Gas Leak Rate (Orifice)
Estimated leak rate from orifice diameter and upstream pressure.
Example
You enter
- Orifice diameter (in) 0.05
- Upstream gauge pressure (psi) 0.25
- Gas natural_gas
- Discharge coefficient 0.7
You get
- Leak rate 7.72 ft^3/hr
- Orifice area 0.00196 in^2
Checked against published worked examples from: Eclipse, Inc.
Details, formula, and sources
Formula or tableOrifice-flow leak estimate Q = 8706 * c * A * sqrt(dP / SG) (scf/h), the orifice equation Q = c A sqrt(2 dP / rho) in cfh, in^2 and psi (8706 = 25 sqrt(2 x 144 x 32.174 / 0.0764), air 0.0764 lb/ft^3), matching the compute. Estimation only, not an authoritative leak-rate calculation.
Source and editionClassical fluid mechanics; orifice coefficient typical from public engineering references.
Free accessNIST fluid-property tables free at nist.gov.
What governsEstimate. AHJ and licensed plumber / gas fitter govern. Verify against the IPC / IFGC edition adopted in your jurisdiction.
API field namesorifice_diameter_in, upstream_psi, gas, c, leak_rate_cfh, orifice_area_in2
- Discharge coefficient Cd 0.7 default (a rough-edged crack or fitting leak); 0.61 is the sharp-edged-orifice value; the user may enter eitherengineering practice
- Gas density at standard conditions from data/plumbing/gas-pipe-capacity.jsonengineering reference