dnvgl ru ship pt5ch2

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FOREWORD

DNV GL rules for classification contain procedural and technical requirements related to obtaining

and retaining a class certificate. The rules represent all requirements adopted by the Society as

basis for classification.

© DNV GL AS October 2015

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

If any person suffers loss or damage which is proved to have been caused by any negligent act or omission of DNV GL, then DNV GL shall

pay compensation to such person for his proved direct loss or damage. However, the compensation shall not exceed an amount equal to ten

times the fee charged for the service in question, provided that the maximum compensation shall never exceed USD 2 million.

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.



Rules for classification: Ships — DNVGL-RU-SHIP-Pt5Ch2. Edition October 2015

Container ships

DNV GL AS

CHANGES – CURRENT

This is a new document.

The rules enter into force 1 January 2016.




Container ships

DNV GL AS

CONTENTS

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

Section 1 General....................................................................................................... 8

1 Introduction............................................................................................8

1.1 Introduction.........................................................................................8

1.2 Scope................................................................................................. 8

1.3 Application.......................................................................................... 8

1.4 Class notations.................................................................................... 8

1.5 Definitions...........................................................................................9

2 Documentation and certification...........................................................10

2.1 Documentation requirements............................................................... 102.2 Certification requirements....................................................................11

Section 2 Structural design principles......................................................................12

1 General................................................................................................. 12

2 Materials...............................................................................................12

Section 3 Loads........................................................................................................ 13

1 General................................................................................................. 13

2 Hull girder loads...................................................................................13

2.1 Still water hull girder loads................................................................. 13

3 Loading condition................................................................................. 13

3.1 Standard design loading conditions.......................................................13

Section 4 Hull girder strength..................................................................................14

1 General................................................................................................. 14

2 Vertical hull girder bending strength....................................................14

2.1 Harbour/sheltered water operation....................................................... 14

3 Vertical hull girder shear strength........................................................14

3.1 Harbour/sheltered water operation....................................................... 14

Section 5 Hull local scantlings..................................................................................151 General................................................................................................. 15

2 Primary supporting members............................................................... 15

2.1 Prescriptive requirements.................................................................... 15

3 Special requirements............................................................................ 16

3.1 Wave breakers...................................................................................16




Container ships

DNV GL AS

Section 6 Finite element analysis.............................................................................17

1 General................................................................................................. 17

2 Cargo hold finite element analysis........................................................17

2.1 Application.........................................................................................172.2 Scope............................................................................................... 17

2.3 Design load combinations....................................................................17

2.4 Acceptance criteria............................................................................. 20

3 Fuel oil deep tank finite element analysis............................................ 20

3.1 Application.........................................................................................20

3.2 Scope............................................................................................... 20

3.3 Modelling principles............................................................................ 20


3.5 Acceptance criteria............................................................................. 24

Section 7 Fatigue......................................................................................................25

1 General................................................................................................. 25

1.1 Scope............................................................................................... 25

2 Prescriptive fatigue strength calculations.............................................25

2.1 Longitudinal stiffener end connections...................................................25

2.2 Welded details in the upper part of the hull girder.................................. 25

2.3 Knuckles and discontinuities in the upper part of the hull girder................26

Section 8 Container securing arrangement.............................................................. 27

1 General................................................................................................. 271.1 Container securing arrangements......................................................... 27

1.2 Container securing structures.............................................................. 27

2 Stowage of containers on deck.............................................................28

2.1 General............................................................................................. 28

2.2 Stowage on deck with neither lashing nor lateral rigid support..................28

2.3 Stowage on deck with lashing but without lateral rigid support................. 29

2.4 Stowage on deck with lateral rigid support............................................ 30

3 Stowage of containers below deck....................................................... 31

3.1 Stowage below deck in cell guides....................................................... 31

4 Loads acting on containers...................................................................32

4.1 General.............................................................................................32

4.2 Wind loads........................................................................................ 33

4.3 Transverse forces............................................................................... 34

4.4 Longitudinal forces............................................................................. 36

4.5 Vertical forces....................................................................................36




Container ships

DNV GL AS

5 Design load combinations for container securing arrangements........... 37


6 Design load combinations for container securing structures.................38

6.1 General............................................................................................. 38

6.2 Design load combinations for lashing bridge.......................................... 39

6.3 Design load combinations for cell guide.................................................39

6.4 Design load combinations for container stanchions..................................39

7 Acceptance criteria............................................................................... 40

7.1 Acceptance criteria for container securing arrangements..........................40

7.2 Permissible forces for container securing structures................................ 40

8 Strength evaluation.............................................................................. 41

8.1 Strength evaluation of container securing arrangements..........................41

8.2 Strength evaluation of container securing structures............................... 41

9 Lashing computer system.....................................................................42

9.1 Application.........................................................................................42

9.2 Definition...........................................................................................42

9.3 Approval and certification process........................................................ 42

9.4 Hardware approval............................................................................. 42

9.5 Software approval.............................................................................. 42

9.6 Certification....................................................................................... 44

Section 9 Hull support structures for container support fittings and containersecuring structures...............................................................................................46

1 General................................................................................................. 46

1.1 Objective...........................................................................................46

2 General requirements........................................................................... 46

2.1 Strength evaluation............................................................................ 46

2.2 Structure arrangement........................................................................46

3 Design loads.........................................................................................46

3.1 General.............................................................................................46

3.2 Hull support structures for container support fittings...............................46

3.3 Hull support structures for container securing structures..........................47

4 Strength evaluation.............................................................................. 47

4.1 General.............................................................................................47

Section 10 Application of thick steel plates and additional requirements for steelstrength group VL47.............................................................................................48

1 General................................................................................................. 48

1.1 Application.........................................................................................48

2 Application of thick steel plates........................................................... 48




Container ships

DNV GL AS

2.1 General............................................................................................. 48

2.2 Brittle crack arrest design................................................................... 49

2.3 Non-destructive testing (NDT) during construction..................................51

2.4 Measures for thick steel plates.............................................................51

3 Additional requirements for steel strength group VL47........................ 52

3.1 General............................................................................................. 52

3.2 Fatigue..............................................................................................53

3.3 NDT..................................................................................................55

4 Enhanced non destructive testing of welds...........................................55

4.1 Application.........................................................................................55

4.2 Magnetic particle testing procedure...................................................... 55

4.3 Ultrasonic testing procedure................................................................ 55




Container ships

DNV GL AS

SECTION 1 GENERAL

1 Introduction

1.1 Introduction

This chapter applies to ships intended for the carriage of containers.

1.2 Scope

The rules in this chapter include requirements regarding hull strength and the relevant proceduralrequirements.

The requirements shall be regarded as supplementary to those given in rules for the assignment of mainclass.

1.3 Application

These rules shall be applied to sea-going ships exclusively intended for the carriage of containers having thefollowing characteristics:

— equipped with fixed stowage appliance in the form of cell guides at the bulkheads

— fixed container foundations on the inner bottom

— fixed appliances for stowage and lashing on the upper deck and/or hatch covers.

The transport of other cargo, i.e. break bulk on the inner bottom, may be accepted on a case by case basis.The transport of dry cargo in bulk is not permitted.

1.4 Class notations

1.4.1 Ship type notation

Ships built in compliance with the requirements as specified in Table 1 will be assigned the ship type notation

as follows:

Table 1 Ship type notation for container ships

Class notation Description Design requirements, rule references

Container shipShip exclusively intended for

the carriage of containers

1.4.2 Additional notations

The following additional notations, as specified in Table 2, are typically applied to ships with ship typenotation Container ship and partly true for ships with the additional notation Container.

Table 2 Additional notations

Class notation Description Application Rule reference

RSD Requirements for global finite element

strength analysis

Ships with the notation

Container ship

Pt.6 Ch.1 Sec.8




Container ships

DNV GL AS

Class notation Description Application Rule reference

WIV Fatigue and ultimate hull girder verified

under explicit consideration of wave induced

vibrations (whipping and springing)


Container ship

Pt.6 Ch.1 Sec.11

RCP Refrigerated container stowage positions Ships with the notations

Container ship or

Container

Pt.6 Ch.4 Sec.9

RSCS Route specific container stowage for ships

intended to carry containers on a specified

sea route

Ships with the notations

Container ship or

Container

Pt.6 Ch.4 Sec.11

Hatchcoverless For hatchcoverless container ships equipped

with the appropriate facilities


Container ship

Pt.6 Ch.5 Sec.2

DG Arrangement for carriage of dangerous goods

in packed form

All ships Pt.6 Ch.5 Sec.10

Safelash Increased safety level for crew members

and stevedores engaged in the handling andsecuring of containers

Ships with the notations

Container ship orContainer

Pt.6 Ch.8 Sec.3

For a full definition of all class additional notations, see Pt.1 Ch.2 Sec.1.

1.5 Definitions

For definitions not defined in this section, see Pt.3 Ch.1 Sec.4 [3].

Definitions for container ships are given in Table 3.

Table 3 Definitions

Terms Definition

container freight container according ISO Standard, or other specially approved container.

container stack containers which are stacked vertically and secured horizontally by stackers, lashings, etc.

container block a number of stacks interconnected and secured horizontally by bridges stackers or double

stacking cones.

container securing

devicescontainer securing equipment and container support fittings.

container securing

equipment

loose container securing devices for securing and supporting of containers (e.g. twistlocks,

midlocks, stackers, turnbuckles, lashing rods).

container support fittings

fixed container securing devices for securing and supporting of containers welded to

tank tops, decks, bulkheads or hatch covers (e.g. raised ISO-foundations, flush/weld in

foundations, lashing eye plates, D-rings, guide fittings).

container wall ends the transverse end of the container constructed as a closed wall.

container door ends the transverse end of the container constructed with doors for access.

lateral rigid supports

members serving securing arrangements so that the stiffness of the containers does not

influence on support forces and internal forces in containers (e.g. cross ties, cell guides and

buttress).




Container ships

DNV GL AS

Terms Definition

container securing

structures

structures taking container support forces not being an integral part of the hull structures

(e.g. cell guides, lashing bridges and stanchions).

cell guides an arrangement in holds or on deck of fixed vertical guide rails for support of containers.

self-supporting cell guide cell guides which are not attached to transverse bulkheads.

lashing bridges framed structures on deck where lashings are secured.

stanchion pillar type structures on deck for support of outermost container stack.

container free end free end of 20ft. containers stowed in 40 ft cell guides.

safe working load, SWL the safe working load certified for container securing devices, based on testing or calculations.

minimum breaking load the tested minimum breaking strength of a container securing device.

lashing computer systemcomputer based system for calculation and control of container securing arrangements for

compliance with applicable strength requirements.

2 Documentation and certification

2.1 Documentation requirements

2.1.1 Container ships

The Builder shall submit the documentation required by Table 4.The documentation will be reviewed by theSociety as a part of the class contract. This table is partly applicable for ships with the additional notationContainer.

Table 4 Documentation requirements

Object Documentation type Additional description Info

H050 - Structural drawing

Cell guides, container stanchions and

lashing brigges, including

— nominal cell guide / container

clearance

AP

H050 - Structural drawingSupporting structures for cell guides,

container stanchions and lashing bridgesAP

H190 - Container securing

arrangement planAP

Cargo securing arrangement

Z030 Arrangement plan

Lashing bridges, including

— lashing eye arrangement

— force plan— access plan

AP

I270 – Test conditions AP

I280 – Reference data FILashing computer system

software

Z161 – Operational manual FI




Container ships

DNV GL AS

Object Documentation type Additional description Info

AP = For approval; FI = For information

ACO = As carried out; L = Local handling; R = On request; TA = Covered by type approval; VS = Vessel specific

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.

2.2 Certification requirements

2.2.1

Products shall be certified as required by Table 5.

Table 5 Certification requirements

Object Certificate type Issued by Certification

standard* Additional description

Container support fittings PC Society DNVGL-CP-0068Container SecuringDevices

Container securing

equipmentPC Society

DNVGL-CP-0068Container Securing

Devices

Cell guides MC Society

Lashing bridges MC Society

Container stanchions MC Society

Lashing computer PC SocietySee Sec.8 [9] for requirements for

certification

* Unless otherwise specified the certification standard is the rules.

PC = Product Certificate, MC = Material certificate

For general certification requirements, see Pt.1 Ch.3 Sec.4. For a definition of the certification types, see Pt.1Ch.3 Sec.5.




Container ships

DNV GL AS

SECTION 2 STRUCTURAL DESIGN PRINCIPLES

1 General

The structural design principles shall be according to Pt.3 Ch.3 except those requirements given in thissection.

2 Materials

Within 0.6 L amidships, the longitudinal stiffeners in way of uppermost strake of longitudinal bulkhead,sheer strake, upper deck and hatch side coaming shall have the same strength group as the plating they areattached to. The material for the longitudinal stiffeners in this area are to satisfy one material class lowerthan the class required for the attached plate.




Container ships

DNV GL AS

SECTION 3 LOADS

1 General

The static and dynamic loads shall be according to Pt.3 Ch.4 except for those requirements given in thissection.

2 Hull girder loads

2.1 Still water hull girder loadsGuidance note:

When determining the required section modulus of the midship section of container ships in the range x/L = 0.3 to x/L = 0.55

it is recommended to use at least the following initial value for the hogging still water bending moment, in kNm:

M SW,ini = n1 · c w · L2 · B(0.123 – 0.015c B)

where

n1 = factor to take into account the total mass of 20 ft containers (TEU) the ship can carry, taken as:

with n1 ≤ 1.2

n = maximum number of 20 ft containers (TEU) of the mass G, in t, the ship can carry

G = 14 t.

The initial hogging still water bending moment M SW,ini should be graduated regularly to ship's ends.

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

3 Loading condition

3.1 Standard design loading conditions

3.1.1 General

The standard design loading conditions given in this sub-section shall be considered in addition to thestandard loading conditions given in Pt.3 Ch.4 Sec.8 [1].

3.1.2 Seagoing design loading conditions

The following seagoing design loading conditions shall be included in the loading manual:

— homogeneous cargo loading conditions at maximum draught

— homogeneous cargo loading conditions at maximum draught with one 40 ft container bay empty

— homogeneous cargo loading conditions at design draught when different from maximum draught

— ballast loading conditions. No cargo shall be loaded in such conditions.

Guidance note:

For operational flexibility, it is recommended to consider the following loading conditions:

— loading condition with maximum stack weights at the aft/forward ends of the ships

— transversely asymmetrical cargo loading conditions at maximum draught.





Container ships

DNV GL AS

SECTION 4 HULL GIRDER STRENGTH

1 General

The hull girder strength assessment shall be carried out in accordance with Pt.3 Ch.5. Additional hull girderstrength requirements are provided in the following sub-sections.

2 Vertical hull girder bending strength

2.1 Harbour/sheltered water operation

2.1.1 Permissible hull girder bending capacity for harbour/sheltered water operations

The permissible hull girder bending moments for all loading conditions for harbour/sheltered operations inhogging and sagging shall comply with Pt.3 Ch.5 Sec.2 [1.7], applying a correction factor:

3 Vertical hull girder shear strength

3.1 Harbour/sheltered water operation

3.1.1 Permissible hull girder shear force capacity for harbour/sheltered water operations

The positive and negative permissible hull girder shear forces for all loading conditions for harbour/shelteredoperations in hogging and sagging shall comply with Pt.3 Ch.5 Sec.2 [2.3], applying a correction factor:




Container ships

DNV GL AS

SECTION 5 HULL LOCAL SCANTLINGSSymbols

For symbols not defined in this section, refer to Pt.3 Ch.1 Sec.4 [2].

1 General

The hull local scantlings shall be calculated according to Pt.3 Ch.6 and Pt.3 Ch.10. Additional local strengthrequirements are provided in the following sub-sections.

2 Primary supporting members

2.1 Prescriptive requirements

2.1.1 Application

The requirements given in [2.1.2] to [2.1.4] shall be applied regardless of required scantlings obtained fromdirect strength analysis.

2.1.2 Thickness of double bottom centre girder

The net thickness, t m, in mm, of the centre girder shall not be less than:

where

h = depth, in mm, of the centre girder, to be taken as:

h = 350 + 45 · ℓ with h ≥ 600

ha = as built depth, in mm, of centre girder

ℓ = unsupported span of the floor plates, in m, to be taken equal to the distance between longitudinalside bulkheads, however not less than ℓ ≥ 0.8 B.

2.1.3 Thickness of double bottom side girder

The net thickness t m, in mm, of the side girders shall not be taken less than:

where

ha

= as built depth, in mm, of side girders.

2.1.4 Minimum net thickness of non-tight transverse structures in way of bench structure and non-tightlongitudinal bulkhead.

The net thickness shall not be taken less than the required minimum thickness for non-tight bulkhead asgiven in Pt.3 Ch.6 Sec.3 [1.1.1]




Container ships

DNV GL AS

3 Special requirements

3.1 Wave breakers

3.1.1 If containers are intended to be carried above the weather deck at a location forward of 0.15 L fromF.E. a wave breaker shall be fitted in accordance with the requirements given in Pt.3 Ch.10 Sec.6 [10].




Container ships

DNV GL AS

SECTION 6 FINITE ELEMENT ANALYSIS

1 General

Finite element analysis shall be carried out according to general assumptions, methodology and requirementsfor the finite element analysis given in Pt.3 Ch.7 and according to methods and procedures given in theSociety's document DNVGL-CG-0127, Finite element analysis, unless otherwise specified in this section.

2 Cargo hold finite element analysis

2.1 Application

Cargo hold finite element analysis shall be carried out for the midship region and applied for one hold withtypical hold arrangement.

2.2 Scope

The cargo hold finite element analysis in midship region shall be used to assess the structural adequacy of allprimary supporting members.

Guidance note:

The evaluation of the yield and buckling criteria is of particular importance for the following structural members:

— inner bottom

— outer bottom

— double bottom girders

— double bottom floors

— vertical girders of the transverse bulkheads.


2.3 Design load combinations2.3.1 Design load combinations as given in Table 1 are based on typical cargo hold arrangements, i.e., two40 ft bays are arranged in each cargo hold and one non-watertight support transverse bulkhead is arrangedin between the two bays. The loading patterns are illustrated in Table 1.

If cargo hold arrangements are different from the above assumption, the design load conditions shall beagreed with the Society.




Container ships

DNV GL AS

2.3.2 The design load combinations as given in Table 1 are required for cargo hold finite element analysis.If more severe container loading conditions exist, such conditions combined with critical dynamic load casesshall be agreed with the Society and shall be included in the analysis.

Table 1 Standard design load combinations for cargo hold finite element analysis

No. DescriptionLoading pattern

Aft Mid Fore

Container Weights and

Tank Content Draught

% of

perm.

SWBM

% of

perm.

SWSF

Dynamic

load case

Seagoing conditions

LC140 ft

Heavy(1)

on deck: max 40 ft

stack weight

in hold: 30.5 t/FEU not

exceeding max 40 ft

stack weight

all tanks empty

T sc 100%

(hog.)

≤

100%

HSM-2

HSA-2

FSM-2

BSR-1P

BSP-1P

LC240 ft

Light(1)

on deck: 90% of max

40 ft stack weight not

exceeding 17 t/FEU

in hold:

16t/FEU

all tanks empty

T sc 100%

(hog.)

≤

100%

HSM-2

HSA-2

FSM-2

BSR-1P

BSP-1P

LC420 ft

Heavy(1)

on deck: max 20 ft

stack weight if mixed

stowage is applicable,

max 20 ft + 40 ft stack

weight

in hold:

24t/TEU not exceeding

max 20 ft stack weight

all tanks empty

0.9T sc

100%

(sag.

or min.

hog.)

≤

100%

HSM-1

HSA-1

FSM-1

BSR-1P

BSP-1P




Container ships

DNV GL AS


Aft Mid Fore



% of

perm.

SWBM

% of

perm.

SWSF

Dynamic

load case

LC5

heavy

deck light

hold(1)

on deck: max 20 ftstack weight, if mixed


max 20 ft + 40 ft stack

weight

in hold: 16 t/FEU

all tanks empty

0.9T sc

100%

(sag.

or min.

hog.)

≤

100%

HSM-1

HSA-1

FSM-1

BSR-1P

BSP-1P

LC6 Pitching(1)

on deck: max 20 ft

stack weight, if mixed


max 20 ft + 40 ft stackweight

in hold: 30.5 t/FEU not

exceeding max 40 ft

stack weight

all fuel oil tanks full

all ballast tanks full

T sc

100%

(sag.

or min.

hog.)

≤

100%

HSM-1

HSA-1

FSM-1

BSR-1P

BSP-1P

Damaged condition

LC7

Flooded

damage

condition(2)

on deck: max 40 ft

stack weight

in hold:

centre: flooded

adjacent: 20t/FEU

all ballast tanks full at

inclined side

T DAM

100%

(sag.

or min.

hog.)

-Static

only(3)




Container ships

DNV GL AS


Aft Mid Fore



% of

perm.

SWBM

% of

perm.

SWSF

Dynamic

load case

Notes:

1) For asymmetrical structures BSR-1S and BSP-1S shall be investigated additionally.

2) With deepest equilibrium waterline T DAM in a heeled damage condition where the considered hold is one

of the flooded compartments. Although this is a typical scenatio with two or three flooded holds. in the

FE-analysis only the center cargo hold is flooded

3) Heeled condition shall be considered at least for inner pressure in the flooded cargo hold, for outer

pressure on the shell and for container forces, based on design ZDAM and ΘDAM as defined in Pt.3 Ch.4

Sec.6 [1.2.7]

2.4 Acceptance criteria

2.4.1 Yield

Verification against the yield criteria shall be carried out according to Pt.3 Ch.7 Sec.3 [4.2].

2.4.2 Buckling

Verification against the buckling criteria shall be carried out according to Pt.3 Ch.8 Sec.4.

3 Fuel oil deep tank finite element analysis

3.1 Application

Fuel oil deep tank finite element analysis is required for ships with typical fuel oil deep tank arrangements,i.e., tanks are below the deck house in a twin-island design or tanks are below one 40 ft container bay in asingle-island design.

3.2 Scope

The fuel oil deep tank finite element analysis shall be used to assess the structural adequacy of all primarysupporting members.

Guidance note:

The evaluation of the yield and buckling criteria is of particular importance for the following structural members:

— inner bottom

— outer bottom

— double bottom girders— double bottom floors

— transverse bulkheads with attached stringers

— longitudinal bulkheads with attached stringers

— vertical girders and/or pillars.





Container ships

DNV GL AS

3.3 Modelling principles

3.3.1 The analysis model shall extend from one cargo hold aft of the aftermost fuel oil tank transversebulkhead to one cargo hold forward of the foremost fuel oil tank transverse bulkhead.

3.3.2 The FE models shall be based on gross scantlings.

3.3.3 If deck houses in a twin-island design are not included in the FE model, the static self-weight of thesestructures shall be included in the model by applying line loads.

3.4 Design load combinations

3.4.1 Design load combinations as given in [3.4.3] are based on typical fuel oil deep tank arrangements, i.e.,tanks are below the deck house in a twin-island design or tanks are below one 40 ft container bay in a single-island design. The loading patterns are illustrated in Table 1.

If fuel oil deep tank arrangements are different from the above assumption, the design load conditions shallbe agreed on by the Society.

3.4.2 In general, heeled conditions of fuel oil deep tank do not need to be considered. However, if any fuel oildeep tank is wider than 50% of ship’s breadth B, heeled seagoing conditions shall be agreed with the Societyand shall be applied in addition to load conditions as given in [3.4.3].

3.4.3 The design load combinations as given in Table 2 are required for fuel oil deep tank finite elementanalysis.




Container ships

DNV GL AS

Table 2 Standard design load combinations for fuel oil deep tank finite element analysis


Aft Mid Fore

Tank content and

container weightsDraught

% of

perm.

SWBM

% of

perm.

SWSF

Dynamic

load case

DT1-a

Ballast

Departure

all fuel oil deep tanks full

all ballast tanks full

all container bays empty

T BAL

SWBM in

Ballast

condition(1)

≤ 100%

HSM-1

HSA-1

FSM-1

DT1-b,

Ballast

Departure

relevant fuel oil deep

tanks are full and empty

so that each longitudinal

bulkhead separating fuel

oil deep tanks has lateral

pressures from first side

all ballast tanks full all

container bays empty

T BAL

SWBM in

Ballast

condition(1)

≤ 100%

HSM-1

HSA-1

FSM-1

DT1

DT1-c

BallastDeparture






pressures from second

side

all ballast tanks full all

container bays empty

T BAL

SWBM in

Ballast

condition(1)

≤ 100%

HSM-1

HSA-1

FSM-1




Container ships

DNV GL AS


Aft Mid Fore

Tank content and


% of

perm.

SWBM

% of

perm.

SWSF

Dynamic

load case

DT2-a

Tank Test

Fuel oil deep tank filling is

for tank test according to

Pt.3 Ch.4 Sec.6 [4.1]

all fuel oil deep tanks full

all ballast tanks empty


T BAL

SWBM in

Ballast

condition(1)

≤ 100%Static

only

DT2-bTank Test

Fuel oil deep tank filling

according to Pt.3 Ch.4

Sec.6 [4.1]



so that each longitudinalbulkhead separating fuel


pressures from first side



T BAL

SWBM in

Ballastcondition

(1)

≤ 100% Staticonly

DT2

DT2-c

Tank Test

Fuel oil deep tank filling

according to Pt.3 Ch.4

Sec.6 [4.1]





oil deep tanks has lateralpressures from second

side



T BAL

SWBM in

Ballast

condition(1)

≤ 100%Static

only




Container ships

DNV GL AS


Aft Mid Fore

Tank content and


% of

perm.

SWBM

% of

perm.

SWSF

Dynamic

load case

DT320 ft

Heavy

all tanks emptyon deck: max 20 ft stack

weight, if mixed stowage

is applicable, max 20 ft +

40 ft stack weight

in hold:

max 20 ft stack weight, if

unavailable 24t/TEU

0.90T SC

100%

(sag.or

min.

hog.)

≤ 100%

HSM-1

HSA-1

FSM-1

DT4 40 ft Light

all tanks empty

on deck: 90% of max 40

ft stack

weight not exceeding 17

t/FEU

in hold: 16 t/FEU

T sc 100%

(hog.)≤ 100%

HSM-2

HSA-2

FSM-2

Notes:

1) Still water bending moment corresponding to the ballast departure loading condition from loading manual.

3.5 Acceptance criteria

Yield and buckling criteria is given in [2.4].




Container ships

DNV GL AS

SECTION 7 FATIGUE

1 General

General assumptions, requirements as well as loading conditions for prescriptive fatigue strength assessmentare given by Pt.3 Ch.9. Methods and procedures for the fatigue strength assessment of the hull structuresare described in the Society's document DNVGL-CG-0129, Fatigue assessment of ship structures.

1.1 Scope

1.1.1 General

This section is applicable for container ships having a rule length, L, of 90 m or greater. Prescriptive fatiguestrength assessment shall be performed for structure details which are predominantly subjected to cyclicloads. The prescriptive fatigue strength assessment is applicable to structures that are mainly loaded bylongitudinal hull girder stresses and local pressures.

1.1.2 Details to be assessed by prescriptive fatigue assessment

In particular, the following details shall be considered for container ships:

— end connections of longitudinal stiffeners to transverse web frames and transverse bulkheads

— welded details in the upper part of the hull girder, e.g., transverse butt welds, hatch cover resting pads,equipment holders etc.

— knuckles and discontinuities of longitudinal structural members, e.g. hatch coamings, in the upper part of the hull girder.

1.1.3 Longitudinal extent for prescriptive fatigue assessment

Structural details subject to significant dynamic stresses between the fore and the aft end of the cargo holdarea shall be assessed.

2 Prescriptive fatigue strength calculations

2.1 Longitudinal stiffener end connections

2.1.1 For side structures comprising relatively low lateral bending stiffness, e.g. due to omission of stringersor reduced number of transverse web frames, additional stresses due to relative deflections of supportingtransverses shall be considered.

2.1.2 The additional stresses due to relative displacement shall be calculated as described in DNVGL-CG-0129 [4.7], based on relative displacements taken from, e.g., global or cargo hold finite element analysis.If no results are available from finite element analysis for the specific ship, relative displacements may beassumed as for a similar ship. The Society decides whether a certain ship can be considered as similar to thespecific ship.

2.2 Welded details in the upper part of the hull girder

For welded details in the upper part of the hull girder, e.g. transverse butt welds, hatch cover resting pads,equipment holders etc., the evaluation of permissible stress concentration factors or required FAT classesaccording to DNVGL-CG-0129 [3.5] are applicable.




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SECTION 8 CONTAINER SECURING ARRANGEMENTSymbols

For symbols not defined in this section, refer to Pt.3 Ch.1 Sec.4 [2].

G = container’s gross mass, in ton, as given in [4.1.2]

ReH = specified minimum yield stress, in N/mm².

1 General

1.1 Container securing arrangements

1.1.1 Container securing arrangement plan

A container securing arrangement plan shall be submitted according to Sec.1 [2.1], complying with thefollowing:

— Stowage of containers on deck, see [2]

— Stowage of containers below deck, see [3]— Strength evaluation of container securing arrangements, see [8.1].

The container securing and arrangement plan shall include minimum one metacentric height, GM. The GMvalue shall not be less than the minimum GM value included in the approved trim and stability booklet for therespective draught.

The approved container securing arrangement plan shall be kept on board.

Guidance note:

It is strongly recommended for ships designed for carrying containers on deck to ensure the compliance with Code of Safe Practice

for Cargo Stowage and Securing (CSS Code) Annex 14 adopted by MSC.1/Circ. 1352 and related IACS UI SC265, considering design

aspects to be implemented at the newbuilding stage.

The application of the class notation SAFELASH visualizes compliance with CSS Code Annex 14 to all relevant parties including flag

administrations and port state authorities.


1.1.2 Stowage of containers

Containers shall be stowed and secured in accordance with the approved container securing arrangementplan or checked for compliance with the requirements given in [8.1] by the lashing computer certified inaccordance with [9].

All container securing devices shall be delivered with product certificates in accordance with Sec.1 [2.2].Container securing equipment need only to be carried on board to the extent the ship is carrying containers.

1.2 Container securing structures

1.2.1 Lashing bridge

If the ship is equipped with lashing bridges, a structural drawing shall be submitted according to Sec.1 [2.1]

and comply with the requirements given in [8.2].

1.2.2 Cell guides

A structural drawing shall be submitted according to Sec.1 [2.1] and comply with the requirements given in[8.2].




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1.2.3 Container stanchions

If the ship is equipped with container stanchions, a structural drawing shall be submitted according to Sec.1[2.1] and comply with the requirements given in [8.2].

1.2.4 Other container securing structures

If the ship is equipped with other container securing structures, a structural drawing shall be submitted forapproval and comply with the requirement given in [8.2].

2 Stowage of containers on deck

2.1 General

2.1.1 Relative movement of container support fittings

For containers resting on container support fittings which may move relative to each other, e.g. containersthat are partly resting on hatch covers and partly resting on container stanchions, the container supportfittings shall be arranged so that the relative movement does not lead to permanent deformation of thecontainers.

Guidance note:To prevent damages to the container itself caused by relative movement of supporting fittings, sliding plates or foundations with

elongated apertures may be provided.


2.2 Stowage on deck with neither lashing nor lateral rigid support

2.2.1 Containers in one layer

Containers carried in one layer shall be secured against tilting and shifting by locking devices arranged attheir lower corner castings.

2.2.2 Containers in several layers

If containers are stowed in several layers, locking devices shall be arranged between the container layers.

Containers located in the lowermost layer shall be locked as well at their lower corner castings.




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2.3 Stowage on deck with lashing but without lateral rigid support

2.3.1 Lashing arrangement

A typical lashing arrangement is shown in Figure 1 for illustration.

Figure 1 Typical arrangement of lashings

2.3.2 Locking devices

Locking devices shall be arranged between container layers and below lowest container layer betweencontainer corner castings/container support fittings.

2.3.3 Direction of containers

All wall ends and all door ends of containers shall be stowed in the same direction. If this requirement is notmet, the stack in question shall be examined separately according to [8.1].

2.3.4 Lashing

In case single lashings are used, lashing elements such as lashing rods shall be fitted to the containers' lowercorner castings. If upper corner castings are utilized instead, the allowable lashing loads shall be decreasedaccording to DNVGL-CG-0060Container securing, [3.2].

Guidance note:

When lashings of containers are used, pretension of lashings should be kept as small as possible.


2.3.5 Vertical lashings

For vertical lashings, lashing shall be "loose" to equalize the clearance between the twistlock and cornercasting/container support fittings.

Guidance note:

This equalization may be achieved by spring elements.





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2.3.6 Cross lashings

If external cross lashing systems are used, see Figure 2, the calculation of lashing forces in accordance with[8.1] shall consider the vertical clearance between the twistlook and corner casting/container support fitting.

For vertical clearance, the following values shall be applied:

— conventional and semi-automatic twistlooks: 12 mm

— Fully Automatic Locks (latch lock): 20 mm

Guidance note:

In case lashing rods with spring elements or similar are fitted, 0 mm may be applied for vertical clearance.


Figure 2 Internal and external lashings

2.4 Stowage on deck with lateral rigid support

2.4.1 Cell guides on deckFor containers stowed with both ends supported by cell guides, they may be treated as containers stowedwith cell guided below the deck, and shall comply with [3.1].

The 20 ft containers may be stowed in 40 ft cell guides according to [3.1.8] provided that outermost stacksare additionally secured against green sea loads in accordance with [2.4.3].

2.4.2 Over stow of containers above cell guide

Containers, with any part of them, stowed exceeding the upper end of cell guides shall be secured accordingto [2.3]. The additional compression/tension forces on container post due to tilting moment shall be includedin the calculations.

2.4.3 Containers subject to green sea loads

Containers stowed in positions subject to green sea loads shall be additionally secured by locking devices, bycontainer support fittings of increased height and/or by reinforced lashings.

Guidance note:

For ships with low freeboard and when it is possible that part of container stacks may submerge into the sea, buoyancy loads may

have to be considered in the design of the lashing system.





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3 Stowage of containers below deck

3.1 Stowage below deck in cell guides

3.1.1 General

Cell guides for containers may be welded to the ship's hull or be arranged in a detachable manner (screwedconnections, suspended structures).

3.1.2 Lateral support of cell guides

Cell guides at transverse or longitudinal bulkheads shall be laterally supported by the bulkhead withhorizontal web plates or other suitable elements.

3.1.3 Vertical guide rails of cell guides

Vertical guide rails consist typically of equal sided steel angle bars. On account of abrasion and local forces,e.g., due to jamming occurring when hoisting and lowering of containers, the thickness of angle bars shall beat least 12 mm.

Where vertical guide rails consist of several steel angle bars, these bars shall be connected to each other

by horizontal web plates arranged at least at the level of lateral supports and additionally between lateralsupports depending on bending moments induced by containers due to random stowage of 8’6” and 9’6” highcontainers.

3.1.4 Guide heads

Top ends of guide rails shall be fitted with sufficiently strong guide heads, according to operating conditions.

To minimise the impact on fatigue strength of longitudinal hull structures, horizontal supports for guide headsin the area close to hatch corners shall be arranged on transverse bulkheads only.

Guidance note:

To transfer shear forces caused by loading and offloading, vertical supports for guide heads should be arranged on transverse

bulkheads. Vertical supports for guide heads may be fitted to the longitudinal bulkhead.


3.1.5 Self-supporting cell guidesThe self-supporting cell guides shall consist of transverse ties and longitudinal ties to which steel guide railsare attached. The self-supporting cell guides shall be sufficiently secured to the inner hull structure.

Guidance note 1:

The transverse ties should be fitted at the level of the container corners.


Guidance note 2:

Cell guides may consist of main girders (e.g., I-beams) to which steel guide angles are attached.


3.1.6 Movable cell guides

Movable cell guides shall be provided with means to prevent lifting during discharge operation of containers.




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3.1.7 Clearances

Clearance of standard containers in guide rails shall not exceed 25 mm athwartships and 38 mm in the fore-to-aft direction. Maximum clearance in the fore-to-aft direction includes the deformation of the cell-guidesystem itself.

Guidance note:

When building tolerance of cell guides is taken into consideration, the limits above may be increased by 6 mm in transverse and

longitudinal directions.


3.1.8 20 ft containers in 40 ft cell guides

In cases where the vertical dimensionless acceleration factor as given in [4.5.3] exceeds 1, the 20 ftcontainers shall be secured against lifting.

In a mixed stowage of 20 ft and 40 ft containers, the 40 ft containers shall be stowed on top of 20 ftcontainers.

In order to prevent sliding in transverse and longitudinal direction:

— for 20 ft containers stacked on top of each other, the 20 ft containers shall be secured together by aminimum of two stacking cones with at least one stacking cone fitted in the free end.

— for the lowermost 20 ft container, the corners in the cell guide end and in the free end shall be secured bystacking cones

— for mixed stowage of 20 ft and 40 ft containers, the lowermost 40 ft container shall be secured to theuppermost 20 ft container by two stacking cones in each end.

4 Loads acting on containers

4.1 General

4.1.1 Transverse, longitudinal and vertical loads on containers given below shall be understood as forcesaligned in the ship’s coordinate. They include static gravity loads, dynamic loads caused by the ship’s surge,pitch, heave, yaw, sway and roll motions, as well as wind loads.

4.1.2 The following values for minimum and maximum gross mass of containers are assumed for subsequentcalculations (see DNVGL-CG-0060 , [B]):

20 ft minimum 2.5 tons

maximum 30.5 tons


maximum 30.5 tons


maximum 32.5 tons

4.1.3 The height of the centre of gravity of the container and its cargo is assumed at 45 % of container

height.

4.1.4 A force reduction in calculations due to friction between container layers shall not be considered.




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4.2 Wind loads

4.2.1 Lateral wind loads in ship’s transverse direction, F w , in kN, shall be considered on exposed side walls of containers according to Table 1.

Table 1 Wind load Fw per container2)

container type

20 ft 40 ft

1st tier1)

30 60

2nd tier and higher 15 30

Notes:

1) The load Fw for the first tier accounts additionally for green sea loads on outermost stacks. The green sea loads may

be neglected in case of open holds of hatchcoverless ships.

2) The stated values are valid for 8' 6" high containers. For other container heights and lengths, the wind force has to

be adjusted according their side wall area.

4.2.2 Wind loads may be neglected for uppermost containers in partly shielded stacks where the differencein height to shielding stack is less than 0.33 x 8 ft 6 inches. For partly shielded stacks where the shieldingstack does not cover the whole length of the partly shielded stack, wind loads according to Table 1 shall beapplied according to the longitudinal overhang areas exposed to wind. See Figure 3 for illustrations.

Figure 3 Example of wind application on partly shielded stacks

If inside positioned stacks form a transversal gap larger than 0.5 B for ships with B > 16 m or more thanthree rows wide for ships with B ≤ 16 m, free standing stacks shall be imposed with wind loads accordingto Table 1. And the wind loads may be reduced to 0.33 of loads given in Table 1. For smaller gaps than theabove, wind loads may be neglected.




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4.3 Transverse forces

4.3.1 Transverse forces

The transverse force in the ship’s transverse direction, F q, in kN, acting on a container shall be calculated as

following:

for container securing arrangements

for container securing structures

Where:

bq = transverse dimensionless acceleration factor, as defined in [4.3.2]

F w = wind loads, in kN, as defined in [4.2]

a y-env

= transverse envelop accelerations, as defined in Pt.3 Ch.4 Sec.3 [3.3].

Where containers or container stacks placed side by side are coupled to form container blocks, transverseloads acting on containers, such as wind loads on outermost container stacks, may be equally distributedover a maximum of three stacks.

4.3.2 Transverse dimensionless acceleration factor

The transverse dimensionless acceleration factor for unrestricted service, bq, including combined effects of the ship’s motions, shall be calculated as following:

Where:

bv = dimensionless acceleration in the global vertical direction due to pitch and heave

bh = dimensionless acceleration in the global horizontal direction due to yaw and sway

θ, T θ = rolling angle and rolling period

R = as defined in Pt.3 Ch.4 Sec.3

z cont = height of container’s centre of gravity above base line, in m.

In the formula above, values of bv , bh and θ represent simultaneously acting accelerations and roll angle of the ship. They are determined from the respective design values bv,D, bh,D and θD, i.e., the extreme valuesoccurring once in operation of the ship, such that bq attains its maximum value and

The transverse acceleration factor, bq, shall be determined based on a semi-empirical tool.Guidance note:

bq may be determined applying the Society's calculation tool for strength evaluation of container securing arrangements, StowLash.

In order to obtain bq values for application in other tools, e.g. loading computer systems, the Society will provide a separate software

development kit upon request.





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For ships with unusual form and design regarding, e.g. stern and bow shape, the Society may requiredetermination of the transverse acceleration factor, bq, by an alternative calculation method.




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4.4 Longitudinal forces

4.4.1 Longitudinal forces

The longitudinal force in ship’s longitudinal direction, F , in kN, acting on a container shall be calculated as

following:



where:

bl = longitudinal dimensionless acceleration factor, as defined in [4.4.2].

a x-env = longitudinal envelop accelerations, as defined in Pt.3 Ch.4 Sec.3 [3.3].

4.4.2 Longitudinal dimensionless acceleration factor

The longitudinal dimensionless acceleration factor, bl , including combined effects of the ship’s motions, shallbe calculated according to Table 2.

Table 2 Longitudinal dimensionless acceleration factor bℓ

for lowest tier in cargo hold for lowest tier on deck

For any length of the ship:

min bℓ

Note: The bℓ values for containers located between the lowest tier in the cargo hold and the lowest tier on deck shall be

determined by linear interpolation and for containers above the lowest tier on deck by linear extrapolation.

4.5 Vertical forces

4.5.1 Vertical forces in combination with transverse forces

The vertical force in ship’s vertical direction acting downwards in combination with transverse forces, F v1, inkN, acting on a container shall be calculated as following:

where:

θ = as defined in [4.3.2] for container securing arrangements

as defined in Pt.3 Ch.4 Sec.3 for container securing structures.




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4.5.2 Vertical forces in combination with longitudinal forces

The vertical force in ship’s vertical direction acting downwards in combination with longitudinal forces, F v2, inkN, acting on a container shall be calculated as following:



where:

bv = vertical dimensionless acceleration factor, as defined in [4.5.3].

a z-env = vertical envelop accelerations, as defined in Pt.3 Ch.4 Sec.3 [3.3].

4.5.3 Vertical dimensionless acceleration factor

The vertical dimensionless acceleration factor, bv , including combined effects of the ship’s motions, shall becalculated as following:

bv = F ∙ m

where:

F = coefficient, to be taken as:

with

m = coefficient, to be taken as:

for

for

for

m0 = coefficient, to be taken as:




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5 Design load combinations for container securing arrangements

5.1 Design load combinations

5.1.1 Applicable load combinations for container securing arrangements are listed in Table 3.

Table 3 Load combinations for container securing arrangements

LC Description Vertical loads Horizontal loads Wind loads

1 Transverse loading Fv1 Fq Yes

2 Longitudinal/vertical loading Fv2 Fl No

5.1.2 Transverse loading (LC1)

Forces in the lashing system shall be calculated by applying the transverse force F q according to [4.3.1],combined with the vertical force F v1 according to [4.5.1].

Wind loads shall be added to wind exposed containers according to [4.2].

5.1.3 Longitudinal/vertical loading (LC2)

Forces in the lashing system shall be calculated by applying the longitudinal force F l according to [4.4.1],combined with vertical force F v2 according to [4.5.2].

6 Design load combinations for container securing structures

6.1 General

6.1.1 Loads

Design load combinations for container securing structures shall be calculated according to Pt.3 Ch.4 basedon [6.1.2] and [6.1.3].

6.1.2 GM

Metacentric height, GM , in m, shall be calculated as following:

GM = 0.04 · B2 /Z for B ≤ 32.2 m

GM = (B-25.96)/156 · B2 /Z for 32.2 m < B ≤ 40 m

GM = 0.09 · B2 /Z for B > 40 m

where:

Z = vertical distance, in m, to be taken as:

Z = 1.05 ntier + H st ntier = number of container tiers for the highest stack on the weather deck, as specified in the container

stowage arrangement planH st = vertical distance between T SC and bottom of container stack on the weather deck, in m.

6.1.3 Height and weight distribution of container stacks

Maximum stack weight and maximum stack height according to the container stowage plan in combinationwith a homogeneous weight distribution shall be used as basis in the design load combinations given in [6.2]to [6.4].




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If strength evaluation in accordance with [8.1] of such a container stowage result in container and/orcontainer securing device exceeding any of the acceptance criteria given in [7.1], the vertical centre of gravity of the stack shall be adjusted vertically downwards until the limit on which none of the acceptancecriteria given in [7.1] is exceeded.

6.1.4 Lashing arrangementLoad combinations of the container securing structures shall be based on lashing/securing patterns as shownin the container stowage plan.

6.2 Design load combinations for lashing bridge

6.2.1 Applicable load combinations are listed in Table 4.

Table 4 Load combinations for lashing bridge


1Symmetrical lashing loads from lashing bridge

forward and aft sideFv1 Fq Yes

2Asymmetrical lashing loads from lashing bridge

forward and aft side separatelyFv1 Fq Yes

6.3 Design load combinations for cell guide

6.3.1 Applicable load combinations are listed in Table 5.

Table 5 Load combinations for cell guide


1 Transverse loading Not Applicable Fq Yes

2 Longitudinal/vertical loading Not Applicable Fl No

6.3.2 Transverse loads on cell guides shall be considered for stowage of both 40 ft containers and 20 ftcontainers as follows:

— for stowage of 40 ft containers in cell guides, it is assumed that one-quarter of F q is transmitted to the cellguide structure at each of the four corner fittings of one longitudinal side wall of the container.

— for stowage of 20 ft containers in 40 ft cell guides, it is assumed that 1/3 of F q is transmitted to the cellguide structure at each of the two corner castings of one longitudinal side wall at the container end placedin the cell guide.

6.3.3 Longitudinal loads on cell guides shall be considered for stowage of both 40 ft containers and 20 ftcontainers as follows:

— it is assumed that one-quarter of F ℓ is transmitted to the cell guide structure at each of the four cornerfittings of the container’s front end or door end.

6.3.4 Cell guide structures shall be dimensioned for the maximum number of container layers and for themaximum permitted container gross weight in each layer. Combinations of different container heights in astack, yielding the most severe stresses in cell guide structures, shall be considered.




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6.4 Design load combinations for container stanchions

6.4.1 Applicable load combinations are listed in [5.1].

6.4.2 For container stowage without lateral support, container stanchions and support structures shall be

dimensioned based on the most severe simultaneously acting transverse force F T,found , and vertical forces,CPLfound and LF found , acting on container support fittings calculated according to DNVGL-CG-0060, Container Securing.

If the bending strength of container stanchions is smaller in the longitudinal than in the transversedirection, the vertical forces on the container support fittings at the stanchion shall be considered as actingsimultaneously with the longitudinal force, F L,found , according to DNVGL-CG-0060, Container Securing,instead of the transverse forces, F T,found .

6.4.3 Where lashings are arranged at the stanchions, the stanchions shall be dimensioned also consideringthe most severe vertical and horizontal loads resulting from lashing forces calculated according to DNVGL-CG-0060, Container Securing, [4.3].

6.4.4 For to dimension container stanchions, the most unfavourable eccentricity of the vertical compressiveforce CPLfound acting on container support fittings points shall be applied.

6.4.5 The horizontal design load for container stanchions bending transversely need not to be taken greaterthan the one producing a deflection considering 10 mm clearance between the container’s locking device andthe container support fittings on the hatch covers.

7 Acceptance criteria

7.1 Acceptance criteria for container securing arrangements

7.1.1 Container securing devices

Permissible forces for container securing devices shall be taken as the provided Safe Working Load (SWL)

Guidance note:

Typical values of SWL for container securing devices are given in DNVGL-CG-0060, Container Securing, [3.3].


7.1.2 Containers

Permissible container forces shall be taken as the container strength ratings given in recognized standards.

Guidance note:

Strength ratings of ISO 20 ft and 40 ft containers are DNVGL-CG-0060, Container Securing, [3.2].


7.2 Permissible forces for container securing structures

7.2.1 Yielding

The permissible stresses for container securing structures, in N/mm2, shall be taken as following:




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where:

σN = normal stress, in N/mm².

τ = shear stress, in N/mm².

σv = equivalent stress, in N/mm².

7.2.2 Buckling

Buckling capacity for container securing structures shall be according to Pt.3 Ch.8 with allowable bucklingutilization factor based on AC-II.

8 Strength evaluation

8.1 Strength evaluation of container securing arrangements

8.1.1 Strength evaluation of container securing arrangements shall be based on load combinations accordingto [5] and acceptance criteria according to [7.1].

Guidance note:

Strength evaluation methods acceptable to the Society are given in DNVGL-CG-0060, Container Securing.


8.1.2 Lashing bridge deformation

For container securing arrangements supported by lashing bridges, the deformation limits given in [8.2.2]

shall be included in the strength evaluation.If strength evaluation of lashing bridges in accordance with [8.2] result in greater deformations than givenin [8.2.2], such values will be accepted on a case by case basis provided that these deformations values areapplied in the strength evaluation of the container securing arrangements.

8.2 Strength evaluation of container securing structures

8.2.1 General

Strength evaluation of container securing structures shall be based on load combinations according to [6]and acceptance criteria according to [7.2].

8.2.2 Lashing bridge

Effective structures to transfer lashing forces into coaming or deck structure shall be provided, e.g. shear

plates or diagonal bracings.

Deformations of the lashing bridges in ship’s transverse direction shall not exceed:

— 1-tier high lashing bridge: 10 mm

— 2-tier high lashing bridge: 25 mm

— 3-tier and higher lashing bridges: 35 mm

Deformations of the lashing bridges in ship’s longitudinal direction shall be limited in particular with regard toasymmetrical load combination to ensure sufficient effectiveness of the lashings.




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8.2.3 Cell guide

Parts of the cell guide structures considered as components of the ship's hull structure, shall be included inthe hull scope.

8.2.4 Container stanchions

Detached stanchions shall be designed to safely absorb shocks occurring during normal loading operations.Hatch deformations shall be taken into consideration so that containers situated on stanchions and hatchcovers shall not transmit shifting forces (see [2.1.1]).

To dimension container support fittings welded into the ship's longitudinal main structures (strength deck,inner bottom, etc.), stresses resulting from the ship’s global loads shall be considered.

9 Lashing computer system

9.1 Application

9.1.1 The lashing computer system shall be certified by the Society. See Sec.1 [2].

9.1.2 The approved test conditions together with the user manual and the lashing computer certificate shallbe kept on board and shall be available to the Society upon request.

9.2 Definition

9.2.1 Lashing computer system

A lashing computer system is a computer-based system for calculation and control of container securingarrangements in compliance with the applicable strength requirements as given in this section. The lashingcomputer system consists of software (calculation program) and hardware (the computer on which it runs).

9.2.2 Approval of software

Approval of software means that the Society approves the software for a specific installation on board of aspecific ship.

9.2.3 Certification of lashing computer system

Certification (installation testing) means that the Society has certified that the lashing computer systemworks properly on board a specific ship, and that the correct approved version of the software has beeninstalled.

9.3 Approval and certification process

The approval and certification process includes the following procedures for each ship:

1) approval of software which results in approved test conditions

2) approval of computer hardware, where necessary

3) certification of the installed lashing computer system, which results in a lashing computer certificate.

9.4 Hardware approval

The approved software is either installed on type approved hardware, or installed on two nominatedcomputers.

If the software is installed on two nominated computers, type approval of the hardware may be waived, butboth nominated computers shall be equipped with separate screens and printers.




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9.5 Software approval

9.5.1 General

The approval is based on a review and acceptance of design, calculation method, verification of stored dataand test calculation for the specific ship.

Approval of the software shall be carried out for each specific ship where the software shall be installed.

9.5.2 Functional requirement

The software shall be user friendly, with a graphic presentation of the container arrangement. It shall rejectinput errors from user, e.g.:

— negative weight input

— container positioned outside the designated storage location

— lashing which are not possible on board

The software and the stored characteristic data shall be protected against any erroneous use.

9.5.3 Output data

All screen and hardcopy output data shall be presented in a clear and unambiguous manner, withidentification of the version number of the calculation program.

The software shall be capable of producing printouts of the results numerically. These numeric values shall bepresented both as absolute values and as a percentage of the allowable values.

9.5.4 Container stowage

The stowage of containers in the software shall be according to the patterns shown in the approved containersecuring arrangements plan, e.g. mixed stowage of 40 ft on top of 20 ft on deck shall only be possible in thesoftware. If the corresponding stowage is listed in the approved container securing arrangement plan.

9.5.5 Test condition, general information

The test conditions shall include the following information:

— ship’s main data (IMO-No., L pp, B, D, T design, V )

— other optional input parameters as used in approved container securing arrangements plan (such as bilgekeel area or C b)

— GM value— position of each container stack

— graphical representation of 20 ft-stowage on deck and 40 ft-stowage on deck as well as other containersizes as described in approved container securing arrangements plan, e.g. 45 ft-overstowed on 40 ft,including information as further detailed in [9.5.7].

— tabular result representation for aforementioned cases as screen and hard copy output to the user in aclear and unambiguous manner, including information as further detailed in [9.5.6].

9.5.6 Test condition, result information

In test conditions, the following details shall be given for each container arrangement in cell guides:

— container weight

— actual stack weights

— permissible stack weights

— transverse acceleration of each stack— corner post loads

— pressure loads at bottom of container

— percentage of exceeding

— a warning has to be given if any of the strength limits are exceeded.

For bays with lashings applied and for bays with deck cell guides where containers will be overstowed on top,information shall be given for the following additional test conditions:




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— typical lashing arrangement and parameters

— racking, lifting and lashing forces.

9.5.7 Test condition, load cases

Test conditions shall be selected in order to represent typical container stowage as follows:

— typical stowage in hold

— mixed stowage in hold and/or on deck, if applicable

— typical stowage on deck

— deck stowage with twistlocks only

— an example where outboard stack is missing

— other stowage as given in the approved container securing arrangements plan.

9.5.8 Test condition, acceptance criteria

Results calculated by the software and shown in test conditions will be verified by the Society. The differencebetween the software and the verified results shall not be greater than 1%, as given in the following:

[(Results from software) – (Results from independent calculations)] / (Strength limits) ≤ ±1%

9.5.9 Reference data

In reference data, the following details shall be given:

— main dimensions of the ship

— the position of each bay from the aft perpendicular

— strength limitations (for containers, lashing equipment and the ship)

— general loading limitations.

Reference data shall be included in test conditions or in a separate document.

9.6 Certification

9.6.1 General

Certification shall be carried out for each ship where a lashing computer system has been installed.

After completion of the test according to [9.6.2] the lashing computer certificate will be issued.The followings will be listed in the lashing computer certificate:

— name of ship, name of yard, yard number and year of built for the ship

— software name, software version

— software manufacturer name and address

— hardware name, serial number and manufacturer

— name and serial number of the second nominated computer or type approval certificate number

— identification of the approved test conditions used for the certification.

9.6.2 Test

The approved test conditions shall be tested on the lashing computer system on board of the ship in presenceof the Society.

During the test,

— the securing arrangements calculated on the installed lashing computer system shall be verified tobe identical to the approved test conditions. If numerical output from the lashing computer system isdifferent with the approved test conditions, a certificate cannot be issued, and

— at least one of the test conditions shall be built up from sketch, to ensure that the calculating methodsfunction properly.




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Where the hardware is not type approved, the test shall be carried out on both the first and the secondnominated computer prior to the issuance of the lashing computer certificate. Both of the nominatedcomputers shall be identified on the certificate.




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SECTION 9 HULL SUPPORT STRUCTURES FOR CONTAINER SUPPORTFITTINGS AND CONTAINER SECURING STRUCTURES

1 General

1.1 Objective

This section contains specific requirements for hull support structures of container support fittings andcontainer securing structures as given in Sec.8.

This section is applicable for ships with hull support structures of container support fittings and containersecuring structures as given in Sec.8.

2 General requirements

2.1 Strength evaluation

Hull support structures shall be provided for container support fittings and container securing structures asgiven in Sec.8. Strength evaluation of these structures shall be based on net scantlings.

2.2 Structure arrangement

2.2.1 The hatchway coamings shall be strengthened in way of the connections of transverse and longitudinalstruts of cell guides.

The cell guides shall not be welded to deck plating edges in way of the hatchways.

2.2.2 For containers stowed in cell guides in hold, doubler plates shall be arranged for the foot prints oninner bottom or stringers.

3 Design loads

3.1 General

3.1.1 Design loads of hull support structures shall be based on lashing/securing patterns as shown in thecontainer stowage plan.

3.1.2 The hull support structures for lashing eye plates shall be strengthened with respect to the lashings'certified Safe Working Loads (SWL).

3.1.3 For hull support structures subject to hull girder loads, such loads shall be included in the strengthevaluation in accordance with [4] in addition to the design loads specified in this section.

3.2 Hull support structures for container support fittings

3.2.1 Design loads shall be calculated as reaction forces of container stacks acting on container supportfittings under applicable load combinations listed in Table 1. Loads in design load combinations shall becalculated according to Sec.8 [6].




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Table 1 Load combinations for hull support structures for container support fittings


1 Transverse loading Fv1 Fq Yes

2 Longitudinal/vertical loading Fv2 Fl No

3.3 Hull support structures for container securing structures

Design loads acting on hull support structures shall be taken in accordance with Sec.8 [6].

4 Strength evaluation

4.1 General

4.1.1 Strength evaluation of hull support structures shall be based on load combinations according to [3] and

acceptance criteria according to Sec.8 [7.2].




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SECTION 10 APPLICATION OF THICK STEEL PLATES ANDADDITIONAL REQUIREMENTS FOR STEEL STRENGTH GROUP VL47

1 General

1.1 Application

1.1.1 In conjunction to IACS UR W31 and IACS UR S33 this section shall be applied to ships with the classnotation Container ship having thick steel plates with thickness exceeding 50 mm, but not greater than 100mm, of steel strength groups VL36, VL40 and VL47, for upper hull longitudinal structural members.

The application of steel plates with thickness exceeding 100 mm shall be agreed on with the Society on acase-by-case basis.

1.1.2 The requirements given in [3] shall be applied additionally in cases where VL47 material is appliedaccording to [1.1.1].

1.1.3 Upper hull longitudinal structural members include uppermost strake of longitudinal bulkhead, sheer

strake, upper deck, hatch side coaming, and all attached longitudinals. See Figure 1 for illustrations.

Figure 1 Upper hull longitudinal structural members

2 Application of thick steel plates

2.1 General

2.1.1 This sub-section gives measures for identification and prevention of brittle fractures for ships accordingto [1.1.1].

2.1.2 The application of the measures specified in [2.2] and [2.3] shall be according to [2.4] duringconstruction.




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2.1.3 Welding procedures (WPS) shall be qualified through welding procedure qualification test (WPQT)according to Pt.2 Ch.4 Sec.5.

2.1.4 The material grade selection shall be according to Pt.3 Ch.3 Sec.1 [2.3].

2.2 Brittle crack arrest design

2.2.1 Measures for prevention of brittle crack initiation and propagation, which is the same meaning asbrittle crack arrest design, shall be implemented within the cargo hold region, see Table 1.

2.2.2 The approach given in this sub-section applies to the block-to-block joints, but it should be noted thatcracks can initiate and propagate away from such joints. Therefore, appropriate measures shall be consideredaccording to [2.2.4] (b).

2.2.3 Brittle crack arrest steel (BCA grade) is defined as steel plate with measured crack arrest propertiesaccording to Pt.2 Ch.2 Sec.2 [7].

2.2.4 Functional requirements of brittle crack arrest design

The purpose of the brittle crack arrest design is to arrest the propagation of a crack at a proper position andto prevent large scale fracture of the hull girder.

The point of a brittle crack initiation shall be considered in the block butt joints both of hatch side coamingand upper deck.

Guidance note:

Butt weld joints designed to be in a straight line i.e. without a shift for the hatch coaming plate, the upper deck plate, the shear

strake and the upper most strake of the longitudinal bulkhead are considered as block butt joints independent whether they are

planned as assembly or sub assembly joints, see Figure 2.


Figure 2 Block butt joints

Both of the following cases shall be considered:

a) where the brittle crack may run straight along the butt joint, and

b) where the brittle crack may be initiated or may move away from the butt joint and run into basematerial.




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2.2.5 Concept examples of brittle crack arrest design

The following options are considered to be acceptable ways of brittle crack arrest design. The detail designarrangements shall be submitted for approval. Other concept designs may be considered and accepted by theSociety on a case by case basis.

Brittle crack arrest design for [2.2.4] b):

1) Brittle crack arrest steel in upper deck, see [2.4] Measure 4 and 5

Brittle crack arrest steel shall be used for the upper deck along the cargo hold region in a way suitableto arrest a brittle crack initiating from the coaming and propagating into the structure below.

Brittle crack arrest design for [2.2.4] a):

2) High toughness welds and enhanced NDT, see [2.4] Measure 2

Where high toughness welds are applied, as an equivalent alternative to 3), 4) and 5), enhanced NDTin accordance with [2.3], with stricter defect acceptance in lieu of standard UT technique shall becarried out.

High toughness welds are defined as multi-pass welds with extended welding procedure qualificationtests including CTOD tests. The CTOD tests shall be in accordance with Pt.2 Ch.1 Sec.3 based onmodified minimum required target values of 0.2 mm for CGHAZ and WM. The CTOD is calculated asaverage of three valid CTOD test results, each individual value may not be less than 0.18 mm. For hightoughness welds COD grade material in accordance with Pt.2 Ch.2 Sec.2 [7] shall be applied.

Guidance note:

Flux-cored arc welding (FCAW) is considered as high toughness welding for the coaming structure [2.4]Table 1, while

submerged arc welding (SAW) may be applied for upper deck butt weld joints. Electro gas welding (EGW) is not considered

as high toughness welds.

The CTOD tests required for high toughness welds can be carried out within the weldability tests (for material manufacturer

approval) presumed that the same essential parameters for the welding procedure are applied.


3) Block shift, see[2.4] Measure 3

Where the block butt welds of the hatch side coaming and those of the upper deck are shifted, this

shift shall not be less than 300 mm, see Figure 3. Brittle crack arrest steel shall be used for the hatchside coaming.

The longitudinal weld joints from hatch side coaming to upper deck and from longitudinal bulkhead toupper deck, in vicinity of block joints, are important in brittle crack arrest design.

Guidance note:

Such longitudinal weld joints may be made as partial penetration welds with a root face of 50% of the abutting plate thickness,

in vicinity of the block joints, between 300 mm aft and 300 mm forward in ship’s longitudinal direction, see Figure 3.





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Figure 3 Block shift with partial penetration weld

4) Crack arrest holes, see [2.4] Measure 3

Where crack arrest holes are provided in way of the block butt welds at the region where hatch sidecoaming welds meets the deck welds, the fatigue strength of the lower end of the butt welds shall beassessed. Additional countermeasures shall be taken against brittle crack running away from the weldline into upper deck or hatch side coaming. These counter measures shall include the application of brittle crack arrest steel in hatch side coaming.

5) Crack arrest insert plates, see [2.4] Measure 3

Where insert plates of brittle crack arrest steel or weld metal inserts with high crack arrest toughnessproperties are provided in way of the block butt welds at the region where hatch side coaming weldsmeets the deck welds, additional countermeasures shall be taken against brittle crack running awayfrom the weld line into upper deck or hatch side coaming. These countermeasures shall include theapplication of brittle crack arrest steel in hatch side coamings.

2.3 Non-destructive testing (NDT) during construction

2.3.1 Where NDT during construction is required according to [2.4], NDT shall be carried out according toPt.2 Ch.4 Sec.7 and DNVGL-CG-0051, Non-destructive testing.

In addition, where enhanced NDT as specified in [2.2.5] 2) is applied, enhanced NDT shall be carried outaccording to[4], Pt.2 Ch.4 Sec.7 and DNVGL-CG-0051, Non-destructive testing.

2.3.2 Target Joints

NDT shall be carried out on all block-to-block butt joints of all upper hull longitudinal structural members asdefined in [1.1.3].

2.4 Measures for thick steel plates

The thickness and the steel strength group shown in the Table 1 apply to the hatch coaming structure, andare the controlling parameters for the application of countermeasures. In case of a thickness step the thickerplate is to be considered as the leading plate.

If the as built thickness of the hatch coaming structure is less than the values given in Table 1,countermeasures are not required regardless of the thickness and steel strength group of the upper deckplating.




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Table 1 Measures depending on thickness and steel strength group of hatch coaming structures

Steel strength

group

Thickness

[mm] Option

Measure 1 Measure 2 Measures 3+4 Measure 5

50 < t ≤ 85 - N.A. N.A. N.A. N.A.VL36

85 < t ≤ 100 - X N.A. N.A. N.A.

VL40 50 < t ≤ 85 - X N.A. N.A. N.A.

A X N.A. X XVL40

(FCAW)85 < t ≤ 100

B X X N.A. X

VL40

(EGW)85 < t ≤ 100 - X N.A. X X

A X N.A. X XVL47

(FCAW)50 < t ≤ 100

B X X N.A. X

VL47

(EGW)50 < t ≤ 100 - X N.A. X X

Notes:

1) “X” means “To be applied”.

2) “N.A.” means “Need not to be applied”.

3) Either option “A” or “B” may be selected.

Measures:

1) NDT other than visual inspection on all target block joints, see [2.3].

2) Brittle crack arrest design against straight propagation of brittle crack along weld line by high toughness welds and

enhanced NDT, see [2.2.5] 2).

3) Brittle crack arrest design against straight propagation of brittle crack along weld line, see [2.2.5] 3), 4) or 5).

4) Brittle crack arrest design against deviation of brittle crack from weld line, see [2.2.5] 1).

5) Brittle crack arrest design against propagation of cracks from other weld areas such as fillets and attachment welds,

see, [2.2.5] 1).

3 Additional requirements for steel strength group VL47

3.1 General

3.1.1 This sub-section gives requirements for ships according to [1.1.2], in addition to requirementsspecified in [2].

3.1.2 VL47 material shall not have lower grade then E.




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3.2 Fatigue

3.2.1 Butt welded joints

The butt welds in the hatch side coaming and in the upper deck shall be kept away from hatch corners as far

as practical.

Guidance note:

The distance between such a butt weld to the termination point of the hatch corner curvature should be at least 500 mm in the ship's

longitudinal and transverse directions respectively.


Butt welded joints in the hatch side coaming top plate shall be analysed to show sufficient fatigue lifeaccording to Sec.3. The stress concentration factor shall be calculated according to DNVGL-CG-0129, Fatigueassessment of ships structures, [A], Table A-3.

3.2.2 Hatch corners

Hatch corners in the hatch side coaming top plate and in the upper deck shall be analysed to showacceptable fatigue strength according to Sec.3, based on global FEA.

3.2.3 GrindingThe free edge of hatch side coaming top plate shall not have any defects such as notches.

The upper and lower edges of the hatch side coaming top plate in way of the butt welds and the hatchcorners shall be ground smooth with a radius of 2 ~ 5 mm, see Figure 4. The grinding shall be doneminimum 100mm forward and aft of the butt welds. For hatch corners, the grinding shall be applied to thewhole hatch corner curvature and shall be extended to a point minimum 100mm away from the terminationof the hatch corner curvature.

Remaining upper and lower edges of the hatch side coaming top plate shall be ground smooth, with a radiusof 2 mm as minimum.

Butt welded joint edges at upper and lower sides of the hatch side coaming top plate shall be ground smooth.

For longitudinals on the hatch side coaming top plate, the grinding shall be carried out similarly as describedabove.

Figure 4 Grinding of hatch side coaming top plate

3.2.4 Outfitting details

To improve the fatigue life, outfitting details shall be applied as followings:

a) Welding for fixing outfitting to the hatch coaming top plate shall be avoided in the area close tohatch corner to the extent 500mm away from the termination of hatch corner curvature, in the ship’slongitudinal and transverse directions respectively. See Figure 5.




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This may be achieved by applying flexible hatch cover pads without attachments to the hatch coamingtop plate.

Such a welding may be accepted, provided that the calculations based on global FE analysis according toSec.3 show sufficient fatigue life at the weld toe on hatch coaming top plate. In such a case, weld profileshall be ground smooth with weld toe burr grinding according to DNVGL-CG-0129, Fatigue assessment of

ships structures, or treated in alternative equivalent means accepted by the Society.b) For hatch cover pads welded to hatch coaming top plate, when the thickness of pads exceeds 25 mm,

a chamfering of pads not exceeding 1:3 shall be applied in order to reduce the stress concentration onhatch coaming top plate.

c) For weld connections of smaller outfitting such as holders to hatch side coaming, if the welding is in arectangular or polygonal or similar shape where good workmanship is difficult to achieve in the corners,circular doubling plates shall be applied in order to achieve good workmanship. See Figure 6. Thedoubling plates shall be designed with a diameter, d , and a thickness, t , as small as practical, e.g., t ≤ 10mm and d ≤ 150 mm. The minimum required material grade for these doubling plates is AH32.

This material requirement may be waived, for round outfitting when d ≤ 50 mm and with welding ina circular shape on hatch side coaming, e.g., hand grip or hand rail stanchions, and for flat bar typeattachments oriented in ship’s transverse or vertical direction.

Figure 5 Top plate of hatch coaming

Figure 6 Doubling plate for holders




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3.3 NDT

3.3.1 During construction stage, extent of NDT on welds of steel strength group VL47 shall be at least asspecified in Table 2.

Table 2 Extent of NDT during construction stage

Testing Procedure Weld Type Scope

Visual Inspection (VT) — all weld joints 100%

Magnetic Particle Testing (MT)

— transversely or vertically orientated weld joints including

butt, T-joint and fillet welds

— longitudinally orientated weld joints

100%

25%

Ultrasonic Testing (UT) — full penetration weld joints including butt and T-joint. 100%

4 Enhanced non destructive testing of welds

4.1 Application

4.1.1

These rules shall be applied for welded joints for structural members in accordance with 2), see [2.2.5]

4.1.2

Prescribed reference level according to [4.3.5][4.4.5] shall be also valid for high strength hull structuralsteels with plate thicknesses exceeding 50 mm.

4.2 Magnetic particle testing procedure

4.2.1 Application

This procedure describes the method for magnetic particle testing (MT) of fusion welded joints in materialgrade VL E47 and shall provide the minimum requirements, which should be carried out in order to maintainand control the weld quality.

4.2.2 Performance

Magnetic particle testing of welded seams shall be performed according to DNVGL-CG-0051, Non-destructivetesting.

The acceptance criteria EN 1291 ISO 23278 level 1 shall be fulfilled. Therefore the detection of surface crackswith a linear length of 1.5 mm and a non-linear length of 2 mm has to be ensured.

4.2.3 Evaluation

Every accumulation of magnetic particles not due to a false indication indicates a discontinuity or crack in

the material which shall be registered in the inspection report and repaired. In the case of small cracks withlength ≤ 3 mm this may be done by grinding. Larger cracks shall be machined out and repair welded.

4.2.4 Documentation

The extend of the magnetic particle tested area and the test results shall be properly documented accordingto DNVGL-CG-0051, Non-destructive testing and in such a way that the performed testing can be retraced ata later stage.




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4.3 Ultrasonic testing procedure

4.3.1 Application

This procedure describes the method for manual ultrasonic testing (UT) of fusion welded joints in theupper hull with material grade VL E47 and thicknesses exceeding 50 mm and shall provide the minimum

requirements, in order to maintain and control the weld quality in new building stage.

4.3.2 Objects to be tested

100% of the full penetrated butt welds in strength plates with thicknesses exceeding 50 mm.

4.3.3 Method

Ultrasonic testing shall be performed with the impulse - echo technique by means of distance gain size –method (DGS).

Phase array (PAUT) or time of flight diffraction (TOFD) testing methods may be applied instead of or incombination with DGS ultrasonic testing method. The related test and acceptance procedures have to besubmitted to the Society for approval.

4.3.4 Requirement to the test equipment

Ultrasonic gauge

The used UT equipment has to fulfil the technical requirements as given in EN 12668-1, EN 12668-2 and EN12668-3.

The UT gauge has to be equipped with digital DGS- display presentation.

The adjustment range for the display range shall enable the range from 1 mm up to 100 mm in even stepsfor longitudinal and transverse waves in steel.

The amplification shall be adjustable for a range up to at least 80 dB with switching stages of 2 dB.

Ultrasonic probes

Probes to be used for ultrasonic testing shall be selected under consideration of nominal frequency,transducer size, size of disc- shape reflector to be tested, bevel preparation and sound attenuation of thematerial to be tested.

For oblique scanning of the welded seams shear- wave probes with an angle of incidence of 45°, 60° or 70°,working with a nominal frequency of 2 MHz, shall be used.

4.3.5 Test class, requirements

Test class B: Acceptance ISO 11666 level 2

Reference flat bottom hole DDSR = 3 mm

Test method: DGS- Method

Table 3 Test classes

Nominal probe frequency

angle of incidence

Parent material thickness t [mm] Reference flat bottom hole

2 MHz,

70° and 45° or 60°50 ≤ t ≤ 100 DDSR = 3 mm

4.3.6 Performance of ultrasonic testing

Sensitivity calibration

The basic gain has to be increased by a certain number of “dB”, in respect to the sound path, taken out of a DGS-diagram for DDSR = 3 mm, belonging to the used brand of 70°-, 45°- respectively 60°-angle probe.The correction value ΔV k for oblique scanning into the 100 mm radius of the calibration block has to beconsidered for each angle probe and can be seen in Figure 7.

Surface preparation




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Surface preparation shall be performed on both sides of the welded seam according to DNVGL-CG-0051,Non-destructive testing.

Firmly adhering paint need not be removed provided that it does not interfere with the inspection andquantitative allowance. The loss of sensitivity has to be compensated by performing of transfer correction.

Use of angle probes for the detection of longitudinal defects

Testing for longitudinal defects has to be performed according to DNVGL-CG-0051, Non-destructive testingfrom both surfaces and both sides of the welded seam with two probes 70° and 45° or 70° and 60°depending on the bevel preparation.

Use of angle probes for the detection of transverse defects

Testing for transverse defects has to be performed according to DNVGL-CG-0051, Non-destructive testingfrom both surfaces and both sides of the welded seam with two probes 70° and 45° or 70° and 60°depending on the bevel preparation.

Evaluation of defects

a) One characteristic which shall be stated for the classification of echo indications is by how many “dB” themaximum echo height of the reflections found differs from the registration level defined in Table 4 andmentioned “X” in Figure 8. In reference to the DGS- method, the size of the disc- shaped reflector mayalso be stated. Further characteristics to be stated are the depth of the defect as well as the registration

length to be determined as given DNVGL-CG-0051, Non-destructive testing. The location of defects shallbe defined by coordinates indicating the “longitudinal and transverse distances from a reference point” and the “depth position” too, see Figure 9.

b) Echo indication produced by longitudinal defects which exceed the repair limit values shown in Table 4(excess of registration length and/or echo heights above the registration level) shall be regarded as welddefects which have to be repaired.

c) Indications which increase the evaluation level shall be observed as allowed and shall be calendared anddocumented in the test report. If the indication increase the reference level too, by maximum of 6 dB(max. permissible excess echo height) they are also treated as allowable and shall be documented too.Therefore the indication length has to be determined by the use of the 6dB- drop technique.

d) Is the distance of two aligned indication less than the double length of the longer one, both indicationscan be treated as one indication. L1 < L2, Δ X 1 < 2L2, L3 < L4, Δ X 2 < 2L4, see Figure 9, but total lengthshall not exceed the maximum registration length shown in Table 4. However the minimum intermediatedistance to the next indication has to be 40 mm.

Table 4 Repair limit values

Longitudinal defects Transversal defects

Plate

thicknessNumber

of defects

[Nos./m]

Registration

length

Max.

permissible

excess

echo height

Number

of defects

[Nos./m]

Registration

length

Max.

permissible

excess

echo height

Test class

[mm] [m] [mm] [dB] [m] [mm] [dB]

B > 40

10 and

3 and

1

10

20

10

6

6

12

3 10 6

Documentation of the test results

Ultrasonic test results shall be properly documented in such a way that the performed testing can beretraced at a later stage. All indications detected shall be reported in this context, regardless whetherthese indications are exceeding the repair level or not. Repaired areas shall be re-tested and documentedaccordingly. The UT-report shall include a reference to the applicable standard and acceptance criteria too. Inaddition to the items listed under DNVGL-CG-0051, Non-destructive testing, the following shall be included inthe ultrasonic testing report:




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a) Clear identification of:

— the component

— the material

— the welded joint inspected together with its dimensions and location (sketch to be provided forcomplex weld shapes and testing arrangements).

Figure 7 Correction value for oblique scanning (ΔVK)

Figure 8 DGS- Reference curve for DDSR = 3 mm




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Figure 9 Geometrical configuration of multiple indications



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