loc guidelines for marine operations - lifting

DOCUMENT CONTROL SHEET

GUIDELINES FOR MARINE OPERATIONS

Marine Lifting

0 May 2003 Reformatted version of original document VK DB

Rev. Date Reason For Issue Author Check Client

LOC Doc. Title Marine Lifting

LOC Ref No. LOCH/GUIDELINES/R003

Client Doc Title

Client Ref No.

LOC Field Marine Operations Guidelines

London Offshore Consultants, Inc. LOCH/GUIDELINES/R003 Rev. 0 Marine Lifting

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TABLE OF CONTENTS PAGE

1. INTRODUCTION 1

1.1. Scope of Guidelines 1

1.2. Definitions 2

1.3. Reference Documents 2

1.4. Certificates of Approval 2

2. PLANNING OF MARINE LIFTS 3

2.1. General 3

2.2. Site Survey 3

2.3. Lifting Manual 3

2.4. Documentation 4

2.5. Design Calculations 5

2.6. Operational Aspects 5

3. LOADS AND ANALYSIS 6

3.1. General 6

3.2. Module Design Weight 6

3.3. Rigging Weight 7

3.4. Centre of Gravity and Tilt of Module - Single Crane 7

3.5. Static Hook Load Single Crane Lift 8

3.6. Static Hook Load - Dual Crane Lift 9

3.7. Dynamic Hook Load 9

3.8. Derivation of Lifting Point Loads - Single Crane Lifts 11

3.9. Derivation of Lifting Point Loads - Dual Crane Lifts 12

3.10. Lifting Through Water 12


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4. STRUCTURES 14

4.1. General 14

4.2. LRFD and Consequence Factors 14

4.3. Method of Analysis of Module 14

4.4. Strength of Module 15

4.5. Padeye Design 15

4.6. Padears and Trunnions 16

4.7. Cast Lifting Points 17

4.8. Fabrication and Installation of Lifting Points 17

4.9. Seafastening 17

4.10. Bumpers and Guides 17

5. REQUIREMENTS FOR LIFTING EQUIPMENT 19

5.1. General 19

5.2. Sling Force Distribution 19

5.3. Shackles 20

5.4. Spreader Beams 21

5.5. Hydraulic Lifting Devices 21

6. CRANE AND CRANE VESSELS 22

6.1. General 22

6.2. Allowable Load 22

6.3. Crane Radius Curve 22

6.4. Minimum Clearances 22

6.5. Crane Vessel Stability 23


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1. INTRODUCTION

1.1. Scope of Guidelines

1.1.1 These guidelines are a basis for the planning, design and operational aspects of marine

lifting.

1.1.2 The purpose of these guidelines is to specify appropriate standards, based on sound

engineering and good marine practice in order to ensure that lifting operations maintain

an acceptable level of safety at all times.

1.1.3 These guidelines are intended to cover any lifting operation that is subject to approval by

the Marine Warranty Surveyor. For example:

Topsides Module Lifting

Subsea Structure Lifting

Jacket Lifting

1.1.4 Other considerations may apply for other categories of lift.

1.1.5 These guidelines are based on experience over a large number of lifting operations.

However, as knowledge advances in specific areas, Marine Warranty Surveyors should

recognize that lifting operations may use alternative or new methods. The fundamental

principle to be followed by the introduction of novel or alternative methods is that the

overall level of safety of a lifting operation should not be reduced.

1.1.6 The Marine Warranty Surveyor for a project will be required to review the following for

any lifting operation requiring approval:

Design specifications

Proposed lifting procedure

Rigging design

Crane vessel details

1.1.7 This information should be made available to the Marine Warranty Surveyor in sufficient

time to enable the completion of these reviews well before the planned operations.


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1.2. Definitions

1.2.1 Company: Warranted Company or representatives acting on their behalf.

MWS: Marine Warranty Surveyor and/or Marine Warranty Survey Company. Installation Contractor: Shall mean the contractor who is responsible for the installation and marine lifting operations. Module: A structure or parts thereof subject to lifting. Sling: Steel ropes spun together with a spliced eye in each end. Grommet: Steel rope spun together and spliced such that there is no end. Dynamic Amplification Factor (DAF): A factor accounting for the global dynamic effects that may be experienced during lifting. Consequence Factor: An additional factor to be applied in assessing the structural strength of lifting points and primary structure. Module Design Weight (MDW): The maximum weight of the module including all relevant contingencies. Rigging Weight: The weight of all rigging, which will be lifted by the crane.

1.3. Reference Documents

1.3.1 MWS review of technical documents will include checks to current editions of relevant

codes and standards.

1.4. Certificates of Approval

1.4.1 The lifting design calculations and operations manuals shall be prepared well before the

planned start of operations and require approval by the MWS prior to the lifting operation

commencing.

1.4.2 An MWS Certificate of Approval for Lift shall be issued to the attending Surveyor

immediately prior to the lift when all preparations and checks are completed to his

satisfaction, and environmental conditions/weather forecast are suitable for the planned

duration of the operation.


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2. PLANNING OF MARINE LIFTS

2.1. General

2.1.1 The Installation Contractor shall prepare and issue a comprehensive lifting manual for

approval by the MWS. This manual may form part of an installation manual for the

module.

2.1.2 All planning for marine operations is based, where possible, on the principle that it may

be necessary to interrupt or reverse the operation. This is generally impractical for lifting

operations. Therefore points of no return, or thresholds, shall be defined during

planning and in the operations manual. Checklists should be drawn up detailing the

required status to be achieved before the operation proceeds to the next stage.

2.1.3 Operational planning shall be based on the use of well-proven principles, techniques,

systems and equipment to ensure acceptable health and safety levels are met and to

prevent the loss or injury to human life and major economic losses.

2.2. Site Survey

2.2.1 Drawings shall be prepared to document that the lifting site is suitable for the planned

lifting operation.

2.2.2 A drawing shall be prepared clearly showing existing pipelines and seabed obstructions.

The drawing shall also show the areas where mooring anchors cannot be placed.

2.3. Lifting Manual

2.3.1 A lifting manual shall be prepared and shall include, as a minimum, details of the

following:

Time schedule

Module dimensions

Module weight and COG information

Module buoyancy and COB information

Organization and communication

Site information

Crane vessel tugs and barges

Clearances module/crane/vessel/barge


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Crane vessel mooring and/or DP arrangement

Crane radius curve

Lifting equipment

Vessel handling procedures

Mooring arrangement

Pre-lift checklist

Description of operation

Limiting environmental criteria

Specific operations:

Barge/crane vessel ballasting

ROV

Survey and positioning

Suction and ventilation systems

Recording Procedure

Drawings

Safety and contingency plans

2.4. Documentation

2.4.1 The MWS requires to sight all relevant documentation related to the crane vessel

including but not limited to Classification and Statutory records and details of crane tests.

2.4.2 The MWS requires to be satisfied that all certificates for component parts of the rigging,

particularly slings, grommets and shackles, are valid. All slings and grommets shall

meet the requirement of Guidance Note PM 20 from the Health and Safety Executive

Cable laid slings and grommets' October 1987).

2.4.3 Documentation, which confirms that suitable tests of the welds on the lifting points have

been satisfactorily carried out, shall be available for inspection by the attending

Surveyor. If a module is lifted more than once, then a close visual inspection of the

lifting point welds shall, where access is possible, be carried out by a competent person

before the second and subsequent lifts.


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2.5. Design Calculations

2.5.1 Calculations prepared by the designers of the module, lifting points and rigging

arrangements shall be submitted for review. Generally, the calculations will be reviewed

and checked against the criteria contained herein.

2.5.2 Where computer analyses form the basis of the designers' submission, details of the

program and the basis of the input should be made available to assist the MWS in their

reviews and approval.

2.6. Operational Aspects

2.6.1 Before approving the lifting operation the MWS will require detailed descriptions and

specifications of the equipment involved and a comprehensive procedure for the lifting

operation.

2.6.2 Where the limiting criteria for a lift have been derived by dynamic analysis resulting in a

limiting criteria based on an allowable significant wave height, Hs, and associated wave

period it is recommended that a wave buoy or similar device is deployed at the lifting site

to allow accurate determination of the existing seastate.


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3. LOADS AND ANALYSIS

3.1. General

3.1.1 This section gives guidelines concerning the derivation of the loads for which the lifting

equipment, structure and crane vessels should be assessed.

3.1.2 The stages in the design or analysis of a lift are summarized in a flow chart in Appendix

1. The text of these guidelines should be read in conjunction with this chart.

3.2. Module Design Weight

3.2.1 The Module Design Weight (MDW) shall include adequate contingency factors to allow

for the module being heavier than intended. The MWS will require to review the

designers proposed overweight allowances; otherwise the following paragraphs give

recommended factors.

3.2.2 If the weight is being estimated at the design stage, then the weights of all components

of the module should be established by accurate material take-off and separated into

two parts:

Structural steel weight: To allow for mill tolerances, paint, weld, section size substitution

and future additions, the estimated weight of structural steel should be increased by

10%.

Weight of equipment and ancillaries: To allow for inaccuracies in the estimation of the

equipment weights and the unforeseen addition of equipment and associated steelwork,

such as equipment foundations and working platforms, the estimated weight of

equipment and ancillaries should be increased by 20%.

3.2.3 After completion, the module shall be weighed using an approved weighing method.

The as-weighed weight shall be increased by 3% to account for weighing inaccuracies.

Documentation should be provided to demonstrate that the equipment and procedures

adopted for weighing have the required accuracy.

3.2.4 Similarly, if the module is partially complete then the design lift weight may be

established by an approved weighing method and allowances for weighing inaccuracies

made. The weight of items which are not yet installed should then be established by an


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updated material take-off and an appropriate allowance made for inaccuracies and

possible future additions.

3.2.5 If the as-built weight plus contingency exceeds the module design weight, then

calculations shall be submitted to verify the lift design.

3.3. Rigging Weight

3.3.1 A further component, the Rigging Weight (RW), shall be added to the MDW. This

allowance represents the weight of rigging and shall include the estimated weight of all

shackles, slings, spreaders and rigging platforms. For preliminary design purposes an

assumed weight of rigging of 5% of a topsides module weight may be used (7% if

spreader bars are used). For jacket structures the weight assumed in the preliminary

design shall reflect the proposed rigging arrangement. In the final design phase the

actual weight of rigging (including contingencies) shall be used.

3.4. Centre of Gravity and Tilt of Module - Single Crane

3.4.1 The plan position of the centre of gravity shall generally be restricted for the following

reasons:

To allow for the use of matched pairs of slings

To prevent overstress of the crane hook

To control the maximum tilt of the object.

3.4.2 The Module COG should be kept within a design envelope. Figure 3.1 shows the

allowable zone within which the centre of gravity should be positioned.

3.4.3 The value of e' in Fig. 3.1 shall not exceed e = 0.02 x vertical distance from the crane

hook to the module centre of gravity. Where the vertical distance between the crane

hook and module centre of gravity is not initially known, the value of e' in Fig. 3.1 shall

not exceed 600mm. Where the centre of gravity is found to be outside the cruciform

shown in Fig. 3.1, the strength of the crane hook shall be shown to be sufficient for the

design load case.

3.4.4 The length of the lifting slings/grommets shall be chosen to control the tilt of the module.

For practical purposes the tilt of the module should not exceed 2 degrees.


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3.4.5 When the module has been weighed, the maximum tilt should be calculated using the

measured centre of gravity position and the certified lengths of the rigging arrangement.

Also, the relative offset between the centre hook position and the module centre of

gravity should be less than 600mm.

Figure 3.1 Allowable position of Centre of Gravity

3.5. Static Hook Load Single Crane Lift

3.5.1 The Rigging Weight (RW) shall be added to the Module Design Weight (MDW) to give

the Static Hook Load (SHL):

MDW + RW = SHL


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3.5.2 The Static Hook Load shall be checked against the approved crane capacity curve at the

maximum planned outreach.

3.5.3 Where the lifting situation may give rise to a dynamic increase in the effective load the

Dynamic Hook Load (DHL) shall be calculated in accordance with Section 3.7 below.

3.6. Static Hook Load - Dual Crane Lift

3.6.1 For dual crane lifts, the SHL for each crane shall be calculated as follows:

The SHL shall be the MDW shared between cranes in accordance with static

equilibrium, plus allowances of:

a) 5% of calculated hook load for offset of centre of gravity (comparing

actual with predicted); this value may be reduced to 3% after weighing.

b) 3% for longitudinal tilt of the lifted object during the lift

c) RW appropriate for the crane.

For subsea lifts using two hooks the buoyancy, hydrodynamic loads and wave slam

effects may alter the load distribution between the two hooks. These effects should be

taken into account when determining the individual hook loads.

3.6.2 The SHL shall be checked against the approved crane capacity curve at the maximum

planned outreach for each crane.

3.7. Dynamic Hook Load

3.7.1 The Dynamic Hook Load (DHL) shall be obtained by multiplying the SHL by a Dynamic

Amplification Factor (DAF):

DHL = SHL x DAF

3.7.2 The DAF allows for the dynamic loads arising from the relative motions of the crane

vessel and/or the cargo barge during the lifting operations.

3.7.3 The DHL shall be checked against the approved crane capacity curve at the maximum

planned outreach.


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3.7.4 For lifts in air the dynamic load is normally considered to be highest at the instant when

the module is being lifted off its grillage. This load, and hence the appropriate DAF,

should be substantiated by means of an analysis which considers the maximum relative

motions between the hook and the cargo barge takes account of the elasticity of the

crane falls, the slings, the crane booms and the luffing gear.

3.7.5 The description of such an analysis must clearly state the assumed limiting wave heights

and periods such that, if the calculated value of DAF is critical to the feasibility of the

operation, then those conducting the lift will be aware of the limiting seastates

3.7.6 For lifts with the module submerged, special investigations should be made taking

account of hydrostatic and hydrodynamic effects to calculate an appropriate DAF.

Further recommendations are given in section 3.10.

3.7.7 In the absence of a dynamic lift response analysis being carried out the values of DAF

given in Table 3.1 may be used for lifts in air using the semi-submersible crane vessels

Weight of Module < 100 Tonnes 100 1,000 Tonnes > 1,000 Tonnes

Lift Offshore 1.30 1.20 1.10

Lift Inshore 1.15 1.10 1.05

Table 3.1 DAF values for SSCV

3.7.8 For offshore lifts from the deck of a semi-submersible crane vessel the DAF appropriate

to an inshore lift may be used.

3.7.9 For lifts from a quayside a DAF of 1.0 may be used.

3.7.10 When using larger mono-hulled crane vessels, the values of DAF given in table 3.2 may

be used as a guideline.


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Weight of Module < 100 Tonnes 100 1,000 Tonnes > 1,000 Tonnes

Lift Offshore 1.50 1.40 1.30

Lift Inshore 1.30 1.20 1.15

Table 3.2 DAF values for large mono-hulled crane vessels

3.7.11 It should be noted that some crane capacity curves already take due account of the DAF

and care should be taken to ensure that the DAF is not considered twice in the design

calculations.

3.8. Derivation of Lifting Point Loads - Single Crane Lifts

3.8.1 Lifting points (padeyes or padears) are the structural elements which connect the lift

rigging to the structure of the module. Spreader bars may also be considered to have

lifting points where the slings or grommets are attached.

3.8.2 After specification of the lifting point locations and lift rigging lengths, the lifting point

loads shall be derived from the Design Lift Load (DLL) by consideration of the geometry

of the lifting arrangement and the position of the module centre of gravity:

DLL = MDW x DAF

3.8.3 An analysis shall be made to determine the load distribution between diagonally

opposite pairs of lifting points. This should include an assessment of the torsional

rigidity of the module and spring stiffness of the slings. In such an analysis it is

recommended that, in the absence of other information, the fabrication errors listed

below should be considered to occur in combination:

Lifting Points: Each lifting point is positioned 12mm from its correct position. The

combined effect of all lifting points being out of position shall be summed in the least

favorable manner

Shackles: Two shackles which are 6mm shorter than their standard dimensions are

attached to diagonally opposite padeyes, whilst 2 shackles which are 6mm longer than

standard are attached at the remaining diagonals.

Slings/Grommets: Slings/grommets that are 0.25% under specified nominal length

should be considered to be attached to two diagonally opposite lifting points, whilst


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slings/grommets that are 0.25% over specified nominal length are attached to the two

remaining lifting points.

3.8.4 If the above analysis is not carried out the DLL carried by a diagonally opposite pair of

lifting points shall be increased by a skew load factor of 1.5, i.e. the load shall be

distributed in the ratio 75/25 across opposite pairs of diagonals.

3.8.5 Where a loose spreader bar is used the skew load factor may be reduced to 1.2, i.e. the

load shall be distributed in the ratio 60/40 across opposite pairs of diagonals.

3.9. Derivation of Lifting Point Loads Using Two Crane

3.9.1 Lifting point loads for two cranes should be derived from the Design Lift Load in

accordance with the following principles.

3.9.2 The DLL is determined for each crane:

DLL = DHL - (RW x DAF)

3.9.3 For lift arrangements having four lift points i.e. two to each crane, the lift point loads are

statically determinate, and shall then be derived from the DLL by considering the

geometry of the sling arrangement. No skew load factor need be applied.

3.9.4 The lift point load shall be increased by 5% to allow for rotation (yaw) of the lifted object.

3.10. Lifting Through Water

3.10.1 This section applies to a module being lowered through the sea surface to its final

position on the seabed. These guidelines are in addition to the foregoing paragraphs.

3.10.2 The DAF and modified hook loads applicable when lifting through water shall be

determined taking account of the factors given below. The lift design shall be checked

accordingly.

3.10.3 The buoyancy and centre of buoyancy of the object shall be established on the basis of

accurate hydrostatic calculations.

3.10.4 For subsea modules, where wave loading may be significant, environmental loads shall

be established for wave conditions consistent with the design and operational criteria.


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An appropriate range of wavelengths and directions, including swell effects, shall be

considered. Wave slam effects in the splash zone shall also be evaluated, as shall the

possible uplift of the module and resulting slackening of slings.

3.10.5 Hydrostatic loads due to external pressure on the submerged module shall be

considered. The effect of hydrodynamic loads shall be calculated. For objects with

complex shapes, a 3D analysis should be carried out to determine the hydrodynamic co-

efficient.

3.10.6 The limiting operational criteria shall be established by considering the predicted motions

of the crane vessel for varying seastates and directions. This may be achieved either by

model testing or a suitable hydrodynamic analysis.

3.10.7 Module impact velocities, in horizontal and vertical directions, due to mating or

contacting the seabed, should not be taken as less than 1 m/s.

3.10.8 Forces due to current on the object and hoist lines should be evaluated and used to

derive off lead (forces away from the crane) and side lead (forces perpendicular to the

crane boom axis) loads.

3.10.9 At the preliminary design stage a DAF of 1.4 may be assumed for lifts of small structures

through water. For jackets a DAF of 1.2 may be assumed.


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4. STRUCTURES

4.1. General

4.1.1 The lifted object shall be designed in accordance with Standards or Codes of Practice

given in Section 1.3. Wherever possible, the design should be carried out to the

requirements of one code only.

4.2. LRFD and Consequence Factors

4.2.1 For Load and Resistance Factor Design (LRFD), the combined LRFD and Consequence

Factors as given in Table 4.1 below shall be applied to the structural elements in

addition to the factors for dynamic effects, weight tolerances, etc. given in Section 3.

4.2.2 A material resistance appropriate to the chosen Standard or Code shall be used.

4.2.3 For Working Stress Design (WSD), in addition to the factors for dynamic effects, weight

tolerances, etc given in Section 3, the consequence factors given in Table 4.1 shall be

applied for each element of the structure.

Structural Element Combined LRFD + Consequence Factor

Working Stress Consequence Factor

Lift points, spreader bars, etc.

1.50 1.0

Primary load transferring members

1.50 1.0

Other, secondary, members

1.15 1.0

Table 4.1 Consequence Factors

4.2.4 In Table 4.1, a member is considered as being primary if structural collapse could result

from failure of that member alone. Generally, primary members will be those members

framing directly into the lifting points. Other members are defined as being secondary.

4.3. Method of Analysis of Module

4.3.1 The module shall be analyzed as a three dimensional elastic space frame, including the

slings and appropriate restraints to prevent rigid body rotations. The structural model


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shall include all primary and secondary members and may take account of the bracing of

floor plating, if appropriate.

4.3.2 The loads input into the model shall represent structural and non-structural dead load,

equipment and finishes. The total input loads shall equal the module design weight,

including overweight contingencies, multiplied by the appropriate DAF.

4.3.3 For single hook lifts two load combinations shall be considered, representing the load

being distributed unevenly to each diagonally opposite pair of padeyes, as per Section

3.8 above. For dual hook lifts the design load shall be the lifting point loads as

determined in Section 3.9.

4.4. Strength of Module

4.4.1 The stresses in the member resulting from the lift analyses shall be evaluated and

compared with the design resistance or allowable stress of the member computed in

accordance with the appropriate design code.

4.5. Padeye Design

4.5.1 Padeyes shall be designed for the following loads:

Lifting point loads calculated in accordance with Section 3.8 and 3.9.

An additional lateral load equal to 5% of the lifting point load. This shall be assumed to

act horizontally at the level of the padeye pinhole.

Where a loose spreader bar is used in the rigging arrangement the additional lateral load

above shall be increased to 8%.

4.5.2 Padeyes shall be aligned to the theoretical true vertical sling angle but shall be

dimensioned for a sling angle tolerance of 5.

4.5.3 Wherever possible padeyes shall be designed with the main welds in shear rather than

tension. Where plates/sections are subjected to tensile loads applied perpendicular to

the rolling direction they shall have guaranteed through thickness properties.

4.5.4 Wherever possible the padeye main plate shall be continuous into the primary structure.


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4.5.5 Padeyes should not have more than one load-bearing cheek plate on each side of the

main plate. The cheek plate thickness should be no greater than the main plate

thickness.

4.5.6 Pin holes should be machined, and be line bored after the welding of the cheek plates to

the main plate

4.5.7 All sharp edges likely to damage the sling during handling and transportation shall be

radiused.

4.6. Padears and Trunnions

4.6.1 Padears and trunnions shall be designed for the following loads:

Loads calculated in accordance with Section 3.8 and 3.9 above. Additionally, where

doubled slings or grommets are used, a load split in the ratio 55%/45% between sling

legs shall be considered;

An additional lateral load equal to 5% of the lifting point load. The line of action of this

force shall be taken at centre of the trunnion, in the longitudinal and transverse

directions;

Where a loose spreader bar is used the additional lateral load above shall be increased

to 8%.

4.6.2 The central stiffener plate (shear plate) of the trunnion should be slotted through the

main plate and should be designed to transfer the total sling load into the main plate,

without taking the strength of the trunnion bearing plate into account.

4.6.3 The diameter of the trunnion shall be a minimum of 4 times the sling/grommet diameter

except where the reduction in strength due to bending losses has been considered.

4.6.4 Unless the lift point is profiled the sling will flatten out at the contact area during lifting.

Therefore, the width of a fabricated trunnion should be a minimum of 1.25 times the

overall sling diameter plus 25mm.

4.6.5 The trunnion shall be fitted with a sling retaining arrangement.

4.6.6 Padears shall be aligned to the theoretical true sling angle but shall be dimensioned for

a sling angle tolerance of 5, vertically and horizontally.


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4.6.7 All sharp edges likely to damage the sling during handling and transportation shall be

radiused.

4.7. Cast Lifting Points

4.7.1 The strength of cast lifting points shall be verified by finite element analyses.

4.7.2 The finished castings shall be subject to stringent quality control including dimensional

conformity, material properties and NDT.

4.8. Fabrication and Installation of Lifting Points

4.8.1 Fabrication and inspection of lifting points shall be in accordance with Company

structural steel fabrication and casting specifications.

4.9. Seafastening

4.9.1 Lift rigging, spreader bars and other temporary lifting equipment shall be seafastened for

transportation.

4.10. Bumpers and Guides

4.10.1 For offshore lifts consideration shall be given to the provision of bumpers and guides on

the modules. The bumpers and guides shall

Enable the object to be positioned after the lift within the required tolerances.

Protect the lifted object, the adjacent surroundings and equipment from damage during

lift.

4.10.2 Particular requirements for bumpers and guides should be determined at the planning

stage taking account of lifting procedures and the assessed risk of damage.

4.10.3 Fabrication tolerances of guides shall be closely controlled. Prior to lifting an as-built

dimensional survey of the guide systems shall be carried out to confirm that operational

tolerances have been maintained.

4.10.4 The design forces on bumpers and guides shall not be less than those given in Table

4.2.


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4.10.5 The bumpers and guides should be designed for any possible combination of forces,

except that the total force perpendicular to the face of the bumper need not exceed 1.1 x

MDW.

4.10.6 The requirements for design impact forces for stab-in guides (e.g. deck to jacket legs)

are given in Table 4.3.

4.10.7 The point of the Stab-in guide shall be designed to fail before damage can occur to the

receiving guide.

Force Bumpers Guides Pin/Bucket

Vertical forces due to friction 1% MDW 1% MDW 1% MDW

Vertical forces due to direct impact (Fv) (vertical post type) 10% MDW 10% MDW 10% MDW

Horizontal forces due to friction 1% MDW 1% MDW 1% MDW

Horizontal forces due to impact acting normal to face (Fh) 10% MDW 5% MDW 5% MDW

Horizontal forces due to impact acting parallel to the face (Fl) 5% MDW 5% MDW 5% MDW

Table 4.2 Bumper and guide impact force factors

For bumpers and guide designed as secondary systems the forces Fv, Fh and FI may be taken to be 50 % of those given in Table.4.2

Force Primary Secondary

Vertical forces due to direct impact 10% SHL 5% SHL

Horizontal forces due to direct impact in longitudinal direction of deck 10% SHL 5% SHL

Horizontal forces due to direct impact in transverse direction of deck 10% SHL 5% SHL

Table 4.3 Design forces for stab-in guides


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5. REQUIREMENTS FOR LIFTING EQUIPMENT

5.1. General

5.1.1 Cable laid rope for heavy offshore lifting shall be constructed and used in accordance

with the requirements of Guidance Note PM20, issued by the Health and Safety

Executive, entitled Cable Laid Slings and Grommets, or an equivalent standard.

5.1.2 The Safe Working Load of slings/grommets shall be calculated in accordance with PM20

taking due account of splicing efficiency and strength losses due to any bending of the

wire rope.

5.2. Sling Force Distribution

5.2.1 Doubled Slings: To take account of the friction losses where slings have been doubled

around the lifting or crane hook the total sling force shall be divided between the two

legs of the slings in the ratio 45/55%.

5.2.2 Grommets: When single grommets are used over a padear or trunnion, the total sling

load shall be divided between the two legs of the grommet in the ratio 45%/55%. This

ratio may be 50%/50% where sheaves are used in the system.

In cases where grommets are doubled between the hook and lifting point a distribution of

45%/55% shall be used between each leg and in addition a distribution of 50%/55%

between each pair, i.e. a design factor of 1.21 shall be used on the heaviest loaded

grommet leg.

5.2.3 Manufacturing and Tolerances: The wire rope construction shall be well suited for the

intended use and comply with recognized codes and standards.

The length of slings or grommets should normally be within tolerances of plus or minus

0.25% of their nominal length. During measuring, the slings or grommets should be fully

supported and adequately tensioned. The tension load should be in range of 2.5% to

5.0% of the MBL. Matched slings should be measured with the same tension load and

under similar conditions.

5.2.4 Construction and Certification: Valid certificates for each sling and grommet to be

used shall be supplied by the sling manufacturer and should be available for inspection

prior to installation of the slings or grommets on the lifted object.


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For cable laid slings and grommets the certificates required in accordance with PM20 are as

follows:

Consolidation Test Certificate that shall contain:

Identification details

Calculated and actual breaking load for outer and core ropes

Summation of breaking loads

Calculated sling or grommet breaking load

Calculation of Working Load Limit

Certificates of Dimensional Conformity

Certificates of Examination (The Certificate of Examination is valid for a period of 6

months)

5.2.5 Inspection and re-use of slings/grommets shall be examined by a competent person

prior to each use. Where the sling or grommet is not part of the vessel's approved

rigging gear, covered by an annual inspection by its Classification Society, then the

details of the history of the sling/grommet and a record of lifts for which the

slings/grommets have been previously used should be available.

5.2.6 The MWS acceptance is subject to a visual inspection of each sling/grommet prior to

and after rigging and tie-down is complete.

5.2.7 During sling lay down, particularly with cable laid rigging, care must be taken to avoid

any twisting of the slings/grommets. Where possible, a line should be painted along the

length of the sling/grommet during manufacture, to facilitate correct lay down of the

rigging.

5.2.8 If a sling/grommet is found to have any defects such that the certified Minimum Breaking

Load cannot be guaranteed, it shall not be used for lifting purposes.

5.3. Shackles

5.3.1 Each shackle shall be marked with its Safe Working Load (SWL) as recommended by

the manufacturer, who shall be a recognized shackle fabricator

5.3.2 A certificate verifying the proof loading and the SWL of each shackle shall be provided

for inspection by the MWS. These certificates shall be issued by a recognized Certifying


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Authority or testing. Each shackle shall be clearly stamped with an identifying mark with

reference to the corresponding certificate.

5.3.3 Shackles and their certification will be subject to an inspection by the attending MWS

surveyor prior to lift. T

5.3.4 The SWL of shackles, which are attached to lifting padeyes, shall not be less than the

lifting point load divided by the DAF.

5.3.5 Shackles shall be loaded along their centreline, in accordance with the design and load

rating principles to which the shackles were fabricated.

5.3.6 When selecting shackles for a particular application the proposed sling or grommet

diameter shall be taken into account.

5.4. Spreader Beams

5.4.1 The requirements of Section 4 shall also apply to the design and fabrication of spreader

beams where applicable.

5.5. Hydraulic Lifting Devices

5.5.1 Hydraulic Lifting Devices (HLD), such as pile lifting clamps, may also be used. The

points below should be taken into consideration when designing for such lifts.

5.5.2 The HLD should rate by the manufacturer. The SWL should be documented, preferably

by means of test results, in accordance with recognized standards. It shall be used in

accordance with the manufacturer's instructions and approved procedures.

5.5.3 The SWL of the HLD shall be greater than the Design Lift Load (See Chapter 3)

5.5.4 The HLD shall be designed to fail-safe. Thus failure of the hydraulic system during lift

(e.g. rupture of the control umbilical) shall not lead to the load being dropped. The lifting

manual shall document modes of failure and their effects and the appropriate

contingency measures.

5.5.5 The lifting forces from the HLD to the lifting points should be transmitted in accordance

with these guidelines and the code of practice being used in the design of the structural

steelwork.


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6. CRANE AND CRANE VESSELS

6.1. General

6.1.1 The crane, crane vessel and associated equipment shall be fit to perform the planned lift

operations in a safe manner.

6.1.2 The crane should be equipped with an accurate load-monitoring device, sufficient to

measure cyclic dynamic loads.

6.2. Allowable Load

6.2.1 Prior to lift, the correct value of the Module Design Weight shall be confirmed using the

as-weighed module weight or updated estimates of weight.

6.2.2 The Dynamic Hook Load, which includes the DAF, shall be compared to the crane

radius curve, adopting the maximum radius to be used for the lift.

6.2.3 It shall be demonstrated, by reference to the crane certification, or by calculation of

allowable stress levels and safety factors within the components of the crane and its

foundations, that the crane has adequate capacity to carry out the lift.

6.3. Crane Radius Curve

6.3.1 A part of the submission made to the MWS for approval purposes shall be a crane

radius curve showing the allowable lift capacity of the crane at different lift radii.

6.3.2 The crane capacity shall be as specified by the manufacturer of the crane and shall have

been validated by a proof load test wherein the crane is loaded to 10% in excess of the

crane radius curve. A statement that the crane is in class with a Certification Authority is

sufficient confirmation that such a test was carried out.

6.4. Minimum Clearances

6.4.1 During all phases of a lift the following minimum clearances should be maintained:

Below module: 3m

Between module and crane boom: 3m

Between spreader bar and crane boom: 3m


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6.4.2 For offshore lifts:

From crane vessel to platform: 3m

From crane vessel to platform: 10 m (Crane vessel on DP)

6.5. Crane Vessel Stability

6.5.1 If the design hook load is less than 80% of the capacity of the cranes and the crane

vessel will perform the lift at its normal working draft then no special submission is

required by the MWS with regard to stability. However, if the load is near the maximum

allowable for the vessel or the vessel will be at a draft outside its normal operational

range a stability statement shall be submitted for review.

6.5.2 When carrying out tandem lifts, documentation shall be submitted to demonstrate that

the crane vessel can safely sustain the changes in hook load which arise from the tilt

and yaw factors combined with environmental effects in the lifting calculations,

specifically considering allowable cross lead angles for the crane booms.


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Appendix A1 Summary of Stages in Design/Analysis of Lift Using Single Crane.

3.2.

Module Design Weight (MDW)

3.3. Rigging Weight (RW)

(3.7) SHL x DAF = Dynamic Hook Load (DHL)

(3.5) MDW + RW = Static Hook Load (SHL)

(3.4) Check COG Position & Tilt

(5.) Rigging Design

(3.8) MDW x DAF = Design Lift Load (DLL)

(4.) Module Structural Strength

(4.5 4.8) Lifting Point Design

Check Crane Capacity

4.2 Combined LRFD + Working Stress Consequence Factors for: Consequence Factor Consequence Factor

(a) Lifting Points, Spreader Bars 1.50 1.0 (b) Primary Members 1.50 1.0 (c) Secondary Members 1.15 1.0 ( increase allowed)

(3.8) Lifting Point Forces


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Appendix A2 Summary of Stages in Design/Analysis of Lift Using Two Cranes

(3.2) Module Design Weight (MDW)

(3.9) Lifting Point Forces

(3.7) Dynamic Hook Load (DHL) = SHL x DAF

(5.) Rigging Design

3.6 Static Hook Load (SHL) = (MDW x a (1) x 1.05i(2) x 1.03(3) ) + Rigging Weight Where: (1) is the ratio of the cog position to the length between lift points (2) is the factor to allow for cog shift (3) is the factor to allow for longitudinal tilt

(3.9) DLL = {DHL (RW x DAF)}

Check Crane Capacity

(4.2) Combined LRFD + Working Stresses Consequence Factors for: Consequence Factor Consequence Factor (a) Lifting Points, Spreader Bars 1.50 1.0 (b) Primary Members 1.50 1.0 (c) Secondary Members 1.15 1.0 ( increase allowed)

(4.3 4.4) Module Structural Strength

(4.5 4.8) Lifting Point Design

(3.9) Lift Point Load = DLL x 1.05(1) where: (1) is the factor to allow for yaw

loc guidelines for marine operations - lifting

Documents

lifting equipment

installation of lifting

title marine lifting

hydraulic lifting devices

planning of marine lifts

marine warranty surveyors

crane vessels

good marine practice