Imtex Controls: Safety Implications of Separate ESD SOV and PST SOV in Valve Systems

In valve systems, ensuring safety is paramount, with reliability and efficiency being key factors. The practice of utilizing separate Emergency Shutdown (ESD) Solenoid Operated Valves (SOV) and Partial Stroke Testing (PST) SOVs can introduce critical safety concerns that could affect the performance of the shutdown valves. 

Factors to consider are:

• Lack of Integration: ESD SOVs, designed for emergency shutdowns, are often not included in Partial Stroke Testing procedures. This means that during routine testing, the ESD SOV element remains untested, potentially harbouring undetected faults or failures.
• Compromised Safety: The absence of ESD SOV testing within the PST procedure undermines the comprehensive assessment of the entire valve system. Any faults or failures within the ESD SOV could go unnoticed until an actual emergency, jeopardizing safety protocols and increasing the risk of catastrophic incidents.
• Operational Impact: Operating with separate ESD and PST SOVs introduces complexity and increases the likelihood of both equipment failure or human error that could take the valve offline to fix, affecting production.
• Prolonged Unplanned Plant Shutdowns: Any undetected failure in the ESD SOV that is only identified during an emergency could lead to prolonged shutdowns, impacting production and exacerbating safety risks. 

Solution

Simplifying PST implementation and utilising the ESD Solenoid itself to deliver PST reduces the risk that a shutdown valve might fail to deliver during a safety demand. PST run via the ESD SOV tests the whole valve system that forms the final element of the Safety Instrumented System in the same way that it would operate under an actual safety demand. It also has the additional benefit of exercising the solenoid valve, making it more likely to perform as required during a shutdown.

This is the concept employed by the Valvescan Type V Smart Controller from Imtex Controls Limited. PST is delivered using the Valve System solenoid valve in combination with data collection and analytics technology to provide accurate insight into likely valve performance during an actual ESD demand and to identify likely areas of concern. 

By consolidating the ESD and PST functions through the same SOV, users gain an enhanced understanding of system health, enabling proactive maintenance and ensuring robust emergency shutdown capabilities.

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