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

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**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.

- Enter the upstream pressure
- Enter the required permanent pressure loss across the orifice
- Enter the fluid density, viscosity and ratio of specific heat capacities
- Enter the required flow rate through the orifice
- Enter the internal diameter of the pipe in which the orifice will be installed
- Click the "Calculate" button
- The calculator will determine the orifice diameter required to give the required flow rate and pressure loss
- 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

- The Beta ratio must be less than 0.8 for the orifice design to be acceptable
- If the Beta ratio is calculated to be outside of this range a warning message will be displayed
- If Beta ratio > 0.8:
- Increase pressure loss across orifice
- Increase the pipe internal diameter
- Reduce the flow rate