Wall-hung boiler expansion tanks are widely used in central air conditioners, boilers, water heaters, frequency conversion and constant pressure water supply equipment. Buffered the pressure fluctuation of the system, eliminated the water hammer, and played the role of stabilizing pressure and unloading. When the water pressure in the system changes slightly, the air bag of the expansion tank of the wall-hung boiler will automatically expand and contract, which has a certain buffering effect on the change of water pressure, and can ensure the stability of the water pressure in the system, and the water pump will not be turned on frequently because of the pressure change. When the system uses a wall-hung boiler expansion tank, because the system pressure is higher than the pressure of the pre-filled gas, a part of the working fluid will enter the airbag (in the case of diaphragm type, it will enter the tank) until a new balance is reached. When the system pressure rises again, the system pressure will be greater than the pressure of the pre-filled gas again, and part of the medium will enter the bag, compressing the gas between the bag and the tank, and the compressed pressure will increase. When it reaches the same level as the system pressure, the medium will stop entering. On the contrary, when the system pressure drops, the medium pressure in the system is lower than the gas pressure between the bladder and the tank, and the water in the bladder will be squeezed out by the gas to replenish the system, so that the system pressure will increase until the working medium pressure of the system is equal to the gas pressure between the bladder and the tank, and the water in the bladder will not be replenished outside the system, thus maintaining a dynamic balance.
If there is no gas in the expansion tank, the expansion tank will not play the role of buffering pressure, and it is prone to failure.