Large orifice Air Valve is recommended as part of the safety system for large diameter and long-length pipes. Under normal conditions (positive pipeline pressure) this Air Valve is fully closed, it serves as a vacuum breaker when the internal pressure in the pipe drops to a negative value. For example in the case of a pipe burst situation with very rapid medium drainage, a huge volume of air is inserted into the pipe through the large orifice of the Air Valve to prevent damage or crumple of the pipes. After pressure increases in the pipeline, the air valve will be closed again. A pneumatic damper is located in the valve for adjusting valve closing speed to avoid damage to the pipe or valve due to rapid closing.