Download - Gas Pressure Regulators
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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
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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.
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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.
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The Three Operating Elements of a 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.
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The Three Operating Elements of a Regulator
• 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.
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The Gas Pressure Regulator
•#1 = Spring Adjustment Screw •#2 = Spring •#3 = Diaphragm •#4 = Valve Stem •#5 = Vent •#6 = Upstream •#7 = Downstream •#8 = Valve
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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.
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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.
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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.
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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.
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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.
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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
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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.
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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.
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Appliance Regulator Accessories
• 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.
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Appliance Regulator Accessories
• 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.
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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.
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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.
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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
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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.
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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.