API Standard 521: New Alternative Method to Evaluate Fire Relief for Pressure Relief Device Sizing and Depressuring System Design

The upcoming 6th edition of API Standard 521 will include an alternative, analytical method to evaluate fire exposure of vessels. The experimental basis and limitations of the existing empirical method will be given. The empirical and analytical methods will then be compared with additional pool fire test data including the 1999 tank car pool fire exposure test in Germany. Based on these comparisons, a modification to the existing empirical method will be given along with recommendations on the use of these methods to design pressure releif systems. The analytical method will then be applied to the design of depressuring systems to mitigate the effects of fire exposure of gas filled equipment.  The basis for the 15 minutes to depressure to 50% of the design pressure will be discussed and alternatve criteria provided.