part 6 additional class notations chapter 6 cold climate...—sec.5 [10.2.2]: material class...

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DNV GL AS

RULES FOR CLASSIFICATION

Ships

Edition January 2017

Part 6 Additional class notations

Chapter 6 Cold climate

FOREWORD

DNV GL rules for classification contain procedural and technical requirements related to obtainingand retaining a class certificate. The rules represent all requirements adopted by the Society asbasis for classification.

© DNV GL AS January 2017

Any comments may be sent by e-mail to [email protected]

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In this provision "DNV GL" shall mean DNV GL AS, its direct and indirect owners as well as all its affiliates, subsidiaries, directors, officers,employees, agents and any other acting on behalf of DNV GL.

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Rules for classification: Ships — DNVGL-RU-SHIP Pt.6 Ch.6. Edition January 2017 Cold climate

DNV GL AS

CHANGES – CURRENT

This document supersedes the July 2016 edition.Changes in this document are highlighted in red colour. However, if the changes involve a whole chapter,section or sub-section, normally only the title will be in red colour.

Main changes January 2017, entering into force 1 July 2017

• Sec.1 Basic ice strengthening - Ice— Sec.1 [9.2.2]: Correction of error in formula for ice class reinforcement factor CEW. has been made.

• Sec.5 Polar class - PC— Sec.5 [1.3]: Subparagraphs [1.3.2], [1.3.3] and [1.3.4] have been added to be aligned with IACS UR I1.— Sec.5 [4.1.5]: Paragraph has been modified to be aligned with IACS UR I2.— Sec.5 [4.1]: Subparagraphs [4.1.6], [4.1.7] and [4.1.8] have been added to be aligned with IACS UR I1.— Sec.5 Table 4: Class factors have been added to be aligned with IACS UR I2.— Sec.5 [4.3.4]: Bow area characteristics for bow forms defined in [4.1.6], have been added to be aligned

with IACS UR I2.— Sec.5 Table 5: Table has been modified to include a row for frames in bottom structures.— Sec.5 [5.3.1]: Clarification of application of patch load on bottom stiffeners has been added to be aligned

with IACS UR I2.— Sec.5 [5.5]: Effective net web area and net elastic section modulus requirements for frames and load

carrying stringers are deleted and direct calculation, as an alternative, has been addressed.— Sec.5 [6.1]: New subparagraph, [6.1.2], has been introduced to exclude which are designed with a

vertical or bulbous bow.— Sec.5 [8.1]: Direct calculation sub-section has been rearranged and modified by adding subparagraphs to

include more clarifications and acceptance criteria.— Sec.5 [10.2.2]: Material class requirements in table 12 have been stepped downtp be aligned with IACS

UR I2.— Sec.5 Table 13: Table for steel grades for inboard framing members attached to weather exposed plating,

have been deleted to be aligned with IACS UR I2.— Sec.5 [10.2]: Paragraph [10.2.5] has been deleted to be aligned with IACS UR I2.

Editorial correctionsIn addition to the above stated changes, editorial corrections may have been made.

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CONTENTS

Changes – current.................................................................................................. 3

Section 1 Basic ice strengthening - Ice................................................................ 101 General.............................................................................................. 10

1.1 Introduction................................................................................... 101.2 Scope............................................................................................ 101.3 Application..................................................................................... 101.4 Class notations............................................................................... 101.5 Definitions......................................................................................11

2 Documentation...................................................................................112.1 Documentation requirements............................................................11

3 Marking and onboard documentation................................................ 113.1 General..........................................................................................11

4 Materials............................................................................................ 124.1 General..........................................................................................12

5 Loading conditions.............................................................................136 Structural requirements for the class notation Ice(C)....................... 13

6.1 General..........................................................................................136.2 Plating........................................................................................... 136.3 Framing......................................................................................... 136.4 Stringers and web frames................................................................136.5 Weld connections............................................................................ 146.6 Rudder and steering arrangement.....................................................146.7 Stem............................................................................................. 14

7 Machinery requirements for class notation Ice(C)............................. 147.1 Output of propulsion machinery........................................................147.2 Design of propeller and propeller shaft.............................................. 147.3 Sea suctions and discharges............................................................ 18

8 Structural requirements for class notation Ice(E)............................. 188.1 General..........................................................................................188.2 Plating........................................................................................... 198.3 Frames.......................................................................................... 198.4 Stem............................................................................................. 19

9 Machinery requirements for class notation Ice(E)............................. 199.1 Propellers.......................................................................................199.2 Propeller shafts, intermediate shafts, thrust shafts.............................. 21

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9.3 Shrunk joints................................................................................. 229.4 Gears............................................................................................ 229.5 Sea chests and discharge valves.......................................................229.6 Steering gear................................................................................. 239.7 Electric propeller drive.....................................................................23

Section 2 Ice strengthening for the Northern Baltic - Ice..................................... 241 General.............................................................................................. 24



3 Marking and onboard documentation................................................ 273.1 General..........................................................................................27

4 Assumptions...................................................................................... 274.1 General..........................................................................................27

5 Materials............................................................................................ 295.1 General..........................................................................................29

6 Loading conditions.............................................................................297 Design loads...................................................................................... 29

7.1 Engine output.................................................................................297.2 Height of the ice load area.............................................................. 337.3 Ice pressure...................................................................................34

8 Shell plating.......................................................................................358.1 Vertical extension of ice strengthening for plating............................... 358.2 Plate thickness in the ice belt...........................................................36

9 Frames............................................................................................... 379.1 Vertical extension of ice framing.......................................................379.2 Transverse frames...........................................................................379.3 Longitudinal frames.........................................................................409.4 Structural details............................................................................ 41

10 Ice stringers.................................................................................... 4110.1 Stringers within the ice belt........................................................... 4110.2 Stringers outside the ice belt..........................................................4210.3 Deck strips...................................................................................42

11 Web frames..................................................................................... 43

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11.1 Design ice load............................................................................. 4311.2 Section modulus and shear area..................................................... 43

12 Bilge keels....................................................................................... 4412.1 Arrangement.................................................................................44

13 Special arrangement and strengthening forward.............................4413.1 Stem, Baltic ice strengthening........................................................ 4413.2 Arrangements for towing................................................................46

14 Special arrangement and strengthening aft.....................................4614.1 Stern........................................................................................... 4614.2 Rudder and steering arrangements..................................................46

15 Propulsion machinery...................................................................... 4715.1 Materials...................................................................................... 4715.2 Design loads for propeller and shafting............................................4715.3 Design loads.................................................................................5215.4 Design loads on propeller blades.....................................................5215.5 Axial design loads for open and ducted propellers............................. 5715.6 Torsional design loads....................................................................5815.7 Blade failure load..........................................................................6115.8 Design principle............................................................................ 6115.9 Propeller blade design................................................................... 6115.10 Propeller bossing and CP mechanism............................................. 6515.11 Propulsion shaft line.................................................................... 6515.12 Design of shaft line components not specifically mentioned inFSICR................................................................................................. 6615.13 Azimuth main propulsors and other thrusters..................................6615.14 Alternative design........................................................................67

16 Miscellaneous machinery requirements........................................... 6716.1 Starting arrangements................................................................... 6716.2 Sea inlet and cooling water systems................................................6816.3 Ballast system.............................................................................. 68

17 Guidelines for strength analysis of the propeller blade using finiteelement method....................................................................................69

Section 3 Operations in cold climate - Winterized................................................ 701 General.............................................................................................. 70


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3 Certification....................................................................................... 763.1 Certification requirements................................................................ 76

4 Design environmental conditions.......................................................764.1 General..........................................................................................76

5 General requirements........................................................................ 775.1 Anti-icing and anti-freezing measures................................................775.2 De-icing measures.......................................................................... 78

6 Requirements to winterization.......................................................... 796.1 Requirements to winterization.......................................................... 79

Section 4 Design ambient temperature - DAT..................................................... 1101 General............................................................................................ 110

1.1 Introduction..................................................................................1101.2 Scope.......................................................................................... 1101.3 Application................................................................................... 1101.4 Class notations............................................................................. 1101.5 Documentation requirements.......................................................... 1101.6 Definitions.................................................................................... 111

2 Material selection............................................................................ 1132.1 Structural categories..................................................................... 1132.2 Selection of steel grades................................................................115

Section 5 Polar class - PC................................................................................... 1171 General............................................................................................ 117

1.1 Introduction..................................................................................1171.2 Scope.......................................................................................... 1171.3 Application................................................................................... 1171.4 Class notations............................................................................. 118

2 Documentation.................................................................................1182.1 Documentation requirements.......................................................... 118

3 Design principles............................................................................. 1193.1 Design temperature for structure and equipment.............................. 1193.2 Hull areas.................................................................................... 1203.3 System design.............................................................................. 120

4 Design ice loads – hull.................................................................... 1214.1 General........................................................................................1214.2 Glancing impact load characteristics................................................ 122

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4.3 Bow area..................................................................................... 1234.4 Hull areas other than the bow........................................................ 1264.5 Design load patch......................................................................... 1274.6 Pressure within the design load patch..............................................1274.7 Hull area factors........................................................................... 1274.8 Ice compression load amidships......................................................130

5 Local strength requirements............................................................1315.1 Shell plate requirements................................................................ 1315.2 Framing general............................................................................1325.3 Framing – transversely framed side structures and bottom structures...1355.4 Framing – longitudinal local frames in side structure..........................1365.5 Framing – web frames and load carrying stringers.............................1375.6 Framing – structural stability..........................................................1385.7 Plated structures...........................................................................1395.8 Stem and stern frames..................................................................1405.9 End connections for framing members............................................. 140

6 Longitudinal strength.......................................................................1426.1 Application................................................................................... 1426.2 Design vertical ice force at the bow................................................ 1426.3 Design vertical shear force.............................................................1436.4 Design vertical ice bending moment................................................ 1446.5 Longitudinal strength criteria.......................................................... 145

7 Appendages..................................................................................... 1467.1 General........................................................................................1467.2 Rudders....................................................................................... 1467.3 Ice forces on rudder......................................................................1467.4 Rudder scantlings..........................................................................1477.5 Ice loads on propeller nozzles........................................................ 1487.6 Propeller nozzle scantlings............................................................. 1487.7 Podded propulsors and azimuth thrusters.........................................148

8 Direct calculations........................................................................... 1498.1 General........................................................................................149

9 Welding............................................................................................1499.1 General........................................................................................1499.2 Minimum weld requirements...........................................................150

10 Materials and corrosion protection................................................ 15010.1 Corrosion/abrasion additions and steel renewal............................... 15010.2 Hull materials............................................................................. 15110.3 Materials for machinery components exposed to sea water............... 153

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10.4 Materials for machinery components exposed to sea watertemperatures..................................................................................... 15310.5 Materials for machinery components exposed to low air temperature.. 153

11 Ice interaction loads – machinery................................................. 15311.1 Propeller ice interaction................................................................15311.2 Ice class factors..........................................................................15411.3 Design ice loads for open propeller................................................15411.4 Design ice loads for ducted propeller............................................. 15811.5 Propeller blade loads and stresses for fatigue analysis......................16111.6 Design ice loads for propulsion line............................................... 16111.7 Machinery fastening loading conditions...........................................165

12 Design – machinery....................................................................... 16612.1 Design principles......................................................................... 16612.2 Propeller blade design..................................................................16912.3 Fatigue design of propeller blades................................................. 16912.4 Blade flange, bolts and propeller hub and CP Mechanism.................. 17012.5 Propulsion line components.......................................................... 17112.6 Azimuth main propulsion..............................................................17712.7 Steering system.......................................................................... 17812.8 Prime movers............................................................................. 17912.9 Auxiliary systems........................................................................ 17912.10 Sea inlets, cooling water systems and ballast tanks........................17912.11 Ballast tanks............................................................................. 18012.12 Ventilation systems....................................................................18012.13 Alternative design......................................................................180

13 Stability and watertight integrity...................................................18013.1 General...................................................................................... 18013.2 Intact stability.............................................................................18013.3 Requirements to watertight integrity..............................................181

Appendix A Guidelines for strength analysis of the propeller blade using finiteelement method..................................................................................................182

1 Guidelines for strength analysis of the propeller blade using finiteelement method..................................................................................182

1.1 Requirements for finite element model............................................ 1821.2 Good engineering practice for finite element analysis.........................1821.3 Boundary conditions...................................................................... 1831.4 Applied pressure loads...................................................................183

Changes – historic.............................................................................................. 186

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SECTION 1 BASIC ICE STRENGTHENING - ICE

1 General

1.1 IntroductionThe additional class notation Ice establishes requirements for ships intended for service in waters with lightice conditions and light localised drift ice, in river mouths and coastal areas.

1.2 ScopeThe scope for additional class notation Ice specifies requirements for hull strength, machinery systems andequipment, and includes the relevant procedural requirements applicable to ships operating in light ice andlight localised drift ice conditions in river mouths and coastal areas.

1.3 ApplicationThe additional class notation Ice applies to ships built in compliance with the requirements as specified inTable 1 and may be assigned a qualifier related to structural strength and machinery. Ships navigating inwaters with light ice conditions may be assigned the class notation Ice(C), and ships navigating in waterswith light localised drift ice conditions may be assigned the class notation Ice(E). The requirements for classnotation Ice(E) are intended for light localised drift ice in mouths of river and coastal areas.

1.4 Class notationsShips built in compliance with the requirements as specified in Table 1 will be assigned the additional notationrelated to structural strength and integrity as follows:

Table 1 Additional class notation related to cold climate

Class notation Qualifier Purpose Application

C Ships intended for navigationin light ice conditions

Ice

Mandatory:

No

Design requirements:

[6] to [9]

FiS requirements:

Pt.7 Ch.1 Sec.2, Pt.7 Ch.1Sec.3 and Pt.7 Ch.1 Sec.4

E Ships intended for navigationin light localised drift ice

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1.5 DefinitionsTable 2 Definitions of terms

Term Definition

the upper ice water line(UIWL)

is the envelope of the highest points of the waterline at which the ship is intended to operatein ice irrespective of water salinity. The line may be a broken line.

the lower ice water line(LIWL)

is the envelope of the lowest points of the waterline at which the ship is intended to operatein ice. The line may be a broken line.

1.5.1 SymbolsFor symbols not defined in this section, see Pt.3 Ch.1 Sec.4.s1 = stiffener spacing measured along the plating between ordinary and/or intermediate stiffeners, in m.

2 Documentation

2.1 Documentation requirementsDetails related to design, arrangement and strength are in general to be included in the plans specified forthe main class.

3 Marking and onboard documentation

3.1 General

3.1.1 The maximum and minimum ice class draughts fore, amidships and aft shall be indicated in theappendix to the classification certificate.

3.1.2 If the summer load line in fresh water is anywhere located at a higher level than the UIWL, the shipsides shall be provided with a warning triangle and with ice class draught marks at the maximum permissibleamidships draught, see Figure 1, and the maximum permissible draught amidships shall be explicitlyindicated in the appendix to the classification certificate.

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Ice

Ice

Figure 1 Ice class draught marking

3.1.3 Marking requirements

1) The ice class draught marking “Ice” shall indicate the maximum ice class draught.2) The upper edge of the warning triangle shall be located vertically above the “Ice” mark, at the height

1000 mm above summer fresh water load line, but not higher than the deck line. The sides of thetriangle shall be 300 mm in length.

3) The ice class draught mark shall be located 540 mm abaft the centre of the load line ring or 540 mmabaft the vertical line of the timber load line mark, if applicable.

4) The ice marks and letters shall be cut out of 5 to 8 mm plate and then welded to the ship's side ormarking shall be indicated by weld seam directly on the ship side. The marks and letters shall be paintedin a red or yellow reflecting colour in order to make the marks and figures plainly visible even in iceconditions.

5) The dimensions of all letters shall be the same as those used in the load line mark.6) For ships not having load line markings, the warning triangle and ice draught mark shall be vertically

aligned with the draught mark. The warning triangle shall be placed 1000 mm above the draught mark,but in no case above the deck line.

4 Materials

4.1 General

4.1.1 For minimum material grade for ice strengthening ships, see Pt.3 Ch.3 Sec.1 Table 7. Shell strakes inway of ice strengthening area for plates shall be minimum grade B/AH.

4.1.2 The use of materials other than those specified in Pt.3 Ch.3 Sec.1 shall be agreed with the Society.

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5 Loading conditionsAll design loading conditions in ice, including trim, shall be within the draught envelope limited by the UIWLand LIWL. The lower ice waterline should further be determined with due regard to the ship's ice-goingcapability in the ballast loading conditions, e.g. propeller submergence. See also Sec.2 [7].(IACS UR I 1.3)

6 Structural requirements for the class notation Ice(C)

6.1 General

6.1.1 The requirements for the bow ice belt region, as defined in Sec.2 Figure 2, for sub-section elements[6.2] to [6.7], shall be in accordance with Sec.2 as follows:

— In Sec.2 Table 5, the value of ho and h shall be as given for Ice(1C).— The ice pressure shall be determined in accordance with Sec.2 [7.3], where the factor c1, as given in

Sec.2 Table 11, is taken as being equal to 0.55— Vertical extension of the ice belt plating and framing shall be:

Plating: 0.4 m above UIWL and 0.5 m below LIWLFraming: 0.62 m above UIWL and 1.0 m below LIWL.

6.2 Plating

6.2.1 In the bow ice belt region as defined in [6.1.1], the shell plate thickness shall be as given in Sec.2 [8].

6.3 Framing

6.3.1 In the bow ice belt region as defined in [6.1.1], the frames shall be as given in Sec.2 [9.1] to Sec.2[9.3].In addition, the following shall apply:

1) Frames shall be effectively attached to all supporting structures. Transverse and longitudinal framescrossing support structures shall be connected to these with lugs. Alternatively, top stiffener incombination with lug may be used. The upper end of intermediate frames may be sniped at a stringer ordeck provided the ice belt covers not more than 1/3 of the span.

2) Frames where the angle between the web and the shell is less than 75 degrees shall be supportedagainst tripping by brackets, intercostals, stringers or similar at a distance preferably not exceeding 2.5m.Transverse frames perpendicular to shell which are of unsymmetrical profiles shall have trippingpreventions if the span is exceeding 4.0 m.

3) The web thickness of the frames shall be at least one half of the thickness of the shell plating. Wherethere is a deck, tank top, bulkhead, web frame or stringer in lieu of a frame, at least one half of thethickness of shell plating shall be kept to a depth of not less than 0.0025 L, minimum 0.2 m.

6.4 Stringers and web frames

6.4.1 Stringers situated inside and outside the ice belt shall be as given in Sec.2 [10.1] to Sec.2 [10.2]. Webframes shall be as given in Sec.2 [11].

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6.5 Weld connections

6.5.1 Weld connections to shell in fore peak shall be double continuous.

6.6 Rudder and steering arrangement

6.6.1 The rudder and steering arrangement shall comply with Sec.2 [14.2], given that the maximum servicespeed of the ship is not taken less than 14 knots.

6.7 Stem

6.7.1 The plate thickness of a shaped plate stem and any part of the bow which forms an angle of 60degrees or more to the centreline in a horizontal plane shall comply with Sec.2 [13.1.2] up to 600 mm aboveUIWL.

7 Machinery requirements for class notation Ice(C)

7.1 Output of propulsion machinery

7.1.1 The maximum continuous output, in kW, is generally not to be less than:ps = 0.73 L B

For ships with a bow specially designed for navigation in ice, a reduced output may be accepted. In any case,the output, in kW, shall not be less than:

ps = 0.59 L B

7.1.2 If the ship is fitted with a controllable pitch propeller, the output may be reduced by 25%.

7.2 Design of propeller and propeller shaft

7.2.1 The formula for scantlings is based on the following loads:

To = mean torque of propulsion engine at maximum continuous rating in Nm.

If multi-engine plant, To is the mean torque in an actual branch or after a common point. To is alwaysreferred to engine r.p.m.

Tho = mean propeller thrust in N at maximum continuous speedR = as given in [7.2.2]Tice = ice torque in Nm, referred to propeller r.p.m.

= 35 200 R2 for open propellers= 35 200 R2 (0.9 − 0.0622 R-0.5) for ducted propellers.

Skewed propellers will be especially considered with respect to the risk of blade bending at outer radii if fskexceeds 1.15 (see [7.2.4]).

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7.2.2 The particulars governing the requirements for propeller scantlings are:

R = propeller radius, in mHr = pitch in m at radius in questionθ = rake in degrees at blade tip (backward rake positive)Z = number of bladest = blade gross thickness, in mm, at cylindrical section considered:

t0.25 = t at 0.25 Rt0.35 = t at 0.35 Rt0.6 = t at 0.6 R

cr = blade width, in m, at cylindrical section considered:

c0.25 = cr at 0.25 R

c0.35 = cr at 0.35 R

c0.6 = cr at 0.6 R

e = distance between skew line and generatrix, in m, at cylindrical section considered, positive whenskew line is forward of generatrix:

e0.6 = e at 0.6 Re1.0 = e at 1.0 R

u = gear ratio:

u = 1, if the shafting system is directly coupled to engine

no = propeller speed at maximum continuous output, for which the machinery shall be approved, inrevolutions per minute.

7.2.3 Propellers and propeller parts (defined in Pt.4 Ch.5 Sec.1 [1.3]) shall be of steel or bronze as specifiedin Pt.2 Ch.2. Nodular cast iron of grade VL 1 and VL 2 may be used for relevant parts in CP-mechanism.Other type of nodular cast iron with elongation ≥ 12% may be accepted upon special consideration for samepurposes.

7.2.4 The blade gross thickness, in mm, of the cylindrical sections at 0.25 R (fixed pitch propellers only) andat 0.35 R shall not be less than:

The gross thickness, in mm, at 0.6 R shall not be less than:

where:

U1 and U2 = material constants shall be taken as given in Pt.4 Ch.5 Sec.1 Table 2.

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For fixed blade propellers:

For controllable pitch propellers:

K4 = kiZTice sinαC1, C2, C3, C4 = as given in Table 3A = q0 + q1d + q2d

2 + q3d3

q0, q1, q2, q3 = as given in Table 4

d = for fixed blade propellers

d = for controllable pitch propellers

ki = 96 at 0.25 R= 92 at 0.35 R

KMat = 1.0 for stainless steel propellers= 0.8 for other materials

sinα = at 0.25 R

= at 0.35 R

K1 as given above is only valid for propulsion by diesel engines (by about zero speed, it is assumed 85%thrust and 75% torque for fixed pitch propellers and 125% thrust and 100% torque for controllable pitchpropellers).

For turbine, diesel-electric or similar propulsion machinery K1 will be considered in each particular case.Guidance note:K1 may be calculated for other than diesel driven propellers by replacing the constants 0.85 by 1.1 and 0.75 by 1.0 for FP providedthat maximum torque of the driving engine is limited to 100% of the nominal torque. If driving torque exceeds 100%, the torqueconstant 1.0 shall be multiplied by the ratio Tmax/To and corresponding thrust value (Tho times constant) calculated based on the

actual maximum torque.

---e-n-d---o-f---g-u-i-d-a-n-c-e---n-o-t-e---

The thickness of other sections is governed by a smooth curve connecting the above section thicknesses.

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Table 3 Values of C1, C2, C3, C4

r 0.25 R 0.35 R 0.6 R

C1 0.278 0.258 0.150

C2 0.026 0.025 0.020

C3 0.055 0.049 0.034

C4 1.38 1.48 1.69

Table 4 Values of q0, q1, q2, q3

R q0 q1 q2 q3

0.25 RA1

A2

8.30

63.80

0.370

-4.500

-0.340

-0.640

0.030

0.0845

0.35 RA1

A2

9.55

57.30

-0.015

-7.470

-0.339

-0.069

0.0322

0.0472

0.6 RA1

A2

14.60

52.90

-1.720

-10.300

-0.103

0.667

0.0203

0.0

7.2.5 If found necessary by the torsional vibration calculations, minor deviations from the dimensions givenin [7.2.4] may be approved upon special consideration.

7.2.6 The gross section modulus of the blade bolt connection, in cm3, referred to an axis tangentially to thebolt pitch diameter, shall not be less than:

where:

σb = tensile strength of propeller blade material, in N/mm2

σy = yield stress of bolt material, in N/mm2.

The propeller blade foot shall have a strength (including stress concentration) not less than that of the bolts.

7.2.7 Fitting of the propeller to the shaft is given in Pt.4 Ch.4 Sec.1 as follows:

— flanged connection in [6.3]— keyless cone connection in [6.4]— keyed cone connection in [6.5].

Considering 0°C seawater temperature.If the propeller is bolted to the propeller shaft, the bolt connection shall have at least the same bendingstrength as the propeller shaft.The strength of the propeller shaft flange (including stress concentration) shall be at least the same as thestrength of the bolts.

7.2.8 The propeller shaft diameter need not exceed 1.05 times the rule diameter given for main class,irrespective of the dimension required below.

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The diameter of the propeller shaft at the aft bearing, in mm, shall not be less than:

where:

σb = tensile strength of propeller blade material, in N/mm2

σy = yield strength of propeller shaft material, in N/mm2

c0.35 = as defined in [7.2.2]t0.35 = as defined in [7.2.2].

Between the aft and second aft bearing, the shaft may be evenly tapered to 1.22 times the diameter of theintermediate shaft, as required for the main class.

Forward of the after peak bulkhead, the shaft may be evenly tapered down to 1.05 times the rule diameter ofintermediate shaft, but not less than the actual diameter of the intermediate shaft.

7.3 Sea suctions and discharges

7.3.1 The sea cooling water inlet and discharge for main and auxiliary engines shall be so arranged so thatblockage of strums and strainers by ice is prevented. In addition to requirements in Pt.4 Ch.1 and Pt.6 therequirements in [7.3.2] and [7.3.3] shall be complied with.

7.3.2 One of the sea cooling water inlet sea chests shall be situated near the centre line of the ship andwell aft. At least one of the sea chests shall be sufficiently high to allow ice to accumulate above the pumpsuctions.

7.3.3 A full capacity discharge branched off from the cooling water overboard discharge line shall beconnected to at least one of the sea inlet chests. At least one of the fire pumps shall be connected to this seachest or to another sea chest with de-icing arrangements.

Guidance note:Heating coils may be installed in the upper part of the sea chest(s). Arrangement using ballast water for cooling purposes isrecommended but will not be accepted as a substitute for sea inlet chest arrangement as described above.


8 Structural requirements for class notation Ice(E)

8.1 General

8.1.1 The requirements for the bow ice belt region, as defined in Sec.2 Figure 2, for sub-section elements[8.2] to [8.4], shall be in accordance with Sec.2 as follows:

— In Sec.2 Table 5, the value of ho and h shall be as given for Ice(1C).— The ice pressure shall be determined in accordance with Sec.2 [7.3], where:

— for determination of k, the machinery output PS need not be taken > 750 kW— the factor c1, as given in Sec.2 Table 11, is taken as being equal to 0.30.

— Vertical extension of the ice belt plating and framing shall be:Plating: 0.4 m above UIWL and 0.5 m below LIW.

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Framing: 0.62 m above UIWL and 1.0 m below LIWL.

8.2 Plating

8.2.1 In the bow ice belt region as defined in [8.1.1], the shell plate thickness shall be as given in Sec.2 [8].

8.3 Frames

8.3.1 In the bow ice belt region as defined in [8.1.1], the frames shall be as given in Sec.2 [9.1] to Sec.2[9.3].

8.3.2 In the bow ice belt region tripping brackets shall be fitted as given in [6.3].

8.4 Stem

8.4.1 The plate thickness of a shaped plate stem and any part of the bow which forms an angle of 60degrees or more to the centreline in a horizontal plane shall comply with Sec.2 [13.1.2] up to 600 mm aboveUIWL.

9 Machinery requirements for class notation Ice(E)

9.1 Propellers9.1.1 GeneralThe propellers of ships with ice class Ice(E) shall be made of the cast copper alloys or cast steel alloysspecified in Pt.4 Ch.5 Sec.1 [2.1].

9.1.2 StrengtheningBlade sections:

tE =

= increased gross thickness of blade section, in mmt = blade section gross thickness fulfilling Pt.4 Ch.5 Sec.1 [2.2]

if CEP ≤ CDyn then tE = t

if CEP > CDyn then tE =

CEP = ice class strengthening factor:

=

f = 0.62 for solid propellers= 0.72 for controllable pitch propellers

In the case of ducted propellers, the values of f may be reduced by 15%.z = number of bladespW = main engine power, in kW

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n2 = propeller shaft speed, in rpmCDyn = dynamic factor:

, for , otherwise 1.0.

σmax/σm = the maximum and mean stress, generally to be taken from a detailed FE calculation.If, in exceptional cases, no such calculation exists, the stress ratio may be calculatedapproximately according to the following formula:

ET =

f2 = 0.4 - 0.6 for single-screw ships, the lower value has to be chosen for stern shapes with a bigpropeller tip clearance and no rudder heel, the larger value to sterns with small clearance andwith rudder heel. Intermediate values are to be selected accordingly

VS = ship speed, in knw = mean wake fractionT = propeller thrust, in N.

Blade tips:

t1.0E =

= increased gross thickness of blade section, in mmt1.0E = strengthened blade tip, in mmD = propeller diameter, in mmCW = material factor, corresponds to σB, see Pt.4 Ch.5 Sec.1 Table 4.

In the case of ducted propellers, the thickness of blade tips may be reduced by 15%.

Leading and trailing edges:

The gross thickness of the leading and trailing edges of reversible propellers and the thickness of the leadingedge of controllable pitch propellers shall be equal for ice class Ice(E) to at least 35% of the blade tipt1.0E when measured at a distance of 1.25 · t1.0E from the edge of the blade. For ducted propellers, thestrengthening at the leading and trailing edges has to be based on the non-reduced tip gross thicknessaccording to formula for t1.0E above.

Blade wear:

If the actual gross thickness in service is below 50% at the blade tip or 90% at other radii of the valuesobtained from [9.1.2], respective counter measures have to be taken. Ice strengthening factors according to[9.1.2] will not be influenced by an additional allowance for abrasion.

Guidance note:If the propeller is subjected to substantial wear, e.g. abrasion in tidal flats or in case of dredgers, a wear allowance should beadded to the blade thickness determined in order to achieve an adequate service time with respect to blade wear.


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Propeller mounting:

Where the propeller is mounted on the propeller shaft by the oil injection method, the necessary contactpressure PE, in N/mm2, in the area of the mean taper diameter shall be determined as in [9.3].

In the case of flanged propellers, the required diameter dsE of the alignment pin shall be determined byapplying the following formula:

where:

dsE = reinforced root diameter of alignment pin, in mmds = diameter of alignment pin for attaching the propeller, in mm, in accordance with Pt.4 Ch.4 Sec.1

[2.3.4]CEW = ice class reinforcement factor in accordance with formula [9.2.2].

9.2 Propeller shafts, intermediate shafts, thrust shafts9.2.1 GeneralThe necessary propeller shaft reinforcements in accordance with formula given in [9.2.2], in conjunction withthe formulae and factors specified in Pt.4 Ch.4 Sec.1 [2.2], apply to the area of the aft stern tube bearingor shaft bracket bearing as far as the forward load-bearing edge of the propeller or of the aft propeller shaftcoupling flange subject to a minimum area of 2.5 · d.

9.2.2 Reinforcements

where:

dE = increased diameter of propeller shaft, in mmd = shaft diameter, in mm, according to Pt.4 Ch.4 Sec.1 [2.2]CEW = ice class reinforcement factor:

=

pW, n2 = see [9.1.2]c = 0.7 for shrink fits in gears

= 0.71 for the propeller shafts of fixed-pitch propellers= 0.78 for the propeller shafts of controllable pitch propellers.

In case of ducted propellers, the values of c can be reduced by 10%.

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9.3 Shrunk joints9.3.1 Normal operationWhen designing shrink fits in the shafting system and in gearboxes, the necessary pressure per unit area PE,in N/mm2, shall be calculated in accordance with the following formula:

where:

f =

A = effective area of a shrink fit, in mm2

CA = coefficient for shrink joints:= 1.0 for geared diesel engine and turbine plants as well as for electric motor drives= 1.2 for diesel engine drives

ce = Ice strengthening factor:

=

C = conicity of shaft ends:= difference in diameter/length of taper

Q = peripheral force at mean taper diameter, in NS = safety margin against propeller slipping on cone ≥ 2.8

θ = half-conicity = .

T has to be introduced as positive value if the propeller thrust increases the surface pressure at the taper.Change of direction of the axial force shall be neglected as far as performance and thrust are essentially less.T has to be introduced as negative value if the axial force reduces the surface pressure at the taper, e.g. fortractor propellers.

9.3.2 Operation at a resonanceFor direct coupled propulsion plants with a barred speed range it has to be confirmed by separate calculationthat the vibratory torque in the main resonance is transmitted safety. For this proof the safety againstslipping for the transmission of torque shall be at least S = 2.0, the coefficient cA may be set to 1.0. For thisadditional proof the respective influence of the thrust shall be disregarded.CEW to be calculated according to [9.2.2], the higher value of the connected shaft ends has to be taken forthe coupling

9.4 GearsGears in the main propulsion plant of ships with ice class Ice(E) shall not be strengthened.

9.5 Sea chests and discharge valvesSea chests and discharge valves shall be designed in accordance with Pt.4 Ch.6.

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9.6 Steering gearThe dimensional design of steering gear components shall take account of the rudder stock diameterspecified in Pt.3 Ch.14 Sec.1 [7].

9.7 Electric propeller driveFor ships with electrical propeller drive see the rules for electrical propulsion Pt.4 Ch.8 Sec.5 and Pt.4 Ch.8Sec.12.

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SECTION 2 ICE STRENGTHENING FOR THE NORTHERN BALTIC - ICE

1 General

1.1 IntroductionThe additional class notation Ice establishes requirements for ships intended for service in the northernBaltic in winter or areas with similar ice conditions.

1.2 ScopeThe scope for additional class notation Ice specifies requirements for hull strength, machinery systems andequipment and the relevant procedural requirements applicable to ships operating in northern Baltic iceconditions. A series of qualifiers is available for this notation; related to ships intended for navigation in ice-infested waters, in varying degrees of ice thickness. High powered ships employed as regular traffic, in heavyBaltic ice, may be assigned a specific qualifier associated with their trade.

1.3 ApplicationThe additional class notation Ice applies to ships built in compliance with the requirements of this sectionand may be assigned one of the following class notations: Ice(1A*), Ice(1A), Ice(1B) or Ice(1C). Shipsassigned class notation Ice(1A*) may be assigned the class notation Ice(1A*F). The additional ice classIce(1A*F) is recommended for ships with relatively high engine power designed for regular traffic in thenorthern Baltic and other relevant areas, normally operating according to rather fixed timetables irrespectiveof ice conditions and to a certain degree independent of ice breaker assistance.

1.4 Class notationsShips built in compliance with the requirements as specified in Table 1 will be assigned the additional notationas follows:



1A*FHigh powered ships forregular traffic in heavy Balticice.

Ships constructed according to Baltic ice rules.Ice thickness 1.0 m.

1A* Ships intended for navigationin ice-infested waters.

Constructed according to Baltic ice rules. Icethickness 1.0 m.

1A Ships intended for navigationin ice-infested waters.


1B Ships intended for navigationin ice-infested waters.


Ice

Mandatory:

No


[6] to [16]

FiS requirements:

Pt.7 Ch.1 Sec.2, Pt.7 Ch.1Sec.3 and Pt.7 Ch.1 Sec.4 1C Ships intended for navigation

in ice-infested waters.Constructed according to Baltic ice rules. Icethickness 0.4 m.

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1.4.1 The DNV GL ice classes are accepted as equivalent to the Finnish-Swedish ice classes.

Table 2 Equivalence between DNV GL Ice class notation and the Finnish-Swedish ice classes

Ice class notation Equivalent Finnish-Swedish ice class

Ice(1A*) 1A Super

Ice(1A) 1A

Ice(1B) 1B

Ice(1C) 1C

1.5 Definitions1.5.1 General definitions

Table 3 Definitions of terms

Term Definition

extent of ice strengthening is determined from the upper ice water line (UIWL) to the lower ice water line(LIWL), which defines the extreme draughtsFor operation in Baltic, the upper ice waterline (UIWL) is in general the same as thefresh water summer load line. See also Sec.1 [1.5].

bow region from the stem to a line parallel to and 0.04 L aft of the forward borderline of thepart of the hull where the waterlines run parallel to the centre lineFor ice classes Ice(1A*F), Ice(1A*) and Ice(1A) the overlap of the borderlineneed not exceed 6 m, for ice classes Ice(1B), Ice(1C) and Ice(E) this overlapneed not exceed 5 m. See Figure 1.

midbody region from the aft boundary of the bow region to a line parallel to and 0.04 L aft of the aftborderline of the part of the hull where the waterlines run parallel to the centre line.For ice classes Ice(1A*F), Ice(1A*) and Ice(1A) the overlap of the borderlineneed not exceed 6 m, for ice classes Ice(1B) and Ice(1C) this overlap need notexceed 5 m. See Figure 1.

ice belt regions

stern region from the aft boundary of the midbody region to the sternSee Figure 1.

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Figure 1 Ice belt regions

The upper ice water line (UIWL) and the lower ice water line (LIWL) are defined in Sec.1 [1.5].

1.5.2 Definition of forward draught during transit in ballast conditionThe minimum forward draught, in m, shall be at least:

(2 + 0.00025 Δf) ho

but need not exceed 4 ho where:

Δf = displacement of the ship, in tonnes, on the maximum ice class draught according to [1.5.3]ho = ice thickness according to Table 10.

1.5.3 SymbolsFor symbols not defined in this section, refer to Pt.3 Ch.1 Sec.4.

2 Documentation

2.1 Documentation requirements2.1.1 GeneralFor general requirements to documentation, including definition of the Info codes, see Pt.1 Ch.3 Sec.2.For a full definition of the documentation types, see Pt.1 Ch.3 Sec.3.Documentation shall be submitted as required by Table 4.

Table 4 Document requirements

Object Documentation type Additional description Info

Technicalinformation Z100 – Specification Displacement, machinery type, propulsion power. FI

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Z265 – Calculationreport

Minimum required propulsion power, Pmin,see[7.1]. Hullparticulars defined in [7.1.3]. FI

C040 – Design analysisApplicable if a first blade order torsional resonance is withinoperational speed range +/- 20%. Torsional vibration analysis ofice torque response.

APPropulsionand steeringarrangement

C040 – Design analysis Applicable for alternative designs, not applying loads defined inthe rules. Comprehensive design analysis of entire system. AP

Propellerarrangement C040 – Design analysis Finite element analysis of blade stresses introduced by ice loads. AP

AP = For approval; FI = For information

3 Marking and onboard documentation

3.1 GeneralFor marking and on board documentation see Sec.1 [3].

4 Assumptions

4.1 General

4.1.1 The method for determining the hull scantlings, engine output and other properties are based oncertain assumptions concerning the nature of the ice load on the structure and operation of the ship asdescribed in the Finnish-Swedish ice class rules. These assumptions rest on full scale observations made inthe northern Baltic.

Table 5 Operation of the ship - design basis

Ice(1A*) normally capable of navigating in difficult ice conditions without the assistance of icebreakers

Ice(1A) capable of navigating in difficult ice conditions, with the assistance of icebreakers when necessary

Ice(1B) capable of navigating in moderate ice conditions, with the assistance of icebreakers when necessary

Ice(1C) capable of navigating in light ice conditions, with the assistance of icebreakers when necessary

Guidance note:For background documentation of this section, reference is made to Finnish Transport Safety Agency (TraFi) homepage: http://www.trafi.fi/en/maritime/ice_classes_of_ships:Finnish-Swedish Ice Class RulesGuidelines for the application of the Finnish-Swedish ice class rules (hereafter called TraFi Guidelines)


4.1.2 Assistance from icebreakers is normally assumed when navigating in ice bound waters.

4.1.3 The formula given for plating, stiffeners and girders is based on special investigations as to thedistribution of ice loads from plating to stiffeners and girders as well as redistribution of loads on stiffenersand girders. Special values have been given for distribution factors and certain assumptions have been maderegarding boundary conditions.

http://www.trafi.fi/en/maritime/ice_classes_of_ships

http://www.trafi.fi/en/maritime/ice_classes_of_ships

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4.1.4 For the formulae and values given in this section for the determination of the hull scantlings moresophisticated methods may be substituted subject to special approval. However, direct analysis is not to beutilized as an alternative to the analytical procedures prescribed by explicit requirements in [8], [9] and [10](plates, frames and stringers), unless these are invalid or inapplicable for a given structural arrangement ordetail.Direct analyses shall be carried out using the load patch defined in [7] (P, h and ℓa). The pressure to be usedis 1.8·P where P is determined according to [7.3.1]. The load patch shall be applied at locations where thecapacity of the structure under the combined effects of bending and shear are minimized. In particular, thestructure shall be checked with load centred at the UIWL, 0.5·ho below the LIWL, and positioned severalvertical locations in between. Several horizontal locations shall also be checked, especially the locationscentred at the mid-span or -spacing. Further, if the load length ℓa cannot be determined directly from thearrangement of the structure, several values of ℓa shall be checked using corresponding values for ca.Acceptance criteria for designs are that the combined stresses from bending and shear, using the von Misesyield criterion, are lower than the yield point ReH. If the structure is analysed by the use of beam models,the allowable bending and shear stress is not to be larger than 0.9·ReH and 0.9·τeH respectively, where τeH =ReH/√3.

4.1.5 If scantlings derived from these regulations are less than those required for a non-ice-strengthenedship, the latter shall be used.

4.1.6 The frame spacings and spans defined in the following text are in general to be as given in Pt.3 Ch.3Sec.6 and normally assumed to be measured along the plate and perpendicular to the axis of the stiffener forplates, along the flange for members with a flange, and along the free edge for flat bar stiffeners. For curvedmembers the span (or spacing) is defined as the chord length between span (or spacing) points. The spanpoints are defined by the intersection between the flange or upper edge of the member and the supportingstructural element (stringer, web frame, deck or bulkhead). Figure 2 illustrates the determination of span andspacing for curved members.

Figure 2 Definition of the frame span (left) and frame spacing (right) for curved members

4.1.7 The effective breadth of the attached plate to be used for calculating the combined section modulus ofthe stiffener, stringer and web frame and attached plate shall be taken as given in Pt.3 Ch.3 Sec.6 [1.3].

4.1.8 The requirements for the section modulus and shear area of the frames, stringers and web frames in[9], [10] and [11] with respect to the effective member cross section, where the member is not normal tothe plating, the section properties shall be calculated in accordance with Pt.3 Ch.3 Sec.6 [1.4].

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5 Materials

5.1 GeneralFor minimum material grade for ice strengthening ships see Sec.1 [4].

6 Loading conditionsFor design loading conditions in ice see Sec.1 [5].

7 Design loads

7.1 Engine output7.1.1 Definition of engine outputThe engine output PS is the maximum output the propulsion machinery can continuously deliver to thepropeller(s). If the output of the machinery is restricted by technical means or by any regulations applicableto the ship, PS shall be taken as the restricted output.

7.1.2 Documentation onboardThe restricted engine output in ice shall be given in the appendix to classification certificate.

7.1.3 Required engine output for ice classesDefinitions

The dimensions of the ship and some other parameters are defined below:

LBOW = length of the bow, in m, see Figure 3L PAR = length of the parallel midship body, in m, see Figure 3T = actual ice class draughts of the ship, in m, according to [1.5.3]A wf = area of the waterline of the bow, in m2, see Figure 3α = the angle of the waterline at B/4, in degrees, see Figure 3φ1 = the rake of the stem at the centre line, in degrees, see Figure 3φ2 = the rake of the bow at B/4, in degrees, see Figure 3ψ = flare angle, in degrees, calculated as ψ = arc tan(tan φ/sin α) using angles α and φ at each

location. For subsection [7.1], flare angle is calculated using φ = φ2

DP = diameter of the propeller or outer diameter of nozzle for the nozzle propeller, maximum 1.2times propeller diameter, in m

HM = thickness of the brash ice in mid channel, in mHF = thickness of the brash ice layer displaced by the bow, in mRCH = resistance, in N, of the ship in a channel with brash ice and a consolidated layer (see formula in

[7.1.4])Ke = factor depending on no. of propellers, CPP (or similar), fixed pitch type (see Table 6)Pmin = minimum required engine output, in kWC = empirical coefficients (misc. sub index)f = empirical factors (misc. sub index)g = empirical factors (misc. sub index)

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L = length of the ship between the perpendiculars, in mB = maximum breadth of ship, in m.

Range of validity

The range of validity of the formulae for powering requirements in [7.1.4] is presented in Table 15. Whencalculating the parameter DP/T, T shall be measured at UIWL.

Table 6 Parameter validity range

Parameter Minimum Maximum

α [degrees] 15 55

φ1 [degrees] 25 90

φ2 [degrees] 10 90

L [m] 65.0 250.0

B [m] 11.0 40.0

T [m] 4.0 15.0

LBOW/L 0.15 0.40

LPAR/L 0.25 0.75

DP /T 0.45 0.75

Awf /(L×B) 0.09 0.27

If the ship’s parameter values are beyond the ranges defined in Table 6, other methods for determining RCHmay alternatively be used as defined in [7.1.5].

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Figure 3 Definitions

7.1.4 The engine output requirement shall be calculated for:

— upper ice waterlines (UIWL) and— lower ice waterlines (LIWL),

as defined in Sec.1 [2].

In the calculations the ship's parameters which depend on the draught shall be determined at the appropriatedraught, but L and B shall be determined only at the UIWL. The engine output shall not be less than thegreater of these two outputs.

The engine output Pmin, in kW, shall not be less than that determined by the formulae and in no case lessthan given in Table 8:

Guidance note:New ships – see [1.4.1] guidance note.For existing Ice(1A) and Ice(1A*) ships see Pt.7 Ch.2 Sec.2 [1].


Table 7 Value of factor Ke for conventional propulsion systems*)

Propeller type or machinery

Numbers of propellers Controllable pitch propeller or electricor hydraulic propulsion machinery Fixed pitch propeller

1 propeller 2.03 2.26

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Propeller type or machinery

Numbers of propellers Controllable pitch propeller or electricor hydraulic propulsion machinery Fixed pitch propeller

2 propellers 1.44 1.6

3 propellers 1.18 1.31

*) For advanced systems see [7.1.5].

Table 8 Minimum engine output Pmin

Ice(1A), Ice(1B) and Ice(1C) 1000 kW

Ice(1A*) 2800 kW

RCH is the resistance, in N, of the ship in a channel with brash ice and a consolidated layer:

where:

Cμ = 0.15 cos φ2 + sin ψ sin αCμ ≥ 0.45 (minimum value)

Cψ = 0.047 ψ − 2.115 and 0 if ψ ≤ 45°HF = 0.26 + (HMB)0.5

HM = 1.0 for Ice(1A) and Ice(1A*)= 0.8 for Ice(1B)= 0.6 for Ice(1C).

C1 and C2 take into account a consolidated upper layer of the brash ice and can be taken as zero for ice classIce(1A), Ice(1B) and Ice(1C).

For ice class Ice(1A*):

For a ship with a bulbous bow, φ1 shall be taken as 90°.

f1 = 23 N/m2

f2 = 45.8 N/mf3 = 14.7 N/mf4 = 29 N/m2

g1 = 1 530 Ng2 = 170 N/m

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g3 = 400 N/m1.5

C3 = 845 kg/m2s2

C4 = 42 kg/m2s2

C5 = 825 kg/s2

shall not be taken less than 5 and not more than 20.

7.1.5 Other methods of determining Ke or RCHFor an individual ship, in lieu of the Ke or RCH values defined in Table 7 and [7.1.4], the use of Ke or RCHvalues based on more exact calculations or values based on model tests may be approved. Such approvalwill be given on the understanding that it can be revoked if experience of the ship’s performance in practicemotivates this.

Guidance note:For ships intended for trading in Finnish waters and having the propulsion power determined by model tests or by means otherthan the rule formula, additional approval by Finnish or Swedish authorities is necessary.


The design requirement for ice classes shall be a minimum speed of 5 knots in the following brash icechannels (see Table 9):

Table 9 Values of HM

Ice class HM

Ice(1A*) 1.0 m and a 0.1 m thick consolidated layer of ice

Ice(1A) 1.0 m

Ice(1B) 0.8 m

Ice(1C) 0.6 m

7.2 Height of the ice load area

7.2.1 An ice strengthened ship is assumed to operate in open sea conditions corresponding to a level icethickness not exceeding ho. The design the ice height (h) of the area actually under ice pressure at anyparticular point of time is, however, assumed to be only a fraction of the ice thickness. The values for ho andh are given in the following table.

Table 10 Values of ho and h

Ice class ho (m) h (m)

Ice(1A*)

Ice(1A)

Ice(1B)

Ice(1C)

1.0

0.8

0.6

0.4

0.35

0.30

0.25

0.22

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7.3 Ice pressure

7.3.1 The design ice pressure (based on a nominal ice pressure of 5600 kN/m2), in kN/m2, is determined bythe formula:

where:

cd = a factor which takes account of the influence of the size and engine output of the ship. This factor istaken as maximum cd = 1. It is calculated by the formula:

a1 and b1 are given in Table 11.

Table 11 Values of a1 and b1

Region

Bow Midbody and stern

k1 ≤ 12 k1 > 12 k1 ≤ 12 k1 > 12

a1 30 6 8 2

b1 230 518 214 286

Δf = displacement, in tonnes, as defined in [1.5.4]PS = machinery output, in kW. PS ≥ Pmin, where Pmin is defined in [7.1.4]c1 = a factor which takes account of the probability that the design ice pressure occurs in a certain

region of the hull for the ice class in question.

The value of c1 is given in Table 12:

Table 12 Values of c1

RegionIce class

Bow Midbody Stern

Ice(1A*) 1.0 1.0 0.75

Ice(1A) 1.0 0.85 0.65

Ice(1B) 1.0 0.70 0.45

Ice(1C) 1.0 0.50 0.25

For ice class Ice(1A*F) an additional lower bow ice belt (see [8.1.2]) is defined with factor c1 = 0.20.

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ca = a factor which takes account of the probability that the full length of the area under considerationwill be under pressure at the same time. It is calculated by the formula:

, maximum 1.0, minimum 0.35, ℓ0 = 0.6 m

ℓa shall be taken as given in Table 13.

Table 13 Values of ℓa

Structure Type of framing ℓa

transverse frame spacingShell

longitudinal 1.7 × frame spacing

transverse frame spacingFrames

longitudinal span of frame

Ice stringer span of stringer

Web frame 2 × web frame spacing

8 Shell plating

8.1 Vertical extension of ice strengthening for plating

8.1.1 The vertical extension of the ice belt (see Figure 1) shall not be less than given in Table 14.

Table 14 Vertical extension of ice belt

Ice class Region Above UIWL (m) Below LIWL (m)

Bow

Midbody1.20

Ice(1A*)

Stern

0.60

1.0

Bow 0.90

MidbodyIce(1A)

Stern

0.500.75

Bow 0.70

MidbodyIce(1B) and Ice(1C)

Stern

0.400.60

8.1.2 In addition the following areas shall be strengthened:Fore foot: For ice class Ice(1A*) and Ice(1A*F), the shell plating below the ice belt from the stem to aposition five main frame spaces abaft the point where the bow profile departs from the keel line shall have atleast the thickness required in the ice belt in the midbody region, calculated for the actual frame spacing.

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Upper bow ice belt: For ice classes Ice(1A*) and Ice(1A) on ships with an open water service speed equalto or exceeding 18 knots, the shell plate from the upper limit of the ice belt to 2 m above it and from thestem to a position at least 0.2 L abaft the forward perpendicular, shall have at least the thickness required inthe ice belt in the midbody region, calculated for the actual frame spacing.

Guidance note:A similar strengthening of the bow region is advisable also for a ship with a lower service speed, when it is, e.g. on the basis of themodel tests, evident that the ship will have a high bow wave.


For ice class Ice(1A*F), the upper bow ice belt shall be taken 3 m above the normal ice belt, extendingwithin the bow region.Lower bow ice belt: For ice class Ice(1A*F), a lower low ice belt below the normal ice belt is definedcovering the bow region aft of the forefoot and down to the lower turn of bilge.

8.1.3 Sidescuttles shall not be situated in the ice belt. If the weather deck in any part of the ship is situatedbelow the upper limit of the ice belt, e.g. in way of the well of a raised quarter deck, the bulwark shall begiven at least the same strength as is required for the shell in the ice belt. The strength of the construction ofthe freeing ports shall meet the same requirements.

8.2 Plate thickness in the ice belt

8.2.1 For transverse framing the thickness of the shell plating, in mm, shall be determined by the formula:

For longitudinal framing the thickness of the shell plating, in mm, shall be determined by the formula:

where:

PPL = 0.75 PP = as given in [7.3.1]f1 =

, maximum 1.0

f2 = , when

= 1.4 − 0.4 (h/s1); when 1 ≤ h/s1 < 1.8= 0.35 + 0.183 (h/s1) for 1.8 ≤ h/s1 < 3= 0.9 for h/s1 > 3

h = As given in [7.2.1]tc = Increment for abrasion and corrosion in mm; normally 2 mm. If a special surface coating, by

experience shown capable to withstand the abrasion of ice, is applied and maintained, lower valuesmay be approved.

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8.2.2 For ice class Ice(1A*F) the following additional requirements are given:

— bottom plating in the bow region (below the lower bow ice belt defined in [8.1.2]) shall have a grossthickness, in mm, not less than:

— side and bottom plating in the Stern region below the ice belt shall have a gross thickness, in mm, notless than:

9 Frames

9.1 Vertical extension of ice framing

9.1.1 The vertical extension of the ice strengthening of the framing shall be at least as given in Table 15:

Table 15 Vertical extension of ice strengthening of the framing

Ice class Region Above UIWL (m) Below LIWL (m)

Bow to double bottom or below top of floors

Midbody 2.0Ice(1A*F), Ice(1A*)

Stern

1.2

1.6

Bow 1.6

midship 1.3Ice(1A), (1B), (1C)

Stern

1.0

1.0

Where an upper bow ice belt is required (see [8.1.2]), the ice strengthened part of the framing shall beextended at least to the top of this ice belt.

9.1.2 Where the ice strengthening would go beyond a deck or a tank top (or tank bottom) by not more than250 mm, it can be terminated at that deck or tank top (or tank bottom).

9.2 Transverse frames

9.2.1 The gross section modulus of a main or intermediate transverse frame, in cm3, shall be calculated bythe formula:

and the effective gross shear area, in cm2, is calculated from:

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where:

P = ice pressure as given in [7.3.1]h = height of load area as given in [7.2.1]

mt =

f3 = is a factor which takes into account the maximum shear force versus the load location and theshear stress distribution, f3 = 1.2

mo = values as given in Table 16.

Table 16 Values of mo

Boundary condition mo Example

7 Frames in a bulk carrier with top wing tanks

6 Frames extending from the tank top to a single deck

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Boundary condition mo Example

5.7 Continuous frames between several decks or stringers

5 Frames extending between two decks only

The boundary conditions are those for the main and intermediate frames. Possible different conditions formain and intermediate frames are assumed to be taken care of by interaction between the frames and maybe calculated as mean values. Load is applied at mid span.

If the ice belt covers less than half the span of a transverse frame, (b2 < 0.5 ℓ) the following modifiedformula may be used for the gross section modulus in cm3:

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where:

b2 = distance in m between upper or lower boundary of the ice belt and the nearest deck or stringerwithin the ice belt.

Where less than 15% of the span, ℓ, of the frame is situated within the ice-strengthening zone for frames asdefined in [9.1.1], ordinary frame scantlings may be used.

9.2.2 Upper end of transverse framing

1) The upper end of the strengthened part of a main frame and of an intermediate ice frame shall beattached to a deck or an ice stringer (see [10]).

2) Where an intermediate frame terminates above a deck or an ice stringer which is situated at or abovethe upper limit of the ice belt (see [8.1]), the part above the deck or stringer may have the scantlingsrequired for a non-ice-strengthened ship and the upper end be connected to the adjacent main framesby a horizontal member of the same scantlings as the main frame.

9.2.3 Lower end of transverse framing

1) The lower end of the strengthened part of a main frame and of an intermediate ice frame shall beattached to a deck, tank top (or tank bottom) or ice stringer (see [10]).

2) Where an intermediate frame terminates below a deck, tank top (or tank bottom) or ice stringer whichis situated at or below the lower limit of the ice belt (see [7.2]), the lower end shall be connected to theadjacent main frames by a horizontal member of the same scantlings as the main frames. Note that themain frames below the lower edge of ice belt shall be ice strengthened, see [8.1.1].

9.3 Longitudinal frames

9.3.1 The gross section modulus of longitudinal frame with and without brackets, in cm3, shall be calculatedby the formula:

The shear effective gross area of a longitudinal frame, in cm2, shall be:

In calculating the actual shear area of the frames, the shear area of the brackets is not to be taken intoaccount.

f4 = factor which takes account of the load distribution to adjacent frames:f4 = (1 − 0.2 h/s1)f5 = factor which takes into account the maximum shear force versus load location and the shear stress

distribution:f5 = 2.16P = ice pressure as given in [7.3.1]h = height of load area as given in [7.2.1]m1 = is a boundary condition factor; m1= 13.3 for a continuous beam; where the boundary conditions

deviate significantly from those of a continuous beam, e.g. in an end field, a smaller boundaryfactor may be required. For frames without brackets a value m1= 11.0 shall be used.

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9.4 Structural details

9.4.1 Within the ice strengthened area all frames shall be effectively attached to all supporting structures.Longitudinal or transverse frames crossing supporting structures, such as web frames or stringers, shall beconnected to these structures on both sides (by collar plates or lugs in way of cut-outs).Brackets or top stiffeners shall be fitted, in order to provide proper transfer of forces to supporting elements,as necessary. Connection of non-continuous frames to supporting structures shall be made by brackets orsimilar construction. When a bracket is installed, it shall have at least the same thickness as the web plate ofthe frame, and the edge shall be appropriately stiffened against buckling.

9.4.2 For ice class Ice(1A*F) and Ice(1A*), and for ice class Ice(1A) in the bow and midbody regionsand for ice classes Ice(1B) and Ice(1C) in the bow region, the following shall apply in the ice strengthenedarea:

1) Frames which are not at a straight angle to the shell shall be supported against tripping by brackets,intercostals, stringers or similar at a distance preferably not exceeding 1.3 m.Transverse frames perpendicular to shell which are of unsymmetrical profiles shall have trippingpreventions if the span is exceeding 4.0 m.

2) Frames shall be attached to the shell by double continuous welds. No scalloping is allowed (except whencrossing shell plate butts).

3) The web thickness of the frames shall be at least the maximum of the following:

— 9 mm— 2.5% of the frame spacing for transverse frames. Alternatively, the buckling capacity of the

transverse frame may be assessed by direct calculation. Direct calculations shall be based on designloads as given in [4.1.4] and buckling calculation procedures according to Pt.3 Ch.8.

— one half of the net shell plating requirement as given by [8.2.1], where the yield stress, ReH, shall notbe taken larger than that given for the frame

—, hw is the web height and C = 805 for profiles and C = 282 for flat bars.

Where there is a deck, tank top (or tank bottom) or bulkhead in lieu of a frame, the plate thickness ofthis shall be as above, to a depth corresponding to the height of adjacent frames.

10 Ice stringers

10.1 Stringers within the ice belt

10.1.1 The gross section modulus of a stringer situated within the ice belt (see [8.1]), in cm3, shall becalculated by the formula:

The gross shear area, in cm2, shall not be less than:

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where:

P = ice pressure as given in [7.3.1]h = height of load area as given in [7.2.1]

The product Ph shall not be taken as less than 150.ℓ = span of stringer, in mm1 = boundary condition factor as given in [9.3.1]f6 = which takes account of the distribution of load to the transverse frames; to be taken as 0.9f7 = factor of stringers; to be taken as 1.8f8 = factor that takes into account the maximum shear force versus load location and the shear stress

distribution; f8 = 1.2.

10.2 Stringers outside the ice belt

10.2.1 The gross section modulus of a stringer situated outside the ice belt but supporting ice strengthenedframes, in cm3, shall be calculated by the formula:

The gross shear area, in cm2, shall not be less than:

where:

P = ice pressure as given in [7.3.1]h = height of load area as given in [7.2.1].

The product Ph shall not be taken as less than 150.

ℓ = span of stringer, in mm1 = boundary condition factor as given in [9.3.1]ℓs = the distance to the adjacent ice stringer, in mhs = the distance to the ice belt, in mf9 = factor which takes account of the distribution of load to the transverse frames; to be taken as 0.80f10 = safety factor of stringers; to be taken as 1.8f11 = factor that takes into account the maximum shear force versus load location and the shear stress

distribution; f11 = 1.2.

10.3 Deck strips

10.3.1 Narrow deck strips abreast of hatches and serving as ice stringers shall comply with the sectionmodulus and shear area requirements in [10.1] and [10.2] respectively. In the case of very long hatches thelower limit of the product Ph may be reduced to 100.

10.3.2 Regard shall be paid to the deflection of the ship's sides due to ice pressure in way of very long hatchopenings (more than B/2), when designing weather deck hatch covers and their fittings.

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11 Web frames

11.1 Design ice load

11.1.1 The design ice load transferred to a web frame from an ice stringer or from longitudinal framing, inkN, shall be calculated by the formula:

where:

P = ice pressure as given in [7.3.1], when calculating factor ca, however, ℓa shall be taken as 2 S

h = height in m of load area as given in [7.2.1].

The product Ph shall not be taken less than 150.

S = web frame spacing, in mf12 = factor of web frames; to be taken as 1.8.

In case the supported stringer is outside the ice belt, the load F may be multiplied by:

as given in [10.2.1].

11.2 Section modulus and shear area

11.2.1 The gross section modulus requirement, in cm3, is given by:

where:

M = maximum calculated bending moment, in kNm, under the ice load F, as given in [11.1.1]. This shallbe taken as M = 0.193 · F · ℓ

γ = as given in Table 17A = required gross shear area from [11.2.2], in cm2

Aa = actual gross cross sectional area of web frame, Aa = Af + Aw, in cm2.

11.2.2 With boundary conditions as given in [11.2.1], the gross shear area of a web frame, in cm2, is givenby:

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where:

Q = maximum calculated shear force under the load F, in kN, as given in [11.1.1]f13 = factor that takes into account the shear force distribution, f13 = 1.1α = factor given in Table 17Af = gross cross sectional area of free flange, in cm2

Aw = actual effective gross cross sectional area of web plate, in cm2.

Table 17 Values of α and γ

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0

α 1.5 1.23 1.16 1.11 1.09 1.07 1.06 1.05 1.05 1.04 1.04

γ 0 0.44 0.62 0.71 0.76 0.80 0.83 0.85 0.87 0.88 0.89

12 Bilge keels

12.1 Arrangement

12.1.1 The connection of bilge keels to the hull shall be so designed that the risk of damage to the hull, incase a bilge keel is ripped off, is minimised.

12.1.2 For class Ice(1A*F) bilge keels are normally to be avoided and should be replaced by roll-dampingequipment. Specially strengthened bilge keels may be considered.

13 Special arrangement and strengthening forward

13.1 Stem, Baltic ice strengthening

13.1.1 The stem may be made of rolled, cast or forged steel or of shaped steel plates. as shown in Figure 4.

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Figure 4 Examples of suitable stems

13.1.2 The plate thickness of a shaped plate stem and in the case of a blunt bow, any part of the shell whereα ≥ 30° and ψ ≥ 75° (see [15.1.3] for angle definitions), shall be calculated according to the formulae in[8.2] assuming that:

s = spacing of elements supporting the plate in mPPL = P (see [7.3.1])ℓa = spacing of vertical supporting elements in m, see Table 13.

For class Ice(1A*F) the front plate and upper part of the bulb and the stem plate up to a point 3.6 m aboveUIWL (lower part of bow door included) shall have a minimum gross thickness, in mm, of:

where:

c = 2.3 for the stem plate= 1.8 for the bulb plating.

The width of the increased bulb plate shall not be less than 0.2 b on each side of the centre line, b = breadthof the bulb at the forward perpendicular.

13.1.3 The stem and the part of a blunt bow defined above shall be supported by floors or brackets spacednot more than 0.6 m apart and having a thickness of at least half the plate thickness. The reinforcement ofthe stem shall be extend from the keel to a point 0.75 m above UIWL or, in case an upper bow ice belt isrequired (see [8.1.2]) to the upper limit of this.

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13.2 Arrangements for towing

13.2.1 The ship shall be arranged for towing.

13.2.2 A bitt or other means for securing a towline, dimensioned to stand the breaking force of the towlineof the ship shall be fitted.

14 Special arrangement and strengthening aft

14.1 Stern

14.1.1 The introduction of new propulsion arrangements with azimuth thrusters or podded propellers, whichprovide an improved manoeuvrability, will result in increased ice loading of the stern region and stern area.This fact should be considered in the design of the aft/stern structure.

14.1.2 In order to avoid very high loads on propeller blade tips, the minimum distance between propeller(s)and hull (including stern frame) should not be less than h0 (see [7.2.1]).

14.1.3 On twin and triple screw ships the ice strengthening of the shell and framing shall be extended to thedouble bottom for 1.5 metre forward and aft of the side propellers.

14.1.4 Shafting and stern tubes of side propellers are normally to be enclosed within plated bossings. Ifdetached struts are used, their design, strength and attachment to the hull shall be duly considered.For class Ice(1A*F) the gross skin plating of propeller shaft bossings, in mm, shall not be less than:

14.1.5 The part of a transom stern situated within the ice belt shall be strengthened as for the midshipregion.

14.2 Rudder and steering arrangements

14.2.1 The scantlings of rudder, rudder post, rudder stock, pintles, steering gear etc. as well as the capacityof the steering gear shall be determined according to the rules. The maximum service speed of the ship to beused in these calculations shall not be taken less than that stated below:

Table 18 Maximum service speed

Ice class Maximum service speed

Ice(1A*)

Ice(1A)

Ice(1B)

Ice(1C)

20 knots

18 knots

16 knots

14 knots

If the actual maximum service speed of the ship is higher, that speed shall be used.When calculating the rudder force according to the formula given in Pt.3 Ch.14 Sec.1 [2] and with the speedV in ahead condition as given above, the factors K2 = K3 = 1.0 irrespective of condition, rudder profile typeor arrangement, shall be used. In the astern condition half the speed values shall be used.

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14.2.2 For the ice classes Ice(1A*) and Ice(1A), the upper part of the rudder and the rudder stockshall be protected from direct contact with intact ice by an ice horn that extends below the LIWL. Specialconsideration shall be given to the design of the rudder and the ice horn for ships with flap-type rudders.

14.2.3 For ice classes Ice(1A*) and Ice(1A), due regard shall be paid to the large loads that arisewhen the rudder is forced out of the midship position while going astern in ice or into ice ridges. Suitablearrangement such as rudder stoppers shall be installed to absorb these loads.

14.2.4 Relief valves for hydraulic pressure in rudder turning mechanism(s) shall be installed. Thecomponents of the rudder actuator, rudder stock and rudder coupling shall be dimensioned to withstandloading corresponding to the required diameter of the rudder stock.

14.2.5 The local scantlings of rudders shall be determined assuming that the whole rudder belongs to theice belt. Further, the rudder plating and frames shall be designed using the ice pressure P for the plating andframes in the midbody region.

15 Propulsion machinery

15.1 Materials15.1.1 Materials exposed to sea waterMaterials of components exposed to sea water, such as propeller blades, propeller hubs, and thruster body,shall have an elongation of not less than 15% on a test specimen, the gauge length of which is five times thediameter. A Charpy V impact test shall be carried out for materials other than bronze and austenitic stainlesssteel. An average impact energy value of 20 J taken from three tests shall be obtained at minus 10ºC.

15.1.2 Materials exposed to sea water temperatureMaterials exposed to sea water temperature shall be of ductile material. An average impact energy valueof 20 J taken from three tests shall be obtained at minus 10ºC. This requirement applies to blade bolts,CP mechanisms, shaft bolts, strut-pod connecting bolts etc. This does not apply to surface hardenedcomponents, such as bearings and gear teeth.

15.2 Design loads for propeller and shafting

15.2.1 These regulations apply to propulsion machinery covering open- and ducted-type propellers withcontrollable pitch or fixed pitch design for the ice classes Ice(1A*), Ice(1A), Ice(1B) and Ice(1C). Thegiven loads are the expected ice loads for the whole ship's service life under normal operational conditions,including loads resulting from the changing rotational direction of FP propellers. However, these loads do notcover off-design operational conditions, for example when a stopped propeller is dragged through ice.The regulations also apply to azimuth’s and fixed thrusters for main propulsion, considering loads resultingfrom propeller/ice interaction. However, the load models do not include propeller/ice interaction loads whenice enters the propeller of a turned azimuth thruster from the side (radially) or load case when ice block hitson the propeller hub of a pulling propeller.

15.2.2 Design ice conditionsIn estimating the ice loads of the propeller for ice classes, different types of operation as given in Table 19were taken into account. For the estimation of design ice loads, a maximum ice block size is determined. Themaximum design ice block entering the propeller, is a rectangular ice block with the dimensions Hice × 2Hice× 3Hice. The thickness of the ice block (Hice) is given in Table 20.

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Table 19 Operation of the ship - design basis

Ice(1A*) Operation in ice channels and in level ice. The ship may proceed by ramming

Ice(1A)…1C Operation in ice channels

Table 20 Thickness of the design maximum ice block Hice entering the propeller

Ice class Ice(1A*) Ice(1A) Ice(1B) Ice(1C)

(Hice) 1.75 m 1.5 m 1.2 m 1.0 m

Table 21 List of symbols

Symbol Unit Definition

A.P. the after perpendicular is the perpendicular at the after end of the length L

c m chord length of blade section

c0.7 m chord length of blade section at 0.7R propeller radius

CP controllable pitch

D m propeller diameter

d m external diameter of propeller hub

Dlimit m limit value for propeller diameter

EAR expanded blade area ratio

Fb kN maximum backward blade force for the ship’s service life

Fex kN ultimate blade load resulting from blade loss through plastic bending

Ff kN maximum forward blade force for the ship’s service life

Fice kN ice load

(Fice)max kN maximum ice load for the ship’s service life

FP fixed pitch

F.P. the forward perpendicular is the perpendicular at the intersection of the summer load waterline withthe fore sideof the stem. For ships with unusual bow arrangements the position of the F.P. will beespecially considered.

h0 m depth of the propeller centreline from the winter waterline

Hice m thickness of maximum design ice block entering to propeller

I kgm2 equivalent mass moment of inertia of all parts on engine side of component under consideration

It kgm2 equivalent mass moment of inertia of the whole propulsion system

k shape parameter for Weibull distribution

LIWL m lower ballast waterline in ice

m slope for SN curve in log/log scale

MBL kNm blade bending moment

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MCR maximum continuous rating

n rev/s propeller rotational speed

nn rev/s nominal propeller rotational speed at MCR in free running condition

Nclass reference number of impacts per propeller rotational speed per ice class

Nice total number of ice loads on propeller blade for the ship’s service life

NR reference number of load for equivalent fatigue stress (108 cycles)

NQ number of propeller revolutions during a milling sequence

P0.7 m propeller pitch at 0.7R radius

P0.7n m propeller pitch at 0.7R radius at MCR in free running condition

P0.7b m propeller pitch at 0.7R radius at MCR in bollard condition

Q kNm torque

Qemax kNm maximum engine torque

Qmax kNm maximum torque on the propeller resulting from propeller-ice interaction

Qmotor kNm electric motor peak torque

Qn kNm nominal torque at MCR in free running condition

Qr kNm maximum response torque along the propeller shaft line

Qsmax kNm maximum spindle torque of the blade for the ship’s service life

R m propeller radius

r m blade section radius

T kN propeller thrust

Tb kN maximum backward propeller ice thrust for the ship’s service life

Tf kN maximum forward propeller ice thrust for the ship’s service life

Tn kN propeller thrust at MCR in free running condition

Tr kN maximum response thrust along the shaft line

t m maximum blade section thickness

Z number of propeller blades

αi deg duration of propeller blade/ice interaction expressed in rotation angle

γε the reduction factor for fatigue; scatter and test specimen size effect

γν the reduction factor for fatigue; variable amplitude loading effect

γm the reduction factor for fatigue; mean stress effect

ρ a reduction factor for fatigue correlating the maximum stress amplitude to the equivalent fatiguestress for 108 stress cycles

σ0.2 MPa proof yield strength of blade material

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σexp MPa mean fatigue strength of blade material at 108 cycles to failure in sea water

σfat MPa equivalent fatigue ice load stress amplitude for 108 stress cycles

σfl MPa characteristic fatigue strength for blade material

σref MPa reference stress (ultimate strength) σref = 0.6 σ0.2 + 0.4 σu

σref2 MPa reference stress (blade scantlings) σref2 = 0.7 σu or σref2 = 0.6 σ0.2 + 0.4 σu whichever is less

σst MPa maximum stress resulting from Fb or Ff

σu MPa ultimate tensile strength of blade material

(σice)bmax MPa principal stress caused by the maximum backward propeller ice load

(σice)fmax MPa principal stress caused by the maximum forward propeller ice load

(σice)max MPa maximum ice load stress amplitude

Table 22 Definition of ice loads

Load Definition Use of the load in design process

Fb The maximum lifetime backward force on a propellerblade resulting from propeller/ice interaction, includinghydrodynamic loads on that blade. The direction of theforce is perpendicular to 0.7 r/R chord line. See Figure5

Design force for strength calculation of the propellerblade.

Ff The maximum lifetime forward force on a propellerblade resulting from propeller/ice interaction, includinghydrodynamic loads on that blade. The direction of theforce is perpendicular to 0.7 r/R chord line.

Design force for calculation of strength of the propellerblade.

Qsmax The maximum lifetime spindle torque on a propellerblade resulting from propeller/ice interaction, includinghydrodynamic loads on that blade.

In designing the propeller strength, the spindle torqueis automatically taken into account because thepropeller load is acting on the blade as distributedpressure on the leading edge or tip area.

Tb The maximum lifetime thrust on propeller (all blades)resulting from propeller/ice interaction. The direction ofthe thrust is the propeller shaft direction and the forceis opposite to the hydrodynamic thrust.

Is used for estimation of the response thrust Tr. Tb canbe used as an estimate of excitation for axial vibrationcalculations. However, axial vibration calculations arenot required in the rules.

Tf The maximum lifetime thrust on propeller (all blades)resulting from propeller/ice interaction. The direction ofthe thrust is the propeller shaft direction acting in thedirection of hydrodynamic thrust.

Is used for estimation of the response thrust Tr.Tf canbe used as an estimate of excitation for axial vibrationcalculations. However, axial vibration calculations arenot required in the rules.

Qmax The maximum ice-induced torque resulting frompropeller/ice interaction on one propeller blade,including hydrodynamic loads on that blade.

Is used for estimation of the response torque (Qr)along the propulsion shaft line and as excitation fortorsional vibration calculations.

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Load Definition Use of the load in design process

Fex Ultimate blade load resulting from blade loss throughplastic bending. The force that is needed to cause totalfailure of the blade so that plastic hinge is caused to theroot area. The force is acting on 0.8 r/R. Spindle armshall be taken as 2/3 of the distance between the axisof blade rotation and leading/trailing edge (whichever isthe greater) at the 0.8R radius.

Blade failure load is used to dimension the blade bolts,pitch control mechanism, propeller shaft, propellershaft bearing and trust bearing. The objective shallguarantee that total propeller blade failure should notcause damage to other components.

Qr Maximum response torque along the propeller shaftline, taking into account the dynamic behaviour of theshaft line for ice excitation (torsional vibration) andhydrodynamic mean torque on propeller.

Design torque for propeller shaft line components.

Tr Maximum response thrust along shaft line, taking intoaccount the dynamic behaviour of the shaft line for iceexcitation (axial vibration) and hydrodynamic meanthrust on propeller.

Design thrust for propeller shaft line components.

Qg Fatigue torque at reduction gear for Ng load cycles. Design torque for reduction gear.

Figure 5 Direction of the backward blade force resultant taken perpendicular to chord line at 0.7r/R

(Ice contact pressure at leading edge is shown with small arrows)

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15.3 Design loads

15.3.1 The given loads are intended for component strength calculations only and are total loads includingice-induced loads and hydrodynamic loads during propeller/ice interaction.

15.3.2 The values of the parameters in the formulae in this section shall be given in the units shown in thesymbol list.

15.3.3 If the propeller is not fully submerged when the ship is in ballast condition, the propulsion systemshall be designed according to ice class Ice(1A) for ice classes Ice(1B) and Ice(1C).

15.4 Design loads on propeller blades

15.4.1 Fb is the maximum force experienced during the lifetime of the ship that bends a propeller bladebackwards when the propeller mills an ice block while rotating ahead. Ff is the maximum force experiencedduring the lifetime of the ship that bends a propeller blade forwards when the propeller mills an ice blockwhile rotating ahead. Fb and Ff originate from different propeller/ice interaction phenomena, not actingsimultaneously. Hence they shall be applied to one blade separately.

15.4.2 Maximum backward blade force Fb, in kN, for open propellers

when

when

where:

in m

n is the nominal rotational speed (at MCR in free running condition) for a CP propeller and 85% of thenominal rotational speed (at MCR in free running condition) for an FP propeller.

15.4.3 Maximum forward blade force Ff, in kN, for open propellers

when

when

where:

15.4.4 Loaded area on the blade for open propellersLoad cases 1 to 4 have to be covered, as given in Table 23 below, for CP and FP propellers. The load case 5applies to reversible propellers in addition to the cases 1 to 4.

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Table 23 Load cases for open propellers

Load case Force Loaded area Right-handed propellerblade seen from behind

Load case 1 Fb Uniform pressure applied on the back ofthe blade (suction side) to an area from0.6R to the tip and from the leading edgeto 0.2 times the chord length.

Load case 2 50% of Fb Uniform pressure applied on the back ofthe blade (suction side) on the propellertip area outside 0.9R radius.

Load case 3 Ff Uniform pressure applied on the bladeface (pressure side) to an area from 0.6Rto the tip and from the leading edge to0.2 times the chord length.

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Load case Force Loaded area Right-handed propellerblade seen from behind

Load case 4 50% of Ff Uniform pressure applied on propellerface (pressure side) on the propeller tiparea outside 0.9R radius.

Load case 5 60% of Ff orFb, whicheveris greater

Uniform pressure applied on propellerface (pressure side) to an area from 0.6Rto the tip and from the trailing edge to0.2 times the chord length

15.4.5 Maximum backward blade ice force Fb, in kN, for ducted propellers

when

when

where:

, in m

n is the nominal rotational speed (at MCR in free running condition) for a CP propeller and 85% of thenominal rotational speed (at MCR in free running condition) for an FP propeller.

15.4.6 Maximum forward blade ice force Ff, in kN, for ducted propellers

when

when

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where:

, in m

15.4.7 Loaded area on the blade for ducted propellersLoad cases 1 and 3 have to be covered as given in Table 24 for all propellers, and an additional load case(load case 5) for an FP propeller, to cover ice loads when the propeller is reversed.

Table 24 Load cases for ducted propellers

Load case Force Loaded area Right handed propellerblade seen from behind

Load case 1 Fb Uniform pressure applied on the back of theblade (suction side) to an area from 0.6Rto the tip and from the leading edge to 0.2times the chord length.

Load case 3 Ff Uniform pressure applied on the blade face(pressure side) to an area from 0.6R to thetip and from the leading edge to 0.5 timesthe chord length.

Load case 5 60% ofFf or Fb,whichever isgreater

Uniform pressure applied on propeller face(pressure side) to an area from 0.6R to thetip and from the trailing edge to 0.2 timesthe chord length.

15.4.8 Maximum blade spindle torque Qsmax for open and ducted propellersThe spindle torque Qsmax, in kNm, around the axis of the blade fitting shall be determined both for themaximum backward blade force Fb and forward blade force Ff, which are applied as in Table 23 and Table

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24. If the above method gives a value which is less than the default value given by the formula below, thedefault value shall be used.

Default value:

where c0.7 is the length of the blade section at 0.7R radius and F is either Fb or Ff, whichever has the greaterabsolute value.

15.4.9 Load distribution for blade loadsThe Weibull-type distribution (probability of exceeding), as given in Figure 6, is used for the fatigue design ofthe blade.

Here, k is the shape parameter of the spectrum, Nice is the number of load cycles in the spectrum, and Ficeis the random variable for ice loads on the blade, 0 ≤ Fice ≤ (Fice)max. The shape parameter k = 0.75 shall beused for the ice force distribution of an open propeller and the shape parameter k = 1.0 for that of a ductedpropeller blade.

Figure 6 The Weibull-type distribution (probability of exceeding) that is used for fatigue design

15.4.10 Number of ice loadsThe number of load cycles per propeller blade in the load spectrum shall be determined according to theformula:

where:n is propeller nominal rps as defined for loads.

Table 25 Reference number of loads for ice classes Nclass

Ice(1A*) Ice(1A) Ice(1B) Ice(1C)

Impacts in life/n 9·106 6·106 3.4·106 2.1·106

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Table 26 Propeller location factor k1

Single propeller Twin propeller

location centreline twin wing

k1 1 1.35

Table 27 Propeller type factor k2

Type Open Ducted

k2 1 1.1

Table 28 Propulsion type factor k3

Type Fixed Azimuting

k3 1 1.2

The submersion factor k4 is determined from the equation

when

when

when

when

where the immersion function f is:

where ho is the depth of the propeller centreline at the lower ballast waterline in ice (LIWL) of the ship.For components that are subject to loads resulting from propeller/ice interaction with all the propeller blades,the number of load cycles (Nice) shall be multiplied by the number of propeller blades (Z).

15.5 Axial design loads for open and ducted propellers15.5.1 Design ice thrust on propeller Tb and Tf for open and ducted propellersThe maximum forward and backward ice thrusts, in kN, are:

15.5.2 Design thrust along the propulsion shaft line for open and ducted propellersThe design thrust, in kN, along the propeller shaft line shall be calculated with the formulae below. Thegreater value of the forward and backward direction loads shall be taken as the design load for bothdirections. The factors 2.2 and 1.5 take into account the dynamic magnification resulting from axial vibration.In a forward direction

In a backward direction

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If the hydrodynamic bollard thrust, T, is not known, T shall be taken from Table 29, where Tn is the nominalpropeller thrust at MCR in free running open water condition

Table 29 Selection of bollard thrust *)

Propeller type T

CP propellers (open) 1.25 Tn

CP propellers (ducted) 1.1 Tn

FP propellers driven by turbine or electric motor Tn

FP propellers driven by diesel engine (open) 0.85 Tn

FP propellers driven by diesel engine (ducted) 0.75 Tn

*) When not known

15.6 Torsional design loads15.6.1 Design ice torque on propeller Qmax for open propellersQmax is the maximum torque, in kNm, on a propeller resulting from ice/propeller interaction.

when

when

where:

, in m

For CP propellers, the propeller pitch, P0.7 shall correspond to MCR in bollard condition. If not known, P0.7shall be taken as 0.7·P0.7n, where P0.7n is the propeller pitch at MCR in free running condition.

Table 30 Rotational speed selection *)

Propeller type Rotational speed n

CP propellers nn

FP propellers driven by turbine or electric motor nn

FP propellers driven by diesel engine 0.85 nn

*)nn refers to MCR free running condition

15.6.2 Design ice torque on propeller Qmax for ducted propellersQmax is the maximum torque, in kNm, on a propeller resulting from ice/propeller interaction.

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when

when

where:

, in m

and n and P0.7 as defined for open propeller.

15.6.3 Ice torque excitation for open and ducted propellersThe propeller ice torque excitation for shaft line transient torsional vibration analysis shall be described by asequence of blade impacts which are of a half sine shape, see Figure 7.The torque resulting from a single blade ice impact as a function of the propeller rotation angle is then

when

when

where Cq and αi parameters are given in the Table 31 and αi is duration of propeller blade/ice interactionexpressed in propeller rotation angle.

Table 31 Torque excitation parameters

Torque excitation Propeller/ice interaction Cq αi

Case 1 Single ice block 0.75 90


Case 3 Two ice blocks (phase shift 45 deg.) 0.5 45

The total ice torque is obtained by summing the torque of single blades, taking into account the phase shift360 degrees/Z. In addition, at the beginning and at the end of the milling sequence a linear ramp functionsfor 270 degrees of rotation angle shall be used.The number of propeller revolutions during a milling sequence shall be obtained with the formula:

The number of impacts is Z·NQ for blade order excitation.

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For 90- and 135-degree single-blade impact sequences and 45 degree double blade impact sequence (figuresapply for propellers with 4 blades.)

Figure 7 The shape of the propeller ice torque excitation

15.6.4 Design torque along propeller shaft lineIf there is not any relevant first blade order torsional resonance within the designed operating rotationalspeed range extended 20% above the maximum and 20% below the minimum operating speeds, thefollowing estimation of the maximum torque, in kNm, can be used:

where I is equivalent mass moment of inertia of all parts on engine side of component under considerationand It is equivalent mass moment of inertia of the whole propulsion system. All the torques and the inertiamoments shall be reduced to the rotation speed of the component being examined.

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If the maximum torque, Qemax, is not known, it shall be taken as follows, where Qmotor is the electric motorpeak torque:

Table 32 Selection of maximum motor torque Qemax

Propeller type Qemax

Propellers driven by electric motor Qmotor

CP propellers not driven by electric motor Qn

FP propellers driven by turbine Qn

FP propellers driven by diesel engine 0.75 Qn

If there is a first blade order torsional resonance within the designed operating rotational speed rangeextended 20% above the maximum and 20% below the minimum operating speeds, the design torque (Qr)of the shaft component shall be determined by means of torsional vibration analysis of the propulsion line.

15.7 Blade failure load

15.7.1 The ultimate load, in kN, resulting from blade failure as a result of plastic bending around the bladeroot shall be calculated with the formula below. The ultimate load is acting on the blade at the 0.8R radiusin the weakest direction of the blade. For calculation of the extreme spindle torque, the spindle arm shall betaken as 2/3 of the distance between the axis of blade rotation and the leading/trailing edge (whichever isthe greater) at the 0.8R radius.

where:

c, t, and r are, respectively, the length, thickness, and radius of the cylindrical root section of the blade at theweakest section outside the root fillet.

15.8 Design principle

15.8.1 The strength of the propulsion line shall be designed according to the pyramid strength principle. Thismeans that the loss of the propeller blade shall not cause any significant damage to other propeller shaft linecomponents.

15.8.2 The propulsion system shall be designed in such a way that the complete dynamic system is freefrom harmful torsional, axial, and bending resonances at a 1-order blade frequency within the designedrunning speed range, extended by 20 per cent above and below the maximum and minimum operatingrotational speeds. If this condition cannot be fulfilled, a detailed vibration analysis has to be carried out inorder to determine that the acceptable strength of the components can be achieved.

15.9 Propeller blade design15.9.1 Calculation of blade stressesThe blade stresses shall be calculated for the design loads given in [15.4]. Finite element analysis shall beused for stress analysis for final approval for all propellers.

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The following simplified formulae can be used in estimating the blade stresses for all propellers at the rootarea (r/R < 0.5). The root area dimensions will be accepted even if the FEM analysis would show greaterstresses, in N/mm2, at the root area.

where the constant R1 is the actual stress/stress obtained with beam equation.If the actual value is not available, R1 should be taken as 1.6.

For relative radius r/R < 0.5F is the maximum of Fb and Ff, whichever is greater.

15.9.2 Acceptability criterion - maximum load (static)The following criterion for calculated blade stresses has to be fulfilled.

Where σst is the calculated stress for the design load. If FE analysis is used in estimating the stresses, vonMises stresses shall be used.σref 2 is the reference stress, defined as:σref 2 = 0.7·σu

orσref 2 = 0.6·σ0.2 + 0.4 σu

whichever is less.

15.9.3 Fatigue design of propeller bladeThe fatigue design of the propeller blade is based on an estimated load distribution for the service life of theship and the S-N curve for the blade material. An equivalent stress that produces the same fatigue damageas the expected load distribution shall be calculated and the acceptability criterion for fatigue should befulfilled as given in this section. The equivalent stress is normalised for 100 million cycles.If the following criterion is fulfilled fatigue calculations according to this section are not required.

where B1, B2 and B3 coefficients for open and nozzle propellers are given in the Table 33 below.

Table 33 B coefficients

Coefficient Open propeller Nozzle propeller

B1 0.00270 0.00184

B2 1.007 1.007

B3 2.101 2.470

For calculation of equivalent stress two types of SN curves are available.

1) Two slope SN curve (slopes 4.5 and 10), see Figure 8.2) One slope SN curve (the slope can be chosen), see Figure 9.

The type of the SN-curve shall be selected to correspond to the material properties of the blade. If SN-curveis not known the two slope SN curve shall be used.

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Figure 8 Two-slope S-N curve

Figure 9 Constant-slope S-N curve

15.9.4 Equivalent fatigue stressThe equivalent fatigue stress for 100 million stress cycles which produces the same fatigue damage as theload distribution is:

where:

(σice)max = the mean value of the principal stress amplitudes resulting from design forward and backwardblade forces at the location being studied.

(σice)f max = the principal stress resulting from forward load.(σice)b max = the principal stress resulting from backward load.

In calculation of (σice)max, load case 1 and load case 3 (or case 2 and case 4) are considered as a pair for(σice)f max, and (σice)b max calculations. Load case 5 is excluded from the fatigue analysis.

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15.9.5 Calculation of ρ parameter for two-slope S-N curveThe parameter ρ relates the maximum ice load to the distribution of ice loads according to the regressionformulae:

where:

γε = the reduction factor for scatter and test specimen size effectγν = the reduction factor for variable amplitude loadingγm = the reduction factor for mean stressσexp = the mean fatigue strength of the blade material at 108 cycles to failure in seawater.

The following values should be used for the reduction factors if actual values are not available: γε = 0.67, γν

= 0.75, and γm= 0.75.

The coefficients C1, C2, C3, and C4 are given in Table 34.

Table 34 C coefficients

Coefficient Open propeller Nozzle propeller

C1 0.000711 0.000509

C2 0.0645 0.0533

C3 -0.0565 -0.0459

C4 2.22 2.584

15.9.6 Calculation of ρ parameter for constant-slope S-N curveFor materials with a constant-slope S-N curve, see Figure 9 The ρ-factor shall be calculated with the followingformula:

where k is the shape parameter of the Weibull distribution, k = 1.0 for ducted propellers and k = 0.75 foropen propellers.NR is the reference number of load cycles (=100 million).Values for the G parameter are given in Table 35. Linear interpolation may be used to calculate the G valuefor other m/k ratios than given in the Table 35.

Table 35 Value for the G parameter for different m/k ratios

m/k G m/k G m/k G

3 6 5.5 287.9 8 40 320

3.5 11.6 6 720 8.5 119 292

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4 24 6.5 1871 9 362 880

4.5 52.3 7 5040 9.5 1.133 · 106

5 120 7.5 14034 10 3.623 · 106

15.9.7 Acceptability criterion for fatigueThe equivalent fatigue stress at all locations on the blade has to fulfil the following acceptability criterion:

where:

γε = the reduction factor for scatter and test specimen size effectγν = the reduction factor for variable amplitude loadingγm = the reduction factor for mean stressσexp = the mean fatigue strength of the blade material at 108 cycles to failure in seawater.

The following values should be used for the reduction factors if actual values are not available: γε = 0.67, γν

= 0.75, and γm= 0.75.

15.10 Propeller bossing and CP mechanism

15.10.1 The blade bolts, the CP mechanism, the propeller boss, and the fitting of the propeller to thepropeller shaft shall be designed to withstand the maximum and fatigue design loads, as defined in [15.4].The safety factor against yielding shall be greater than 1.3 and that against fatigue greater than 1.5. Inaddition, the safety factor for loads resulting from loss of the propeller blade through plastic bending asdefined in [15.7] shall be greater than 1.0 against yielding.

15.11 Propulsion shaft line

15.11.1 The shafts and shafting components, such as the thrust and stern tube bearings, couplings, flangesand sealing, shall be designed to withstand the propeller/ice interaction loads as given in [15.4] - [15.6]. Thesafety factor shall be at least 1.3.

15.11.2 The design torque Qr determined according to [15.6] shall be applied for low cycle and high cyclestrength analysis respectively.

15.11.3 Shafts and shafting componentsThe ultimate load resulting from total blade failure as defined in [15.7] should not cause yielding in shaftsand shaft components. The loading shall consist of the combined axial, bending, and torsion loads, whereverthis is significant. The minimum safety factor against yielding shall be 1.0 for bending and torsional stresses.Forward of the after peak bulkhead, the shaft may be evenly tapered down to 1.05 times the rule diameter ofintermediate shaft, but not less than the actual diameter of the intermediate shaft.

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15.12 Design of shaft line components not specifically mentioned in FSICR

15.12.1 Below criteria are given for application of Pt.4 Ch.4 for determination of scantlings for intermediateshafts, couplings, reduction gears and crank shafts.Application factor KAice = Qr/Qn shall be used for low cycle criteria and/or static load criteria (see [15.12.3]).For components where fatigue is dimensioning, e.g. shaft and reduction gear, cumulative fatigue analysis arerequired. The actual Qr/Qn ratios shall be determined as given in [15.6.4].

15.12.2 The diameter of intermediate shafts shall be determined based on methods given in Pt.4 Ch.4 Sec.1[2.2.1].

a) When using the class guideline DNVGL-CG-0038 the necessary reinforcement is determined by usingKAice = Qr/Qn in the given criteria.

b) With Qr/Qn ≤ 1.4 the method in Pt.4 Ch.4 Sec.1 [2.2.6] may be used, i.e. no ice reinforcement beyondthe rules for main class.

When using the method in Pt.4 Ch.4 Sec.1 [2.2.8], the minimum diameter in item 3 of that paragraph shallbe multiplied with:(Qr/1.4 Qn)

1/3, where Qr is relevant maximum value, but not less than 1.0.

In item 4 of same paragraph, the vibratory torsional stress τv is replaced by:

τv = 0.5 (Qr/Qn - 1) To

and shall not exceed τC.

15.12.3 Regarding shaft connections, use KAice = Qr/Qn in Pt.4 Ch.4 Sec.1 as follows:

— flange connections, see Pt.4 Ch.4 Sec.1 [2.3]— shrink fit connections, see Pt.4 Ch.4 Sec.1 [2.4]— keyed connections, see Pt.4 Ch.4 Sec.1 [2.5].

Connections transmitting ice axial load determined in [15.5] and [15.7] from the propeller to the thrustbearing shall be capable of transmitting relevant loads without consequential damage.

15.12.4 For reduction gears, use KAice = Qr/Qn in Pt.4 Ch.4 Sec.2.

15.12.5 For clutches, use KAice = Qr/Qn in Pt.4 Ch.4 Sec.3 [2.1].

15.12.6 For torsional elastic coupling, use KAice = Qr/Qn in Pt.4 Ch.4 Sec.5 [2.2].

15.12.7 For crank shafts in direct coupled diesel engines, see Pt.4 Ch.3 Sec.1 [2.5.7].

15.13 Azimuth main propulsors and other thrusters

15.13.1 Special consideration shall be given to those loading cases which are extraordinary for propulsionunits when compared with conventional propellers. The estimation of loading cases shall reflect the way ofoperation of the ship and the thrusters. In this respect, for example, the loads caused by the impacts of iceblocks on the propeller hub of a pulling propeller shall be considered. Furthermore, loads resulting from thethrusters operating at an oblique angle to the flow shall be considered. The steering mechanism, the fitting ofthe unit, and the body of the thruster shall be designed to withstand the loss of a blade without damage. Theloss of a blade shall be considered for the propeller blade orientation which causes the maximum load on thecomponent being studied. Typically, top-down blade orientation places the maximum bending loads on thethruster body.

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15.13.2 Azimuth thrusters shall also be designed for estimated loads caused by thruster body/iceinteraction. The thruster body shall withstand the loads obtained when the maximum ice blocks, which aregiven in the design ice conditions section, strike the thruster body when the ship is at a typical ice operatingspeed. In addition, the design situation in which an ice sheet glides along the ship's hull and presses againstthe thruster body shall be considered. The thickness of the sheet shall be taken as the thickness of themaximum ice block entering the propeller, as defined in the dDesign ice conditions section.

15.13.3 Tunnel thrustersIce strengthening of tunnel thrusters is not required.

15.13.4 Other thrusterThrusters other than propulsion thrusters and tunnel thrusters need only comply with the relevantrequirements in [15] if they shall be used in ice conditions or for any reason be exposed to ice loads.For thrusters that are not intended for use in ice conditions, this will be stated in the class certificate and onsignboards fitted at all relevant manoeuvring stands.

15.13.5 The relevant structure parts of non-retractable thrusters shall be strengthened with respect to iceloads, independent of whether they are used in ice conditions or not.

15.14 Alternative design15.14.1 ScopeAs an alternative to [15.2]to[15.13], a comprehensive design study may be carried out to the satisfaction ofthe administration. The study shall be based on ice conditions given for different ice classes in [4.1]. It shallinclude both fatigue and maximum load design calculations and fulfil the pyramid strength principle, as givenin [15.8].

15.14.2 LoadingLoads on the propeller blade and propulsion system shall be based on an acceptable estimation ofhydrodynamic and ice loads.

15.14.3 Design levelsThe analysis shall indicate that all components transmitting random (occasional) forces, excluding propellerblade, are not subjected to stress levels in excess of the yield stress of the component material, with areasonable safety margin.Cumulative fatigue damage calculations shall indicate a reasonable safety factor. Due account shall be takenof material properties, stress raisers, and fatigue enhancements.Vibration analysis shall be carried out and shall indicate that the complete dynamic system is free fromharmful torsional resonances resulting from propeller/ice interaction.

16 Miscellaneous machinery requirements

16.1 Starting arrangements

16.1.1 The capacity of the air receivers shall be according to the requirements in Pt.4 Ch.6 Sec.5 [9].If the air receivers serve any other purposes than starting the propulsion engine, they shall have additionalcapacity sufficient for these purposes.The capacity of the air compressors shall be sufficient for charging the air receivers from atmospheric tofull pressure in one (1) hour, except for a ship with the ice class Ice(1A*) if its propulsion engine has to bereversed for going astern, in which case the compressors shall be able to charge the receivers in half an hour.

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16.2 Sea inlet and cooling water systems

16.2.1 The cooling water system shall be designed to ensure supply of cooling water when navigating in ice.The sea cooling water inlet and discharge for main and auxiliary engines shall be so arranged that blockageof strums and strainers is prevented. For this purpose at least one cooling water inlet chest shall be arranged as follows:

1) The sea inlet shall be situated near the centre line of the ship and well aft if possible. The inlet grids shallbe specially strengthened.

2) As a guidance for design the volume of the chest shall be about one cubic metre for every 750 kWengine output of the ship including the output of the auxiliary engines necessary for the ship's service.

3) To allow for ice accumulation above the pump suction the height of the sea chest shall not be less than:

where:

Vs = Volume of sea chest according to item 2.

The suction pipe inlet shall be located not higher than hmin/3 from top of sea chest.4) A pipe for discharge cooling water, allowing full capacity discharge, shall be connected to the chest.

Where the sea chest volume and height specified in 2 and 3 are not complied with, the discharge shallbe connected to both sea chests. At least one of the fire pumps shall be connected to this sea chest or toanother sea chest with de-icing arrangements.

5) The area of the strum holes shall be not less than four (4) times the inlet pipe sectional area.

If there are difficulties in meeting the requirements of 2) and 3) above, two smaller chests may be arrangedfor alternating intake and discharge of cooling water. The arrangement and situation otherwise shall be asabove.Heating coils may be installed in the upper part of the chest or chests.Arrangements using ballast water for cooling purposes may be useful as a reserve in ballast condition butcannot be accepted as a substitute for sea inlet chests as described above.

16.3 Ballast system

16.3.1 An arrangement to prevent freezing of the ballast water shall be provided for inside ballast tankslocated fully or partly above the LIWL, adjacent to the ship's shell, and which need to be filled for operationin ice conditions according to [1.5.4]. For this purpose the following ambient temperatures shall be taken asdesign conditions:

— sea water temperature: 0°C— air temperature: –10°C.

Necessary calculations shall be submitted.

16.3.2 When a tank is situated partly above the LIWL, an air-bubbling arrangement or a vertical heating coil,capable of maintaining an open hole in the ice layer, will normally be accepted.The required heat-balance calculations may then be omitted.

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Guidance note:It is assumed that, before pumping of ballast water is commenced, proper functioning of level gauging arrangements is verifiedand air pipes are checked for possible blockage by ice.


17 Guidelines for strength analysis of the propeller blade usingfinite element methodSee App.A for guidelines on strength analysis of the propeller blade using finite element method.

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SECTION 3 OPERATIONS IN COLD CLIMATE - WINTERIZED

1 General

1.1 IntroductionThe additional class notation Winterized establishes requirements for ensuring that a ship is capable ofbeing suitably prepared for operations in low temperatures. This is provided for by setting requirements forimportant shipboard functions, systems and equipment intended to be in operation in the specified designenvironmental conditions. The design environmental conditions include cold air, cold sea water and wind.

1.2 ScopeThe scope for additional class notation Winterized specifies functions, systems and equipment essentialfor safety of the ship, personnel and the environment, operating in adverse cold climate conditions. Suchconditions include; freezing sea spray, atmospheric icing, wind chill factor, and the properties of materialsin cold temperatures. Winterization measures encompass: protection of important shipboard functions,systems and equipment, provisioning suitable equipment and supplies, and implementing procedures for safeoperation and personnel welfare. Other functions, such as systems and equipment important for commercialoperations may also be affected by cold climate and can benefit from winterization measures. However, thewinterized notation does not address these issues where they are not essential to safety; nor do they addressthose hull and machinery requirements necessary for safe navigation through sea ice, which is addressed inthe ice class rules.

1.3 ApplicationThe additional class notation Winterized applies to ships constructed and equipped, surveyed and tested inaccordance with the rules of this section and may be assigned the class notation Winterized with relevantqualifiers defined in Table 1. One, and only one, of the qualifiers Basic, Cold or Polar, is mandatory. Thequalifier td is mandatory for Cold or Polar and is optional for Basic. The qualifier Enhanced is optional andcan be selected together with Basic or Cold. The qualifier Enhanced may be assigned to a ship that fulfilsadditional requirements at a higher level of winterization. For example, a ship that fulfils all requirementsfor qualifier Basic and several additional elements from Cold may be assigned the qualifier Enhanced. Thespecific enhancements will be listed in the appendix to the ship's classification certificate.

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1.4 Class notationsShips built in compliance with the requirements as specified in Table 1 will be assigned the additional notationrelated to structural strength and integrity as follows:



Basic Occasional operation in coldclimate for short periods

Cold Regular operation in coldclimate or for an extendedperiod of time

Polar Operation in extreme coldclimate of the polar regionsyear-round

td Design temperature

Winterized

Mandatory:

No


[5] and [6]

FiS requirements:

Pt.7 Ch.1 Sec.2, Pt.7Ch.1 Sec.3 and Pt.7 Ch.1Sec.4

Enhanced Additional requirements of ahigher level of winterization

1.4.1 Use of qualifiersOne and only one of the qualifiers Basic, Cold or Polar, is mandatory.The qualifier td is mandatory for Cold or Polar; it is optional for Basic.The qualifier Enhanced is optional and can be selected together with Basic or Cold.

1.4.2 Qualifier Enhanced may be assigned to a ship that fulfils additional requirements of a higher levelof winterization. For example, a ship that fulfils all requirements for qualifier Basic and several additionalelements from Cold may receive the qualifier Enhanced. The specific enhancements will be listed in theappendix to the ship’s classification certificate.

Guidance note:This feature is meant to recognize and document additional winterization enhancements of a ship and include them in surveyprocess, as particular winterization features are of increasing importance to ship owners, charterers and vetting agents.


1.4.3 Syntax of class notation and qualifiersOrder of appearance: 1 Winterized, 2 Basic, Cold or Polar, 3 t and 4 Enhanced.td shall be indicated in °C.Qualifiers shall be surrounded by parentheses.

Examples: Winterized(Basic)

Winterized (Cold, -20°C)

Winterized (Cold, -20°C, Enhanced).

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1.5 Definitions1.5.1 Terminology and definitions

Table 2 Terminology and definitions

Term Definition

active measures winterization measures that rely primarily on energy to address the adverse effects of icing,freezing or wind chill; e.g., heat, physical force and circulation of liquids

anti-icing measures to prevent ice from forming on surfaces, structures or equipmentThe intent of anti-icing is that the surfaces, structures or equipment are immediatelyavailable.

de-icing measures to remove snow and ice accumulations from surfaces, structures or equipmentThe intent of de-icing is that the surfaces, structures or equipment can be made availablewithin a reasonable amount of time.

design environmentalconditions

environmental conditions for which the ship is designed to operateFor winterization, the key design environmental conditions are air temperature, sea watertemperature and wind speed.

design temperature(td) reference air temperature used as a criterion for the selection, testing and use of materialsand equipment for low temperature service

F.P. the forward perpendicular is the perpendicular at the intersection of the summer loadwaterline with the fore side of the stemFor ships with unusual bow arrangements the position of the F.P. will be especiallyconsidered.

functional requirement requirements that provide the fundamental rationale behind a particular rule

main functions the main functions of a ship in the context of class as defined in Pt.1 Ch.1 Sec.1 [1.22]

passive measures winterization measures that do not rely primarily on energy to address the adverse effectsof icing, freezing or wind chill; e.g., shielding, enclosures, insulation and building-in areasor equipment

performance requirement requirements that explain in greater detail the type of performance a winterization measureshall achieve in order to fulfil the intent of the functional requirement

sea spray icing icing caused by the freezing of sea spray on ship surfaces, structures and equipment

winterization measures taken to ensure a ship is capable of and suitably prepared for operations in lowtemperaturesWinterization is primarily focused on the adverse effects and control of freezing, icing, windchill and material properties in cold temperature.

1.5.2 Reference to other documentsDocuments referenced in this section are listed in Table 3.

Table 3 Reference to other documents

Document code Title

CSA Standard C22.2 No. 0.3 Test methods for electrical wires and cables

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Document code Title

IEC 60945 Maritime navigation and radio communication equipment and systems – Generalrequirements – Methods of testing and required test results

IMO Res. A.1024(26) Guidelines for ships operating in polar waters

IMO Res. MSC/81(70) Revised recommendation on testing of life-saving appliances

ISO 3434 Ships and marine technology – Heated glass panes for ships’ rectangular windows

ISO 8863 Ship’s wheelhouse windows – Heating by hot air of glass panes

ISO 17899 Ships and marine technology – Marine electric window wipers

LSA Code International life-saving appliances code

MARPOL Annex I Regulations for the prevention of pollution by oil

SOLAS Chapter IV Radio communications

IS Code International code on intact stability

2 Documentation

2.1 Documentation requirementsFor general requirements to documentation, including definition of the Info codes, see Pt.1 Ch.3 Sec.2.For a full definition of the documentation types, see Pt.1 Ch.3 Sec.3.Documentation shall be submitted as required by Table 4.

Table 4 Documentation requirements

Object Documentation type Additional description Info Qualifier

Accommodationheating system

S120 - Heat balancecalculation

Indicating the heating consumption based on anexternal ambient temperature of 20°C below thedesign temperature (td).

AP ColdPolar

S010 - Piping diagram(PD)

Anti-freezing arrangement. APBallast tanks


Indicating anti-freezing capacity required for tankslocated fully or partly above the water line or lowerice water line (LIWL), whichever is lower.

FI

Cables Z262 - Report from testat manufacturer

To at least 10°C colder than the design temperature(td).

FI ColdPolar

Cargo hatches andservice hatches

H080 - Strengthanalysis

Under conditions of snow and ice loading. FI ColdPolar

Emergency electricpower generationarrangement



AP ColdPolar

Escape routes G120 - Escape routedrawing

Including anti-icing protection. AP

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Externalcommunicationssystems

Z262 - Report from testat manufacturer

To the design temperature (td), where td is colderthan -25°C.

FI

S011 - Piping andinstrumentationdiagram (P&ID)

Indicating anti-freezing arrangement, includingdrains (for self-draining systems), heat tracing andinsulation.

APFire-fightingsystems


Indicating anti-freezing capacity required. FI

S010 - Piping diagram(PD)

Indicating anti-freezing arrangement. APFresh water tanks


Indicating anti-freezing capacity required. FI

Helicopter deck H080 - Strengthanalysis

Under conditions of snow and ice loading. FI

Machinery spacesheating system



AP ColdPolar

Main electric powergeneration

E040 - Electrical loadbalance

Including winterization systems as a separate mode. AP

Navigation lights Z262 - Report from testat manufacturer

To -25°C or the design temperature (td), whichever iscolder.

FI

Navigation systems Z262 - Report from testat manufacturer


FI

Navigation bridge Z030 - Arrangementplan

Including anti-icing arrangement to bridge windows,wipers and washers.

AP

Oil pollutionprevention

Z265 - Calculationreport

Accidental oil outflow performance in accordance withMARPOL Annex I Reg. 23.

FI Polar

Propulsionand steeringarrangements

Z100 - Specification Stern tube and controllable pitch propeller oils. AP Polar

Radar systems Z262 - Report from testat manufacturer


FI

Rescue boatarrangements

G160 - Life-savingarrangement plan


B030 - Internalwatertight integrityplan

FI

B070 - Preliminarydamage stabilitycalculation

AP

Stability

B130 - Final damagestability calculation

AP

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Steam and thermaloil system

S030 - Capacityanalysis

Indicating boiler capacity required for supplying anti-icing, anti-freezing and de-icing arrangements.

FI

Survival craftarrangements

G160 - Life-savingarrangement plan


Z051 - Design basis Including description of the overall winterizationdesign arrangement, indicating how each applicableitem in the notation has been addressed in thewinterization design.

FI

E050 - Single linediagrams/consumer listfor switchboards

For anti-icing and anti-freezing systems, including:full load; cable types and cross sections; make,type and rating of fuses, switching gear and heatingcables.

AP

E170 - Electricalschematic drawing

For anti-icing and anti-freezing systems, including:control and instrumentation circuits, including make,type and rating of all equipment.

AP


For anti-icing and anti-freezing systems, indicatingheating capacities required and provided.

FI

Z030 - Arrangementplan

Including anti-icing, anti-freezing and de-icingsystems; heating capacity for each area; fasteningarrangement and spacing of electrical cables and fluidpipes; and installation protection details of electricalcables.

AP

Z253 - Test procedurefor quay and sea trial

Including anti-icing, anti-freezing and de-icingsystems.

AP

Winterizationarrangements

Z161 - Operationmanual

Including:

— cold climate operations and planning: cold climatehazards, icing prediction, meteorological and routeplanning, ship-hand-ling in icing conditions;

— winterization preparations and procedures:general precautionary measures; description,location and operating procedures for installedwinterization features; system-specificwinterization measures; de-icing procedures;

— procedures for special operations in cold climate:ballasting, cargo operations, mooring, anchoring,and other relevant operations for ship type;

— personnel protection; and— cold climate operation checklists: winterization

preparations; routine winterization checks;additional actions for special operations in coldclimate.

AP


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3 Certification

3.1 Certification requirementsFor a definition of the certificate types see Pt.1 Ch.3 Sec.5

3.1.1 Products shall be certified as required by Table 5.

Table 5 Certification requirements

Object Certificatetype

Issued by Certification standard* Additional description

Lifeboat PC Manufacturer Including stowage down to −30°C or 20°Ccolder than the design temperature (td),whichever is colder; and operation to −15°C orthe design temperature (td), whichever is colder.

Life raft PC Manufacturer Including stowage down to −30°C or 20°Ccolder than the design temperature (td),whichever is colder; and operation to −15°C orthe design temperature (td), whichever is colder.

* Unless otherwise specified the certification standard is the rules.

4 Design environmental conditions

4.1 General

4.1.1 The design temperature (td) value shall be specified in degrees Celsius. Where the ship has also theclass notation DAT(t), the design temperature for the two notations shall be the same.Typical environmental conditions for qualifiers Basic, Cold and Polar are listed in Table 6. The values arerepresentative but not necessarily prescriptive.

Table 6 Typical design environmental conditions

Qualifier Air temperature (td) Sea water temperature Wind speed

Basic ≤ −10°C

(−10°C is default)

+4°C without ice class−2°C with ice class 20 m/s

Cold−15°C to −30°C

+2°C without ice class−2°C with ice class

20 m/s

Polar < −25°C −2°C 20 m/s

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Guidance note:td should reflect the lowest mean daily average air temperature in the area of operation, where

mean = statistical mean over the observation period (at least 20 years)

daily average = average during a 24-hour period

lowest = lowest during a year.

For seasonally restricted service, the lowest value during the period of operation applies.For ships with ice class, the design sea water temperature is the freezing point of sea water. As the freezing point varies withsalinity (from −2°C in normal sea water to 0°C in fresh water), this should be taken into consideration where appropriate whenmaking calculations in connection with the notation.


4.1.2 Specific requirements for winterized notation are listed in Table 7. In the table, items marked with an Xare applicable for the relevant qualifier.

4.1.3 Required additional class notationsFor qualifier Basic, class notation DAT(t) is mandatory if td < −20°C.For qualifier Cold, either class notation DAT(t) or PC is mandatory.For qualifier Polar, an ice class notation PC, class notation Clean, and either class notation DAT(t) or PCare mandatory.

4.1.4 Functional, performance and prescriptive requirementsThe notation adopts a three-tiered approach. First, winterization requirements are based upon fulfilling thestated functional requirements. The functional requirements provide the fundamental rationale and intentbehind a particular rule.Second, some functional requirements are supported by one or more performance requirements. Theseexplain in greater detail the type of performance a winterization measure shall achieve in order to fulfill theintent of the functional requirement, either in part or in whole.Third, functional and performance requirements are supported by prescriptive rules and guidance notes.These provide a set of generally acceptable solutions to meet the functional and performance requirements,either in part or in whole.

4.1.5 Prescriptive requirements do not preclude the use of other alternative solutions. Such solutions will beconsidered by their ability to fulfill the relevant functional and performance requirements.

4.1.6 Equipment not otherwise mentioned in these rules and which in the opinion of the Society is essentialfor safety shall function properly in the design environmental conditions. Such equipment shall be providedwith anti-icing and anti-freezing protection as appropriate, and shall be constructed of material appropriatefor the design temperature (td). Equipment material shall be selected according to C1001 in Table 7, asappropriate.

5 General requirements

5.1 Anti-icing and anti-freezing measures

5.1.1 Winterization measures required by Table 7 shall fulfil the functional requirements, and shall beconsidered for approval in each case.

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5.1.2 Where anti-icing and anti-freezing measures are required for areas and equipment in Table 7, thefollowing are examples of acceptable solutions:Equipment and areas that require anti-icing measures should as far as possible be situated in protectedlocations, so that sea spray cannot reach it. This may be accomplished by using fully enclosed spaces, semi-enclosures, recesses with removable curtains in front, or similar. A shielded location will be the simplest andmost reliable solution for anti-icing wherever it is possible.Heating of spaces may be necessary depending on the type of equipment located therein.Hard removable covers may also be applicable for some types of equipment. Cover by canvas may beacceptable for some types of equipment, like fire monitors. Supply of heated air may be an alternative if theequipment in question is enclosed under a cover, hard cover or canvas.The use of electric heating blankets or heat tracing can be a solution for protection of equipment on opendeck.

Guidance note:At higher levels of winterization, preference is given to passive measures for anti-icing/anti-freezing protection (such asenclosures) versus de-icing or active measures for anti-icing/anti-freezing protection (such as heat tracing). Passive measures areinherently more effective, more efficient, and contribute to reducing emissions to the environment.


5.1.3 The heating capacity for anti-icing and anti-freezing arrangements shall be sufficient to prevent icing orfreezing under the design environmental conditions. Anti-icing and anti-freezing arrangements shall be ableto maintain a surface temperature of at least +3°C under the design environmental conditions.

5.1.4 In anti-icing and anti-freezing arrangements using heating, special attention shall be paid to theheat transfer from the heating cables or pipes to the equipment or structure to be heated. The spacingand fastening of heating cables or pipes shall be appropriate for efficient heating to keep the equipment orstructure ice-free under the design environmental conditions. Appropriate spacing shall be established byheat balance calculations.

5.1.5 For anti-icing and de-icing arrangements applying heating by fluids in pipes, the installation shallensure that the heating fluid maintains its heating effectiveness under the design environmental conditions.The appropriate amount of insulation and the rate of circulation shall be established by heat balancecalculations.

5.1.6 Where heated fluids are used for winterization purposes, their process plants shall have sufficientcapacity to simultaneously supply all normal consumers and the winterization systems under the designenvironmental condition.

5.2 De-icing measures

5.2.1 Where removal of ice prior to taking equipment into use is acceptable, de-icing may be carried out byfixed heating arrangements or by use of portable equipment.Portable equipment may consist of:

— hoses for steam blowing— hoses for heated water flushing— mallets (wooden, rubber or plastic hammers)— snow blowers— shovels.

Guidance note:Mallets should be made of wood, not metal, to avoid damage to equipment, structures and paintwork.


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5.2.2 Steam or hot water shall be available where an area or equipment is intended to be de-iced manuallyand fixed heating is not provided. The location and number of the steam/hot water outlets and equipmentshall be appropriate to the local layout and to the time scale in which the de-icing is required to be achieved.

5.2.3 De-icing equipment shall be located in areas where it is readily available and protected from icingand other adverse conditions. It is preferable to store de-icing equipment inside the ship. Where it is storedoutside, the storage facilities shall be afforded anti-icing protection to ensure it is readily accessible.

5.2.4 Steam- or water-based de-icing equipment shall be stored in heated spaces or containers that are keptabove freezing temperature in the design environmental condition to prevent hoses from freezing.

5.2.5 Any equipment or systems scheduled for de-icing shall have all susceptible components (e.g., sensors,counters, limit switches, electric fittings) adequately protected from mechanical damage from manual de-icing activities or water ingress from water/steam de-icing.

6 Requirements to winterization

6.1 Requirements to winterization

6.1.1 Winterization measures required by Table 7 shall fulfill the functional requirements, and shall beconsidered for approval in each case, in addition to those given for the assignment of main class. Therequirements relevant for Winterized Basic, Cold and Polar are indicated by an X in the correspondingcolumn of the table.

Table 7 Requirements for winterized notation

Item Object Basic Cold Polar Rule

C200 Stability, watertightand weathertightintegrity

C201 Cargo hatches,service hatches andshell doors

X X Functional requirements:

— Cargo hatches, service hatches and shell doors shall maintainweather-tightness under the design environmental conditions.

— Cargo hatches and service hatches shall maintain theirstructural integrity and weather-tightness under the additionalloading of snow and ice accumulation.

Performance requirements:

— Hatch/door seals and other components relevant for safetyshall be made from materials suitable for the designtemperature (td) specified in the class notation.

Prescriptive requirements:

— Snow and ice loading calculations in this requirement shalluse the same snow and ice loads as those used for stabilitycalculations in C203.

— Where not addressed by Sec.4 for DAT or Sec.5 for PC iceclass notation, materials shall be selected according to C1001,as appropriate.

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C202 Freeing ports andscuppers

X X X Functional requirements:

— Freeing ports, scuppers and drains shall be capable ofbeing kept clear and open under the design environmentalconditions, and not be blocked due to snow, ice or freezingwater.


— Where decks, access ways and muster areas are requiredto be kept ice-free, they shall be arranged with drains andscuppers that have anti-freezing protection.

— Freeing ports shall be fitted with anti-icing protection.— Increasing the freeing port area by 30% is accepted as an

alternative to heating (see Pt.3 Ch.12 Sec.10).— If a shutter is fitted on the freeing port, it shall be provided

with heating sufficient for maintaining its opening ability.— For ships 100 m or less in length, shutters shall not be fitted in

the freeing ports, as per the IS Code, Sec. 6.4.1.

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C203 Stability X X X Functional requirements:

— The ship shall retain adequate stability under conditions oficing under the design environmental conditions.


— The ship shall satisfy the applicable intact and damage stabilityrequirements under conditions of icing, taking into account theadditional weights due to ice accretion.

— Where there are no other damage stability requirementsapplicable for the ship, the ship shall comply with the damagestability requirements of IMO Res. A.1024(26).


— The icing weight distribution shall be calculated from thefollowing:

— For decks, gangways, wheelhouse tops and other horizontalsurfaces, the values found in Table C203

— For projected lateral area of each side of the ship above thewater plane; 7.5 kg/m2;

— The projected lateral area of discontinuous surfaces of rail,sundry booms, spars (except masts) and rigging of shipshaving no sails and the projected lateral area of other smallobjects shall be computed by increasing the total projectedarea of continuous surfaces by 5% and the static momentsof this area by 10%.

C300 Mechanical

C301 Anchor emergencyrelease safetysystem (offshoreservice vessels)


— The anchor emergency disconnect system on offshore servicevessels with anchor handling capability shall be usable in thedesign environmental conditions.


— The anchor emergency disconnect system shall be providedanti-icing protection.

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C302 Anchoringarrangement


— The anchoring system shall be readily available in the designenvironmental conditions when in or approaching coastal orpiloting waters.

— The control systems shall not be susceptible to damage by de-icing methods.

— Associated hydraulic systems shall function under the designenvironmental conditions


— The anchor windlass and windlass controls shall be providedanti-icing protection.

— The anchor chain may be de-iced manually.— The hawse pipe shall be provided anti-icing protection or de-

icing protection with steam or hot water.— Associated hydraulic systems shall comply with the

requirements in C805.

C303 Anchoringarrangement


— The crew shall be able to easily access and operate the anchorwindlass in an environment that protects them from wind,water spray, ice and slippery conditions, without the need toremove ice from equipment or decks.


— Anchor windlass, windlass controls and chain stopper shallbe located inside a deckhouse, a semi-enclosure providingprotection from water spray or inside a forecastle space.

C304 Anchoringarrangement –Material quality


— The anchor chain, chain stopper and anchor windlass shall bemade from materials suitable for the design temperature (td).


— The anchor chain material quality shall be chosen as follows:

if td > -20°C, then chain type K2 or K3

if td ≤ -20°C, then chain type K3— For anchor windlass components fabricated from plate

material, class III steel grades shall be selected according toSec.4 [2].

— For equipment or parts of equipment fabricated from forgedor cast material, the impact test temperature and energy shallfulfil the requirements in C1001.

— The anchor windlass shall have foundation bolts and shaftbearing holding bolts made from low temperature steel. Greycast iron shall not be used in any load bearing parts.

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C305 Cranes X X Functional requirements:

— Cranes shall be able to withstand icing loads withoutcollapsing.


— Cranes shall be able to withstand icing loads used in C203 orin Pt.3 Ch.11 Sec.2 [4.5], whichever is greater.

— Cranes shall be able to withstand icing loads in the stowed andoperating conditions.

— Crane foundations and supports shall be able to support aniced crane, using the loads specified above.

C306 Cranes X X Functional requirements:

— Cranes that are required for essential safety functions (e.g.,crane used for launching the rescue boat) shall operate in thedesign environmental conditions.

Performance requirements

— The relevant cranes shall be made from materials suitable forthe design temperature (td).


— Equipment material shall be selected according to C1001, asappropriate.

— The relevant cranes shall be fitted with anti-icing protection.

Guidance note:

1) Icing protection may either be active (e.g., heating) orpassive (e.g., shielding).


C307 Emergency towingarrangement(tankers)

X Functional requirements:

— It shall be possible for tankers to make the emergency towingarrangement available on short notice during operation andsailing in the design environmental conditions.

— The emergency towing arrangement shall operate under thedesign environmental conditions.


— The emergency towing arrangement pre-rigged for immediateuse shall have anti-icing protection.

— The other emergency towing arrangement may be arrangedwith either anti-icing or de-icing protection.

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C308 Emergency towingarrangement(tankers)


— It shall be possible to make the emergency towingarrangement available on short notice during operation andsailing in the design environmental conditions.

— The emergency towing arrangements shall operate under thedesign environmental conditions.


— Components exposed to the low temperature shall be madefrom materials suitable for the design temperature (td)specified in the class notation.


— The emergency towing arrangement pre-rigged for immediateuse shall have passive anti-icing protection, that is, it shall belocated in an enclosed space, semi-enclosure or under deckspace.

— The other emergency towing arrangement may be arrangedwith either anti-icing or de-icing protection.

— Equipment material shall be selected according to C1001, asappropriate.

C309 Engine rooms –restart from deadship


— It shall be possible to re-start the main machinery froma dead-ship condition after 30 minutes under the designenvironmental conditions.


— The machinery shall be arranged such that it can re-start andoperate from a dead-ship condition after 30 minutes at anoutside ambient temperature 20°C colder than the designtemperature (td).

1) Guidance note:

1) Insulation may be necessary to ensure the machineryspace maintains a sufficiently warm environment for re-starting the machinery after a dead-ship condition of 30minutes.

2) Machinery may require air intake heating, cooling waterheating and lube oil heating, depending on individualmachinery specifications, to ensure it can re-start froma dead-ship condition after 30 minutes.

3) Water cooling lines and other machinery componentsthat are subject to freezing should be located away fromship sides, where they will get coldest first.


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C310 Mooringarrangement


— Crew shall be able to safely and efficiently remove snow andice accumulation from mooring winches and the surroundingwork area to make operating them safe in a reasonable timeprior to mooring.


— De-icing system shall be provided in the vicinity of themooring winches.

— Mooring winches shall be provided with covers to protect themfrom icing.

C311 Mooringarrangement


— Mooring equipment exposed to the low temperature shall bemade from materials suitable for the design temperature (td)specified in the class notation.


— Equipment material shall be selected according to C1001, asappropriate.Mooring winches shall have foundation bolts andshaft bearing holding bolts made from low temperature steel.Grey cast iron shall not be used in any load bearing parts.

— Mooring wires shall be lubricated with low temperature wirerope dressing appropriate for the design temperature (td).

Guidance note:Mooring equipment includes bollards, chocks, fairleads and rollerpedestal (e.g. body and seat of fairleads and bollards; roller, pin,boss, bush, seat of deck stand rollers); body of sunken bits; chainwheel, gear wheel, shaft, foundation bolt, drum, warping head onan anchor windlass; and mooring wires.


C400 Electrical

C401 Cables X X Functional requirements:

— Electrical cabling shall maintain its required performance underthe design environmental conditions.


— Electric cables exposed to the low temperature shall be madefrom material suitable for the design temperature (td).


— Cables shall comply with acceptable impact and bending teststandards. Impact and bending tests shall be conducted to atleast 10°C colder than the design temperature (td).

Guidance note:The latest revision of Canadian CSA standard C22.2 No. 0.3 forimpact test at –35°C and bending test at –40°C, is an acceptabletest standard.


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C402 Electric motorcooling


— Electric motors on open deck and necessary for safety or forsupporting main functions shall be capable of operation underthe design environmental conditions.


— Snow, ice and cold temperatures shall not adversely affectthe motor’s cooling system and thereby render the motorinoperable.


— Electric motors in the category above shall be naturally cooled,without external fan.

C403 Emergency electricpower generationarrangement


— Emergency generators shall be operable under the designenvironmental conditions.


— Emergency generator shall be able to start and operate withan outside ambient air temperature of 20°C below the designtemperature (td).


— Space heating, or heating of the generator itself, is required toensure the emergency generator will start and operate undercold conditions, unless it can be shown that it will start andoperate in temperatures 20°C below the design temperature(td).

C404 Emergency electricpower generationarrangement


— The emergency generator starting system shall be arranged soas to avoid a common mode failure, particularly one related tocold temperatures.


— The emergency generator shall have two different, separateand independent starting systems.

Guidance note:The reference to different starting systems means that the twosystems are based on different principles (e.g., one battery-powered and one air-powered), so as to avoid a common modefailure, particularly one related to cold temperatures.


C405 Lighting X X X Functional requirements:

— Deck lighting should be operable under the designenvironmental conditions.


— Deck lights that do not generate sufficient heating to stayice-free shall be fitted with additional heating to make themoperational.

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C406 Main electricpower generationarrangement


— Main electric generator capacity shall be sufficient to operateessential ship systems including anti-icing systems fitted tocomply with the notation, under the design environmentalcondition, and a minimum of half of the de-icing systems fittedto comply with the notation.

Prescriptive requirement

— For calculation of required electric generator capacity (see Pt.4Ch.8), the power requirements for the heating arrangementsshall be included as follows:

— 100% of electric power needed for anti-icing and anti-freezing purposes fitted to comply with the notation

— 50% of electrical power needed for de-icing purposes fittedto comply with the notation, or 100% of the power for thesingle largest de-icing system consumer fitted to complywith the notation, whichever is greatest.

— Calculations shall be based upon power demands under thedesign environmental condition.

C407 Main electricpower generationarrangement


— Sufficient main electricity power generation shall be availablesuch that a casualty to any one engine room (e.g., from fireor flooding) will not endanger the electric power generationcapacity such that the ship is inoperable or crew survivability isput at risk.


— Main electric power generators shall be located in separatespaces so that a casualty affecting one space (e.g., from fire orflooding) does not affect the other.

— The ship shall have sufficient capacity to power essentialsystems for operation and survivability with the loss of any oneengine space.

— Auxiliary systems required to operate the main electric powergenerators shall also be separate and independent, to reducecommon fault failures.

Guidance note:The redundancy requirement applies to electric power generationcapacity, not to propulsion capacity.


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C408 Main switchboards X X X Functional requirements:

— Switchboards shall be arranged such that the crew canadequately control and monitor the performance of installedwinterization systems.


— Switchboard for winterization systems shall be arrangedas required for distribution switchboards. A wattmeter orampere meter, indicating the total load shall be installed onthe switchboard. Marking on the switchboard shall state theload on each circuit, as well as the total load.

C409 Protective earthingarrangements


— Electrical circuits for winterization features shall be arrangedsuch that an earthed circuit may be automatically isolated anddisconnected without disabling the rest of the system.


— All electrical circuits for winterization features shall have earthfailure monitoring with automatic disconnection and alarmconnected to the main alarm system.

C500 Safety

C501 Access, external X X X Functional requirements:

— Personnel should be able to move safely up and downthe accommodation ladder and gangway in the designenvironmental conditions, including freezing precipitation(snow and ice).


— The ship shall have de-icing protection for the accommodationladder and gangway.

C502 Access, internal X X X Functional requirements:

— Personnel safety: The personnel should be able to movesafely about weather deck areas of the ship under the designenvironmental conditions.

— Stability: Snow and ice accumulation on weather decks shallbe controlled within ship stability limits.


— The ship shall have de-icing protection to remove snow and iceaccumulation from all weather deck areas where there are noother requirements for anti-icing protection, to prevent loss ofstability and to make them safe for personnel.

— Some areas of weather decks may need to be ice-free, e.g.when those areas are important for emergency access (e.g.,escape routes, muster areas, embarkation areas to survivalcraft); these areas shall be provided anti-icing protection.

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C503 Access, internal X X X Functional requirements:

— People shall not be at risk of injury, nor essential safetyequipment/structures at risk of damage, caused by falling icefrom elevated structures, including but not limited to cranes,derricks, masts and overhanging decks.


— Elevated structures shall be provided with de-icing or othermeasures adequate to prevent personnel injury or damage toessential safety equipment/structures from falling ice.

Guidance note:Possible measures to prevent injury or damage from fallingice include: locating elevated structures to avoid or minimizeicing; locating work areas and equipment away from elevatedstructures to eliminate or minimize risk from falling ice; designand/or locate elevated structures such that they can be easilyde-iced; anti-icing measures (enclosure, shielded location, orheat tracing); design measures to reduce icing potential (box vs.lattice structure); dropped object protection to protect people,equipment and structures from falling ice.


C504 Access, internal(tankers)


— Personnel shall have safe access to bow (for tankers) underthe design environmental conditions.


— Safe access to tanker bow shall be provided by a gangwayraised to a sufficient height to prevent passage being impededby snow build-up on underlying surfaces.

— The safe access to tanker bow shall be provided de-icingprotection.

C505 Access, internal(tankers)


— Personnel shall have safe access to bow (for tankers) underthe design environmental conditions.


— The safe access to bow gangway shall either be provided anti-icing protection, or it shall be made of a grating with raisednon-skid points that will give safe footing in the presence ofminor sea spray icing.

Guidance note:Anti-icing protection may be in the form of an under-deckpassageway, on deck trunk, or heat tracing.


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C506 Accommodationheating system


— Accommodation spaces shall be kept at a temperature thatensures the health and safety of personnel under the designenvironmental conditions.


— Accommodation heating shall be dimensioned to ensureaccommodation spaces can be kept at a temperature of atleast +18°C under the design environmental conditions, with arecirculation rate of 50%.

— The heating consumption shall be calculated based on anexternal ambient temperature of 20°C below the designtemperature (td).

C507 Accommodationheating system


— Accommodation spaces shall be kept at a temperature thatensures the health and safety of personnel under the designenvironmental conditions.


— The accommodation and spaces essential to ship operationshall have a redundant space heating design such that afailure of one heating source will not render the spaces withoutheating.

C508 Emergencyshutdown system


— Emergency shutdown (ESD) valves for gas tankers shallbe ice-free and operational at all times in the designenvironmental conditions.


— ESD valves shall be arranged with anti-icing protection.

C509 Escape routes X X X Functional requirements:

— Escape exits and escape doors shall be able to readily openand close under the design environmental conditions, includingfreezing precipitation (snow and ice) and sea-spray icing.

— Escape ways shall be safe to use in an emergency under thedesign environmental conditions.


— Escape exits and doors shall have anti-icing protection.— Escape ways shall have anti-icing protection providing a

minimum ice free width of 700 mm, enabling the use of atleast one railing.

C510 Escape routes X Functional requirements:

— Escape routes shall be dimensioned so as not to hinderpassage for persons wearing suitable polar clothing, to complywith IMO Res. A.1024(26), Sec. 4.3.2.

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C511 Fire extinguishingequipment, mobile


— Miscellaneous fire-fighting equipment (including but not limitedto portable fire extinguishers, fire blankets, etc.) shall bereadily available under the design environmental conditions.


— Portable fire extinguishers in open or unheated spaces shall berated for operation at the design temperature (td).

— Miscellaneous fire-fighting equipment shall be located in areaswhere it is readily available and protected from icing and otheradverse conditions. The storage facilities shall be affordedanti-icing protection to ensure it is readily accessible.

C512 Fire-fightingsystems


— Fire-fighting systems shall be readily available under thedesign environmental conditions.


— Fire-fighting equipment (including but not limited to hydrants,hoses, nozzles and monitors) shall not be blocked by externalicing or by internal freezing under the design environmentalconditions.

— Fire mains and fire-fighting system piping shall not beblocked by internal freezing under the design environmentalconditions.


— Fire-fighting equipment shall have anti-icing and anti-freezingprotection.

— Fire mains and fire-fighting system piping shall have anti-freezing protection.

— Anti-freezing protection of the fire mains and fire-fightingsystem piping may be achieved by locating them in a heatedpassageway, by providing them with heat tracing, or byarranging them as a dry, self-draining system. Where piping isarranged as a dry, self-draining system, drains shall be locatedat the lowest points in the system, and the piping layout shallensure all water will drain to them without being trapped in U-bends, low points or dead-ends.

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C513 Fire-fightingsystems


— Fire-fighting systems equipment shall be readily availableunder the design environmental conditions.


— The choice of fire-fighting systems and extinguishing agentsshall be appropriate for the design environmental conditions,taking into account low temperature effects on extinguishingagents.

— Isolation valves shall be fitted and readily available under thedesign environmental conditions.


— Fire extinguishing agents (foams, powders, gases) shall berated for operation at the design temperature (td).

— Isolation valves shall have anti-icing protection.— The isolation valve spindle shall be accessible from weather

deck.

C514 Fire and gasdetection and alarmsystems


— Fire and gas detection and alarm systems shall function underthe design environmental condition and shall not be obstructedby ice or snow.


— Fire and gas detection sensors and dampers located outsideshall be provided anti-icing protection.

— Fire and gas detection sensors located outside or in unheatedspaces shall be rated for operation at the design temperature(td).

C515 Guard rails X X X Functional requirements:

— Personnel safety: Icing of railings shall be controlled so thatrailings can maintain their safety function.


— Railings that are important as hand-holds (stairs, escapeways) shall have anti-icing protection.

— Railings that function only as barriers, but are not intended ashand-holds, can be arranged for de-icing

C516 Helicopter safetyarrangements


— The helicopter winching area and helicopter deck, where fitted,shall be safe for personnel and helicopter operations under thedesign environmental conditions.


— De-icing arrangements shall be provided for the helicopterwinching area and helicopter deck, where fitted.

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C517 Helicopter safetyarrangements(standby vessels)


— For standby vessels, the helicopter winching area andhelicopter deck shall be readily available and safe forpersonnel and helicopter operations under the designenvironmental conditions.


— For standby vessels, de-icing arrangements shall be providedfor the helicopter winching zone and helicopter deck, wherefitted, capable of making the zone/deck available within onehour under the design environmental conditions.

C518 Immersion suits X X Functional requirements:

— Immersion suits shall be provided and afford the wearer theappropriate level of protection for the design environmentalcondition.


— The insulated type of immersion suits shall be provided for allpersonnel.

C519 Life raftarrangements


— The crew shall be able to launch/lower/release the rafts safelyin the design environmental condition.

— The hydrostatic release mechanism for the life rafts shall beable to function safely in the design environmental conditionand is protected from icing build-up.


— Life rafts shall not be damaged in stowage by ambient airtemperatures down to -30°C or 20°C colder than the designtemperature (td), whichever is colder.

— Life rafts shall remain operational in ambient air temperaturesdown to -15°C or the design temperature (td), whichever iscolder.


— Life rafts and their release and lowering systems shall beprovided with anti-icing protection.

— Life rafts shall be type approved and satisfy relevant criteriagiven in the LSA Code.

— Life rafts shall be tested in accordance with IMO Res.MSC/81(70) as amended and relevant for the equipment inquestion.

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C520 Lifeboatarrangements


— The crew shall be able to launch/lower/release and operate thelifeboats safely in the design environmental condition.


— Lifeboats shall not be damaged in stowage by ambient airtemperatures down to −30°C or 20°C colder than the designtemperature (td), whichever is colder.

— Lifeboats shall remain operational in ambient air temperaturesdown to -15°C or the design temperature (td), whichever iscolder.

— Lifeboat engines shall be arranged to ensure they will startreadily when required under the design environmentalconditions.

— Lifeboat engine fuel oil shall be suitable for operation underthe design environmental conditions.


— Lifeboats shall be type approved and satisfy relevant criteriagiven in the LSA Code.

— The lifeboats shall be tested to be undamaged in stowage byambient air temperatures down to -30°C or 20°C colder thanthe design temperature (td), whichever is colder.

— The lifeboats shall be tested to operate in ambient airtemperatures down to -15°C or the design temperature (td),whichever is colder.

— Lifeboats and their securing and launching systems shall befitted with anti-icing protection.

— Lifeboat engines shall be fitted with a heater.— Free-fall lifeboats are not acceptable for ships that have also

an ice class notation according to Sec.2 or Sec.5, unless thelifeboats have alternative means for lowering with their fullcomplement onboard.

C521 Lifeboatarrangements


— The crew shall be able to launch/lower/release and operate thelifeboats safely in the design environmental condition.


— Lifeboat davits/securing and launching systems shall be madefrom materials suitable for the design temperature (td).

— The lifeboat shall protect occupants from extreme cold.


— Anti-icing for lifeboats and lifeboat davits/securing andlaunching systems shall be arranged as passive protection.

— Materials for davit/securing and launching system componentsshall be selected according to C1001, as appropriate.

— The lifeboat shall be outfitted with internal heating.

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C522 Rescue boatarrangements


— The crew shall be able to immediately access, launch, andoperate the rescue boat under the design environmentalconditions.


— The rescue boat and its deployment and recovery equipmentshall be fitted with anti-icing protection.

C523 Rescue boatarrangements


— The rescue boat and deployment equipment shall functionunder the design environmental conditions.


— Rescue boat davits and related components shall be madefrom materials suitable for the design temperature (td).

— The rescue boat engine shall be arranged to ensure it will startreadily when required under the design temperature (td).


— Materials for rescue boat davits and related components shallbe selected according to C1001, as appropriate.

— Rescue boat engine fuel oil shall be suitable for operationunder the design temperature (td).

— The rescue boat engine shall be fitted with a heater.

C524 Machinery spacesheating system


— Spaces containing equipment necessary to perform mainfunctions and safety functions shall be kept at a temperaturethat ensures safe operation of the essential equipment.


— Engineering spaces shall be kept at a temperature of at least+5°C.


— Engineering spaces shall be provided with heating as required.Spaces that may need heating include, but are not limited to:steering gear room, emergency fire pump room, CO2 rooms,foam rooms, battery rooms, and bow thruster rooms.

— The heating consumption shall be calculated based on anexternal ambient temperature of 20°C below the designtemperature (td).

C525 Muster stationand survival craftarrangements


— Muster station, embarkation area and access to lifeboats andlife rafts must be immediately available and safe to use in anemergency under the design environmental conditions.

Prescriptive requirement

— Muster station, embarkation area, and access to the lifeboatsand life rafts shall be fitted with anti-icing protection.

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— Muster station, embarkation area and access to lifeboats andlife rafts shall be immediately available and safe to use in anemergency under the design environmental conditions.


— The muster station shall be located inside the superstructure,close to the lifeboats.

— The embarkation area and access to the lifeboats and life raftsshall be fitted with anti-icing protection.



— The muster station, embarkation area and lifeboat access shallbe dimensioned for people wearing suitable polar clothing.

C528 Other safetyarrangements


— The ship shall carry survival equipment suitable for the polarenvironment.


— The ship shall carry personal survival kits and group survivalkits as described in IMO Res. A.1024(26), Sec. 11.3 and 11.4.

— Sufficient personal and group survival kits shall be carried tocover at least 110% of the persons onboard the ship.

— Personal survival kits shall be stored in dedicated lockers in themuster station.

— Group survival kits shall be stored so that they may beeasily retrieved and deployed in an emergency situation.Containers shall be located adjacent to the survival craft andbe designed so that they may be easily moved over the iceand be floatable.

C529 Personal life-savingappliances


— Lifesaving equipment shall be stored so that the equipment isnot harmed by the cold climate, and so that it is immediatelyavailable.

— The bridge life-buoy shall be kept ice-free and immediatelyready to launch.


— Storage facilities for lifesaving equipment shall be fitted withanti-icing protection.

— The bridge life-buoy shall be provided anti-icing protectionand be arranged such that it is immediately deployable by thecrew.

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C530 Pressure reliefvalves


— Pressure relief valves shall function properly in the designenvironmental condition and shall not be impaired by ice orsnow.


— Pressure relief valves and vent heats associated with anypressure relief discharge line shall be provided anti-icingprotection.

— Associated piping arrangements shall be self-draining. Thedrains shall be located at the lowest points in the system, andthe piping layout shall ensure all liquids will drain to themwithout being trapped in U-bends, low points or dead-ends.

C531 Pressure reliefvalves


— Pressure relief valves shall function properly in the designenvironmental condition.


— Pressure relief valves shall be made from materials suitable forthe design temperature (td).


— Materials for pressure relief valves shall be selected accordingto C1001, as appropriate.

C532 Protective gear X X X Functional requirements:

— Appropriate personal protective equipment shall be providedthat protects the crew while working outdoors in the designenvironmental conditions, as well as from falling ice andslippery decks.

C533 Stairs X X X Functional requirements:

— Personnel should be able to move safely up and down stairs inthe design environmental conditions.


— External stairs and their top railing shall have anti-icingprotection to make them safe for personnel.

— Stairs that are not part of escape ways or not in regular usemay be considered, on a case-by-case basis, for de-icingprotection.

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C534 Ventilation systems X X X Functional requirements:

— Ventilation openings for spaces containing equipmentnecessary to perform main functions and safety functions shallbe operational at all times under the design environmentalconditions.


— Ventilation openings shall be provided with anti-icingprotection.

Guidance note:For Winterized(Cold) and Winterized(Polar), passiveprotection (e.g., protective cowlings or vestibules that preventsnow, ice or sea spray ingress) is preferred to active protection(e.g., heat tracing).


C535 Ventilation systems X X Functional requirements:

— Ventilation openings for spaces containing equipmentnecessary to perform main functions and safety functions shallbe operational at all times under the design environmentalconditions.


— Ventilation openings shall be equipped with an alarm toindicate blockage.

C536 Workingenvironment


— The deck/manifold watch shall be provided with a shelterthat keeps them warm and protects them from wind, coldand precipitation while also allowing them to perform theiressential duties.


— A heated watchman's shelter shall be arranged at the gangwayor at a location covering both the gangway and the loadingmanifold.

— The shelter shall be capable of maintaining an insidetemperature of at least +5°C. The heating consumptionrequirements shall be calculated based on an external ambienttemperature of 20°C colder than the design temperature (td).

C600 Hull and structure

C601 Helicopter deck X X X Functional requirements:

— The helicopter deck, where fitted, shall maintain its structuralintegrity under the additional loading of snow and iceaccumulation.


— The structural integrity of the helicopter deck design shall beconfirmed by calculations. Snow and ice loading calculationsin this requirement shall use the same snow and ice loads asthose used for stability calculations in C203.

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C602 Helicopter deck X X Functional requirements:

— An elevated helicopter deck, where fitted, shall be made frommaterials suitable for the material design temperature (td)specified in the class notation.


— Materials for an elevated helicopter deck shall be selectedaccording to C1001, as appropriate.

Guidance note:Material requirements for the main supporting structure for thehelicopter deck sub-structure are covered by Sec.4 for shipswith the DAT notation or by Sec.5 for ships with a PC ice classnotation.Material requirements for helicopter decks that are part of the hullstructure are covered by Sec.4 for ships with the DAT notation orby Sec.5 for ships with a PC ice class notation.Aluminium helidecks are suitable to all levels of winterization.


C700 Navigation

C701 Navigation bridge X X Functional requirements:

— The navigating officers shall be able to navigate the shipwithout being exposed to the outside environment.


— The navigation bridge wings shall be fully enclosed.— The ship’s side shall be visible from the bridge wings without

opening the bridge windows.— Additional conning positions (e.g., aloft conning position for

use in ice navigation, aft-facing conning positions), if fitted,shall also be fully enclosed.

C702 Navigation lights X X X Functional requirements:

— Navigation lighting shall be operable under the designenvironmental conditions.


— Navigation lights shall either generate sufficient heat to keepthe light fixture ice-free under the design environmentalconditions or be provided with anti-icing protection.

— Sidelight screens shall be provided with anti-icing protection toensure the required lighting sector is not obstructed by snowor ice accumulated on the screen.

— Navigation lights shall be tested for proper operation as perC703.

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C703 Navigation systems X X X Functional requirements:

— Navigation equipment required by SOLAS Ch.V and additionalnavigation equipment fitted to fulfil requirements of otherclass notations assigned to the ship (e.g., DYNPOS) shallbe available and operable under the design environmentalcondition.


— Relevant navigation equipment located outside or in unheatedcompartments shall be tested for proper operation at atemperature of -25°C or the design temperature (td) specifiedin the notation, whichever is colder.

Guidance note:Test procedures found in IEC 60945 may be adopted, using thetest temperature specified in the prescriptive requirement, above.



— Positioning sensors (e.g., anemometers) fitted to fulfilequipment requirements of other class notations assignedto the ship (e.g., DYNPOS) shall operate under the designenvironmental conditions.


— Such positioning sensors shall be either of a type not adverselyaffected by icing, or they shall have anti-icing protection.


— Antennae to navigation equipment required by SOLASCh.V and additional navigation equipment fitted to fulfilrequirements of other class notations assigned to theship (e.g., DYNPOS) shall function properly in the designenvironmental conditions.


— Relevant antennae shall be protected from snow and iceaccumulation that interferes with signal performance.

— The movement of rotating antennae (e.g., radar) shall not beinhibited by snow or ice.


— Relevant antennae shall be provided anti-icing protection.Antennae may be heated or placed in heated domes. Whiptype antennae do not require heating arrangements. Whererelevant equipment requires antennae that cannot be heated,then provision shall be made for easy access for manual de-icing.

— Dome and rod antennae shall be located such that heavysnowfall will not bury the antennae.

— Pedestals for rotating antennae (e.g., radar) shall have anti-icing to ensure rotation of the antenna is not inhibited by snowor ice under the design environmental conditions.

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C706 Navigation systems,other


— Windows to the navigation bridge shall be ice and frost freeunder the design environmental conditions.


— All windows within the required field of vision shall be providedwith appropriate heating arrangements. Windows shall complywith ISO 3434 and ISO 8863. The heating capacity shall bedesigned for an outside temperature of -20°C or less.

— Windows shall be fitted with window wipers that will operateand remain ice-free under the design environmentalconditions.

— Where fitted, window washers shall be protected from freezingunder the design environmental conditions.

Guidance note:Reference is made to ISO 17899 for marine electric windowwipers.When a field of vision larger than defined by SOLAS is requiredby a class notation, e.g. NAUT(AW), this should be taken intoaccount.


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C707 Searchlights X X Functional requirements:

— The ship shall have ice searchlights to aid in detection of iceduring navigation in darkness.

— The ice searchlights shall function in the design environmentalconditions.


— The luminous intensity of the focused position of the icesearchlight shall be sufficient to provide an illumination of 5.6lux at a distance of at least 1000 meters from the foremostpart of the ship or twice the ship’s stop distance at full speed,whichever is greater, with an atmospheric transmission of 0.8.


— The ship shall have at least one ice searchlight, which shallin so far as possible be located in the forepart of the ship,and shall be of sufficient luminous intensity to meet theperformance requirement.

— Ice searchlights shall be located and mounted so that thewheelhouse visibility is not obstructed in snow (i.e., the lightsshould be positioned as far forward as practicable and shouldnot be mounted above the viewing level of the navigationbridge).

— The lights shall be operable remotely from the wheelhouse.— The lights shall include functionality for focusing the cone of

light from the wheelhouse.— To function in the design environmental conditions, ice

searchlights shall be fitted with the following:

— means for securing the starter function at lowtemperatures;

— anti-condensation function of the searchlight housing;— anti-icing protection of the rotation mechanism, if the light

is rotatable.

C708 Sound signalappliances


— The ship’s whistle shall operate under the designenvironmental condition.


— The whistle shall be fitted with anti-icing to ensure it willoperate under the design environmental conditions.

— Steam or air lines to the whistle, where fitted, shall beprotected from freezing at the design temperature (td).

C800 Piping

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C801 Air pipes and ventheads


— Air pipes and vent heads to tanks shall be able to maintainproper tank ventilation under the design environmentalcondition.


— Air pipes and vent heads for all tanks shall be provided withanti-icing protection.

C802 Ballast tanks, freshwater tanks andother tanks


— The ship shall be able to safely ballast, de-ballast and shiftballast in the design environmental condition.

— Freezing of ballast water shall be controlled such that it doesnot cause any harm to the tank or equipment, and does notinterfere with ballasting, de-ballasting or shifting of ballast.

— For fresh water tanks and other tanks intended for holdingliquids subject to freezing under the design environmentalconditions, freezing of tank contents shall be controlled suchthat it does not cause any harm to the tank or equipment.


— The ship shall have an arrangement to prevent the surface ofballast tanks, fresh water tanks and other relevant tanks fromfreezing over under the design environmental conditions.

— GRP piping and other systems and structures in the tanks thatmay be damaged by freezing and falling ice shall be suitablyprotected.

— Tank level gauging shall function under the design operationalconditions.

— Where arrangements to prevent freezing of ballast waterare required under other sections of these Rules, the morestringent design environmental conditions shall be used incalculations.

— In determining the need for anti-freezing protection of freshwater and other relevant tanks, the freezing point of theintended tank contents shall be used in tank calculations.

Guidance note:An arrangement to prevent freezing of the ballast water neednot be provided for ballast tanks located fully below the waterline or lower ice water line (LIWL), whichever is lower, or whereheat balance calculations show the tank will not freeze under thedesign environmental conditions.An arrangement to prevent freezing of the ballast water neednot be provided for ballast tanks located fully below the waterline or lower ice water line (LIWL), whichever is lower, or whereheat balance calculations show the tank will not freeze under thedesign environmental conditions.It is assumed that, before pumping of tanks is commenced,proper functioning of level gauging arrangements is verified andair pipes are checked for possible blockage by ice.


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C803 Compressed airsystems


— The supply of compressed air to essential systems shall beprovided with air drying sufficient to prevent condensationunder the design environmental conditions.


— Compressed air shall be provided with air drying sufficientto lower the dew point to not warmer than -25°C or 15°Ccolder than the design temperature (td) at the actual pressure,whichever is colder.

C804 Fuel oil system X X Functional requirements:

— Transfer of fuel oil shall be possible under the designenvironmental conditions.


— Fuel oil heating system shall be sufficiently dimensionedto enable transfer of fuel under the design environmentalconditions.

— Transfer lines for heavy fuel oil exposed to the lowtemperature environment shall have heat tracing.

C805 Hydraulic powersystems


— Hydraulic systems serving main functions shall operate underthe design environmental conditions.


— Hydraulic fluid shall either be of a type that maintains anacceptable viscosity, or the hydraulic system shall haveheating/circulation arrangements to keep fluids at anappropriate temperature to ensure the operability of theessential systems they serve.

— For calculation of heating need and choice of hydraulic oilfor systems located outdoors or in non-heated spaces, atemperature of 20°C below the design temperature (td) shallbe used.

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C806 Piping X X X Functional requirements:

— Piping shall not be damaged by internal freezing under thedesign environmental conditions.


— Piping on open decks and in non-heated spaces that carryliquids susceptible to freezing under the design environmentalconditions shall be provided anti-freezing protection.


— Anti-freezing protection may be achieved by locating piping ina heated passageway or trunk, by providing them with heattracing, or by arranging them as a dry, self-draining system.Where piping is arranged as a dry, self-draining system, drainsshall be located at the lowest points in the system, and thepiping layout shall ensure all liquids will drain to them withoutbeing trapped in U-bends, low points or dead-ends.

C807 Pollution preventionarrangements


— The ship shall be designed to reduce the possibility of pollutingthe polar environment from oil pollution.


— The ship shall have the class notation Clean.— For oil tankers, the accidental oil outflow index: OM shall not

exceed 0.01 calculated in accordance with revised MARPOLAnnex I, Reg. 23.

— Non-toxic and biodegradable oil shall be used for stern tubeand controllable-pitch propeller systems.

C808 Sea chests X X X Functional requirements:

— Cooling water systems for machinery that are essential for thepropulsion and safety of the ship, including sea chests inlets,shall be designed to ensure supply of cooling water under thedesign environmental conditions.


— The sea cooling water inlet and discharge for main andauxiliary engines shall be arranged so that blockage of strumsand strainers by ice is prevented.


— A ship with an ice class notation shall comply with therespective requirements in Pt.3 Ch.11 Sec.1 [7.3], Sec.2[16.2] or Sec.5 [10], as appropriate for their ice class.

— A ship without an ice class notation shall comply with therequirements in eitherSec.1 [7.3], Sec.2 [16.2] or Sec.5[12.10].

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C809 Ventilation systemsfor hazardous cargoareas


— Venting system for cargo tanks shall be operational underdesign environmental conditions


— Cargo tank venting systems shall be fitted with anti-icingprotection (pressure/vacuum valves, pressure/vacuumbreakers, safety valves and flame arresters).

— Cargo tank pressure/vacuum breakers shall be fitted with anti-freezing protection (e.g., glycol or heating).

C900 Telecommunications

C901 Externalcommunicationsystems


— External communications systems required by SOLAS Ch.Vand additional communications equipment fitted to fulfilrequirements of other class notations assigned to the ship shallfunction properly in the design environmental conditions.


— Relevant antennae shall be protected from snow and iceaccumulation that interferes with signal performance.

— The movement of rotating antennae shall not be inhibited bysnow or ice.


— Relevant antennae shall be provided anti-icing protection.Antennae may be heated or placed in heated domes to protectthem from snow and ice accumulation. Whip type antennae donot require heating arrangements. Where relevant equipmentrequires antennae that cannot be heated, then provision shallbe made for easy access for manual de-icing

— Dome and rod antennae shall be located such that heavysnowfall will not bury the antennae.

— Pedestals for rotating antennae shall have anti-icing to ensurerotation of the antenna is not inhibited by snow or ice underthe design environmental conditions.

C902 Externalcommunicationsystems


— Communication equipment required by SOLAS Ch.Vand additional communications equipment fitted to fulfilrequirements of other class notations assigned to the ship shallfunction properly in the design environmental conditions.


— Relevant communication equipment located outside or inunheated compartments shall be tested and certified tooperate properly down to -25°C or the design temperature (td)specified in the notation, whichever is colder.

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C903 GMDSS - EPIRB X X X Functional requirements:

— The EPIRB shall be kept ice-free and immediately ready tolaunch.


— The EPIRB shall be provided anti-icing protection and bearranged such that it is able to float free to the surface withoutcrew intervention. Alternatively, the EPIRB shall be arrangedwith de-icing protection and an additional EPIRB mountedinside the wheelhouse, ready for immediate deployment by thecrew.

C904 GMDSS – globalmaritime distressand safety system


— Suitable communication equipment shall be fitted for highlatitude operations.


— The ship shall meet SOLAS Ch.IV communication equipmentrequirements for Area A4.

C1000 Multidiscipline

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C1001 Equipment material X X Functional requirements:

— All equipment exposed to the low temperature and beingimportant for ship operations shall be made from materialssuitable for the material design temperature (td) specified inthe class notation.


— For equipment or parts of equipment fabricated from platematerial, steel grades shall be selected as follows, according toSec.4 [2].

Class III:

— lifeboat and rescue boat davits— anchoring and mooring equipment— emergency towing arrangement (tankers).

Class II:

— cargo securing devices— mast with derrick having load greater than 3 tons— other equipment or components not specified as class I or

class III, unless upgraded or downgraded on a case-by-case basis due to special considerations of loading rate,level and type of stress, stress concentrations and loadtransfer points and/or consequences of failure.

Class I

— natural vents— cargo hatches, service hatches, access hatches.

— For pipes, the pipe material shall be selected in the samemanner as for plate material above or according to Pt.2 Ch.2Sec.4 [4].

— For equipment or parts of equipment fabricated from forgedor cast material, the impact test temperature and energy shallfulfil the requirements in Table C1001.

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C1002 Winterizationarrangements– installationsassociated withoptional classnotation


— Installations made in connection with optional class notationsand which are essential for safety shall function properly inthe design environmental conditions. Arrangements that areessential for safety include those required for a ship to performthe primary safety-related functions of its type.


— Rescue arrangements in a ship with class notation Standbyvessel shall be provided with anti-icing protection.

— Fire-fighting arrangements in a ship with the class notationFire fighter shall be provided with anti-icing and anti-freezingprotection.

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SECTION 4 DESIGN AMBIENT TEMPERATURE - DAT

1 General

1.1 IntroductionThe additional class notation DAT sets requirements to materials in ships of any type intended to operatefor longer periods in areas with low air temperatures, i.e. regular service during winter to Arctic or Antarcticwaters.

1.2 ScopeThe scope for the additional class notation DAT provides requirements to steel grades, based on the materialclass, for a given design ambient air temperature for ships of regular service during winter to Arctic orAntarctic waters.

1.3 ApplicationThe additional class notation DAT applies to ships complying with the rules in this section. The additionalclass notation DAT(t), where the qualifier t is indicating the temperature applied as basis for the approval.For further details, please see Table 1.

1.4 Class notationsShips built in compliance with the requirements as specified in Table 1 will be assigned the additional notationas follows:



DAT

Mandatory:

No


[2]

FiS requirements:


t Design ambient airtemperature suitable forregular service during winterto polar waters, where tdenotes the lowest designambient temperature in °C

1.5 Documentation requirementsFor general requirements to documentation, including definition of the Info codes, see Pt.1 Ch.3 Sec.2.For a full definition of the documentation types, see Pt.1 Ch.3 Sec.3.Documentation shall be submitted as required by Sec.3 Table 3.

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Technical information Z100 – Specification Design ambient air temperature suitable forregular service during winter, td.

AP

AP = For approval

1.6 Definitions1.6.1 Terminology and definitions

Table 3 Terminology and definitions

Term Definition

external structure the plating with stiffening to an inwards distance of 0.6 metre from the shell plating,exposed decks and exposed sides and ends of superstructure and deckhouses

design temperature the reference temperature used as a criterion for the selection of steel grades

The design temperature for external structures is defined as the lowest mean daily averageair temperature in the area of operation. This temperature is considered to be comparablewith the lowest monthly mean temperature in the area of operation −2°C. If operation isrestricted to summer navigation the lowest monthly mean temperature comparison mayonly be applied to the warmer half of the month in question.

For the purpose of issuing a polar ship certificate in accordance with the polar code (seeSec.5), the design temperature shall be no more than 13°C higher than the polar serviceemperature (PST) of the ship.

Temperature terms definition see Figure 1.

Guidance note:The design temperatures are defined by the user when signing the class contract. The extremedesign temperature may be set to about 20°C below the lowest mean daily average airtemperature, or the material design temperature, if information for the relevant trade area isnot available.


mean daily averagetemperature

the statistical mean average temperature for a specific calendar day, based on a number ofyears of observations (= MDAT)

monthly mean averagetemperature

the average of the mean daily temperature for the month in question (= MAMDAT)

lowest mean daily averagetemperature

the lowest value on the annual mean daily temperature curve for the area in question. Forseasonally restricted service the lowest value within the time of operation applies

lowest monthly meanaverage temperature

is the monthly mean temperature for the coldest month of the year

fore ship substructure includes the bow and the bow intermediate ice belt area, i.e. B and BIi, see Figure 1 inSec.5

MDHT mean* daily high (or maximum) temperature

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Term Definition

MDAT mean* daily average temperature

MDLT mean* daily low (or minimum) temperature

MAMDHT monthly average** of MDHT

MAMDAT monthly average** of MDAT

MAMDLT monthly average** of MDLT

MEHT monthly extreme high temperature (ever recorded)

MELT monthly extreme low temperature (ever recorded)

1) Mean: Statistical mean over observation period. In the polar regions, the statistical mean over observation periodshall be determined for a period of at least 10 years.

2) Average: Average during one day and night.

JAN FEBMARAPRMAYJUN JUL AUG SEPOCTNOVDEC

MEHT

MAMDAT

MAMDLT

MELT

MAMDHT

Figure 1 Commonly used definitions of temperatures

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2 Material selection

2.1 Structural categories

2.1.1 Structural strength members or areas are classified in four different classes for the purpose ofselecting required material grades. The relevant members are classified as specified in Table 4. The classesare generally described as follows:Class IV:

— Strakes in the strength deck and shell plating amidships intended as crack arrestors.— Highly stressed elements in way of longitudinal strength member discontinuities.

Class III:

— Plating chiefly contributing to the longitudinal strength.— Fore ship substructure for vessels with class notation Icebreaker.— Appendages of importance for the main functions of the ship, e.g. stern frames, rudder horns, rudder,

propeller nozzles and shaft bracket.— Aft ship substructures in ships equipped with podded propulsors and azimuth thrusters, and intended for

continuous operation astern.— Foundations and main supporting structures for heavy machinery and equipment.— Crane pedestal and main supporting structure.— Main supporting structure for helideck sub-structure.— Frames for windlasses, emergency towing and chain stopper, when equipment is welded to foundation or

deck (i.e. not applicable when equipment is bolted to foundation or deck).

Guidance note:Main supporting structures are primary load bearing members such as plates, girders, web frames/bulkheads and pillars.


Class II:

— Structures contributing to longitudinal and/or transverse hull girder strength in general.— Gutter bars of oil spill coamings attached to hull.— Structures for subdivisions.— Structures for cargo, bunkers and ballast containment.— Internal longitudinal members (stiffeners, girders) on plating exposed to external low temperatures where

class III and IV is required.— Deck house or superstructure exposed to longitudinal stresses within 0.6L amidship.

Class I:

— Local members in general unless upgraded due to special considerations of loading rate, level and type ofstress, stress concentrations and load transfer points and/or consequences of failure.

— Deckhouse or superstructure in general.— Cargo hatch covers.

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Table 4 Material classes of strength members in general.

Structural member Within 0.4 L amidships Elsewhere

SECONDARY:A1. Longitudinal bulkhead strakes, other than that

belonging to the Primary category

A2. Deck plating exposed to weather, other than thatbelonging to the Primary or Special category

A3. Side plating

A4. Transverse bulkhead plating10)

II II

PRIMARY:B1. Bottom plating, including keel plate

B2. Strength deck plating, excluding that belonging tothe Special category

B3. Continuous longitudinal members above strengthdeck, excluding hatch coamings

B4. Uppermost strake in longitudinal bulkhead10)

B5. Vertical strake (hatch side girder) and uppermostsloped strake in top wing tank10)

III 7) II

SPECIAL:C1. Sheer strake at strength deck 1), 2)

C2. Stringer plate in strength deck 1), 2)

C3. Deck strake at longitudinal bulkhead, excludingdeck plating in way of inner-skin bulkhead ofdouble-hull ships 1)

C4. Strength deck plating at outboard corners of cargohatch openings in container carriers and otherships with similar hatch opening configurations 3)

C5. Strength deck plating at corners of cargo hatchopenings in bulk carriers, ore carriers combinationcarriers and other ships with similar hatch openingconfigurations 4)

C7. Bilge strakes 1),8),9)

C8. Longitudinal hatch coamings of length greater than0.15L5)

C9. End brackets and deck house transition oflongitudinal cargo hatch coamings5)

IV III 6)

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Structural member Within 0.4 L amidships Elsewhere

1) Single strakes required to be of class IV or of grade VL E/EH and within 0.4 L amidships shall have breadths not lessthan (800 + 5 L)mm, and need not to be taken greater than 1 800 mm, unless limited by the geometry of the ship’sdesign.

2) Not to be less than grade VL E/EH within 0.4 L amidships in ships with length exceeding 250 m.3) Min. class IV within cargo region.4) Class IV within 0.6 L amidships and class III within rest of cargo region.5) Not to be less than grade VL D/DH.6) May be class II outside 0.6 L amidships.7) May be class II if relevant midship section modulus as built is not less than 1.5 times the rule midship section

modulus, and the excess is not credited in local strength calculations.8) Not to be less than grade VL D/DH within 0.4 L amidships in ships with length exceeding 250 m.9) May be of class III in ships with double bottom over the full breadth and length less than 150 m.10) Applicable to plating attached to hull envelope plating exposed to low air temperature. At least one strake shall be

considered in the same way as exposed plating and the strake width shall be at least 600mm

2.1.2 The material class requirement may be reduced by one class for:

— Laterally loaded plating having a thickness exceeding 1.25 times the requirement according to designformulae.

— Laterally loaded stiffeners and girders having section modulus exceeding 1.5 times the requirementaccording to design formulae.

2.2 Selection of steel grades

2.2.1 Plating materials for various structural categories as defined in [2.1]of exposed members, includingmembers defined in note 10 of Table 4, above the ballast waterline of ships with class notation DAT(t) shallnot be of lower grades than obtained from Figure 2 using the specified design temperature.

Plating materials of non-exposed members, except as defined in note 10 of Table 4shall not be of lower gradethan obtained according to Pt.3 Ch.3 Sec.1 Table 9.

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Figure 2 Required steel grades

Guidance note:When the structural category is known the material grade can be selected based on the design temperature and plate thickness.E.g. if a 30 mm plate should be applied for structural category III with a design temperature of –30oC, grade E or EH need to beapplied. Boundary lines form part of the lower grade.


2.2.2 Forged or cast materials in structural members subject to lower design temperatures than −10°Caccording to [2.1] shall fulfil requirements given in Sec.3 Table 6 item C1001.

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SECTION 5 POLAR CLASS - PC

1 General

1.1 IntroductionThe additional class notation PC sets requirements for ships constructed of steel, intended for navigation inice-infested polar waters. The requirements for the additional class notation PC are in general equivalent tothe IACS Unified Requirements for Polar Ships (UR I1 and UR I3).

1.2 ScopeThe scope for the additional class notation PC consider hull structure, main propulsion, steering gear,emergency and essential auxiliary systems essential for the safety of the ship and the survivability of thecrew.These rules do not consider aspects related to the operation of on-board equipment in cold climate. It isrecommended that ships intended to operate in cold climate environments for longer periods comply with therequirements as given in Sec.3.

1.3 Application

1.3.1 The additional class notation PC applies to steel ships complying with the requirements in this section,as listed in Table 1. If the hull and machinery are constructed such as to comply with the requirementsof different polar classes, then the ship shall be assigned the lower of these classes in the classificationcertificate. Compliance of the hull or machinery with the requirements of a higher polar class is also to beindicated in the classification certificate or an appendix thereto.Ships designed for ice breaking for the purpose of escort and ice management, and which are assigned apolar class notation PC(1) to PC(7), may be given the additional class notation Icebreaker, as given in Pt.5Ch.10 Sec.10.

1.3.2 For ships which are assigned a polar class notation, the hull form and propulsion power shall be suchthat the ship can operate independently and at continuous speed in a representative ice condition, as definedin Table 1 for the corresponding polar class. For the ships and ship-shaped units which are not intentionallydesigned to operate independently in ice, such operational intent or limitations shall be explicitly stated inappendix to the classification certificate.

1.3.3 For ships which are assigned a polar class notation PC(1) through PC(5), bows with vertical sides,and bulbous bows shall generally be avoided. Bow angle should in general be within range specified in[4.1.5].

1.3.4 For ships which are assigned a polar class notation PC(6) and PC(7), and are designed with a bowwith vertical sides or bulbous bows, operational limitations (restricted from intentional ramming) in designcondition shall be stated in appendix to the classification certificate.

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1.4 Class notations

1.4.1 Ships built in compliance with the requirements as specified in Table 1 will be assigned the additionalnotation as follows:



1 Ships intended for navigationin ice-infested polar waters

Year-round operation in all polar waters


Year-round operation in moderate multi-year iceconditions


Year-round operation in second-year ice whichmay include multi-year ice inclusions


Year-round operation in thick first-year ice whichmay include old ice inclusions


Year-round operation in medium first-year icewhich may include old ice inclusions


Summer/autumn operation in medium first-yearice which may include old ice inclusions

PC

Mandatory:

No


[3] to [13]

FiS requirements:



Summer/autumn operation in thin first-year icewhich may include old ice inclusions

1.4.2 It is the responsibility of the owner to select an appropriate polar class. The descriptions in Table 1 areintended to guide owners, designers and administrations in selecting an appropriate polar class to match therequirements for the ship with its intended voyage or service.

1.4.3 The polar class notation is used throughout the IACS Unified Requirements for Polar Ships to conveythe differences between classes with respect to operational capability and strength.

2 Documentation

2.1 Documentation requirements

2.1.1 For general requirements to documentation, including definition of the info codes, see Pt.1 Ch.3 Sec.2.For a full definition of the documentation types, see Pt.1 Ch.3 Sec.3.Documentation shall be submitted as required by Table 2.

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Technicalinformation

Z100 - Specification Main propulsionmachinery, steering,emergency andessential auxiliaries:Description, location,protection againstfreezing, ice andsnow, and operationalcapability in intendedenvironment.

FI

B030 - Internal watertight integrity plan FI

B070 - Preliminary damage stability calculation APDamage stability

B130 - Final damage stability calculation AP

Propulsion torqueand thrusttransmissionarrangement

C040 - Design analysis Ice load responsesimulation.

AP

Propellerarrangements

C040 - Design analysis Finite element analysisof blade stressesintroduced by ice loads

AP

Externalenvironment

Z100 - Specification Details of theenvironmentalconditions and therequired ice classfor the machinery, ifdifferent from ship’s iceclass.

FI


3 Design principles

3.1 Design temperature for structure and equipmentApplicable design temperature for the operation of the ship in ice infested waters shall be given in thedocumentation submitted for approval.

Guidance note:The design temperature reflects the lowest mean daily average air temperature in the intended area of operation. An extremeair temperature about 20°C below this may be tolerable to the structures and equipment from a material point of view. Forcalculations where the most extreme temperature over the day is relevant, the air temperature can be set 20°C lower than thedesign temperature in the notation.If no specification of the design temperature has been given, the values -35ºC for notations PC(1) to PC(5) and -25ºC fornotations PC(6) and PC(7) will be considered.


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3.2 Hull areas

3.2.1 The hull of polar class ships is divided into areas reflecting the magnitude of the loads that areexpected to act upon them. In the longitudinal direction, there are four regions: bow, bow intermediate,midbody and stern. The bow intermediate, midbody and stern regions are further divided in the verticaldirection into the bottom, lower and ice belt regions. The extent of each hull area is illustrated in Figure 1.

min

Figure 1 Hull area extents

3.2.2 The upper ice waterline (UIWL) and lower ice waterline (LIWL) are as defined in Sec.1.

3.2.3 Figure 1 notwithstanding, at no time is the boundary between the bow and bow intermediate regionsto be forward of the intersection point of the line of the stem and the ship baseline.

3.2.4 Figure 1 notwithstanding, the aft boundary of the bow region need not be more than 0.45 L aft of theforward perpendicular (F.P.).

3.2.5 The boundary between the bottom and lower regions shall be taken at the point where the shell isinclined 7° from horizontal.

3.2.6 If a ship is intended to operate astern in ice regions, the aft section of the ship shall be designed usingthe bow and bow intermediate hull area requirements as given in [4.7].

3.3 System design

3.3.1 Systems, subject to damage by freezing, shall be drainable.

3.3.2 Ships classed PC(1), to PC(5) inclusive shall have means provided to ensure sufficient ship operationin the case of propeller damage including CP-mechanism, i.e. pitch control mechanism.

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Sufficient ship operation means that the ship should be able to reach safe harbour (safe location) whererepair can be undertaken in case of propeller damage. This may be achieved either by a temporary repair atsea, or by towing assuming assistance is available (condition for approval).

3.3.3 Means shall be provided to free a stuck propeller by turning backwards. This means that a plantintended for unidirectional rotation shall be equipped at least with a sufficient turning gear that is capable ofturning the propeller in reverse direction.

3.3.4 Propulsion powerGuidance note:For PC no explicit power requirement exists. However, according to IMO guidelines for Ships operating in Polar waters ships shallhave sufficient propulsion power and sufficient manoeuvrability for operation in intended area.Engine power may be selected according to current rule practice. We advise to use model test alternative.


4 Design ice loads – hull

4.1 General

4.1.1 A glancing impact on the bow is the design scenario for determining the scantlings required to resistice loads.

4.1.2 The design ice load is characterized by an average pressure Pavg uniformly distributed over arectangular load patch of height b and width w.

4.1.3 Within the bow area of polar class ships, and within the bow intermediate ice belt area of polar classPC(6) and PC(7), the ice load parameters are functions of the actual bow shape. To determine the ice loadparameters Pavg, b and w, it is required to calculate the following ice load characteristics for sub-regions ofthe bow area; shape coefficient fai, total glancing impact force Fi, line load Qi and pressure Pi.

4.1.4 In other ice-strengthened areas, the ice load parameters Pavg, bNonBow and wNonBow are determinedindependently of the hull shape and based on a fixed load patch aspect ratio, AR = 3.6.

4.1.5 Design ice forces, calculated according to [4.3.3], are applicable for bow forms where the buttockangle γ at the stem is positive and less than 80 degrees, and the normal frame angle β' at the center of theforemost sub-region, as defined in [4.3.1], is greater than 10 degrees.

4.1.6 Design ice forces calculated according to [4.3.4] are applicable for ships which are assigned the polarclass PC(6) or PC(7) and have bow form with vertical sides. This includes bows where the normal frameangles β' at considered sub-regions, as defined in [4.3.1], are between 0 and 10 deg.

4.1.7 For ships which are assigned the polar class PC(6) or PC(7), and equipped with bulbous bows, thedesign ice forces in the vicinity of the bulb shall be determined according to [4.3.4]. The design ice forces forthe remaining part of the bow are to be specially considered. In addition, the design ice forces are not to betaken less than those given in [4.3.3] assuming fa = 0.6 and AR = 1.3.

4.1.8 For ships with bow forms other than those defined in [4.1.5] - [4.1.7], design forces shall be speciallyconsidered.

4.1.9 Ship structures that are not directly subjected to ice loads may still experience inertial loads of stowedcargo and equipment resulting from ship/ice interaction, as given in [4.1.10] – [4.1.12], which shall beconsidered as alternative to the design accelerations given in Pt.3 Ch.4 Sec.3.

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4.1.10 Maximum longitudinal impact acceleration, in m/s2, at any point along the hull girder, to be taken as:

4.1.11 Combined vertical impact acceleration, in m/s2, at any point along the hull girder, to be taken as:

where:

Fx = 1.3 at F.P.= 0.2 at midships= 0.4 at A.P.= 1.3 at A.P. for ships conducting ice breaking astern.

Intermediate values to be interpolated linearly.

4.1.12 Combined transverse impact acceleration, in m/s2, at any point along hull girder, to be taken as:

where:

Fx = 1.5 at F.P.= 0.25 at midships= 0.5 at A.P.= 1.5 at A.P. for ships conducting ice breaking astern.


where:

φ = maximum friction angle between steel and ice, normally taken as 10°, in degreesγ = bow stem angle at waterline, in degreesΔtk = displacement at UIWL, in ktH = vertical distance from UIWL to the point being considered, in mFIB = vertical impact force, defined in [6.2], in MNFBow = as defined in [4.5.1], in MN.

4.2 Glancing impact load characteristics

4.2.1 The parameters defining the glancing impact load characteristics are reflected in the class factors listedin Table 3 and Table 4.

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Table 3 Class factors to be used in [4.3.3]

Polarclass

Crushing failureclass factor (CFC)

Flexural failure

class factor (CFF)

Load patchdimensions

class factor (CFD)

Displacement

class factor (CFDIS)Longitudinal strength

class factor (CFL)

PC(1) 17.69 68.60 2.01 250 7.46

PC(2) 9.89 46.80 1.75 210 5.46

PC(3) 6.06 21.17 1.53 180 4.17

PC(4) 4.50 13.48 1.42 130 3.15

PC(5) 3.10 9.00 1.31 70 2.50

PC(6) 2.40 5.49 1.17 40 2.37

PC(7) 1.80 4.06 1.11 22 1.81

Table 4 Class factors to be used in [4.3.4]

Polar class Crushing failureclass factor (CFCV)

Line load class factor (CFQV) Pressure class factor (CFPV)

PC(6) 3.43 2.82 0.65

PC(7) 2.60 2.33 0.65

4.3 Bow area

4.3.1 In the bow area, the force F, line load Q, pressure P and load patch aspect ratio AR associated with theglancing impact load scenario are functions of the hull angles measured at the upper ice waterline UIWL. Theinfluence of the hull angles is captured through calculation of a bow shape coefficient fa. The hull angles aredefined in Figure 2.

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Figure 2 Definition of hull angles

β’ = normal frame angle at upper ice waterline, in degreesα = upper ice waterline angle, in degreesγ = buttock angle at upper ice waterline (angle of buttock line measured from horizontal), in

degreestan(β) = tan(α)/tan(γ)tan(β’) = tan(β) cos(α).

4.3.2 The waterline length of the bow region is generally to be divided into 4 sub-regions of equal length.The force F, line load Q, pressure P and load patch aspect ratio AR shall be calculated with respect to themid-length position of each sub-region (each maximum of F, Q and P shall be used in the calculation of theice load parameters Pavg, b and w).

4.3.3 The bow area load characteristics for bow forms defined in [4.1.5] are determined as follows:

a) Shape coefficient, fai, shall be taken as

fai = minimum (fai,1; fai,2; fai,3)where:

fai,1 = (0.097 − 0.68 (x/Li − 0.15)2) · αi / (β’i)0.5

fai,2 = 1.2 · CFF / (sin (β’i) · CFC · Δtk0.64)

fai,3 = 0.60

i = sub-region considered

Li = ship length as defined in Pt.3 Ch.1, measured on the upper ice waterline(UIWL), in m

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x = distance from the forward perpendicular (FE) to station under consideration,in m

α = waterline angle,in degrees, see Figure 2

β’ = normal frame angle,in degrees, see Figure 2

Δtk = ship displacement, in ktonnes, at UIWL, not to be taken less than 5 kt

CFC = crushing failure class factor from Table 3

CFF = flexural failure class factor from Table 3

b) Force, in MN:

Fi = fai · CFC · Δtk0.64

where:


fai = shape coefficient of sub-region i

CFF = crushing failure class factor from Table 3

Δtk = ship displacement, in ktonnes, at UIWL, not to be taken less than 5 kt

c) Load patch aspect ratio, AR:

ARi = 7.46 · sin (β’i) ≥ 1.3where:


β’ = normal frame angle of sub-region i, in degrees

d) Line load, in MN/m:

Qi = Fi0.61 · CFD / ARi

0.35

where:


Fi = force of sub-region i, in MN

CFD = load patch dimensions class factor from Table 3

ARi = load patch aspect ratio of sub-region i

e) Pressure, in MPa:

Pi = Fi0.22 · CFD

2 · ARi0.3

where:


Fi = force of sub-region i, in MN


ARi = load patch aspect ratio of sub-region i.

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4.3.4 The bow area characteristics for bow forms defined in [4.1.6] are determined as follows:

a) Shape coefficient, fai, shall be taken as:

fai = αi / 30b) Force, Fi, in MN:

Fi = fai · CFCV · Δtk0.47

c) Line load, Qi, in MN/m:Qi = Fi

0.22 · CFQVd) Pressure, Pi, in MPa:

Pi = F0.56 · CFPV

where:

i = sub-region consideredα = waterline angle [deg], see Figure 2Δtk = ship displacement [kt], as defined in [4.3.3]CFCV = crushing failure class factor from Table 4CFQV = line load class factor from Table 4CFPV = pressure class factor from Table 4.

4.4 Hull areas other than the bow

4.4.1 In the hull areas other than the bow, the force FNonBow and line load QNonBow used in the determinationof the load patch dimensions (bNonBow, wNonBow) and design pressure Pavg are determined as follows:

a) Force, in MN:

FNonBow = 0.36 · CFC · DF

b) Line load, in MN/m:

QNonBow = 0.639 · FNonBow0.61 · CFD

where:

CFC = crushing force class factor from Table 3


DF = ship displacement factor

= Δtk0.64 if Δtk ≤ CFDIS

= CFDIS0.64 + 0.10 (Δtk - CFDIS) if Δtk > CFDIS

Δtk = ship displacement, in ktonnes at UIWL, not to be taken less than 10 ktonnes

CFDIS = displacement class factor from Table 3.

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4.5 Design load patch

4.5.1 In the bow area for all PC-classes, and the bow intermediate ice belt area for ships with class notationPC(6) and PC(7), the design load patch, in m, has dimensions of width, wBow, and height, bBow, defined asfollows:

wBow = FBow / QBow

bBow = QBow / PBow

where:

FBow = maximum force Fi in the bow area, ref. [4.3.3] b), in MN

QBow = maximum line load Qi in the bow area, ref. [4.3.3] d), in MN/m

PBow = maximum pressure Pi in the bow area, ref. [4.3.3] e), in MPa.

4.5.2 In hull areas other than those covered by [4.5.1], the design load patch, in m, has dimensions ofwidth, wNonBow, and height, bNonBow, defined as follows:

wNonBow = FNonBow / QNonBow

bNonBow = wNonBow / 3.6

where:

FNonBow = ice force as given by [4.4.1], in MNQNonBow = ice line load as given by [4.4.1], in MN/m.

4.6 Pressure within the design load patch

4.6.1 The average pressure within a design load patch, in MPa, is determined as follows:

Pavg = F / (b·w)

where:

F = FBow or FNonBow, see [4.5.1] and [4.5.2] as appropriate for the hull area under consideration, in MN

b = bBow or bNonBow, see [4.5.1] and [4.5.2] as appropriate for the hull area under consideration, in m

w = wBow or wNonBow , see [4.5.1] and [4.5.2] as appropriate for the hull area under consideration, in m.

4.6.2 Areas of higher, concentrated pressure exist within the load patch. In general, smaller areas havehigher local pressures. Accordingly, the peak pressure factors listed in Table 5 are used to account for thepressure concentration on localized structural members.

4.7 Hull area factors

4.7.1 Associated with each hull area is an area factor that reflects the relative magnitude of the loadexpected in that area. The area factor (AF) for each hull area is listed in Table 6.

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4.7.2 In the event that a structural member spans across the boundary of a hull area, the largest hull areafactor shall be used in the scantling determination of the member.

4.7.3 Due to their increased manoeuvrability, ships having propulsion arrangements with azimutingthruster(s) or podded propellers shall have specially considered stern ice belt (Si) and stern lower (Sl) hullarea factors according to Table 7. The fore boundary of the stern region shall be at least 0.04 L forward ofthe section where the parallel ship side at the upper ice waterline (UIWL) ends.

4.7.4 For ships intended to operate astern in ice regions, the area factor as for the bow shall be used for allstructure within the stern ice belt area, and the bow intermediate lower and bottom area factors increased by10% shall be used for the stern lower and bottom areas, appendages included. In addition stern intermediateareas shall be defined for the aft ship as for the fore ship. The area factor (AF) for ships intended to operateastern is listed in Table 8.

Table 5 Peak pressure factors

Structural member Peak pressure factor (PPFi)

Transversely-framed PPFp = (1.8 − s) ≥ 1.2Plating

Longitudinally-framed PPFp = (2.2 − 1.2·s) ≥ 1.5

With load distributing stringers1) PPFt = (1.6 − s) ≥ 1.0Frames in transverse

Framing systems With no load distributing stringers1) PPFt = (1.8 − s) ≥ 1.2

Frames in bottom structures PPFs = 1.0

Load carrying stringers

Side longitudinals

Web frames

PPFs = 1, if Sw ≥ 0.5 · wPPFs = 2.0 − 2.0 · Sw / w, if Sw < (0.5 · w)

where

s = frame or longitudinal spacing [m]

Sw = web frame spacing [m]

w = ice load patch width [m]

1) In order that the reduced PPFt value may be used, the load distributing stringer shall be located at or close to themiddle of span of the transverse frames, to have web height not less than the 80% of the transverse frames, and tohave net web thickness not less than the net web thickness of the transverse frames.

Table 6 Hull area factors (AF)

Polar classHull area Area

PC(1) PC(2) PC(3) PC(4) PC(5) PC(6) PC(7)

Bow (B) All B 1.00 1.00 1.00 1.00 1.00 1.00 1.00

Ice belt BIi 0.90 0.85 0.85 0.80 0.80 1.00* 1.00*

Lower BIl 0.70 0.65 0.65 0.60 0.55 0.55 0.50Bow intermediate(BI)

Bottom BIb 0.55 0.50 0.45 0.40 0.35 0.30 0.25

Ice belt Mi 0.70 0.65 0.55 0.55 0.50 0.45 0.45

Lower Ml 0.50 0.45 0.40 0.35 0.30 0.25 0.25Midbody (M)

Bottom Mb 0.30 0.30 0.25 ** ** ** **

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PC(1) PC(2) PC(3) PC(4) PC(5) PC(6) PC(7)

Ice belt Si 0.75 0.70 0.65 0.60 0.50 0.40 0.35

Lower Sl 0.45 0.40 0.35 0.30 0.25 0.25 0.25Stern (S)

Bottom Sb 0.35 0.30 0.30 0.25 0.15 ** **

Notes:

* = See [4.1.3].

** = Indicates that strengthening for ice loads is not necessary.

Table 7 Hull area factors (AF) for ships with thrusters/podded propulsion


PC(1) PC(2) PC(3) PC(4) PC(5) PC(6) PC(7)

Bow (B) All B 1.00 1.00 1.00 1.00 1.00 1.00 1.00

Ice belt BIi 0.90 0.85 0.85 0.80 0.80 1.00* 1.00*


Bottom BIb 0.55 0.50 0.45 0.40 0.35 0.30 0.25

Ice belt Mi 0.70 0.65 0.55 0.55 0.50 0.45 0.45

Lower Ml 0.55 0.45 0.40 0.35 0.30 0.25 0.25Midbody (M)

Bottom Mb 0.30 0.30 0.25 ** ** ** **

Ice belt Si 0.90 0.85 0.80 0.75 0.65 0.55 0.50

Lower Sl 0.60 0.55 0.50 0.45 0.40 0.40 0.40Stern (S)

Bottom Sb 0.35 0.30 0.30 0.25 0.15 ** **

Notes:

* = See [4.1.3].


Table 8 Hull area factors (AF) for ships intended to operate astern


PC(1) PC(2) PC(3) PC(4) PC(5) PC(6) PC(7)

Bow (B) All B 1.00 1.00 1.00 1.00 1.00 1.00 1.00

Icebelt BIi 0.90 0.85 0.85 0.80 0.80 1.00* 1.00*


Bottom BIb 0.55 0.50 0.45 0.40 0.35 0.30 0.25

Midbody (M) Icebelt Mi 0.70 0.65 0.55 0.55 0.50 0.45 0.45

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PC(1) PC(2) PC(3) PC(4) PC(5) PC(6) PC(7)

Lower Ml 0.50 0.45 0.40 0.35 0.30 0.25 0.25

Bottom Mb 0.30 0.30 0.25 ** ** ** **

Icebelt SIi 0.90 0.85 0.85 0.80 0.80 1.00* 1.00*

Lower SIl 0.70 0.65 0.65 0.60 0.55 0.55 0.50Stern Intermediate(SI)***

Bottom SIb 0.55 0.50 0.45 0.40 0.35 0.30 0.25

Icebelt Si 1.00 1.00 1.00 1.00 1.00 1.00 1.00

Lower Sl 0.77 0.72 0.72 0.66 0.61 0.61 0.55Stern (S)

Bottom Sb 0.61 0.55 0.50 0.44 0.39 0.33 0.28

Notes:

* = See [4.1.3].


***= The Stern intermediate region, if any, for ships intended to operate astern shall be defied as the region forwardof Stern region to section 0.04 L forward of WL angle = 0 degrees at UIWL (see definition of bow intermediate inFigure 1).

4.8 Ice compression load amidships

4.8.1 All ships shall withstand line loads acting simultaneously in the horizontal plane at the water level onboth sides of the hull. These loads are assumed to arise when a ship is trapped between moving ice floes.The parameter for ice thickness CFm is given in Table 9 and will be stated in the appendix to the classificationcertificate.

Table 9 Ice compression class factors

Polar class CFm

PC(1) 3.0

PC(2) 2.5

PC(3) 2.0

PC(4) 1.6

PC(5) 1.2

PC(6) 0.7

PC(7) 0.5

4.8.2 The design line loads, in kN/m, shall be taken as:

(1)

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For vertical side shells with βf < 10 degrees, the design line loads, in kN/m, may be taken as:

(2)

where:

CFm = Ice compression class factorβf = Angle of outboard flare at the water level, in degrees.

The stresses, in N/mm2, resulting from bending moments and shearing forces shall not be greater than thefollowing permissible values:

Normal stress = 0.67ReH

Shear stress = 0.67τeH

von Misesstress

= 0.75ReH

5 Local strength requirements

5.1 Shell plate requirements

5.1.1 The required minimum gross shell plate thickness, in mm, is given by:

tgr = t + ts

where:

t = net plate thickness required to resist ice loads according to [5.1.2], in mmts = corrosion and abrasion allowance according to [10.1], in mm.

5.1.2 The thickness of shell plating required to resist the design ice load, t, depends on the orientation of theframing.

In the case of transversely-framed plating (Ω ≥ 70 deg), including all bottom plating, i.e. plating in hull areasBIb, Mb and Sb, the net thickness, in mm, is given by:

In the case of longitudinally-framed plating (Ω ≤ 20°), when b ≥ s, the net thickness, in mm, is given by:

In the case of longitudinally-framed plating (Ω ≤ 20°), when b < s, the net thickness, in mm, is given by:

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In the case of obliquely-framed plating (70° > Ω > 20°), linear interpolation shall be used.

where:

Ω = smallest angle between the chord of the waterline and the line of the first level framing asillustrated in Figure 3, in degrees

s = transverse frame spacing in transversely-framed ships or longitudinal frame spacing inlongitudinally-framed ships, in m

AF = hull area factor from Table 6, Table 7 or Table 8PPFp = peak pressure factor from Table 5Pavg = average patch pressure as given in [4.6], in MPab = height of design load patch, in m, where b ≤ (ℓ – s/4) in the case of transversely framed platingℓ = distance between frame supports, i.e. equal to the frame span as given in [5.2.5], but not

reduced for any fitted end brackets, in m. When a load-distributing stringer is fitted, the length lneed not be taken larger than the distance from the stringer to the most distant frame support.

Figure 3 Shell framing angle Ω

5.2 Framing general

5.2.1 Framing members of polar class ships shall be designed to withstand the ice loads defined in [4].

5.2.2 The term framing member refers to transverse and longitudinal local frames (stiffeners), load-carryingstringers and web frames in the areas of the hull exposed to ice pressure, see Figure 1.

5.2.3 The strength of a framing member is dependent upon the fixity that is provided at its supports.Fixity can be assumed where framing members are either continuous through the support or attached toa supporting section with a connection bracket. In other cases, simple support should be assumed unlessthe connection can be demonstrated to provide significant rotational restraint. Fixity shall be ensured at thesupport of any framing which terminates within an ice-strengthened area.

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5.2.4 The details of framing member intersection with other framing members, including plated structures,as well as the details for securing the ends of framing members at supporting sections, shall be in accordancewith [5.9] and Pt.3 Ch.3 Sec.5 [3], Pt.3 Ch.3 Sec.5 [4], Pt.3 Ch.3 Sec.6 [1] and Pt.3 Ch.6 Sec.7 asapplicable.

5.2.5 The design span of framing members shall generally be determined according to Pt.3 Ch.3 Sec.6 [1].However, the span length is only to be reduced in accordance with Pt.3 Ch.3 Sec.6 [1] provided the endbrackets fitted are flanged or the free edge length in mm is equal to or less than 600 tb /ReH

0.5.tb = net thickness of bracket, in mm.

5.2.6 Load-carrying stringers and web frames are generally to be of symmetrical cross-section. When theflange is arranged to be unsymmetrical, an effective tripping support shall be provided at the middle of eachspan length.

5.2.7 When calculating the section modulus and shear area of a framing member, net thickness of the web,flange (if fitted) and of the attached shell plating shall be used. The shear area of a framing member mayinclude that material contained over the full depth of the member, i.e. web area including portion of flange, iffitted, but excluding attached shell plating.

5.2.8 The actual net effective shear area of a framing member, in cm2, is given by:

where:

h = height of stiffener, in mm, see Figure 4tw = net web thickness, in mm

= tw-as-built-tstw-as-built = as built web thickness, in mm, see Figure 4ts = corrosion addition, in mm, as given in [10.1.3], to be subtracted from the web and flange

thicknessφw = smallest angle between shell plate and stiffener web, in degrees, measured at the midspan

of the stiffener, see Figure 4. The angle φw may be taken as 90 degrees provided thesmallest angle is not less than 75 degrees.

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Figure 4 Stiffener geometry

5.2.9 When the cross-sectional area of the attached plate flange, Apn, exceeds the cross-sectional area ofthe local frame, (Afn+hw· tw/100), the actual net effective plastic section modulus, in cm3, of a transverse orlongitudinal frame (stiffeners), is given by:

where:

h, tw, and φw are as given in [5.2.7] and s as given in [5.1.2].

Ap = net cross-sectional area of the fitted shell plate, (tpn·s·10), in cm2

tp = fitted net shell plate thickness, in mm (shall comply with t as required by [5.1.2])hw = height of local frame web, in mm, see Figure 4Af = net cross-sectional area of local frame flange, in cm2

hfc = height of local frame measured to centre of the flange area, in mm, see Figure 4bw = distance from mid thickness plane of local frame web to the centre of the flange area, in mm, see

Figure 4.

When the cross-sectional area of the local frame exceeds the cross-sectional area of the attached plateflange, the plastic neutral axis is located a distance above the attached shell plate, in mm, given by:

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and the net effective plastic section modulus, of a transverse or longitudinal frame (stiffeners) in cm3, isgiven by:

5.2.10 In the case of oblique framing arrangement 70° > Ω > 20°, where Ω is defined as given in [5.1.2],linear interpolation shall be used.

5.3 Framing – transversely framed side structures and bottom structures

5.3.1 Local frames in bottom structure (i.e. hull areas BIb, Mb and Sb) and transverse local frames(stiffeners) in side structure shall be dimensioned such that the combined effects of shear and bending donot exceed the plastic strength of the member. The plastic strength is defined by the magnitude of patch loadthat causes the development of a plastic hinge mechanism.For bottom structure the patch load shall be applied with the dimension (b) parallel with the frame direction.

5.3.2 The actual net effective shear area of the frame, in cm2, as defined in [5.2.8], shall comply with thefollowing condition: Aw ≥ At, where:

where:

LL = length of loaded portion of span= lesser of a and b, in m

a = frame span as defined in [5.2.5], in mb = height of design ice load patch as given in [4.5], in ms = spacing of local frame, in mAF = hull area factor from Table 6, Table 7 and Table 8PPFt = peak pressure factor from Table 5Pavg = average pressure within load patch as given in [4.6], in MPa.

5.3.3 The actual net effective plastic section modulus of the plate/stiffener combination, in cm3, as defined in[5.2.9], shall comply with the following condition: Zp ≥ Zpt, where Zpt shall be the greater calculated on thebasis of two load conditions: a) ice load acting at the midspan of the transverse frame, and b) the ice loadacting near a support. The A1 parameter reflects the two conditions:

where:

AF, PPFt, Pavg, LL, b, s, and a are as given in [5.3.2].

Y = 1 - 0.5·(LL / a)

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A1 = maximum of:

A1A = 1 / (1 + j / 2 + kw·j / 2·[(1 - a12) 0.5 - 1])

A1B = (1 – 1 / (2·a1·Y)) / (0.275 + 1.44·kz0.7)

j = 1 for a local frame with one simple support outside the ice-strengthened areas

= 2 for a local frame without any simple supports

a1 = At / Aw

At = Minimum shear area of the local frame as given in [5.3.2], in cm2

Aw = Effective net shear area of the local frame (calculated according to [5.2.8], incm2

kw = 1 / (1 + 2·Afn / Aw) with Afn as given in [5.2.9]

kz = zp / Zp in general

0.0 when the frame is arranged with end bracket

zp = sum of the individual plastic section modulus of flange and shell plate as fitted, in cm3

= (bf·tfn2 / 4 + beff·tpn

2 / 4) / 1000

bf = flange breadth, in mm, see Figure 4

tf = net flange thickness, in mm

= tf-as-built–ts (ts as given in [5.2.8])

tf-as-built = as-built flange thickness, in mm, see Figure 4

tp = the fitted net shell plate thickness, in mm (not to be less than tnet as given in [5.1.2])

beff = effective width of shell plate flange, in mm

= 500 s

Zp = net effective plastic section modulus of the local frame (calculated according to [5.2.9]), incm3.

5.3.4 The scantlings of the frame shall meet the structural stability requirements of [5.6].

5.4 Framing – longitudinal local frames in side structure

5.4.1 Longitudinal local frames in side structure shall be dimensioned such that the combined effects ofshear and bending do not exceed the plastic strength of the member. The plastic strength is defined by themagnitude of midspan load that causes the development of a plastic collapse mechanism.

5.4.2 The actual net effective shear area of the frame, in cm2, as defined in [5.2.8], shall comply with thefollowing condition:

Aw ≥ AL

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where:

AF = hull area factor from Table 6, Table 7 or Table 8PPFs = peak pressure factor from Table 5Pavg = average pressure within load patch as given in [4.6], in MPab1 = ko·b2 in mko = 1 − 0.3 / b’b’ = b / sb = height of design ice load patch as given by [4.5.1] or [4.5.2], in ms = spacing of longitudinal frames, in mb2 = corrected load height, in m

= b (1 − 0.25·b’) if b’ < 2= s if b’ ≥ 2

a = longitudinal design span as given in [5.2.5], in m.

5.4.3 The actual net effective plastic section modulus of the plate/stiffener combination, in cm3, as defined in[5.2.9], shall comply with the following condition:

ZP ≥ ZPL

where:

AF, PPFs, Pavg, b1, and a are as given in [5.4.2].

A4 = 1 / (2 + kwℓ·[(1 - a42)0.5 - 1])

a4 = AL / Aw

AL = minimum shear area for longitudinal as given in [5.4.2], in cm2

Aw = net effective shear area of longitudinal (calculated according to [5.2.8]), in cm2

kwℓ = 1 / (1 + 2·Af / Aw) with Af as given in [5.2.9].

5.4.4 The scantlings of the longitudinals shall meet the structural stability requirements of [5.6].

5.5 Framing – web frames and load carrying stringers

5.5.1 Web frames and load-carrying stringers shall be designed to withstand the ice load patch as defined in[4.5]. The load patch shall be applied at locations where the capacity of these members under the combinedeffects of bending and shear is minimised.

5.5.2 For determination of scantlings of load carrying stringers, web frames supporting local frames or webframes supporting load carrying stringers forming part of a structural grillage system, appropriate methodsoutlined in [8] shall normally be used.

5.5.3 The scantlings of web frames and load-carrying stringers shall meet the structural stabilityrequirements of [5.6].

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5.6 Framing – structural stability

5.6.1 To prevent local buckling in the web, the ratio of web height, hw, to net web thickness, tw, of anyframing member (stiffener) shall not exceed:

For flat bar sections:

hw / tw ≤ 282 / (ReH)0.5

For bulb, tee and angle sections:

hw / tw ≤ 805 / (ReH)0.5

where:

hw = web height, in mmtw = net web thickness, in mm.

5.6.2 Load carrying stringers or web frames, are required to have their webs effectively stiffened. Theminimum net web thickness for these framing members, in mm, is given by:

where:

c1 = hw – 0.8·h, in mm

hw = web height of stringer/web frame, in mm, see Figure 5h = height of framing member penetrating the member under consideration (0 if no such framing

member), in mm, see Figure 5c2 = spacing between supporting structure oriented perpendicular to the member under consideration, in

mm, see Figure 5.

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Figure 5 Parameter definition for web stiffening

5.6.3 In addition, the following shall be satisfied:

tw ≥ 0.35·tp·(ReH / 235)0.5

where:

ΡeH = minimum upper yield stress of the shell plate in way of the framing member, in N/mm2

tw = net thickness of the web, in mmtp = net thickness of the shell plate in way of the framing member, in mm.

5.6.4 To prevent local flange buckling of welded profiles, the following shall be satisfied:

— the flange width, bf in mm, shall not be less than 5 × tw— the flange outstand, bf-out, as defined in Pt.3 Ch.8 Sec.2, in mm, shall meet the following requirement:

bf-out / tf ≤ 155 / (ReH)0.5

where:

tfn = net thickness of flange, in mm.

5.7 Plated structures

5.7.1 Plated structures are those stiffened plate elements in contact with the shell and subject to ice loads.These requirements are applicable to an inboard extent which is the lesser of:

— web height of adjacent parallel web frame or stringer; or— 2.5 times the depth of framing that intersects the plated structure.

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5.7.2 The thickness of the plating and the scantlings of attached stiffeners shall be consistent with the endconnection requirements for supported framing as given in [5.9].

5.7.3 Plated structures subjected to direct ice loads, as defined in [4], shall be considered with respect to thebuckling requirements in Pt.3 Ch.8.

5.8 Stem and stern frames

5.8.1 For PC(6) or PC(7) ships requiring 1A*/1A equivalency, the stem and stern requirements of theFinnish-Swedish ice class rules may need to be additionally considered.

5.8.2 When the ship has a sharp edged stem, the thickness of the stem side plate within a breadth not lessthan 0.7 s, where s denotes the spacing of stiffening members, in m, shall not be less than 1.2 t, where tdenotes the required net shell plate thickness, in mm, for the bow area, as given in [5.1].The stem reinforcement shall be extending vertically from a line 1.5 m below the LIWL to the horizontal line xm above the UIWL, see the Figure 6.

Figure 6 Stem reinforcement

5.8.3 In ships with class notation PC(3) to PC(1), intended to operate under harsh ice condition, and oftype and size that may cause excessive beaching to occur, a forward ice knife may be required fitted. Thisrequirement will be based on consideration of design speed, stability and freeboard.

5.9 End connections for framing members

5.9.1 The end connection for framing members (stiffeners) exposed to ice loads, to supports, e.g. stringers,web frames, decks or bulkheads, shall be related to the response of the member when subjected to ice loads.The connection area is generally obtained through support members such as collar plate, lugs, end bracketsor web stiffener.

The total net connection area of support members, in cm2, is given as:

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where:

hi = effective dimension of connection area of member #i, in mmti = net thickness of connection area #i, in mmkτ = 1.0 for members where critical stress response is shear

= 1.5 for members where critical stress response is normal stressn = number of support members.

5.9.2 The net end connection area fitted, a, shall generally not be less than a0, in cm2, given as:

for longitudinal local frames

for transverse local frames

where:

AF = hull area factor from Table 6, Table 7 or Table 8PPF = peak pressure factor from Table 5Pavg = average pressure within load patch as given in [4.6.1], in MPaLH = load height, given as the smaller of b and (a-s), in mLL = load length, given as the smaller of w and (a-s), in ma = span of member as given in [5.2.5], in ms = spacing of frames (stiffeners), in mb, w = as given in [4.6.1]b1 = as given in [5.4.2]η = Permissible usage factor

= 0.9φw = smallest angle between shell plate and the web of the stringer or web frame as applicable, in

degrees, measured at the intersection with the stiffener. The angle φw may be taken as 90 degreesprovided the smallest angle is not less than 75 degrees.

5.9.3 For end connections of local supporting members (stiffeners), the leg thickness in mm of double filletwelds for the connection member i, to the web frame or load carrying stringer is given as the smaller of:

tleg =

= 0.7 ti

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where:

a = as given in [5.9.1]ao = as given in [5.9.2]ti = as built thickness of connection member i, in mmfyd = as given in Pt.3 Ch.13 Sec.1 [2.5.2]ts = corrosion addition/abrasion addition as given in [10.1.3], in mm.

The throat thickness not be less than as given in Pt.3 Ch.13 Sec.1 [2.5].

6 Longitudinal strength

6.1 Application

6.1.1 A ramming impact on the bow is the design scenario for the evaluation of the longitudinal strength ofthe hull.

6.1.2 Intentional ramming is not considered as a design scenario for ships which are designed with avertical or bulbous bow, see [1.3.4]. Hence the longitudinal strength requirements given in [6] shall not beconsidered for ships with stem angle γstem equal or larger than 80 degrees.

6.1.3 Ice loads shall only be combined with still water loads. The combined stresses shall be comparedagainst permissible bending and shear stresses at different locations along the ship’s length. In addition,sufficient local buckling strength shall also be verified.

6.2 Design vertical ice force at the bow

6.2.1 The design vertical ice force at the bow, in MN, shall be taken as:

FIB = minimum (FIB,1; FIB,2)

where:

FIB,1 = 0.534·KI0.15·sin0.2(γstem)·(Δkt ·Kh)

0.5·CFL , in MN

FIB,2 = 1.20·CFF , in MN

KI = indentation parameter = Kf / Kh

a) For the case of a blunt bow form:

Kf = (2·C·B1-eb / (1 + eb))0.9·tan(γstem)-0.9·(1 + eb)

b) For the case of wedge bow form (αstem < 80 deg), eb = 1 and the above simplifies to:

Kf = (tan(αstem) / tan2(γstem))0.9

Kh = 0.01·Awp , in MN/m.

CFL = longitudinal strength class factor from Table 3eb = bow shape exponent which best describes the water plane (see Figure 7 and Figure 8)

= 1.0 for a simple wedge bow form= 0.4 to 0.6 for a spoon bow form= 0 for a landing craft bow form

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An approximate eb determined by a simple fit is acceptable

γstem = stem angle to be measured between the horizontal axis and the stem tangent at the upper icewaterline, in degrees, (buttock angle as per Figure 2 measured on the centerline)

αstem = hull waterline angle to be measured at stem (centre line) at the UIWL, see Figure 2, in degreesC = 1 / (2·(LB / B)eb)

LB = bow length used in the equation y = B / 2·(x/LB)eb, in m, see Figure 7 and Figure 8

Δkt = ship displacement, in ktonnes, at UIWL, not to be taken less than 10 ktonnesAwp = ship water plane area, in m2

CFF = flexural failure class factor from Table 3.

Draught dependent quantities shall, where applicable, be determined at the waterline corresponding to theloading condition under consideration.

6.3 Design vertical shear force

6.3.1 The design vertical ice shear force along the hull girder, in MN, shall be taken as:FI = Cf · FIB

where:Cf = Longitudinal distribution factor to be taken as follows:

a) Positive shear force

Cf = 0.0 between the aft end of Li and 0.6 Li from aftCf = 1.0 between 0.9 Li from aft and the forward end of Li

b) Negative shear force

Cf = 0.0 at the aft end of Li

Cf = – 0.5 between 0.2 Li and 0.6 Li from aftCf = 0.0 between 0.8 Li from aft and the forward end of Li

where Li is ship length, in m, as defined in [6.4.1].

Intermediate values shall be determined by linear interpolation.

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Figure 7 Bow shape definition

Figure 8 Illustration of eb effect on the bow shape for B = 20 and LB = 16

6.3.2 The applied vertical shear stress, τa, shall be determined along the hull girder in a similar manner as inPt.3 Ch.5 Sec.1 by substituting the design vertical ice shear force for the design vertical wave shear force.

6.4 Design vertical ice bending moment

6.4.1 The design vertical ice bending moment along the hull girder, in MNm, shall be taken as:

MI = 0.1 · Cm · Li · sin-0.2(γstem) · FIB

where:

γstem is as given in [6.2.1]

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FIB = design vertical ice force at the bow, in MNCm = longitudinal distribution factor for design vertical ice bending moment to be taken as follows:

Cm = 0.0 at the aft end of Li

Cm = 1.0 between 0.5 Li and 0.7 Li from aftCm = 0.3 at 0.95 Li from aftCm = 0.0 at the forward end of Li

Li = ship length as defined in Pt.3 Ch.1 Sec.4, but measured on the upper ice waterline (UIWL), inm.Intermediate values shall be determined by linear interpolation.

Draught dependent quantities are, where applicable, to be determined at the waterline corresponding to theloading condition under consideration.

6.4.2 The applied vertical bending stress, σa, shall be determined along the hull girder in a similar manneras in Pt.3 Ch.5 Sec.1 by substituting the design vertical ice bending moment for the design vertical wavebending moment. The ship still water bending moment shall be taken as the maximum sagging moment.

6.5 Longitudinal strength criteria

6.5.1 The strength criteria provided in Table 10 shall be satisfied. The design stress shall not exceed thepermissible stress.

Table 10 Longitudinal strength criteria

Failure mode Applied stressPermissible stress when

ReH / Rm ≤ 0.7Permissible stress

when ReH / Rm > 0.7

Tension σa η·ReH η·0.41 (Rm + ReH)

Shear τa η·τeH η·0.41 (Rm + ReH) / (3)0.5

σa

σc for plating and for web plating of stiffeners

σc / 1.1 for stiffenersBuckling

τa τc

where:

σa = applied vertical bending stress, in N/mm2

τa = applied vertical shear stress, in N/mm2

ΡeH = specified minimum yield stress of the material, in N/mm2

Ρm = specified minimum tensile strength of material, in N/mm2

σc = critical buckling stress in compression, according to Pt.3 Ch.8, in N/mm2

τc = critical buckling stress in shear, according to Pt.3 Ch.8, in N/mm2

η = 0.8.

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7 Appendages

7.1 General

7.1.1 All appendages shall be designed to withstand forces appropriate for the location of their attachment tothe hull structure or their position within a hull area, as given below. For appendages of type or arrangementother than as considered in the following, the load definition and response criteria are subject to specialconsideration.

7.1.2 Stern frames, rudders and propeller nozzles shall be designed according to the rules given in Pt.3Ch.14 Sec.1.

7.1.3 Bilge keels are normally to be avoided and should preferably be substituted by roll-dampingequipment. If bilge keels are fitted, it is required that the connection to the hull is so designed that the risk ofdamage to the hull, in case the bilge keel is ripped off, is minimized.

7.1.4 Additional requirements for ice reinforced ships are given in the following. For ships with rudders whichare not located behind the propeller, special consideration will be made with respect to the longitudinal iceload.

7.2 Rudders

7.2.1 The rudder stock and upper edge of the rudder shall be effectively protected against ice pressure.

7.2.2 Rudder stops shall be provided. The design ice force on rudder shall be transmitted to the rudder stopswithout damage to the steering system.

7.2.3 Ice horn shall in general be fitted to protect the rudder in centre position. The ice horn shall extendbelow BWL. Design forces shall be determined according to the [12.5].

7.2.4 Ice horns shall be fitted directly abaft each rudder in such a manner that:

— the upper edge of the rudder is protected within two degrees to each side of the mid position when goingastern, and

— ice is prevented from wedging between the top of the rudder and the ship's hull.

The ice horn shall extend vertically to, minimum = 1.5 CFD , in m, below LIWL, where CFD shall be taken asgiven in Table 3. Alternatively an equivalent arrangement shall be arranged.

7.2.5 Exposed seals for rudder stock are assumed to be designed for the given environmental conditionssuch as:

— ice formation— specified design temperature.

7.3 Ice forces on rudder

7.3.1 The ice force, FU, acting on the uppermost part of the rudder, the ice horn included shall be assessedon a case to case basis based on the Society’s current practice.

The force FU shall be divided between rudder and ice horn according to their support position. The forceacting on the ice horn, in kN, may generally be taken as:

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where:

X = distance from leading edge of rudder to point of attack of the force F:= 0.5 ℓr minimum, in m= 0.67 ℓr maximum, in m

ℓr = length of rudder profile (including ice horn), in mXF = longitudinal distance, in m, from the leading edge of the rudder to the axis of the rudder stockXK = distance, in m, from leading edge of rudder to centre of ice horn.

For this loading the stress response of the rudder, the ice horn and support structures for these shall notexceed ReH, where ReH denotes the specified minimum yield stress of the material.

7.3.2 The ice force, FR, acting on the rudder the distance zLIWL below LIWL shall be assessed on a case tocase basis based on the Society’s current practice.

The rudder force, FR, in kN, gives rise to bending moments in the rudder, the rudder stock and the rudderhorn, as applicable. Alternative positions for the ice load area shall be considered in order that the maximumbending moment shall be determined.

The bending moment in way of the rudder section in question, in kNm, is given as:

MB = FR·hs

hs = vertical distance from the ice load area position to the rudder section in question, in m.

The rudder force, FR, gives rise to a rudder torque, MTR, and a bending moment in the rudder stock, MB,which both will vary depending on the position of the assumed ice load area, and on the rudder type andarrangement used.

In general the load giving the most severe combination of FR, MTR and MB with respect to the structure underconsideration shall be applied in a direct calculation of the rudder structure.

The design value of MTR is given by:

MTR = FR (0.6 ℓr – XF), in kNm= 0.15 FR ℓr minimum

XF = longitudinal distance, in m, from the leading edge of the rudder to the axis of the rudder stockℓr = length of rudder profile, in m.

7.4 Rudder scantlings

7.4.1 Scantlings of rudder, rudder stock, rudder horn and rudder stoppers, as applicable, shall be calculatedfor the force, F, given in [7.3.1] acting on the rudder and ice horn, with respect to bending and shear. Thenominal von Mises stress shall not exceed ReH, where ReH denotes the specified minimum yield stress of thematerial in N/mm2.

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7.4.2 The scantlings of rudders, rudder stocks and shafts, pintles, rudder horns and rudder actuators shall becalculated from the formulae given in Pt.3 Ch.14 Sec.1, inserting the rudder torque MTR, bending momentsMB and rudder force FR as given in [7.3.2].

7.4.3 Provided an effective torque relief arrangement is installed for the steering gear, and provided effectiveice stoppers are fitted, the design rudder torque need not be taken greater than:

M TR = MTRO

MTRO = steering gear relief torque, in kNm.

7.4.4 For rudder plating the ice load thickness shall be calculated as given in [5.1] for the stern area or lowerstern area as applicable.

7.5 Ice loads on propeller nozzles

7.5.1 The transverse ice force, FN, shall be calculated as outlined in [7.7].

7.5.2 The longitudinal ice force, FL, acting on the nozzle shall be assessed on a case to case basis based onthe Society’s current practice.For the determination of FL, the following two alternative ice load areas, A, shall be considered:

— an area positioned at the lower edge of the nozzle with width equal to 0.65 D and height equal to theheight of the nozzle profile, in m

— an area on both sides of the nozzle at the propeller shaft level, with transverse width equal to the heightof the nozzle profile in m and with height equal to 0.35 D. Both symmetric and asymmetric loading shallbe checked.

D = nozzle diameter, in m.

7.6 Propeller nozzle scantlings

7.6.1 The scantlings of the propeller nozzle and its supports in the hull shall be calculated for the ice loadsgiven in [7.5]. The nominal von Mises stress shall not exceed ReH, where ReH denotes the specified minimumyield stress of the material in N/mm2.For nozzle plating the ice load thickness shall be taken as given in [5.1] using the design ice pressure asgiven for the stern area, lower stern area as applicable.

7.7 Podded propulsors and azimuth thrusters

7.7.1 Ships operating in ice and equipped with podded propulsors or azimuth thrusters shall be designedaccording to operational mode and purpose stated in the design specification. If not given, it shall beassumed that the ship may operate longer periods in ice using astern running mode as part of its operationalprofile. When limitations are given, this information shall also be stated in the ship's papers.

7.7.2 Ramming astern is not anticipated.

7.7.3 Documentation of both local and global strength capacity of the pod/thruster shall be submitted forclass assessment. Recognised structural idealisation and calculation methods shall be applied.

7.7.4 Ice loads on pod/thruster body shall be assessed on a case by case basis based on the Society’scurrent practice.

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7.7.5 The nominal von Mises stress shall not exceed ReH, where ReH denotes the specified minimum yieldstress of the material in N/mm2.

8 Direct calculations

8.1 General

8.1.1 Direct calculations shall not be utilised as an alternative to the analytical procedures prescribed forshell plating and local frames.

8.1.2 Direct calculations shall be used for load carrying stringers and web frames forming a part of a grillagesystem.

8.1.3 Where direct calculation is used to check the strength of structural systems, the load patch specifiedin [4.5] shall not be combined with any other load. The load patch shall be applied at locations where thecapacity of these members under the combined effects of bending and shear is minimized. Special attentionshall be paid to lightening holes and cut-outs within the ice reinforced area.

8.1.4 The strength evaluation of the web frames and load carrying stringers may be performed basedon linear or non-linear analysis. Recognized structural idealization and calculations methods shall be inaccordance with Pt.3 Ch.7 Sec.1. In the strength evaluation, the guidance given in [8.1.5] and [8.1.6] maygenerally be considered.

8.1.5 If the structure is evaluated based on linear calculation methods, the following shall be considered:

1) Web plates and flanges elements in compression and shear to fulfil relevant buckling criteria as specifiedin Pt.3 Ch.8.

2) Nominal shear stresses in member web plates to be less than ReH / .3) Nominal von Mises stresses in member flanges to be less than 1.15 ReH.

8.1.6 If the structure is evaluated based on non-linear calculation methods, the following shall beconsidered:

1) The analysis shall reliably capture buckling and plastic deformation of the structure.2) The acceptance criteria are to ensure a suitable margin against fracture and major buckling and yielding

causing significant loss of stiffness.3) Permanent lateral and out-of-plane deformation of considered member are to be minor relative to the

relevant structural dimensions.4) Detailed acceptance criteria to be evaluated on case-by-case basis.

9 Welding

9.1 General

9.1.1 All welding within ice-strengthened areas shall be of the double continuous type.

9.1.2 Continuity of strength shall be ensured at all structural connections.

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9.2 Minimum weld requirements

9.2.1 The weld connection of local frames (stiffeners) and load carrying stringers and web frames supportinglocal frames to shell shall be as given in Pt.3 Ch.13 Sec.1 [2.5] with the weld factor, fweld, given as:

fweld = 0.31rw, minimum 0.26, for middle 60% of span= 0.52rw, minimum 0.43, at ends

rw = ratio of required net web area over fitted net web area for member considered. For transverse localframes, rw is, however, not to be taken less than:

where:

LLs = length of loaded portion of span, in m= lesser of a and (b - 0.5 s), in m

a = frame span as defined in [5.2.5], in mb = height of design ice load patch as given in [4.5], in ms = transverse frame spacing, in mAF = hull area factor from Table 6, Table 7 or Table 8PPFi = peak pressure factor from Table 5Pavg = average pressure within load patch as given in [4.6], in MPa.

9.2.2 Weld throat thickness need not be greater than 0.50 × as built thickness of the abutting plate.

10 Materials and corrosion protection

10.1 Corrosion/abrasion additions and steel renewal

10.1.1 Effective protection against corrosion and ice-induced abrasion is recommended for all externalsurfaces of the shell plating for polar class ships.

10.1.2 The values of corrosion/abrasion additions, ts, to be used in determining the shell plate thickness arelisted in Table 11.

Table 11 Corrosion/abrasion additions for shell plating

ts [mm]

With effective protection Without effective protection

Hull area PC(1)

PC(2)

PC(3)

PC(4)

PC(5)

PC(6)

PC(7)

PC(1)

PC(2)

PC(3)

PC(4)

PC(5)

PC(6)

PC(7)

Bow; bow intermediate ice belt 3.5 2.5 2.0 7.0 5.0 4.0

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ts [mm]

With effective protection Without effective protection

Hull area PC(1)

PC(2)

PC(3)

PC(4)

PC(5)

PC(6)

PC(7)

PC(1)

PC(2)

PC(3)

PC(4)

PC(5)

PC(6)

PC(7)

Bow intermediate lower; midbody and sternice belt 2.5 2.0 2.0 5.0 4.0 3.0

Midbody and stern lower; bottom 2.0 2.0 2.0 4.0 3.0 2.5

10.1.3 Polar class ships shall have a minimum corrosion/abrasion addition of ts = 1.0 mm applied to allinternal structures within the ice-strengthened hull areas, including plated members adjacent to the shell, aswell as stiffener webs and flanges. Additionally, the corrosion/abrasion addition, ts, shall not be less than tc asgiven in Pt.3 Ch.3 Sec.3.

10.1.4 Steel renewal for ice strengthened structures is required when the gauged thickness is less than tnet+ 0.5 mm.

10.2 Hull materials

10.2.1 Steel grades of plating for hull structures shall be not less than those given in Table 13 based on theas-built thickness, the PC class notation assigned to the ship and the material class of structural membersgiven in [10.2.2].

10.2.2 Material classes specified in Pt.3 Ch.3 Sec.1 are applicable to polar class ships regardless of the ship’slength. In addition, material classes for weather and sea exposed structural members and for membersattached to the weather and sea exposed shell plating of polar class ships are given in Table 12. Where thematerial classes in Table 12 and those in Pt.3 Ch.3 Sec.1 differ, the higher material class shall be applied.

Table 12 Material classes for structural members of polar ships

Structural members Materialclass

Shell plating within the bow and bow intermediate ice belt hull areas (B, BIi) II

All weather and sea exposed SECONDARY and PRIMARY, as defined in Pt.3 Ch.3 Sec.1 Table 3, structuralmembers outside 0.4 L amidships I

Plating materials for stem and stern frames, rudder horn, rudder, propeller nozzle, shaft brackets, ice skeg,ice knife and other appendages subject to ice impact loads II

All inboard framing members attached to the weather and sea-exposed plating including any contiguousinboard member within 600 mm of the plating I

Weather-exposed plating and attached framing in cargo holds of ships which by nature of their trade havetheir cargo hold hatches open during cold weather operations I

All weather and sea exposed SPECIAL, as defined in Pt.3 Ch.3 Sec.1 Table 3, structural members within 0.2 Lfrom FE II

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10.2.3 Steel grades for all plating and attached framing of hull structures and appendages situated below thelevel of 0.3 m below the lower waterline, as shown in Figure 9, shall be obtained from Pt.3 Ch.3 Sec.1 basedon the material class for structural members in Table 12 above, regardless of qualifier.

Figure 9 Steel grade requirements for submerged and weather exposed shell plating

Table 13 Steel grades for weather exposed plating 1)

Material class I Material class II Material class III

PC(1)through (5)

PC(6)and (7)

PC(1)through (5)

PC(6)and (7)

PC(1)through (3)

PC(4)and (5)

PC(6)and (7)

Thickness

t [mm]

MS HT MS HT MS HT MS HT MS HT MS HT MS HT

t ≤ 10 B AH B AH B AH B AH E EH E EH B AH

10 < t ≤ 15 B AH B AH D DH B AH E EH E EH D DH

15 < t ≤ 20 D DH B AH D DH B AH E EH E EH D DH

20 < t ≤ 25 D DH B AH D DH B AH E EH E EH D DH

25 < t ≤ 30 D DH B AH E EH 2) D DH E EH E EH E EH

30 < t ≤ 35 D DH B AH E EH D DH E EH E EH E EH

35 < t ≤ 40 D DH D DH E EH D DH F FH E EH E EH

40 < t ≤ 45 E EH D DH E EH D DH F FH E EH E EH

45 < t ≤ 50 E EH D DH E EH D DH F FH F FH E EH

Notes:

1) Includes weather-exposed plating of hull structures and appendages, as well as their outboard framing members,situated above a level of 0.3 m below the lowest ice waterline.

2) Grades D, DH are allowed for a single strake of side shell plating not more than 1.8 m wide from 0.3 m below thelowest ice waterline.

10.2.4 Steel grades for all weather exposed plating of hull structures and appendages situated above thelevel of 0.3 m below the lower ice waterline, as shown in Figure 9, shall be not less than given in Table 13.

10.2.5 Castings and forgings shall have specified properties consistent with the expected servicetemperature for the cast component. Forged or cast materials in structural members exposed to designtemperatures lower than 10°C, shall fulfil requirements given in Sec.3 Table 7 item C1001. The testtemperature of components fully exposed to the ambient air shall, if the design temperature has not beenspecified, for notations PC(1) to PC(5) be taken as -20ºC and for notations PC(6) and PC(7) as -10ºC.

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10.3 Materials for machinery components exposed to sea water

10.3.1 Materials exposed to sea water, such as propeller blades, propeller hub, cast thrusters body shallhave an elongation not less than 15% on a test specimen with a length which is five times the diameter oftest specimen.

10.3.2 Charpy V impact tests shall be carried out for materials other than bronze and austenitic steel.Average impact energy of 20 J taken from three Charpy V tests shall be obtained at −10ºC.

10.4 Materials for machinery components exposed to sea watertemperatures

10.4.1 Materials exposed to sea water temperature shall be of steel or other approved ductile material.

10.4.2 Charpy V impact tests shall be carried out for materials other than bronze and austenitic steel.An average impact energy value of 20 J taken from three tests shall be obtained at −10ºC. This requirementapplies to blade bolts, CP-mechanisms, shaft bolts, strut-pod connecting bolts, etc. This does not apply tosurface hardened components, such as bearings and gear teeth.

10.5 Materials for machinery components exposed to low air temperature

10.5.1 Materials of essential components exposed to low air temperature shall be of steel or other approvedductile material. An average impact energy value of 20 J taken from three Charpy V tests shall be obtainedat 10ºC below the lowest design temperature. This does not apply to surface hardened components, such asbearings and gear teeth.For definition of structural boundaries exposed to air temperature see [10.2.4].

11 Ice interaction loads – machinery

11.1 Propeller ice interaction

11.1.1 These rules cover open and ducted type propellers situated at the stern of a ship having controllablepitch or fixed pitch blades. Ice loads on bow propellers and pulling type propellers shall receive specialconsideration. The given loads are expected, single occurrence, maximum values for the whole ships servicelife for normal operational conditions. These loads do not cover off-design operational conditions, for examplewhen a stopped propeller is dragged through ice. These rules cover loads due to propeller ice interaction alsofor azimuth and fixed thrusters with geared transmission or integrated electric motor (geared and poddedpropulsors). However, the load models of these rules do not cover propeller/ice interaction loads when iceenters the propeller of a turned azimuthing thruster from the side (radially) or when ice block hits on thepropeller hub of a pulling propeller/thruster.

11.1.2 The loads given in this section are total loads (unless otherwise stated) during ice interaction andshall be applied separately (unless otherwise stated) and are intended for component strength calculationsonly.

11.1.3 Fb is a force bending a propeller blade backwards when the propeller mills an ice block while rotatingahead. Ff is a force bending a propeller blade forwards when a propeller interacts with an ice block whilerotating ahead.

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11.2 Ice class factors

11.2.1 Table 14 below lists the design ice thickness and ice strength index to be used for estimation of thepropeller ice loads.

Table 14 Ice class factors

Ice class Hice [m] Sice [-]

PC(1) 4.0 1.2

PC(2) 3.5 1.1

PC(3) 3.0 1.1

PC(4) 2.5 1.1

PC(5) 2.0 1.1

PC(6) 1.75 1

PC(7) 1.5 1

where:

Hice = ice thickness for machinery strength design, in mSice = ice strength index for blade ice force.

11.3 Design ice loads for open propeller11.3.1 Maximum backward blade force, in kNwhen D < Dlimit:

when D ≥ Dlimit:

Dlimit = 0.85 · Hice1.4 , in m.

where:

n = nominal rotational speed (at MCR free running condition) for CP-propeller and 85% of thenominal rotational speed (at MCR free running condition) for a FP-propeller (regardless drivingengine type), in rps

D = propeller diameter, in mEAR = expanded blade area ratioZ = number of propeller blades.

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Fb shall be applied as a uniform pressure distribution to an area on the back (suction) side of the blade forthe following load cases:

a) Load case 1: from 0.6 R to the tip and from the blade leading edge to a value of 0.2 chord lengthb) Load case 2: a load equal to 50% of the Fb shall be applied on the propeller tip area outside of 0.9 Rc) Load case 5: for reversible propellers a load equal to 60% of the greater of Fb or Ff, shall be applied from

0.6 R to the tip and from the blade trailing edge to a value of 0.2 chord length.

Table 15 Design ice load cases for maximum backward blade force for open propellers

Force Loaded area Right handed propellerblade seen from back

Load case 1 Fb

Uniform pressure applied on the back of theblade (suction side) to an area from 0.6 R tothe tip and from the leading edge to 0.2 timesthe chord length

Load case 2 50% of Fb

Uniform pressure applied on the back of theblade (suction side) on the propeller tip areaoutside of 0.9 R radius.

Load case 5

60% ofFf or Fb

which oneis greater

Uniform pressure applied on propeller face(pressure side) to an area from 0.6 R to thetip and from the trailing edge to 0.2 times thechord length

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11.3.2 Maximum forward blade force, in kNwhen D < Dlimit:

when D ≥ Dlimit:

where:

d = propeller hub diameter, in mD = propeller diameter, in mEAR = expanded blade area ratioZ = number of propeller blades.

Ff shall be applied as a uniform pressure distribution to an area on the face (pressure) side of the blade forthe following loads cases:

a) Load case 3: from 0.6 R to the tip and from the blade leading edge to a value of 0.2 chord lengthb) Load case 4: a load equal to 50% of the Ff shall be applied on the propeller tip area outside of 0.9 Rc) Load case 5: for reversible propellers a load equal to 60% of the greater of Ff or Fb shall be applied from

0.6 R to the tip and from the blade trailing edge to a value of 0.2 chord length.

Table 16 Design ice load cases for maximum forward blade force for open propellers

Force Loaded area Right handed propeller blade seen from back

Load case 3 Ff

Uniform pressure applied on the blade face(pressure side) to an area from 0.6 R to thetip and from the leading edge to 0.2 times thechord length.

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Force Loaded area Right handed propeller blade seen from back

Load case 4 50% of Ff

Uniform pressure applied on propeller face(pressure side) on the propeller tip areaoutside of 0.9 R radius.

Load case 5

60% ofFf or Fb

which oneis greater

Uniform pressure applied on propeller face(pressure side) to an area from 0.6 R to thetip and from the trailing edge to 0.2 times thechord length

11.3.3 Maximum blade spindle torque, Qsmax

Spindle torque Qsmax around the spindle axis of the blade fitting shall be calculated both for the load casesdescribed in [11.3.1] and [11.3.2] for FbFf. If these spindle torque values are less than the default valuegiven below, the default minimum value, in kNm, shall be used:Default value: Qsmax = 0.25 Fc0.7

where:c0.7 = length of the blade chord at 0.7 R radius, in m.F is either Fb or Ff which ever has the greater absolute value.

11.3.4 Maximum propeller ice torque, in kNm, applied to the propeller

when D < Dlimit:

where:

kopen = 14.7 for PC(1) - PC(5); andkopen = 10.9 for PC(6) - PC(7)

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when D ≥ Dlimit:

Dlimit = 1.8·Hice, in m.

where:

P0.7 = propeller pitch at 0.7 R, in mn = rotational propeller speed, in rps, at bollard condition. If not known, n shall be taken as shown in

Table 17.

Table 17 Rotational propeller speed, n, at bollard condition

Propeller type n

CP propellers nn



where nn is the nominal rotational speed at MCR, free running condition.

For CP propellers, propeller pitch,P0.7 shall correspond to MCR in bollard condition. If not known, P0.7 shall betaken as 0.7 P0.7n, where P0.7n is propeller pitch at MCR free running condition.

11.3.5 Maximum propeller ice thrust, in kN, applied to the shaft:Thf = 1.1 Ff

Thb = 1.1 Fb

However, the load models of this UR do not include propeller/ice interaction loads when ice block hits on thepropeller hub of a pulling propeller.

11.4 Design ice loads for ducted propeller

11.4.1 Maximum backward blade force, in kN:when D < Dlimit:

when D ≥ or equal Dlimit:

where Dlimit = 4 Hice, in m.n shall be taken as in [11.3.1].Fb shall be applied as a uniform pressure distribution to an area on the back side for the following load cases:

a) Load case 1: On the back of the blade from 0.6 R to the tip and from the blade leading edge to a valueof 0.2 chord length.

b) Load case 5: For reversible rotation propellers a load equal to 60% of the greater of Fb or Ff is applied onthe blade face from 0.6R to the tip and from the blade trailing edge to a value of 0.2 chord length.

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Table 18 Design ice load cases for maximum backward blade force for ducted propellers


Load case 1 Fb

Uniform pressure applied on the backof the blade (suction side) to an areafrom 0.6 R to the tip and from theleading edge to 0.2 times the chordlength

Load case 560% of Ff orFb which one isgreater

Uniform pressure applied on propellerface (pressure side) to an area from0.6 R to the tip and from the trailingedge to 0.2 times the chord length

11.4.2 Maximum forward blade force, in kN:when D ≤ Dlimit:

when D > Dlimit:

where:

Ff shall be applied as a uniform pressure distribution to an area on the face (pressure) side for the followingload case:

a) Load case 3: On the blade face from 0.6 R to the tip and from the blade leading edge to a value of 0.5chord length.

b) Load case 5: A load equal to 60% of the greater of Ff or Fb shall be applied from 0.6 R to the tip andfrom the blade leading edge to a value of 0.2 chord length.

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Table 19 Design ice load cases for maximum forward blade force for ducted propellers


Load case 3 Ff

Uniform pressure applied on the bladeface (pressure side) to an area from 0.6R to the tip and from the leading edgeto 0.5 times the chord length.

Load case 560% of Ff or Fb

which one isgreater

Uniform pressure applied on propellerface (pressure side) to an area from 0.6R to the tip and from the trailing edgeto 0.2 times the chord length

11.4.3 Maximum blade spindle torque for CP-mechanism design, Qsmax. Spindle torque Qsmax around thespindle axis of the blade fitting shall be calculated for the load case described in [11.1]. If these spindletorque values are less than the default value given below, in kNm, the default value shall be used: DefaultValue: Qsmax = 0.25 Fc0.7 where c0.7 the length of the blade section at 0.7 R radius and F is either Fb or Ffwhich ever has the greater absolute value.

11.4.4 Maximum propeller ice torque applied to the propeller

Tmax is the maximum torque on a propeller due to ice-propeller interaction, in kNm.

when D ≤ Dlimit:

where:

kducted = 10.4 for PC(1) - PC(5); andkducted = 7.7 for PC(6) - PC(7)

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when D > Dlimit:

where Dlimit = 1.8 Hice, in m.

n is the rotational propeller speed, in r.p.s., at bollard condition. If not known, n shall be taken as shown inTable 20.

Table 20 Rotational propeller speed, n, at bollard condition

Propeller type n

CP propellers nn



where nn is the nominal rotational speed at MCR, free running condition.

For CP propellers, propeller pitch,P0.7 shall correspond to MCR in bollard condition. If not known, P0.7 shall betaken as 0.7 P0.7n, where P0.7n is propeller pitch at MCR free running condition.

11.4.5 Maximum propeller ice thrust (applied to the shaft at the location of the propeller), in kN:Thf = 1.1 Ff

Thb = 1.1 Fb

11.5 Propeller blade loads and stresses for fatigue analysis11.5.1 Blade stressesThe blade stresses at various selected load levels for fatigue analysis shall be taken proportional to thestresses calculated for maximum loads given in sections [11.3.1], [11.3.2], [11.4.1] and [11.4.2].The peak stresses are those determined due to Ff and Fb. The peak load range ΔFmax and the maximum loadamplitude FAmax are determined from:

The corresponding maximum stress range Δσmax and maximum stress amplitude σAmax are calculated fromthese loads.

11.6 Design ice loads for propulsion line

11.6.1 TorqueThe propeller ice torque excitation for shaft line dynamic analysis shall be described by a sequence of bladeimpacts which are of half sine shape and occur at the blade. The torque due to a single blade ice impact as afunction of the propeller rotation angle, in kNm, is then defined as:

T(ϕ) = CqTmax sin(ϕ(180/αi))

when ϕ rotates from 0 to αi plus integer revolutions

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T(ϕ) = 0

when ϕ rotates from αi to 360 plus integer revolutions

where Cq and αi parameters are given in Table 21.

Table 21 Propeller ice torque parameters

Torque excitation Propeller-ice interaction Cq αi



Case 3 Two ice blocks with 45 degree phase in rotation angle 0.5 45

The total ice torque is obtained by summing the torque of single blades taking into account the phase shift360 deg/Z. The number of propeller revolutions during a milling sequence shall be obtained with the formula:

NQ = 2 Hice

and total number of impacts during one ice milling sequence is:

In addition, the impacts shall ramp up over 270 degrees and subsequently ramp down over 270 degrees. Thetotal excitation torque from the 3 cases will then look like the figures below. See Figure 10.

Rules for classification: S

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IP Pt.6 Ch.6. Edition January 2017

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Part 6 Chapter 6 Section 5

Case 1 Case 2 Case 3

Figure 10 The shape of the propeller ice torque excitation for 90, 135 degrees single blade impact sequences and 45degrees double blade impact sequence (Case 1 to 3 respectively apply for propeller with 4 blades)

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Milling torque sequence duration is not valid for pulling bow propellers, which are subject to specialconsideration.

11.6.2 Response torque in the propulsion systemThe response torque, Tr(t) at any component in the propulsion system shall be analysed by means oftransient torsional vibration analysis considering the excitation torque at the propeller T(ϕ) as given in[11.6.1], the actual available engine torque Te, and the mass elastic system. Calculations have to be carriedout for all excitation cases given in [11.6.1] and the excitation torque has to be applied on top of the meanhydrodynamic torque in bollard condition at considered propeller rotational speed. The worst phase anglebetween the ice interactions and any high torsional vibrations caused by engine excitations (e.g. 4th orderengine excitation in direct coupled 2-stroke plants with 7-cyl. engine) should be considered in the analysis.

Guidance note:A recommended way of performing transient torsional vibration calculations is given in class guideline, DNVGL-CG-0041.Alternative methods to the ones given in class guideline, DNVGL-CG0041 may also be considered on the basis of equivalence.


The results of the 3 cases shall be used in the following way:

1) The highest peak torque (between the various lumped masses in the system) is in the following referredto as peak torque Tpeak.

2) The highest torque amplitude during a sequence of impacts shall be determined as half of the range frommax to min torque and is referred to as TAmax.

Figure 11 Response torque over time

11.6.3 Maximum response thrust ThrMaximum thrust along the propeller shaft line shall be calculated with the formulae below. The factors 2.2and 1.5 take into account the dynamic magnification due to axial vibration. Alternatively the propeller thrustmagnification factor may be calculated by dynamic analysis.

Maximum shaft thrust forwards, in kN: Thr = Thn + 2.2 Thf

Maximum shaft thrust backwards, in kN: Thr = 1.5 Thb

Thn = propeller bollard thrust, in kN

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Thf = maximum forward propeller ice thrust, in kN.

If hydrodynamic bollard thrust, Thn is not known, Thn shall be taken as shown in Table 22 below:

Table 22 Hydrodynamic bollard thrust, Thn

Propeller type Thn

CP propellers (open) 1.25 Th

CP propellers (ducted) 1.1 Th

FP propellers driven by turbine or electric motor Thr

FP propellers driven by diesel engine (open) 0.85 Th

FP propellers driven by diesel engine (ducted) 0.75 Th

Th = nominal propeller thrust at MCR at free running open water conditions.

11.6.4 Blade failure load for both open and nozzle propeller, Fex

The force is acting at 0.8R in the weakest direction of the blade at the centre of the blade. For calculationof spindle torque the force is assumed to act at a spindle arm of 1/3 of the distance from the axis of bladerotation to the leading or the trailing edge, whichever is greater.The blade failure load, in kN, is:

where σref = 0.6σ0.2 + 0.4σu

where σu (specified maximum ultimate tensile strength) and σ0.2 (specified maximum yield or 0.2% proofstrength) are representative values for the blade material. Representative in this respect means values forthe considered section. These values may either be obtained by means of tests, or commonly acceptedthickness correction factors approved by the classification society. If not available, maximum specified valuesshall be used.c, t, D and r are respectively the actual chord length (m), thickness (m), propeller diameter (m) and radius(m) of the cylindrical root section of the blade at the weakest section outside root fillet and typically will be atthe termination of the fillet into the blade profile.Alternatively the Fex can be determined by means of FEA of the actual blade. Blade bending failure shall takeplace reasonably close to the root fillet end and normally not more 20% of R outside fillet. The blade bendingfailure is considered to occur when von Mises stress reach σref1 times 1.5 in elastic model.

Guidance note:A recommended FE analysis method is given in class guideline, DNVGL-CG-0041.Alternative methods to the ones given in class guideline, DNVGL-CG-0041, may also be considered on the basis of equivalence.


11.7 Machinery fastening loading conditions

11.7.1 Essential equipment and main propulsion machinery supports shall be suitable for the accelerationsas indicated in as follows. Accelerations shall be considered acting independently.

11.7.2 Longitudinal impact accelerations, al

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Maximum longitudinal impact acceleration, in m/s2, at any point along the hull girder:

11.7.3 Vertical acceleration, av

Combined vertical impact acceleration, in m/s2, at any point along the hull girder:

FX = 1.3 at F.E.= 0.2 at midships= 0.4 at A.E.= 1.3 at A.E. for ships conducting ice breaking astern.


11.7.4 Transverse impact acceleration at

Combined transverse impact acceleration, in m/s2, at any point along hull girder:

FX = 1.5 at F.E.= 0.25 at midships= 0.5 at A.E.= 1.5 at A.E. for ships conducting ice breaking astern, intermediate values to be interpolated linearly

where:

φ = maximum friction angle between steel and ice, normally taken as 10°, in degreesγ = bow stem angle at waterline, in degreesΔtk = displacement at UIWL, in ktonnesH = distance, in m, from the water line to the point being consideredFIB = vertical impact force, defined in [6.2]FBow = as defined in [4.5.1].

12 Design – machinery

12.1 Design principles12.1.1 Fatigue design in generalThe propeller and shaft line components shall be designed so as to prevent accumulated fatigue failure whenconsidering the loads according to [11.3] through [11.6] using the linear elastic Palmgren-Miner’s rule.

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The long term ice load spectrum is approximated with two-parameter Weibull distribution.

12.1.2 Propeller bladesThe load spectrum for backward loads is normally expected to have a lower number of cycles than the loadspectrum for forward loads. Taking this into account in a fatigue analysis introduces complications that arenot justified considering all uncertainties involved.

The blade stress amplitude distribution is therefore simplified and assumed to be as:

where the Weibull shape parameter is, k = 0.75 for open propeller and k = 1.0 for nozzle propeller

This is illustrated in the cumulative stress spectrum (stress exceedence diagram) in Figure 12.

Number of load cycles Nice in the load spectrum per blade shall be determined according to the formula:

where:

Nclass = reference number of load impacts for each ice class

Ice class PC(1) PC(2) PC(3) PC(4) PC(5) PC(6) PC(7)

Nclass 21 × 106 17 × 106 15 × 106 13 × 106 11 × 106 9 × 106 6 × 106

k1 = 1 for centre propeller= 2 for wing propeller= 3 for pulling propeller (wing and centre)= for pulling bow propellers number of load cycles is expected to increase in range of 10 times

k2 = 0.8 - f when f < 0

= 0.8 - 0.4·f when 0 ≤ f ≤ 1= 0.6 - 0.2·f when 1 < f ≤ 2.5= 0.1 when f > 2.5

where the immersion function f is:

where:

ho = depth of the propeller centreline at the minimum ballast waterline in ice (LIWL) of the ship, in m.

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12.1.3 Applicable loads in propulsion line componentsThe strength of the propulsion line components shall be designed

a) for maximum loads in [11.3] and [11.4] (for open and ducted propellers respectively)b) such that the plastic bending of a propeller blade shall not cause damages in other propulsion line

componentsc) with fatigue strength as determined by the criteria in [12.5] with the following ice load spectrum

The Weibull shape parameter is k = 1.0 for both open and ducted propeller torque and bending forces. Theload distribution is an accumulated load spectrum (load exceedence diagram).

This is illustrated by the example in the Figure 13.

Figure 12 Ice load distribution for ducted and open propeller

Figure 13 The total number of load cycles in the load spectrum is determined as: Z·Nice

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12.2 Propeller blade design12.2.1 Maximum blade stressesBlade stresses (equivalent and principal stresses) shall be calculated using the backward and forward loadsgiven in section [11.3] and [11.4]. The stresses shall be calculated with recognised and well documented FE-analysis.

Guidance note:A recommended FE analysis method is given in class guideline DNVGL-CG-0041. Alternative methods to the ones given in classguideline, DNVGL-CG-0041, may also be considered on the basis of equivalence.


The stresses on the blade shall not exceed the allowable stresses σall for the blade material given below.

Calculated blade equivalent stress for maximum ice load shall comply with the following:

σcalc < σall = σref /S

S = 1.5σref = reference stress, defined as:σref = 0.7σu orσref = 0.6σ0.2 + 0.4σu whichever is less

where σu and σ0.2 are minimum specified values for the blade material according to approved maker’sspecification.

12.3 Fatigue design of propeller blades

12.3.1 Propeller blades shall be designed so as to prevent accumulated fatigue when considering the loadsaccording to [12.1.2] and using the Miner’s rule.

Guidance note:A recommended fatigue analysis method is given in class guideline DNVGL-CG-0041. Alternative methods to the ones given inclass guideline, DNVGL-CG-0041, may also be considered on the basis of equivalence.


12.3.2 The S-N curve characteristics are based on two slopes, the first slope 4.5 is from 100 to 108 loadcycles; the second slope 10 is above 108 load cycles.

— The maximum allowable stress is limited by σref/S— The fatigue strength σFat-E7 is the fatigue limit at 10 million load cycles.

The geometrical size factor (Ksize) is:

Where t = actual blade thickness at considered section and a is given in Table 23The mean stress effect (Kmean) is:

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The fatigue limit for 10 million load cycles is then:

where S is the safety factor S = 1.5The S-N curve is extended by using the first slope (4.5) to 100 million load cycles due to the variable loadingeffect (stress interaction effect).

Table 23 Mean fatigue strength σFat-E7 for different material types

Bronze and brass (a = 0.10) Stainless steel (a = 0.05)

Mn-Bronze, CU1 (high tensile brass) 80 MPa Ferritic (12Cr 1Ni) 120 MPa

Mn-Ni-Bronze, CU2 (high tensile brass) 80 MPa Martensitic (13Cr 4Ni/13Cr 6Ni) 150 MPa

Ni-Al-Bronze, CU3 120 MPa Martensitic (16Cr 5Ni) 165 MPa

Mn-Al-Bronze, CU4 105 MPa Austenitic (19Cr 10Ni) 130 MPa

Alternatively, σFat-E7 can be defined from fatigue test results from approved fatigue tests at 50% survivalprobability and stress ratio R = -1, see Pt.4 Ch.5 Sec.1 [2.1.1].

12.4 Blade flange, bolts and propeller hub and CP Mechanism

12.4.1 The blade bolts, the cp mechanism, the propeller boss, and the fitting of the propeller to the propellershaft shall be designed to withstand the maximum and fatigue design loads, as defined in I. The safety factoragainst yielding shall be greater than 1.3 and that against fatigue greater than 1.5. In addition, the safetyfactor for loads resulting from loss of the propeller blade through plastic bending as defined in [11.6.4] shallbe greater than 1 against yielding.

Guidance note:A recommended fatigue analysis method is given in class guideline, DNVGL-CG-0041. Alternative methods to the ones given inclass guideline, DNVGL-CG-0041, may also be considered on the basis of equivalence.


12.4.2 Blade bolts shall withstand following bending moment, in kNm, considered around bolt pitch circle, oran other relevant axis for not circular joints, parallel to considered root section with a safety factor of 1.0:

where:rbolt = radius to the bolt plan, in m.

12.4.3 Blade bolt pre-tension shall be sufficient to avoid separation between mating surfaces withmaximum forward and backward ice loads in [11.3.1] - [11.3.2] and [11.4.1] - [11.4.2] (open and ductedrespectively).

12.4.4 Separate means, e.g. dowel pins, have to be provided in order to withstand a spindle torque resultingfrom blade failure ([11.6.4]) Qsex or ice interaction Qsmax ([11.3.3]), whichever is greater. A safety factor S of1.0 is required. The minimum diameter of the pins, in mm, shall be taken as:

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where:

PCD = pitch circle diameter, in mmi = number of pinsQs = max(Qsmax; Qsex ) − Qfr1 − Qfr2, in kNm

σ0.2 = yield strength of dovel pin material

Qsex = , in kNm

Qfr1 = friction torque in blade bearings caused by the reaction forces due to Fex

Qfr2 = friction between connected surfaces resulting from blade bolt pretension forcesℓex = maximum of distance from spindle axis to the leading, or trailing edge at radius 0.8RCoefficient offriction

= 0.15 may normally be applied in calculation of Qfr1,2.

12.4.5 Components of CP mechanisms shall be designed to withstand the blade failure spindle torque Qsexand maximum ice spindle torque.The blade failure spindle torque, Qsex , shall not lead to any consequential damages.Fatigue strength shall be considered for parts transmitting the spindle torque from blades to a servo systemconsidering ice spindle torque acting on one blade. The maximum amplitude, in kNm, is defined as:

Provided that calculated stresses duly considering local stress concentrations are less than yield strength,or maximum 70% of σu of respective materials, detailed fatigue analysis is not required. In opposite casecomponents shall be analysed for cumulative fatigue.

12.4.6 Design pressure for servo system shall be taken as a pressure caused by Qsmax or Qsex when notprotected by relief valves, reduced by relevant friction losses in bearings caused by the respective ice loads.Design pressure shall in any case be less than relief valve set pressure.

12.5 Propulsion line components12.5.1 Propeller fitting to the shaftA. Keyless cone mounting

The friction capacity (at 0°C) shall be at least 2.0 times the highest peak torque Tpeak, in kNm, as determinedin [11.6] without exceeding the permissible hub stresses.

The necessary surface pressure, in MPa, can be determined as:

where:

μ = 0.14 for steel-steel= 0.13 for steel-bronze

DS = shrinkage diameter at mid-length of taper, in mℓ = effective length of taper, in m.

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Above friction coefficients may be increased by 0.04 if glycerine is used in wet mounting

B. Key mounting

Key mounting is not permitted.

C. Flange mounting

I = The flange thickness shall be at least 25% of the shaft diameter.II = Any additional stress raisers such as recesses for bolt heads shall not interfere with the flange fillet

unless the flange thickness is increased correspondingly.III = The flange fillet radius shall be at least 10% of the shaft diameter.IV = The diameter of ream fitted (light press fit) bolts shall be chosen so that the peak torque does not

cause shear stresses beyond 30% of the yield strength of the bolts.V = The bolts shall be designed so that the blade failure load Fex ([11.6.4]) does not cause yielding.

12.5.2 Propeller shaftThe propeller shaft shall be designed to fulfill the following:

A. The blade failure load Fex ([11.6.4]) applied parallel to the shaft (forward or backwards) shall not causeyielding. Bending moment need not to be combined with any other loads.The diameter in way of the aft sterntube bearing, in mm, shall not be less than:

where:

σy = minimum specified yield or 0.2% proof strength of the propeller shaft material, in MPad = shaft diameter, in mmdi = shaft inner diameter, in mm.

Forward from the aft stern tube bearing the diameter may be reduced based on direct calculation of actualbending moments, or by the assumption that the bending moment caused by Fex is linearly reduced to 50%at the next bearing and in front of this linearly to zero at third bearing.

Bending due to maximum blade forces Fb and Ff have been disregarded since the resulting stress levels aremuch below the stresses due to the blade failure load.

B. The stresses due to the peak torque Tpeak, in kNm, shall have a minimum safety factor of 1.5 againstyielding in plain sections and 1.0 in way of stress concentrations in order to avoid bent shafts. Minimumdiameter, in mm, of:

plain shaft:

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notched shaft:

where αt is the local stress concentration factor in torsion. Notched shaft diameter shall in any case not beless than the required plain shaft diameter.

C. The torque amplitudes with the foreseen number of cycles shall be used in an accumulated fatigueevaluation with the safety factors as defined below.

Guidance note:A recommended fatigue analysis method is given in class guideline, DNVGL-CG-0041, with further references to the DNVGL-CG-0038. Alternative methods to the ones given in class guideline, DNVGL-CG-0041, may also be considered on the basis ofequivalence.


D. For plants with reversing direction of rotation the stress range Δτ·αt, in MPa, resulting from forward Tpeakfto astern Tpeakb shall not exceed twice the yield strength (in order to avoid stress-strain hysteresis loop), inMPa, with a safety factor of 1.5, i.e.:

The fatigue strengths σF and τF (3 million cycles) of shaft materials may be assessed on the basis of thematerial’s yield or 0.2% proof strength, in MPa, as:

This is valid for small polished specimens (no notch) and reversed stresses, see VDEH 1983 Bericht Nr. ABF11Berechnung von Wöhlerlinien für Bauteile aus Stahl.

The high cycle fatigue (HCF) shall be assessed based on the above fatigue strengths, notch factors (i.e.geometrical stress concentration factors and notch sensitivity), size factors, mean stress influence and therequired safety factor of 1.5.

The low cycle fatigue (LCF) representing 103 cycles shall be based on the lower value of either half of thestress range criterion (see D) or the smaller value of yield or 0.7 of tensile strength/√3. Both criteria utilise asafety factor of1.5.

The LCF and HCF as given above represent the upper and lower knees in a stress-cycle diagram. Since therequired safety factors are included in these values, a Miner sum of unity is acceptable.

12.5.3 Intermediate shaftsThe intermediate shafts shall be designed to fulfil the following:A. The stresses due to the peak torque Tpeak, in kNm, shall have a minimum safety factor of 1.5 againstyielding in plain sections and 1.0 in way of stress concentrations in order to avoid bent shafts. Minimumdiameter, in mm, of:

plain shaft:

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notched shaft:

where αt is the local stress concentration factor in torsion. Notched shaft diameter shall in any case not beless than the required plain shaft diameter.B. The torque amplitudes with the foreseen number of cycles shall be used in an accumulated fatigueevaluation with the safety factors as defined below.



C. For plants with reversing direction of rotation the stress range Δτ·αt, in MPa, resulting from forward Tpeakfto astern Tpeakb shall not exceed twice the yield strength (in order to avoid hysteresis), in MPa, with a safetyfactor of 1.5, i.e.:

The fatigue strengths σF and τF (3 million cycles) of shaft materials may be assessed on the basis of thematerial’s yield or 0.2% proof strength, in MPa, as:

This is valid for small polished specimens (no notch) and reversed stresses, see VDEH 1983 Bericht Nr. ABF11Berechnung von Wöhlerlinien für Bauteile aus Stahl.The high cycle fatigue (HCF) shall be assessed based on the above fatigue strengths, notch factors (i.e.geometrical stress concentration factors and notch sensitivity), size factors, mean stress influence and therequired safety factor of 1.5.The low cycle fatigue (LCF) representing 103 cycles shall be based on the lower value of either half of thestress range criterion (see C) or the smaller value of yield or 0.7 of tensile strength/√3. Both criteria utilise asafety factor of 1.5.The LCF and HCF as given above represent the upper and lower knees in a stress-cycle diagram. Since therequired safety factors are included in these values, a Miner sum of unity is acceptable.

12.5.4 Shaft connectionsA. Shrink fit couplings (keyless)

The friction capacity shall be at least 1.8 times the highest peak torque Tpeak as determined in [11.6.2]without exceeding the permissible hub stresses.

The necessary surface pressure, in MPa, can be determined as:

where:

μ = coefficient of friction = 0.14 for steel to steel with oil injection (= 0.18 if glycerine injection)DS = is the shrinkage diameter at mid-length of taper, in mℓ = is the effective length of taper, in m.

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B. Key mounting

Key mounting is not permitted.

C. Flange mounting

I = The flange thickness shall be at least 20% of the shaft diameter.II = Any additional stress raisers such as recesses for bolt heads shall not interfere with the flange fillet

unless the flange thickness is increased correspondingly.III = The flange fillet radius shall be at least 8% of the shaft diameter.IV = The diameter of ream fitted (light press fit) bolts or pins shall be chosen so that the peak torque does

not cause shear stresses beyond 30% of the yield strength of the bolts or pins.V = The bolts shall be designed so that the blade failure load ([11.6.4]) in backwards direction does not

cause yielding.

12.5.5 Gear transmissionsA. ShaftsShafts in gear transmissions shall meet the same safety level as intermediate shafts, but where relevant,bending stresses and torsional stresses shall be combined, e.g. by von Mises.



Maximum permissible deflection in order to maintain sufficient tooth contact pattern shall be considered forthe relevant parts of the gear shafts.B. GearingThe gearing shall fulfil following 3 acceptance criteria:

1) tooth root fracture2) pitting of flanks3) scuffing.

In addition to above 3 criteria subsurface fatigue may need to be considered.Common for all criteria is the influence of load distribution over the face width. All relevant parametersshall be considered, such as elastic deflections (of mesh, shafts and gear bodies), accuracy tolerances, helixmodifications, and working positions in bearings (especially for twin input single output gears).The load spectrum (see [12.1.3]) may be applied in such a way that the numbers of load cycles for theoutput wheel are multiplied by a factor of (number of pinions on the wheel/number of propeller blades Z).For pinions and wheels with higher speed the numbers of load cycles are found by multiplication with thegear ratios. The peak torque, Tpeak, is also to be considered.

Guidance note:The acceptance criteria for calculation assessment are given below. They refer to calculation methods as given in class guideline,DNVGL-CG-0036, comprising information on calculation of tooth root strength (root fractures), flank surface durability (pitting,spalling, case crushing and tooth fractures starting from the flank), scuffing and subsurface fatigue.Alternative methods to the ones given in class guideline, DNVGL-CG-0036, may also be considered on the basis of equivalence.


Tooth root safety shall be assessed against the peak torque, torque amplitudes (with the pertinent averagetorque) as well as the ordinary loads (free water running) by means of accumulated fatigue analyses. Theresulting safety factor shall be at least 1.5.The safety against pitting shall be assessed in the same way as tooth root stresses, but with a minimumresulting safety factor of 1.2.

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The scuffing safety (flash temperature method – see class guideline, DNVGL-CG-0036) based on the peaktorque shall be at least 1.2 when the FZG class of the oil is assumed one stage below specification.The safety against subsurface fatigue of flanks for surface hardened gears (oblique fracture from active flankto opposite root) shall be assessed at the discretion of each society.C. BearingsSee section [12.5.9].

12.5.6 ClutchesClutches shall have a static friction torque of at least 1.3 times the peak torque and dynamic friction torque2/3 of the static.Emergency operation of clutch after failure of e.g. operating pressure shall be made possible withinreasonably short time. If this is arranged by bolts, it shall be on the engine side of the clutch in order toensure access to all bolts by turning the engine.

12.5.7 Elastic couplingsThere shall be a separation margin of at least 20% between the peak torque and the torque where any twistlimitation is reached.The torque amplitude (or range Δ) shall not lead to fatigue cracking, i.e. exceeding the permissible vibratorytorque. The permissible torque may be determined by interpolation in a log-log torque-cycle diagram whereTKmax1 respectively ΔTKmax refer to 50,000 cycles and TKV refer to 106 cycles. See illustration in Figure 14,Figure 15 and Figure 16.

Figure 14

Figure 15

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Figure 16

12.5.8 CrankshaftsSpecial considerations apply for plants with large inertia, e.g. flywheel, tuning wheel or PTO, in the non-driving end of the engine.

12.5.9 BearingsAll shaft bearings shall be designed to withstand the propeller blade ice interaction loads according to [11.3]and [11.4]. For the purpose of calculation the shafts are assumed to rotate at rated speed. Reaction forcesdue to the response torque, e.g. in gear transmissions, shall be considered.Additionally the aft stern tube bearing as well as the next shaft-line bearing shall withstand Fex as given in[11.6], in such a way that the ship can maintain operational capability.Rolling bearings shall have a L10a lifetime of at least 40 000 hours according to ISO-281.Thrust bearings and their housings shall be designed to withstand maximum response thrust [11.6] and theforce resulting from the blade failure force Fex. For the purpose of calculation except for Fex the shafts areassumed to rotate at rated speed. For pulling propellers special consideration shall be given to loads from iceinteraction on propeller hub.

12.5.10 SealsBasic requirements for seals:A. Seals shall prevent egress of pollutants, and be suitable for the operating temperatures. Contingency plansfor preventing the egress of pollutants under failure conditions shall be documented.B. Seal shall be of type approved type or otherwise of proven design.

12.6 Azimuth main propulsion

12.6.1 In addition to the above requirements, special consideration shall be given to those loading caseswhich are extraordinary for propulsion units when compared with conventional propellers. The estimationof loading cases has to reflect the way of operation of the ship and the thrusters. In this respect, forexample, the loads caused by the impacts of ice blocks on the propeller hub of a pulling propeller have to beconsidered. Furthermore, loads resulting from the thrusters operating at an oblique angle to the flow have tobe considered. The steering mechanism, the fitting of the unit, and the body of the thruster shall be designedto withstand the loss of a blade without damage. The loss of a blade shall be considered for the propellerblade orientation which causes the maximum load on the component being studied. Typically, top-down bladeorientation places the maximum bending loads on the thruster body.

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12.6.2 Azimuth thrusters shall also be designed for estimated loads due to thruster body/ice interaction asper sub-section E. The thruster body has to stand the loads obtained when the maximum ice blocks, whichare given in [11.2.1], strike the thruster body when the ship is at a typical ice operating speed. In addition,the design situation in which an ice sheet glides along the ship’s hull and presses against the thruster bodyshould be considered. The thickness of the sheet should be taken as the thickness of the maximum ice blockentering the propeller, as defined in [11.2].

12.6.3 Design criteria for azimuth propulsorsAzimuth propulsors shall be designed for following loads:

1) Ice pressure on strut based on defined location area of the strut/ice interaction as per [12.5].2) Ice pressure on pod based on defined location area of thruster body/ice interaction as per subsection

[12.5].3) Plastic bending of one propeller blade in the worst position (typically top-down) without consequential

damages to any other part.4) Steering gear design torque, in kNm, shall be minimum 60% of steering torque expected at propeller ice

milling condition defined as Tmax

TSG = 0.6(Tmax / 0.8R) ℓwhere ℓ is distance from the propeller plane to steering (azimuth) axis, in m.

5) Steering gear shall be protected by effective means limiting excessive torque caused by:

a) ice milling torque exceeding design torque and leading to rotation of unitb) torque caused by plastic bending of one propeller blade in the worse position (related to steering

gear) and leading to rotation of the unit.

6) Steering gear shall be ready for operation after above load, 5)a) or 5)b) has gone.

12.7 Steering system

12.7.1 The effective holding torque of the rudder actuator, at safety valve set pressure, is obtained bymultiplying the open water requirement at design speed (maximum 18 knots) by following factors:

Ice class PC(1) PC(2) PC(3) PC(4) PC(5) PC(6) PC(7)

Factor 5 5 3 3 3 2 1.5

The holding torque shall be limited to the actual twisting capacity of the rudder stock calculated at its yieldstrength (see Pt.4 Ch.10)

12.7.2 The rudder actuator shall be protected by torque relief arrangements, assuming the following turningspeeds [deg/s] without undue pressure rise (see Pt.4 Ch.10 for undue pressure rise):

Ice class PC(1) and PC(2) PC(3) to PC(5) PC(6) and PC(7)

Turning speeds [deg/s] 8 6 4

12.7.3 Additional fast acting torque relief arrangements (acting at 15% higher pressure than set pressureof safety valves in [12.7.2] shall provide effective protection of the rudder actuator in case of the rudder ispushed rapidly hard over against the stops assuming following turning speeds [deg/s].

Ice class PC(1) and PC(2) PC(3) to PC(5) PC(6) and PC(7)

Turning speeds [deg/s] 40 20 10

The arrangement shall be so that steering capacity can be speedily regained.

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12.8 Prime movers

12.8.1 Engines shall be capable of being started and running the propeller in bollard condition.

12.8.2 Propulsion plants with CP propeller shall be capable being operated even in case with the CP systemin full pitch as limited by mechanical stoppers.

12.8.3 Provisions shall be made for heating arrangements to ensure ready starting of the cold emergencypower units at an ambient temperature applicable to the polar class of the ship.

12.8.4 Emergency power units shall be equipped with starting devices with a stored energy capability of atleast three consecutive starts at the design temperature in [11.1] above The source of stored energy shall beprotected to preclude critical depletion by the automatic starting system, unless a second independent meansof starting is provided. A second source of energy shall be provided for an additional three starts within 30min., unless manual starting can be demonstrated to be effective.

12.9 Auxiliary systems

12.9.1 Machinery shall be protected from the harmful effects of ingestion or accumulation of ice or snow.Where continuous operation is necessary, means should be provided to purge the system of accumulated iceor snow.

12.9.2 Means should be provided to prevent damage due to freezing, to tanks containing liquids.

12.9.3 Vent pipes, intake and discharge pipes and associated systems shall be designed to prevent blockagedue to freezing or ice and snow accumulation.

12.10 Sea inlets, cooling water systems and ballast tanks

12.10.1 Cooling water systems for machinery that are essential for the propulsion and safety of the ship,including sea chests inlets, shall be designed for the environmental conditions applicable to the ice class.

12.10.2 At least two sea chests shall be arranged as ice boxes for class PC(1) to PC(5) inclusive. Thecalculated volume for each of the ice boxes shall be at least 1 m3 for every 750 kW of the total installedpower. For PC(6) and PC(7) there shall be at least one ice box located preferably near centre line.

12.10.3 Ice boxes shall be designed for an effective separation of ice and venting of air.

12.10.4 Sea inlet valves shall be secured directly to the ice boxes. The valve shall be a full bore type.Guidance note:Butterfly valves are not considered to be full bore type valves.


12.10.5 Ice boxes and sea bays shall have vent pipes and shall have shut off valves connected direct to the shell.

12.10.6 Means shall be provided to prevent freezing of sea bays, ice boxes, ship side valves and fittingsabove the load water line.

12.10.7 Efficient means shall be provided to re-circulate cooling seawater to the ice box. Total sectional areaof the circulating pipes shall not be less than the area of the cooling water discharge pipe.

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12.10.8 Detachable gratings or manholes shall be provided for ice boxes. Manholes shall be located abovethe deepest load line. Access shall be provided to the ice box from above.

12.10.9 Openings in ship sides for ice boxes shall be fitted with gratings, or holes or slots in shell plates.The net area through these openings shall be not less than 5 times the area of the inlet pipe. The diameterof holes and width of slot in shell plating shall be not less than 20 mm. Gratings of the ice boxes shall beprovided with a means of clearing. Clearing pipes shall be provided with screw-down type non return valves.

12.11 Ballast tanks

12.11.1 Efficient means shall be provided to prevent freezing in fore and after peak tanks and wing tankslocated above the water line and where otherwise found necessary.

Guidance note:Acceptable solutions for prevention of freezing can be air bubbling system. For tanks located fully or partly above the water line orlower ice water line (LIWL), whichever is lower, heat balance calculations may be provided in lieu of anti freezing arrangements


12.12 Ventilation systems

12.12.1 The air intakes for machinery and accommodation ventilation shall be located on both sides of theship.

12.12.2 Accommodation and ventilation air intakes shall be provided with means of heating.

12.12.3 The temperature of inlet air provided to machinery from the air intakes shall be suitable for the safeoperation of the machinery

12.13 Alternative design

12.13.1 As an alternative, a comprehensive design study may be submitted and may be requested to bevalidated by an agreed test programme.

13 Stability and watertight integrity

13.1 General

13.1.1 Ships with a length LLL of 24 meters and above and class notation PC(7) to PC(1) shall complywith the requirements of Pt.3 Ch.15 and IMO Resolution A.1024(26) Guidelines for Ships Operating in PolarWaters Chapter 3 Subdivision and Stability as well as the requirements of this subsection.

13.1.2 For ships with PC(6) and PC(7) not carrying any polluting or hazardous cargoes, damage may beassumed to be confined between watertight bulkheads, except where such bulkheads are spaced at less thanthe damage dimension.

13.2 Intact stability

13.2.1 The initial metacentric height GM shall not be less than 0.5 m.

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13.3 Requirements to watertight integrity

13.3.1 As far as practicable, tunnels, ducts or pipes which may cause progressive flooding in case ofdamage, shall be avoided in the damage penetration zone. If this is not possible, arrangements shall bemade to prevent progressive flooding to volumes assumed intact. Alternatively, these volumes shall beassumed flooded in the damage stability calculations.

13.3.2 The scantlings of tunnels, ducts, pipes, doors, staircases, bulkheads and decks, forming watertightboundaries, shall be adequate to withstand pressure heights corresponding to the deepest equilibriumwaterline in damaged condition.

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APPENDIX A GUIDELINES FOR STRENGTH ANALYSIS OF THEPROPELLER BLADE USING FINITE ELEMENT METHOD

1 Guidelines for strength analysis of the propeller blade using finiteelement method

1.1 Requirements for finite element model

1.1.1 The objective of the stress analysis of ice-strengthened propeller blades shall make sure that thedesigned propeller blade has an acceptable margin of safety against both ultimate and fatigue strength at thedesign loads.The typical locations on the propeller blades at which the highest stresses caused by ice loads occur are thefillet at the root of the blade in the case of all propeller types and the section next to the tip load area in thecase of skewed propellers.The requirement for the finite element model is that it is able to represent the complex curvilinear geometryand the thickness variation of the blade and also the geometry of the fillet at the root of the blade, in orderto represent the complex three-dimensional stress state of the structure and to represent the local peakstresses needed to assess the fatigue strength of the structure with acceptable accuracy. The load of thepropeller blade is dominated by bending, leading to non-constant stress distribution over the thickness of theblade. The model should also be able to represent the stress distribution over the thickness of the blade.A conventional stress analysis approach to propeller blades utilising beam theory, although capable of dealingwith warping stresses, or an approach utilising coarse shell elements with a rough representation of thethickness variation of the blade do not lead to acceptable accuracy in the stress analyses of ice-strengthenedpropeller blades.

1.2 Good engineering practice for finite element analysis

1.2.1 The use of solid elements is highly recommended for determining the stress distribution of thepropeller blades. The use of a very dense parabolic tetrahedron mesh is recommended. Parabolic hexahedronsolid elements may also be used, but hexahedra require considerably greater modelling effort. Linearelements and, especially, linear tetrahedrals should not be used in stress analysis.As a rule of thumb, a minimum of two parabolic solid elements should be used over the thickness of theblade in the thinnest regions of the blade. Near the root region of the blade, where the geometry changesrapidly, the element size used should be chosen to be such that the local peak stress used in the fatigueassessment is obtained with good accuracy.Additional geometric details which have a significant effect on the maximum peak stress at the root filletshould also be taken into account in the model, e.g. bolt holes located close to the root fillet. Well-shapedelements are a prerequisite for the stress analyses. The element formulation to be used should be chosen soas to be such that no locking, hour-glassing etc. phenomena occur.A typical parabolic tetrahedron mesh of a propeller blade used in the verification studies is presented inFigure 1 as an example.

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Figure 1 A typical parabolic tetrahedron mesh of a propeller blade

Shell elements may be used in the stress analyses of propeller blades, but the accuracy of the modellingapproach has to be proven by measurements or extensive verification calculations covering the thickness,dimensional, and geometrical variations of the propeller blade product range to be manufactured. Forexample, extreme sizes and an adequate number of intermediate sizes of the propeller blade productrange should be used in verification calculations or measurements. The peak stress obtained using theshell element approach has to be within acceptable accuracy and the boundary conditions shall not causesignificant disturbance in the peak stresses. The root fillet geometry has to be considered in the peak stressstate used in the stress analysis. The modelling of the tip region is difficult. Thus, it is allowed, for example,to finish discretisation at the 0.975 chord and to make an artificial chord at the tip. The shell elementformulation to be used should be chosen so as to be such that no locking, hour-glassing etc. phenomenaoccur.

1.3 Boundary conditions

1.3.1 The boundary conditions of the blade model should be given at an adequate distance from the peakstress location in order to ensure that the boundary condition has no significant effect on the stress field usedin the stress analysis.

1.4 Applied pressure loads

1.4.1 The pressure loads applied on the finite element model can be given either in the normal direction ofthe curved blade surface or alternatively as a directional pressure load. The normal pressure approach - seeFigure 2 - leads to a loss of the net applied transversal load as a result of the highly curved surface near theedge of the propeller blade.Whichever approach is used, it should be ensured that the total force determined in the particular load caseis applied on the model. In the normal pressure case, this can be done by scaling the load or, alternatively,by scaling the resulting stresses.The directional pressure is better suited to propeller blade stress analyses. The pressure can be given on asurface in a direction defined using, for example, a local coordinate system; see Figure 3.

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Figure 2 First alternative. One possible way to apply the pressure load to the propeller blade. Ifthe pressure load is given in the normal direction of the highly curved blade surface, the resultingnet applied load will be less than the intended load and should be scaled appropriately.

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Figure 3 Second alternative. If the pressure load is given in a fixed direction, the net applied loadis directly the intended load.

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CHANGES – HISTORIC

July 2016 editionThis document supersedes the October 2015 edition.

Main changes July 2016, entering into force 1 January 2017

• Sec.2 Ice strengthening for the northern Baltic - Ice— Sec.2 [7.1.2]: A requirement for the restricted engine output in ice to be included in the Appendix to

Classification Certificate is added.— Sec.2 [7.3.1]: The machinery output used in the formula for K1 is corrected with use of PS instead of Pmin,

which is in line with the Finnish - Swedish maritime authorities for Baltic ice operations

• Sec.5 Polar class - PC— Sec.5 [3.2.1]: In Figure 1 the word "max" is replaced with "min" in the extension of Stern ice belt area,

i.e. the new extension is 0.7b min 0.15L.

October 2015 editionThis is a new document.The rules enter into force 1 January 2016.

Amendments 1 January 2016

• Sec.2 Ice strengthening for the Northern Baltic - Ice— [7.1]: Re-arranged and moved rules for minimum engine output in [15.1] to be a part of subsection [7]

"Design loads".

• Sec.5 Polar class - PC— [4.7.3]: Prescriptive requirements for hull area factors (AF) were missing for ships with thrusters/podded

propulsion operating astern. Table 5 is containing the new hull area factors.— [4.8]: The requirement to clients to define the ice thickness hice has been replaced with prescriptive

ice compression class factors which represents expected ice thicknesses for the different Polar Classnotations. Allowable limits for normal, shear and von Mises stresses have been implemented as well.

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