Expansion Tanks

Expansion Tanks

Expansion Tanks

Expansion Tanks are plumbing equipment that provides pressure control and water support in plumbing systems. The average water temperature is 80°C in systems that prepare domestic hot water in residences and workplaces. The feed water temperature is accepted as 10°C. In this case, the value of the water passing through the system constantly changes between 10°C and 80°C. The specific volume of water also changes depending on this temperature. The system is protected by using expansion tanks to correct the volume of this water, which expands as it heats up.

We can express what the expansion tank means as follows. When water is heated, it expands. The expanding water affects the pressure in the closed heating systems it is in and causes the pressure in these systems to increase. Over time, this pressure increases further and various fluctuations occur. These fluctuations begin to damage the system. If the water that expands with the increase in temperature is not taken under control, it will cause leaks in the pipes, boiler and heating system. These leaks, which break out at the weakest point, cause you to not get efficiency from the heating system and cause the system to malfunction. The device designed to prevent this pressure and possible dangers is called an expansion tank.

In fact, the expansion tank acts as a “mediator” between the increased heat pressure and the heating system. It allows the increased temperature to be controlled. It reduces the pressure in the system, balances it and helps the system to work at the desired performance. Today, every boiler room has an expansion tank. Expansion tanks equalize the pressure in the system. It is a small tank divided into two parts by a rubber diaphragm. The system works as follows; As hot water enters the heating system, the pressure in the system increases. As this pressure increases, the diaphragm in the expansion tank is pushed down. This compresses the air in the tank and creates space for excess water to enter. The excess pressure in the system is reduced, thus preventing the pipes from being damaged.

The expansion tank or the balance tank prevents the booster from being activated too often in low water consumption demands (on/off operation of the system), ensuring that the system pressure remains stable within certain limits. With the use of the expansion tank, the number of engine starts (how many times the engine starts and goes into operation per hour) is reduced, thus extending the service life of the system.

Expansion tanks can be air cushioned or membrane type. In air cushion types, there is no clear separation between water and air. Since some of the compressed air mixes with the water, air supply is required by a compressor or an air charging unit. On the other hand, there is no need for an air charging unit or compressor for membrane types. Because there is a flexible diaphragm (membrane) on the contact surfaces of air and water. Therefore, the use of membrane tanks is preferred.

There are two types of expansion tanks as open and closed;

Open Expansion Tanks

Open expansion tanks operate open to the atmosphere. It protects the system by preventing the installation from going above this pressure according to the pressure ratio in the atmosphere.

Closed Expansion Tanks

In systems where an open expansion tank cannot be placed and operating at larger capacities, closed expansion tanks working with a monometer and safety valve are preferred.

Considerations in Selection of Expansion Tank

While choosing the expansion tank, the following features should be considered.

Capacity (in liters)

Height of the place to be used

compressive strength

Auxiliary equipment to work with the expansion tank

Where is the Expansion Tank Used?

Expansion tanks are used in a wide range. It is used in various fields in industry and private sector. In general, it is possible to list the usage areas as follows;

  • Water systems
  • Washing systems
  • Pressure systems
  • Irrigation pumps
  • Solar and pressure retention systems
  • Cooling systems (shrinkage tank)
  • We come across the use of expansion tanks in heating systems such as hot water systems.


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