Conference focuses on best practices in towing rope technology

By Alan Sorum
Council project manager

A recent conference on rope design hosted by Samson Rope, a leading producer of high performance towing rope, shared best practices for towing that may be applicable in Prince William Sound.

Founded in Boston in 1878, Samson is the world’s largest producer of ropes made with “Dyneema,” an ultra-high molecular weight polyethylene fiber. The company manufactures ropes of traditional fibers, like nylon and polyester.
Samson provided the emergency towing equipment for the last two foreign-flagged tankers that called on the Valdez Marine Terminal. The International Maritime Organization, a United Nations agency tasked with improving maritime safety and preventing pollution from ships, requires tankers to carry an emergency towing package on their stern. In addition to this equipment, the Alaska Department of Environmental Conservation requires what is known as the “Prince William Sound Tow Package” to be carried on the bow of every tanker. This towing package consists of a messenger line, towline, buoy, and heavy-duty shackle that can be quickly deployed in an emergency.

Every year the company hosts a summit at its factory in Ferndale, Washington, where it invites customers and leading industry experts to discuss the latest innovations in rope design and manufacturing, and share best practices for rope use in the field. Project Manager Alan Sorum attended the summit for the council on November 9, 2016. Some highlights of the conference are shared below.

Testing rope used in real world applications

Analyzing used rope allows Samson to help its customers be safer and more efficient. Ropes are brought back to the factory for testing once they are taken out of service to measure breaking strength. The company uses the rope’s history, test results, and predictive modeling to help rope owners and operators in many industries predict when their lines should be replaced, providing safer operations.

Always important to the analysis is the rope’s history, including its installation, operational use, monitoring, and condition assessment. The company promotes periodic inspections, looking for cut yarns, compression, discoloration, inconsistent diameter, and melting and twisting of the rope. Effective management can greatly extend rope service life and improve overall towing safety. Samson provides pocket inspection guides and mobile apps for users to reference for these inspections.

At Samson’s extensive testing facility, they demonstrated a residual break test on a “pendant” from a Crowley tug, the Attentive, from its Valdez operation.

A pendant is a short piece of rope added to the beginning of a main towline meant to take the abuse that comes from regular use. The pendant can be periodically replaced to preserve the more expensive mainline. The Attentive’s line broke, with a truly impressive noise, at just over 900,000 pounds or 450 tons. This value is very close to the original strength of the rope when it was new.

New tow winch testing technology

Samson is in the process of commissioning a new winch test machine. A winch is a mechanical device consisting of a rope and a rotating drum that adjusts tension on a rope or line. This appliance, and the technology behind the analysis tool, allows them to test lines on a winch drum under load. The testing machine looks to be a significant tool in understanding line construction and uses that have not formerly been possible.

Designing towing systems as a whole

The naval architecture firm, Robert Allan Ltd, made a presentation on how they use a “systems approach” to optimize towing structure. Their approach looks at the system as a whole, and includes fairleads (devices that guide a towing rope), tow winches, towlines, and supporting structures, rather than looking at one piece at a time. There is limited room on a tug to accommodate towing infrastructure, so optimization of these systems is necessary.

Control systems for towing winches

Seattle-based Markey Machinery, who specialize in engineering custom deck machinery for vessels, made a presentation on their next generation “render-recover” winch control systems. A render-recover winch is designed to monitor and automatically adjust line tension. Markey has developed a more precise way to control the forces experienced on a winch during a tow. This reduces operator control of the system and improves the safety of their towing winches.

Applying lessons in Alaska

Samson worked with Crowley Marine for many years developing best practices in the use and care of high performance towlines. These included annual trainings, rope manuals, splicing instructions, inspection guides, and rope retirement support to prevent failures and safe operations. The council is encouraging Edison Chouest Offshore to adopt these practices as they assume their duties as the Alyeska marine services contractor.

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