Restrictive flow orifice

  1. Control devices
  2. Gas technologies


A Restrictive Flow Orifice (RFO) is a type of orifice plate. They are used to limit the potential danger of an uncontrolled flow from a compressed gas cylinder by:[1][2]

  1. limiting the accidental release of a hazardous gas (flammable, toxic, etc.) resulting from regulator or other component failure,
  2. restricting flow in a system in order to assure adequate pressure relief valve sizing and system over pressure protection, or
  3. restricting flow from bulk sources.[3]

Predicting Flow

Correlations assist in predicting the flow of a particular gas or gas mixture through a RFO. This is done by first determining the flow through the same RFO at the required pressure with a reference gas and then adjusting the specific gravity accordingly.

The pertinent equation for the reference gas of nitrogen (N2) is presented below.

\(Flow = \text{Flow Rate of N2 at the same pressure} * \sqrt{\frac{1}{\text{Specific Gravity}}}\)

Notes

  1. ↑ Matheson, Restrictive Flow Orifice accessed Sep 2011
  2. ↑ RFO Stanford accessed Sep 2011
  3. ↑ Gas Flow Characterization of Restrictive Flow Orifice Devices, Sandia REPORT SAND97-1670, Jul. 1997


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