Design and Protection of Pressure Systems to Withstand Severe Fires

Abstract

Mitigation of the impact of severe fires on hydrocarbon processing plant is critical to minimizing the risk to personnel, reducing damage and limiting capital loss. It is recognized that current experimental data and the associated model validation are mainly confined to the response of vessels containing liquefied petroleum gas. Models for predicting the behaviour of vessels containing multicomponent fluids (with or without emergency depressurisation) under severe fire loads exist. However, relatively little validation has been performed. Currently, industry tends to use the American Petroleum Institute's Recommended Practices 520 and 521 for the design of pressure-relieving systems to withstand fire conditions, but these are only applicable to some of the less severe, hydrocarbon pool-fire scenarios. Under the auspices of the Institute of Petroleum and with the support of the Health and Safety Executive, interim guidelines have recently been published. They are intended to assist design and process engineers concerned with large, essentially fully enveloping pool fires and jet-fire impingement on pressure vessels and their associated pipework. The guidelines are intended for use primarily for designing new facilities and specifically deal with fires that are more severe than the open pool fires currently covered by API guidance. This paper considers the guidance in the API recommended practice and the new Institute of Petroleum guidelines and compares the approaches with data from hydrocarbon pool and jet-fire trials on filled propane vessels.