March 15, 1977 - Maritime Reporter and Engineering News

Lloyd's Register Studies Deep Oil Technology's Tension Leg Platform

As offshore oil operators move into deeper waters, the cost of constructing and installing conventional steel jacket or concrete gravity platforms rises steeply. The Tension Leg Platform System (T.L.P.) design by Deep Oil Technology Inc. of Long Beach, Calif., has been devised to economize on steel and to simplify installation problems for a drilling and production platform with workover capabilities, in water up to 590 feet deep.

The T.L.P. is basically a floating platform, the buoyancy of which reacts against the constraint of the vertical wire cables which anchor it to the sea floor.

This configuration acts to virtually eliminate vertical platform motions and to provide lateral and rotational restoring forces to reduce these motions.

Deep Oil Technology Inc. requested Lloyd's Register's Offshore Services Group to provide a quality assurance report to ensure that the proposed design would satisfy the mandatory requirements of the U.K. Department of Energy.

The submitted T.L.P. design is essentially a space frame of triangular plan form. The three sides are braced vertically and diagonally, and the upper and lower horizontal elements incorporate the deck and pontoons, respectively.

Tension mooring is achieved by three groups of wire ropes which run from winches on the deck vertically down through the corner main columns to anchors on the sea floor.

The length overall is 358 feet, breadth is 410 feet, and the depth to upper deck is 225 feet.

Operating draft is 162 feet.

Extreme survival conditions are for a wave height of 103 feet and 100-knot wind speed.

Within the limits of the study, Lloyd's Register considers that the platform design as approved would satisfy the mandatory requirements of the U.K. Department of

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