The offshore wind industry is growing rapidly and the number of personnel transfers between turbines and work boats is increasing. As this is considered an operation that carries a significant risk, a number of improvements have been developed in the industry. In order to provide a cost effective solution optimised for the safety and convenience of operations, a Turbine Access System (TAS) was developed. The functionality of TAS is based on the principle that the motions of the vessel are actively compensated in heave, roll and pitch in order to provide a stable platform for personnel transfer.
This paper presents the technical design of TAS, including the development of the global design, the hydraulic system and the control systems. This covers deriving the general arrangement of the unit, obtaining the required inverse motions of the gangway, the means of hydraulic cylinder activation and developing the control system.
The control system comprises cascade control with feed-forward and nonlinear compensation in order to minimise trajectory tracking errors. The methodology to derive high degrees of accuracy and smooth operations is discussed alongside the operational logic, monitoring, fault actions and safety features which are accessed through two touch-panel computers.
The first TAS came into operation during the summer of 2012 where it was mounted on a 24m catamaran. The sea trials, offshore commissioning and control system optimisation provided extensive amounts of data on the performance of TAS in waves. The results of the performance in waves has been investigated and documented in order to validate the claims of the functionality of TAS.
Further optimisation of the motion compensation principle is discussed where the main focus lies on the increase of the operability range beyond the current standards. By changing the bow fenders of the work boat to rollers that provide hydraulic energy dissipation, the additional imposed pitch damping is expected to reduce the boat motions and increase the TAS operability. The paper discusses the methodology and logic behind the active pitch damping devices and the effect on the operation of TAS.
The paper discusses the main technical challenges and solutions to achieve a safe, user friendly and comfortable transfer system for the offshore industry.
