Exhaust valve is the use of liquid on the buoyancy of the float characteristic principle, when the exhaust valve level rises, in the exhaust at the same time, the float is subject to the buoyancy of the liquid, automatically floating until the sealing surface with the exhaust port, to a certain pressure when the ball will be automatically closed, when the valve level is lowered, the ball will be with the level of the liquid down, this time will be injected into the pipeline through the exhaust port to inject a large amount of air, mounted in the pipeline, the use of the liquid to the When mounted on the pipeline, the exhaust port will be opened/closed automatically by using the inertia of the liquid on the float. When the pipeline is running, the float stops at the bottom of the bowl for a large amount of exhaust, when the air in the pipe is discharged, the liquid rushes into the valve, passes through the bowl and then pushes back on the float, so that the float floats closed, the pipeline is in normal operation, such as a small amount of gas will be concentrated in the valve to a considerable extent, the valve level drops, the float falls with it and the gas is discharged from the small hole. If the pump stops, negative pressure will be generated at any time, the float will drop at any time, for a large number of suction to ensure pipeline safety. Exhaust state, the float due to gravity, the end of the lever will be pulled down, then the lever is in a tilted state, in the lever and the exhaust hole contact part of the gap, the air will be discharged through the gap by the exhaust hole, with the air discharged, the liquid level rises, the float in the liquid buoyant force upward, the sealing surface on the lever is gradually pressed on the exhaust hole, until the entire exhaust hole is completely blocked, the exhaust valve The exhaust valve is then completely in a closed state.

The importance of exhaust valves

For a long time, people do not know enough about whether urban water distribution pipelines contain gas and whether it may cause pipe bursting, so they cannot fundamentally solve the problem of water leakage from time to time in the pipeline network. Therefore, we need to reveal the normal operation of the water supply network may be stored in the gas causes and the principle of the pipeline pressure and caused by the burst, in order to improve the gas-containing type of broken water hammer awareness.

1, the normal operation of the pipe network in the source of gas: water supply network gas generation mainly the following five cases

(1) part of the region or the whole pipe network for some reason stopping water;

(2) Individual pipe sections of the accident repair venting;

(3) single or multiple large users flow regulation too fast to make the pipeline negative pressure, exhaust valve and pipeline not tight place gas injection;

(4) Not in the flow of gas release;

(5) in the pump suction pipe and impeller, due to the operation of the negative pressure generated by the release of gas.

2, water supply pipe network airbag movement characteristics and hazard analysis :

As the pipe diameter of the water supply pipe network along the main water flow direction from large to small, the main form of pipeline gas storage is the segment plug flow, that is, the gas is discontinuous with a number of independent airbags exist at the top of the pipe. The length of the airbag and accounted for over the water cross-section area depends on the gas content, pipe diameter size and longitudinal section of the pipeline conditions and so on. Theoretical research and practice shows that the airbag along the top of the pipe with the movement of water flow, easy to turn in the pipeline up, reducers, valves, etc. to produce aggregation, and produce pressure oscillation. Due to the pipe network speed and direction of water flow has a great deal of randomness, gas movement caused by the pressure rise will depend largely on the drastic degree of change in water velocity. The relevant experiments have proved that the pressure rise up to 2Mpa, enough to destroy the general water supply pipeline. In addition, it is worth noting that the long-term movement of the airbag in the pipeline network, the size of its volume with the size of the pressure changes to the place. This further exacerbates the pressure fluctuations of gas-containing water flow, resulting in an increase in pipe bursts. Pipeline gas hazard by the size of the gas content, pipeline structure and operation and other factors, the hazards can be divided into two categories of explicit and implicit, the characteristics are as follows:

Explicit hazards are mainly in the following areas

(1) poor exhaust caused by water difficulties

In the water and gas, float exhaust valve of the role of the large exhaust port is almost zero, only by micro-hole exhaust, resulting in a serious "gas plug", gas discharge, water flow is not smooth, so that the water flow channel cross-sectional area of the people become smaller or even cut off, the water flow is blocked, the system cycling ability to reduce the local flow rate increases, the increase in the loss of water head, in order to maintain the original circulation In order to maintain the original amount of circulation or head must increase the opening of the pump, increase power and the cost of the line.

(2) poor exhaust caused by the water and running during the burst pipe, the water supply system can not run normally

pipeline due to exhaust valve due to the ability to micro-exhaust caused by the phenomenon of pipe burst, according to the relevant theoretical calculations, exhaust gas caused by poor air burst pressure up to 20 ~ 40 atmospheres, the destructive force equivalent to the static pressure of 40 ~ 80 atmospheres, enough to destroy any water supply pipe, the strongest engineering ductile cast iron is not uncommon to be destroyed, all types of pipeline pipe burst instances are too many to mention, typical of a city in the Northeast, a city, the water supply system can not run normally, and the water supply system can not run normally, and the water supply system can not run normally. pipeline length of 91Km, a few years of operation burst pipe up to 108 times as much as the experts of the Shenyang Institute of Architecture and Engineering after analysis concluded that the gas explosion. A city in the South, a section of the pipeline only 860m, pipe diameter DN1200mm, running a year burst up to 6 times more. Conclusion is due to the exhaust valve can only be a micro-exhaust caused by poor exhaust pipeline caused by the destruction of the gas explosion. Finally, the exhaust to ensure that a large number of exhaust can be replaced by a power-type high-speed exhaust valve, from the fundamental solution to the problem of pipe burst.

(3) due to the continuous release of air in the water and the release of air and air sacs gradually formed and increased, the dynamic pressure of the water flow rate in the pipe constantly changing, the system parameters are unstable, and may produce greater vibration and noise.

(4) Alternate contact with air and water, metal surface corrosion increases.

(5) The pipeline produces unpleasant noise.

Hidden hazards caused by poor rolling air

1 poor exhaust gas may make the pipeline pressure instability, flow regulation is out of alignment, pipeline automatic control is out of alignment, the failure of safety measures.

2 pipeline leakage increase; 3 pipeline failure increase, long-term

3 pipeline failure to increase, long-term continuous pressure shock caused by pipe joints and pipe wall fatigue, resulting in reduced service life and other issues, increasing maintenance costs.

A large number of theoretical studies and some applications show that the pressurised water supply pipe contains more gas, it is very easy to happen to the pipeline hazard.

Maximum harm to the breakage of the bridging water hammer, long-term use will make the wall fatigue brittle, shorten the life expectancy, increase the amount of water loss, and even burst pipe. Urban water supply pipeline leakage of the biggest root cause of the problem is the pipeline exhaust, the most important way to solve the problem is the bottom of the exhaust pipeline gas storage, the choice of exhaust valve can be discharged. At present, the power type high-speed exhaust valve can meet the requirements.

Exhaust valve is an essential auxiliary component of the pipeline system, widely used in boilers, air conditioning, oil and gas, water supply and drainage pipelines, long-distance slurry transport. Often installed in the high point or elbow, etc., to exclude excess gas in the pipeline, improve the efficiency of pipeline road use and reduce energy consumption.

Classification of exhaust valves

Micro-exhaust valve in general, the water contains about 2VOL% of dissolved air, in the process of water transfer, these air from the water is constantly released, gathered in the high point of the pipeline, the formation of air pockets (AIR POCKET) to make the water transfer difficult, the system's water transfer capacity can be reduced by about 5-15%. The main function of this micro-exhaust valve is to exclude the 2VOL% of dissolved air, and is suitable for installations in high-rise buildings, plant piping, small pumping stations to protect or improve the system's water transfer efficiency and energy savings.

Single lever (SIMPLE LEVER TYPE) micro-exhaust valve, for a similar oval valve body, all internal parts, including the float, lever, lever, bar, seat, etc. are 304S.S stainless steel, the internal use of the standard exhaust orifice diameter 1/16 "for up to PN25 working pressure environment.