Expansion Tank Usage Areas
In heating and cooling systems
If the pressure drops below the atmospheric pressure, this may cause airenterance into the system. Due to this air in the system water flow may be blocked, and undesirable deposits may
occur in the installation as a result of oxygen corrosion. In addition, air can cause cavitation, especially in low height systems, at pumps and control equipments. For this reason, it is very important that the closed-loop systems are kept under a certain static pressure during operation. This may be possible by compensating for fluctuations in the amount of water between the maximum and minimum water temperatures.
In pressure booster sets, the expansion tank functions as a pressurized water storage and is used to limit the number of pump switches. The difference between the amount of water instantaneously discharged by the pump and the amount of water consumed is stored in the tank or used from the tank. The pre-charged pressure in the tank is adjusted so that it will be slightly below the cut-in pressure of the pump. When the water pressure drops to the cut-in level due to consumption, the pump starts to operate and supplies water to the system. When consumption is cut off, the pump continues to operate until the gas pressure in the tank is raised to the cut-out pressure and stores some amount of pressurized water in the tank. When the consumption starts again, the water in the tank is used until the gas pressure drops to the cut-in pressure of the booster set, then the pump starts. In this way, the number of pump switches is reduced depending on the pressurized water accumulation capacity of the tank, and becomes independent from the start/end frequency of use. In addition, the pressure fluctuations that
occur during the cut-in/cut-out of the pumps are also absorbed to provide a safe and comfortable operation.
There is no need to control the number of pump switches in frequency-controlled booster sets, which adjusts the pump speed, and thus the flow, according to the amount of consumption. Because the pump continues to run at the minimum speed for a preset period of time after the usage is interrupted, and if the usage starts again during this period, the pump increases the flow accordingly. In such systems, the expansion tank is used not to adjust the number of switches, but to increase the safety and comfort of use by absorbing the water hammers and pressure fluctuations in the system. For this reason, a tank with a much smaller volume is sufficient. Likewise, in water supply and transfer systems expansion tanks are used to prevent system equipment from being damaged by water hammers and excessive pressure fluctuations.