“GAS FACTS & RULES OF THUMB”
Not intended for use as engineering criteria
GAS IS COMPRESSIBLE AND ITS VOLUME IS AFFECTED BY BOTH PRESSURE AND TEMPERATURE
Information Required to Select Gas Regulators and Flow Meters
- Flow rate of gas expressed in CFH or BTU/hr.
- Inlet pressure of gas flowing into the regulator/flow meter.
- Regulated or desired outlet pressure leaving the regulator.
- Flowing media (i.e. Natural Gas, Propane Gas, Compressed Air, etc) and physical properties if other than common gases.
- Line size of the piping system in which the regulator or meter will be installed.
- Desired mechanical or electrical characteristics coming from the flow meter (i.e. Pulse, Current, or Voltage Relative to Flow Rate.)
Gas Pressure Regulator Venting
(TO BE USED AS A GENERAL RULE OF THUMB ONLY)
- Use the same size or larger pipe as the vent connection on the regulator. Vent piping runs should be kept as short as possible with limited bends and elbows.
- For every fifteen feet of straight pipe run beyond the first ten feet from the regulator increase vent line size 1 nominal pipe size back to the regulator vent connection. 1 pipe elbow = 5 feet of straight pipe run.
- Never vent multiple regulators together with the same vent line.
- Note: Special care is required not to screw vent piping too deeply into the vent connection. This can cause improper vent operation.
- Line size of the piping system in which the regulator or meter will be installed
- Desired mechanical or electrical characteristics coming from the flow meter (i.e. pulse, current, or voltage relative to flow rate
Useful Conversions & Definitions
1 PSIG = 27.68 inches Water Column (WC)
BTU = British Thermal Unit
1 MSCFH natural Gas = 1,000 SCFH
1 Standard Cubic Foot of natural Gas = 1,000 BTU’s
1 Cubic Foot of Propane Gas = 2,500 BTU’s
1,000 BTU’s = 1 CFH (Cubic Feet per Hour)
1 Unit of Natural Gas = 10 Therms = 1,000 BTU’s
1 Boiler Horse Power = 42,000 BTU Input (Assumes 80% Efficiency)