How to monitor your safety instrumented system performance

Abstract

With the impending release of Edition 2 of the International Electrotechnical Commission (IEC) Standard 61511 in Australia, it is timely to revisit the topic of safety instrumented system (SIS) performance monitoring. Operators need to monitor the performance of their SISs to ensure that design assumptions are correct. Any incorrect assumption or error introduced during operation can result in an unsafe plant situation. Questions to consider include: how do operators know their plants are adequately protected; are protection systems performing as required, and do operators need to re-assess the safety of their plant’s process vis-à-vis the implemented safety instrumented systems; what are end-user obligations; how and is it possible to meet these obligations; and what additional requirements are there, and how much more prescriptive is Edition 2? If any of the above questions are of concern, or if plant personnel are aware of their obligation to maintain and monitor the SIS during operations but are still not 100% sure if they are on the right track or need to do more, then this paper will prove useful. In addition to knowing all the requirements to comply, actual implementation and maintenance of a program to monitor the performance of SIS can prove overwhelming. Not only do you need to be adept in maintaining a database, but you also need to understand how to consolidate various critical information sources in order to make sense of all the data collected. Fortunately, there are solutions in the market to help end-users overcome these hurdles to effectively monitor SIS performance. This paper looks at some key areas that a complete solution should cover and what some of the features of such a solution are.