Pressure Relief Requirement During External Pool-Fire Contingency
By Santosh Arvind Katkar Jacobs Engineering Group Inc. |
Relief system design is an important engineering activity throughout the chemical process industries (CPI). The main purpose of this task is to design a system that protects process equipment and piping against all possible causes of overpressure. It should relieve the excess pressure safely so as to protect personnel working in the facility from accidents, prevent damage to equipment and adjoining property, and comply with government regulations.
The principle causes of overpressure and guidance of plant design to minimize the effect of these causes are discussed in-depth in API STD 521 . Among these causes, the external pool fire is a contingency that is very complex and dynamic in nature. (A pool fire is a turbulent diffusion fire burning above a horizontal pool of vaporizing hydrocarbon fuel where the fuel has zero or low initial momentum.) Although it is very difficult to cover every aspect of this contingency, important aspects are presented in this article for non-reactive systems. Reactive systems are beyond the scope of this article and interested readers should refer to DIERS Methodology . A sample calculation and modeling results using commercial software are also presented at the end of this article.