Optimization of recertification intervals for PSV based on major accident risk

Overpressure is a major hazard in the process industry with the potential to lead to a major accident. Pressure Safety Valves (PSVs) are often used as the last layer of protection against such a hazard and require regular recertification in order to be dependable. The valve safely vents gas from a vessel when the pressure becomes excessive. It is often the practice in industry to apply one or two years as the normal recertification interval of PSV. However, experience from the Norwegian oil and gas industry is that the recertification process several times have caused leaks of gas. The process thus represents a certain risk in itself and the question is then whether the recertification intervals presently being used actually are optimal from a risk point of view? The objective of this paper is to look into this problem, applying typical data from an oil and gas installation. An optimal recertification interval will be calculated based on minimization of risk to personnel.