How do I prevent safety valves from sticking and creating an explosion risk?
Published: 03 January, 2017
The answer to this month’s trouble shooter is provided by Sam Thiara, Emerson Automation Solutions.
A question often asked of safety valves is will they operate correctly when needed? Safety valves will often sit idle (wide open) for long periods because the safety function is not often called upon. Over time this can lead to a mechanical failure, with the valve ‘sticking’ in its open position and creating a significant risk to plant, equipment and people.
The practice of performing safety valve testing can often be cumbersome, especially for older systems, which require pin retainers, pneumatic local panels and bypassing. However, with valves and their associated control and actuator systems now offering a high degree of embedded intelligence and data logging capabilities, carrying out a safety demand on the safety valve has become much easier.
Digital valve controllers enable online partial stroke testing (PST) of valves, reducing the probability of failure. This can lead to an increase in the safety integrity level (SIL) where the valve is applied. Digital valve controllers also provide auditable PST results, which supports the overall manufacturer’s safety lifecycle documentation requirements.
In addition, to help reduce the probability of failure on demand (PFD), digital valve controllers provide a range of diagnostics and alerts, such as stuck valve indication, low supply pressure, valve travel, shaft integrity, travel and pressure deviation. Digital valve controllers also provide a means to test the integrity of the solenoid valve plungers, which can often remain undetected. Users can adopt digital valve controllers in a scalable way by implementing only a small number to start with.
Digital valve controllers represent the fundamental building blocks of the Industrial Internet of Things (IIoT). Data gathered from the controllers can then be proactively monitored and analysed to prevent an explosion risk.