Gimbal Suspended Gangway
Offshore gangway systems for transfer of personnel and equipment in use today is designed on a principle that a telescopic gangway section is mounted on a tower and is rotatable relative to the tower. The gangway section is hinged on the tower end, and a luff movement is made possible by hydraulic power.
When the tip of the gangway is established to the receiving structure a push force is activated to keep the tip of the gangway stable to the receiving structure.
On tests against offshore structures you find examples that the tip of the gangway has slipped off the receiving structure and the push force has driven the gangway into the structure and in that way caused damages.
A gangway system like GSG, that use vacuum force to establish a connection to the receiving structure has several advantages. After established to the receiving structure a smaller retract force can be activated, and if a fault should occur the gangway section would automatic pull back from the receiving structure and avoid damage to the receiving structure and the gangway it selves.
During personnel transfer the retract force could be deactivated and the telescopic gangway section operate in a passive mode for increased safety for personnel.
For to perform drilling operation and production of oil and gas in remote areas out of helicopter range, use of vessel with gangway solutions will be necessary to perform personnel transfer to and from the installations for crew change and in emergency situations. The gangway solutions must provide for a safe operation for personnel transfer even in bad weather conditions.
One must strive for a vessels ability to maintain a stable position against the offshore structure becomes the limiting factor for a safe personnel transfer, and not the gangway solution.
The unique solution the GSG holds to automatically keep the gangway level only by help of gravity, and without any use of energy makes the solution reliable and increase the safety. Systems that compensates for movements by help of control systems and hydraulic power has by this a possible source of error that could lead to unwanted situations.
The gangway solution GSG holds compensates with no limit, one more axis of movement than other systems. When the gangway is directed out from the vessels side, the gangway compensates automatically for vessel pitch movements by help of gravity. This can allow for a higher pitch and roll factor on the host vessel and still provide a safe operation.
Some gangway systems compensate for the vessel pitch by automatically tilt the entire tower by hydraulic power and can within a limit compensate for this movement by use of energy.
The freedom of movement of the gangway section in luff is significant and will not be the limiting factor related to the roll movements of a vessel on DP at an offshore installation.
GSG holds several advantages that can contribute to increased up-time for the offshore wind industry. It may open for increased use of offshore gangway solutions in the oil and gas industry and used for personnel transfer between vessels.
Establish/connection of the gangway:
Maintains a stable horizontal position no matter the pitch and roll factor on the host vessel with no use of active motion control. Use of active motion control only in the establishing phase.
The point of connection for the gangway tip can be a relatively larger area than in between a H-beam as many other systems make use of. This opens for connection with higher pitch and roll factor on the host vessel than today’s gangways can offer.
When the gangway is established a retract force can be activated, and if a fault should occur, the gangway would automatically retract the gangway section from the receiving structure and reduce the risk of damage to the receiving structure and the gangway.
Connection to the receiving structure by vacuum require only a smooth surface and can utilize existing structure on many offshore wind turbine solutions as well as a vessels hull for vessel to vessel transfer. Offshore structures that has no connection point for a vacuum solution can be modified by simple and inexpensive measures.
A low energy consumption. When gangway is connected to the receiving structure, a minor energy is needed for to run a vacuum generator.
Unlike some other systems that must cool down the hydraulic fluid after a period of use, the GSG has no time limit for operation when connected and in passive motion compensation mode.
All vessel movements are compensated in passive mode without any use of energy or control systems and so increase the safety of the system, unlike other systems where system errors could cause problems.
A high degree of freedom of movement opens for significant movements in the vessel and the receiving structure as you find in floating wind-generators as well as vessel to vessel transfer.
One more degree of freedom of movement than most other systems.
A high degree of freedom of movement, and a gangway that maintain a stable horizontal position only by help of gravity open for use on smaller vessels than used today with same degree of security, or operation with same type of vessels under worse weather conditions.
Use of vacuum for fixation of the gangway tip to the receiving structure opens for connection to any smooth surface and use of existing structures. Many offshore structures have an ideal surface on several positions on the structure and make vessel set up possible at the best location with respect to wind and wave direction. This is an advantage for increased operation limits and reduced fuel consumption for the vessel.
Transfer between two vessels with small or no adaptions on the receiving vessel.
Vacuum can create powerful hold force and be adapted to the holding force needed.