Analyses of pressure relief systems are concerned with transient process disturbances that potentially cause overpressure of piping and mechanical equipment. The transient in pressure may be beyond that allowed by the relevant design code. Process disturbances typically include blockages in piping and vessel outlets, utility failure such as air and power, and uncontrolled process reactions. The aim of transient analyses is to determine the requirements for pressure relief, such that the effect of these disturbances is minimized or controlled. The integrity of equipment is maintained thereby providing a safe operating environment for personnel. An understanding of both the hydraulic and thermodynamic response characteristics of the process involved is fundamental to these analyses.