What are the differences between diaphragm expansion tanks and bladder expansion tanks?

Diaphragm expansion tanks and bladder expansion tanks are the two main categories of expansion tanks currently. So what is the difference between the two?

The working principle of the expansion tank: When water under pressure from the outside enters the diaphragm or bladder of the expansion tank, the nitrogen sealed in the tank is compressed. According to Boyle's gas law, the volume of the gas becomes smaller after being compressed and the pressure increases until the pressure inside the expansion tank increases. Stop water inflow when the gas pressure reaches the same pressure as the water. When the water is lost and the pressure decreases, the gas pressure in the expansion tank is greater than the water pressure. At this time, the gas expansion will squeeze out the water in the bladder and replenish it to the system.

Comparison between diaphragm expansion tank and bladder expansion tank:

1. The shell of the diaphragm expansion tank is in direct contact with water, and the inside of the shell is sprayed with an anti-rust layer. The interface of the tank is welded to the shell. During the welding process, high temperatures will oxidize the anti-rust coating. The originally silver-white coating turns black after welding. You can feel small black particles when you touch it with your hands. When these seemingly insignificant oxidation points are in contact with water for a long time, they will slowly rust and gradually expand until they corrode the entire tank. It is not surprising why the water poured out of this expansion tank turns yellow after being used for a period of time.

2. The inner membrane of the diaphragm expansion tank is fixed between the two carbon steel half shells of the expansion tank through hot rolling. If this process is not handled well, tiny pores will be left in the inner membrane and These tiny pores between the carbon steel will leak the precharged gas. If the expansion tank leaks gas, 90% of it will leak from here. This kind of leaking expansion tank will not be able to function as a constant pressure unloader if the gas is not replenished in time after being used for a period of time. In addition, since the wall thickness of the expansion tank is generally about 1mm, the interface is directly welded to the tank, and the torque that this connection method can withstand is quite small. When installing the tank, you can only hold the shell and rotate it. If you use too much force or too much force, the interface will be broken. This situation is most common in the air conditioning production process.

The bladder expansion tank overcomes these shortcomings very well. There is an integral bladder inside the bladder expansion tank. When working, water only enters the bladder and does not come into contact with the shell. The interface is connected with a flange. This structure avoids rust problems caused by the welding process. In addition, the bladder of the expansion tank of this structure is replaceable. Similarly, because it is a flange connection, its interface can withstand a large torque, and there is no fear of breaking the interface during installation.

The above is an introduction to the differences between diaphragm expansion tanks and bladder expansion tanks. If you have relevant needs, you can consult the customers of Nanjing Beite AC Equipment Co., Ltd. online, and we will reply to you as soon as possible. Nanjing Beite AC Equipment Co., Ltd. has focused on pressure tanks and expansion tanks for many years. The product quality is reliable and worthy of customers' choice.