Sub-sea actuator is largest so-far for Lucca
Rotork Fluid Systems has supplied the largest sub-sea rack and pinion actuator ever built at the Lucca factory. Measuring over two metres high and five metres in length, the single-acting spring-return model number GSR-2-500-160F/CX actuator is designed to operate a 24 inch, ANSI class 900 sub-sea safety isolation ball valve (SSIV) for the Tuna Gas Gathering Project, off the coast of Egypt.
The hydraulically operated package incorporates a special gearbox and de-clutch system manufactured by Rotork Gears which enables the actuator’s output drive to the valve to be automatically disconnected and reconnected, if necessary when maintenance is required. In such an event, uninterrupted valve operating availability is ensured by a separate ROV (remotely operated underwater vehicle) connection to the gearbox. Complete valve control is also maintained by means of the ROV interface on the gearbox if the actuator is removed. This feature enables a single, interchangeable actuator to be used on two or more valves. The complete system has proved to be very reliable, with the potential to achieve high levels of SIL approval. Diagnostic analyses are also available, enabling potential operating problems to be identified before they might occur.
Due to its considerable size, factory testing of the actuator demanded the construction of special equipment. In particular a tall frame was built in order to realistically simulate the ROV operation that would take place from the top of the installed valve skid, which is designed to prevent any damage to the valve from objects dropped into the sea or fishing activities.Testing was assisted by new external cranage installed at Lucca to handle the very largest of actuators in an area dedicated to sub-sea actuator testing.
The SSIV package will be installed on the export pipeline from the new Tuna platform to an existing pipeline connecting the TNW2 platform to the shore. A dedicated electro-hydraulic umbilical from the Tuna platform will control the actuator. Together with a check valve installed upstream of the ball valve, the SSIV will prevent any gas backflow in the event of a pipeline or riser rupture in the close proximity of the Tuna platform.