Avoiding pitfalls in determining quantitative safety integrity levels for batch processes

An evaluation of a quantitative safety integrity level (SIL) for batch processes is not as straightforward as an evaluation for continuous processes. Because batch processes do not operate under steady conditions and involve frequent startups and shutdowns, the various factors considered for a quantitative SIL evaluation play a different role. This article discusses how these factors are affected by the operating characteristics of batch processes and suggests ways of avoiding errors in computing the SIL for batch processes. One example is presented to show what precautions are necessary to avoid possible errors in a quantitative SIL determination of batch processes.