Unique lift for Seaflex

20 May 2014

One of the 50 tonne ALBs is installed on the moorings to reduce tension

One of the 50 tonne ALBs is installed on the moorings to reduce tension

Unique Seaflex, part of Unique Maritime Group, completed an underwater lift to decommission a floating production storage and offloading (FPSO) unit for Lundin Tunisia.

The job was carried out in approximately 300 metres of water 80 km off shore from Tunisia. Moorings weighing several hundred tonnes needed to be disconnected.

To complete the job, 41 air lift bags (ALBs), weighing up to 51 tonnes each, were installed on the moorings to reduce their tension, a company spokesperson said.

“The deck-mounted linear winch was rated to 450 tonnes but, because the three mooring anchors were extremely well embedded in the sandy seabed, the effective tension on the chafe chain would have increased by an estimated 1.5 to 2 times the original 400 tonnes,” a company spokesperson explained.

By using the ALBs it was possible for the winch to pull on the chafe chain and slacken the connection to the Ikdam deck hook. The connecting shaft was then pulled out from the wren hook, which freed the chafe chain allowing the mooring system to gently be lowered.

“Once released, the chafe chain was transferred to a nearby AHTV which held the de-tensioned mooring system whilst the Ikdam FPSO was disconnected,” a spokesperson added.

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