Making Relief Load Estimates Match Reality

摘要

A pressure relief system designer must make some assumptions when looking at a reliefsystems analysis. Some assumptions may result in costly modifications of the system, soknowing when to apply certain assumptions is paramount with the ability to accuratelysize a relief valve. When looking at systems, industry standards should be consultedbefore taking certain credits based on the given scenario. For example, the designer maybe able to reduce the relief load by looking at a reduced reboiler duty and a temperaturepinch during an overpressure event. When evaluating an inlet control valve failure, somecredits may be taken for the minimum turndown for the outflow. However, when lookingat how a downstream system may respond to the overpressure event, credit for flowcontinuing may not be acceptable and flow may be assumed to be lost. The applicationof assumptions is common practice in relief systems analysis; however, an assumptionthat does not match the true operational limits may lead to problems with the reliefsystem that do not actually exist. These invalid assumptions could cost millions of dollarsto fix the problem.