What are the effects of changing the test interval of land based safety critical valves in hydrocarbon transport systems

Abstract

In this master thesis, the effects of changing the test interval of the land based safety critical valves have been highlighted. Compliance with the regulations given by the PSAN (Petroleum Safety Authority Norway) requires annual testing of these valves. The testing of safety critical valves are essential to increase the probability that the valves are able to conduct intended functions, and beneficial to improve safety and regularity. Moreover, "Too often" testing can lead to unnecessary production loss, with major economic consequences, and the danger/risk of test-induced errors. "Too less" testing can lead to the valves failure, which in a result could have major consequences in relation to safety and long downtime during repairs. There are a number of test methods (differential pressure test, partial stroke testing etc.) used for different safety critical valves, because Valve design, the consequences of downtime, environmental aspects of the testing, etc. varies between different safety critical valves. The choice of inappropriate test regimes can lead to unnecessary downtime and environmental emissions in testing. Thus these different test methods have great influence on the effects of changing the test interval of the safety critical valves. It is not simple and easy to clarify and conclude, which case of changing the test interval is more appropriate in connection with all the effects related to the change of test interval of these valves. As there are many factors (degradation mechanism, failure modes, testing methods, regularity, production effects) which needs to be deeply analyzed and evaluated for future research.