The HeavyLift Engineer Issue 04 Affinity

THE HEAVY L I F T ENG INE ER

WINTER 2020

...managing & delivering heavy lift projects

ISSUE: 04

FEATURE ARTICLES—CONSIDERING TRANSPORTATION

BEFORE IT’S TOO LATE—MOORING ANALYSIS

—DESIGN OF SHIP BUILD ANDTRANSPORTATION CRADLES FOR

FLOAT OFF LAUNCHES—TOWCON 2008 & TOWHIRE 2008

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A PUBLICATION

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THE HEAVYLIFT ENGINEER ISSUE 04

EDITORIAL page 5

DESIGN OF SHIP BUILD AND TRANSPORTATION CRADLES FOR FLOAT OFF LAUNCHES page 17

TOWCON 2008 AND TOWHIRE 2008 page 7

CONSIDERING TRANSPORTATION BEFORE IT’S TOO LATE page 13

CONTENTS

MOORING ANALYSIS. Page 25

Heavy Lift Tip - Single Point of Contact / Page 11

Heavy Lift Tip - Open Circuits and Pivot Points / page 21

Book Recommendations / page 16

Heavy Lift Tip - Lashing on Barges / page 23

Heavy Lift Tip - NDT Dim Control / page 29

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EDITORIAL

Welcome to our autumn edition of theHeavylift Engineer. This is our fourth editionand you can find past issues to download onour website as well as being able to sign upto be notified when new editions come out(www.heavyliftengineer.com/magazine).

The industry lost a well known and widelyrespected figure this year to illness and hehas written articles for this edition of theHeavylift Engineer. I knew Richie for myentire career and learned a lot from him.We thought long and hard as to whether ornot we should include them now but hewas driven by the sharing of knowledgeand good practice and so felt it was fittingto leave them in and dedicate this edition tohim as a friend first and colleague second.

It has been great to hear all of yourresponses and feedback to date and I lookforward to your views on our latest edition.

As the world in which we work hascontinued to change and adapt, and as wecome to grips with Covid, we all too aretrying to grapple with new workingpractices and what the wider sector willlook like going forward. None of us exactlyknow what this may be, but this time alsoprovides an opportunity to develop our skillsand arm ourselves for the challenges wemay face going forward.

This edition aims to share knowledge acrossa range of heavy lift areas, from anoverview of two commonly encounteredBIMCO charter parties, to mooring analysis.This is teamed with a piece outlining theconsiderations when designing bespoketransportation frames.

We have a selection of our helpful heavy lifttips, covering everything from lashings onbarges, to open circuits and pivot points –and of course our book reviews, to offersome helpful recommendations for yournext read.

Whether you are in shipbuilding, heavyfabrication, power generation or mining,the heavy lift engineer’s skill set is critical.No other engineering discipline, if youdecide to dive deep enough, offers such arange of technical challenges. We hope thatthis edition reflects that variety, offeringsomething of interest to you, regardless ofyour background.

Please do get in touch if you have a topicyou would like to see covered or would liketo guest feature for a future release – and Ihope you enjoy this new edition!

We would love to hear from you! Pleasesend any questions to:[email protected].

Please also sign up for future editions at:www.heavyliftengineer.com

JOHN MACSWEEN, MANAGING DIRECTOR AT MALIN GROUP

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TOWCON 2008 ANDTOWHIRE 2008

A towage contract can be for a variety ofactivities: arrival and departure of ships atports, offshore mobilisations and salvageoperations to name a few. There is also aplethora of towage contracts to be used bytug owners and hirers around the world. Forexample, in the United Kingdom you use theUK Standard Towage Conditions, revised in1986. These conditions were drafted by tugowners and, unsurprisingly, are heavilybiased towards them. Furthermore, they are30 years old which means they may not becompletely suitable for modern towageoperations. A more balanced and recentapproach can be found in the BIMCO standardform international ocean towageagreements. BIMCO stands for the Baltic andInternational Maritime Council and wasfounded in 1905. They are now the world’slargest international shipping association withthe aim to produce flexible commercialagreements that are fair to both parties.

There are two types of BIMCO ocean towageagreement. These are Towcon 2008 andTowhire 2008 with the main difference beingthat Towcon 2008 (TC08) is a lump sumcontract, while Towhire 2008 (TH08) is a dailyhire/time charter contract. These forms werefirst issued in 1985 with a revised editionissued in 2008 and another revision currentlyunderway. I will quickly explain the structureof the agreements and then discuss the majorclauses in the terms and conditions. Eventhough I will not discuss every clause, it isimportant to read every agreement in full andin detail. Where clauses are to be found inboth TC08 and TH08 the clause reference willrefer to Towcon 2008. From the outset Ishould make clear that my comments are onunamended BIMCO forms. It will often be thecase that the terms and conditions have beenamended. This will impact the apportioning ofrisk and liability so any amendments must beclosely scrutinised.

For people familiar with BIMCO agreements,TC08 and TH08 are both set out as per thestandard BIMCO form with a Part I, Part II andAnnex A. For people unfamiliar with BIMCO,this template has a clear structure and is easyto understand. Part 1 consists of boxes thatare to be populated with the job specificinformation (40 boxes in TC08 and 43 boxesin TH08), Part II is the terms and conditions(35 clauses in TC08 and 33 clauses in TH08)and Annex A contains the tug specification. Itis important to complete Annex A properlyand not to just include a tug specificationsheet. The forms allow additional clauses tobe included in the contract. Part I and anyadditional clauses will prevail over Part II andAnnex A in the event of a conflict of termsand conditions.

The first clause to look at in Part II is clause 3which is ‘price and conditions of payment’.Even though the payment mechanisms inPart I of TC08 and TH08 are different, thesame condition applies to both – that all sumspayable shall “be fully and irrevocably earnedat the moment it is due”. That is to say thatany lump sums or daily hire due shall be paidregardless of whether the tow or part of thetow is lost. In TC08 the risk to the hirer can bereduced in Box 33. The lump sum towageprice can be split into instalments with thefinal instalment “due and payable on arrivalof tug and tow at place of destination.”Aprudent hirer will aim to have much of thelump sum price in that instalment.Consequently, if the tug and tow does notarrive at the place of destination thatinstalment is not due. In TH08, as a timecharter contract, there is no instalmentscheme available to back load.

The agreements recognise the potential riskof a tug not being ready to commence thetowage and require a cancelling date in Box38. This is the date that the hirer shall havethe option of cancelling the agreement if thetug is not ready to commence the towage.Clause 5 deals with the cancelling date andhow it can be extended, providinginstructions for both the tug owner and hirer.If the tug owner anticipates that the tug willnot be ready, he shall notify the hirer statingthe expected date of readiness and enquireif the hirer wishes to cancel the agreement.This option is only available to the hirer for48 hours after receipt of the tug owner’snotice. If the option to cancel is notexercised, then the date in the tug owner’snotice shall be the new agreed date tocommence towage operations. Regardlessof whether the hirer cancels the agreementhe is “entitled to claim damages fordetention if due to the wilful default of thetug owner”. This could be the additionalcosts at the place of departure incurred as aresult of the tug’s delay.

There are often additional charges and extracosts when performing a tow. This issue isdealt with in clause 9, ‘additional chargesand extra costs’. To put it simply alladditional charges and extra costs are to beborne by the hirer. These charges and costsconsist of agency, port expenses, taxes,assisting tugs, costs necessary forpreparation of the tow and insurance of thetow. These costs must be taken intoconsideration by the hirer when enteringinto a towage agreement.

Clause 18 imposes undertakings on the hirerwith regard to the condition of the tow or‘tow-worthiness’. The hirer must exercise

due diligence to ensure that the tow is fit tobe towed. This means that the hirer mustensure that the tow is “suitably trimmed,prepared and ready to be towed at the timewhen the tug arrives and is fitted andequipped with such shapes, signals,navigational other lights of a type requiredfor the towage.” This will usually bedemonstrated with a certificate of tow-worthiness issued by a Marine Surveyor.However, there is no obligation to performthe tow until, at the tug owner’s discretion,the tow is fit and ready for towage. It isimportant to note that an inspection of thetow by the tug owner will not constituteapproval of the tow’s condition or a waiverof the hirer’s above undertakings.

A much shorter clause 19 governs sea-worthiness of the tug. The tug owner “willexercise due diligence to tender the tug atthe place of departure in a seaworthycondition and in all respects ready toperform the towage.” What does this duediligence entail? The tug owner must carryout any inspection, repairs etc, which, in thecircumstances a skilled and prudentshipowner would carry out. Any work carriedout must be done with reasonable skill, careand competence. This exercise of duediligence is not delegable. It would not besufficient for the tug owner to point to theappointment of properly qualified people toperform the work. Tug owner will be liablefor defects reasonably discoverable whentug comes into their ownership, possessionor control. However, if bad work is concealedand can not be detected by reasonable carethen the tug owner will not be liable.

fig. 01 / Stern tug with towline over the bow

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Clause 22 allows the hirer to terminate thecontract. In every instance of termination, atermination fee will have to be paid as set outin Part I, assuming no fault on the part of the tugowner. If the tug is already en route to / arrivedat the place of departure or even if towageoperation is underway then hirer shall pay thetug owner all sums payable under thisagreement. This is in addition to any damagesthe tug owner may be entitled to claim forbreach of the agreement.

Clause 23 gives the tug owner the right towithdraw and leave the tow. This right is limitedto five situations, namely:• delay at place of departure;• delay at place of refuge;• financial security not provided;• hirer not accepted tow at place ofdestination and;• unpaid sums due.

Delay (or delays) must exceed 14 days beforethe tug owner has the option to terminate. Theother three termination grounds require 7 daysto pass before termination can be invoked. Thetug owner must give 48 hours notice of hisintention to withdraw. Failing to do so mayresult in a repudiatory breach of the contract.

Clause 25 governs ‘liability and indemnity’. The2008 revisions introduced a knock for knockregime into both Towcon and Towhire. Theunderpinning principle of knock for knock issimply, ‘your personnel + your property = yourproblem and my personnel + my property = myproblem’. The result is no responsibility for eachothers personnel and property and protectionfrom third party claims caused by the otherparties’ property. The indemnities applyhowever the claim may arise or the damage iscaused. As the clause is written there is noexception due to the gross negligence or wilfulmisconduct of the hirer or tug owner. The knockfor knock regime applies for the period of time“from arrival of tug at place of departure untildisconnection at place of destination”.

In TC08 and TH08 the indemnities and liabilitiesare split out which makes them easier tounderstand. Part (a) deals with personal injuryor death with (i) setting out the tug owner’sindemnities and (ii) setting out the hirer’sindemnities. Part (b) deals with loss or damageto property with the tug owner’s and hirer’sindemnities split into (i) and (ii). Part (c)concerns loss of profit, loss of use or loss ofproduction and consequential loss or damage.This part of the clause includes five exceptionsto the strict knock for knock regime. These arepermits and certification, the tow-worthiness ofthe tow, the seaworthiness of the tug,termination by the hirer and termination by thetug owner. So, in these instances, parties will be

liable for loss of profit, use or production andany consequential loss or damage.

TC08 and TH08 both contain another exceptionto the knock for knock regime and it can befound in clause 16 which is ‘towing gear and useof tow’s gear’. The tug owner must provide alltow wires, bridles and towing gear carried onboard the tug for the purpose of the towage freeof cost to the hirer. Furthermore, the tug ownercan make reasonable use at his discretion of thetow’s gear, power anchors, anchor cables, radio,communication and navigational equipmentfree of cost during and for the purposes of thetow. This is set out in parts (a) and (b) but mostimportant is part (c). It states that “the hirershall pay for the replacement of any towinggear and accessories should such equipmentbecome lost, damaged or unserviceable duringthe service(s), other than as a result of the tugowner’s negligence.” Now that replacementcost could be very large as towing gear isexpensive. This is a significant exception to theknock for knock regime that the hirer must beaware of.

Clause 28 allows a possessory lien over the tow.This lien can be exercised in relation to any andall sums due to the tug owner under thisagreement, and not just the lump sum or dailyhire. The lien can be exercised by the tug owner“himself or his servants or agents or otherwise.”This is necessary as the tug owner does notalways receive payment, so it allows the partywho does receive payment to exercise the lien.The clause allows the tug owner to recover “allreasonable costs and expenses and all costs ofrecovering the same, including legal fees…inexercising or attempting or preparing toexercise such lien”. Finally, the tug owner shallbe entitled to receive the tug’s delay paymentunder TC08 or the daily rate of hire under TH08for any reasonable delay to the tug resultingfrom the lien. So, having a lien exercised on atow can be an expensive matter. The hirer willhave to pay all sums due under the agreementwith interest and all costs associated with thelien and delay payments.

Clause 6 in TC08 deals with free time and delaypayments. A similar clause is not required inTH08 as it is a time charter and the daily hire willapply. The purpose behind this clause is to allowfor a defined period of free time for clearlyidentified events where the tug will not besubject to delay payments. Boxes 26 and 27 willstate the defined periods of free time and clause6 states the identifiable events when free timeapplies and when free time starts. The eventsare connecting and disconnecting the tow,transiting canals and restricted waters and allother purposes related thereto. Free time atplace of departure shall commence when theTug arrives at the pilot station until dropping last

Written by Nick Banks, Contracts Engineer, MalinAbram

outbound pilot when leaving for the open sea.Free time at place of destination shall commencewhen the tug and tow arrive at the pilot station oranchors or arrives at the usual waiting place oranchorage until dropping last outbound pilotwhen leaving for the open sea. Should free timebe exceeded then delay payments at the ratespecified in Box 30 of Part I shall be payable.These delay payments will apply until tug and towsail from the place of departure or the tug is freeto leave the place of destination.

These are, in summary, the main considerations inTowcon 2008 and Towhire 2008. I will repeat thatthe comments are on unamended BIMCO formsand to again warn that any amendmentsintroduced by the other party will require closescrutiny. Thankfully on BIMCO forms additions arehighlighted in red and deletions are highlighted inblue which makes amended agreements easier todigest.

Changes to the clauses that have been discussedrequire extra close scrutiny as the risks andliabilities of the parties may have shifted. If aparty is including their own changes to the forms,then these should be clear in wording andpurpose. Otherwise that will bring uncertainty intothe agreement which the BIMCO forms try toavoid.

fig. 02 / Tug moving into position

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HEAVY LIFT TIPSINGLE POINT OF CONTACT

One issue that is becoming harder to managewith today’s digital communications is thesingle point of contact.

For most contracts between a client and asubcontractor there is a named relationshipwithin the contract. What happens during thecontract execution is this relationship getsblurred.

How?

Human nature….

With modern communications everything canbe sent to everyone, with everyone cc’d in onan email, whether relevant to thecommunication or not. Some people areannoyed by this… this leads people to limittheir correspondence to directcommunication, thinking they are sparingothers what annoys them. This is fine withinan organisation, but as soon as that happensexternally, then control over the messagestarts to slip. Things that are urgent, lose theirurgency when people don’t understand theiroverall role in a project and what is critical ornot. Similarly, they fail to react to a request,when bombarded with emails from everyoneabout everything.

Why should we insist on a single point?

The single point of contact is probably theonly individual who understands how all thestrands of a project tie together. If you are aclient, ideally, you want to speak to theperson who knows what is going on, whounderstands the issues and don’t want to bebombarded with every Tom, Dick or Harriet

asking some minor question…which hasprobably been answered already. If you are asubcontractor, you need to ensure that yourcommunications are on message and don’tgive conflicting or confusing information tothe client.

By all means, communicate person to person(both internally and externally), but keep thepoint of contacts in the loop!

When it gets to site.

On site there are too many things happeningto allow a loss of control. The ability tochannel everything through a single point ofcontact facilitates focus and direction. It limitsrisk, as people might be told by others, to dosomething which conflicts with the overallplan. If they act on that request, they could beexposing themselves, their colleagues andthe project or business to risk.

Written by Richie Mason, Principal ProjectEngineer

SINGLE POINT OF CONTACT

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CONSIDERINGTRANSPORTATIONBEFORE IT’S TOO

LATE

fig. 03 / Large subsea towheadnavigating narrow streets

Fabrication facilities, producing largestructures or items of equipment, are almostalways positioned close to a river or coastlinewhere there is a suitable quayside for loadingto a ship or barge. The reason for this, ofcourse, is that transporting any large item aconsiderable distance usually requires someelement of sea transportation and the closera facility is to the open sea and facilities forloading and discharging equipment, the morecompetitive and effective it can be. It istherefore surprising that in many cases theconsideration of transportation is of primeimportance when selecting a build site andthen typically left as a secondaryconsideration during design and manufacture.

It’s then not until close to the completion ofthe equipment that transportationconsiderations return to the fore. Whilebudget tendering for the relocation of thefinal item will likely have been done duringany bid stage, it is often not until during build,and often close to the end, that a heavy liftpartner is selected to do the final move. Atthis point, engineering will be undertakenand, unfortunately, by this point in the projectlife cycle options become limited leavingsolutions that are costly and complicated toimplement. For this reason, I would alwaysadvocate looking at how you are going tosupport, move, lift, turn and ship an item atthe earliest stage possible to maximise thebenefits and time to develop an optimalsolution.

Considering transportation at the early designstages offer greater opportunities to ensurethe equipment can be shipped with minimaldifficulty. Some key areas that should beconsidered are:

• •Design of a bespoke transportation frame• •The shipping route and associatedconstraints• Factoring transportation into the equipmentdesign• Heavy lift equipment selection to ensuremaximum competitiveness when tenderingfor your final contractor

A bespoke transportation frame, tailored tosuit the size, shape and characteristics of theequipment can result in a much simplertransport and leave a solution open to awider variety of land and sea basedequipment, maximising the supply chain youcan approach for prices. Ideally, this framewould be considered at an early stage of theequipment’s fabrication allowing sufficienttime for design and manufacture. The framecan incorporate features to aid in seafastening, provide suitable load spreadingand accommodate the preferred load-outmethod for the equipment.

Some large times of equipment do not lendthemselves to a transport frame as the itemalready has a large flat base offering ampleload spreading and large lever-arm forstability other considerations such as localpoint load capacity and bearing points forconcentrated loads must still be consideredand modification to suit lifting and movingare best done at the design stage.

The main advantage of a bespoketransportation frame is the very fact that it isbespoke. This allows the frame to bedesigned to meet the specific needs of theequipment such as spanning and supportingit at any inherent strong points the structuremay already have as well as avoiding anyweak points with little inherent structuralstrength, and then allowing a variety ofoptions for static and dynamic load transferfrom heavy lift equipment through the frameand into the native primary structure behind.It also allows for the incorporation of externalsecuring points on the equipment and allowsfor integration into any existing temporaryinterfaces such as bolted connections orlifting points.

Another key consideration when transportingany large and/or heavy item of equipmentby sea is the transfer of the item from theshore to the vessel or barge. When loading tomost conventional ships the item will belifted by shore or vessel crane. For theseoperations, it is normal to simply incorporatethe lifting eyes into the equipment itselfhowever even when this is possible, it isworth considering how lifting aids or framemight make the lift safer, easier or reducingany internal stiffening needed for just thelifting case. This can be as simple as a framethat ensures any lifting lugs are loaded in oneplane only to reduce the secondary stiffeningbehind a lifting point or it can be much moreinvolved such as the creation of a frame thatis used for supporting the equipment from itsbase while the crane lifts from dedicatedpoints around the perimeter of the frame.This protects the integrity of the cargo assupport forces are applied at the strongestlocations and lifting locations can bepositioned to allow for an even lift and it candouble as load spreading under theequipment and serve as a flexible interfacebetween the equipment and a wide range oftransportation vessels. If the equipment isbeing transported on a barge or vessel withRORO (Roll-on/Roll-off) capabilities, then askidding or SPMT arrangement may beutilised. Where the equipment does not havea framed base or suitable points for trailer/skidding support then, again, a transportationframe will be required. The frame will act asan interface between the equipment andloading method, offering suitable support

points for the transport equipment and anydeck grillage and sea fastening after beingloaded out to the vessel.

It is often the case that large, out of gaugeitems of equipment have small footprintsand/or high centre of gravity compared withtheir height. This can cause large vertical,dynamic loads into the deck and in somecases when the lever-arm of stability is small,tipping can occur at maximum roll angles. Inboth instances this can cause issues with deckstrength limiting the number of suitablevessels for transporting the equipment. Whena suitable transportation frame is introducedthe frame can be designed to spread theloads over a greater area, increasing thenumber of available vessels and open upgreater options for transportation.

Further to this, the frame can be designed towork in conjunction with other availableequipment such as existing grillages whichmay also be used for the transportation. Afurther consideration when transporting anyitem by sea is how the item will be secured.This can often cause problems when notconsidered during the item’s design stages asthere may not be suitable securing points onthe piece (padeyes, lifting lugs). Further tothis it is usually not possible to add these orweld to the item and this results in acomplicated securing arrangement. Atransportation frame allows for a securingmethod to be designed as part of thestructure and allows for the equipment to besecured to the frame (either on shore or onthe vessel) before the latter is then securedto the vessel deck. This offers good flexibilitywith the available securing methods whichwould not normally be available. The framecan also be designed to accommodate themost appropriate securing method for theequipment such as welded seafastening orlashings and does not limit the method towhat is available at the time oftransportation.

Even when a frame is employed it is oftendesigned with only one item of equipment inmind and might not consider a wider projectview. If a fabrication facility was regularlyproducing the same piece of equipment thenreuse possibilities are obvious, howeverwhen a number of, at first glance, widelydifferent items are being built as part of awider programme, consideration for a slightly

more complicated frame that can then beused multiple times is worth considering.Cargoes, that at first glance, appear verydifferent may actually be hiding similarpatterns of support points and primarystructure. A level of flexibility may bedesigned into the frame so that it canaccommodate variances in the equipmentthat are to be transported reducing overallproject cost.

By doing this the cost of fabricating atransportation frame for every item isremoved but consideration must be made ofthe costs for relocating the frame betweenmoves. By enabling it to be roadtransportable, or dismantled (possibly by wayof bolted connections) this could allow for amuch reduced cost of transportation.

Essentially, designing and fabricating atransportation frame for any large and/orheavy item of equipment should always beconsidered and ideally at the early designstages. This could provide huge benefits inboth cost and time both in late modificationsto a structure near the end of build, afterpainting and outfit and in the selection ofheavy lift equipment and partners to bid forthe transport.

Written by James Bowie, Team Leader, MalinAbram

BOOK RECOMMENDATIONS...START WITH WHY BY SIMON SINEK

THE OILMEN: THE NORTH SEA TIGERS BY BILL MACKIE

Whilst a lengthy and sometimes repetitivepiece, with many references to Apple, thisbook by Sinek, based on his TED talk putsforward a rather simply but nonethelesscompelling argument; to be successful,knowing what you do and how you do it isnot enough.

To succeed, inspire, thrive, you also need tounderstand why. The simple answer may beto make money, but it is the reasoningbeyond this, and an understanding of it thatwill enable you to progress in your operation.Its an appreciation of the importance ofpassion, drive and vision and an unwaveringcommitment to achieve your goal.Rather than a comprehensive guide, this

book provides a reference point, that may bereused and reread - almost a reminder tochallenge assumptions in your everydayways of working.

The exploration of Oil in the UK’s North Seahas been a mix of engineering triumph,technical ingenuity, political machinationsand sombre loss of life. Bill’s book capturesthis through stories, photographs, anecdotesfrom those who were offshore from the1960s through to the late 1990 and early2000s. These stories show, in many cases,how far we have come and the dreadfullyexpensive, in terms of lives lost, road to gethere.

It starts with several chapter covering thedawning of a new oil age in the North Seabefore moving through the Americanisationof UK oil and gas exploration and the effectthe piper alpha incident had on the industry.

For anyone working in ht oil and gas sectoras well as other, newer offshore sectors suchas renewables, this book gives a good tasteof where we started and how far we havecome.

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Design of Ship Build and TransportCradles for Float Off Launches

Transportation cradles are a key componentin the build, transportation and launch of aship and a suitable design can befundamental in the success of theseoperations. Throughout their use they willsupport the various blocks and completedship during construction, act as the interfacebetween the vessel and SPMT’s (SelfPropelled Modular Transporters) or barge,and ultimately support the ship during floatoff operations. The cradles are possibly theonly item of equipment that will see theship from very early stages of constructionthrough until she is floating in the water. Itis apparent that the correct transport cradledesign is of the utmost importance.

At the early stages it is important to outlinethe design parameters and drivers.Generally, the main considerations will besteel weight and cost (which areinterlinked). Keeping these as low aspractically possible will of course depend onthe engineering budget available. This thenbecomes a trade-off between the two andhaving a target steel weight or not toexceed (NTE) weight from the outset can bebeneficial and prevent the burning ofexcess engineering hours.

It is not unreasonable to assume that thedesign of the transportation cradles will becarried out before the shipbuilding processbegins. This poses its own problems in thatan accurate ship weight and longitudinalweight distribution will be required as abasis to design the cradles against. Ideally,the ship will have been modelled instructural or draughting software, withweights and stiffnesses defined, allowingfor an accurate weight estimate at each ofthe cradle locations. In most instances thiswill not be the case and approximationdistribution methods would have to beemployed. This inherently introduces some

uncertainty into the weights andappropriate factors of safety should beapplied. Further to this, it is important toconsider that the weight of the ship mayincrease due to operational or designchanges and it is always recommended tofactor this into the initial ship weight.Overcompensating will never cause issueswhereas under compensating almostalways will.

Once the weight and distribution of the shiphas been adequately defined a transportarrangement can be identified which willgenerally involve the use of SPMT’s. TheSPMT arrangement is a key factor in thedesign of transportation cradles and shouldbe established prior to the commencementof engineering. Seeking the input of anexperienced transport engineer to producea preliminary trailer configuration isbeneficial and gives assurance that thecradles are being designed and checked toa working arrangement. There may be arequirement with larger ships that they arebuilt in several blocks in the build hallsbefore being moved to a hardstand withgreater space to be combined. Individualblock moves and their respective trailerarrangements should be considered asbefore as loads into the transportationcradles here will differ from that of the fullship transportation. When SPMTconfigurations have been identified it isthen possible to determine the locations ofthe support stools in the build hall and onthe hard stand, and the location of thegrillages on the barge (or occasionally, theship).

Appropriate load cases will be devised toreflect the various stages of the build andtransportation process. Generally, these willinclude a static case with the completedship and individual ship blocks positioned

atop the build stools, a case representing shipand block weighing, a case during SPMTtransportation for both completed ship andindividual ship blocks, and a case during bargetransit to the float off location. Environmentalconditions such as wind should also beconsidered where appropriate.

The static case when the vessel is on the buildstools and during weighing operations tend toonly account for the weight of the vessel astaken from the load distribution. The differencebetween the two is of course the supportlocations will differ, depending on the locationof the build stools and load cells underneaththe cradles. Consideration should be given as tohow the load will spread between the loadcells and suitable factors of safety should beapplied here to account for any variancebetween cell groups.

It can be difficult to predict exactly how theload will be applied through the transportcradles during SPMT transportation withoutproducing a detailed model of thearrangement. It is common for SPMT’s to bendupwards at the tips and this can cause anincrease in the loadings to the cradles at theforward and aft extents. Further to this, wherethere are several cradles grouped closelytogether there may not be an even spreadbetween the transport beams and this againshould be investigated. Careful thought mustgo into the methodology for this load case and

proper analysis will help to avoid applyingoverly large safety factors where uncertaintiesare present.

The final, and generally most onerous load casetends to be the barge transit condition. Thisload case must consider additional motions dueto transportation by river or sea. The magnitudeof these motions will be determined by thenature of the transit. For example, the transportcradles must be capable of withstandinggreater forces if the transit is through non-benign waters compared with inland andsheltered waterways. These differences mustbe taken seriously as more challengingtransportations can require a much toughertransport cradle arrangement. Further to this,analysis must be carried out to consider themost severe increase in inclination of the bargedue to single or sometimes doublecompartment damage. Default motion criteriafor considering the transit load case is readilyavailable in current guidelines.

A further area for consideration that is oftenoverlooked for transit is the potential hoggingor sagging of the barge. It is almost impossibleto eliminate the barge curving when it isloaded with heavy items and therefore theeffects of this bending should be consideredduring the transportation cradle design. Ideally,the hogging or sagging will be minimal and canbe eliminated by observation, however, whenthis is not the case the additional force due to

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fig. 04 / Vessel in cradle pre launch

bending should be carefully considered toensure the cradles are not over stressed.

Once the groundwork has been carried outa preliminary cradle layout can be createdusing the knowledge of the requiredtransportations and considering theirassociated load cases. There are manyareas to consider when creating thearrangement and some of the main pointsare detailed as follows:

• Suitable transport beam width to spansupport locations in all conditions (buildstool, SPMT, and barge grillageextremes)

• Locate suitable strong points on theship where supports can be positioned,this tends to be in way of bulkheadsand frames. Checks should be carriedout to ensure hull structure can takeloads from supports.

• Determine suitable sizes for cradlebeams and sections. High level checkscan be carried out initially to give agood steer on the required sizes. Thesecan be refined as more detailedanalysis is carried out.

• Consideration should be given toaccommodating the weighingarrangement in the design. Addingcross members between transportbeams may allow for better weighingpositions and reduce the number ofload cells required.

• Practicality and feasibility of the design.

Having created a preliminary arrangementthis can then be further developed byanalysing the design against the previouslydefined load cases. Detail of the cradlearrangement can be adjusted as requiredand an iterative design process may takeplace to further refine the layout. Oncecomplete, the output will be a technicallyand operationally compliant proposal.

When the cradle design is complete andmeets the requirements of the shiptransportation it is reasonable to assumethat the next step would be to produce thefabrication drawings. However, there maybe benefits to be had of involving a third-party at this point to review the design andcomment on areas for improvement orconcern. This gives added assurance thatthe design is capable and fit for purpose.Additionally, where transportation cradledesign is a relatively new undertaking, itmay be useful for a third-party expert tohave input during the complete designprocess to offer guidance and a steer from

the outset. This may prevent wastedresearch and engineering time and result ina better solution at the end. Finally, thedetailed drawings of the transportationcradles can be produced and sent forfabrication with the knowledge that thecradles will be suitable for purpose.

In essence, there are many factors toconsider when developing a transportationcradle arrangement and a good layout canbe key to the success of any ship build andlaunch project.

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fig. 05 / Hull support cradles

Written by James Bowie, Team Leader,Malin Abram

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fig. 06 /SPMT, Image by IMessmer

HEAVY LIFT TIPOPEN CIRCUITS AND

PIVOT POINTS

One of the basic issues/pitfalls involving selfpropelled modular transporters (SPMT) isunintended rotation around pivot points.

This usually occurs when there is a narrowsupport point above a tower of packing. Whencombined with an open hydraulic circuit thiscan creates a potential incident.

What is an open circuit?

An open hydraulic circuit is the term used todescribe the free flow of oil between hydraulicsuspension rams. This occurs when the ramson each side of a 2-file trailer are linkedtogether in one circuit, as occurs in the pointcircuit of a 3-point system. Ordinarily this willnot be an issue as there is tipping or twistingresistance provided by the side circuits and thechassis strength.

But when there are no side circuits, such as inan overall 4-point setup, or multi trailerarrangement, where single trailers are pipedinto a much larger hydraulic group, but are notphysically connected to each other, then thereexists the potential for a trailer to “roll” aroundits pivot point.

This roll can be prevented in the short term byensuring the ram tops are covered byadditional supports as a minimum.

This “roll” can also occur in the longitudinaldirection, when a trailer is on a single supportin the centre. Any minor imbalance in hydraulicpressure centre, transporter cog (perhapscaused by the PPU) and the position of the loadpoint on the transporter can quickly developinto a transporter rotating underneath a piece.

Written by Richard Mason, Principle ProjectEngineer

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OPEN CIRCUITS ANDPIVOT POINTS

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Written by Lindsay McDougall, TechnicalDirector, Malin Group

“CHECK ME! I’M ‘TENSE’!”

Barges are a fundamental part of today’smarine transport solutions and we areoccasionally asked why welded sea-fastenings are preferred for securing cargoon barges. Lashing of cargo using chains,wire or webbing straps is common practiceespecially on ships, so why not use them onbarges?

The key difference between ships andtransport barges is the fact that ships aremanned whereas barges are typicallyunmanned. As good seamanship dictates aship’s crew examine the lashingsperiodically it becomes clear why lashingsmay not be preferred for an unmannedbarge. The lashings would typically beinspected daily or directly after a period ofheavy weather. The inspections allow thecrew to check that the lashings havemaintained their tension, that the tension isconstant throughout the lashing spread andthere are no issues in general with thelashings.

To do this on an unmanned barge in opensea is neither safe or practical. Thereforeuse of lashings on a barge introduces a riskas they are effectively not inspectable andtherefore potential issues cannot beidentified or rectified.

Lashings under tension can loosen for anumber of reasons, including naturalstretch, vibrations and slamming loadsespecially if they are not fitted with lockingmechanisms. Slack lashings can lead touneven loading into the ones that are stilltensioned, leading to progressive failure. Ifthe cargo is not sufficiently secured it canlead to damage, or even total loss of thecargo.

Lashing on barges can be safe but normallythis would be predicated on a number offactors including passage time, weatherrestrictions, the type / arrangement oflashing and the cargo itself. For example ashort coastal tow, with weather restrictions,may be suited to lashing solutions. But keywould still be the ability to lock the lashings,and ensuring the spread of load in thelashings is constant.

To eliminate the chance of cargo beingcompromised whilst at sea, speak with aspecialist who can determine the forces thecargo will be subjected to on a barge andwho understands the safest sea-fasteningmethod for a successful barge transport.

fig. 07 / Longitudinal lashing arrangement

HEAVY LIFT TIPLASHING ON BARGES

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THE HEAVYLIFT ENGINEER

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MOORING ANALYSIS

Mooring analysis is the process of ensuring avessel, or any floating body, remains in position,under applied environmental conditions, safely andsecurely. Mooring lines are connected to an anchorsystem which can either be a series ofinstalled/laid anchors, or the lines can beconnected to bollards which can be foundpositioned along quaysides and harbour berths.There a number of different types of offshoremoorings leg types such as catenary, taut leg,tension leg and single point articulated moorings(SPMs). For most heavy lift operations, inshore,moorings will be either to shore side bollards orrelaid anchors on the sea/river bed.

Offshore moorings

The most common offshore mooring spread is acatenary spread, where the body is moored usingline and anchor systems – usually drag embedmentanchors. These are put in position by lowering tothe seabed, and then having a horizontal tensionapplied tot he line with “drags” the anchor alongthe sea bed. As this happens the anchor flukescause the anchor to embed itself into the sea bedand as it does so, the resining focus increase to thepoint that the vessel can no Lanier move it. At thispoint the anchor is said to have “set”.

. Catenary spreads rely on the line length beinggreater than the water depth, this “groundedlength” ensures that the anchor does notexperience any uplift (vertical forces) and is subjectto only horizontal loading. The long line lengthsprovide substantial added weight to the system,contributing to restoring forces required tocounteract the response of the vessel due toenvironmental conditions and can also add to theholding capacity of an anchor system due to thefriction between the bottom chain and the seabed.

The mooring analysis for such a spread will statevessel offset limits, which the spread must notallow the body to exceed. These offset limits areusually specified in terms of maximum surge, swayand yaw parameters defining the maximumamount the vessel can move during maximumstorm conditions in either its longitudinal,transverse and rotation (about its vertical axis)directions.Although the catenary lines appear slack,the sheer weight of them will ensure the body

remains within the desired offset envelope basedon set limits. They do this by applying a restoringforce on a vessel which increases the further avessel moves from its original position. An exampleof this being of semi-submersible drill rigs;connected to the wellhead via a “riser” – increasedvessel offsets will induce excessive bending andtensile stresses in the riser, which risks damagingthe infrastructure.

Although catenary spreads are widely used, theyare limited in their application, due to water depthrestrictions. There are accepted industry limits as tohow deep a catenary can be installed. Thesesystems become impractical to install in deeperwaters; however, the main issue is that the weightof the lines becomes too significant, with thebuoyancy capacity of the vessel unable tocounteract this. For this reason, many moderndeepwater catenary systems employ elements ofsynthetic moorings which are either neutrally orslightly buoyant.

Taut leg

Taut leg mooring is a solution employed in deep toultra-deep-water locations and, unlike catenaryspreads, relies on vertically laid anchors – e.g.suction piles. The lines in a taut leg spread do notcontact the seabed and are usually made ofpolymer or fibre lines so as to reduce line weight.The lines will be set in such a way that the spreadcreates an angle between the line and seabed, thisproduces a vertical and horizontal component atthe anchor.

Tension leg

Tension leg moorings are very similar to taut legmoorings in that the lines do not come in contactwith the seabed and they are employed in deepwater locations. In these systems, the loadcomponent at the anchor is entirely vertical. This isachieved by laying the spread to produce 90degree angles between the waterline and seabed– also eliminating almost all vertical movement atthe platform. Although the platform is fixed againstvertical displacement, wave motion can still affectthe displacement in the horizontal plane.

Single point mooring (SPM)

Single point mooring is when a floatingbuoy or jetty is moored offshore and isprimarily used by tankers to unloadpetroleum or other products to save thevessel going into port, or if the port doesnot have the unloading infrastructurerequired for such an operation. SPM is asimple system and is named as such due tothe requirement for only one point ofcontact between the vessel and the buoy/jetty

There are a number of key considerationswhich must be made,for the requiredanalysis, such as;• Where is the vessel to be moored?• Sea states such as wave conditions, tidalbehaviour, current velocity, water depth• Expected wind conditions – velocity anddirection• Vessel particulars and motion data

Another consideration is how long thevessel is expected to remain on location,determining to which limits the analysis isrun and could dictate the number/type ofmoorings required. Typically, wintermoorings will be more substantial thanthose used in the summer months.

Industry standards and codes must beconsidered. These will outline theoperational and environmental limits,desired safety factors and any preparatoryinstructions as to how the analysis must berun. It is at the engineer’s discretionwhether or not the analysis passes, adecision can be made to work within thelimits of the codes, or allow for tolerances.Institutions such as DNV and API bothoutline such features, however, limits andfactors of safety differ from code to code,therefore, a client will usually specify towhich code the analysis should be run.

Inshore moorings:

Lay-By moorings follow the same principlesand methodology as those for offshoremoorings, however, inshore mooringspredominately rely on bollards instead ofphysical “anchors” to provide the holdingcapacity. The bollards are in fixed locationson the quayside; therefore, the flexibility ofthese systems is more limited. Figure 8

shows a standard spread, where lines 1 and8 (outboard lines) are angled close toperpendicular to the quayside to restricttransverse/sway motion, away from thequay. Lines 2-7 (spring lines) are angledparallel to the quayside, restrictinglongitudinal/surge motion forward and aftalong the quayside.

By having these angles as such we canensure that we utilise as much of thetensile properties of the mooring lines aspossible.

There are a range of mooring analysisoptions and the two most common inheavy lift projects are Quasi-static andDynamic.

Quasi-Static

In Quasi-Static analysis, averages are takenfor the environmental forces and vesseloffsets, and low and wave frequencyresponses in the horizontal plane arecombined, giving the maximuminstantaneous offset. The wave frequencyresponse is established when the effects ofthe mooring system are significant –mooring line tensions are then calculatedstatically for the determined maximumoffset location. However, Quasi-Staticanalysis will begin to underestimate linetensions as water depth increases – as such,codes of practice will counteract this byimplementing higher factors of safety. Indeep water applications Quasi-Static is notconsidered a conservative approach.

Dynamic

Dynamic analysis takes into account linedynamics caused by inertia forces onmooring lines due to vessel motions andhydrodynamic effects on the lines. Dynamicanalysis is generally accepted to be moreaccurate in comparison to Quasi-Static.

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Written by Calum Reid, Graduate NavalArchitect , Malin Abram

fig. 08 / Complex Orcaflex mooring analysis

As the engineer, it is our responsibility toensure that the mooring spread isoptimised while operating within theboundaries set out. We must considervariables such as different line types,materials and attachments, anchorlocations, subsea assets etc. In doing sowe can ensure that the spread is not onlycost effective but as suitable for purpose aspractically possible. This process has beenmade far easier with the use of computerprograms which allow the user to simulateand analyse various mooring spreads andenvironmental data accurately and quickly.

One of the most popular programs isOrcaflex by Orcina. Orcaflex allows the userto input all of the above parameters andallows basic structures to be modelled tosimulate the real life scenario – Orcaflexutilises a Finite Element (FEA) method ofanalysis and can account for line elementswith and without bending stiffness., andwill allow static or dynamic analysis, togenerate results and motion simulatedoutputs.The FE method in mooring analysisdivides a loaded model or body into

discrete (or finite) elements in much thesame way as it would for a structuralmodel. This network of elements are thenassembled into a series of equations thatare solved simultaneously to determine theoverall deflection and tensions or beddingsstresses for lines that can accommodatethem. These results are then reported astensions and stresses along the length ofthe mooring line as well as restrainingforces and vessel movements in a reportformat. It also then allows the user toremove selected lines and rerun theanalysis to model various damagescenarios.

By combining all of the mentionedenvironmental factors, load cases andindustry standards, we can provideaccurate, optimised and thoroughlyanalysed mooring arrangements to ensurethat vessels, whether they be inshore oroffshore, are steadfast and safe.

fig. 09 / Pipelay vessel moored to bespoke mooring buoys

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WHY YOU SHOULD MEASUREYOUR OWN WELDS

Whether you secure an item of cargoaboard a vessel using lashings or stoppersand cleats, an amount of welding is usuallyrequired. This, in turn, means fundamentalchecks of the welding must be carried outto confirm it is suitable and up to the job.

While the quality of the weld may seemadequate to the naked eye, further weldevaluation tests are important to identifyany internal defects and surface cracks.Non-Destructive Testing (NDT) is anappropriate examination technique whichdetermines the quality of the weld byreviewing the surface and sub-surface ofthe weld, as well as the surrounding basematerial, without destroying the weldedcomponent.

Within the industry, a number of weldingcodes and guidelines exist which specifythe necessary level of NDT, along with thecorresponding acceptance criteria. Theseguidelines will often include a requirementfor 100% visual inspection, in addition toevaluating the welds using MagneticParticle, Radiographic and Ultrasonic testmethods.

In saying this, there is no point insubmitting an obviously bad weld foradvanced inspection techniques. Visualinspections are perhaps the mostunderrated method of weld checking,despite being the easiest and leastexpensive to perform.

Many will assume that once a qualifiedWeld Inspector has signed off on a weld, nofurther checks are required. However, this isnot always the case. Welds can pass theNDT checks but still be unacceptable, so thevisual inspection is a step that should not bemissed out. If the weld is visually checkedand found to be wanting, then there is nopoint in moving to the NDT until the weldhas been dressed and repaired. Without a

visual inspection, time can be wasted ontesting already unacceptable welds.

Unless explicitly confirmed, it should neverbe assumed that checks on the weld sizehave been carried out by the WeldInspector. Inspectors are often onlyconcerned with making sure there are nodefects, not checking that the correct size ofweld has been used based on theengineering. It is imperative to examine thedimensions of a weld, as it correlatesdirectly to its strength. Welds that are toosmall may have insufficient strength towithstand the forces acting on them.

Weld gauges are cheap and relatively easyto use. A trained site engineer should bechecking the weld dimensions as a matterof course to ensure that what is installedmatches the design. Keep in mind that theInspector may not have a copy of thewelding fabrication drawings, so theywould not know the correct sizes to check.

Faulty welds can lead to serious problemsaboard a vessel during sea transit, so NDT isa vital process for detecting any deficienciesprior to the weld being put under load.Visual inspections and dimensionalchecking are a key part of this process andshould involve someone who has a widerunderstanding of the engineering to ensurewelds are fit for their designed purpose.

Written by Lindsay McDougall, TechnicalDirector, Malin Group

HEAVY LIFT TIPNON DESTRUCTIVE

TESTING DIM CONTROL

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