08 March 2011
Called OPD Stemsaver, the device is said to guard against failure of the filter-regulator that controls compressed air system pressure, by providing dual-redundant over-pressure protection. It ensures that any downstream actuators for controlling process valves cannot be accidentally exposed to over-pressures that could be high enough to shear a valve stem or cause other damage. The device is an industry first, and provides plant and automation engineers with a high integrity safeguard against a failure mechanism that could lead to a costly process shutdown or injury.In hazardous areas, actuated valves are often elements of a plant's emergency procedures, such as the safety instrumented system (SIS) that controls emergency shut down (ESD). Depending on the emergency and type of process, valves may be automatically closed – to stop media feeding a fire for example – parts of the plant may be isolated, or media might be vented to atmosphere, via an emergency system vent (ESV). Although considerable safety design effort goes into ensuring that the actuators that control these valves can be relied on in an emergency, pneumatic actuation systems typically use a single filter-regulator component, and the failure of this component can expose downstream devices to pressures as high as two or more times the norm which is enough to cause significant damage, even providing an actuator with enough torque to shear a valve stem. OPD Stemsaver was developed following a request from an engineering, procurement and construction firm working for a North Sea oil producer. A failed filter-regulator had led to the cover of a pneumatic actuator being blown off, leading to costly downtime of operations. As standard, OPD Stemsaver can be set to regulate pressure in the 4-8 Bar range. The device is supplied as a single compact unit, fabricated in 316 stainless steel to meet the anti-corrosion requirements of environments such as offshore platforms, and process plants handling harsh media. In use, the secondary regulator is set to operate at a slightly higher pressure than the primary regulator. If the secondary regulator is activated, a reset button also automatically pops up. This can be linked to a proximity switch, to provide feedback to the plant's distributed control system (DCS).
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