Value of Condition Monitoring Data in Safety Management Decision Support

Jeeves, Simon (MRC Global Norway AS)



ValveWatch can be a powerful tool as part of an operational strategy, as it provides valuable information that can be used to track operational Safety according to IEC 61511/508 (Functional Safety Assessment - SIL – Safety Integrity Level).

Within an operating plant, Functional Safety Management for automated on/off valves, PSVs and manual valves it is required to understand why the valves fail and how it is possible to mitigate these failures. The common factor is that the Faults that one has experienced i.e the valve/actuator has failed to carry out its intended task has caused a loss in production or a reduced the level of safety that the plant has been operating under. – These are expensive lessons and lessons that are repeated often.

The reason why these "lessons" get repeated is because the failures that have been experienced are due to hidden failures that are not possible to discover with traditional instrumentation (I.e limit switch, Partial Stroking, opening/closing time). In the terms of IEC 61508 these faults are categorized as DU Faults (Dangerous Undetected). Often these faults may have been introduced due incorrect maintenance, incorrect operation of the valve/actuator or simply due to wear and tear.

Critical valves have requirements with respect to functional testing and also perhaps through leakage tests. The manual methods in testing are flawed and it is difficult to uncover the DU's and even the DD (Dangerous Detectable Faults). Furthermore, the manual tests are often carried out when there is no pressure present, hence the valve is not tested under realistic conditions.