Types of Pressure Relief Valves

Pressure relief valves are safety devices that eliminate excess pressure from a tank or system of tanks. The pressure relief valve activates when pressure in a tank reaches a predetermined level. Most pressure relief valves are vented through pipes to dispose of excess liquid or vapor without harming the tanks or other items in the area. Situations causing high pressure that can trigger the relief valve include mechanical equipment failures, fires in the tank area or clogged outlet pipes.

Spring-Loaded Pressure Relief Valves

• A spring-loaded valve is held closed by the tension of the spring against the pressure of the contents of the tank. When pressure within the tank exceeds the tension of the spring, the valve is forced open and the contents are vented. When the pressure drops below the tension of the spring, the valve closes to contain any remaining liquid. The system then can continue operations. This is an advantage of a spring-loaded pressure relief valve.

Rupture Disc and Pin

• A rupture disc and pin is made up of a rubber disc that expands when pressure builds inside a tank. When pressure enlarges the disc to the point it reaches the pin, it ruptures and creates an opening allowing the tank's contents to ventilate. A rupture disc and pin pressure relief valve stays open after the excess content of the tank is ventilated. The system usually becomes inoperable until the valve is replaced.

Balanced Bellows Valve

• A balanced bellows valve includes an interior tube of a material folded into an accordion or bellows-like configuration. High pressure compresses the bellows to the point that a relief opening is created. The bellows serves the same principle as the spring in the spring-loaded valve but is less susceptible to corrosion of back pressure. The valve will close when excess pressure is ventilated.