Active Heave Compensation (AHC)

Active heave compensation (AHC) is a powered crane or winch control that counteracts vessel heave in real time so a subsea load holds a near-constant depth during lifts through and below the splash zone. A motion-reference unit feeds vessel heave to the winch drive, which pays out and hauls in to cancel it; unlike passive systems that store energy in a gas accumulator, AHC drives the wire actively and can hold position with the load stationary. IMCA M 187 and the SWL/dynamic-load checks in the crane’s hook-load rating govern its use offshore.