Tianjin U-ideal Combination Air valve;large orifice air valves,Quick Exhaust (Suction) Valve,Fire protection Combination Air valveis
Principle
When water enters into the pipe, the plug will stop at the lower part of Locating bracket to discharge the air by a large quantity. When the air has been discharged completely, water will enter into the valve to make the ball floated, driving the plug closed and exhaust stopped. Under normal operation, there can be little gas gathered onto the upper part in pipe. When it arrives to a certain extent, the water level in valve will lower,and the float ball will lower as well, the air will be discharged out from the small hole. In case of power cut and pump stop, and when the water in pipe is emptied, there can easily cause negative pressure in pipe, and the float ball will lower along with the water. Here, the small hole will be opened, and large quantity of air will come in from the large hole, thus to ensure the safety of pipeline.
Note: it cannot be used in sewage pipeline.
The Fire protection  Combination Air valveis adopted to expel 2VOL% deliquescent air in water supply system, and is suitable to be installed at high building, pipeline in plant, small scale pump station and fire-fighting system to protect or improve efficiency of water transportation and save energy. 

Air vent valves are used to allow the pressure in the tank to balance while preventing the spillage of the fluid through the vent lines. These valves allow the free flow of fluid or air in or out of a chamber or tank until they close, usually activated by a float.
During refueling, incoming fuel dis-places the air in the tank. The vent valve allows this air to escape through a designated vent path
When the tank is full, the float valve closes preventing the fuel from escaping. These valves also allow air to re-enter the tank as fuel is consumed, preventing dangerous negative pressure and potential fuel starvation. Vent valves protect the fuel tank from pressure damage resulting from expansion and contraction of the fuel due to changes in temperature. In some applications they incorporate measures to prevent the fuel from exiting the tank when the aircraft is inverted either during flight or in an emergency.

Applications for Tianjin U-ideal float-type air vents include hydronic heating systems, water service lines, water storage tanks, centrifugal pumps, gas lines, solvent filters and similar equipment. Operation is completely automatic, and the simple design and quality mechanism make operation trouble-free and maintenance infrequent.
Why remove air from a water system?
Every building services engineer knows that air trapped in either a hot or chilled water system can cause trouble, such as excessive noise, corrosion and increased maintenance costs. Air can cause air locks which inhibit the filling of the system or the priming of pumps. It can seriously affect the accuracy of flow measurement meters and regulating valves. Under extreme conditions it may even temporarily decommission plant.
Air and other incondensable gases considerably reduce heat transfer efficiency. A film of air 1 mm thick presents the same barrier to heat transfer as a wall of copper 13 m thick!
Entrapped air in any water system is a threat to thermal efficiency. It is particularly damaging in a chilled water system which does not have the natural deaerating ability of hot water.