For marine winch applications, there are many advantages to using synthetic rope as steel wire rope. Synthetic rope is lighter, more buoyant, and higher flexibility, all of which are even more important for marine applications. Synthetic rope also stores less energy than steel rope, making it safer in a break scenario. Synthetic rope can be repaired, if require, by braiding broken ends, but this should be done by the professionals. Another important advantage is that steel rope strands can break, causing a dangerous loose sharp end, which can snag hands, even if they are gloved.
Over time, synthetic rope is susceptible to UV exposure, and abrasion. Plus heat and chemicals can effect synthetics more so than steel.
Types of Marine Winches:
A winch is a device that pulls, hauls or lifts an object thru rope, cable or chain medium by typically winding around or from friction against a rotating drum. Marine winches are mainly used for towing, mooring, anchoring, lifting heavy objects on-board and over-board.
Type of Marine Winch Drives:
Basically, there are 3 different ways of powering a marine winch; pneumatically, hydraulically and electrically; hand crank is excluded here. Provided is a brief, not exhaustive, summary of advantages and disadvantages of each:
-Pneumatic is least efficient, usually noisy, usually less controllable, and susceptible to debris in air supply. Pneumatic is inherently spark resistant for X-proof environment and compressible nature of air makes torque control easily achieved. In cold environments, provisions must be made to reduce freezing of the exhaust, which restricts air flow, reducing torque output of the winch.
-Hydraulics offer least footprint to power ratio, meaning, the size of hydraulic drive components is generally less than other modes for a given torque/horsepower required. With proper system design fairly accurate speed and torque are attainable. Efficiency of hydraulics is greater than pneumatic. Hydraulics are messy, assuredly will leak over time, and generally higher maintenance than electric. Provisions should be made to contain the leaking fluid. Generally, excess hydraulic flow/pressure is available on most marine vessels and can be applied to added winches inexpensively. If hydraulic power unit is required, these can be made explosion proof rated without too much added expense.
-Variable speed electric winches offer low operating and maintenance costs, easy installation and most efficient power to a winch. They also offer the greatest accuracy in speed, position and torque control. Plus, during rendering (paying out material), the power from the VFD drives can be put back to vessels power, otherwise braking resistors are required to exhaust this energy. Explosion proof and wash down motors, which are mounted on the winch, are relatively inexpensive and widely available, but a large VFD X-proof enclosure can be quite expensive. It’s generally recommended to mount these VFD enclosures off the deck, inside of a control or engine room.
Direct Drive vs Chain Drive Winches – Generally, the less mechanical components the better in terms of reliability and maintenance. A chain and sprocket between motor and winch drum are mechanical items that can and will fail at some point. Direct drive couples the motor/reducer directly to the drum shaft, eliminating the addition potential failure points. However, space limitations sometime dictate a chain (or belt) configured winch.