A relief valve relieves excess pressure in pneumatic or steam lines, preventing dangerous explosions. It is adjustable and rebuildable, and some emergency valves require manual resetting. Machines like air compressors and pneumatic presses use relief valves to operate safely. Steam engines also use relief valves to prevent overpressure.
A relief valve is a device used to relieve excess pressure in a pneumatic or steam line. Typically constructed with adjustable tension springs, the relief valve has a panel or valve that will open when the pressure reaches a predetermined point. It is often referred to as a blow-off or pop-off valve due to the sound made by escaping pressure when the blow-off valve is opened. The typical blow off valve is adjustable and rebuildable to allow the valve to perform in a variety of manufacturing operations. While the common safety valve resets automatically after releasing excess pressure, which allows the system to remain functional, some emergency valves must be manually reset after opening.
With machines such as air compressors, excessive air pressure inside the holding tank can lead to dangerous explosions and injury or death to nearby operators. While the typical air compressor is built with a pressure sensitive safety switch intended to turn the compressor on and off as the air pressure rises, it can sometimes fail. When this happens, the compressor could potentially build up enough air pressure to cause the tank to rupture. By installing a relief valve in the compressor tank, the valve can open and relieve any excess pressure before the tank fails and potentially injures people and property.
Many air presses and other types of manufacturing machinery depend on a relief valve to relieve excess pressure while the machine does its normal job. When a pneumatic press is operated, a loud swish of air can be heard escaping from the press after each pressing cycle. This is the sound of the relief valve releasing the high pressure of air needed for the press to do its job. The press regains the high pressure needed to operate as the press is loaded by the press operators. Once loaded and ready, the press performs another pressing sequence and vents the air pressure again and returns to the starting position.
With steam engines, the process is much the same. A relief valve vents accumulated steam from lines or machinery after each work cycle and prevents overpressure of components within the machine. The sound of the steam being released is often very loud and high-pitched as the valve opens and closes at high speed, allowing steam pressure to escape instantly without gradual pressure build-up. Closing the valve is just as abrupt and often makes a louder sound than an opening valve as the pressure escaping through the relief valve is reduced almost instantly.
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