Gas Restriction Orifice Plate Sizing Calculator

This calculator determines the orifice diameter required to restrict the flow rate of gas or vapour in a pipe using a sharp edge restriction orifice plate.

Gas ROP Sizing Calculator Guide

Show Instructions

The calculator determines the orifice size required to restrict the flow of a gas or vapour through a pipe.

The calculation is based on the method described in Crane Technical Paper 410M.

The orifice flow coefficient is determined automatically.

  1. Enter the upstream pressure
  2. Enter the required permanent pressure loss across the orifice
  3. Enter the fluid density, viscosity and ratio of specific heat capacities
  4. Enter the required flow rate through the orifice
  5. Enter the internal diameter of the pipe in which the orifice will be installed
  6. Click the "Calculate" button
  7. The calculator will determine the orifice diameter required to give the required flow rate and pressure loss
  8. The calculator will also determine:
    • Orifice velocity head loss coefficient
    • Beta ratio of the orifice (orifice diameter:pipe internal diameter)
    • Pipe Reynolds number
    • Orifice flow coefficient
    • Pressure difference across orifice (upstream pressure - vena contracta pressure)
    • Orifice flow area
    • Pressure ratio of the vena contracta pressure to the upstream pressure
    • Net expansion factor of the gas
  9. The Beta ratio must be less than 0.8 for the orifice design to be acceptable
  10. If the Beta ratio is calculated to be outside of this range a warning message will be displayed
  11. If Beta ratio > 0.8:
    • Increase pressure loss across orifice
    • Increase the pipe internal diameter
    • Reduce the flow rate


ROP Sizing Diagram