Safety Implications of Separate ESD SOV and PST SOV in Valve Systems

In valve systems, safety is of utmost importance, with reliability and efficiency being crucial elements. The use of separate Emergency Shutdown (ESD) Solenoid Operated Valves (SOV) and Partial Stroke Testing (PST) SOVs can pose significant safety risks that may impact the performance of the shutdown valves.

Key Considerations:

1. Lack of Integration: ESD SOVs, intended for emergency shutdowns, are often excluded from Partial Stroke Testing procedures. This means that during routine tests, the ESD SOV component remains untested, potentially harboring undetected faults or failures.

2. Compromised Safety: Excluding ESD SOV testing from the PST procedure undermines a comprehensive assessment of the entire valve system. Any faults or failures within the ESD SOV could remain undetected until an actual emergency, endangering safety protocols and increasing the risk of catastrophic incidents.

3. Operational Impact: Using separate ESD and PST SOVs adds complexity and increases the likelihood of equipment failure or human error, which could take the valve offline for repairs, affecting production.

4. Prolonged Unplanned Plant Shutdowns: An undetected failure in the ESD SOV identified only during an emergency could lead to extended shutdowns, impacting production and exacerbating safety risks.

Solution:

Simplifying PST implementation by using the ESD solenoid itself for PST reduces the risk of a shutdown valve failing during a safety demand. Conducting PST via the ESD SOV tests the entire valve system that forms the final element of the Safety Instrumented System in the same manner as it would operate under an actual safety demand. Additionally, this approach exercises the solenoid valve, making it more likely to perform correctly during a shutdown.

This concept is implemented by the Valvescan Type V Smart Controller from Imtex Controls Limited. PST is delivered using the valve system's solenoid valve combined with data collection and analytics technology, providing accurate insight into potential valve performance during an actual ESD demand and identifying areas of concern.

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