THE CHALLENGE: Install Belly Strakes on the hull of the Tahiti Spar up to 850 feet below the water line and tension the 3" studs without the use of divers.
THE SOLUTION: Robotic Installation. Fastorq designed and manufactured 3" Zip Nuts to be installed on the hull of TAHITI in the shipyard. Fastorq also designed and built 3" Auto-Zip DZ300ROV-4 stud tensioners equipped with hydraulic motor driven nut rotators and two HTP-28000 power units to provide power and control to operate all functions of the stud tensioners from a remote location.
TESTING: The Fastorq stud tensioners and power units were tested on a test fixture provided by Oceaneering at their facility in Houston with representatives from Heerema Marine Contractors, Statoil and Chevron present to observe. Oceaneering also designed and built a Tensioner Control Panel to provide robotic control of the tensioners when deployed below the water line. Tests were also conducted at Mohr Engineering to verify tensioner performance at 850 feet water depth.
INSTALLATION: The offshore cranes and the Heerema vessel Baldor provided by Heerema are used to lower the Belly Strake sections with the 3" studs and stud tensioners installed on the Belly Strakes; into position on the hull of TAHITI. The 3" studs are inserted into the 3" Zip Nuts as the crane lowers the Belly Strake section into position. No rotation of nut or stud is required as the stud pushes through the Zip Nut.
Hydraulic hoses are deployed by a LARS connecting the Fastorq HTP-28000 power unit to the Oceaneering Tensioner Control Panel (TCP). The TCP is connected to the tensioners for subsea operation and control. An ROV is positioned to observe the functions of the tensioners and intervene if necessary.
The Fastorq DZ300ROV-4 tensioners are employed to pull the 3" studs into full tension and the hydraulic motor driven nut rotators are used to turn down the service nuts robotically. The DZ300ROV-4 tensioners are released from the 3" studs by hydraulically releasing the Double Zip nuts.
The ROVs are then employed to remove the tensioners from the 3" studs, cut sacrificial hydraulic lines and prepare the stud tensioners to be returned topside for reuse.
A total of 6 belly strake sections are installed with a total of 36 studs of 3" diameter and 36 Zip Nuts. A total of 12 Fastorq DZ300ROV-4 robotic stud tensioners are employed three times each to complete the installation.