For any closed heating system, a device must be provided to compensate for the expansion of the coolant. This is necessary to maintain the integrity of the pipes, radiators and the boiler heat exchanger. In addition to the standard air vent, membrane tanks for heating systems must be installed: installation, calculation, the principle of operation of which directly affects the heating efficiency of a residential building.
Purpose and features of membrane tanks for heating
First you need to know the functional qualities of this device. When water is heated in pipes, natural expansion and pressure increase occurs. If the value exceeds the standardized value, a stabilization mechanism is required. It is for this purpose that membrane tanks for heating systems are intended, which may differ in technical and design characteristics.
They represent a sealed container, divided into 2 areas - water and air chambers. An elastic membrane is located between them. To connect the water, a corresponding branch pipe is provided, and a pressure build-up system is located in the air chamber. The principle of operation of an expansion membrane tank for a heating system is to increase the usable volume as a result of the displacement of the elastic membrane towards the air chamber. To do this, it is necessary to connect a water pipe to the heating pipe, and create a pressure in the air chamber, the value of which should not exceed the nominal value for the heating system.
Installing a membrane tank in a heating system has the following advantages:
- Automatic stabilization of the critical expansion of the coolant;
- No water loss due to evaporation;
- Can be installed for both distilled water and antifreeze systems;
- Simple installation and replacement of the membrane when its service life is exceeded.
But how to choose the right membrane tank for heating, the principle of operation of which is so simple? To do this, you first need to familiarize yourself with its varieties.
A membrane tank for heating is similar in principle to that for a water supply system. But the design of the latter is not designed for high temperatures. Manufacturers mark them in blue, and heating ones in red.
Types of membrane tanks
At first glance, the design of the device is quite simple. However, for different heating systems with specific technical characteristics, the correct model of membrane expansion tank for heating must be selected. Consider the most popular models that can be installed in both household and industrial systems.
Fixed tank
Their feature is that the membrane tank for heating according to the instructions is not collapsible. those. the elastic membrane cannot be dismantled and replaced with a new one. Despite this seemingly disadvantage, these models have one significant advantage - affordable cost. That is why they are installed for small heating systems with relatively stable pipe pressure. Often, the calculation of a membrane tank for heating implies a constant pressure in the air chamber, which the manufacturer specifies additionally.But if there is a likelihood of exceeding the critical expansion rate of the coolant, it is necessary to install a different type of structure.
Flanged with replaceable diaphragm
To install a new membrane, a flange is provided in the structure on which it is mounted. Thus, you can adjust the volume of the membrane tank for heating, install elastic lotions with different elasticity indicators. Such models are mounted for heating systems with a high probability of excess pressure in the pipes. First of all, this applies to solid fuel boilers, where it is impossible to quickly adjust the water heating level. Tanks can be made of horizontal and vertical type. To replace the diaphragm, it is necessary to remove the flange, dismantle the old one and install a new one in its place. The most popular manufacturer of such models is the Wester company, a membrane heating tank, which can be found both in a small private house and in the heating system of a production workshop.
The usable volume of a membrane heating tank depends on its shape. For large systems, it is best to choose cylindrical structures, and flat models will be optimal for heating with a short pipe length.
Calculation of the diaphragm tank
However, the choice of design is not the only parameter of membrane tanks for the heating system. An important quantity is the volume in one chamber, namely, its filling factor. The correct calculation of a membrane tank for heating is impossible without the following parameters:
- The total volume of the coolant in the system is C. As is known from the school physics course, when the temperature rises for every 10 degrees, the liquid increases by 0.3%. This is what will primarily affect the volume of filling the tank;
- The maximum and minimum pressure in the system. Often, the critical value does not exceed 5 atm;
- Fill factor (Kzap). It directly depends on the pressure indicators in the pipes. In the table you can find the required value for a specific diaphragm tank. In the instructions, the manufacturer indicates the nominal value of the fill factor.
You should also take into account the coefficient of expansion for water E, which is 0.034 at 85 ° C. Further, the calculation is performed according to the formula. Suppose that the total volume of the heating system is 410 liters, the minimum pressure is 1 atm, and the maximum pressure is 3.5 atm. The filling factor will then be equal to 0.55, and the useful volume of the tank is equal.
This is the optimal calculated volume of the membrane tank for heating. If necessary, it can be changed upwards, but not more than by 15%.
An accurate calculation of the volume of a membrane tank for heating is recommended only after reading the instructions from the manufacturer. It contains all the necessary data for the calculations, as well as possible errors and deviations.
Tank installation steps
For a qualified installation of a membrane tank in a heating system, it is necessary that the room meets the operating conditions. The temperature in it should not drop below 0 degrees with a stable humidity indicator. It is necessary to determine the place of installation, since the system is characterized by pressure drops during its start-up. Therefore, it is not recommended to install expansion membrane tanks for heating immediately after the boiler on the outlet pipe.
The next criterion is the absence of turbulence in water flows that can simulate overpressure. It is best to mount membrane tanks for heating systems on the return pipe in front of the circulation pump. Installation technology consists in performing the following steps:
- Pipeline tie-in. Typically, the expansion vessel nozzle diameter is 3/4. Therefore, a suitable threaded channel must be installed in the return pipe;
- Installation should not be impeded by objects or system elements. External mechanical stress on the tank is excluded;
- It is best to use paronite models as gaskets, as they withstand pressure and high temperatures well;
- The diaphragm expansion tank for heating is necessarily equipped with an air valve. It is necessary to stabilize and regulate the pressure in the air chamber.
Each time a closed heating system is started, an increased pressure will act on the membrane. Therefore, it is recommended to check the condition at least once every 2 years and, if necessary, replace it.
This is a typical installation scheme that does not take into account the characteristics of a particular heating system and its constituent elements. During installation, frequent mistakes should be avoided, which can lead to incorrect functioning of membrane tanks for heating systems. First of all, setting the maximum pressure in the air chamber. It should be 10-15% less than the calculated critical value. Otherwise, the membrane will not expand towards the chamber, which will lead to a burst of pipes and failure of heating radiators. To avoid this, it is necessary to install a pressure gauge, which is recommended by Wester, whose membrane heating tanks are characterized by high reliability.
To install a membrane tank in the heating system, make sure that there is no such tank in the heating boiler. If its volume is not enough according to calculations, you can mount an additional tank.
Tips for choosing a diaphragm tank
First of all, it is necessary to determine the design of the membrane expansion tank intended for heating. If critical pressure surges are not expected, the total volume of the coolant is small - an inexpensive fixed type model can be selected. In all other cases, membrane tanks are required for collapsible heating systems, since it is much cheaper to change the elastic membrane than the entire structure. In addition, when choosing, you should consider the following factors:
- The thickness of the metal of the case. It must be at least 1 mm;
- Protective inner and outer coating. Since all membrane tanks designed for heating systems are made of metal, corrosion processes should not affect their integrity;
- Reduction of heat losses due to an additional insulating layer. The relatively large volume of the water chamber can negatively affect the decrease in the temperature of the water in the pipes. If the design does not provide for a heat-insulating layer, you can make it yourself using polyethylene foam or a similar material;
- Pay attention to the design. According to the instructions, the membrane tank for heating can be horizontal or vertical type. Installation in any other position is prohibited.
And most importantly, you should only purchase models from trusted manufacturers. These include expansion tanks for heating from Wester. Along with it, the products of the companies Zilmet (Italy), Aquasystem (Italy) and Sprut (China) are characterized by good quality indicators. Their average cost ranges from 2 to 5 thousand rubles, depending on the volume.
Despite the good operating characteristics, a drain safety valve is installed in addition to the expansion membrane tanks of the heating system. If the pressure in the pipes exceeds the critical value even for the expansion tank, the valve will remove excess water.
The video material presents another method for calculating the volume of the expansion tank:
