What is the basis for the required relief valve orifice size in CGA S1.3, Pressure Relief Device Standards-Part 3-Stationary Storage Containers for Compressed Gases?

Equation 6.3.1.1 in CGA S1.3 is based on modeling to API methods described in: Heitner, T. Trautmauis, and M. Morrissey, “Relieving Requirements for Gas Filled Vessels Exposed to Fire,” 1983 Proceedings-Refining Department, Volume 62, American Petroleum Institute, Washington, D.C., pp. 112-122.

This method considers the transient nature of the vessel warming in combination with the venting of the vessel. It also includes the inherent delay in the gas temperature increase over time. This approach is used as the basis for CGA S1.3 and has proven valid for industrial gas and related vessels.