HAZOP revalidation and focus on major accident hazards

摘要

Management of Major Accident Hazards (MAHs) is critical for long term sustainability of companies which use hazardous materials. ExxonMobil has a suite of Process Hazard Analyses (PHAs) which have been used successfully for many years to identify and mitigate risks. These are ongoing processes which are repeated, in order to ensure that existing hazards remain under control and to incorporate any new learnings in process safety. Recently ExxonMobil benchmarking has identified the need for us to focus on the health of critical safeguards to prevent MAHs. Analysis of our risk identification techniques has led us to introduce new and enhanced methodologies which target this area, as well as causing us to evaluate the current value added from repetition of prior PHAs. For units which have previously been through at least two Hazard and Operability studies (HAZOPs), there is increasingly less risk discovery when common techniques are utilised. An alternative approach is to identify changes since the previous HAZOP, and ensure that the associated hazards are known and adequately managed. This is particularly important for subtle changes, which can lead to degradation of the design safeguards. Review of changes since the last HAZOP coupled with trending of data associated with MAH Key Performance Indicators results in a study which is focused on the highest consequence events. Studies which use this approach have been found to result in a different risk profile, with a concentrated output which is focused on MAH. This "Delta HAZOP" approach focuses the site resources and activities on MAH prevention, partly due to a shorter overall resource commitment to execute this type of revalidation study.