Performance Characteristics of Large Tank Breathing Valve
The function of the breathing valve
Under normal conditions, the breathing valve ensures the safety and sealing of the storage tank; and also minimizes the evaporation loss of the medium in the storage tank. The breathing valve starts working under the following abnormal conditions:
- When the tank carries out the media receiving operation, the gas pressure to change, and the breathing valve starts to breathe with large flow rate;
- When the gas temperature in the tank changes, as the medium steam pressure in the tank to increase or decrease, and the breathing valve begins to breathe with small flow;
- When the weather changes suddenly or a fire occurs, the temperature in the tank changes rapidly , causing the gas pressure in the tank to rise or fall sharply, the breathing valve should meet the ventilation required by the storage tank to ensure the safety of the storage tank.
Working principle
The breathing valve is a ventilation device ,widely used in the top of the tank, which is used to maintain the air pressure balance inside and outside the tank, and prevent the tank from sinking and warping. By controlling the exhalation pressure and vacuum degree of the tank, also reduce the evaporation loss of the medium in the tank . Therefore, the breathing valve should have two functions: releasing positive pressure and negative pressure.
According to the working principle, there are three kinds:
- Gravity breathing valve
- Spring type breathing valve
- Pilot operated breathing valve
The performance comparison
- Gravity breathing valve has simple structure, low price.
- Spring type breathing valve has compact structure, small size, light weight, relatively low price, and can adjust its setting pressure.
- Pilot type breathing valve is small in size, light in weight (high pressure, large caliber), It can also adjust its set pressure.However, the pilot type breathing valve mechanism is complex, the single valve is expensive, and it is only suitable for storage tanks with high technical requirements.
At present, in the domestic large storage tank, the traditional gravity type and spring type breathing valve are more used. The diaphragm structure of the pilot breathing valve ensures that the action of the main valve can be accurately controlled under very low working pressure. When gravity type and spring type breathing valve work under constant pressure, the valve is easy to leak because the working pressure is very close to the constant pressure. Before the pressure in front of the valve reaches a constant pressure, the pilot type breathing valve starts to leak late and the leakage amount is small. This not only reduces the loss of materials in the tank, but also is conducive to environmental protection.
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