# Category Archives for **Relief Valve Sizing**

## Two-Phase Flow Standard Sizes

Two-Phase Flow There are no precise formulas for calculating orifice area for twophase flow. The common convention is to calculate the area required for the gas flow as if there were no liquid present and the area required for the … Continue reading

## Liquids Flow Rate

Conventional Valve, Balanced-Bellows Valve, or Pilot-Operated Valve The corresponding equations for liquid flow are the following: Note that a preliminary orifice size must be determined in order to calculate Reynolds number. If the viscosity correction is significant, it may be … Continue reading

## Orifice Gas Flow Rate

The flow rate for gas through a given orifice area or the area required for a given flow rate is obtained by:

## Effects of Back Pressure

Back-pressure can affect either the set pressure or the capacity of a relief valve. The set pressure is the pressure at which the relief valve begins to open. Capacity is the maximum flow rate that the relief valve will relieve. … Continue reading

## Critical Flow

The flow of a compressible fluid through an orifice is limited by critical flow. Critical flow is also referred to as choked flow, sonic flow, or Mach 1. It can occur at a restriction in a line such as a … Continue reading