Loc Guidelines for Marine Lifting

GUIDELINES FORMARINE OPERATIONS

MARINE LIFTING

February 1998

London Offshore ConsultantsGUIDELINES FOR MARINE OPERATIONS

LIFTING

TABLE OF CONTENTS

1. INTRODUCTION................................................................................................................... 4

1.1 Scope of Guidelines1.2 Definitions1.3 Reference Documents1.4 Certificates of Approval

2. PLANNING OF MARINE LIFTS........................................................................................ 7

2.1 General2.2 Site Survey2.3 Lifting Manual2.4 Documentation2.5 Design Calculations2.6 Operational Aspects

3. LOADS AND ANALYSIS...................................................................................................... 9

3.1 General3.2 Module Design Weight3.3 Rigging Weight3.4 Centre of Gravity and Tilt of Module - Single Crane3.5 Static Hook Load - Single Crane Lift3.6 Static Hook Load - Dual Crane Lift3.7 Dynamic Lift Load3.8 Derivation of Lifting Point Loads - Single Crane Lifts3.9 Derivation of Lifting Point Loads - Dual

Crane Lifts 3.10 Lifting Through Water

4. STRUCTURES...................................................................................................................... 16

4.1 General4.2 Consequence Factors4.3 Method of Analysis of Module4.4 Strength of Module4.5 Padeye Design4.6 Padears and Trunnions4.7 Cast Lifting Points4.8 Fabrication and Installation of Lifting Points4.9 Seafastening4.10 Bumpers and Guides

London Offshore ConsultantsGUIDELINES FOR MARINE OPERATIONS

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5. REQUIREMENTS FOR LIFTING EQUIPMENT ......................................................... 21

5.1 General5.2 Sling Force Distribution 5.3 Shackles5.4 Spreader Beams5.5 Hydraulic Lifting Devices

6. CRANE AND CRANE VESSELS ...................................................................................... 24

6.1 General6.2 Allowable Load6.3 Crane Radius Curve6.4 Minimum Clearances6.5 Crane Vessel Stability

APPENDICES

Appendix A1: Summary of Stages in Design/Analysis of Single Crane LiftAppendix A2: Summary of Stages in Design/Analysis of Dual Crane Lift

London Offshore Consultants Page 1 of 25GUIDELINES FOR MARINE OPERATIONS

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GuidLFT. February 1996

1. INTRODUCTION

1.1 SCOPE OF GUIDELINES

These guidelines are a basis for the planning, design and operational aspects of marinelifting. Guidelines for loadout and transportation are covered in the two precedingchapters.

The purpose of them is to specify appropriate standards, based on sound engineering andgood marine practice in order to ensure that lifting operations maintain an acceptable levelof safety at all times.

These guidelines are intended to cover any lifting operations which are subject to approvalby the Marine Warranty Surveyor. For example:-

C Topsides Module LiftingC Subsea Structure LiftingC Jacket Lifting

Other considerations may apply for other categories of lift.

These guidelines are based on experience over a large number of lifting operations. However, as knowledge advances in specific areas, Marine Warranty Surveyors shouldrecognise that lifting operations may use alternative or new methods. The fundamentalprinciple to be followed by the introduction of novel or alternative methods is that theoverall level of safety of a lifting operation should not be reduced.

The Marine Warranty Surveyor for a project will require to review the following for anylifting operation requiring approval:-

C Design specificationsC Proposed lifting procedureC Rigging designC Crane vessel details

This information should be made available to the MWS in sufficient time to enablecompletion of these reviews well before the planned operations.

1.2 DEFINITIONS

Company:Warranted Company or representatives acting on their behalf.


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MWS:Marine Warranty Surveyor and/or Marine Warranty Survey Company.

Installation Contractor:Shall mean the contractor who is responsible for the installation and marine liftingoperations.

Module:A structure or parts thereof subject to lifting.

Sling:Steel ropes spun together with a spliced eye in each end.

Grommet:Steel report spun together and spliced such that there is no end.

Dynamic Amplification Factor (DAF):A factor accounting for the global dynamic effects which may be experienced duringlifting.

Consequence Factor:An additional factor to be applied in assessing the structural strength of lifting points andprimary 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

MWS review of technical documents will include checks to current editions of relevantcodes and standards.

1.4 CERTIFICATES OF APPROVAL

The lifting design calculations and operations manuals shall be prepared well before theplanned start of operations and require approval by the MWS prior to the lifting operationcommencing.


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A MWS Certificate of Approval for Lift shall be issued to the attending Surveyorimmediately prior to the lift when all preparations and checks are completed to hissatisfaction, and environmental conditions/weather forecast are suitable for the plannedduration of the operation.


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2. PLANNING OF MARINE LIFTS

2.1 GENERAL

The Installation Contractor shall prepare and issue a comprehensive lifting manual forapproval by the MWS. This manual may form part of an installation manual for theModule.

All planning for marine operations is based, where possible, on the principle that it may benecessary to interrupt or reverse the operation. This is generally impractical for liftingoperations. Therefore points of `no return', or thresholds, shall be defined during planningand in the operations manual. Checklists should be drawn up detailing the required statusto be achieved before the operation proceeds to the next stage.

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

2.2 SITE SURVEY

Drawings shall be prepared to document that the lifting site is suitable for the plannedlifting operation.

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

A lifting manual shall be prepared and shall include, as a minimum, details of thefollowing:-

C Time scheduleC Module dimensionsC Module weight and COG informationC Module buoyancy and COB informationC Organisation and communicationC Site informationC Crane vessel tugs and bargesC Clearances module/crane/vessel/bargeC Crane vessel mooring and/or DP arrangement


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C Crane radius curveC Lifting equipmentC Vessel handling proceduresC Mooring arrangementC Pre-lift checklistC Description of operationC Limiting environmental criteriaC Specific operations:

Barge/crane vessel ballastingROVSurvey and positioningSuction and ventilation systems

C Recording ProcedureC DrawingsC Safety and contingency plans

2.4 DOCUMENTATION

The MWS requires to sight all relevant documentation related to the crane vesselincluding but not limited to Classification and Statutory records and details of crane tests.

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 meetthe requirement of Guidance Note PM 20 from the Health and Safety Executive - `Cablelaid slings and grommets' (October 1987).

Documentation which confirms that suitable tests of the welds on the lifting points havebeen 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 pointwelds shall, where access is possible, be carried out by a competent person before thesecond and subsequent lifts.

2.5 DESIGN CALCULATIONS

Calculations prepared by the designers of the Module, lifting points and riggingarrangements shall be submitted for review. Generally, the calculations will be reviewedand checked against the criteria contained herein.

Where computer analyses form the basis of the designers' submission, details of theprogram and the basis of the input should be made available to assist the MWS in theirreviews and approval.


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2.6 OPERATIONAL ASPECTS

Before approving the lifting operation the MWS will require detailed descriptions andspecifications of the equipment involved and a comprehensive procedure for the liftingoperation.

Where the limiting criteria for a lift have been derived by dynamic analysis resulting in alimiting criteria based on an allowable significant waveheight, Hs, and associated waveperiod it is recommended that a wave buoy or similar device is deployed at the lifting siteto allow accurate determination of the existing seastate.


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3. LOADS AND ANALYSIS

3.1 GENERAL

This section gives guidelines concerning the derivation of the loads for which the liftingequipment, structure and crane vessels should be assessed.

The stages in the design or analysis of a lift are summarised 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

The Module Design Weight (MDW) shall include adequate contingency factors to allowfor the module being heavier than intended. The MWS will require to review thedesigners' proposed overweight allowances, otherwise the following paragraphs giverecommended factors.

If the weight is being estimated at the design stage, then the weights of all components ofthe module should be established by accurate material take-off and separated into twoparts:-

C Structural steel weight. To allow for mill tolerances, paint, weld, section sizesubstitution and future additions, the estimated weight of structural steel should beincreased by 10%.

C Weight of equipment and ancillaries. To allow for inaccuracies in the estimation ofthe equipment weights and the unforeseen addition of equipment and associatedsteelwork, such as equipment foundations and working platforms, the estimatedweight of equipment and ancillaries should be increased by 20%.

After completion, the module shall be weighed using an approved weighing method. Theas-weighed weight shall be increased by 3% to account for weighing inaccuracies.Documentation should be provided to demonstrate that the equipment and proceduresadopted for weighing have the required accuracy.

Similarly, if the module is partially complete then the design lift weight may beestablished by an approved weighing method and allowances for weighing inaccuraciesmade. The weight of items which are not yet installed should then be established by anupdated material take-off and an appropriate allowance made for inaccuracies and possiblefuture additions.


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If the as-built weight plus contingency exceeds the module design weight then calculationsshall be submitted to verify the lift design.

3.3 RIGGING WEIGHT

A further component, the Rigging Weight (RW), shall be added to the MDW. Thisallowance represents the weight of rigging and shall include the estimated weight of allshackles, slings, spreaders and rigging platforms. For preliminary design purposes anassumed weight of rigging of 5 percent of a topsides Module weight may be used (7% ifspreader bars are used). For jacket structures the weight assumed in the preliminarydesign shall reflect the proposed rigging arrangement. In the final design phase the actualweight of rigging (including contingencies) shall be used.

3.4 CENTRE OF GRAVITY AND TILT OF MODULE - SINGLE CRANE

The plan position of the centre of gravity shall generally be restricted for the followingreasons:

C To allow for the use of matched pairs of slingsC To prevent overstress of the crane hookC To control the maximum tilt of the object.

The Module COG should be kept within a design envelope. Figure 3.1 shows theallowable zone within which the centre of gravity should be positioned.

The value of `e' in Fig. 3.1 shall not exceed e = 0.02 x vertical distance from the cranehook to the Module centre of gravity. Where the vertical distance between the crane hookand Module centre of gravity is not initially known, the value of `e' in Fig. 3.1 shall notexceed 600mm. Where the centre of gravity is found to be outside the cruciform shown inFig. 3.1, the strength of the crane hook shall be shown to be sufficient for the design loadcase.

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 2E.

When the Module has been weighed, the maximum tilt should be calculated using themeasured 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 gravityshould be less than 600mm.


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Figure 3.1 Allowable position of Centre of Gravity

3.5 STATIC HOOK LOAD - SINGLE CRANE LIFT

The Rigging Weight (RW) shall be added to the Module Design Weight (MDW) to givethe Static Hook Load (SHL):-

C MDW + RW = SHL

The Static Hook Load shall be checked against the approved crane capacity curve at themaximum planned outreach.

Where the lifting situation may give rise to a dynamic increase in the effective load theDynamic Hook Load (DHL) shall be calculated in accordance with Section 3.7 below.


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3.6 STATIC HOOK LOAD - DUAL CRANE LIFT

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

C The SHL shall be the MDW shared between cranes in accordance with staticequilibrium, plus allowances of:-

- 5% of calculated hook load for offset of centre of gravity (comparing actualwith predicted); this value may be reduced to 3% after weighing.

- 3% for longitudinal tilt of the lifted object during the lift.- RW appropriate for the crane.

C For subsea lifts using two hooks the buoyancy, hydrodynamic loads and wave slameffects may alter the load distribution between the two hooks. These effects shouldbe taken into account when determining the individual hook loads.

The SHL shall be checked against the approved crane capacity curve at the maximumplanned outreach for each crane.

3.7 DYNAMIC HOOK LOAD

The Dynamic Hook Load (DHL) shall be obtained by multiplying the SHL by a DynamicAmplification Factor (DAF):-

C DHL = SHL x DAF

The DAF allows for the dynamic loads arising from the relative motions of the cranevessel and/or the cargo barge during the lifting operations.

The DHL shall be checked against the approved crane capacity curve at the maximumplanned outreach.

For lifts in air the dynamic load is normally considered to be highest at the instant whenthe 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 relativemotions between the hook and the cargo barge takes account of the elasticity of the cranefalls, the slings, the crane booms and the luffing gear.

The description of such an analysis must clearly state the assumed limiting wave heightsand periods such that, if the calculated value of DAF is critical to the feasibility of theoperation, then those conducting the lift will be aware of the limiting sea states.

For lifts with the Module submerged, special investigations should be made takingaccount of hydrostatic and hydrodynamic effects to calculate an appropriate DAF. Further


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recommendations are given in section 3.10.

In the absence of a dynamic lift response analysis being carried out the values of DAFgiven in Table 3.1 may be used for lifts in air using the semisubmersible crane vessels.

Weight of Module < 100 Tonne 100 - 1000 Tonne > 1000 Tonne

Lift Offshore 1.30 1.20 1.10

Lift Inshore 1.15 1.10 1.05

Table 3.1 DAF values for SSCV

For offshore lifts from the deck of a semisubmersible crane vessel the DAFappropriate to an inshore lift may be used.

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

When using larger mono-hulled crane vessels, the values of DAF given in table 3.2may be used as a guideline.

Weight of Module < 100 Tonne 100 - 1000 Tonne > 1000 Tonne

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

It should be noted that some crane capacity curves already take due account of theDAF and care should be taken to ensure that the DAF is not considered twice in thedesign calculations.

3.8 DERIVATION OF LIFTING POINT LOADS - SINGLE CRANE LIFTS

Lifting points (padeyes or padears) are the structural elements which connect thelift rigging to the structure of the Module. Spreader bars may also be considered tohave lifting points where the slings or grommets are attached.

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


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point loads shall be derived from the Design Lift Load (DLL) by consideration of thegeometry of the lifting arrangement and the position of the Module centre of gravity:-

C DLL = MDW x DAF

An analysis shall be made to determine the load distribution between diagonallyopposite pairs of lifting points. This should include an assessment of the torsionalrigidity of the Module and spring stiffness of the slings. In such an analysis it isrecommended that, in the absence of other information, the fabrication errors listedbelow should be considered to occur in combination:-

C Lifting Points. Each lifting point is positioned 12mm from its correctposition. The combined effect of all lifting points being out of position shall besummed in the least favourable manner.

C Shackles. Two shackles which are 6mm shorter than their standarddimensions are attached to diagonally opposite padeyes, whilst 2 shackles whichare 6mm longer than standard are attached at the remaining diagonals.

C Slings/Grommets. Slings/grommets which are 0.25% under specifiednominal length should be considered to be attached to two diagonally oppositelifting points, whilst slings/grommets which are 0.25% over specified nominallength are attached to the two remaining lifting points.

If the above analysis is not carried out the DLL carried by a diagonally oppositepair of lifting points shall be increased by a skew load factor of 1.5, ie the load shall bedistributed in the ratio 75/25 across opposite pairs of diagonals.

Where a loose spreader bar is used the skew load factor may be reduced to 1.2, iethe load shall be distributed in the ratio 60/40 across opposite pairs of diagonals.

3.9 DERIVATION OF LIFTING POINT LOADS - DUAL CRANE LIFTS

Lifting point loads for dual hook lifts should be derived from the Design Lift Loadin accordance with the following principles.

The DLL is determined for each crane:-

C DLL = DHL - (RW x DAF)

For lift arrangements having four lift points ie two to each crane, the lift point loadsare statically determinate, and shall then be derived from the DLL by considering thegeometry of the sling arrangement. No skew load factor need be applied.


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

3.10 LIFTING THROUGH WATER

This section applies to a Module being lowered through the sea surface to its finalposition on the seabed. These guidelines are in addition to the foregoing paragraphs.

The DAF and modified hook loads applicable when lifting through water shall bedetermined taking account of the factors given below. The lift design shall be checkedaccordingly.

The buoyancy and centre of buoyancy of the object shall be established on the basisof accurate hydrostatic calculations.

For subsea Modules, where wave loading may be significant, environmental loadsshall be established for wave conditions consistent with the design and operationalcriteria. An appropriate range of wave lengths and directions, including swell effects,shall be considered. Wave slam effects in the splash zone shall also be evaluated, asshall the possible uplift of the module and resulting slackening of slings.

Hydrostatic loads due to external pressure on the submerged Module shall beconsidered. The effect of hydrodynamic loads shall be calculated. For objects withcomplex shapes, a 3D analysis should be carried out to determine the hydrodynamiccoefficients.

The limiting operational criteria shall be established by considering the predictedmotions of the crane vessel for varying seastates and directions. This may be achievedeither by model testing or a suitable hydrodynamic analysis.

Module impact velocities, in horizontal and vertical directions, due to mating orcontacting the seabed, should not be taken as less than 1 m/s.

Forces due to current on the object and hoist lines should be evaluated and used toderive off lead (forces away from the crane) and side lead (forces perpendicular to thecrane boom axis) loads.

At the preliminary design stage a DAF of 1.4 may be assumed for lifts of smallstructures through water. For jackets a DAF of 1.2 may be assumed.


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4. STRUCTURES

4.1 GENERAL

The lifted object shall be designed in accordance with Standards or Codes ofPractice given in Section 1.3. Wherever possible, the design should be carried out tothe requirements of one code only.

4.2 LRFD AND CONSEQUENCE FACTORS

For Load and Resistance Factor Design (LRFD), the combined LRFD andConsequence Factors as given in Table 4.1 below shall be applied to the structuralelements in addition to the factors for dynamic effects, weight tolerances, etc. given inSection 3.

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

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 4.1shall be applied for each element of the structure.

Structural Element CombinedLRFD +

ConsequenceFactor

Working StressConsequence

Factor

Lift points, spreader bars, etc. 1.50 1.0

Primary load transferring members 1.50 1.0

Other, secondary, members 1.15 (1)

Table 4.1 Consequence Factors

In Table 4.1, a member is considered as being primary if structural collapse couldresult from failure of that member alone. Generally, primary members will be thosemembers framing directly into the lifting points. Other members are defined as beingsecondary.


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4.3 METHOD OF ANALYSIS OF MODULE

The Module shall be analysed as a three dimensional elastic space frame, includingthe slings and appropriate restraints to prevent rigid body rotations. The structuralmodel shall include all primary and secondary members and may take account of thebracing of floor plating, if appropriate.

The loads input into the model shall represent structural and non-structural deadload, equipment and finishes. The total input loads shall equal the Module designweight, including overweight contingencies, multiplied by the appropriate DAF.

For single hook lifts two load combinations shall be considered, representing theload being distributed unevenly to each diagonally opposite pair of padeyes, as perSection 3.8 above. For dual hook lifts the design load shall be the lifting point loadsas determined in Section 3.9.

4.4 STRENGTH OF MODULE

The stresses in the member resulting from the lift analyses shall be evaluated andcompared with the design resistance or allowable stress of the member computed inaccordance with the appropriate design code.

4.5 PADEYE DESIGN

Padeyes shall be designed for the following loads:-

C Lifting point loads calculated in accordance with section 3.8 and 3.9 above.C An additional lateral load equal to 5% of the lifting point load. This shall beassumed to act horizontally at the level of the padeye pinhole.C Where a loose spreader bar is used in the rigging arrangement the additionallateral load above shall be increased to 8%.

Padeyes shall be aligned to the theoretical true vertical sling angle but shall bedimensioned for a sling angle tolerance of " 5E.

Wherever possible padeyes shall be designed with the main welds in shear ratherthan tension. Where plates/sections are subjected to tensile loads appliedperpendicular to the rolling direction they shall have guaranteed through thicknessproperties.

Wherever possible the padeye main plate shall be continuous into the primarystructure.


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Padeyes should not have more than one load-bearing cheek plate on each side ofthe main plate. The cheek plate thickness should be no greater than the main platethickness.

Pin holes should be machined, and be line bored after the welding of the cheekplates to the main plate

All sharp edges likely to damage the sling during handling and transportation shallbe radiused.

4.6 PADEARS AND TRUNNIONS

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

C 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;

C An additional lateral load equal to 5% of the lifting point load. The line ofaction of this force shall be taken at centre of the trunnion, in the longitudinaland transverse directions;

C Where a loose spreader bar is used the additional lateral load above shall beincreased to 8%.

The central stiffener plate (shear plate) of the trunnion should be slotted through themain plate and should be designed to transfer the total sling load into the mainplate, without taking the strength of the trunnion bearing plate into account.

The diameter of the trunnion shall be a minimum of 4 times the sling/grommetdiameter except where the reduction in strength due to bending losses has beenconsidered.

Unless the lift point is profiled the sling will flatten out at the contact area duringlifting. Therefore the width of a fabricated trunnion should be a minimum of 1.25times the overall sling diameter plus 25mm.

The trunnion shall be fitted with a sling retaining arrangement.

Padears shall be aligned to the theoretical true sling angle but shall be dimensionedfor a sling angle tolerance of " 5E, vertically and horizontally.

All sharp edges likely to damage the sling during handling and transportation shallbe radiused.

London Offshore Consultants Page 17of 25GUIDELINES FOR MARINE OPERATIONS

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4.7 CAST LIFTING POINTS

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

The finished castings shall be subject to stringent quality control includingdimensional conformity, material properties and NDT.

4.8 FABRICATION AND INSTALLATION OF LIFTING POINTS

Fabrication and inspection of lifting points shall be in accordance with Companystructural steel fabrication and casting specifications.

4.9 SEAFASTENING

Lift rigging, spreaderbars and other temporary lifting equipment shall beseafastened for transportation.

4.10 BUMPERS AND GUIDES

For offshore lifts consideration shall be given to the provision of bumpers andguides on the Modules. The bumpers and guides shall:-

C Enable the object to be positioned after the lift within the required tolerances.C Protect the lifted object, the adjacent surroundings and equipment from

damage during lift.

Particular requirements for bumpers and guides should be determined at theplanning stage taking account of lifting procedures and the assessed risk of damage.

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 thatoperational tolerances have been maintained.

The design forces on bumpers and guides shall not be less than those given in Table4.2.

The bumpers and guides should be designed for any possible combination offorces, except that the total force perpendicular to the face of the bumper need notexceed 1.1 x MDW.


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The requirements for design impact forces for stab-in guides (eg deck to jacketlegs) are given in Table 4.3.

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

Force Bumpers Guides Pin/Bucket

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

Vertical forces due to directimpact (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 impactacting normal to face (Fh)

10% MDW 5% MDW 5% MDW

Horizontal forces due to impactacting parallel to the face (Fl)

5% MDW 5% MDW 5% MDW

Table 4.2 Bumper and guide impact force factors

Force Primary Secondary

Vertical forces due todirect impact

10% SHL 5% SHL

Horizontal forces due todirect impact inlongitudinal direction ofdeck

10% SHL 5% SHL

Horizontal forces due todirect impact in transversedirection 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

Cable laid rope for heavy offshore lifting shall be constructed and used inaccordance with the requirements of Guidance Note PM20, issued by the Healthand Safety Executive, entitled Cable Laid Slings and Grommets, or an equivalentstandard.

The Safe Working Load of slings/grommets shall be calculated in accordance withPM20 taking due account of splicing efficiency and strength losses due to anybending 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 thelifting or crane hook the total sling force shall be divided between the two legs ofthe slings in the ratio 45%/55%.

5.2.2 Grommets

When single grommets are used over a padear or trunnion, the total sling load shallbe divided between the two legs of the grommet in the ratio 45%/55%. This ratiomay be 50%/50% where sheaves are used in the system.

In cases where grommets are doubled between the hook and lifting point adistribution of 45%/55% shall be used between each leg and in addition adistribution of 45%/55% between each pair, ie a design factor of 1.21 shall be usedon the heaviest loaded grommet leg.

5.2.3 Manufacturing and Tolerances

The wire rope construction shall be well suited for the intended use and complywith recognised codes and standards.

The length of slings or grommets should normally be within tolerances of plus orminus 0.25 per cent of their nominal length. During measuring, the slings orgrommets should be fully supported and adequately tensioned. The tension loadshould be in range of 2.5% to 5.0% of the MBL. Matched slings should be


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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 thesling Manufacturer and should be available for inspection prior to installation of theslings or grommets on the lifted object.

For cable laid slings and grommets the certificates required in accordance withPM20 are as follows:-

C Consolidation Test Certificate which shall contain;Identification detailsCalculated and actual breaking load for outer and core ropesSummation of breaking loadsCalculated sling or grommet breaking load

C Calculation of Working Load LimitC Certificates of Dimensional ConformityC 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

Slings/grommets shall be examined by a competent person prior to each use. Wherethe sling or grommet is not part of the vessel's approved rigging gear, covered by anannual inspection by its Classification Society, then the details of the history of thesling/grommet and a record of lifts for which the slings/grommets have beenpreviously used should be available.

The MWS acceptance is subject to a visual inspection of each sling/grommet priorto and after rigging and tie-down is complete.

If a sling/grommet is found to have any defects such that the certified MinimumBreaking Load cannot be guaranteed, it shall not be used for lifting purposes.

5.3 SHACKLES

Each shackle shall be marked with its Safe Working Load (SWL) as recommendedby the manufacturer, who shall be a recognised shackle fabricator.

A certificate verifying the proof loading and the SWL of each shackle shall beprovided for inspection by the MWS. These certificates shall be issued by arecognised Certifying Authority or testing house. Each shackle shall be clearly


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stamped with an identifying mark with reference to the corresponding certificate.

Shackles and their certification will be subject to an inspection by the attending MWS surveyor prior to lift.

The SWL of shackles which are attached to lifting padeyes shall not be less than thelifting point load divided by the DAF.

Shackles shall be loaded along their centreline, in accordance with the design andload rating principles to which the shackles were fabricated.

When selecting shackles for a particular application the proposed sling or grommetdiameter shall be taken into account.

5.4 SPREADER BEAMS

The requirements of Section 4 shall also apply to the design and fabrication ofspreader beams where applicable.

5.5 HYDRAULIC LIFTING DEVICES

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.

The HLD should be rated by the manufacturer. The SWL should be documented,preferably by means of test results, in accordance with recognised standards. Itshall be used in accordance with the manufacturer's instructions and approvedprocedures.

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

The HLD shall be designed to fail safe. Thus failure of the hydraulic system duringlift (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 theappropriate contingency measures.

The lifting forces from the HLD to the lifting points should be transmitted inaccordance with these guidelines and the code of practice being used in the designof the structural steelwork.


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6. CRANE AND CRANE VESSELS

6.1 GENERAL

The crane, crane vessel and associated equipment shall be fit to perform theplanned lift operations in a safe manner.

The crane should be equipped with an accurate load monitoring device, sufficientto measure cyclic dynamic loads.

6.2 ALLOWABLE LOAD

Prior to lift, the correct value of the Module Design Weight shall be confirmedusing the as-weighed Module weight or updated estimates of weight.

The Dynamic Hook Load, which includes the DAF, shall be compared to the craneradius curve, adopting the maximum radius to be used for the lift.

It shall be demonstrated, by reference to the crane certification, or by calculation ofallowable stress levels and safety factors within the components of the crane and itsfoundations, that the crane has adequate capacity to carry out the lift.

6.3 CRANE RADIUS CURVE

A part of the submission made to the MWS for approval purposes shall be a craneradius curve showing the allowable lift capacity of the crane at different lift radii.

The crane capacity shall be as specified by the manufacturer of the crane and shallhave been validated by a proof load test wherein the crane is loaded to 10% inexcess of the crane radius curve. A statement that the crane is in class with aCertification Authority is sufficient confirmation that such a test was carried out.

6.4 MINIMUM CLEARANCES

During all phases of a lift the following minimum clearances should bemaintained:-


LIFTING


C Below Module: 3 mC Between Module and crane boom: 3 mC Between spreader bar and crane boom : 3 m

For offshore lifts:

C From crane vessel to platform : 3 m

6.5 CRANE VESSEL STABILITY

If the design hook load is less than 80% of the capacity of the cranes and the cranevessel will perform the lift at its normal working draft then no special submission isrequired by the MWS with regard to stability. However, if the load is near themaximum allowable for the vessel or the vessel will be at a draft outside its normaloperational range a stability statement shall be submitted for review.

When carrying out tandem lifts, documentation shall be submitted to demonstratethat the crane vessel can safely sustain the changes in hook load which arise fromthe tilt and yaw factors combined with environmental effects in the liftingcalculations, specifically considering allowable cross lead angles for the cranebooms.

London Offshore Consultants Appendices

GUIDELINES FOR MARINE OPERATIONS

LIFTING


APPENDIX 1

LIFTING DESIGN FLOW CHARTS



LIFTING


(3.2) Module Design Weight (MDW)

(3.3)Rigging Weight(RW)

(3.4)Check COGPosition & Tilt

(3.5)MDW + RW = StaticHook Load (SHL)

Check CraneCapacity

(3.7)SHL x DAF =Dynamic HookLoad (DHL)

(3.8)MDW x DAF = DesignLift Load (DLL)

(5.)Rigging Design

(3.8)Lifting Point Forces

(4.2) Combined LRFD + Working StressConsequence 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 (a increase allowed)

(4.)ModuleStructural

(4.5 - 4.8)Lifting PointDesign



LIFTING


Strength

Figure A1 SUMMARY OF STAGES IN DESIGN/ANALYSIS OF SINGLE CRANE LIFT



LIFTING


(3.2)Module Design Weight (MDW)

(3.6)Static Hook Load (SHL) = (MDW x a(1) x 1.05(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

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

Check CraneCapacity

(3.9)DLL = [DHL -(RW x DAF)]

(5.)Rigging Design

(3.9)Lift Point Load = DLL x 1.05(1)

where: (1) is the factor to allow for yaw

(3.9)Lifting Point Forces

(4.2) Combined LRFD + Working StressConsequence Factors for:- Consequence Factor Consequence Factor

(a) Lifting points, spreader 1.50 1.0 bars(b) Primary Members 1.50 1.0(c) Secondary Members 1.15 1.0 (a increase allowed)



LIFTING


(4.3 -4.4)Module Structural Strength

(4.5 - 4.8)Lifting Point Design

Figure A2 SUMMARY OF STAGES IN DESIGN/ANALYSIS OF DUAL CRANE LIFT

Loc Guidelines for Marine Lifting

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