Rotork Gears has designed and manufactured an innovative gearbox to provide a key function in subsea valve intervention systems used for diver-less applications in the offshore oil and gas industry.
The Linear Subsea Model 1 (LS1) gearbox is currently installed in a Choke Insert Running Tool (CIRT) that is used for the maintenance of retrievable choke valves in shallow and deep water subsea locations. In this most demanding application, a CIRT is lowered onto the top of the valve and attached to the choke valve insert, which is then lifted out of the valve and brought to the surface inside the CIRT. A second CIRT containing the replacement valve insert is then lowered onto the valve and the insert is lowered into the valve.
The key duty in this process is the lifting and lowering of the valve insert and this is the function performed by the LS1 gearbox. It is designed as a linear screw jack system and can be operated either by a Remotely Operated Underwater Vehicle (ROV) or manually by a diver via a handwheel.
Reliability is vital for this function so the gearbox has been designed for subsea applications at any depth with a pressure compensated design allowing sea water to enter and avoid any pressure compensating problems.
In spite of its small dimensions, the LS1 gearbox has a maximum lifting capacity of five tonnes. The screw jack system can also be configured horizontally, providing increased flexibility to suit other subsea applications. The LS1 design allows an increase in the number of input turns when used with an ROV.
