AB Valves - Spring Loaded Air Valve

Large orifice air valves are recommended as part of safety system for large diameter and long pipe lines. Under normal condition (positive pipeline pressure) this air valve is fully closed, it serves as vacuum breaker when the internal pressure in the pipe drops to negative value. For example in case of a pipe burst situation with very rapid medium drainage, a huge volume of air is insert to the pipe through the large orifice of the air valve to prevent damages, caving in, or collapse  of the pipes. Once the pressure increases in the pipe line again, the air valve will be closed. A pneumatic damper is located in the valve to adjust the valve’s closing speed in order to avoid damages in the pipe or the valve caused by rapid closing.