How a Pressure Relief Valve Operates
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In systems where there is the possibility of gas buildup, there is normally a pressure relief valve. This is because gas pressure that accumulates in any system can damage piping if there is no way to release it. Steam is included in this category. Pressure relief valves built in at certain points along the way allow the gas pressure to return to normal and save the system. The valves can also be used for fluids as well if there is a possibility of pressure building up in a fluid process. When used for fluids, an alternate pipe is set up with the relief valve to divert the pressurized fluid until levels return to normal.
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The makings of a pressure relief valve consist of a handle or some other means of opening and closing, a shell and a plug. The plug is located in the shell of the valve and attached to the handle. If the handle is turned to the closed setting, the valve seat is next to the plug. This is because the plug is pushed against it when the handle is screwed down. This seals the valve, and gas is not allowed past the valve. Metal and rubber are two types of material that the plug can be made of. The type of material depends on the gas or fluid in the pipe.
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A pressure relief valve operates like a screw. The handle, when in the closed position, is turned as far as it can go to the right. This pushes the stem of the handle down into the valve. When rotated to the left, the screw is loosened and the handle raises. The plug, which is attached to the handle, goes down when the handle is tightened and ends up pressed tight to close the valve. The seal keeps gas from leaking. Opening the valve releases the gas from the pipe. When controlled by hand, safety precautions such as gloves are normally used to keep people from burning their hands. Some gases are extremely hot when released. Computer-operated systems are often attached to sensors that can recognize when a relief valve needs to be opened, and the system open the valve automatically by mechanical means. This takes away some of the injury risks associated with operating the valves.
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One of the most common places that a pressure relief valve can be found in the home is the hot water heater. In industry, they can be found in systems that use steam, are powered by hydraulics or are piping forms of gas for manufacturing purposes.
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