(46b) Common Misunderstanding of Overpressure Protection Scenarios for Pressure Relief Valves

Most of process engineers developing reief load scenarios of a pressure relief valve commonly misunderstand some concept of relief load scenarios. For instance, a credit of safety trip interlock is usually taken in stead of considering relief load scenario without Layer of Protection Analysis (LOPA) for the protected system, or neglecting control valve failure scenario in both fully closed and fully opened position. The latter is also usually mixed up with the instrument air failure scenario. Therefore, this presentation has summarized and highlighted the following misconception of relief valves sizing;

• What is a relation between Layer of Protection Analysis (LOPA) and Relief Load Scenarios Consideration?

• How to identify whether overpressure scenarios is applicable or not for the protected system?

• What is a difference between control valve failure and instrument air failure?

• Is a relief valve required for every pressure vessel?