What is a Breather Valve?
Breather Valves, also known as direct acting Pressure/Vacuum Relief Valves, are special types of Relief Valves which are specifically designed for tank protection. The range includes pressure only, vacuum only, combined Pressure/Vacuum Valves and combined Pressure/vacuum valves with pipe-away, all available with flanged outlets or vented to atmosphere. Pressure/Vacuum Relief Valves are used extensively on bulk storage tanks to minimize evaporation loss. The Valves prevent the build-up of excessive pressure or vacuum which can unbalance the system or damage the storage vessel. Pressure and vacuum protection levels are controlled with weighted pallets or springs and can be combined to provide the required Pressure/Vacuum settings. It is common to combine pallet and spring systems in one unit i.e. pressure settings require a spring section, whilst the vacuum settings use the pallet method.
Why use Breather Valve?
The Breather Valve is a protection device mounted on a nozzle opening on the top of a fixed roof atmospheric storage tank. Its primary purpose is to protect the tank against rupturing or imploding. Without an opening or a controlled opening, a fixed roof atmospheric tank would rupture under increasing pressure caused by pumping liquid into the tank or as a result of vapor pressure changes caused by severe thermal changes. Imploding, or the collapsing of a tank, occurs during the pumping out procedure or thermal changes. As the liquid level lowers, the vapor space pressure is reduced to below atmospheric pressure. This vacuum condition must be alleviated through a controlled opening on the tank. In short, the tank needs to breathe in order to eliminate the possibility of rupturing or imploding. Because of its primary function, this Valve is called Breather Valve. Valve selection should be in accordance with American Petroleum Institute Standard API 2000 or other applicable standard.
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