Diaphragm tanks are membrane expansion vessels that protect water supply systems against sudden increases in pressure. They are used in closed heating, solar and cooling installations and ensure their proper functioning. Expansion pressure vessels are also used in installations for increasing the pressure of the medium and supplying utility water. The vessel accepts excess water pressure when necessary.
Diaphragm tanks. Characteristics and structure
Diaphragm tanks are metal cylindrical vessels made of standard steel or stainless steel with increased corrosion resistance. Inside there is a diaphragm made of heat-resistant EPDM rubber (ethylene-propylene rubber), which can be used in a wide temperature range, from -40°C to even +120°C. The EPDM rubber diaphragm is not only resistant to high temperatures, but also to water vapor, ozone and weather conditions. An alternative is SBR rubber. The diaphragm has a bag-like membrane structure and separates the liquid medium from the gas filling the tank. The water space is connected to the installation via a connection. There is a valve outside the expansion tank which can be used to fill or release gas and thus equalize the pressure. Diaphragm tanks are available on the market in various volume variants, from 24 liters to even 300 liters.
Diaphragm tanks. Application and principle of operation
Diaphragm tanks stabilize the pressure in water supply systems and compensate for the thermal expansion of water. As the temperature changes, the pressure of the liquid changes and thus its volume changes. Diaphragm tanks protect the liquid against uncontrolled pressure increases and thus compensate for differences in liquid volume. If the volume of the liquid increases, the condensed gas is pushed upwards through the deformed membrane and the liquid takes its place. In this way, the expansion tank takes over excess liquid and equalizes the pressure. After the temperature drops, the held liquid is pushed back into the installation and the gas expands. Excess water from the installation is collected by automatic mechanisms. The purpose of expansion tanks is to protect the installation against failures and damage as a result of uncontrolled temperature increases. They maintain the installation parameters within specified limits, especially the pressure at an acceptable level. They also increase the active volume of the water supply system and suppress hydrodynamic shocks. The use of expansion tanks significantly increases the service life of pumps.
Expansion tanks most often cooperate with central heating installations and heat pumps in the heating systems of residential buildings. The expansion tank is also an integral element of hydrophore sets, whose task is to maintain constant water pressure. However, in solar installations, the expansion tank can be additionally used to store the working liquid. Diaphragm tanks can be used not only to stabilize the pressure, but also to degas the installation or replenish water losses.
