These are special devices that function as an end-of-line valve to protect against pressure and vacuum. The valves may be designed as pipe away version which can be connected to a vent header to process vapors.
 
Preferred Applications
PROTEGO® pressure/vacuum relief valves are used as inbreathing and outbreathing valves, pressure relief valves, conservation valves, for simple control, and for venting tanks and equipment when an unallowable vacuum or pressure is exceeded. They are used for low pressures, i.e. in pressure ranges in which classic safety valves cannot be used due to their limited performance characteristics. PROTEGO® valves are available as pressure relief valves, vacuum relief valves, or as combined pressure/vacuum relief valves.
PROTEGO® diaphragm valves are used for problem products and low temperatures.
Pilot valves are advantageous for special control responses or when a tight seal is required up to the point at which the valve starts to open.
High-velocity-vent valves are used on tanker ships and for special land uses.