Various approaches are presented to protect storage tanks from fire exposure. Design techniques for emergency relief devices flowing vapor or two-phase vapor-liquid flow are discussed. The effects of maximum design pressure versus emergency relief device set pressure, fire exposure insulation and water spray protection, fire exposure duration, relief device flow characterization and inlet pipe pressure drop and discharge pipe back pressure must all be considered when designing to protect storage tanks.

This paper discusses some aspects of pressure relief design for low pressure storage tanks. The concepts and techniques discussed here can be modified to include design guidance/recommended design parameters from specific standards. Even if not used for pressure relief design, the concepts/calculations presented should be useful for Process Hazard Analysis studies to determine the relative ranking of credible scenarios.

The reader is cautioned that no attempt was made to cover every design situation or conform to any design standard/recommended practice. There are too many specific scenarios and too many (unnecessary) conflicts between standards/recommended practices. Instead, the reader is cautioned to ensure that all prescribed federal, state and local as well as company design standards are followed when mandated.