Double Orifice Air Release Valve

Double orifice air release valve is a dual-channel automatic air vent device widely installed on high points, long ascending sections and pipeline terminals of municipal water supply, irrigation, sewage and fire-fighting pipe networks. Equipped with two independent exhaust openings of different sizes, it combines rapid bulk air discharge, continuous micro air venting and vacuum breaking into one unit, making it an upgraded alternative to single orifice air valves and a mainstream matching fitting for medium and large-diameter water delivery pipelines.

When pipelines are first filled with water after maintenance or construction, huge volumes of trapped air need to be evacuated quickly. The large main orifice fully opens to exhaust massive air at high speed, shortening pipeline priming time significantly. As water level rises and lifts the primary float, the large opening is tightly sealed to stop liquid leakage. During normal running, dissolved air constantly precipitates from the water and gathers at the top of pipes. The small auxiliary orifice works separately to slowly release tiny air bubbles without disrupting pipeline pressure or water flow. If air pockets accumulate without timely venting, effective flow area will shrink, water transmission resistance rises sharply, pump power consumption increases, and severe vibration or water hammer may damage pipe fittings. When the pipeline drains or emergency shutdown occurs, internal negative pressure forms; the float drops to reopen the large orifice, allowing outside air to flow in and break vacuum, preventing pipeline collapse, deformation or cracking, especially for HDPE plastic pipes and thin-walled ductile iron pipelines.

The valve body is integrally cast from high-toughness ductile iron EN-GJS-500-7, with internal and external fusion bonded epoxy coating over 250 μm thickness. The anti-corrosion coating resists rust, scale and mild chemical erosion, meeting drinking water sanitary standards for urban potable water systems. Two separate floating assemblies are arranged inside the cavity: a large stainless steel float for the main exhaust port and a lightweight auxiliary float matched with the small vent hole. All sealing contact surfaces adopt high-elastic EPDM rubber gaskets, achieving bubble-tight shutoff under PN10 and PN16 rated working pressure. The split top bonnet design enables easy disassembly for sediment flushing and float replacement, without removing the entire valve from the pipeline. It operates fully automatically by buoyancy of medium, requiring no power supply or manual operation, which cuts long-term operation and maintenance costs.

Standard specifications range from DN40 to DN250 with standard flanged connections compatible with GB and DIN pipeline standards. Applicable media include tap water, fire water, raw river water, agricultural irrigation water and low-corrosion wastewater, with operating temperature from 0°C to 80°C. Every finished product undergoes a shell strength test at 1.5 times nominal pressure and air tightness inspection before delivery to guarantee stable sealing performance under full pipeline load.

Compared with single orifice air release valves, the double orifice structure separates large air discharge and micro venting functions to avoid functional interference, delivering more reliable protection for long-distance trunk pipelines. It is extensively used in municipal water main networks, reservoir water conveyance pipelines, large farm irrigation systems, sewage treatment plant piping and urban fire protection infrastructure. By stabilizing pipeline flow and pressure, eliminating air blockages and suppressing water hammer risks, this valve reduces energy waste of water pumps and extends the overall service life of the whole fluid transportation system.