Having to land helicopters in high winds and on heaving and rolling vessels not only poses operational but safety challenges for helicopter transfer. Helicopters are also expensive to operate and maintain, requiring a significant amount of support both on the onshore and offshore facilities.
High speed vessels offer a viable alternative to helicopters and can provide increased safety as well as significant additional functionality at a lower cost. To make this work, TENSA has developed a safe and reliable lightweight personnel transfer system suitable for installation on high speed vessels.
This complete personnel transfer solution mounts a lightweight aluminium telescopic gangway on a heave compensated platform. On the FPSO, there is a simple adjustable height landing platform. A motion monitoring system gives clear guidance on the relative vessel motions and confirmation that conditions are suitable for gangway transfer.
This is a total system that ensures that the operation can be undertaken safely.
A key feature of the gangway is active telescoping. This was developed in conjunction with Uptime in Norway and allows the gangway to be landed on a small flat landing. The end of the gangway remains in the same position by automatically telescoping in or out even if the boats move apart or together.
Vertical motion is handled by active heave compensation of the gangway support platform. The system can also be extended to compensate for relative motions between two moving vessels by using a second wireless motion reference unit on the receiving vessel. The TENSA Dynamic Motion System (DMS) already has this proven wireless connection and differential motion functionality.
With this system, the availability in a location offshore Northwest Australia would be above 90% so that all transfers could be undertaken by boat with appropriate management.
By having the ability to transport up to two 20ft containers, the system can handle virtually all of the routine and urgent supply requirements for offshore production facilities.
The whole gangway system can be secured to the vessel deck with twistlocks so that it can be easily installed and removed in under an hour. This also allows the vessel to be fully utilised for deck cargo if required.
The benefit of this system, according to Derick Markwell, TENSA’s managing director, is that “instead of having regular vessels fortnightly or monthly from the support base and one service a week with helicopter, you can have personnel transfer and up to two sea containers of cargo by boat daily”.
A single vessel could easily service three or four offshore facilities.
TENSA is looking at a system weight of under 12 tonnes, compared to a conventional active compensated gangway system that would weigh around 35 tonnes. The system costs less than 30% of the traditional systems.
“High speed vessels are most applicable at places like Exmouth where the fields are close to shore. There is also an opportunity at the limit of helicopter reach such as the northern Timor Sea. We see it is a compelling solution for the offshore oil and gas industry as it really offers benefits in all areas”.
Photo credits: Southerly and Strategic Marine