A vertical-axis powered drum on deck used to heave in mooring lines or warping lines.
In practice
Capstans are commonly located at the bow and stern to complement the windlass and mooring winches. They are driven by electric or hydraulic motors and are fitted with variable-speed controls. Correct operating technique is critical: turns of line on the drum must be maintained under controlled tension, and personnel must remain clear of snap-back zones. Under ISM Code requirements, the planned maintenance system must include scheduled inspection and lubrication of capstan bearings, gearboxes, and motor connections. Where a capstan also serves as a windlass gypsyhead, it may be subject to classification society certification requirements for its safe working load.
Regulatory detail & full definition
A capstan is a vertical-axis powered drum fitted on deck and used to heave in mooring lines by turning a rope around the drum head and taking tension on the hauling end. Unlike a horizontal windlass, the capstan cannot lock a line under load; the operator or line handler must take in the slack continuously as the drum turns. This arrangement is particularly useful for warping operations, pulling the ship along a quay or into position using fixed wires or lines ashore.
Capstans are commonly located at the bow and stern to complement the windlass and mooring winches. They are driven by electric or hydraulic motors and are fitted with variable-speed controls. Correct operating technique is critical: turns of line on the drum must be maintained under controlled tension, and personnel must remain clear of snap-back zones. Under ISM Code requirements, the planned maintenance system must include scheduled inspection and lubrication of capstan bearings, gearboxes, and motor connections. Where a capstan also serves as a windlass gypsyhead, it may be subject to classification society certification requirements for its safe working load.
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