Vent sizing for fire considerations: external fire duration, jacketed vessels and heat flux variations owing to fuel composition

The methods for calculating heat flux to a vessel exposed to fire are well documented. API RP 520, 521, Standard 2000 and NFPA 30 are the basic indust ry guidelines providing correlations to calculate this heat flux. Other gui delines are available for less general cases. Given the heat flux, a reliev ing rate can be calculated to prevent vessel damage caused by over pressure . Considering the height and geometry variables, heat flux is calculated ba sed on the exposed vessel wall area that is wetted by internal liquids. Som e add a contribution owing to heat flux through unwetted surfaces. The above references provide guidance for the basic cause of calculating ex ternal fire heat flux to a typical vessel for the purpose of vent sizing. T he following paper provides guidance for the three special external fire ca ses. The authors believe that these three cases are not addressed in the Co des or elsewhere, thus justifying their presentation here. These papers wer e presented in summary at the 2000 DIERS Users Group meetings. (C) 2001 Els evier Science Ltd. All rights reserved.