New lift system tested in Gulf

A new lift system removed Mobil Exploration & Producing Co.'s 250-ton deck from a jacket in West Cameron Block 77 (Fig. 1).

In a test, a new lift system successfully removed a 250-ton deck from Mobil Exploration & Producing Co.'s West Cameron Block 77 jacket, in the Gulf of Mexico ( Fig. 1 [29939 bytes]).

Versatruss Inc., New Orleans, expects its new system may change the method of lifting heavy decks.

The patented lift system is the invention of Jon Khachaturian, president of Versabar Inc., New Orleans.

He describes the lift system as two barges equipped with custom-made A-frame boom trusses. The base of each boom typically is secured to the centerline of the barge deck with a spreader beam, while the tip of each boom is inserted into a prefabricated receptacle (stabbing bell) installed at the top edge of the deck.

The deck is then lifted by pulling the two barges together with hoists connected to the deck's lower level legs, which increases the angle of inclination of the booms and raises the deck.

Khachaturian claims that the system has the following advantages:

Deck installation potential of up to 20,000-ton capacity compared to the 14,000-ton capacity now available with the largest derrick barges.
Shallow-water operations where access with large installation barges would involve dredging or was unfeasible.
No requirement for major jacket or deck modifications.
Lift operations that can be stopped or reversed at any lift stage, because unlike conventional float-over operations, the deck lowering is done "on the hook."
Local availability of all required equipment except for boom trusses, which must be custom built.
No requirement to mobilize a semisubmersible crane vessel when the deck weight exceeds the capacity of conventional mono-hull vessels.

Khachaturian says motion studies that have been conducted indicate the weather window for the lift system is similar to other methods.