DAMAGE ASSESSMENT OF FIBRE ROPES FOR OFFSHORE MOORING

Transcription

1 RECOMMENDED PRACTICE DNV-RP-E304 DAMAGE ASSESSMENT OF FIBRE ROPES FOR OFFSHORE MOORING APRIL 2005

2 FOREWORD (DNV) is a autoomous ad idepedet foudatio with the objectives of safeguardig life, property ad the eviromet, at sea ad oshore. DNV udertakes classificatio, certificatio, ad other verificatio ad cosultacy services relatig to quality of ships, offshore uits ad istallatios, ad oshore idustries worldwide, ad carries out research i relatio to these fuctios. DNV Offshore Codes cosist of a three level hierarchy of documets: Offshore Service Specificatios. Provide priciples ad procedures of DNV classificatio, certificatio, verificatio ad cosultacy services. Offshore Stadards. Provide techical provisios ad acceptace criteria for geeral use by the offshore idustry as well as the techical basis for DNV offshore services. Recommeded Practices. Provide prove techology ad soud egieerig practice as well as guidace for the higher level Offshore Service Specificatios ad Offshore Stadards. DNV Offshore Codes are offered withi the followig areas: A) Qualificatio, Quality ad Safety Methodology B) Materials Techology C) Structures D) Systems E) Special Facilities F) Pipelies ad Risers G) Asset Operatio H) Marie Operatios J) Wid Turbies Amedmets ad Correctios This documet is valid util superseded by a ew revisio. Mior amedmets ad correctios will be published i a separate documet o the DNV web-site; ormally updated twice per year (April ad October). To access the web-site, select short-cut optios "Techology Services" ad "Offshore Rules ad Stadards" at The electroic web-versios of the DNV Offshore Codes will be regularly updated to iclude these amedmets ad correctios. Commets may be set by to rules@dv.com For subscriptio orders or iformatio about subscriptio terms, please use distributio@dv.com Comprehesive iformatio about DNV services, research ad publicatios ca be foud at or ca be obtaied from DNV, Veritasveie 1, NO-1322 Høvik, Norway; Tel , Fax Det Norske Veritas. All rights reserved. No part of this publicatio may be reproduced or trasmitted i ay form or by ay meas, icludig photocopyig ad recordig, without the prior writte coset of Det Norske Veritas. Computer Typesettig (FM+SGML) by Det Norske Veritas. Prited i Norway If ay perso suffers loss or damage which is proved to have bee caused by ay egliget act or omissio of Det Norske Veritas, the Det Norske Veritas shall pay compesatio to such perso for his proved direct loss or damage. However, the compesatio shall ot exceed a amout equal to te times the fee charged for the service i questio, provided that the maximum compesatio shall ever exceed USD 2 millio. I this provisio "Det Norske Veritas" shall mea the Foudatio Det Norske Veritas as well as all its subsidiaries, directors, officers, employees, agets ad ay other actig o behalf of Det Norske Veritas.

3 Itroductio Page 3 Itroductio This recommeded practice has bee developed i a joit idustry project which was carried out The project was broadly supported by the oil idustry ad rope makers; ad DNV values highly their cotributios, ad the cotributios from others, which made it possible to develop the recommeded practice. The damage assessmet method is based o detailed kowledge of the rope that has bee damaged. This iformatio shall be provided by the maufacturer of the rope, ad the techical documetatio shall be available whe the damage assessmet is performed. The rope maufacturer will provide data tables ad tables to fill i step by step durig the assessmet. The work is carried out with hads-o access to the rope with tesio removed. The recommeded practice does ot cover repair of the load bearig subropes of the rope. Hece, if a rope is deemed ot suitable for service, this cocers the rope i the damaged coditio. If a damaged rope is deemed suitable for further use, the the filter ad jacket must be repaired. The recommeded practice icludes field experiece gaied up to the time of publicatio. Stricter requiremets to the removal of rope jacket prior to assessmet have, therefore, bee icorporated.

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5 Page 5 CONTENTS 1. APPLICATION OF THE RECOMMENDED PRACTICE DEFINITIONS Terms used i this recommeded practice Notatio MANUFACTURER S REPORT Cotets of the Maufacturer s Report Descriptio of types of rope Maufacturig data to be used as basis for damage assessmet Damaged-Subrope Stregth Data INSPECTION Geeral Ispectio Close Ispectio Subrope Ispectio Damage Ispectio DAMAGE ASSESSMENT Levels of damage assessmet Level 1 Simplified damaged-stregth assessmet Method, level Level 2 Detailed damaged-stregth assessmet Method, level 2: Damage Ispectio Level 3 Damaged fatigue-life assessmet Method, level APP. A INPUT REQUIRED TO PERFORM DAMAGE ASSESSMENT... 13

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7 Page 7 1. Applicatio of the recommeded practice The purpose of this recommeded practice is to provide assessmet basis for the suitability of a polyester moorig rope to remai i service, after it has bee mechaically damaged by exteral objects. The recommeded practice is applicable to ay parallel-subrope type of rope. The iputs required to perform the ecessary calculatios are provided by the rope maufacturer. This iformatio is give i the Maufacturer s Report. The damage assessmet is based o the subrope-to-rope relatioship, sice the subrope is the primary buildig block of the rope. Subrope-to-rope assessmet is required sice the effect of damage is highly depedet o the damage distributio. This implies that for a give loss of area, the resultig rope stregth ad fatigue performace will vary depedig o the distributio of the damage. The result of the damage assessmet is a revised miimum breakig stregth MBS, deoted MBS DAMAGED. This (revised) MBS DAMAGED is used to determie if a damaged rope is suitable for temporary or prologed service, ad use of this guidelie shall provide documetatio for that decisio. Prologed service may be possible if the fatigue performace of the damaged rope is deemed satisfactory. 2. Defiitios 2.1 Terms used i this recommeded practice Rope: The moorig rope beig examied ad assessed for damage. The moorig rope is costituted by a assembly of subropes, which is held i place as a budle by a jacket ad termiated at each ed by spliced eyes. Subrope: A rope-like assembly of strads. Per defiitio, i this recommeded practice subropes are ot referred to as rope, but they are ideed ropes i their ow right. Strad: The priciple compoet of the subrope. A assembly of rope yars which are grouped to form the strad. The strads form a subrope by either a helical or braided arragemet. Rope yar: The largest yar compoet of the strad, made by twistig or budlig smaller yars together. Miimum breakig stregth: The miimum required breakig stregth of a rope or a subrope i the udamaged coditio. Ofte determied as the average break stregth mius two stadard deviatios of five break test results. Filter: A barrier towards igressio of foreig matter, which is applied to the rope betwee the jacket ad the load bearig subropes. Jacket: A o-load bearig exteral sleeve desiged to maitai the budle of subropes i a orgaized maer. Damaged rope: A rope with mechaical damage to oe or more subropes. Damaged subrope: A subrope with damage to oe or more of its strads. Maufacturer s Report: Data sheets cotaiig all iformatio about the particular rope, prepared for use as a resource ad referece for performig damage assessmet based o this guidelie. Rope Layout: A descriptio of how the subropes are idividually arraged i the budle, ad how they are spliced together. Damaged-Subrope Stregth Data: Test results provided i the Maufacturer s Report for selected sizes ad combiatios of strad damage withi a subrope. Stregth Ratio: The stregth of a damaged subrope (bs damaged ) divided by the average subrope stregth (). Highest desig load: The highest force occurrig i the rope as derived by the moorig-desig aalysis. Ultimate load: The failure load of a damaged rope. Fatigue Amplificatio Factor: The ratio betwee the average subrope stregth () ad the damaged stregth of a subrope (bs damaged ). This ratio represets the icrease of stresses locally i a subrope due to the damage i that subrope. 2.2 Notatio Table 2-1 presets the otatio used i this recommeded practice. Notatio pertaiig to the rope is i uppercase letters. Notatio pertaiig to the subrope is i lowercase letters. Table 2-1 Notatio i the damage assessmet MBS Miimum breakig stregth of the rope. AVS Average stregth of the rope from testig. MBS DAMAGED The recalculated miimum breakig stregth of the rope i the damaged coditio. mbs Miimum breakig stregth of the subrope. Average stregth of the subrope from testig. BS damaged, No.i The rope force at which subrope No. i will fail. bs damaged, No.i Break stregth of damaged subrope No. i. BS damaged, ext Rope force greater tha the highest desig load at which the ext subrope i the rope will fail. bs damaged, ext Break stregth of the ext subrope to fail, above highest desig load. bs damaged, ULTIMATE Break stregth of the subrope that fails at the ultimate load i the damaged rope. total Number of subropes i the rope. damaged, ubroke Number of damaged subropes ot yet broke. udamaged Number of udamaged subropes. affected Number of subropes either damaged or spliced i pair with a damaged subrope. k Fatigue amplificatio factor due to reduced cross sectio of a damaged subrope. ML The loadig of the udamaged rope as derived i the moorig-desig aalysis. ml damaged Corrected, amplified loadig i the critical strad (i the critical subrope), due to loss of other subropes ad reduced cross sectio of the strads i the critical subrope.

8 Page 8 3. Maufacturer s Report 3.1 Cotets of the Maufacturer s Report The rope maufacturer shall prepare a report for the particular rope delivered. This report shall cotai the ecessary ropespecific iformatio to perform the damage assessmet. The mai cotets are: 1) Damaged-Subrope Stregth Data. 2) Rope Layout. 3) Stregth data from rope qualificatio testig. The Maufacturer s Report may also cotai jacket removal ad repair istructios. Jacket Jacket Filter Figure 3-1 Priciple sketch of a parallel-subrope rope Subropes The Maufacturer s Report as defied herei should be a itegral part of the rope documetatio package. A detailed descriptio of the rope costructio ad the assembly shall be give i the Maufacturer s Report. It shall cotai key iformatio as outlied i sectios 3.3 ad Descriptio of types of rope The Maufacturer s Report shall cotai a detailed descriptio of the subropes which may be of various costructios, depedig o the choice of the maufacturer. Examples of possible subrope costructio types are: 3-strad helical. 4-strad helical. 8-strad braided. 12-strad braided. Six-aroud-oe helical. The maufacturer may vary the stregth of the rope i two ways: vary the stregth of the subropes vary the umber of subropes i the rope. The method of damage assessmet is the same for all parallelsubrope ropes, but a distictio is made for ropes where subropes are spliced to form a pair with aother subrope. I each pair, two subropes are coected at each spliced termiatio. If subropes are ot i pairs, each subrope forms a rope i its ow right, with a spliced eye each ed. If subropes are i pairs, each pair of subropes form a loop. The required iformatio is foud i the Maufacturer s Report. 3.3 Maufacturig data to be used as basis for damage assessmet The Rope Layout is used to assess the effect of subrope damage with respect to the rope. Key iformatio is: umber of subropes i the rope idetifyig marker system for the subropes i the rope, used to determie if ay damaged subrope forms a pair with aother damaged or itact subrope rope cross-sectio layout. A example Maufacturer s Report is give i Appedix A. Level 1 damage assessmet is based o the Rope Layout. (See Sec.5). This iformatio from the Maufacturer s Report is applied i coectio with the Subrope Ispectio. (See Sec.4.3) Strad lay legth Figure 3-2 Details of 3-strad helical subropes. S ad Z helix orietatios are idicated Z S Subrope lay legth Figure 3-3 Details of 8-strad braided subrope. S ad Z strad orietatios are foud i the same subrope 3.4 Damaged-Subrope Stregth Data The Damaged-Subrope Stregth Data describes the stregth of subropes with various stadard sizes of damage. Typical examples are: 25% damage to 1 strad of 3. 50% damage to 1 strad of 3. 50% damage to 2 strads of 3. 50% damage to 1 strad of 8. 50% damage to 1 of 4 S-strads, ad 1 of 4 Z-strads. The rope maufacturer provides the Damaged-Subrope Stregth Data i a table i the Maufacturer s Report. Level 2 damage ispectio is based o the level 1 assessmet ad the Damaged-Subrope Stregth Data. This iformatio is applied i coectio with the Damage Ispectio (of the subropes). (See Sec.5.)

9 Page 9 4. Ispectio There are four categories of rope ispectio defied: Carried out before damage assessmet, or durig service/operatio as part of regular ispectio: Geeral Ispectio. Close Ispectio. Carried out uder level 1 damage assessmet (see Sec.5): Subrope Ispectio. Carried out uder level 2 damage assessmet (see Sec.5): Damage Ispectio. 4.1 Geeral Ispectio The Geeral Ispectio is performed to survey the exterior of the rope for potetial areas of damage. Two meas exist to check for mechaical damage to the rope jacket: ROV survey of a istalled lie visual survey durig reelig ad/or istallatio. Mechaical damage to the jacket is a coditio to mechaical damage to the subropes which is ot related to the loadig of the rope. 4.2 Close Ispectio If a poit of potetial damage to the jacket has bee located, this area of the rope requires closer ispectio. Close Ispectio is carried out by ispectors with access to the rope legth i questio, with tesio removed from the rope. Hads-o approaches are the basis of this guidelie. This should however ot be costrued as a limitatio to the use of reliable ROV or future o-destructive techiques to assess the extet of damage to the jacket. Perform a close examiatio of the jacket. Look for ay severed jacket yars, ad record the extet of damage to the jacket. Take photographs. If the damage does ot peetrate the jacket, the the rope is ok. Jacket repair is ot required. If the damage peetrates the jacket, but ot the filter, the the rope is ok. Jacket repair may be required, depedig o the extet of damage to the jacket. For the examiatio of the filter, a blut fid or similar tool such as the hadle of a spoo may be used to force the over braidig aside to get the ecessary access view. Observe ay istructios provided by the maufacturer. If the filter is damaged, but ot peetrated, cosider whether a filter patch is eeded. If ot, the rope may be retured to prologed service immediately. If the damage peetrates the filter, the a Subrope Ispectio must be performed. 4.3 Subrope Ispectio Ope the jacket for a distace of approximately 0.6 metres (2 feet) to each side of the damage area. Follow the rope maufacturer s istructios, to prepare for the jacket repair. This procedure may well be carried out by a represetative of the maufacturer. If sufficiet subrope idetificatio is provided, together with documetatio of their exact arragemet, it may be possible to determie that subropes adjacet to a damaged subrope are itact ad preset without opeig the jacket aroud the etire circumferece. Otherwise observe below importat otice. Cout the umber of subropes i the damage area. Importat otice: Assessmet of extet of damage without sufficiet jacket removal to physically cout all subropes is highly ureliable. Verify the umber of subropes towards the Maufacturer s Report; ad make sure that all subropes have bee foud. If the umber of subropes is less tha what is stated i the Maufacturer s Report, the oe or more subropes have bee completely severed, ad pulled back ito the rope to become ivisible. Cout ad record the umber of damaged subropes. Record the idetifyig markers of the damaged subropes. If subropes are missig from the damage area (i.e. completely severed ad pulled back) the the idetifyig markers eed to be idetified for all subropes i order to distiguish which subrope(s) have severed. Verify this iformatio towards the Maufacturer s Report. If o subrope damage is foud, the rope may be retured to prologed service after repair of the filter ad jacket. 4.4 Damage Ispectio The objective of the Damage Ispectio is to quatify the stregth cotributio from the damaged subropes i the rope. For each damaged strad i each damaged subrope, the umber of itact rope yars is couted ad recorded, or alterative methods are applied as appropriate depedig o type of rope. (See Sec.5.6). 5. Damage Assessmet 5.1 Levels of damage assessmet There are three levels of damage assessmet defied i this recommeded practice: Level 1 is the simplest assessmet, cosiderig all damaged subropes as broke. Level 2 cosiders stregth cotributio from damaged subropes, without cosiderig the effect of damage o fatigue life. Level 3 icludes fatigue-life assessmets i the level 2 approach. 5.2 Level 1 Simplified damaged-stregth assessmet The level 1 damage assessmet is used if it is assumed that the udamaged subropes aloe have sufficiet stregth for the service of the rope; ad that the damaged subropes do ot cotribute to the stregth. Typical applicatios are oversized rope i MODU moorig, or rope with very limited damage. The level 1 assessmet is also

10 Page 10 suitable for a quick assessmet of the status of the rope, to determie if more detailed aalysis is required. 5.3 Method, level 1 Carry out the Geeral Ispectio. Carry out the Close Ispectio. Carry out the Subrope Ispectio. Refer to the Maufacturer s Report to fid out if ay damaged subrope is spliced to ay other subrope. If so, both subropes must be cosidered as affected. Cosider all affected subropes as broke. This applies oly to the level 1 approach. Calculate the damaged MBS of the rope by multiplyig the origial MBS with the ratio of umber of uaffected subropes to the total umber of subropes. This formula applies oly to the level 1 approach. If the damaged miimum breakig stregth is deemed isufficiet, discard the rope or proceed to the level 2 assessmet. If the damaged miimum breakig stregth is deemed sufficiet for the applicatio, the the rope may be retured to temporary service. Repair the filter ad jacket accordig to the maufacturer s istructios, or have the filter ad jacket repaired by the maufacturer. If the rope is cosidered for prologed service, the fatigue life should be reassessed accordig to level 3 based o the udamaged subropes. For the level 3 assessmet based o level 1, the fatigue amplificatio factor k = 1.00, sice oly udamaged subropes are cosidered to carry load. 5.4 Level 2 Detailed damaged-stregth assessmet The level 2 damage assessmet icludes the stregth of damaged subropes i the assessmet of the stregth of the damaged rope. It is assumed that the damage does ot affect fatigue life. If this assumptio is doubtful, the a level 3 assessmet should be performed after the level 2 assessmet. 5.5 Method, level 2: MBS DAMAGED = MBS uaffected Carry out the Subrope Ispectio. Refer to the Maufacturer s Report to fid out if ay damaged subrope is spliced to ay other subrope. Carry out Damage Ispectio as described i the followig. 5.6 Damage Ispectio Ispect each strad of each damaged subrope, ad idetify the damaged strads with a marker pe for trackig. Use differet colours to distiguish the damaged subropes, ad use the colours for referece whe performig the damage assessmet. total The combiatio of damage to strads for each subrope is the basis for this assessmet, ad ot loss of area. For example, if a subrope has 40% damage to oe strad ad there is break stregth data for 50% damage to oe strad, the that data should be selected. Examie each damaged subrope to assess the extet of damage. For each subrope, the actual combiatio of damage to strads is quatified to the earest higher subrope damage size, as foud i the Damaged-Subrope Stregth Data. Importat otice: If ecessary, special-purpose damaged subrope break tests ca be coducted for the exact damage foud i the critical subrope. This ispectio is best performed by coutig the umber of rope yars that are udamaged withi each damaged strad of the subrope. The total umber of rope yars per strad is foud i the Maufacturer s Report. The extet of damage may also be determied by visual judgmet of the strad area or other techiques foud to be practical. Refer to the Damaged-Subrope Stregth Data, ad list the subrope loads which will cause each of the damaged subropes to fail. Rak the damaged subropes, with the most severely damaged subrope as No. 1. The Maufacturer s Report provides empty tables to be used for damage recordig, determiatio of earest higher subrope damage size ad severity rakig. See Appedix A for example tables. The most severely damaged subrope is that of the lowest stregth. This might ot be the subrope with most total damage. Estimate the force i the rope at which subrope No. 1 will fail: BS bs = damaged, No.1 damaged, No.1 AVS The force i the rope for the first subrope failure is the Stregth Ratio for that subrope times the average stregth of the rope from prototype testig also give i the Maufacturer s Report. Refer to the Rope Layout give i the Maufacturer s Report, ad fid out if damaged subrope No. 1 is spliced to ay other subrope. If the subropes are idividually spliced, failure of subrope No. 1 will result i oe less load-carryig subrope. (See Figure A-2.) If subrope No. 1 forms a pair with aother subrope, failure of subrope No. 1 will result i two less load-carryig subropes. Both affected subropes must be cosidered as broke whe subrope No. 1 has failed. (See Figure A-3.) A itact (or less damaged) subrope that is spliced to form a pair with a damaged subrope is ot cosidered load carryig after failure of the (most) damaged subrope. Util the (most) damaged subrope fails, both are cosidered fully load bearig. Estimate the force i the rope at which subrope No. 2 will fail.

11 Page 11 BS damaged, No.2 bs = damaged, No.2 AVS damaged, ubroke The secod subrope failure load is the Stregth Ratio of that damaged subrope as foud i the Maufacturer s Report times the average stregth of the rope, multiplied by the ratio of umber of ubroke subropes after the previous failure to the total umber of subropes. Refer to the Rope Layout give i the Maufacturer s Report, ad fid out if damaged subrope No. 2 is spliced to ay other subrope. If the subropes are idividually spliced, failure of subrope No. 2 will cause the rope to cotai oe (additioally) less loadcarryig subrope. If subrope No. 2 formed a pair with aother subrope, both affected subropes must be cosidered as broke whe subrope No. 2 has failed. Cotiue the calculatio for the total umber of damaged subropes. List the calculated subrope-failure loads of the rope. Check if a subrope failure force is lower tha the previous. If it is lower, the subrope is expected to break mometarily upo the previous subrope break. If this is the case, the ultimate capacity of the damaged rope is most likely, but ot ecessarily, exceeded. Determie the ultimate load, i.e. the highest force to be attaied as already listed. (See example tables i Appedix A.) Calculate the damaged MBS of the rope. This will be the origial MBS, times the Stregth Ratio for the subrope that fails at ultimate load, times the ratio of umber of load-carryig subropes upo ultimate load, to the total umber of subropes. MBS bs = The umber of load carryig subropes at ultimate load is the umber of udamaged subropes + damaged subropes still carryig load at the attaimet of ultimate load. Evaluate if the damaged MBS is sufficiet. If ot, the rope should be take out of service. If the stregth is sufficiet, the rope may be put back for temporary service, pedig completio of the level 3 assessmet of fatigue. Repair the filter ad jacket accordig to the maufacturer s istructios, or have this carried out by the maufacturer. 5.7 Level 3 Damaged fatigue-life assessmet The level 3 damaged fatigue-life assessmet is carried out if there is a risk that the damaged subropes that survive the highest desig load might fail by fatigue. Importat otice: The level 3 assessmet is ot meat to be carried out i the field uless persoel authorized for fatiguelife assessmet ad judgmet of prologed use of a damaged rope is preset or available. I additio to the Damaged-Subrope Stregth Data ad the total + total + damaged, ULTIMATE damaged, ubroke udamaged DAMAGED udamaged MBS Rope Layout provided by the maufacturer, the level 3 assessmet requires the data o highest load that is likely to occur as give by the moorig-desig calculatios. The level 3 damage assessmet is most likely relevat i case of a highly utilized rope, or a rope with severe damage. The severity of damage is based o the umber of subropes affected, rather tha the extet of damage to each subrope. Severe damage is typically that more tha 15% of the subropes are affected by damage. A affected subrope is either damaged, or spliced to, a damaged subrope. Mior damage is typically that less tha 10% of the subropes are affected by damage. These values are give as examples; whether a actual damage is severe or mior will deped o the actual damaged rope. (Example: A twety-four-subrope rope has comprehesive damage to two of the subropes. If the subropes are spliced idividually, this damage would typically be mior. If the rope is spliced with the subropes i pairs, rope damage will typically be severe if the two damaged subropes are ot i the same pair, ad mior if they are i the same pair. If they are ot i the same pair, the four subropes of twety-four are affected.) 5.8 Method, level 3 Determie the highest desig load for the moorig leg cotaiig the damaged rope, by referrig to the moorigdesig calculatios. Carry out the level 2 assessmet. From the level 2 assessmet rakig table, determie how may affected subropes will fail whe the rope is tesioed to the highest desig load. Cosider those affected subropes to have broke. Cosider all other subropes, icludig damaged subropes, to be ubroke. Estimate the force i the rope that will cause the ext subrope to fail (above the highest desig load): BS damaged, ext bs = damaged, ext AVS damaged, ubroke For a certai damaged rope, it is possible to have for example oe damaged-subrope failure due to desig loads, ad two damaged subropes remaiig i service sice they will break at loads above the highest desig load. The fatigue assessmet shall be cocetrated to the most severely damaged remaiig subrope, or a itact subrope if all damaged subropes fail due to desig loads. The fatigue-life assessmet is focused to the ext subrope to fail, where the fatigue life is assessed for the strad that is most damaged. Due to the removed material i the damage zoe of a subrope, the yar stress will be higher i damaged subropes, ad highest i the most severely damaged strad. I for example a 3-strad subrope with 50% damage to oe strad, the yar stress will be the highest i the damaged strad, compared to the two other strads. Hece, the most damaged strad is the focus of the fatigue assessmet. Correct the forces i the moorig aalysis by multiplyig with the ratio of total umber of subropes to the umber of subropes ot yet broke. Refer to the Maufacturer s Report ad obtai the fatigue amplificatio factor for the most severely damaged subrope ot yet cosidered as broke by the highest desig load. total + udamaged

12 Page 12 The Fatigue Amplificatio Factor describes the icrease of stresses i the most severely damaged strad i a damaged subrope. It is equal to the ratio of average subrope stregth to damaged subrope stregth. k = bs damaged Multiply the corrected moorig loads by the fatigue amplificatio factor, to obtai the equivalet udamaged fatigue forces of the most damaged strad of the most severely damaged subrope, which will ot fail by desig loads. These calculatios are performed as follows: total mldamaged = ML k + damaged, ubroke udamaged where ML is the forces i the moorig desig aalysis for the rope, ad ml damaged is the corrected ad amplified forces as experieced by the critical strad. Verify that the amplified, corrected moorig loads are acceptable towards the appropriate fatigue-life desig curve. For a rope that has see prologed service already, the fatiguelife coditio at preset must also be take ito accout. If uacceptable, the damaged subrope i questio should be cosidered as broke. I this case, repeat the level 3 assessmet for the ext damaged subrope. If evetually all damaged subropes are expected to fail by fatigue, check the fatigue situatio of the uaffected subropes aloe. Whe this iterative process is completed, update the coclusio of the level 2 assessmet if the subrope to fail at ultimate load is expected to fail by fatigue. If the resultig damaged stregth or fatigue capacity is deemed isufficiet, the rope should be take out of service. If the resultig damaged stregth or fatigue capacity is deemed sufficiet, the filter ad jacket should be repaired, ad the rope may be put back for prologed service. Importat otice: The corrected, amplified fatigue loads are calculated for the ext subrope to fail. I the other (damaged or udamaged) subropes, the fatigue exposure is less severe. Due to the complex chages i iteral compliaces withi a damaged subrope, derivatio of fatigue amplificatio factors based o lost area of either strad, subrope or rope is ot recommeded, ad will be ambiguous. The ratio of average subrope stregth to damaged subrope stregth should be used.

13 Page 13 APPENDIX A INPUT REQUIRED TO PERFORM DAMAGE ASSESSMENT A.1 Example Maufacturer s Report This appedix shows typical cotets of the Maufacturer s Report, which shall provide the ecessary rope-specific iput to perform the damage assessmets. Sice the guidelie shall be applicable to ay parallel-subrope type of rope; it is the resposibility of the rope maufacturer to produce these data that shall be specific to every rope delivered. Hece, the guidelie is ot geeric to geeral types of rope, however whe experiece ad data have bee accumulated it will be likely that geeric iformatio ca be derived from the Maufacturer s Reports previously produced. Free legth Splices Eye loop Rope-specific iformatio: Table A-1 Rope-layout data Number of subropes i rope: Number of strads i subrope: Number of rope yars i strad: Splicig method: Subrope idetificatio: Table A-2 Udamaged-state data Average breakig stregth of rope: Miimum breakig stregth of rope: Average breakig stregth of subrope: 1 2 AVS MBS Eye loop Splices subropes Figure A-2 Priciple of rope assembly for idividually spliced subropes I the rope-layout data table it will be idicated that splicig method is either i pairs or idividual. If some subropes are spliced i pairs ad some subropes are spliced idividually i the same rope, more detailed idicatio of this will be give. It must be oted that if subropes are spliced i pairs, failure of oe subrope reders two subropes to be couted as broke. This is reflected whe the figures for damaged,ubroke + udamaged are etered i Table A-7 ad Table A-8, ad the associated calculatios are carried out. If a combiatio of idividual ad paired subrope splicig is used, this also must be reflected i the damage assessmet whe fillig i Tables A-7 ad A-8. A sketch of a rope that uses paired splicig is show i Figure A Figure A-1 Cross sectio of assembled rope, idicatig subrope arragemet ad id umbers Splices Free legth Splices Splices Splices Eye loop subropes ½ pairs Figure A-3 Paired splicig layout

14 Page 14 Table A-3 Example table for Damaged-Subrope Stregth Data No. of strads damaged Extet of damage to strad(s) [%] bs damaged Fatigue amplificatio factor k This is a example table for 3-strad helical subropes. If the subrope has four strads, the left-had colum will reflect that. If the rope is of a type that uses braided subropes, the orietatio (S or Z) of the damaged strads will also be listed together with the umber of damaged strads, damage sizes ad the effect o stregth ad fatigue amplificatio factor. Assessmet tables: Table A-4 is used to complete the subrope ispectio required for the level 1 damage assessmet, oly coutig the umber of damaged subropes. Table A-4 Subrope Ispectio recordig table Total umber of subropes foud: Number of itact subropes: Number of damaged subropes: Damaged-subrope idetities: I order to proceed with level 2 assessmet, perform the damage ispectio ad fill i Table A-5. Table A-5 Damaged-subrope recordig table Damage recordig Subrope idetity Strad No. 1 Strad No. 2 Strad No. 3 Itact rope yars Damage [%] Itact rope yars Damage [%] Itact rope yars Damage [%] Use Table A-5 to record the itact rope yars that ca be idetified i each strad of the damaged subropes. Calculate the % damage to each strad, based o the umber of rope yars i itact strads as give i Table A-1, the rope-layout data table. Whe the actual damage has bee quatified for each subrope, refer to Table A-3 ad determie for each damaged subrope the earest higher damage size that has bee tested. Eter this data i Table A-6 for each damaged subrope. Table A-6 Recordig table for earest higher damage sizes Nearest higher damage size [%] Subrope idetity Strad No. 1 Strad No. 2 Strad No. 3 bs damaged

15 Page 15 The proceed to the rakig table, deotig the most severely damaged subrope (i.e. that of lowest stregth) as damaged subrope No. 1. The damaged stregth ratio ad fatigue amplificatio factor is foud i Table A-3, the damaged-subrope stregth table. Table A-7 Damaged-subrope rakig table bs damaged Damaged subrope No. Subrope idetity k damaged,ubroke + udamaged etc. The completed Table A-7 shows the sequece of subrope failures that is utilized i the estimatio of damaged stregth. Table A-7 also shows the umber of subropes that carry load upo the ext subrope failure. For level 2 assessmet, complete the predictio table, Table A- 8, ad estimate the damaged-state ultimate load. Table A-8 Rope stregth predictio table Subrope No. bs damaged bs damaged, No. i damaged, ubroke + udamaged damaged,ubroke + udamaged AVS = total BS damaged, No. i [kn] etc. The highest value for BS damaged, No. i will be the predicted ultimate load, deoted BS damaged, ultimate. Calculate the damaged-state miimum breakig stregth accordig to the followig formula: MBS bs = Proceed to the level 3 assessmet as required. total + damaged, ULTIMATE damaged, ubroke udamaged DAMAGED MBS

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