(54co) Facility Siting, Closing the Gaps

History has seen numerous process safety disasters with catastrophic damage to nearby buildings, resulting in loss of life and property, documented in the literature with some still under investigation. In these disasters, the poor arrangement of equipment within a facility contributed to the magnitude of the disaster.

Despite stern lessons from the past, PSM regulations provide uncertain requirements. PSM require acknowledging or considering facility siting (FS) on their process hazard analysis (i.e. HAZOP), but does not provide a clear guidance on what is a proper approach to consideration and what is adequate. FS can be easily overlooked or even not considered during design; application of corporate siting decisions can be made by compliance exposing operators to unnecessary risk. In many cases FS decisions are considered during late project stages, even after the intended permanently occupied buildings are already in place and mitigation measures are extemporaneous or budget prohibitive.

The American Petroleum Institute (API) and the Center for Chemical Process Safety (CCPS) has invested significant effort in develop API RP-752/753 guidelines and literature. Although these resources provide a good starting point and a sound process via practical flowcharts, the recommended practices leave a lot of room in the selection of adequate technical methods needed to complete the assessment; this is a gap particularly when required answers call for quantitative event simulation and frequency calculation.

For example, once the API screening flowchart is applied, and qualitative assessment is completed; but the building does not meet siting criteria for explosion or toxic, what next? How detailed should the detailed analysis be? Can radiation and blast loads be determined without a full blown quantitative risk analysis (QRA) that is in most cases budget prohibitive? How much of sound analysis can be can be done with a constrained budget? In absence of benchmark public industrial development individual/risk criteria, are there local/corporate siting decision criteria for decision making?

An overall optimized quantitative method is discussed in this paper including four stages. It can be applied for a variety of process and multiple facilities and scope can be managed (i.e. when to stop and what to evaluate). This approach is flexible and cost-effective as it allows screening-out what does not contribute to risk and makes the most of the qualitative assessment, reducing the scope of computational stages.