, "Pressure-relieving and Depressuring Systems," is the primary engineering benchmark for protecting process equipment—such as vessels and piping—from catastrophic overpressure events. The latest 7th Edition (June 2020) provides updated guidelines for refineries, petrochemical plants, and LNG facilities. 1. Scope and Application
To protect personnel and assets by preventing equipment failure and ensuring safe discharge to the environment or disposal systems.
API 521 applies to a wide range of industrial environments where high-pressure operations are common.
Primarily oil refineries, but also includes petrochemical, gas, and LNG production facilities.
It specifically does not apply to direct-fired steam boilers. 2. Principal Causes of Overpressure
The standard details credible scenarios that lead to unsafe pressure buildup, requiring engineers to design for "worst-case" events. API Standard 521