Passive Heave Compensation (PHC) systems used during offshore lifting operations are designed to absorb motions where it is needed, namely at the hook of the crane. This reduces motion and thus the overall forces on the deployed units. Fundamentally they are very simple and robust systems, relying on a hydraulic cylinder and pre-pressurised accumulator. Unlike Active Heave Compensation (AHC) systems, the risks of failure during critical stages are reduced, bringing greater assurance to operations. They are also less power hungry and less fatigue damaging to both ropes and sheaves within the crane. PHCs already have a long track record of successfully improving weather sensitive operations and thus productivity.
This paper considers the joint development between Technip and Cranemaster® of a new family of PHCs; the adaptive PHC system. This system brings greater flexibility, automatic weight adjustment, pressure compensation and data logging, whilst retaining the robust requirement in design.
Development of the adaptive PHC unit has included a thorough mathematical analysis to demonstrate the achievable benefits in improved performance and thus identify the increased weather window potential that this intelligent system can bring. Simulation of the instrumentation and valve system was completed to help design the automated algorithms to achieve these goals. The first adaptive PHC unit has successfully completed extensive onshore testing. This paper considers the details of the analysis, simulation and testing approach, highlighting what operational savings could be achieved through the adoption of this adaptive PHC system.
Offshore testing of the first unit will be used to validate all system functionality in a dynamic environment and allow a technology certificate to be obtained from DNV-GL.