The breathing valve is a ventilation device fixed on the top of the storage tank to ensure the normal state of the pressure in the tank and prevent the tank from being damaged due to the overpressure or the vacuum caused by the overpressure or the vacuum, and also to reduce the liquid volatilization loss in the tank. For the calculation and selection of breathing valve comparison, the selection is much more important, much more complex. Because the calculation is just a simple formula calculation, the breathing valve itself is not based on the accuracy of the formula, but rather on the accuracy of the given process parameters. Breathing valve selection involves more content, a little careless, it will lead to improper selection, not only resulting in human, material and financial resources, and the use of results is not satisfactory, bringing a number of problems, such as reliability, life expectancy , Running quality and so on. Respiratory valve is the use of spring limit valve plate, determined by the positive and negative pressure or call or suction. There are gravity-type breathing valve, is adjusted by gravity, when the pressure inside the container reaches over pressure when the valve opens to release pressure. Specific Description: When the pressure in the tank is balanced with the atmospheric pressure, the exhalation valve of the breathing valve closely matches the seat of the exhalation valve, and the inhalation valve and the inhalation valve seat cooperate closely. When the tank pressure exceeds the atmospheric pressure value (that is, too much pressure), the tank pressure directly under the valve flap and overcome the valve gravity and acting on the flap on the external pressure to open Exiting the valve by the A channel discharge tank is too high pressure, so that the tank pressure and atmospheric pressure balance. When the pressure in the tank is lower than the atmospheric pressure (ie too low negative pressure is generated), atmospheric pressure enters the suction channel B and acts directly below the suction port flap, overcoming the flap's gravity and acting on the tank above the flap Pressure, thus opening the suction port flap to replenish the pressure in the tank, the tank pressure and atmospheric pressure to maintain balance. When a fire occurs, the fire source may spread to the storage tank through the inlet port. When the flame passes through the narrow pores of the fire-resistant core layer in the breathing valve, the corrugated board absorbs a large amount of heat due to the wall effect so that the heat loss suddenly increases , So that the flame extinguished. 1) Breathing valves should be installed at the highest point of the accumulator gas source to reduce material evaporation losses and to provide the most direct and maximum access to the respiration valve smoothly. Usually for vertical tank, the valve should be installed in the roof of the central roof as far as possible, for the roof to be insulated tank, can be installed in the vicinity of the ladder platform; 2) When the need to install two breathing valves, they 3) If the breathing valve is used on a nitrogen sealed tank, the nitrogen gas supply pipe should be taken away from the valve port and inserted into the tank by the top of the tank for about 200mm, so that after the nitrogen gas is injected into the tank, Direct discharge, to achieve the purpose of nitrogen seal. This article Keywords: valve