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 air pressure regulator from decreasing due to a shortage of gas in the pressure system. A pressure 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.When the actuator is forced against an expansion disk, the force is distributed among the pressure walls. This allows the gas to flow at the proper rate and not to be continually vaporized and diluted.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 combine element. In the pictured gas pressure 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. Single Stage Regulator When the spindle of the cylinder is opened slowly, the high pressure gas from the cylinder enters into the regulator through the inlet valve. The gas then enters the body of regulator which is controlled by the needle valve. The pressure inside the regulator rises which pushes the diaphragm and the valve to which it is attached, closes the valve and prevents any more gas from entering the regulator. The outlet side is fitted with a pressure gauge which indicates the working pressure on the blowpipe. Upon the gas being drawn ‘’off’’ from outlet side the pressure inside the regulator body falls. The diaphragm is pushed back by the spring and the valve opens, letting more gas in from the cylinder. The pressure in the body therefore depends on the pressure of springs and this can be adjusted by means of a regulator knob. Double Stage Regulator Two gas cutting torch are nothing but two regulators in one which operates to reduce the pressure progressively in two stages instead of one. The first stage which is preset, reduces the pressure of the cylinder to an intermediate stage i.e. 5kgf/mm2 and gas at that pressure passes into the second stage. The gas now emerges at a pressure (working pressure) set by the pressure adjusting control knob attached to the diaphragm. Two stage regulators have two safety valves, so that if there is any excess pressure there will be no explosion. A major objection to the single stage regulator is the need for frequent torch adjustment. If the cylinder pressure falls the regulator pressure likewise falls necessitating torch adjustment. In the two stage regulator, there is automatic compensation for any drop in the cylinder pressure. Single stage regulator may be used with pipe lines and cylinders. Two stage regulators are used with cylinder and manifolds.