Monday 16 August 2010

Gas over oil pipeline actuator

The Shafer SH Series is designed for high reliability with a long service life and is ideally suited to critical applications

Emerson Process Management's Shafer™ SH Series of gas-over-oil valve actuators are ideally suited to automate valves used for gas transmission as well as at compressor stations, gathering plants, storage facilities, meter runs and many other applications. Designed for fifty years of operation, the actuator has a 15 year seal life and a ten year, industry-leading warranty.

The SH series actuator is operated by hydraulic oil, pressurised by the pipeline gas. Powering the actuator with oil prevents the internal corrosion associated with other actuator designs. The actuator is designed so that the gas is contained within two tanks, half filled with hydraulic oil. Contaminants and moisture in the gas settle to the bottom of the tank where they can be easily drained.

The actuators can be used for standard on/off service or as part of an Emergency Shutdown System (ESD). Three sizes of SH are available to suit DN 50 to 200 (2” to 8”) valves with a torque range between 254 Nm and 2034 Nm. Torque is evenly applied across the whole range of movement, making the SH Series ideal for plug and blowdown valves. The compact actuator package is operated by solenoid valves which are factory piped, ready for operation. A switch box provides open/closed feedback to the operator.

The helical spline technology contained within the actuator does not cause stem side loading, which other designs can be prone to do. Stem side loading can cause premature packing or seal wear and leakage. The SH series is powered by pipeline gas in the pressure range of 27.5 bar to 103 bar. It is also possible to operate the actuator manually when required, for example during commissioning or in situations where pipeline pressure is not available.

Maintenance requirements are minimal; the drain valve in the tanks needs to be opened periodically to remove the contaminants and water that have settled out of the gas. This should normally only be necessary once a year.

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