Wire Rope - Ushapedia
Contents
1. TABLE 11 CONVERSION FACTORS Reproduction is not allowed unless specifically agreed 7 usha martin APPENDIX G MINIMUM ROPE INFORMATION When providing an enquiry or a purchase order at least the following information should be supplied 1 2 3 4 5 6 7 8 10 11 12 13 14 reference standard i e EN 12385 4 quantity and length nominal diameter rope class or construction core type rope grade wire finish lay direction and type single layer ropes are normally manufactured right hand ordinary lay unless otherwise stated by the purchaser 27 preformation outer strands of single layer and parallel closed ropes are normally preformed during manufacture The purchaser should specify any particular preformation requirements lubrication at least the strands are lubricated during manufacture The purchaser should specify any particular lubrication requirements type of inspection document refer EN 12385 1 any particular marking requirements any particular packaging requirements required minimum breaking force This document is property of Usha Martin Italia Reproduction is not allowed unless specifically agreed EJ 7 usha martin APPENDIX REFERENCE DOCUMENTS The following list indicates some of the most relevant documents about wire ropes definitions use maintenance and inspection e EN 12385 1 2009 Steel wire ropes Safety Part 1 General requirements e EN 12385 2 202. nennen eene 4 Rope diameter and measurement 5 Rope lay measurement and selection 6 Benefits of compacted strands nennen 7 Fleet angle and plastic impregnated core ropes 8 Rotational characteristics and use of swivel 9 Reel receipt and storage nennen nene nnne nnns 10 POPOD Rol ect p 11 Serving and cutting siria iron daa re eR dS 12 oe NPS 13 Inspection of grooves and sheaves nnns 14 Rope installation and training 15 Lifting operations inni 16 Rope FUNN 17 Guidelines for rope inspection nennen 18 Discard criteria for visible broken wires 19 Discard criteria for diameter decrease deformation and corrosion 20 Health and safety information enne 21 Appendix Definitions Lee 22 Appendix C Examples of strand constructions 24 Appendix D Examples of rope constructions 25 Appendix E Fleet angle during spooling 26 Appendix F Quick calculator Me 28 Appendix G Minimum rope information
3. Baku URotterdam Vietnam YrHoshiarpur Shanghai o Jakarta 0 Johannesburg dr Dubai Australia Singapore c tr Silvassa gap Ranchi Bangkok vr Jamshedpur Manufacturing F acilities O Distribution Centers DI Sales Office EMMC Centers PI fj usha martin Usha Martin Italia s r l Via Nikolajewka 1 25062 Concesio BS ITALY info ushamartin it Edition 1 October 2013
4. gt Crossover and max fleet angle Block and head sheaves e Compensating sheaves FIGURE 31 AREAS REQUIRING DETAILED INSPECTION This document is property of Usha Martin Italia Reproduction is not allowed unless specifically agreed 7 usha martin DISCARD CRITERIA FOR VISIBLE BROKEN WIRES Rope conditions have to be clearly assessed by a competent person based on discard criteria provided by regulations and internal procedures Discard criteria depends on the nature occurrence and location of broken wires and on the rope construction and are based on number of visible broken wires diameter variation corrosion and distortion or a combination of all these factors Number of visible broken wires takes in account only the breaks due to regular use that indicate fatigue pile up and approaching of end of rope safe life therefore breaks due to improper handling may not be considered in this count if not affecting safety conditions Breaks protruding from the rope can be removed if there is the risk that they generate further damage to the equipment or to the rope itself FIGURE 32 CROWN AND VALLEY BREAKS DUE TO FATIGUE If groups of broken wires are found in a section of rope which do not spool on and off the drum and breaks are concentrated in adjacent strands it might be necessary to discard the rope It shall be discarded as well if two or more wire breaks are found at a termination or concentrated in th
5. 29 Appendix H Reference documents 30 NP AP MV AP OCCU EE et 31 This document is property of Usha Martin Italia Reproduction is not allowed unless specifically agreed usha martin PREFACE ABOUT ROPE USE A wire rope can be simply considered as an assembly of several strands laid helically in different possible arrangements in order to bear axial loads To be fit for purpose it must also ensure other features like resistance to side loads flexibility handling and stability This definition however does not cover completely the implications of correct rope design manufacturing use and inspection as the real mandatory requirement must be in any case safety compliance which allows adequate working conditions for men and environment To ensure high quality standards our Company has settled up a complete process which includes custom design software state of the art manufacturing equipment and skilled personnel with proven expertise Rope integrity management should always be operated by properly trained personnel who should always refer to general regulations specific customer standards local legislation and internal guidance The content of this document is a brief abstract of rope characteristics and recommendations for rope use and it is not intended to be all inclusive specific matters can be followed with special care to customer needs by our technical departments This document is property of Usha Ma
6. Fe min and the specified minimum breaking force Fmin of the rope as determined from the ropemaker s design measured total spinning loss factor km the ratio between the measured breaking force Fm of the rope and the measured aggregate breaking force of the rope before rope making COATING finish and quality of coating the condition of the surface finish of the wire e g uncoated bright zinc coated zinc alloy coated or other protective coating and the class of coating e g class B zinc coating defined by the minimum mass of coating and the adherence of the coating to the steel below mass of coating the mass of coating obtained by a prescribed method per unit of surface area of the uncoated wire expressed in g m CORE core central element of a round rope around which are laid helically the strands of a stranded rope or the unit ropes of a cable laid rope fibre core FC core made from either natural fibres NFC or synthetic fibres SFC NOTE Fibre cores are normally produced in the sequence fibres to yarns yarns to strands and strands to rope steel core WC core made from steel wires arranged as a wire strand WSC or as an independent wire rope IWRC NOTE The steel core and or its outer strands can also be covered with either fibre or solid polymer solid polymer core SPC core consisting of a solid polymer material having a round shape or a round shape with grooves It may also contain an internal element o
7. 4 39 4 71 4 85 6 5 16 5 60 5 80 8 6 60 7 32 7 65 10 7 91 8 98 9 47 12 9 11 10 6 11 3 14 10 2 12 1 13 0 16 11 2 13 6 14 7 18 12 2 15 0 16 4 20 13 0 16 4 18 1 This document is property of Usha Martin Italia Reproduction is not allowed unless specifically agreed TABLE 3 EXAMPLE OF LEAD LINE FACTORS 7 usha martin ROPE RELUBRICATION The main purpose of lubrication is to maintain rope performance in use and protect it against corrosion which can determine rope discard when reaching a high severity rating Corrosion affects not only the residual breaking force but also wire ductility and mechanical characteristics therefore it should be carefully considered when inspecting a rope FIGURE 29 HEAVILY CORRODED ROPE Good quality lubricants are characterized by high adherence to steel in order to resist during the passage over the reeving light color not to obstruct possible rope damages detection and high compatibility with other products Drop point has to be high enough to tolerate rope storage and operating in warm environment but with a safety borderline to denote rope overheating during use Since steel can suffer permanent deterioration if subjected to high temperature for extended periods a good temperature limitation and consequent drop point is approximately 80 C Unless unexpected events the protection provided by the original manufacturing lubricant is enough to prevent rope corrosion during shipment storage and
8. be properly trained and have all the necessary equipment and operating procedures to perform their job safely Steel wire rope is a composite material containing different materials which can be identified based on the delivery note invoice or certificate The main component of steel wire ropes covered by the various parts of EN 12385 is carbon steel which may be galvanized or coated with zinc aluminium alloy Other components can be the fibre core the lubricant and possible plastic filling or covering Ropes produced from carbon galvanizing coated or stainless steel wires in the as supplied condition are not considered a health hazard However during any subsequent processing such as cutting welding grinding and cleaning dust and fumes may be produced which contain elements that may affect the health of exposed workers Fibre cores are composed by synthetic or natural fibres and do not present a health hazard when handled except in the unlikely case that the core may have decomposed into a dust which may be inhaled Also the concentration of toxic fumes from the cores generated during cutting will be almost negligible compared with the products generated by wire and lubricant Same risk of toxic fumes inhalation applies to plastic filling or covering The lubricants used in the manufacture of steel wire ropes normally present minimal hazard to the user who should anyway take reasonable care to minimize skin and eye contact and also avoid
9. breathing their vapours and mists Lubricants consist essentially of mixtures of oils waxes bitumen resins petroleum jelly gelling agents and fillers with minor concentrations of corrosion inhibitors oxidation stabilizers and tackiness additives and they are typically solid at ambient temperature To avoid the possibility of skin disorders repeated or prolonged contact with mineral or synthetic hydrocarbons should be avoided and workers should always wear protective clothing and gloves General and local exhaust ventilation should be used to keep airborne dust or fumes below established occupational exposure standards and operators should wear approved dust and fume respirators if these values are exceeded Protective equipment should be worn during operations creating eye hazards as well as gloves and other protective equipment when required A welding hood should be worn when welding or burning In the solid state steel components of the rope present no fire or explosion hazard The organic elements present like lubricants natural and synthetic fibres and other natural or synthetic filling and covering materials are capable of supporting fire Ropes and components must be disposed of in accordance with local Regulations This document is property of Usha Martin Italia Reproduction is not allowed unless specifically agreed HJ 7 usha martin APPENDIX A DEFINITIONS BREAKING FORCE minimum breaking force Fmin specified v
10. compacting process such as drawing rolling or swaging whereby the metallic cross sectional area of the wires remains unaltered whereas the shape of the wires and the dimensions of the strand are modified Seale parallel lay strand construction with the same number of wires in both layers Warrington parallel lay strand construction having an outer layer containing alternately large and small wires and twice the number of wires as the inner layer Filler parallel lay strand construction having an outer layer containing twice the number of wires than the inner layer with filler wires laid in the interstices between the layers WIRE outer wires all wires positioned in the outer layer of a spiral rope or in the outer layer of wires in the outer strands of a stranded rope inner wires all wires of intermediate layers positioned between the centre wire and outer layer of wires in a spiral rope or all other wires except centre filler core and outer wires in a stranded rope filler wires wires used in filler constructions to fill up the interstices between wire layers centre wires wires positioned either at the centre of a spiral rope or the centres of strands of a stranded rope core wires all wires of the core of a stranded rope load bearing wires those wires in a rope which are regarded as contributing towards the breaking force of the rope serving wire or strand single wire or strand used for making a close wound helical serving to ret
11. depends on rope construction Some typical values for crane applications are shown in the following table and are determined based on uniform stress distribution of rope strands and individual wires Other values can be found on specific regulations ROPE DIA d gt Construction Suggested D d ratio 6 x 46 8 x 36 18 19x19 35x7 6x41 8x 25 20 6x36 23 Sx19 6x25 6x31 26 19x7 6x19 34 TABLE 2 EXAMPLES OF RECOMMENDED BENDING RATIOS FOR CRANES SHEAVE DIA D This document is property of Usha Martin Italia Reproduction is not allowed unless specifically agreed M usha martin ROPE INSTALLATION AND TRAINING Rope spooling and installation should be carried out in accordance with a detailed plan issued by the user of the rope to prevent safety hazards and early rope damage The installation tension should be at least the highest value between 2 of the rope MBF or 10 of rope SWL This tension can be obtained directly using the spooling device or later during training stage depending on rope size and equipment availability Standard rope reels are designed for transportation and storage therefore they can bear a limited amount of pulling tension which is approximately 3 times the reel diameter for steel reels 0 5 times the reel diameter for wood reels e g 1 5 meter steel reel can bear up to 4 5 tons 1 5 meter wood reel can bear un to 0 75 tons up to a maximum of 10 tons using four spindles If higher tens
12. first period of use Lubricant conditions must be periodically checked depending on rope working type and environmental conditions Before relubrication rope must be cleaned to remove scales moisture and other contaminants Lubrication must be carried out on dry and clean rope using a lubricant compatible with the original one and whose amount is not excessive as this would make difficult to inspect the rope and could lead to accumulation of debris which could generate abrasions Some typical lubrication modes are shown in the following figure re e PRESSURE LUBRICATOR CONTINUOUS BATH SPRAY NOZZLE lt B B 5 5 5 5 I Ut 7 17111111111111111111111111 POURING SWABBING PAINTING FIGURE 30 TYPICAL LUBRICATION MODES This document is property of Usha Martin Italia Reproduction is not allowed unless specifically agreed 7 usha martin GUIDELINES FOR ROPE INSPECTION Wire ropes must be periodically inspected following regulations e g 1504309 and internal procedures to assess rope deterioration due to regular use or unexpected events and to ensure safe working conditions Inspections can be carried out with the aid of visual or magnetic devices in this case it is recommended to perform an initial inspection before rope use to have a baseline for future comparisons Each rope shall be inspected along its entire length or at the discretion of the competent person along the working length plus a
13. 08 Steel wire ropes Safety Part 2 Definitions designation and classification e EN 12385 3 2008 Steel wire ropes Safety Part 3 Information for use and maintenance e EN 12385 4 2008 Steel wire ropes Safety Part 4 Stranded ropes for general lifting applications e EN 13411 3 2011 Terminations for steel wire ropes Safety Part 3 ferrules and ferrule securing e EN 13411 4 2011 Terminations for steel wire ropes Safety Part 4 metal and resin socketing e EN 13411 5 2011 Terminations for steel wire ropes Safety Part 5 U bolt wire rope grips e EN 13411 6 2011 Terminations for steel wire ropes Safety Part 6 Asymmetric wedge socket e EN 13411 7 2011 Terminations for steel wire ropes Safety Part 7 Symmetric wedge socket e EN12927 Part 8 Magnetic rope testing e 50 17558 2006 Steel wire ropes Socketing procedures Molten metal and resin socketing e 50 4309 2010 Cranes Wire ropes Care and maintenance inspection and discard e 171 Crane specification document e M179 Guidance on the use of cable laid slings and grommets e IMCA M187 Guidelines for lifting operations e IMCA M194 Wire rope integrity management for vessels in the offshore industry e IMCAM197 Guidance on non destructive examination NDE by means of magnetic rope testing e API 9A ISO 10425 2003 Steel wire ropes for the petroleum and natural gas industries Minimum requirements
14. AND CUTTING During manufacturing process the strands can be preformed in order get a helical profile just before closing and improve rope stability and handling Similar purpose can be achieved through postforming which consists of the passage of the rope through a series of rollers With the exception of very specific applications preforming and postforming level must be such to stabilize the rope without reaching extreme levels as this would make the rope very faint during use Therefore unless the rope has been subjected to complete preforming it will have the tendency to unlay when cut For this reason serving shall be applied before rope cutting to keep strands in position and it has to be performed carefully as its failure may cause injuries or rope permanent damages Serving must be also performed before socketing and in this case it has to allow socket medium penetration between the rope and the socket bore The material shall be tinned or galvanized soft wire or strand for zinc zinc alloy coated wire ropes and bright tinned or galvanized soft wire or strand for bright wire ropes Wire diameter shall be such to firmly hold the strands and particularly in case of large size ropes seven wires strands can be used as an alternative to single wires Service length should be at least equal to two rope diameters see figure For preformed ropes one serving is typically enough while for not preformed ropes rotation resistant and paralle
15. MPREGNATED CORE ROPES Rope routing must be carefully considered to prevent early damage one of the most critical factors is the presence of deflection i e fleet angles between two sheaves or from the drum to the spooler c ib CENTRE LINE ERI LL __ SHEAVE ANGLE OF FLEET CENTRE LINE OF REEL FIGURE 11 FLEET ANGLE DURING SPOOLING AND ROPE ROLLING When fleet exists the rope is induced to roll and slide into the groove causing shortening and increasing of the lay length and possible permanent distortion of the rope structure like birdcage or core protrusion FIGURE 12 BIRDCAGE DEFORMATION Fleet angle should never exceed 2 it can be increased up to 4 with the adoption of plastic impregnated core ropes In this type of ropes plastic is applied to the core after its closing and is lightly heated and softened before final closing in order to create a connection between outer strands and core strands Plastic layer must not work as a cushion see left sketch but must ensure radial stiffness and diameter stability and therefore maintain the steel over steel contact between the strands see right sketch FIGURE 13 CUSHION LAYER VERSUS PLASTIC IMPREGNATED CORE This document is property of Usha Martin Italia Reproduction is not allowed unless specifically agreed f usha martin ROTATIONAL CHARACTERISTICS AND USE OF SWIVEL Being composed by helically laid elements each rope has the natura
16. VVIRE ROPE USER MANUAL 7 AN COMPANY PROFILE BRUNTON SHAW AND USHA MARTIN ITALIA USHA MARTIN GROUP COMPANIES Brunton Shaw UK is a successful manufacturer of high quality wire ropes for a wide range of applications which effectively combines more than 100 years of experience and tradition with an up to the minute range of products and a customer service package ideal for the modern market place 22 Usha Martin Group started in 1961 in Ranchi as a wire rope manufacturing company today is a USD 1 billion conglomerate with a global presence With continuous growth in both the domestic and international markets Usha Martin has emerged as India s largest and the world s second largest steel wire rope manufacturer ve ET 2295848 10000026 02096020 lt On Ou SOG lt CY NRS in 997 SG 05100 ANG OR 227 3 29 OG 2 Usha Martin Italia SpA is the last born of the Group It has been settled in January 2013 to support all Usha subsidiaries incorporating a highly qualified engineering office focused to computer aided rope design and application engineering and a specialized laboratory for rope inspection and R amp D activities This document is property of Usha Martin Italia Reproduction is not allowed unless specifically agreed f usha martin LIST OF TOPICS Preface about rope use
17. ain the elements of a rope in their assembled position This document is property of Usha Martin Italia Reproduction is not allowed unless specifically agreed E usha martin Single lay 19 Seale 19 Seale compacted 7 1 6 19S 1 9 9 K19S 1 9 9 25 Filler 26 Warrington Seale compacted 29 Filler 25F 1 6 6F 12 K26WS 1 5 5 5 10 29F 1 7 7F 14 31 Warrington Seale compacted 36 Warrington Seale 41 Warrington Seale compacted K31WS 1 6 6 6 12 36WS 1 7 7 7 14 K41WS 1 8 8 8 16 usha martin 6xK7 FC 6xK36WS IWRC 6xK36WS PWRC 8xK26WS FC 8 195 IWRC 10xK19S IWRC CL LE La hal ar LITE TP p M m LL E M Fpa dau A 35xK7 35xK19 57xK7 7 usha martin APPENDIX E FLEET ANGLE DURING SPOOLING Excessive deflection angles during rope use should be carefully considered to avoid rope permanent damage The following tables show the recommended green areas borderline yellow areas and not recommended red areas fleet angles for different drum widths W and spooling distances L 2 FIGURE 35 SPOOLING ARRANGEMENT Fleet angle a deg Hoist ropes Width Distance m TABLE 7 RECOMMENDED RANGE OF USE FLEET ANGLES FOR NOT NON ROTATING ROPES This document is property of Usha Martin Italia Reproduction is not allowed unless specifically agreed
18. alue in kN below which the measured breaking force Fm is not allowed to fall in a prescribed breaking force test and normally obtained by calculation from the product of the square of the nominal diameter d the rope grade Rr and the breaking force factor K minimum breaking force factor K an empirical factor used in the determination of minimum breaking force of a rope and obtained from the product of fill factor f for the rope class or construction spinning loss factor k for the rope class or construction and the constant 4 calculated minimum breaking force Fc min value of minimum breaking force based on the nominal wire sizes wire tensile strength grades and spinning loss factor for the rope class or construction as given in the manufacturer s rope design minimum aggregate breaking force Fe min specified value in kN below which the measured aggregate breaking force is not allowed to fall in a prescribed test and normally obtained by calculation from the product of the square of the rope diameter d the metallic cross sectional area factor C and the rope grade Rr measured aggregate breaking force Fe m the sum of the measured breaking forces of all the individual wires taken from the rope spinning loss factor k the ratio between either the calculated minimum aggregate breaking force Fe c min and the calculated minimum breaking force Fc min of the rope or the specified minimum aggregate breaking force
19. and terms of acceptance e API RP 9B 2005 American Petroleum Institute recommended practice for application care and use of wire rope for oilfield services e Wire rope technical board Wire rope user s manual 4th edition This document is property of Usha Martin Italia Reproduction is not allowed unless specifically agreed VARUNA PROJECT In order to deal with the new challenges given by industrial The location of the plant achieves the best compromise and offshore heavy lifting applications Usha Martin group between logistic and expertise only 60 miles to the sea has opened Varuna project which is leading to the built without resigning the skills of Brunton Shaw people up of a brand new manufacturing facility All rope design will be analysed and fine tuned by Usha Martin The new facility is currently under construction in Worksop Italia in order to meet the required product specifications UK and will accommodate an efficient production line reliability and production efficiency including two dedicated stranders and a state of the art Varuna products will be focused on the most typical rope closer constructions and size to Supply customers the right The new machines will be capable to produce large size product in swift delivery ropes with six strands multistrand and non rotating construction up to 300ton weight Sheffield UK 0 Glasgow UK Aberdeen UK Tr Hottinghamshire UK tr O Houston i 9 Norway
20. aps and uniform rope arrangement also in the cross over zone and up to the last layers which will reduce the risk of crushing cut in or early formation of broken wires Training is also essential to stabilize rope dimensions and to optimize rope lifetime and performance It is performed by lifting an adequate load for at least three times using the full rope length excluding the safety wraps which must always remain on the drum the load automatically generates proper backtension diameter stabilization and torque factor reduction FIGURE 27 CROSSOVER AREA This document is property of Usha Martin Italia Reproduction is not allowed unless specifically agreed f usha martin LIFTING OPERATIONS Applicable regulations give indications to ensure that lifting equipment is safe when new that it is used safely and that it remains safe for use Equipment and accessories are marked with their own safety working loads and must never be used out of the prescribed interval They should always be thoroughly examined according to examinations schemes and timing as well as before first use when moved to different locations in respect to the original one and each time unexpected events which may affect safety occur Similar indications apply to wire ropes who should always be handled maintained and inspected by competent persons using proper procedures see also chapters related to wire rope inspection When bent over stationary pins or
21. below Slings must have an adequate length to avoid flange ends overstress during reel lifting The rope should be checked to verify that it is not damaged when unloaded and transported to storage site and should not come into contact with parts of the lifting devices like hooks and forks Some recommendations for rope handling are indicated on specific labels applied on the reels see figure with a detail of EWRIS label FIGURE 17 ROPE HANDLING RECOMMENDATIONS Storage conditions are essential to prevent rope damage it should be avoided to keep the rope in very warm or humid environment as this could break down the effectiveness of native lubrication and accelerate the deterioration process If lubricant has the tendency to drain due to high temperature the reel should be periodically rotated to maintain a homogeneous distribution The rope should not be stored in places which could be affected by chemical agents corrosive matters or accidental damages and if stored outside the reel should be positioned in order to avoid direct contact with the ground and covered with waterproof material The rope marking should be clearly detectable and readable in order to safely and quickly identify the reel AMA GROUND CLEARANCE FIGURE 18 REEL STORAGE This document is property of Usha Martin Italia Reproduction is not allowed unless specifically agreed 7 usha martin ROPE PAY OUT Ropes can be supplied on coils or r
22. duction is not allowed unless specifically agreed 7 usha martin BENEFITS OF COMPACTED STRANDS Ropes for special applications and heavy lifting activities require a high load efficiency and breaking load which cannot be achieved using traditional round strands For this reason these ropes are typically composed by compacted strands whose compacting level can be designed and modulated depending on specific requirements Compacted strands are obtained by the passage through a die or a series of rollers applied on the strander machine just after the closing point as shown in the figure FIGURE 7 COMPACTING PROCESS THROUGH ROLLERS OR DIE FIGURE 8 ROUND STRAND LIGHT AND HIGH COMPACTING LEVEL FIGURE 9 ROUND STRAND VERSUS COMPACTED STRAND The main benefit of compacted strands adoption is the increase of metallic area in respect to round strands which allows to get higher breaking force This process also gives higher cooperation level to the individual wires homogeneous and stable strand diameter resistance to side pressure wear and abrasion Finally smoother contact surface between the strands and rounder profile gives better spooling performance and resistance to crushing LINE CONTACT SURFACE CONTACT FIGURE 10 CONTACT SURFACES FOR A NON COMPACTED AND A COMPACTED ROPE This document is property of Usha Martin Italia Reproduction is not allowed unless specifically agreed 7 usha martin FLEET ANGLE AND PLASTIC I
23. due to resin loss of volume helps to verify the proper wires distribution into the cone and does not need to be covered or removed This document is property of Usha Martin Italia Reproduction is not allowed unless specifically agreed f usha martin INSPECTION OF GROOVES AND SHEAVES Before installing the new rope the condition and dimensions of interface parts like drums sheaves and rope guards should be checked to verify that they are within the operating limits as specified by the original equipment manufacturer The groove diameter which can vary from 5 to 10 above the nominal rope diameter should be checked using a sheave gauge see figure Sheaves should also be checked to ensure that they are free to rotate FIGURE 24 GROOVES INSPECTION CORRECT SIZE NARROW AND LARGE GROOVE Grooves material and hardness is also important for good system performance the typical recommendation is to use hardened steel minimum 300HB which ensures good pressure resistance between the rope and the sheave When grooves become excessively worn they can be re machined if sufficient wall thickness will remain in the underlying material after the machining has been carried out Improper groove finishing can generate irregular rope routing and derailing over the sheave see figure FIGURE 25 FLATTENED PORTION DUE TO ROPE DERAILING The recommended bending ratio D d e g ratio between diameter of the component and rope nominal diameter
24. e socket Wire shall not be straightened when forming the brush as this would reduce the efficiency of the socketing media NN x i Y N t b 100 FIGURE 22 SOCKET BRUSH D The wires shall be evenly distributed around the circumference within the socket basket and the area where the enters the bore of the socket shall be sealed with material that prevents leakage of resin H and that shall be removed after socketing Before starting the operation c Re 0 9 the socket must be aligned with the rope axis The operator shall follow the resin manufacturer s instructions resin d system packages or kits shall not be sub divided or used after EE CONTE the expiry date indicated on the container or out the prescribed AND CONE DIMENSIONS temperature range The socket shall be filled from a single pour until the basket is full the approximate resincontent in cc for a standard spelter socket can be calculated using the formula in the sketch cone dimensions are in cm During the pouring and topping up operation and early stages of gelling it is essential that possible leaks are identified and stopped as such leaks may generate cavities near the neck of the brush The resin mixture shall be allowed to harden after gelling and the socket shall not be moved until the resin has hardened Some resins contain a coloring component which turns to blue during gelling Wire protruding after hardening
25. e valleys in a rope lay length as this could indicate the beginning of fatigue phenomenon If breaks occur randomly in rope sections running through sheaves spooled on and off a single layer drum or on crossover points of a multilayer drum the maximum amount is determined by specific regulations e g ISO 4309 Some examples of maximum allowed breaks for different rope use and constructions are shown in the following table Rope Number of visible broken outer wires construction On steel sheaves or single layer drum dini On multi layer drum Over 6d Over 30d Over 6d Over 30d Over 6d Over 30d 6 x 19 3 6 2 3 6 12 6x25 8x19 5 10 2 5 10 20 6x26 8x25 6 13 3 6 12 26 6x36 8x26 9 18 4 9 18 36 35x7 3 5 3 5 5 10 TABLE 4 MAXIMUM NUMBER OF VISIBLE BROKEN WIRES FOR TYPICAL ROPE CONSTRUCTIONS The numbers depend on the assumption that outer wire breaks correspond to a certain number of inner wire breaks Typically the number of inner broken wires due to use of a Lang lay rope is higher than the number of outer broken wires therefore damage detection is harder and the number of outer allowed breaks must be low On the other hand in ordinary lay ropes more breaks occur on the outer surface therefore they are more detectable and the allowed number is higher than the Lang lay value For non rotating ropes this difference is not remarkable due to their geometrical structure therefore there is no distinct
26. eels depending on size and customer requirements If the rope is supplied on a coil it should be placed on the ground and rolled out straight avoiding contamination with dust grit moisture or other harmful material The rope should never be pulled away from a stationary coil as this will induce turns into the rope and form kinks see figure FIGURE 19 ROPE KINK AND ASSOCIATED DEFORMATION If the coil is too large to be physically handled it may need to be placed on a turntable to pay it out as the end of the rope is pulled away from the coil If the rope is supplied on a reel a shaft of adequate strength should be passed through the reel bore and the reel should be placed in a suitable stand which allows it to rotate and be braked to avoid overrun during installation If a loop forms in the rope it should not be allowed to tighten to form a kink The reel stand should be mounted in a way that avoids reverse bend during reeving for a drum with an underwind rope take the rope off the bottom of the supply reel Underwind is also preferable in respect to overwind as it gives higher stability to the stand and less risk of overturn When releasing the outboard end of the rope from the supply reel or coil this should be done in a controlled manner De fa 6 FIGURE 20 RECOMMENDATIONS FOR ROPE PAY OUT This document is property of Usha Martin Italia Reproduction is not allowed unless specifically agreed 7 usha martin SERVING
27. f usha martin Fleet angle a deg Hoist ropes with plastic Width m Distance m 10 13 20 25 30 1 0 1 1 1 2 1 3 1 4 1 5 1 6 1 7 1 8 1 9 2 0 2 1 2 2 2 3 2 4 2 5 2 6 2 7 2 8 2 9 3 0 35 40 45 50 TABLE 8 RECOMMENDED RANGE OF USE FLEET ANGLES FOR NOT NON ROTATING ROPES WITH PLASTIC IMPREGNATED CORE Fleet angle a deg Rotation resistant ropes Width m Distance m 1 0 1 1 1 2 1 3 1 4 1 5 1 6 1 7 1 8 1 9 2 0 2 1 2 2 2 3 2 4 2 5 2 6 2 7 2 8 2 9 3 0 TABLE 9 RECOMMENDED RANGE OF USE FLEET ANGLES FOR NON ROTATING ROPES This document is property of Usha Martin Italia Reproduction is not allowed unless specifically agreed EJ T usha martin APPENDIX F QUICK CALCULATOR Quick calculation for general purpose evaluations or for preliminary design feasibility can be made using the following formulas and tables which provide a set of relevant nominal values MBF kN Ked Mass kg m kmed Metallic area A mm 0 785 f d d nominal diameter mm A
28. f wire s or fibre CROSS SECTIONAL AREA AND MASS fill factor f the ratio between the sum of the nominal metallic cross sectional areas of all the wires in the rope and the circumscribed area of the rope based on its nominal diameter nominal metallic cross sectional area factor C factor derived from fill factor and used in the calculation to determine the nominal metallic cross sectional area of a rope NOTE This can be expressed as C f e r 4 nominal metallic cross sectional area A the product of the nominal metallic cross sectional area factor C and the square of the nominal rope diameter rope length mass factor W that factor which takes into account the mass of core and lubricant as well as the metallic elements nominal rope length mass M product of the length mass factor and the square of the nominal diameter DIMENSIONS dimension of round wire or strand the diameter of the perpendicular cross section of the wire or strand dimension of round rope that diameter which circumscribes the rope cross section outer wire factor a factor used in the calculation of the approximate diameter of the outer wires of the outer strand layer outer wire diameter 6a the value derived from the product of the outer wire factor and the nominal rope diameter GRADE AND TENSILE STRENGTH rope grade Rr a level of requirement of breaking force which is designated by a number e g 1770 1960 NOTE It does not imply that the actual tens
29. ile strength grades of the wires in the rope are necessarily of this grade wire tensile strength grade R a level of requirement of tensile strength of a wire and its corresponding range It is designated by the value according to the lower limit of tensile strength and is used when specifying wire and when determining the calculated minimum breaking force or calculated minimum aggregate breaking force of a rope expressed in N mm wire tensile strength Rm the ratio between the maximum force obtained in a tensile test and the nominal cross sectional area of the test piece expressed in N mm This document is property of Usha Martin Italia Reproduction is not allowed unless specifically agreed LAY lay length H that distance H parallel to the longitudinal rope axis in which the outer wires of a spiral rope the outer strands of a stranded rope or the unit ropes of a cable laid rope make one complete turn or helix about the axis of the rope lay direction of rope the direction right Z or left S corresponding to the direction of the outer strands in a stranded rope in relation to the longitudinal axis of the rope ordinary lay sZ or zS stranded rope in which the direction of lay of the wires in the outer strands is in the opposite direction to the lay of the outer strands in the rope NOTE The first letter denotes strand direction the second letter denotes rope direction lang lay 27 or sS stranded rope in which the la
30. ion due to lay direction Breaks distribution along the rope can indicate fatigue beginning therefore the number of broken wires over a significant rope length e g 30d is not proportional to the number of localized broken wire in a specific portion e g 6d which could be due to other causes to be specifically investigated This document is property of Usha Martin Italia Reproduction is not allowed unless specifically agreed 7 usha martin DISCARD CRITERIA FOR DIAMETER DECREASE DEFORMATION AND CORROSION Diameter shall be periodically measured and compared to the initial reference value i e recorded measurement taken immediately after receipt to detect uniform or localized variations Diameter decrease has to be calculated using the following formula Diameter decrease 96 100 reference diameter measured diameter nominal diameter In case of uniform decrease the maximum allowed value is 596 in respect to nominal diameter for non rotating ropes 7 596 for other rope constructions with steel core 1096 for fibre core ropes A clear localized decrease indicates a severe failure of rope core and leads to immediate rope discard Also in case of break of a complete strand rope has to be immediately discarded Ropes showing deformations like basket core or strand protrusion or distortion kink or tightened loop shall be evaluated and can remain in service if the damaged portion can be removed and if the remaining part of r
31. ion has to be applied the rope has to be spooled on an intermediate reel or special reel requirements have to be agreed with the rope supplier When first installing the rope a pilot line having adequate breaking force to bear the installation pull should be reeved on the system and connected to the rope itself The pilot line shall have same lay direction and type as the rope to be installed otherwise twist could be induced and permanent damage could occur lt the rope is superseding an existing one having same characteristics it can be installed with the aid of the old one by connecting the two wire ends in a proper way using clamps splice chinese finger becket loop etc A swivel should not be used during the installation of the rope During pulling into the system the rope should be carefully monitored and it should not obstructed by any part of the structure that may bring damage and result in a loss of control FIGURE 26 BROKEN WIRE DUE TO IMPROPER HANDLING The equipment should be run at limited speed to facilitate gradual rope stabilization Full load should never be applied during this stage During spooling continuous check has to be performed to verify that no slack occurs in the rope or cross laps of rope develop at the drum as irregular coiling would inevitably result in severe surface wear and rope distortion In multilayer drums the crossover area see figure must be carefully monitored A good spooling will show tight wr
32. l closed ropes a minimum of two servings is recommended Before cutting the rope a clear mark should be applied on the cut area and servings should be applied at each side of the mark Depending on its size the wire rope can be fused and tapered or cut using high speed abrasive disc cutters percussive or shearing methods paying particular attention not to disturb the position of wires and strands below the serving Rope core can be cut with no major issues in case the it has the tendency to protrude in respect to the outer layer Suus gms SSR SSS FIGURE 21 SERVING DIMENSIONS AND CONFIGURATION Diameter of service wire or strand Rope size mm Wire Strand Up to 22 mm 1 1 1 5 1 6 1 8 From 22 to 38 mm 1 4 1 8 1 6 2 5 From 39 to 76 mm 1 6 2 0 2 5 3 0 From 77 to 100 mm 1 8 2 2 3 0 3 5 Over 100 mm n a 3 5 4 0 TABLE 1 TYPICAL SERVING WIRE AND STRAND DIMENSIONS This document is property of Usha Martin Italia Reproduction is not allowed unless specifically agreed usha martin SOCKETING OPERATION Rope end connections can be temporary if used for rope rewinding or installation on the drum or permanent to be used during lifting operations Permanent connections allow to respect the installation safety working load and are characterized by a specific efficiency depending on the connection type which varies from 100 for resin sockets to 80 for wedge sockets Temporary end connecti
33. l tendency to twist when subjected to axial loads This depends on the geometrical arrangement and can be reduced by compensating the core tendency to rotate in one direction with an opposite tendency of the outer layer as typically applied to spin resistant and non rotating ropes Rope are conventionally classified based on the number of turns that a portion with length of 1000 times nominal rope diameter would make when pulled at 20 MBF with less than 1 turn a rope is classified as non rotating from 1 to 4 turns as low rotation from 4 to 10 as spin resistant higher than 10 as not non rotating Each rope is characterized by torque factor which is used in the calculations when both ends of the rope are fixed and rotation factor expressed in degrees lay which is used when one end is free to rotate Both torque factor and rotation factor strongly decrease after rope stabilization and are negligible if the rope is always used at same working load and lifting height In case of single fall lifting a non rotating rope is typically recommended while in case of multi part reeving arrangement rope type has to be selected depending on height of lift block configuration and loading A wrong rope selection or improper installation and training can cause cabling phenomenon which can lead to permanent rope deformation like waviness and severe operations issues The maximum lifting height for a given rope torque factor t can be briefly calculated u
34. olling or swaging compacted swaged rope rope which is subjected to a compacting usually swaging process after closing the rope thus reducing its diameter cable laid rope an assembly of several usually six round stranded ropes referred to as unit ropes closed helically around a core usually a seventh rope ROPE CHARACTERISTICS torque torsional characteristic the value of which is usually expressed in Nm at a stated tensile 10 11 12 13 14 15 7 usha martin loading and determined by test when both rope ends are prevented from rotating NOTE Torsional characteristics can also be determined by calculation turn rotational characteristic the value of which is usually expressed in degrees or turns per unit length at a stated tensile loading and determined by test when one end of the rope is free to rotate fully preformed rope rope in which the wires in the strands and strands in the rope have their internal stresses reduced resulting in a rope which after removal of any serving the wires and the strands will not spring out of the rope formation STRAND strand an element of rope consisting of an assembly of wires of appropriate shape and dimensions laid helically in the same direction in one or more layers around a centre NOTE Strands containing three or four wires in the first layer or certain shaped strands e g ribbon cannot have a centre compacted strand a strand which has been subjected to a
35. ons must not be used as lifting devices as they are not designed to ensure safety working load but only to allow to move the rope from the storage reel to another reel or to the winch drum Socketing media can be metal or resin which is more extensively used due to ease of handling and safety Moreover heat generated during metal socketing can affect steel properties of the rope According to regulations i e EN12927 the length of the tapered part of a socket shall be at least 5 times the nominal rope diameter or 50 times the outer wire diameter and the angle between the generatrix and the axis of the cone shall be from 5 to 9 The socket basket neck diameter shall be from 1 2 up to 1 3 times the rope nominal diameter and shall have a cylindrical portion long from 0 25 up to 0 5 times the rope nominal diameter The internal socket profile must not have grooves as these would reduce resin penetration To perform proper socketing the position of the wires and strands of the non socketed portion of rope shall remain undisturbed during the socketing operation therefore adequate servings are required Dirt grease scale or residues shall be removed from the inside of the socket basket to prevent resin contamination After having inserted the rope into the socket all the individual wires shall be opened to form a brush which shall be degreased to remove all traces of lubricant and shall be completely dry before the socketing medium is poured into th
36. ope is still suitable for use Other damages like flattened portion or permanent bend may not be cause of immediate discard but they have to be inspected with higher frequency as the affected portions are likely to deteriorate and show broken wires at faster rate than usual Waviness should be assessed using a straight bar and considering the gap between the rope and the cut surface see figure the maximum allowed gap is 1 3 the rope nominal diameter if the deformation affects a portion not running over sheaves or spooled on the drum otherwise it has to be reduced to 1 10 y FIGURE 33 WAVINESS ASSESSMENT Corrosion should be evaluated after having wiped the rope to remove contaminating particles and should be assessed considering type and severity Rope should be discarded in case of heavy pitting and slack wires on the external surface as well as in case of internal corrosion see figure indicated by the presen ce of debris extruding between the outer strands Rope should also be discarded in case of severe fretting corrosion which manifests as a dry red powder and is caused by the continuous rubbing between dry wires and consequent particles oxidation FIGURE 34 INTERNAL CORROSION This document is property of Usha Martin Italia Reproduction is not allowed unless specifically agreed 7 usha martin HEALTH AND SAFETY INFORMATION As a general indication applicable to all types of working environment workers must
37. rands ensure improved rotation stability and are therefore recommended for relevant lifting height or high capacity cranes FIGURE 5 LANG LAY LEFT FIGURE AND REGULAR LAY RIGHT FIGURE The natural tendency of the rope to twist must be in accordance with the direction of drum winding to get a tight contact between adjacent wraps especially on the first layer In case of plain drum right hand or left hand lay direction must be selected in order to match the drum s type and direction as shown the figure These indications are not strictly required for grooved drums as in this case the rope is already guided by the grooves themselves In case of grooved multilayers drums lay direction can be selected to facilitate the first layer spooling or optimized considering the rope layer that will be more frequently used during operations In case of grooved drums an adequate number of safety wraps should remain in place to avoid rope slipping while in case of plain drum the whole first layer should never be used as it works as a bedding for the following layers Painting the first layer or the safety wraps is a good practice to clearly detect the use of a forbidden portion of rope OVERWIND UNDERWIND OVERWIND UNDERWIND LEFT TO RIGHT RIGHT TO LEFT RIGHT TO LEFT LEFT TO RIGHT USE RIGHT LAY ROPE USE RIGHT LAY ROPE USE LEFT LAY ROPE USE LEFT LAY ROPE FIGURE 6 SELECTION OF LAY DIRECTION This document is property of Usha Martin Italia Repro
38. red phenomena like geometrical deformation core distortion or presence of heavy corrosion while a distributed diameter reduction can be associated to wear due to intensive use Ovalization is also a marker of possible rope issues which have to be properly addressed FIGURE 2 SUNKEN STRAND AND ASSOCIATED DIAMETER REDUCTION FIGURE 3 CORE DISTORTION AND ASSOCIATED DIAMETER INCREASE This document is property of Usha Martin Italia Reproduction is not allowed unless specifically agreed 7 usha martin ROPE LAY MEASUREMENT AND SELECTION Lay length represents one of the key characteristics of the rope and affect its elasticity and performance under load It has to be periodically measured as possible variations can indicate rope issues like forced rotation during installation or unlay due to excessive lifting height or misalignment of the reeving components ONE ROPE LAY FOR SIX STRAND ROPE FIGURE 4 LAY LENGTH MEASUREMENT FOR A SIX STRAND ROPE The choice of a Lang or regular lay rope has to be based on rope use and desired performance Lang lay ropes i e ropes having same direction as the outer strands give better stability to side wear phenomenon also known as crushing as the contacts between the wires of adjacent rope wraps are smoother They are particularly indicated up to 40 mm size ropes used on deck cranes or small winches Regular lay ropes i e ropes having opposite direction in respect of the outer st
39. rtin Italia Reproduction is not allowed unless specifically agreed usha martin ROPE DIAMETER AND MEASUREMENT Each rope is first of all characterized by the nominal diameter and oversize which have to be selected depending on system configuration and reference regulations According to EN12385 1 ISO and API standard diameter measurement has to be taken on a straight portion of the rope either under no tension or a tension not exceeding 596 of the minimum breaking force at two positions spaced at least one metre apart At each position two measurements at right angles of the circumscribed circle diameter shall be taken The most suitable measuring equipment is plate gauge capable to cover at least two strands see Figure 1 FIGURE 1 DIAMETER MEASUREMENT Diameter must be measured and recorded immediately after rope receipt as this value has to be used as a baseline for following inspections It has always to be considered that the actual diameter of the rope changes during use due to initial stabilization to the effect of working tension and to wear generated by the passage over the components of the reeving Permanent diameter reduction after first pull can vary from 0 5 to 3 depending on rope and core construction Diameter measurement is an essential tool which allows to give an immediate and simple evaluation of the overall condition of the rope For example a localized diameter variation can indicate undesi
40. sheaves rope minimum breaking force is affected in respect to linear load conditions depending on D d ratio thus reducing its efficiency see figure For moving parts further reduction must be considered due rope internal friction and efficiency of the rotating parts 100 90 80 70 Efficiency 60 50 40 D d ratio FIGURE 28 REDUCTION IN ROPE EFFICIENCY IN CASE OF BENT OVER STATIONARY COMPONENTS The efficiency of sheaves should also be considered when calculating the lead line load In case of systems having same number of rotating sheaves and parts of line e g 2 falls and two rotating sheaves like in the sketch the lead line load can be calculated by dividing the load by the efficiency coefficient e g as per Table 3 lifting 80 tons in 2 parts mode with roller bearing sheaves will give a lead line load of 80 1 94 41 2 tons If additional rotating sheaves are used unless otherwise specified the resulting line load should be divided by 0 96 0 98 or 0 99 plain roller bearing or high efficiency sheaves times the number of extra sheaves in respect to the rope bearing parts Parts of With plain With roller With high line bearing sheaves bearing sheaves efficiency sheaves 1 0 96 0 98 0 99 2 1 87 1 94 1 97 3 2 75 2 88 2 94 4 3 59 3 81 3 90 5
41. sing the approximate formulas shown in the sketch all dimensions are in mm In case of special block arrangement please contact us for a custom evaluation When operating a non rotating rope in single fall mode a swivel can be used to relieve the rope of any induced rotation resulting from angular deflections at a sheave or drum Swivels must not be used with not non rotating ropes like 6 strand as it would cause rope unlay severe reduction of its breaking force and secondary fatigue of the steel core not detectable during inspections APPROXIMATE CALCULATION IN CASE OF NUMBER OF FALLS HIGHER THAN 2 H LeM 4edet M B D ia C 26 227 gt 2 pf e H LeD 4edet FIGURE 14 CALCULATION OF MAXIMUM LIFTING HEIGHT FIGURE 15 ROPE WAVINESS FIGURE 16 EXAMPLE OF SWIVEL This document is property of Usha Martin Italia Reproduction is not allowed unless specifically agreed f usha martin REEL RECEIPT AND STORAGE After receipt the rope should be immediately checked to verify its identity and condition and should not be used without the possession of adequate documentation and certificates The Certificate of Conformity by the manufacturer should be stored in a safe designated place in order to quickly identify the rope and carry out periodic inspections During loading transferring and unloading operations rope reels or coils should be properly handled using slings or lifting beams as shown in the figures
42. t least five wraps on the drum In this case if a greater working length is subsequently foreseen to be used that additional portion should also be inspected The frequency of inspections depends on regulations type of crane and environment results of previous examinations load spectrum and experience related to similar ropes and systems The main modes of deterioration are broken wires or stands decrease in rope diameter corrosion deformation mechanical or heat damage and change in elastic behaviour of rope under load The following areas have to be inspected with particular care drum anchorage and any section close and in correspondence to rope termination in case of repetitive operations any part of the rope that lies over a sheave during crane working rope portion which lies over a compensating sheave cross over zones on multilayer drums rope sections subjected to revers bending over sheaves or rollers section subjected to external damage like abrasion or heat clamps and securing ferrules should be also inspected with special care to detect possible looseness due to vibrations cracks distortion wear or corrosion After each periodic inspection the competent person shall provide a rope inspection record and state a maximum time interval that shall not be exceeded before the next periodic inspection takes place The following sketch shows some examples of typical points which require special care during inspection
43. xial stiffness EA MN E 0 785 f d 1000 Elastic elongation 24 Load kN 1000 Rope torque Nm ted load kN MBF Mass Emodulu Torque factor t Ref lay Turn degrees lay Rope type Fill factor factor factor 5 factor f K km N mm Lang Reg k Lang is Non rotating d up to 40 mm 0 725 0 0 0049 127 0 02 0 009 7 25 2 Non rotating d up to 100 mm 0 740 dec 0 0049 130 0 012 0 007 7 1 5 1 Non rotating d over 100 mm 0 725 ud 0 0049 128 0 008 0 001 7 0 75 0 5 10 strands compacted spin 0 695 Dor 0 0047 125 0 05 0 045 6 5 12 8 10 strands compacted 0 695 o 0 0047 127 0 12 0 090 6 5 140 100 8 strands compacted 0 680 Don 0 0046 125 0 11 0 085 6 5 120 90 6 strands compacted 0 670 dm 0 0045 122 0 1 0 078 6 5 100 80 6 strands not compacted IWRC 0 590 dm 0 0042 122 0 1 0 078 6 5 100 80 Nominal values at 20 MBF for trained rope TABLETO TYPICAL ROPE PROPERTIES kg m 0 672 Ibs ft Ibs ft 1 49 kg m 1 m 3 28 ft 1 ft 0 305 m 1 mm 0 039 inch 1 inch 25 4 mm 1 kg 2 205 Ibs 1 Ibs 0 454 kg 1 Ib 0 0005 short t ton 1 short t ton 2000 Ib 1 metric t tonne 1 10 short t ton 1 short t ton 0 907 metric t tonne 1 metric t tonne 0 984 long t 1 long t 1 016 metric t tonne 1 kN 0 102 metric tf 1 metric tf 9 81 kN 1 N mm MPa 145 psi 1 psi 0 0069 N mm MPa This document is property of Usha Martin Italia
44. y direction of the wires in the outer strands is in the same lay direction as that of the outer strands in the rope NOTE The first letter denotes strand direction the second letter denotes rope direction ROPES rope construction the detail and arrangement of the various elements of the rope rope class a grouping of ropes of similar mechanical properties and physical characteristics stranded rope an assembly of several strands laid helically in one or more layers around a core single layer rope or centre rotation resistant or parallel closed rope NOTE Stranded ropes consisting of three or four outer strands can or cannot have a core single layer rope stranded rope consisting of one layer of strands laid helically around a core rotation resistant rope stranded rope designed to generate reduced levels of torque and rotation when loaded NOTE Rotation resistant ropes generally comprise an assembly of at least two layers of strands laid helically around a centre the direction of lay of the outer strands being opposite to that of the underlying layer Ropes having three or four strands can also be designed to exhibit rotational resistant properties parallel closed rope stranded rope consisting of at least two layers of strands laid helically in one closing operation around a strand or fibre centre compacted strand rope rope in which the strands prior to closing of the rope are subjected to a compacting process such as drawing r
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