No more waiting for good weather

Integrated 400t active heave compensated hoisting system enables safe deep-water installation in less than favourable weather conditions.

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.

 

THE CHALLENGE

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. 

 

OUR SOLUTION

By combining our extensive knowledge of hydraulicsautomationwinches 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.

Keeping loads under control

Requirements to safely transfer 400t loads to water depths of 3,000m with minimal energy consumption.

Advanced control system

Our dedicated control software identifies potential resonance hazards. It 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.

Neutralising resonance

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.

Quick lift

The integrated quick lift mode is activated on the through of a wave to perform a controlled lift without risk of reimpact to the seafloor.

Smooth transition

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.

Splash zone crossing

Instant wire load changes occur when entering the waves. Our AHC system keeps the hoisting wire tensioned – and minimises uncontrolled motion.

Subsea landing

A stepless, controlled and low landing speed is essential for a safe landing. Our integrated approach ensures the highest motion reduction even at water depths of up to 3,000m.

Results

The active heave compensated hoisting system enables the heavy-lift vessel to safely perform installation jobs, even in less than favourable weather conditions. Not having to wait for the perfect weather window, allows the vessel to operate an extra 60 days each year.

Technical specifications


9.338 km
8.000 MM
Compensated stroke
350.000 m3
95 cent
Per motion
compensation
36 Vessel
3.000 MM
Water depth
36 Vessel
400 tonnes
Workload

 

 

 

TECHNOLOGIEs FOR HARSH OFFSHORE CONDITIONS IN DEEP WATERS

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