A Single Orifice Air Valve sometimes referred to as a "small orifice" valve, will continuously release accumulated air during system operation. As air from the pipeline enters the valve, it displaces the water, allowing the float to drop. The air is then released into the atmosphere through a small orifice. As the air is vented it is replaced. An added benefit of an Air/Vacuum Valve is its ability to provide pipeline vacuum protection. If a negative pressure develops, the air release valve will open, admitting air into the line, reducing the potential for surges related to column separation and possible pipeline collapse.
Benefits of Single Orifice Air Valve:
While Air/Vacuum Valves will exhaust large quantities of air upon start-up, it should be remembered that they will not continuously release air during system operation. For this function, a single orifice air valve is also required.
The function of a Single orifice air valve is to allow air to be expelled from the system during filling and to admit air into the system whenever sub-atmospheric pressure occurs. When water enters the valve body the float buoyancy lifts it on to the seat and the resultant rise in system pressure ensures a tight seal, with line pressure holding the float on the seat. In the event of air entering the valve while the line is still positively charged, the valve remains shut. In the event of sub-atmospheric pressure in the system, water is drawn from the body and the float drops from the seat to admit air into the system.