n RULES FOR PLANNING AND EXECUTION OF MARINE OPERATIONS CURRENT BOOKLETS ' JJANUARY 2000 (} (i PART 0 Chapter 1 PART! Chapter 1 Chapter 2 Chapter 3 Chapter 4 .PART2 Chapter 1 Chapter 2 ( (Chapter 3 Chapter 4 Chapter 5 Chapter 6 ().Chapter 7 INTRODUCTION User Infonnation and Indexes ................... .... ................. January1996 GENERAL ' Warranty Surveys ..... ... .......... ................................................................ January 1996 Planning of Operations ......................................................................... January1996 Design Loads ...... .. ....... :............. ............................. ............ .................. January1996 Structural Design ............. .................. : ................................................... January 1996 OPERATION SPECIFIC REQUIREMENTS Load Transfer Operations ................................................ ................... ... January1996 Towing .................... .............................................................................. January1996 Special Sea Transports ................................. ............................ .......... ... January1996 Offshore lnstallation ............ ................. ....... ....................................... ... January1996 Lifting ......... ..................................................... .. t.................. ................January 1996 Sub Sea Operations ............................................................................... J anuary 1996 Transit and Positioning of Mobile Offshore Units ............................... January 2000 DETNORSKEVERITAS Veritasveien 1. N1322 Norway Tel.: +47 67 57 99 00, Fax.: +47 6757 99II n J o DNV - RULES FOR PLANNING AND EXECUTION OF MARINE OPERATIONS - 1996 REVISION CORRECTION SHEET No.1SEPTEMBER 1996 Please note the following clarifications/corrections to the DNV Rules for Planning and Execution of Marine Operations. Pr. lCH.3DESIGN LoADSllEM2.3.3.5 The equation for "d" is printed as d = 1.5 - (1I2j) The last part of the equation may be misunderstood and is more correctly expressed as; d = 1.5 - 1/(2j) Pr.2 CH.6 SUB SEA OPERATIONS.PARAGRAPH 2.3.1 A new item 2.3.1.5 with the following text will be added; 2.3.1.5The effects of enlrapped air/air cushions shall be specially considered.Dynamic load effects aswellas changes in buoyancy forces shall be addressed. Guidance Note Formulas for loads andload effects inthischapter do not consider the effects of entrapped alr or air cushions. Pr.2 CH.6SUB SEA OPERATIONS llEM 2.3.2.1 Equation 2.6 should be understood as i.e.the hydrodynamic force is a function of slamming, dynamic effects of buoyancy, drag and inertia effects. For combining load components into load cases the following combination is acceptable to DNV; Rev. OASign. LUNDPageIof3 ) (F 2F2F2F2 )0.5 Fhyd=,lam+P+ ~ (_+15+ 15/GM),max.40degrees Eq.4-1 provided =forthe design environmental condition is smaller or equal \0 the heel angle where the maximum transverse righting moment occurs,otherwise: ~ 40 degrees Eq.4-2 where _=maximum dynamic heel angle due towind and waves,see also Pt. 1 Ch.3. GM=initial metacentricbeight in metres. Fiure 4.1 - Dlustration of StabiliTerms. RightingArm (GZ) GM Heel Angl 4.2.2.3The areas under the rigbting moment curve and the wind beeling moment curve should be calculated up to an angle of heel which isthe least of; the angle corresponding tothe second intercept of thetwocurves, the angle of progressive flooding,or the angle at whichoverloading of a structural member occurs. The area under tbe righting moment curve should not be less than1.4 timesthe area under the wind heeling moment curve. This stability requirement (A+B) ~ 1.4 (B+C) is illustrated in Figure 4.2 where the righting moment curve isincluded in the sarne diagram. 4.2.2.4For marine operations of very short duration (for instance harbour moves and out of dock operations) covered byreliable weather forecasts,anexemption from the requirements given in 4.2.2.2 maybe acceptable provided that adequate safetyiseusured. However,the stability should be positive to a heel angle15 degrees beyond equilibrium.Such situationsare subject toDNV acceptance. Rules for Marine Operatious Pt. 1 Ch.2 Planniug of Opemtious Fi!!W"e4.2 - Intact Stability requirement ItITACrSTABUTY (A..8)> 1.4(9+ C) ~ RlghllngMoment ffi ~, a > v r ~ 0 7 /EJ ~ /~K 1m ANC1.E 4.2.3Siugle barge damage stability requirements 4.2.3.1Damage stability evaluations shall be based on damage scenarios according \0 identified contingency situations,see 2.1. 1.Collision,leakage andoperational failure situations shallbe evaluated. As a minimum thebarge should bave an acceptable stabilityandreserve buoyancy,and remain floatingin an acceptable manner with anyone submerged or partly submerged compartment flooded. 4.2.3.2The acceptable floating condition is determined bythe following: The design resistance of any part of the barge, cargo seafasteningor grillage should not be exceeded. The barge should have sufficient freeboard consideringenvironmentaleffects to any open compartment,where floodingmayoccur. The area under the righting moment curve should be greater than the minimum area under the wind heeling momentcurve upto: thesecond intercept,or the down flooding angle,whichever isless,see Figure 4.3. 4.2.3.3The consequences of a damage stability situation should be thoroughly evaluated,in particular witbrespectto; progressiveflooding, localstrength of watertight boundaries and loads on seafastening. DET NORSKEVERITAS ( , 'i ) ) Rules for Marine Operations l't.1 Ch.2 Planning of Operations I Fieure 4.3 - Damaee Stabilitv Reouirements DAMAGDSU.BUTY (A+B(B+C) Rightingt,lamenl Z '" > 0 > / 1" 1m. ""'"' } 2.4Multibarge damage stability requirements 4.2.4.1Damage stability evaluatioos sball be based on damage scenarios according to identified contingency situations,see 2.1.1.Collision,leakage and operational failuresituations sball be evaluated. As aminimum tbe harges with tbetransported object sbould remainafloat in stable equilibrium with sufficient freeboardtopreclude progressive flooding with anyone compartmentsopentothesea. The acceptable floatingconditionisdetermined bytbe following: ) The requirements of 4.2.3.2 apply. The steady angle of beel or pitch caused by tile damage nodpressure sbould not immerse anynon watertight closures in the hull. It shallbedemonstrated by calculationthat the floodingof anyone compartment will not cause the damagedbarge toits heel or trim angle relative tothe overallheel or trim of the barge unit,i.e.,the damaged barge should not pivot around anyof the deck supports andthusloose contact with the deck at other support(s). 4.3SELF FLOATING STRUCTURES 4.3.1General 4.3. 1.1This sub-section appliestoobjects such as gravitybase structures, jackets,offshore towers,etc. supported bytheir ownbuoyancy duringtowing and construction afloat. 4.3.1.2The requirements in 4.2.1 apply. ,. 3.1.3Incliningtestsforthefloatingobject should be ..,erformedprior tomarine operation toconfirm the position of centre of gravity,see 4.1.4. 4.3.2Intact stability requirements January 1996 Page 17 of 23 4.3.2.1The followingrequirements sbould bemet by the self-floating object: The initialmetacentric height,GM, corrected for free surface effects andeffect of possible air cushionshould be at leastLOrn. The requirements tointact stability in 4.2.2 apply.For large concrete gravity base structures a reducedratio between righting moment and heelingmoment of 1.3maybe used. Special consideration sbould be given tothe bydrostatic stability andmotions ciuringtransfer of beavyloads to afloatingstructure both under normalconditions andincase of anaccidental loadtransfer. 4.3.3Damage stability requirements 4.3.3.1General requirements to damage stability given in4.2.3apply. 4.3.3.2Damage stability evaluationsshall be based on damage scenarios accordingtoidentified contingency situations,see 2.1.1.Collision,leakage andoperational failure situations sballbe evaluated. Asa minimum tbeself-floatingobject shall normally remainafloat in a stable equilibrium with sufficient freeboardtopreclude progressiveflooding witb anyone compartment open tothe sea,asgiven in 4.2.3.2. Exemptionsfrom thisrequirement are not acceptable unless adequate,approvedprecautions are taken.The precautionsshouldensure acceptable safety,for instance asgiven in4.3.3.3 andlor 4.3.3.4.. 4.3.3.3If 4.3.3.1cannot be complied with,the structure sball witbstandthe collision loads according to Pt. 1 Ch.3 Sec.3,on the whole exposed circumference of the structure from 5 metres belowto5 metres abOveany operation waterline without ingress of water. 4.3.3.4During moored construction pbases, compliance with 4.3.3.3 maybe obtained bysufficient fenderinginthe waterline area. 4.4LOADOUT OPERATIONS 4.4.1General 4.4.1.1Load out operations sball be performed with a minimum inital GM=1.0 m.The requirements in 4.2.2.3and 4.2.2.4 apply . DE! NORSKE VERITAS January 1996 rage 18 of 23 4.4.1.2Specialattention shall be paid tothe influence of slack Uwkson stability afloat during the load out operations. 4.5OTHER VESSELS 4.5.1 Cilp Y= Peakness parameter. The Pierson Moskowitz spectrum appears fory=1.0. The relation between T, and Tpmaybe taken according toEq.2-10. T=TtEL PVu-:;r Eq.2-IO DEI' NORSKE VERIfAS 1996 of20 2.3 .5.4The Pierson Moskowitz spectrum isgenerally r=mmended for open.deep waters ( > 150m) andfully de"... loped seas.The Jonswap spectrum is recommended for fetchlimited.growing seas and in shallow waters. Fo.a general Jonswap spectrum the r parameter may. unlessspecific data are available be taken as (f, in sec.Aco:.Ac2) 2.4.2Tide January 1996 Page 11of20 2.4:2.1The astronomical tidalrange isdefined asthe range between the highest astronomical tide (HA1) and the lowest astronomical tide (LA1), see Figure 2.3. 2.4.2.2Mean water level (MWL)isdefined asthe mean level between the highest astronomical tide and the lowest astronomical tide. 2.4.2.3Storm surge includes wind induced and atmospheric pressure induced effects.Variations due to storm surge shall be considered. 2.4.2.4Characteristic water levels shall be taken as expected astronomicaltide variationsplus/minus storm surge effects.Both a maximum and minimum characteristic water level shall be defined for operations sensitive totidal variations,see Figure 2.3. Fie 2.3 - Definition of water levels MN.1MlmlE\R DET NORSKE VERITAS January 1996 Page Uof 20 Rules for Marine Operations Pt.1 Ch.3 Design Loads 3.LOADS AND LOAD EFFECTS 3.1LOAD CATEGORIES 3.1.1(;eneral 3.1.1.1Loads and load effects shall he categorised into the foUowinggroups; l'erman""t Loads " P, Live Loads - L, Deformation Loads - D, Envirol)Illental Loads - E,and Accidental Loads - A. 3.1.2Permanent loads (P) 3.1.2.1Permanent loads are static loads which willnot be moved or removed during the phase considered. Such load may be; weight of structures, weight of.permanent ballast and equipment that can not be removed, external/internal hydrostatic pressure of permanent nature,and buoyancy (permanent part). 3.1.2.2Characteristic permanent loads shall be based on reliable estimates of weight,weight controlsystem or weighted weight, see also 3.5. 3.1.3Live loads (L) 3.1.3.1Live loads are loads that can be moved, removed or added.Suchloads maybe; opemtion of cranes., loads from alongside vessels, differential ballasting, operational impact loads,and stored materials,equipment or liquids. 3.1.3.2Characteristic live loads shall be specified with maximum and minimum values,both values maybe necessary toconsider. 3.1.4Defonnation loads (D) 3.1.4.1Deformation loads are associated with deformations.Such loads maybe; installation or set downtolerances, structural restraints between structures, differential settlements,and temperature. 3.1.4.2Characteristic deformation loads shallbe ~ u or minimum valuesresultingfrom characteristic environmentalconditions. 3.1.5Environmental loads (E) 3.1.5.1Allloads caused by environmental phenomena shall be categorised asenvironmental loads.Such loads maybe; wind, waves, current, storm surge, tide,and ice. 3.1.5.2Loads due tothe gravitycomponents in plan parallel or perpendicular to deck,caused bymotions due to wind and waves of a floating object,shallbe categorised asenvironmental loads. 3.1.5.3Characteristic environmental loads shall be based oncharacteristic environmentalconditionsas specified in Sec.2. 3.1.6Accidental loads (A) 3.1.6.1Accidental loads are loads associated with exceptional or unexpected events or conditions.Such loads maybe; collisionsfrom vessels, dropped objects, loss of hydrostatic stability, flooding,and loss of internalpressure. 3.1.6.2Characteristic accidentalloads shall be basedon realistic accidentalscenarios. Realistic accidentalscenarios maybeidentified by Hazoptechniques,seePt. 1Ch.2Sec. 2. DEI" NORSKE VERITAS Rules for Marine Operations Pt. iCh.3 Design Loads 3.2LOADANALYSIS 3.2.1General 3.2.1.1Allloads and load effects which during the marine operation mayinfluence operationalprocedure, design or the dimensioning of structures shall be analysised and consideredin planning and preparation formarine operations. 3.2.2Sensitivity st"dies 3.2.2.1Parametric sensitivity studies should be performed if anyload or operational parameters significantly affect the design or the selection of method and equipment. If the result of the study indicates that the operational safetyis critically dependent on anyparameters, increased reliability shan be obtained forthe design solution e.g. by use of conservative characteristic values. Guidance Note The objectives with a sensitivity study are toreveal If minor changes of input parameters critically or unexpectedly affect the design . . 3.2.2.2Consequences of unexpected conditions and loads w.r.t.structural capacity and failuremodes should be investigated.Emphasis shall be put on possible non-linear load effects. Guidance Note Examples of unexpected conditions may be unexpected deformations and load distributions,unexpected weights and C.o.G pOSitions,unexpected buoyancy and centre of buoyancy etc. 3.2.2.3Consequences of malfunctioning equipment and erroneous operation of equipment or systems shall be evaluated. Guidance Note Examples of malrunctionlng equipment may be leaking valves, valves impossible to close,pipeline fracture,unexpected deformation pattern of load distribution elements. Examples of erroneous operation of equipment may ~opening/closing of wrong ballast valve. 3.2.2.4The variations of input parameters shall be within realistic limits.Too small variations shallbe avoided. 3.2.2.5Consequences of parameters outside specified or expected values or ranges may be categorised asa PLS condition. Single unplanned or unexpected events,see3.2.2.2 alld 3.2.2.3, shall not lead toa progressive failure situation. Simultaneous variations of several input parameters outside thespecifieddesign value or range does not be considered. 3.2.3Dynamic effects January 1996 Page 13of20 3.2.3.1Dynamic loads andloadeffects shall be investigated.Dynamic load effectsmay be causedby oscillatory wave forces,wind loadS(gusts),vortex shedding in air or water,or slamming loads. 3.2.3.2Dynamic loading effectsshall be investigated byrecognised methods,realistic assumptions of natural period, damping,materialproperties etc. 3.2.3.3Special considerations should be made tothe possibilities of dynamic amplification. 3.2.3.4Both fatigue andultimate stress or deflection maybe criticalfor the design. 3.2.4Non-linear effects 3.2.4.1Non-linear effects shallbe considered incases where these significantly influence the load estimates. Typical non-linear effects are; material ncm-linearities, geometrical non-linearities, damping effects, non linear effects due to combination of load components or response components,and wave elevation effects. 3.2.4,2Non linear load effects due tocombination of environmental conditions should be evaluated. Guidance Note The quadratic Increase Indrag loads due combination of wave particle velocity and current velocity illustrate such effect. 3.2.5Friction effects 3.2.5.1Effect of frictionshall be considered in the design verification. 3.2.5.2A friction coefficient range,i.e.both a maximum and a J;D.inimumfriction coefficient maybe necessary to considered in the design calculations. 3.2.5.3The frictioncoefficient range shall be defined according to recognised industrystandards or tests,see also Pt.2 Ch.l Sec.2.2.5. 3.2.5.4Consequences of friction coefficients outside the established range shall be evaluated,and if found severe the range shall be extended,see also 3.2.2. 3.2.5.5Vibrations,variating or uncertain surface condition etc.affecting the frictionshall be considered. DET NORSKEVERITAS January 1996 Page 14 or20 3.2.5.6Restraint effects caused bycombination of friction and global deflections shall be considered. 3.2.6Tolerances 3.2.6.1Loads caused by operational or fabrication tolerances exceeding tolerances stated in the design standards/codes sh..n be considered.Typicalexamples may be; . set down tolerances(loadout,positioning), .himming tolerances,and uncertain deformation (in load distributing material). 3.2.6.2Characteristic loads .ball be based on specified maximum or minimum values. 3.2.7Modeltesting 3.2.7.1Testing to detennine motions or loads may be required.Reference isalso made to3.3.3.1 3.2.7.2Adequate andreliable modeltest data sbould be used to verify/correlate tbeoretically calculated envirnnmentalloads.This is particularly relevant for geometrically complex structures and fornew design or operationalconcepts. 3.2.7.3The law of similarity sball be carefully considered in order toobtain a representativetest result. Effects that may influence the measured quantity,and that can not be represented in the modeltest sball be identified and consequences of these effects sbould be evaluated. 3.3WAVE LOADS 3.3.1First nrder wave loads 3.3.1.1Wave loads .hould be estimated accordingto a deterministic or stochastic design method.A wave period range accordingto 2.3.4 or 2.3.5 should be investigated. Guidance Note If any responses are founddimensioning for T 'I.C. .... Ihodf.m.Sirus IL The graphs inAgure 3-1Indicate that thesafety level obtained by applying an1/3 allowable stressIncrease, i.e. fromto 0.8, due to the presence of E loads,are not generally acceptable. Anacceptable safety levelmay be oblalned by; increase the characteristic E loads, or decrease thebasic usage factor, For non linear problems (e,g,buckling)anadditional reductioninthe permissible usage factor may beapplicable in order to ensure an acceptable safety level. DEl NORSKE VERITAS Januar 1996 Page 10of 15 3.2STRENGTH VERIFICATION 3.2.1General 3.2.1.1These Rulesrecommendthepartial coefficient methodfor verification of structural strength.Load and material factorsspecified in thissubsection are according tothe principlesof the partial coefficient method. 3.2.1.2Usage factorsforthe permissible stress method are not defined in these Rules.Permissible usagefactors are to be agreed in each case. 3.2.2Limit state definition 3.2.2.1A limit state is commonly defined asa state in which the structure ceases tofulfilthe function,or to satisf'ythe conditions,for which it was designed. 3.2.2.2The followinglimit state spall be considered in the strength verification; The Ultimate Limit States (ULS),related tothe maximum load canying capacity (yielding limit state,buckling limit state,etc.) The Fatigue Limit State (FLS),related tothe capacity of the structuretoresist accumulated effect of repeated loading. The Progressive Collapse Limit States (PLS), related to maximum load canying capacity under the assumption that localdamage is unavoidable, or that certain parts of the structure have been damagedor removed(see also ULS). The ServiceabilityLimit States (SLS),related to limits regarding structural behaviour under specified conditionsof service or treatment (deflection limit state,vibration limit state,limit states relatedtohuman limits,etc.) 3.2.3Design approach 3.2.3,1The format of the partial coefficient method implies that strength verification of structures or structural element involves the following steps: Identif'y all relevant limit states/failuremodes. For each limit state an!!failuremode,determine tbe design loads and conditions. For eacb limit state andfailure mode,determine the design load effects. For eacb limit state andfailuremode,determine the designresistance. Ensure adequate safety byproving that the design loads or effects does not exceedthe design resislUflce. Rules for Marine Operations Pt.t Ch.4 Structural Design 3.2.4Acceptance criteria 3.2.4.1The fonnalrequirement tbat the structuremay reacbbut not exceed n definedlimit state when subjected to design loads,issatisfiedwbenthe design load effect, Sd'does not exceed the designresistance,R.,for all possiblefailuremodesi.e.; Eq.31 The equation Sd= R. definesthe limit state. 3.2.4.2A design load effect is a loadeffect (sucb as stress or stress resultant)due to a design load i.e.: Sd=S(FJ where S:loading effect Fd:designload S(FJ: S-function of Fd ! ) Eq.32 3.2.4.3A design load isobtainedby multiplyingthe characteristic load bya load coefficient i.e.: Fd=Yr' F. Eq.33 where Yr:load coefficient Fe :characteristicload 3.2.4.4A designresistance isobtained bydividing the characteristic resistance bya materialcoefficient,i.e.: Eq.3.4 where Rc :characteristicresistance 'Ym:materialcoefficient 3.2.4.5In practicaldesign Eq.3] maytake various forms.If R,.can be defined by one single quantity,Eq. 3 ]maybe written as; Eq.35 3.2.4.6If both Sdand R. cannot be defined bysingle quantities,Eq.3] maybe written as; Eq.36 Abovefunctiondescribes a combination of thefractions S ..IR.,through S.JR.", byintemction.A typical example of this case isthe buckling of a plate subjected tovariousstresscomponents,for which thestructural resistance maybe defined separatelyfor eacb component acting alone. DIlT NORSKE VERITAS Rules for Marine Operations Pt.1 Ch.4 Structural Design 3.2.5Ultimate limit state - ULS 3.2.5.1For the ultimate limit states (ULS)the two load conditions aandbasgiven in the Table 3.1 below sball be considered. Table 3.1 - Load factors for ULS .... ... . 1.3I1.3I1.0I0.7I.NA ' 1> ..,.:':;' ,'.' :.:'-"1.0I1.0I1.0I1.3INA Load categories P,l ; 0, E and A are described In Pl.1 Ch.3 Sec.3. 3.2.5.2For loads and load effects that are well controlled a reduced load coefficient Yf =1.2 may be usedfor the P andL loadsinstead of 1.3in load a. Guidance Note: A load coefficient of 1.215 for projects withinthepetroleum actiVities onthe Norwegian continental shelr, subject 10NPD's approval. 3.2.5.3Where a permanent load P (e.g.self weight or hydrostatic pressure)causesfavourablyload effects a load coefficient 1f = 1.0 sball be used for this load in loadcondition a. 3.2.5.4In eases where the load is tbe r"l'ult of counteracting andindependent large bydrostatic pressuresthe appropriate load coefficient sball be applied tothe pressure difference.However,the pressure difference sbould .not be taken lesstban 0.1timesthe hydrostatic pressure. 3.2.5.5In dynamic problems special considerations of application of theload coefficients are necessary.In lieu ofa refined analysis,e.g.sucb as indicated in3.1,the load effectsmaybe foundby application of load coefficients after baving foundthe responses,e.g.after bavingsplved tbe equations of motion for vesselmotion response analysis. ))3.2.6Progressive collapse limit state - PLS 3.2.6.1Possible accidental situations sball be considered against whicb sufficient local strengtb cannot be provided byreasonable means,or against whicb increasedlocal strengtb wouldreduce the safety against overall failure of the structure. Januar 1996 Page 11of 15 3.2.6.2The evaluation of safetyagainst progressive collapse (PLS)sball be carried out in tbe followingtwo steps: 1)Determination of effects (damages) caused by an accidental situation on theintact structure.For this cbeck loading condition c applies,seeTable 3.3 (loads of type E maybe ignored). 2)VerilYtbat the damaged structure mayresist the design loading effect caused by P,L,D, and E without the occurrence of aglobal mode of failure,see 3.2.2. 2.See also Table 3.2, loading condition d. Table 3.2 - Load factors for PLS ''''''''''::' .'''',' ', h1.0I1.0I1.0INAI1.0 ,;d -; .',.>. ":'.,1.0I1.01.01.0INA load categoriesP,l, D.E and A are described in Pt.1 Ch.3 5eO.3. 3.2.7Fatigue limit state - FLS 3.2.7.1For marine operations of long durations and with elements exposed to high cyclic loads tbe possibilities and effects of fatigue should be considered. 3.2.7.2The fatigue limit state (FLS) sball be evaluated accordingtoprocedures given in a recognised code or standard.Such evaluation should be based on the defined operation period and the anticipated load history duringthe marine operation 3.2.7.3Allload coefficients sball be Yf =1.0 3.2.7.4If adeterministicapproacb by calculating a Miner sum isused,the Miner sum sballnot exceed the valuesindicated in Table 3.3. The elements shallbe categorised according to 3.2.7.5Lower valuesfor the Miner sums may be relevant if tbe structure bas been or will be subjectedto fatigue loading before or after the considered marine operation.In sucb easesthe maximum allowable Miner sum for the actualmarine operations sballbe determined by considering tbe totalload historythe structure will be exposed to. DET NORSKE VERIT AS n ) 0 ;RImr--!!::!IJWW PART 2 CHAPTER 1 RULES FOR PLANNING ANDEXECUTIONOF MARINE OPERATIONS PART 2: OPERATION SPECIFIC REQUIREMENTS LOAD TRANSFER OPERATIONS JANUARY1996 SECTIONS 1. INTRODUCTION ................................ . ... .. ... .......................... ............. .................................... 5 2.LOAD OUT ................................................ .. ....................................... .......... ....................... 7 3. FLOAT OUT ............................. .............. ................. .............................. . ............................. 15 4.LIFT OFF ........................................................................................................................... 18 5.MATING............................................................................................................................ 23 6.CONSIRUCTION AFLOAT .............. .... ............... ... ................................................................ 27 DETNORSKEVERITAS VerilasveienI, N-1322 H0Vik,Norway Te\.:+4767579900,Fax.:+47675799 11 ) ) CHANGES IN THE RULES This isthe first issue of the Rulesfor Planning and Execution of Marine Operations,decided bythe Board ofDet Norske Veritas Classification AlS as of December 1995.These Rules supersedes the June 1985,Standard for Insurance Warranty Surveys in Marine Operations. These Rules come intoforce on 1st of January1996. @Det Norske Vcritaa Computer TypescuingbyDel Norskc VeriLaIi Printedin NOrWaybytheOctNOIlike VeritasJanuary1996 1.96.600 This chapter is valid until superseded by a revised chapter.Supplements tothis chapter will not be issued except for minor amendments and an updntedlist of corrections presented in the introduction booklet. Users are advisedtocheck the systematic index in tbe introduction booklet toensure that that the chapter is current. Rules for Marine Operations "1.. 2 Ch.l Load Transfer Operations j January 1996 Page 3 of 28 CONTENTS 1.INTRODUCTION ...................... ....... 52.6LOAD OUT VESSEL.............................. 12 2.6.1 General ................................. : .. .. .. 12 1.1GENERAL ............................................ 52.6.2 Structural strength ........................... 12 1. 1.1Application ... . . ... . ..... .... .... ... .. ........ . 52.6.3Documentation ............................... 13 1.1. 2 Terminology ................................... 52.6.4 Stability afloat ................................ 13 1.1.3 Symbols ........................................ S2.6.S Maintenance .................................. 13 1.2DESIGN PHASE .................................... S2.7OPERATIONAL ASPECfS .. .. ..... ............. 13 1.2.1Planning and design .......................... 52.7.1General ...... . ........................ . .... .... 13 1.2.2 Documentation .... ........ .... ................ 62.7.2 Load out site ... .. ........................... . 13 2.7.3Preparations ..................... .... ......... 13 .)1.3OPERATIONAL ASPECTS ....................... 62.7.4 Grillage and seafasteruog ......... .......... 14 ) 1.3.1Preparations ................................... 6 1.3.2 Recording and monitoring .................. 6 1.3.3 Weather forecast. ................ .... ..... .... 6 } 1.3.4 Organisation ... ............ ......... ... ........ 6 2.LOAD OUT .......................................... 7 2.1GENERAL ............................................ 7 2.1.1 Application .................................... 7 2. 1.2 Plamiing and design .............. ............ 7 2. 1. 3 Load out class ................................. 7 2.2LOADS ................... ... .. ... ..... . ............... 7 2.2.1 General .................... ..................... 7 2.2.2 Weight and CoG .............................. 7 2.2.3Weight of load out equipment .............. 8 2.2.4 Environmentalloads......................... 8 2.2.5 Skiddingloads................................ 8 2.2.6 Skewload ...................................... 8 2.2.7 Other loads.................................... 8 2.3LOAD CASES AND ANALYSIS OF FORCES9 2.3.1 General .. ...... .. ... . ...... ..... . ............... 9 2.3.2 Loadcases ...................................... 9 2.4STRUCTURES AND SOIL ........................ 9 2.4.1General ......................................... 9 2.4.2 Quays ........................................... 9 2.4.3Soil .............................................. 9 2.SSYSTEMSAND EQUIPMENT ................... 9 2.5.1Geoeral .... ....... .............................. 9 2.5.2 Push/pull systems ..... : ....................... 9 2.5.3 Trailers ................. . .................. .. .. 10 2.S.4 Skidding equipment ......................... 10 2.5.5 Barge ballast system ......................... II 2.S.6 Power supply ................................. 12 2.S.7 Testing........................... . ............ 12 2.5.8 Mooring andfendering..................... 12 2.7.5 Monitoring ................................... 14 2.8SPECIAL CASES ............ ....................... 14 2.8.1Load in ........................................ 14 2.8.2 Barge to barge load transfer ................ 14 3.FLOAT OUT ....................................... 15 3.1INTRODUCTION .................................. IS 3.1.1Application ................................... 15 3.1.2 Planning and design basis ........ ......... . 15 3.2LOADS ....................... ...... .. ... . .. ......... . IS 3.2.1Geoeral ....... .. ... ................ .. ... : ...... IS 3.2.2 Weight ......................................... IS 3.2.3 Buoyancy ..................................... 15 3.2.4 Other loads ................................... IS 3.3LOADCASESAND ANALYSISOF FORCESI5 3.3.1Basic loadcasesand structural analyses.. IS 3.4STRUCTURES ................. .. ................... IS 3.4.1General ........................................ 15 3.4.2 Stability afloat. ............................... 16 3.5SYSTEMS AND EQUIPMENT.................. 16 3.5.1General ........................................ 16 3.5.2 tnstallation systems .......................... 16 3.5.3 Air cushion systems ......................... 16 3.5.4 MooringlPositioruogrrowing System .... 16 3.6OPERATIONAL ASPECTS ...................... 16 3.6.1General .......... ........ ................ ...... 16 3.6.2 Float out site .................... . ........... . 16 3.6.3Clearances .................................... 16 3.6.4 Monitoring.... ................. . ............. 17 DlIT NORSKE VERITAS ) ) January 1996 Page 4 of2S 4.LIFT OFF ................................... ... .... 18 4.1GENERAL .................................. . .......18 4.1.1Application... . . .............................18 4.1.2 Planning and design basis .................18 4.1.3 Lift off class ......... . ............. . .. ... ....18 4.2LOADS .... ... . ................. . ..... . ........... '"18 4.2.1General ............. ..... . ........ ... .........18 4.2.2 Skew loads ................. ..... ........ .. ...18 4.2.3Other lo.ds ............................ .. .....19 ' 4.3LOADCASESANDANALYSIS OF FORCES19 4.3.1General .................... . ..................19 4.3.2 Basic loadcases andforce distribution .. .19 4.4STRUCTURES ....... . . ..... ... . ........ . ..... . ....19 4.4.1 General .............. . ................ .. ......19 4.4.2 Object.. ............ . . .........................19 4.4.3 Plnstruction supports ......................19 4.4.4 Barge supports ...............................19 4.5SYSTEMS AND EQUIPMENT ........ .. ....... 20 4.5. 1 General........... ..... ............... . .. ... ..20 4.5.2Ballast system .. ............................. 20 4.5.3 Positioning systems .......... . .............. 21 4.6UFT OFF VESSELS ........... ..... ..............21 4.6.1General................ ... ..... . .............. 21 4.6.2 Structural strength .................... .. . ...21 4.6.3Stability afioaL .......... . ................... 21 4.7OPERATIONAL ASPECTS ....... . ......... . ...21 4.7.1General..... ... .. .... ........... . ............. 21 4.7.2 Lift off site .............. .. ...................21 4.7.3Preparations . ................................. 22 4.7.4 Clearances ........... ... .................. . .. .22 4.7.5 Monitoring andmonitoringsystems ..... 22 5.MATING ..... .... . ........................ 23 5.1INTRODUCTION ...... . .......... ... ............ .23 5.1.1Application... ............................... 23 5.1.2 Planning anddesign basis.......... . ...... 23 5.2LOADS ............ . ................. ...... ... . .. ....23 5.2.1General .... ... ...... . . ............ . ........... 23 5.2.2 Skew loads . . ................................ .23 5.3LOADCASESAND ANALYSIS OF FORCES23 5.3.1Basicloadcases and force distribution ...23 5.3.2 Additionalloadcases ..... .......... ..... . . ..23 5.3.3Deck horizontalrestraint ...... ............ 24 Rulesfor Marine Operations Pt.2 Ch.l Load Transfer Operations 5.4STRUCTURES ............................ .. ........ 24 5.4.1General .......... .. . ...... ...... ............ ... 24 5.4.2 Barge supports...................... .. ... . .. 24 5.4.3 Substructure .............. ................ .. . 24 5.5SYSTEMSAND EQUIPMENT .. .............. .. 24 5.5.1 General .................... ... ..... .... ........ 24 5.5.2 Multi barge ballast systems............. .. . 24 5.5.3 Substructure ballast and sounding systems24 5.5.4 Primary positioning system ................ 25 5.5.5 Secondary positioning system ........ .... .. 25 5.6OPERATIONAL ASPECTS......... ... ..........25 5.6.1 General .. ......................................25 5.6.2 Mating Site ................... . ............... 25 5.6.3 Preparations.................................. 25 5.6.4 Clearances .....................................26 5.6.5 Monitoring and monitoring systems ...... 26 6.CONSTRUCTION AFLOAT.. . . ..... ... . . 27 6.1INTRODUCTION ..... . ............................27 6.1.1Application ................ ... ............. ...27 6.1.2 Planning and design basis ........... . ......27 6.2LOADS ................................... .... ........ 27 6.2.1General ...... ................. .. .... . ...... .... 27 6.3STABlUTY AFLOAT .... ........ . . ............... 27 6.3.1 General ..................... . ............ . ..... 27 6.3.2lnclining tests . ..... .. .... .. ........... ...... .27 6.4MOORlNG ........................................... 27 6.4.1 General ........................................ 27 6.4.2 Anchor lines ..... .. . . ........... ..... ......... 28 6.4.3 Auxiliary anchoring equipment.. .......... 28 6.5OPERATIONAL ASPECTS .. .. ............. ..... 28 6.5.1General . . ................. . .......... ..... ..... 28 Table List. Table 2.1 - Load out class definition ........ ....... ........ 7 Table 2.2 - Friction coefficients .......... . . ... ........ .... . 8 Table 2.3- Push/pullrequirements .. .....................10 Table 2.4 - Ballast capacityrequirements....... .. ......11 Table 4.1- Lift off class definition .................. .....18 Table 4.2 - Ballast capacity requirements........... ... .20 DET NORSKE VERITAS o ) Rules for Marine Operations Pt.2 Ch.l Load Transfer Operations January 1996 PageS of28 1.INTRODUCTION 1.1GENERAL 1.1.1Application 1.1.1.1Pt.2 Ch. !. Load Transfer Operations.gives specific requirementsandforloadout, float out, lift off and mating operations.This chapter also appliesfor the construction afloat phases. 1.1.1.2General requirementsforplanning,design and execution of marine operations are given in Pt. 1 Ch.2. 1.1.1.3Re 500 tonnes).For highly loaded barges separate analysis/calculations are recommended for verification of local deck strength. VET NORSKE VERITAS n , ) January 1996 Page 8 of 14 Rules for Marine Operations Pt.2 Ch.2 Towiog 3.TOWING EQUIPMENT 3.1TOWING ARRANGEMENT 3.1.1",",eraI 3.1.1.1Towing equipment shallbe arranged sothat proper control over towed object isensured. 3.1.1.2The followingitemsshouldbe considered w.r.t tostructural strengthandoperationalpracticalities, towing brnckets ontowed objcct, fuirleadson towed object. arrangement of towing line, possible fibreropelowing pennant, wire lope towing pennant, chain bridle/wirerope bridle/single leg chain, flounder plate, shackles, rings, thimbles,and recoveringarrangement. 3.1.2Main towiog line 3.1.2.1The minimum breaking load.intonnes. of the towingline should he Illken accordingtoEq.3-1. where 4BP 0.8BP 1 6 . J B ~2.2 BP BP130 Eq.3-1 BP :static hollard pull of the vesselin tonnes. Guidance Note The lower limit of 2.2 BPcorresponds to a loadfactor of 1.3, a materialfactor of 1.5 anda OAF of 1.1,. 3.1.2.2The requiredtowline MBL mayaIso be influenced by length of towing linetobe used, towroute, number of tugs andtowfleet arrangement, nature of thetowedobject, winch design, and available hack-up/contingency. 3.1.2.3The maintowingline should for offshore towing have a length Dolless than; l.,...w,.=2000BPIMBl.,...w,. Eq.3-2 where l.,...w,.:minimum tow line length (m) BP:static bollard pull of the vesselin tonnes. MIlL....... : towline MBL in tonnes 3.1.3Towiog bridle 3.1.3.1Abridle should be usedforconnection of the towline tothe towed object.Chains should he usedin the way of chafing areas such as fairlends. 3.1.3.2Eachsingle leg,componentsand connections (shackles.rings etc.)in the bridle shaIlhave a MBL not lessthan the MBL of the maintowline.Reductionsof equipment MBL duetobending inwayof fairleads, end connections elc.shallbe considered.Fairlea.dsshall have a shape preventing excessive bending stressinthe chain links/wire. Guidance Nole Shackles,rings-etc. are normally acceptable if statedsafe workfng load(SWl) Is minimum 113 of the main towlineMBL. 3.1.3.3A towing bridle should nonnal\y be attached to towing brackets. 3.1.3.4Endconnections of wire ropes should preferably be spelter ,sockets.Pressed connectionsfitted withthimbles maybe used.Spliced connections should be avoided. 3.1.3.5Pennants with lower minimum breaking loads thanthe main towline may be attached if a reduction of thedimensions of the towline attachments is desired. However the minimum requirements in 3.1.2 shall nlways be complied with. 3.1.3.6A recoverywire rope shouldbe fitledtothe flounder plate,or if single leg connections are used,to theend of the legs.Therecoverywire rope should be leadtoa winchinan accessible position. The recovery wire ropeshould have a minimum breaking load not lessthan 3timestheweight of the bridle or leg. DETNORSKE VERITAS Q); ) Rules for Marine Operations Pt.2 Ch.2 Towing 3.1.3.7Fibre rope pennants should nonnally not be usedwherethere isadequate depthandsearoomto allowforsufficient shock absorbinginthetowline catinary. If fibrerope pennants are used the pennants shallbe in ... new condition.Minimum breaking load of anyfibre rope pellDantsshallnot be less than; 2.3timesthe towline MBL for tugs with bollard pull lessthan 50 tonnes, 1.5 times thetow line MBL fortugs with bollard pullgreater than100 tonnes,and linearlyinterpolated between1.5 and 2.3times the towline MBL for tugs with ballard pull between 50 and100 tonnes 3.1.4Towline attachments 3.1.4.1Towline attachments shall be designedtoresist towline pullfromanylikely direction,with the use of fairleadsif necessary. 3.1.4.2The ultimate capacity of any towline atlacbment (bracket, ballard andtheir foundations)sball not beless than1.3timestheminimum breaking load of the towlipc. 3.2BARGES 3.2.13.2.1.1Generalrequirementstobarges aregivenin Pt.]Ch.2 Sec.5.2.Strength verification of barge structure and barge be according to 2.3. 3.2.1.2Towing equipment shall complywith requirementsin3.1. 3.2.2Emergencylowing arrangement 3.2.2.1Anemergency towing wire rope of with minimum length equaltobarge length shall be connected toa bridle or single leg connection,andlashedtothe barge sidefor easyrelease.A recoverytrailingli,oe with a pick-Up buoy shallbe filled to the emergencytowing wire rope. January 1996 Page 9 of14 3.2.2.2The trailing .Iine shallbe of floatingmaterial and shall have aminimum breaking load not less than 30 tonnes.The distancefromthe aft extremity of thelowed objecttothe buoy shall not be less than 50 metres.In add ilion 10thetrailing line,n messenger line of length 100 metresmaybe considered necessarybetweenthe buoy and the trailing line. 3.2.3Anchoring and mooring equipment 3.2.3.1Abarge should nonnally have at least one anchor availableforemergencyanchoring.A windlass or similar arrangementshouldbe andcapable of paying out and holding the anchor.The anchor should be secured withaeasy releaSe arrangemeDt. The anchor line length and MBL shall comply withthe Rules of theClassification Society. Guidance Note For barges classedbyDel Norske VeritasreferenceIsmade to Rulesfor Classification of Ships,Pt.3 Ch.3 Sec,3. 3.2.3.2Mooring ropes of adequate strength andlength shaJlbe available on board. Guidance Note ItIsrecommended tohave at least 4 mooring ropes of110m each (or 2 of 220m each)available onboard. 3.2.4Ballast and drainage systems 3.2.4.1The drainage system and bilge pumps should complywith the Rules of the Classification Society. 3.2.4.2If the barge bilge pumps are out of order or if bilge pumps are not filled,hilge suction may be arranged by portable pumps placed on board the barge. 3.2.5Access 3.2.5.1The barge shall be equipped with adequate accessmeans,' allowing safe cntenngfrombothsides of the barge during towing. 3.2.6Inspection and testing 3.2.6.1The barge, object,equipment,and arrangements shall be availablefor inspection before departure of the tow. 3.2.6.2Functional testing of machinerythat maybe used duringthe voyage should be performed.The machineryshould be tested in presenr..,or bythe personnelwhowill operatethe systems. DET NORSKE VERITAS I I, I ) ) January 1996 Page 10 of 14 3.2.7Barge docwnentation 3.2.7.1GenernI description of barge systems sballbe presented.Ballast and towing equipment/systems shall be described indetail. 3.2.7.2The following main particulars should as a minimum be described; object particulars. name,signal letters, owners andport of registry of barge. draught during towing. stability propertiesforintact and damaged conditions, specification of anchoring andmooring equipment,and the class of the barge (if any).length.breadth. depth. and year of bUild.etc. 3.2.7.3The followingmain dmwings should normally be presented; generalarrangement, load charts if applied. midship sectioD.longitudinal section andother plansfor evaluation of structural strength.if such evaluation isfound necessruy, drawings showing arrailgementandscantlings of towing brackets.boUards and fairleads. themain andemergency towing arrangement,and recovering arrangement. 3.3TOWJNG VESSELS 3.3.1General 3.3.1.1Generalrequirements totowing vessels are given in Pt. 1Ch. 2 Sec.5.2. 3.3.1.2Towing equipment shall comply with 3.1. 3.3.2Criteria for.selection of towingvessel.s 3.3.2.1Towing vessels shall be selectedto enable; effective utilisation of ballard pull, good manoeuvrability. simple disconnecting opemtions,and simple recovery. 3.3.2.2The towing vessels shall be equipped with a towing winch. see 3.3.4.Towing withhooks should onlybe used for assistance andinsheltered waters. 3.3.2.3Necessary towingforce should be estimated based on the planned towing route. Rules for Marine Operations Pt.2 Ch.2 Towing 3.3.2.4Towing forcefor open sen towing shall be sufficient tomaintain zerospeed underthefollowing conditions. sustainedwind velocity head current velocity significant wave height Vw = 20[mls] . V,= 1 [mls].and Ii, =5 [m]. 3.3.2.5Towingforcefor coastal towing and towingin narrow or shallow watersrepresenting a dangerfor grounding,shall be sufficient tomaintain a speed over ground,insafe direction,of minimum2 knotsunder defined environmental design conditions. Guidance Note Aboverequirements are based on thenecessity to control the tow offshore,and to ensure adequate manoeuvrability inshore andIn narrow walers. Guidance Note SImplified wave drift force componentsfor single"box"shaped barges may be calculated according Eq. 3-3, provided; UB>3.0 BfT> 6.0 v = o Eq.3-3 where Fdr1 ft Wave driftforces HaSignificant wave heIght BBreadth Llength TDran vToWingspeed (through water) (kNl 1m] 1m] Iml (ml Iknots] 3.3.2.6Requiredtug boUard pullshall be estimated based on calculated required lowing force.tug resistance,andtug efficiency in waves. Unless more accurate calculations of tug efficiencyare made.the CO!1tinuousboU';d pall stated in the bollard pull certificate shall be multiplied with an efficiency factorsof; 0.85 0.75 inshore offshore 3.3.2.7For towing with short l(lwlines the interaction effects due to propeller mce between tug and the towed object sball be considered in estimates of required pull . Unless moreaccurate analysis are performed an efficiencyfactormay be takenas; where au..:Interaction efficiencyfactor. I.,..."",> 30m Eq. 34 A.z,.:Projected cross sectional areaof towed object io 2 m . r,.......:Towline length in metres. '1= 2. 1 fortypical barge shapes. DET NORSKE VERITAS D> .-1 Rules for Marine Operations Pt.2 Ch.2 Towing 3.3.3Towing lines 3.3.3.1The requiremenls of 3.1.2 apply.Minimum requiredlowline MBL shallconsider bending oftow line over stem, or aroundother towline guiding/steering equipment. 3.3.3.2Tugs shouldbe equipped with suitable anti-chnrmgequipment. 3.3.3.3Gogropeor alternative arrangementshould be provided to prevent athwartship pullfromtbetowing line. 3.3.3.4For offshore towingone sparetowline, satisfyingrequirementsin3.1.2, shall beavailable onboard,preferablyona second winch drum. Additionally the followingspare equipment shouldbe kept available on boardthetowing vesselandlor the towed object. 1 pennant 2fibre rope springs,if used A suitable Dumberof shacldcs,rings,and other connecting equipment for atleast one complete towingline cpofiguration 3.3.4Towing winches 3.3.4.1The towing winch shall be approved according classification requirements. 3.3.4.2Winchesfor opensea towingshouldbe remote operated from the wheel house and so designed and instrumentedtbatitwill be possible todetermine the loads inthe wireropefromthe drum.As examples,this maybe arrangedeither directlybyuse of a load cell or indirectly whenthe brake is actuated byhydraulic pressure. 3.3.5Equipment for personnel transrer 3.3.5.1At least one suitable workboat with propulsion should be carriedonboardfortransferriugpersonnel and equipment from the towing vesseltothetowed barge. If the workboat is of the inflatable type,aflooring of adequate strength should be fittedtoallowthe carriage of heavyobjects. 3.3.6Vesseldocumentation January 1996 Page 11ofl4 3.3.6.1The followingmain particulars shouldnormally be described; name,signal letters, owners and port of registry I main engine(s):manufacturer andnumber, maximumcontinuous output andcorresponding r.p.m., static continuous bollard pull, propeller(s):number,type, .whether nozzle is fitledor nat, side thrusters (if fitted):position andthrust, fuelcapacity, fuelcansumption.tonnes per day,and stability particulars for departure and arrival loading conditions. 3.3.6.2Towing vessels sballhave a ballard pull certificates not older than10 years.The bollard pulltest procedure shallbestated. If the vessel hasundergone significantstru.cturalor machinery changes a renewed bollard pull test maybe required. 3.3.6.3For the towing winch andtowing lineslbe followingshould be available: Certificate andparticularsforthetowingwinch stating manufacturer,type,maximumhalding and stalling pawer. Certificatesfar main andspare towing wire ropes, stating manufacturer.diameter of~ p e length, construction,naminaltensile strength af wires, breaking strength. A logfar thetowinglines,givingthefollowing information oneachrope; datetakenin use, records of inspection, dateof renewalof endsockets or other end connections and report on damagetothe rope. Certificates for shackles,rings and connecting equipment. 3.3.7Inspections and testing 3.3.7.1Before departure an inspection of the towing vesseland towed object including allparts of the 19wing arrangementshallbe carried out tocanfirm compliance with above statedrequirements. Functional testing of towing winch systems sball asa minimum be carried out. 3.3.7.2Aninspection of thetowing wire ropes shall be perfonned.At least thefirst50 metres of the towing wire shouldbe streamedforinspection. DET NORSKE VERITAS ) January 1996 Page 12 of 14 3.3.7.3The towing line shall not be used if; the reduction of towline strengthduetowear, corrosion and broken wires ~ x e e d s 10% and there are severe kinking,crushing,orother damages resulting in distortion of the rope structure. End sockets or other end connections should nonna1ly Dotbe olderthan 2 years,depending on the extent of use (wear and tear). Guidance Note The low line should besubject for special evaluations if number of broken wires over a length of 7 times the tow line diameter exceeds 6% of total number of wiresIn the tope, If significant wear of outer layer of wiresare foundor if the tow line Isfound significanUy corroded. Guidance Note Special attention shouldpaid10 the connection of end sockets. DET NORSKEVERITAS Rules for Marine Operations Pt.2 Ch.2 Towing tal (\"III \) '. Rules for Marine Operations Pt.2 Ch.2 Towing January1996 Page 13 of 14 4.TOWlNG OPERATIONS 4.1TOWOUT 4.1.1Tow out criteria 4.1.1.1Atowout criteria sball be established for all towing opemtions. A towout criteria of Beaufort force5 or betterfor the coming 24 bours is normally acceptable. Based upon evaluations of tow out route,type of tow andtow arrangement other towout criteriamayhe accepted. Guidance Note The Intention with the tow out criteria Is to allow timefor familiarisation withthe low, and to ensure adequate distance 10 shore Incase of adverse weather conditions. 4.1. 1.2The tow out should take place with good visibility.Due care should be giventoeffects of snow.rain,fog,etc . . This is particularlyrelevant if towmaster is unfamiliar withthe area.Assistance local should be evaluated. 4.1.2Weather forecast 4.1.2.1Arrangementsforreceiving weatherforecasts at regular intervals prior to IlDdduring towing shall be made. 4.1.2.2Weather forecastrequirements sballcomply with Pt.l Ch.2 Sec. 3. 2. 4.1.3Internal seafastening 4.1.3.1All loose items shall be properly"sccured andlor stowed.Items that maybe.damagedby water shallbe adequately protected. 4.1.3.2Securing of internalitems weighing more than 5tonnes shall be verified by calculations according to 2.3. 4.1.3.3Internal seafastening by meansof steel wire ropes,clamping devices,etc .may be acceptedfor securingsmaller itemssuch aspiping,valves,etc. 4.1.4Towing manual 4.1.4.1Atowing mIlDuaishallbe prepared and distributedto key personnel.The towmaster sball familiarise himself with the towing procedure and briefed aboutessentialinformation in thetowing manual(limitations,restrictionsetc.),see also Pt.] Ch.2 Sec.3.5. 4.1.4.2The towing procedure shall normally contain detailed information regarding; tow out cliteria, criteria for seeking shelter, towing route, ports/areas of shelter, estimated towing time (EID,ETA), envjronmentallimitations w.r .t.structural capacityof object,senfnstening,grillage etc . contingency actions, description of the ballast conditioD, reportingroutinesforprogress of thetow. ETA,status,etc. , contact persons andtelepbone numbers, expected environmental conditionsforthe intendedtowingroutefor tberelevantseason, and Procedures for departure and arrival as well as calls at intermediate ports. 4.2TOWING 4.2.1Routing 4.2.1.1The routing sball be chosen sothat adequate bottom clearance andsea room areavailable duringthe towing.Considerations shouldbe to navigational accuracy,environmentalconditions and loads,motion characteristics of the unit.possible heel and trim effects,towingforce.etc. 4.2.2Towingcleamnces 4.2.2.1The tow should normallybe routed sothat a minimum uoderkeel clearance of 5metres forbarge and tug is obtained.Clearances lessthaa 5metres sball be evaluated in eacb case. DET NORSKE VERITAS I' ) ) ) January 1996 Poge 14of14 4.2.2.2The combination of bollardpull andtowline length should be so thata clearance of at least 5metres between towline bight and seabed i. rosintained. 4.2.2.3The widtb of the towingroute sbould normaIly be at least three timesthe widtb of the tow. Narrow cbanaels sbould be passed in with good visibility 4.2.3Towing procedures 4.2.3.1The tow sball not commence uoder more adverse environmentalconditionsthanspecified by the operational or characteristic design criteria. 4.2.3.2During normal operation,the le"gth of the towingline should be adju.ted at regular interval. to avoid cbafing at the stem rail. 4.2.3.3The crew of thetowing vessel(s) and the boarding crew or permanent crew forthetowedobject shall be familiar withtheequipment andinstallations which may be used duringthe voyage.A demonstration of the operation of bilge and ballast systems,anchoring arrangement,etc.on the towed object may be required before departure. 4.2.3.4Slack tanks sbould be avoided.If used,it should be verified that the specified slack tanks will not jeopardise the stnbilityor strength of the barge. 4.2.3.510 order to avoid slamming and improve seakeeping it is recommendedtbatthe towed barge is trimmed minimum 0.005times barge length by stem, and ballasted to a draft at bow of minimum 0.15times barge depth. 4.2 .. 3.6For large tows or towing close to shipping lanesthe use of a guard ship to prevent other vessels and objects fromjeopardi.ing tbe tow sbould be considered. 4.2.3.7For towing in areas with high traffic density anescort tug should be available to assist in case of a break down fthe rosin tug. The presence of a riding crew on the barge mayalso be relevant insuch waterstopick upantowline.or release the anchor,incase of towlinefailure. DET NORSKE VERITAS Rules for Marine Operations. Pt.2 Ch.2 Towing I. ) () ) :! V: densityof sea water,normally= 1025[kgfm'l volume of displaced waterduringdifferentwhenpassing throughthe watersurface[m 2.3.1.3For objects that mayemerge after submergence, the possibilities of anincreasedweight duetoentrapped water shallbe considered. 2.3.1.4Snapforces in lifting wire will occur if hydrodynamic force exceedsstatic submerged weight of object,see 2.5. 2.3.2Characteristic hydrodynamic force 2.3.2.1The characteristic hy.drodynamicforceon object when lowered throughwatersurfacemaybetaken as: F.,.=F..... +Fp+F.....+F"""" Eq.2-6 where FI1am:characteristic slammingimpact Jorce,see 2.3.3 F p:characteristic buoyancyforce.see 2.3.4 F.....:hydrodynamic dragloads. F....,.: hydrodynamicinertia loads. January 1996 Page 9 or 18 2.3.3Characteristic slamming impact force 2.3.3.1The characteristic slammingimpactforceonthe bottomof the object whenpenetratingthewater surface maybe takenas: F.Jam=0.5pC. Ap VIZ Eq.2-7 where p:densityof sea water,normally= 1025[kgfm'j C.:slamming coefficient whichmaybe determinedby theoreticaland/or experimentalmethods.For smoothcircular cylinders C.should not betaken less than3.0.Otherwise,C.shouldnot be taken lessthan 5.0. Ap:area of clementspenetratingthe water surface. projected on a horizontal plane[m] v.:slamming impact velocity[mI_] 2.3.3.2The slamming impact velocity may be calculated by: v.= +3lH. [0528(4v,)-0 ...+1.645]+ V, 4 +31H .. Eq.2-8 where Vet:cranetipvelocity,see Eq . .2-2 v.:hook lowering velocity,typically0.50 [mls] H, :Significant wave height of design sea state 2.3.4Characteristic buoyancy force 2.3.4.1The lifting force acting on the object due to buoyancyforcesduringsurfacepenetration phasemaybe taken-as: F,= mg[1(IpgAp)(K)' .] (K+pgA,)m [N] Eq.2-9 where m :mass of object in air[kg] g:acceleration due to gravity= ?81[mi.>:! v r:characteristicvertical,relative velocitybetween object and water particles[mi.] K :stiffness of hoisting system[NfmJ 2.3.4.2The characteristic vertiCilIrelative velocity between object and water particles maybe laken as: v, =[mls] Eq. 2-10 where d :distancefrom water planetocentre of gravity of submerged part of object.[m] DET NORSKEVERITAS ) ) ) January 1996 Page 10 of 18 2.3.4.3The stiffuess of the hoisting system maybe calculatedby: II1111 -=--+--+--+--+--Kk,,,,,k"",k."",kboomk ..... Eq.2-11 where K: stiffness of hoisting system[N/m] stiffness of single wire line stiffness of soft stropif used k\l.il"t: k.,,(l:. kblock: kboom: k....,: stiffnessof multiple wirelines ina block stiffness of crane boom other stiffness contributionsif any 2.3.4.4The stiffnessof craJieboom is often neglected asitisusuallymuchlargerthantheline stiffness'.The line stiffness'maybe calculated.by: k=EA, L where [N/m] Eq.2-12 E: modulusof elasticity[N/m'] A,: effective crosssection areaof line,if multiple linestheareasaresummarised[m1 L: totallengthof line(s)[m] 2.4HYDRODYNAMIC FORCES ON SUBMERGED OBJECTS 2.4.1Characteristic total force 2.4.1.1Tho characteristic totalforce on object when object issubmergedmaybe takenas: FtctaI = F 5Iu1icFhyd Eq.2-13 where FroW,:static submerged weight of object,see 2.3.1.2[N] Ph".:characteristic hydrodynamic force[N] 2.4.1.2The espacity of the lifting equipment should be checked according toPt.2Ch.5 Sec. '1applying: D AF =F.12lic +Fbyd F.1:I.1ic where Fh,. maybefoundby Eq.2-16. Eq.2-14 Rules for Marine Operations Pt.2 Ch.6 Sub Sea Operations 2.4.1.3Soapforcesinlifting wire will occur if hydrodyopmicforceexceeds staticsubmerged weightof object.In such case,thedynamic amplificationfactor should be takenas: Eq.2-15 where F.DIIP may be foundaccordingto2.5.2.. 2.4.2Characteristic hydrodynamic force 2.4.2.1The hydrodynamicforce ontheobject consists of massforcesand dragforceswhich maybe combined by: where Pm: F, : characteristicmassforce characteristic dragforce [N] Eq.2-16 [N] [N] 2.4.2.2The characteristic massforce duetocombined acceleration of object andwater particlesmaybetaken as: where m: m".,. : n,,: p: v: a.,: [N] Eq.2-17 mass of object in air[kg] addedmass of object[kg] characteristic single amplitudevertical acceleration of cranetip,see 2.2.4[m/s2] densityof sea water,normally= 1025[kglm1 volume of displaced water[m1 verticalwalerparticle acceleration [mil] 2.4.2.3The added mass of the object may be takenas: m".,.=pVCm Eq.2-18 where em:addedmasscoefficient as a functionof depth, which may be determined by theoreticalandlor experimentalmethods. 2.4.2.4-The characteristic waterparticle acceleration maybe takenas; ( 032dJ' aw =31H,e-"""""'Hs'""" [mls' Eq.2-19 where d :distance fromwater plane tocentre of gravityof submergedpart of object [m]. H..:Significant wave height of designsea state DEl' NORSKEVERITAS o c Rules forMarine Operations Pt.2 Ch.6 Sub Sea Operations 2.4.2.5The characteristic dragforcemaybe takenas: Fc= 0.5 P CdApvr2 Eq.2-20 where Cd:dragcoefficient asafunctionof depth,whichmay be determined bytheoreticaland/or experimental methods. Ap:area of object projected on a horizontal plane[m']. Vr:characteristic verticalrelative velocity between object and water particles,see 2.3.4.2 [mls]. 2.4.3Effect of moonpool 2.4.3.1Characteristic hydrodynamic forcewhen object is loweredthrough amoon-poolmaybe computedin accordance with2.4. 2 but with adjustedmass- and drag-coefficients. 2.4.3.2The mass- anddrag-coefficients emandCd shouldbesubstituted byfmemandfdCdrespectively, where: fm=1+1.9(AplAmp)2.25 I-OS(A, I Am,) fd= [1- (A, IAmp)]' Amp ;cross sectionalarea ofmoon-pc;JOI[m1 A, :area of object projected on a horizontalplane [m'l 2.SSNAP FORCES IN HOISTING LINE 2.S.1General 2.S.1.1Snapforce,,mp.ybe causedbysudden velocity changes inthe handling system due tostartor stop,or byslack hoistinglinesdue tohydrodynamic forcesexceedingstatic submergedweight: Fhyd>Flttltic Eq.2-21 where FblandF ...,are given by 2.3.1, 2.3.2 and 2.4.2. 2.5.1.2Snapforcesdue tolarge hydrodynamicforces shallasfaraspossible be avoided.Weather criteriafor operationshould be adjusted to ensurethis. 2.5.1.3Snapforcesdue tostart or stop should be taken into due considerations.Snaploads duringstart/stop maybe taken according to2.5.2.1. January1996 Page 11of 18 2.5.2Characteristic snap force 2.S.2.1Characteristic snaploadsduringstartandstop may betakenas: Eq.2-22 where snapvelocity see definitions2.3.1,2.3.4 and 2.4.2 m"" [mls] 2.5.3Characteristic snap velocity 2.5.3.1Thesnapvelocityduringstart andstopmaybe takenas; V'Iap:maximum normaltransportvelocity.typically 1.0 mi. 2.5.3.2The snapvelocityoccurringif hydrodynamic forcesexceedstatic submergedweight maybetaken as: Eq.2-23 where VI{:freefallvelocity,see 2.5.3.3[mls] vr:characteristic verticalrelative velocity between object and water particles,see 2.3.4.2[mi.] 1. forVff