FEATURE
WINCHES & ROPES
Pulling Together
Advances in ropes, winches impact workboat design, capability
When it comes to "marine technology," thoughts often turn to advances in hull and vessel design, propulsion equipment and efficiency, or marine electronics and communications. When considering advances in "enabling" technologies; technologies that have revolutionized some aspect of the marine industry, one need not look much further than advances in rope and winch technology over the last two decades. "There is a sea change in the way in which these tugs are specified today," Barry Griffin, VP of Sales for B.A. Griffin Associates and sales representative for Markey Machinery, in discussing Maritime Reporter's June 2009 "Vessel of the Month", the 3200 Class tug Monterrey. Today, as we are dealing with larger ships, increased security regulations and more dynamic seas; everything has changed. After you have to determine the operating conditions under which the tug will operate; first you determine the rope that can handle the movement, then you pick the winch that can handle the load, then you select the power needed. Griffin noted that demand for tug control over ships has led to a 10-fold increase of winch power over the past 20 years, as compared to a doubling of propulsive power in the same time. This is due in large part to the demand that tugs maintain a consistent bollard pull in even the roughest of conditions, a demand which means the line connecting tug and ship must remain as taut as possible even as the smaller vessel gets tossed about on the waves. Monterrey was built around the Markey DESDF-48WF winch, a high speed, 760-hp double-drum waterfalltype electric hawser winch. The winch uses render-recover technology to minimize the effects of sea-state induced forces and motion anticipated during offshore escort activity at the Energ�a Costa Azul terminal. It features two drums, each with 200m of 10 in. circumference soft-line in 7-plus layers. A single automatic level wind is situated to service both drums, and the winch also integrates a chain-windlass for 26mm anchor chain, to be used for tug anchoring service. The winch's automatic render-recover technology, pioneered by Markey, provides safe line control by operating within an upper and lower tension range selected by the tug Captain. Under dynamic sea conditions the DESDF-48WF winch is designed to maintain constant line tension and automatically compensates for the tug's surge, heave, and pitch - adjustments nearly impossible for a man to achieve using lever controls. By controlling tension and keeping slack out of the working line at all times the winch prevents snap-loads from occurring, thus reducing the risk of line breakage and/or damage to the bitts the line is tied off to on the LNG tanker. Another interesting new escort tug with a powerful modern winch is Foss' Carolyn Dorothy. Rolls-Royce supplied the winches, wich include a forward escort single-drum escort winch holding 200 m of synthetic fiber towline, and incorporates a windlass to handle the vessel's own anchors. Quick and sensitive handling of the towline is important in escort work, and the winch can pull 50 tons at 17 m/min. and render at 80 tons at 19 m/min, with 60 m/min. available at eight tons load. The aft winch has a brake load of 200 tons, and is a double drum unit holding 950 m of 52 mm wire rope on each drum. It is clear that much more attention is paid today to application of rope and winch technology on a case-by-case basis, meaning that innovations are being sparked by unique applications, and close
26
Maritime Reporter & Engineering News