Rotork Gears has successfully completed an order from Fluitek Valves for customised heavy-duty gearboxes to operate 450 mm (18″) Class 600 subsea ball valves at a depth of 130 to 150 m (460 to 490 ft) in the Zawtika oil and gas field in the Bay of Bengal.
The Rotork WGS range of quarter-turn gearboxes are designed for heavy-duty subsea applications and constructed with carefully chosen materials to offer the highest level of reliability in very harsh environments.
The customer specified that the model WGS550 gearboxes should be built with a special vertical input structure with a total height of 750 mm, capable of sustaining 3,000 Nm of bending moment force and a vertical axial load of 3,000 N. The design has been validated by Rotork Gears, using a Final Element Model (FEM) software simulation that predicts how a model reacts to physical effects, followed by a Mechanical Advantage (MA) test on an in-house test rig to confirm the efficient performance of the design.
The gearboxes can operate the valve by using a Class 2 Remotely Operated Vehicle (ROV) or a removable handwheel used by a diver. To avoid damage to the valves the input torque is limited at 170 Nm. For added security, special handwheels with calibrated Duplex stainless steel shear pins have been supplied and a highly visible operating data plate is attached next to the ROV bucket on each gearbox.
Completed valve and gearbox assemblies tests were performed in a hyperbaric chamber, simulating an external pressure of 27 bar (around 1.8 times the required pressure).