Expansion Tanks

The correct pressure is a fundamental requirement for the proper operation of water based heating, solar, cooling water systems and pressure booster systems.  Like all other substances, the volume of water changes with its temperature.  Unlike other liquids, water does not expand proportionately to the temperature.  As water cannot be compressed, this means the pressure increases significantly in closed systems as the temperature changes.

Pressure maintenance systems have to fulfil three fundamental tasks:

  • Compensate for fluctuations in the system volume due to temperature changes as the system cycles.

  • Maintain the pressure within permissible limits.  This means not only ensuring the permissible operating pressure is not exceeded but also maintaining a minimum pressure to avoid vacuum formation at system high points, cavitation, and evaporation.

  • Balance systemic water losses using a water reservoir.

In these situations, static pressure maintenance systems such as diaphragm expansion vessels can offer a simple and smart solution.  They are independent of electrical power and easy to operate.  Inside the vessel, a diaphragm or bladder seals the system water from the gas compartment, so diffusion of pressured gas into the water is prevented.  The result is a fully closed system that does not suffer from corrosion or other gas-related problems.

Cooke Industries offer expansion tanks from two of the world’s leading suppliers; Reflex Winkelmann from Germany and Varem from Italy.


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