In 1995, with the construction of the tugs Protector and Guard for Crowley Marine Services, Markey Machinery developed the operational concept of Render/Recover® controls for its hawser winches. The idea was to develop a winch that would increase the performance, speed, and safety of certain tug escort and assist operations by automating certain winch functions. The primary goals were based on controlling line tension to:
The Class II Hawser Winch with the Render/Recover® system provided automatic “constant-tension” performance up to the limit of the hydraulic or electric power available, generally less than 75 to 100 horsepower. These power limitations of the first Class II Hawser Winch’s led to the development of the CLASS III Escort Winch with Markey Asymmetric Render/Recover® controls.
Early in 2000, Markey Machinery was asked to develop a winch concept for Crowley’s planned new tug, the Response. This tugboat would be involved in high-speed tanker escorts in the Strait of Juan De Fuca and ship-assist operations in Anacortes, Washington. Design goals for this new concept included:
The solution was to design a three-speed gearbox, or transmission, below-deck, controlled by a programmable logic controller (PLC) to automatically shift between ranges as required to match pull and speed requirements. As well, the overall system efficiency and performance was increased by using Alternating Current Variable Frequency (ACVF) electric power to drive the winch. Electric winches offer the highest overall system efficiency, providing full programmability and the ability to dissipate horsepower through dynamic braking resistors. Another feature of the new design was a wheelhouse adjustable levelwind that allowed the operator to influence how the line is spooled onto the drum. Synthetic hawsers are difficult to spool at high load due to problems associated with “diving” or “burying the line.” The approach taken was to set up the levelwind for open-weave type spooling and give the operator the ability to increase or decrease the spooling speed from the wheelhouse. This helps avoid issues while on missions and in full force maneuvers.
Finally, a water-cooled multi-disc brake was integrated into the design to improve shock-load and braking control, eliminating the drawbacks of traditional band-type drum brakes. Self-energizing band-type brakes are known for being able to withstand very high loads but they cannot be made to “slip” in a reliable, smooth fashion. Caliper-type disc brakes were ruled out for this application due to the marine environment and design considerations. The water-cooled multi-disc brake was mounted to the below-deck portion of the winch gearbox and provides finely controllable braking (or “rendering”) at up to 3x tug bollard-pull and handles payout speeds at up to 15 knots. With the water-cooling feature, this brake can dissipate a total of up to 1600 HP continuously.
Existing Hawser Tension Displays are limited to displaying line tension only when the drum band brake is set. With Markey Asymmetric Render/Recover® Controls, a strain-gauge type load pin is incorporated into the gearbox on an idler-pinion that can continuously and directly measure drive and braking torque. This is displayed in the wheelhouse as line pull. To simplify use, the engineers at Markey Machinery improved operator controls in the wheelhouse by separating them into “primary” controls on the starboard side and “secondary” controls on the port side.
The weight of this winch was a major concern. The challenge was to achieve a balance between minimum weight while also making it strong enough to react to operational loads. The finished weight of an ARR Winch ranges from 25 to 60 tons.