API 521 Historical

This Guide presents recommended practices applicable to pressure-relieving and vapor depressuring systems. The information provided is designed to aid in the selection of the type of system that is most appropriate for the risk and circumstances involved in the various installations. It is intended to supplement the practices set forth in API RP 520 for establishing a basis of design. 

This publication provides guidelines for examining the principal causes of overpressure, for determining individual relieving rates and for selecting and designing disposal systems which include such component parts as vessels, flares, and vent stacks. 

Piping information pertinent to pressure-relieving systems is presented in 5.4.1; but the actual piping is to be designed in accordance with ANSI/ASME B31.3 or other applicable codes.