Valves play critical role in Caspian Sea platforms

BP's exploration and development of Azerbaijan's oilfields in the Caspian Sea is the driving force of one of the largest infrastructure projects in the world.

BP's exploration and development of Azerbaijan's oilfields in the Caspian Sea is the driving force of one of the largest infrastructure projects in the world.

It has involved close collaboration with main contractor Halliburton KBR to construct 14,000t, 280m-high oil platforms that are the initial constituents of a massive programme, also encompassing the construction of a more than 600km of pipeline and the development of one of the world's largest oil terminals at Sangachal.

A key element in this first float-over installation in the Caspian Sea, delivering access to a projected 400,000 barrels per day throughput is clearly the successful "launch" of the gigantic platforms - a complex operation that demands accurate positioning to avoid them sinking into the mud of the Caspian Sea.

As part of the process, hydraulically actuated Argus ball valves - in an order valued at GBP 1.5 million - have been specified to control the flow of seawater into the platform legs (known as "jackets").

Each jacket measures approximately 140 x 75 x 58m and is carried on huge barges which are positioned precisely by a satellite guidance system.

Once in position the barge is deliberately flooded at one end, causing it to submerge partially and the jacket to slide off into the sea.

The jacket floats until the Argus 4 and 6in FK76 valves are opened in sequence to allow water in to a series of compartments to exactly the correct volume so that the jacket sinks slowly and under control.

By regulating the flow of water the speed of descent is also controlled, allowing a floating crane to manoeuvre them slowly and precisely into position on the seabed.

As back up, Argus is also supplying 2 and 6in submersible valves which can be operated under water by ROVs (remotely operated vehicles).

Although the ROVs can exert sufficient torque to operate the specially designed 2in valves using normal 90-degree operation, the 6in FK76 valves require additional torque and are controlled using special gearboxes designed and produced in Flowserve's Argus centre in Ettlingen, Germany.

These gearboxes allow the ROVs to cycle the valves using just six turns, instead of the more usual 18 to 20.

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