Expansion tank

Expansion tank - is designed to compensate for water volume fluctuations caused by temperature changes in a closed heating system loop.

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

When the heating system heats up, the excess water volume enters the expansion tank, stretching the membrane and compressing the air, and when the system cools down, the deficient volume is expelled from the tank by compressed air. Minor coolant leaks in the heating system are also compensated by water displaced from the expansion tank if a reserve volume is provided during its calculation.

Application

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

In heating systems, membrane expansion tanks are installed for thermal capacities of less than 6 MW, as larger systems typically require constant water replenishment, demanding continuous operation of make-up pumps.

Advantages

• Can be installed at any point in the heating system.
• Water does not come into contact with air and does not become oxygenated, which prevents corrosion of heating system elements.

Alternative Names

• Membrane tank
• Closed expansion tank
• Pressure tank
• Pneumatic tank

Substitutions

• An open expansion tank installed at the highest point of the heating system.
• A complex automated system for replenishment and pressure maintenance.
• Pressure tank designed for water supply systems, though care must be taken regarding membrane suitability for hot coolant use.