Heave compensation systems may be provided to monitor motions of the sea and for causing line payout or haul in of a crane line in response to the motion. The compensation allows an object that is suspended from the line to remain substantially stationary below the surface and the compensation also helps to reduce the load on the line due to the heaving sea.
Many cranes use multiline systems for lowering or raising objects on and off of a vessel and/or to and from deep locations below the sea surface. To accommodate the multiline systems and avoid intricate and excessive line handling systems, portions of current heave compensation systems may be mounted on the boom of the crane. In addition, a large amount of hydraulic equipment and piping may be mounted near the base of the crane for controlling the portion that is on the boom.
These systems cause a large mass of equipment to be located relatively high on a vessel affecting the stability of the vessel. In addition, the systems may be integrated into the multiline system such that line wear occurring at or near the heave compensation system may require the full line to be replaced. Moreover, much of the line may commonly be below water and unavailable for inspection. Still further, the portion of the system that is located on the boom can take away from the overall capacity of the crane boom on which it is mounted.