What are expansion vessels?
The function of pressure expansion vessels is to compensate for fluid volume changes caused by temperature changes, and to keep the system pressure within the necessary limits. They are used in heating and solar systems, in drinking water circuits with storage water heaters.
The vessels are made of deep drawn welded steel sheet with anti-corrosion surface treatment in colors corresponding to the vessel type. The steel vessel is fitted with a membrane inside. One section of the vessel is filled with gas, the other one with liquid.
When cold, the expansion vessel is almost completely filled with gas. As the system temperature rises, the fluid volume and pressure increases, the fluid enters the expansion vessel and compresses gas at the other side. When the temperature drops, the fluid is pushed by gas out from the expansion vessel again.