Pressure Regulation & Gas Metering
Gas pressure regulators, two-stage systems, manifold pressures, gas meters, shutoff valves, and excess flow protection.
- Explain the function and operation of gas pressure regulators
- Distinguish between natural gas and propane manifold pressures
- Describe two-stage regulation systems and their applications
- Identify gas meter types and their installation requirements
- Explain excess flow valve operation and shutoff valve requirements
Leçon 1
Gas Pressure Regulators & Operation
Why Pressure Regulation Is Required
Gas is delivered to buildings at pressures much higher than what appliances require. Pressure regulators reduce the incoming supply pressure to the manifold pressure that appliances are designed to operate at. Without proper regulation, excessive pressure would damage appliance controls, create dangerous flame conditions, and compromise safety.
Regulator Components
A gas pressure regulator contains:
- Diaphragm - senses downstream pressure changes
- Spring - sets the desired outlet pressure
- Valve seat and disc - controls gas flow
- Vent - relieves excess pressure (must vent to outdoors on indoor regulators)
- Adjustment screw - fine-tunes outlet pressure
Regulator Vent Must Be Protected
Indoor regulators must have their vent piped to the outdoors to prevent gas accumulation inside the building if the diaphragm ruptures. Outdoor regulators must have vents protected from water, insects, and debris with a screened vent fitting.
Lock-Up Pressure
Lock-up pressure is the pressure at which the regulator completely shuts off gas flow when no appliances are running. A properly functioning regulator should lock up within a few tenths of an inch water column above the set pressure. Excessive lock-up pressure indicates a worn or damaged valve seat.
Gas regulators reduce supply pressure to manifold pressure - 7" WC for natural gas and 11" WC for propane. Indoor regulator vents must be piped to outdoors. Lock-up pressure should be only slightly above set pressure.