Gas Pressure Regulators

Gas Pressure Regulators

Topics Covered: • Introduction to Gas Pressure Regulators

• The three operating elements of a regulator.

• Analysis of Operation

• Types of Regulators

• Sizing the Gas Pressure Regulator

Gas Pressure Regulators

• The purpose of the gas pressure regulator is to maintain a constant downstream gas pressure.

• The pressure regulator reduces an upstream pressure to a desired downstream pressure.

• In the operating range of the regulator, it will maintain the set downstream pressure, regardless of the changes in gas flow or inlet pressure.

The Three Operating Elements of a Regulator

• Gas pressure regulators have three main operating elements that work together in providing the pressure control action of the reg.

• The loading element usually takes the form of a regulator spring, the pressure setting of the spring is equal to the downstream pressure setting.

• An increase in spring pressure takes a higher downstream pressure acting underneath the diaphragm, to rebalance the regulator.


• The measuring element is usually a neoprene diaphragm.

• The diaphragm measures the changes in the downstream condition and responds to position the valve.

• The restricting element (valve) moves in response to the diaphragm which counteracts the change, thus returning the downstream pressure.


• The restricting element is the valve part of the regulator, it is actuated by the measuring element.

• An increase or decrease in the downstream pressure will cause the valve to either open or close, depending on the desired effect required.

• Closing of the valve will reduce the downstream pressure, opening the valve increases the downstream pressure.

The Gas Pressure Regulator

•#1 = Spring Adjustment Screw •#2 = Spring •#3 = Diaphragm •#4 = Valve Stem •#5 = Vent •#6 = Upstream •#7 = Downstream •#8 = Valve

Types of Regulators • There are basically two types of pressure

regulators in the utilization of natural gas, the appliance regulator and the service regulator.

• The appliance regulator reduces the upstream pressure from 7-14”wc to the required downstream manifold pressure of 3.5”wc at the burner.

• The appliance regulator is located at the start of the burner valve train assembly.

Types of Regulators • There are basically two types of pressure

regulators in the utilization of natural gas, the appliance regulator and the service regulator.

• The appliance regulator reduces the upstream pressure from 7-14”wc to the required downstream manifold pressure of 3.5”wc at the burner.

• The appliance regulator is located at the start of the burner valve train assembly.

Low Capacity Appliance Regulators

• Low capacity type appliance regulators are designed to provide safe and uniform gas pressure to residential gas appliances.

• Regulators can have both main burner load, and main burner and pilot burner load applications.

• Low capacity type appliance regulators with main and pilot duties, are specifically designed to give pressure control to tiny pilot flows that are an essential operating part of the appliance.

High Capacity Appliance Regulators

• High capacity type of appliance regulators are used on larger residential and commercial appliances.

• Usually these appliances regulators are of the straight-thru-flow design.

• Straight-thru-flow regulators have been widely accepted in the industry, because of their low friction flow resistance results in greater flow capacities for a given size regulator.

As a Component of a Gas Control Valve

• The appliance regulator is often used as a component of a combustion control valvetrain.

• The valvetrain provides the same function as the low capacity appliance regulator.

• The only difference in the valvetrain is that it is physically a part of a combination control valve assembly.

Outlet Pressure Adjustment • Appliance regulators can be either the limited or

variable adjustment type.

• Limited adjustment type appliance regulators are usually factory set at an outlet pressure of 3.5”wc and are adjustable .5”wc from the factory setting.

• Variable adjustment type appliance regulators are equipped with regulator springs that can give an adjustment to the outlet pressure depending on the spring range of the regulator 3-6”wc or 2-5”wc

Outlet Pressure Adjustment • Outlet pressure adjustments can only be

attempted when there is sufficient inlet pressure.

• The minimum required inlet pressure for outlet pressure adjustments is 1”wc above the maximum adjustment range of the spring.

• Adjusting the outlet pressure when there is insufficient inlet pressure available, could overfire the appliance if the inlet pressure were to rise.

Appliance Regulator Accessories

• Appliance regulator accessories are used to improve the operating characteristics of the reg.

• The surge arrester induces soft lighting, controls flame roll out and maintains pilot flame stability.

• The surge arrester is mounted in the regulator vent boss, and causes the regulator to open slowly and close normally.


• The vent limiting orifice is usually machined from brass.

• The vents purpose is to allow equal limits of inhalation and escape of air from the upper diaphragm chamber.

• In the event that the diaphragm does rupture, the leakage is limited to less than 1 ft3/hr at 7”wc gas pressure.


• Automatic safety vent limiting device, a ball check permits free inhalation of the regulator for fast regulator-diaphragm response.

• The ball check also automatically limits gas escape to safe limits should a diaphragm rupture.

• This device gives sensitive response even at low inlet pressure.

Service Regulators • The service regulator is located at the gas meter

inlet and reduces the upstream gas service line pressure in PSI to 7-14”wc houseline pressure.

• The linkage provides the connection between the diaphragm and the valve.

• Movement of the linkage, as actuated by the diaphragm, will open and close the valve.

Service Regulators • The orifice restricts the gas flow through the

regulator.

• In conjunction with the valve, the orifice controls the flow of gas through the regulator.

• The orifice is sized according to the customer ‘s total ft3/hr demand, and the upstream and downstream pressure conditions.

• The Vent allows the regulator to breathe.

Service Regulators • The valve seat is made of a soft material providing

100% shut-off when the valve is closed, preventing and gas flow through the orifice.

• Some service regulators can have the following

available features.

• Internal Safety Relief (IRV) • Lock-off Mechanism

Lock-off Mechanism • Service regulators with a lock-off mechanism are

equipped with an additional seat.

• The additional seat is designed to close, shutting off the flow of gas through the regulator, if the outlet pressure is too high or too low.

• If the regulator locks off under these conditions, it must be manually reset.

Positive Shut-off • Service regulators provide a positive shut-off

when no flow is occurring in the line to the appliances.

• The service regulator will usually lock-up to within 10% of the original outlet pressure setting.

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Gas Pressure Regulators