D e c k M a c h i n e r y

Taking Advantage of Synthetic Rope Technologylncludes Hardware MaintenanceBy Merry Schnell

J n a 2007 interview,Tom CrowleyI Jr., CEO ofCrowley Maritime,

Isaid that the most significanttechnical advance to effect efficiencyin the tanker escort business has beensynthetic rope. However, to many, thedifferences between steel-wire ropeand high-performance rope may not

Proper Line InstallationThe first defense in the service life

of a new rope is at installation, whenall hardware surfaces are exposed andcan be properly prepared against wearcaused by abrasion. While properlydesigned and engineered ropes made of

drum to prevent rope diving orburyinginto the lowerwrap layers.Tension canbe created by running the rope arounda newly resurfaced capstan, bollar4or pin. Another common method toproduce significant back tension is torig a rope stopper onto the line beinginstalled. The friction between the tworopes creates the appropriate tension.However back tension is created, therope should be led through or aroundsomething that is directly in line withthe winch so it can be loaded evenly.However, the surface of the deviceused to create the tension should notbe abrasive to the rope and the instal-lation speed or tension applied shouldnot generate excessive heat build upon the rope.

Back tension is intended to helpeliminate the rope's tendency to buryitself on the winch drum, but how theline winds onto the winch can help aswell. The line should be wound ontothe winch in a closely packed forma-tion to minimize areas where the ropemay "dive" or bury into the layers ofthe wind. Each layer should be installedin the valleys ofthe previous layers orcrossed overeach otherto support eachsubsequent layer. Layers should neverbe stacked on top ofeach other.

How Wil l theHardware Perform?

During installation of high-perfor-mance synthetic ropes, it is also a goodtime to consider how well hardware willperform in conjunction with the newlines. HMPE ropes are as strong as thewire ropes theyreplace, which can dan-gerously emphasize the underdesigned,worn or damaged hardware on a ship'sdeck that may break or pull free.

When Ed McCain, marine opera-tions manager of Hawaiian Tug andBarge/Young Brothers (HTBYB) re-placed their traditional heavy polyesterlines with Samson's Quantum -l2,theyfoundthatthey needed to overhaul theirhardware too.

"Moving away from the traditionalsynthetic lines was aprocess. Because

A crewmember adds back tension during the instal lat ion of rope onto a winch.courtesy of Samson.

be well known; nonetheless, they areclear-cut.

Steel-wire ropes are heavy on thedeck andhard on the crew; they abradeand wear machinery and equipment;and depending on the application,they have a limited service life. On asize-for-size basis, ropes made ofhigh-modulus polyethylene (HMPE) are asstrong as wire; they are one-sevenththe weight; easier on deck machineryand crew; and, with proper care, theycan outlast wire three to one.

Indeed, HMPE lines can make ahuge difference in the lives of own-ers, operators, and crewmembers;however, every precaution availableshould be taken to ensure the long andsafe service life of high-performancelines. These include proper installa-tion; chock and line protection; andhandling, inspection, maintenance,and repair of both the hardware andthe lines used on it.

HMPE fiber take maximum advantageofthe cut and abrasion resistance, theway inwhichthey wearcan be acceler-ated by rough surfaces.

Often, fibers are found on hardwaresurfaces that caused the abrasion. andthe external surface ofthe rope readilyshows abraded yarns. In order to avoidthis type ofwear, all surfaces that comein contact with the HMPE line must besmoothed to within a surface rough-ness of 300 microinches" as measuredby a surface comparator gauge. Fortugboats, this means bull nose, cap-stan, H-bitt, and winch surfaces mustbe made and kept as smooth and rustfree as possible.

Installing Rope on the WinchAfter surfaces have been prepped,

the line may be wound onto a winch. Theworking line should be installed withtension and in a close, tight wind on the

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D e c k M a c h i n e r y

the lines were no longer the weak linkin the chain of equipment, we had toupgrade our hardware- the lines wereoutperforming it," said McCain.

For optimum performance of thesynthetic lines, hardware and theirattachments should be maintained andreplaced when necessary as part oftheongoing maintenance of the vessel.Abrasion to high-performance linescan lead to ropes parting, and whileHMPE may part less violently thanwire rope, it can still be life threaten-ing. But perhaps even more dangerousis a piece of hardware that breaks ordetaches while under tension from ahigh-performance line.

Closed or Roller Chocks?There is some question asto whether

closed chocks or roller chocks workbetter with HMPE lines. Most usersassume that roller chocks are bestsimply because the chock rolls withthe line, thereby mitigating abrasion.This is true in theory. However, due tothe low coefficient of friction in manv

HMPE lines, the amount of frictionrequired to "roll" the chock cannot becreated. Instead, the l ine simply slidesover the roller.

Also, special attentionis needed where the ropemight exit the roller chockat a sharp angle, creating"pinch points" that canlead to rope damage. Thisis commonon spring lines,where, depending on thevarying heights betweenthe ship and berth, a moor-ing l ine can get'Jammed"between the horizontaland vertical rollers. Rollerchocks require additionalmaintenance to the bear-ings and the positions atwhich the rollers are set inan effortto keep the rollers

and offer significant advantages overroller chocks, which include easiermaintenance and reduced abrasion onhigh-performance lines.

A closed chock and line with chafe protection. Photo cour-tesy of Samson.

Both c losed and ro l ler chocksrequire basic maintenance, whichincludes keeping the contact surfacesfree from rust and damage. Conversion

moving smoothly.Based on trials conducted by Samson

on both types of chocks, it was con-cluded that properly maintained closedchocks provide a longer service l ife

conplete coverage ofyour yaluable r1pes

THE SrBONGESr NAME IN NOPE

www.pacmar.com . July 2009 . Pacif ic Marit ime 25

D e c k M a c h i n e r y

A severe ly abraded bu l lnose on a tugboat . Photo cour tesyof Samson.

to high-performance synthetic lines is a costly expenditure,but when considering hardware replacements, installing newclosed chocks, instead of new roller chocks, can providesignificant savings. Standard steel closed chocks are rela-tively inexpensive, and maintenance costs are low. Anotheroption is stainless steel closed chocks, which, although moreeipensive upfront than plain carbon steel, are still much

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26 Pacif ic Marit ime . July 2009 . www.pacmar.com

less expensive than roller chocks and have low maintenancecosts. This long-term cost savings can be a big advantagewhen converting a vessel from wire to HMPE lines.

Chafe Protection for Hardware and Lines

Typically, the constant movement between the ropeand hardware can actually keep the hardware smooth. Buteven what appears to be the smoothest hardware will causesome damage to the rope. While the most obvious abrasiondamage to the rope is external, internal abrasion is moredifficult to observe since it is caused by the movement ofthe internal stands relative to each other. Internal abrasionoccurs when the external strands pass over a rough surface,slowing them relative to the internal strands next to them.Heat is created in the process- and heat is among the big-gest enemies of synthetic ropes.

Because it is difficult to judge damage to the rope causedby internal abrasion, and because lines are often subjectedto surfaces not underyour control, such as mooring bollardsroughened and scored by wire ropes, proper chafe gear isthe second line of defense to ensuring the longevity of thesynthetic high-performance line. Chafe gear is essential inpreventing both external and internal abrasion. Properlydesigned chafe gear acts as a sacrificial layer for externalabrasion from rough surfaces, andreduces internal abrasionby keeping relative fiber movement at the surface of the ropeto a minimum. Chafe gear is a lifeline to HMPE ropes.

Rope Handing, Maintenance, Inspection, and Repair

Once your high-performance ropes are in place and readyto use, the crew should be trained on handling and safetyprocedures, rope inspection procedures, use ofchafe gearto protect rope in the chocks, and rope repair and splicingtechniques. Not all ropemanufacturers offerthoroughtrainingand follow through in these areas, so purchasing decisionsshould be made based on a few considerations:. All synthetic and wire ropes gradually loseAll synthetic and wire ropes gradually lose breaking

strength during use due to factors such as cycle load-ing, shock loading, abrasion wear, cutting, and fiberfatigue.Most injury-related accidents occur because of partedropes and wires. In fact, the UK P&I Club estimatesthat 53o/o of personal injuries in mooring operations arecaused by parted ropes and wire.Simple steps that include training, inspection, and saferetirement guidelines can be taken to lower the risk tocrewmembers.

The vessel's officers and crewmembers should be vigilantin routinely inspecting and maintaining all metal surfaces,making sure they remain rust free and smooth. It is alsoimportant the crew be trained on rope inspection proceduresand splicing techniques. The crew should be responsible forreplacing worn orcutchafe gearand making sure it isproperlypositioned. Safe retirement of the lines can be establishedbased on the needs of the vessel, and technical supportshould be provided by the rope manufacturer. EtrM

Merry Schnell is the marketing communications specialistfor Samson and has extensive experience in technicalwriting and editing in the sciences and engineering.