A Damping Tugger System for Offshore Heavy Lifts

Abstract

HMC’s new Deep Water Construction Vessel, Aegir has reeling capabilities using an exchangeable reel concept. The reel logistics is performed by transport vessel or barges while the vessel utilizes its 4000mT main crane to take on board new full reels and unload the empty reels at the offshore location. To ensure sufficient workability for this critical lift operation, a damping tugger system is developed to control the swinging motion of the suspended load which is often a governing criterion for the offshore lift operation. The patented system not only dampens the swinging motion of the suspended reel, but also has a large damping effect on the vessel roll. The roll motion is almost critically damped resulting in very calm motions of the vessel during the reel lift, to enable a controlled and safe operation. The paper describes the critical aspects of the reel exchange operation and how this is extensively analyzed both in frequency and time domain simulations to finally come to the system with damping tuggers to significantly improve the operability. The concept has been verified with model test and the simulation models are validated.