Pressure Regulator
Operation
Single-stage pressure regulator
Two-stage pressure regulator
A pressure regulator’s primary function is to match the flow of gas through the regulator to the demand for gas placed upon the system. If the load flow decreases, then the regulator flow must decrease also. If the load flow increases, then the regulator flow must increase in order to keep the controlled pressure from decreasing due to a shortage of gas in the pressure system.
A regulator includes a restricting element, a loading element, and a measuring element:
The restricting element is a type of valve. It can be a globe valve, butterfly valve, poppet valve, or any other type of valve that is capable of operating as a variable restriction to the flow.
The loading element applies the needed force to the restricting element. It can be any number of things such as a weight, a spring, a piston actuator, or more commonly the diaphragm actuator in combination with a spring.
The measuring element determines when the inlet flow is equal to the outlet flow. The diaphragm is often used as a measuring element because it can also serve as a loading element.
In the pictured single-stage regulator, a diaphragm is used with a poppet valve to regulate pressure. As pressure in the upper chamber increases, the diaphragm is pushed upward, causing the poppet to reduce flow, bringing the pressure back down. By adjusting the top screw, the downward pressure on the diaphragm can be increased, requiring more pressure in the upper chamber to maintain equilibrium. In this way, the outlet pressure of the regulator is controlled.
Applications
Oxy-fuel welding and cutting
Oxy-fuel welding and cutting processes require gases at specific pressures, and regulators will generally be used to reduce the high pressures of storage cylinders to those usable for cutting and welding. Oxy-gas regulators usually have two stages: The first stage of the regulator releases the gas at a constant rate from the cylinder despite the pressure in the cylinder becoming less as the gas in the cylinder is used, as in the first stage of a scuba-diving regulator. The second stage of the regulator controls the pressure reduction from the intermediate pressure to low pressure. It is constant flow. The valve assembly has two pressure gauges, one indicating cylinder pressure, the other indicating hose pressure.
Propane/LP Gas
All propane and LP Gas applications require the use of a regulator. Because pressures in propane tanks can fluctuate significantly, regulators must be present to deliver a steady flow pressure to downstream appliances. These regulators compensate for tank pressures in excess of 200 psig and commonly deliver 11 inches water column for residential applications. Propane regulators differ in size, delivery pressure and adjustability but are uniform in their purpose to deliver a constant outlet pressure for downstream requirements. As is the case in all regulators, inlet pressure is higher than outlet pressure.
Recreational vehicles
For recreational vehicles with plumbing, a pressure regulator is a necessity. When camping, a source of water may have an enormous pressure level, particularly if it comes from a tank that is at a much higher elevation than the campground. Water pressure is dependent on how far the water must fall. Without a pressure regulator, the intense pressure encountered at some campgrounds in mountainous areas may be enough to burst the camper’s water pipes or unseat the plumbing joints, causing flooding. Pressure regulators for this purpose are typically sold as small screw-on accessories that fit inline with the hoses used to connect an RV to the water supply, which are almost always screw-thread-compatible with the common garden hose.
Breathable air supply
Main article: Diving regulator
Pressure regulators are used with air tanks used for breathing during SCUBA diving. The tank may contain pressures well in excess of 2000 PSI, which could cause a fatal barotrauma injury to a person breathing it directly. A regulator allows only a sustained flow of air at 14.7 psia.
Mining industry
As the pressure builds rapidly in relation to depth, underground mining operations require a fairly complex water system with pressure reducing valves. These devices must be installed at a certain distance interval, usually 600 feet. Without such valves, pipes would easily burst and pressure would be too great for equipment operation.
References
http://www.irwd.com/WaterQuality/pressure.php
External links
XB-70 How a pressure regulator works (PowerPoint)
Categories: Plumbing valves | Hydraulics
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