Expansion tank

Expansion tank - is designed to compensate for changes in the volume of water that occur when its temperature changes in a closed circuit heating system.

Water is an incompressible liquid that increases its volume when heated. In a closed circuit heating system, the heating of water and the increase in volume can lead to a significant increase in pressure, which can damage the heating system elements.

During the heating of the heating system, the excess water volume enters the expansion tank, stretching the membrane and compressing the air, and in the moment of cooling, the deficient volume is displaced from the tank by compressed air. Minor leaks of the heat transfer fluid in the heating system are also compensated for by water displaced from the expansion tank, if the reserve volume is provided for in its calculation.

Scope of application

Expansion tanks are installed in heating and water supply systems, boiler rooms and simply in closed circuits with heat supply to water.

In heating systems, membrane expansion tanks are installed at a thermal capacity of less than 6 MW, since in systems with greater capacity, constant water leaks usually require round-the-clock operation of the feed pumps.

Advantages

• Possibility of installation in any point of the heating system.
• Water does not come into contact with air and does not become saturated with oxygen, which promotes corrosion of heating system elements.

Equivalent names

• Membrane tank
• Closed expansion tank
• Hydroaccumulator
• Pneumatic tank

What can replace it

• An open expansion tank installed at the top of the heating system.
• A complex automated system for feeding and maintaining pressure.
• Hydroaccumulator intended for water supply systems, but attention should be paid to the permissibility of using a membrane with a hot heat carrier.