Supplier of valves and actuator control systems, Midland-ACS, is helping a North Sea oil producer to avoid costly downtime with the launch of the OPD Stemsaver. The device, said to be an industry first, is a high-integrity pressure regulator for the pneumatic control systems widely used for valve actuation in the oil, gas and other processing industries
The OPD Stemsaver, guards against any failure of the filter-regulator that controls compressed air system pressure, by providing dual-redundant over-pressure protection. It ensures any downstream actuators for controlling process valves cannot be accidentally exposed to dangerous over-pressures that could be high enough to shear a valve stem or cause other damage. The device provides plant and automation engineers with a high integrity safeguard against a failure mechanism that could lead to a costly process shutdown or injury.
Pneumatic actuation is widely used in process automation systems for controlling and sequencing valves. Automated control valves are common in hazardous areas, such as offshore platforms and refineries. There may be as many as 1,000 actuated valves on an offshore platform for example.
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 goes into ensuring the actuators controlling these valves are reliable in an emergency, pneumatic actuation systems typically use a single filter-regulator component, and the failure of this can expose downstream devices to pressures two or more times the norm. This can cause significant damage, even providing an actuator with enough torque to shear a valve stem.
Midland-ACS, represented in Ireland by Walsh Industrial Sales, developed OPD Stemsaver following a request from an engineering, procurement and construction firm working for a North Sea oil producer. A failed filter-regulator led to the cover of a pneumatic actuator being blown off, leading to costly downtime. The OPD Stemsaver design avoids this possibility by providing a dual-redundant pressure regulation facility with one diaphragm regulator, coupled to a spring-tensioned poppet valve. The use of these two regulation mechanisms provides added reliability.
As standard, OPD Stemsaver can be set to regulate pressure in the 4-8 bar (58-116 PSI) range. It is supplied as a single compact unit, fabricated in 316 stainless steel. 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.
Midland-ACS has produced around 100 of the new high-integrity over-pressure protectors for its first offshore platform client. These have been installed over several months to improve the integrity of the platform’s network of remote control valves.
“If a valve actuator fails, it can easily lead to downtime or even a plant shutdown, and for continuous processes such events can be extremely costly,” says Derek Clure of Midland-ACS. “OPD Stemsaver provides a practical and economic solution that could benefit thousands of plants worldwide.”
OPD Stemsaver is available an individual component. It is also compatible with the company’s modular pneumatic control manifold – IMpact. This is a universally compatible interface block that mounts directly onto valve actuators, and accepts a range of field-proven pneumatic components.