Deep-water installation in harsh weather conditions made possible by active heave compensated hoisting system in which IHC combines extensive knowledge with hydraulics, automation, winches and heavy lifting technology.
The 400t active heave compensated hoisting system allows the heavy-lift vessel to perform more installation jobs each year, maximising return on asset investment.
Our client needed a 400t hoisting system to safely place heavy loads onto the seabed at a depth of up to 3,000 meters. To ensure maximum return on the asset investment, the system would have to be able to perform installation jobs in dynamic sea states.
During deep sea lifting and lowering operations, it is important to keep full control over the load to prevent it from slamming into the seabed. Regular Active Heave Compensators are designed to keep the lifting point steady in relation to the seafloor, compensating the movement of the vessel caused by swell and waves. In this case, however, the large working depths of up to 3,000 metres, added an extra challenge.
Over such great distances, even the strongest cables can stretch up to an additional 8 metres in length. So even if the lifting point is kept steady, the load can start bouncing (oscillating) due to the spring-like characteristics the cable develops in these conditions.
By combining our extensive knowledge of hydraulics, automation, winches and heavy lift technology, we designed, engineered and constructed a system that integrates an active heave compensator and a winch system. It includes a storage winch for 3,500m of wire rope, the complete drive and control system with motion reference unit, and controls cabin.
The system not only balances out the motion caused by waves and swell; its dedicated control software also identifies potential resonance hazards and actively neutralises the typical frequency to avoid the risk of resonance. A safe lowering operation can be demonstrated by logging force, speed and accelerations during the entire lowering operation.
Moreover, this advanced system has a splash zone mode that keeps the hoisting wire tensioned the moment the load enters the waves. The transition between resonance avoidance mode, landing mode, active tension mode and quick lift mode is performed smoothly to avoid sudden uncontrolled movements.