ABS Speeds Truss Spar Projects to GOM

ABS-classed as a XA1 Floating Offshore Installation, the Medusa truss spar will be located on Mississippi Canyon Block 582 in 2,223 ft. of water.

Murphy Oil's Medusa truss spar has a hull diameter of 94 ft. (28.6 m) and a total length of 568 ft. (173.1 m). The sixth truss spar to be installed in the Gulf of Mexico, the facility will have capacities of 40,000 barrels of oil per day and 110 million cu. ft. per day of gas.

In addition to Medusa, ABS is classing and certifying several other deepwater truss spar projects now under way, including Dominion/Williams "Devils Tower," BP's "Horn Mountain" and "Holstein" and Kerr-McGee's "Boomvang," "Nansen" and "Gunnison" spars.

ABS maintains efficient interface with the U.S. Coast Guard, the Minerals Management Service, oil and gas companies and various contractors to significantly accelerate the regulatory compli- ance of these Gulf of Mexico deepwater applications.

Truss spar installations continue to grow in popularity in the Gulf of Mexico, offering avenues for deepwater developments. Classification society American Bureau of Shipping (ABS) has been apply its considerable deepwater expertise of late, as ABS is providing classification services while facilitating fast-track fabrication and installation schedules for Murphy Oil's "Medusa" truss spar and for the Dominion/Williams "Devils Tower" truss spar, currently the world's deepest dry tree platform in progress.

As for all floating production systems operating in the GOM, these two projects must comply with federal regulatory codes in order to receive a Certificate of Inspection (COI) from the United States Coast Guard (USCG) and a permit to operate from the Minerals Management Service (MMS), says Lynnda Pekel, ABS project manager for both the "Medusa" and the "Devils Tower" truss spars.

"The interface that ABS maintains with the Coast Guard, the MMS, oil and gas companies and various contractors and vendors significantly accelerates the regulatory compliance of these Gulf of Mexico deepwater applications," said Lynnda Pekel, ABS project manager for both the Medusa and the Devils Tower truss spars., said Pekel.

Truss spars-similar to caisson or classic spars in their operational profile-are intended to offer some design improvement.

The truss spar is primarily characterized by its space frame of tubular members, which provides the structural linkage between hard tank (flotation tank) and keel tank as well as support to the heave plates. The heave plates provide added mass and damping to further reduce heave motions and to improve stability.

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