An expansion membrane tank is an element of a closed heating system designed to compensate for the thermal expansion of the coolant and maintain the required pressure.

Note! In addition to being used in heating systems, membrane tanks are also used in water supply systems. They "soften" the water hammer that occurs when the pumping stations are turned on / off, and also maintain a constant pressure in the system.

Diaphragm tank design

The expansion membrane tank for heating is a sealed cylindrical steel body covered with red epoxy lacquer (there are also blue lacquered tanks, but they are designed for cold water). There are 2 chambers in the body: gas and water, which are separated from each other by a movable gas-tight membrane (diaphragm) made of butyl rubber. Thanks to this material, the membrane is able to function stably at various temperatures (from -10 to + 100 ° C) and perform up to 100,000 cycles.

The membrane practically completely excludes the interaction of the coolant and gas. The absence of such interaction allows the pre-pressure in the gas chamber to be maintained longer, which has a positive effect on the service life of the tank.

Note! Modern high-quality membranes are not simply pulled out under the pressure of the expanding coolant, but, as it were, "stick" to the walls of the tank. This principle of operation allows to increase the service life of the membrane.

Both chambers have the same pressure, which allows maintaining the tightness of this section of the heating system. The air chamber is filled with a nitrogen-containing mixture. When the coolant expands, nitrogen is compressed, allowing the coolant to "enter" into the water chamber.

Most modern membrane heating tanks have a nipple built into the body (similar to a conventional automobile one), with which you can "pump" the air chamber by increasing the pressure in it. You can do this yourself at home using a pump or compressor. However, it should be remembered that it is recommended to inject nitrogen, and not air. The fact is that the oxygen contained in the air will cause accelerated corrosion of the walls of the tank body, which will inevitably shorten the service life of the device. Nitrogen, on the other hand, is neutral and does not corrode.

The tank body has an external threaded outlet for easy installation. Depending on the model, the thread can be:

• For low pressure tanks (from 0.5 to 1.5 bar) - 3/4 ″ or 1 ″;
• For medium pressure tanks (1.5 bar) - 1 ″;
• For high-pressure tanks (from 3 bar and above) - from 1 "to DN 100 flanged connections;

The principle of operation of the diaphragm tank

When the heating system starts up, the coolant heats up and increases in volume. This excess volume moves into the water chamber of the expansion vessel. After the coolant has cooled down, the pressure in the air chamber squeezes out the membrane, thereby displacing the coolant from the water chamber back into the heating circuit.

In addition, as noted above, the membrane tank maintains the required pressure in the entire heating system. So for example, if somewhere there was an insignificant leak of the coolant, then the pressure should drop in the entire system, but this does not happen, because the pressure in the air chamber will push the membrane and, with it, the coolant back into the system, thereby creating a limited make-up.

1. The coolant is in constant contact with air, which leads to the airing of the system and the appearance of air locks. Therefore, it is necessary to regularly remove air or is required. Otherwise, air can lead to corrosion of individual elements of the heating system, as well as to a decrease in heat transfer from heating devices;
2. Due to the constant presence of the coolant in contact with air, it evaporates. You have to regularly add coolant to the system;
3. Air microbubbles circulating through the heating system create unpleasant noises in pipes and radiators, and also lead to premature wear of parts. In addition, microbubbles "de-rate" the circulation pump;
4. Unlike the membrane tank, which can be installed at any point in the system (next to the boiler, in the basement, ...), the open-type expansion tank is installed only at the highest point. This leads to an increase in the cost of the system, because additional pipes and fittings must be used to mount the tank at the highest point.

For any closed heating system, a device must be provided to compensate for the expansion of the coolant. This is necessary to preserve 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 heating tanks

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 both for a system with distilled water and antifreeze;
• 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 a household and an industrial system.

Fixed tank

Their feature is that the membrane tank for heating according to the instructions is not collapsible. those. the elastic membrane cannot be removed 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 installed 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 that 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 you know 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 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 indicator of humidity. It is necessary to determine the place of installation, since the system is characterized by pressure drops during 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 must be 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 diagram 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.

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, one should take into account the following factors:

• Case metal thickness. 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. 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 diaphragm expansion tank is an indispensable component of the heating system, without which it is impossible to fully heat the room in the cold season. With the help of this device, critical changes in the volume of water are compensated, which are the result of its heating.

Tank device

If the heating system does not include an additional device, into which an excess volume of liquid can pass, then it may fail. The role of a spare tank is played by a membrane tank, which is necessary for smooth operation.

Membrane

The reservoir housing has an elastic membrane that divides its inner chamber into two parts. One part contains a coolant, and the other is filled with air. Nitrogen can be used instead.

Depending on the model, the device may include a replaceable or non-replaceable membrane. In the first case, the coolant is placed in an elastic cavity and does not come into contact with the metal inner surfaces.

Installation (or removal) of the membrane is carried out through the flange, for which bolts are used. Such manipulations are performed when the equipment is being repaired.

If the device has a non-replaceable membrane, then it is equipped with an internal cavity of two sections. Dismantling in this case is not provided.

To protect the system from overpressure, the diaphragm tanks are equipped with safety valves.

Operating principle

The principle of operation of the device is based on the change in the volume of liquid during heating and cooling.
In a closed loop, the water, heating up, expands, while the pressure in the entire network increases. The excess volume of liquid enters the expansion tank, where it reduces the amount of air by stretching the membrane between the chambers.

As the temperature drops, the pressure in the system drops and air displaces water from the tank. Water from the tank will continue to flow until the pressure equilibrates.

Application area

Diaphragm tanks are widely used. They are embedded in systems such as:

• heat supply from heat;
• heating system connected to the central heating line according to an independent scheme;
• heating powered by solar collectors and heating ducts;
• any systems with a closed loop and variable temperature of the working environment.

Advantages

The invention of a closed expansion tank with a membrane made it possible to increase the working life of the entire heating system. The device has the following advantages:

• allows the use of water of any composition, incl. hypercalcified;
• a membrane made of butyl and natural rubber allows the use of equipment for drinking water;
• the principle of operation and the membrane design of the device can ensure the reception of a significant amount of the displaced liquid;
• easy installation;
• minimal losses from evaporation;
• low operating costs.

Scheme of use in the heating system.

The compact dimensions of the flat membrane tank allow an economical use of room space, so it is best suited for oversized rooms.

The expansion tank does not allow the occurrence of increased loads in the heating system and is an effective means of preventing emergencies.

Equipment selection

First of all, the volume of the coolant for the heating system is taken into account. If the selection is not performed correctly and the volume is not enough, then cracks and water leaks will appear at the joints.

In addition, pressure may drop below a safe minimum. This will lead to the airing of the internal cavity of the tank, then urgent repairs will be required. Therefore, it is better to select a model based on the characteristics that the accompanying instructions contain.

The value of the initial pressure in the expansion vessel connected to the cold heating network must match the static pressure of the system. The permissible discrepancy between the indicators can be + 30-50 kPa.

This table will help you calculate the required tank volume.

The tank must have a volume of at least 10-12% of the total volume of the heat supply network in which it is used. This will exclude the possible failure of both the reservoir itself and the entire heating system as a whole during a pressure surge.

When choosing a suitable model, you should also take into account the maximum allowable pressure at which the device can function.

Diaphragm tanks protect the heating system from excessive temperature rise and regulate the pressure level in it. Therefore, such devices are equipped with independent temperature and pressure sensors.

Mounting the device

The installation is carried out in such a way that subsequent maintenance can be carried out without hindrance.
The new tank, as a rule, has an excess initial gas pressure that spreads throughout the entire volume. Before installing the expansion tank, it must be inflated to the previously calculated pressure.

The diaphragm tank must be installed before branching the water supply. It is necessary to ensure the drainage of water and make-up of the system. The room must be maintained at a positive temperature.

Additional loads on the tank are unacceptable! If the container has a volume of 8 to 30 liters, then wall mounting is allowed. For large volumes, the equipment is placed on its legs.

Grounding must be carried out to prevent electrolytic corrosion.

Setting up the device

In order not to wonder how to check the pressure, it is advisable to install a pressure gauge at the outlet. To remove excess air, it is rational to supplement the equipment with an automatic valve.

The set of the required pressure is carried out in strict sequence. First, the pressure is released through the nipple or using a compressor. Then connect the device to the heating system and fill it with water. The process does not stop until the pressure in the system and in the tank is the same.

When arranging the heating system, it is necessary to pay attention to absolutely all points, from the design of the heating unit to its complete set. Among all the variety of functional elements, a vacuum expansion tank for heating plays an important role in creating high-quality heating equipment. Thanks to this device, the volume of the coolant is regulated, which eliminates the rupture of the heating main, radiators and shut-off valves.

The principle of operation and types of compensatory devices

If you are going to equip a heating unit in a country house, then an expansion tank for heating (expansomat) must appear in it without fail.

The scheme of operation of the expansion tank for heating is simple: with an increase in the temperature regime of the coolant, its volume (we are talking about water, since it is it that is most often used for piping heating units) increases. Due to the fact that the circuit is closed, the liquid does not evaporate or burn, which, in turn, provokes an increase in pressure in the line, which must be reduced in order to avoid an emergency. This stabilization of pressure in the heating system is called compensation, and it is for these purposes that an expansion tank for heating is used.

Types of expansomats

Until recently, heating units were widely used that worked by means of gravitational circulation of the coolant, that is, without centrifugal pumps. Open-type expansion tanks were installed for them. But at the same time, such devices had a lot of shortcomings, so today they are practically not used for piping thermal blocks.

And the thing is that air entered the open expansomats, which provoked the development of corrosion on the inner surfaces of the heat exchangers. In addition, the liquid from the system was regularly evaporated, which required constant monitoring of its amount, since this could lead to a decrease in the efficiency of the entire heating unit. And besides, such tanks should be located at the highest point of the system, which is not always convenient and practical.

Modern heating blocks are characterized by the use of pumping units and closed-type expansion tanks. In this case, the advantage is that the heating circuit is completely sealed.

The scheme of operation of the membrane expansion tank of the heating system is based on the following principle: inside it there is a membrane that divides the expansomat into two parts. One half contains air or gas, which is pumped into it under pressure. Whereas at the expense of the other part, the amount of liquid is directly adjusted. The membrane for the expansion tank is made of elastic material, which causes the air chamber to contract when water enters it, the pressure in it increases, thereby compensating for the increased pressure in the heating circuit. When the coolant is cooled, the opposite process takes place.

Buried type expansomats can be flanged (with a replaceable membrane block) and one-piece (with a non-replaceable membrane). The second option is the most preferable due to its favorable cost. But at the same time, flange expansion joints are much better in terms of performance, since if the membrane ruptures, it can be replaced with a new one without any problems.

Choosing an expansion tank

The choice of a heating system compensator is quite important, so you need to take it seriously. An important aspect of choosing a compensator is:

• type - closed or open;
• standard size;
• membrane properties:
• resistance to diffusion processes;
• working temperature;
• operational period.

You can find out all these data directly in the store where you will purchase the expansomat.

How to calculate the volume of the expansion joint?

First, we will determine the dependence of the required volume and the parameters that affect it. When calculating, it is necessary to take into account the fact that the larger the volume of the thermal circuit and the higher the maximum permissible temperature regime in it, the larger the size of the compensating tank should be.

So, to determine the volume of the expansion tank, you can use the following formula:

• K ov is a coefficient that shows the size of the increase in the cubic capacity of the coolant when it is heated.

According to research data, for every 10 ° C increase in the water temperature in the main line, it becomes 0.3% more. In simplified calculations, a figure of 5% is used. In the event that a non-freeze (antifreeze) circulates along the thermal circuit, this value will be from 8 to 10%, depending on the type of anti-freeze liquid.

• V vk - the volume of water in the line.

This data is taken from the calculations of the project, which were carried out at the stage of drawing up the diagram of the heating unit. In the event that you do not possess such data, then you will have to determine the cubic capacity of the coolant yourself. This can be done by draining the fluid from the pipeline. The amount of water is measured with buckets or a flow meter, which is installed on the stream.

• R dk is the maximum allowable pressure of the boiler and the entire circuit as a whole. This value is taken from the rating data of the heating element.
• P db is the pressure indicator in the air compartment of the regulator, which is indicated by the manufacturer in the technical passport of the unit.

Based on the calculation results, you will receive an accurate value.

The installation of the expansion tank of the heating system is carried out in accordance with all the rules for the installation of such equipment, which are regulated by the project and the instructions of the manufacturer of the equipment. The installation of an open-type compensator is carried out at the highest point of the heating main. Whereas closed tanks are placed anywhere, but not immediately after the pumping unit.

When installing compensating tanks, it is necessary to pay special attention to its fasteners, since its mass together with the liquid is large enough.

As a rule, such equipment is equipped with all the necessary fasteners, however, according to user reviews, they are far from always able to ensure reliable fixation of the tank.

In addition, during the installation of this functional device, it is worth thinking about the fact that it should be convenient for you to use it.

Features of the maintenance of the compensating tank

• regular checks for corrosion, dents and smudges - at least once every 6 months;
• checking the initial pressure of the gas space for compliance with the calculated indicator - at least once every 6 months;
• checking the membrane for deformations and damage - at least once every 6 months;
• storage of an unused tank is carried out in a dry place.

That is, in fact, all the subtleties of the device of this functional equipment. We hope this publication will help you equip your home with an efficient heating system.

VIDEO: Overview of expansion tanks with a volume of 2-12500 liters with fixed and replaceable membranes and automatic expansion systems controlled by compressors

Many devices are used in heating and water supply systems. One of the main ones is the membrane tank. With its help, pressure drops are smoothed. Diaphragm tank for heating system, principle of operation which is based on improving the quality of the heating system, consists of a sealed barrel with a flange.

In this way, it connects to the pipeline system.

Diaphragm tank device

The equipment is presented in the form of a sealed vessel, divided into two sections:

• The air section includes pressurized air.
• The water section is attached to the heating. It passes water of various pressures through itself.

An elastic membrane separates the compartments, due to which it changes in shape. Therefore, the volumes of these compartments change. The air compartment contains a valve with a nipple, which changes the pressure. With its help, the functioning of the membrane tank is regulated.

Air pressure influences water flow as well as volume and pressure.

Principle of operation

As the water compartment increases, the tank expands. As a result, it fills with a lot of water. And the air department gets smaller. The air pressure then decreases, thereby balancing the water pressure. When the pressure in the system decreases, the membrane contracts, after which the lost pressure is replenished.

The water supply in the membrane tank will continue until the air and water pressure are balanced.

Diaphragm tank functions

• For the heating system. Heating water leads to an increase in its volume, which requires the use of expansion tanks. With their help, the expansion of the water is compensated. The size of the device must correspond to the heating system: the volume "dampens" the expansion of the water. If there is no membrane tank, then heating leads to defects in the heating system. As a result, the entire system may fail.
• In a water supply device, a membrane tank is used instead of a hydraulic accumulator, due to which water accumulates, after which its consumption occurs as intended. For operation, the pressure present in the accumulator is used, and a pump is not required in this case. Since the pump operates infrequently, its service life is extended. As a hydraulic accumulator, it performs the function of water compensation when hot water is connected.
• Water hammer protection function. If you suddenly turn on the pump for supplying water, then such an overlap leads to the appearance of a water hammer. It assumes a pressure drop, due to which the pipeline and the entire mechanism fail. The membrane tank will perform the function of protection: due to the high pressure, the membrane will stretch, the water section will be large, and the pressure will decrease.

The use of such equipment is useful in many areas of equipment operation. Therefore, its presence in the heating system is very important.

In the heating system, a very important element is the expansion tank for heating. Such a device serves in order to receive surplus coolant at the moment when it expands, thus preventing bursting of the pipeline and taps.

The principle of operation of the expansion tank for heating is as follows: when the temperature of the coolant rises by 10 degrees, then its volume increases by about 0.3%. Since the liquid is not burnt, excessive pressure appears, which must be compensated. It is for this that the expansion tank is installed.

Types of expansion tanks

Different types of expansion tanks are used in different heating systems. Previously, systems that did not have circulation pumps used an open expansion tank for heating. But such tanks had many drawbacks, so now they are very rarely used. Due to the fact that air enters such an expansion tank for heating, corrosion appears, and the liquid also evaporates faster and must be constantly replenished. Such a tank should be placed at the highest point of the heating system, and this is not always easy and simple to implement.

Open expansion tank for heating

In such heating systems, where the heat carrier circulates with the help of a pump, a closed expansion tank is placed for heating, the calculation here is made on the fact that it is a sealed container that has an elastic membrane inside. A membrane (balloon or diaphragm) divides the tank into two parts. Air or inert gas is pumped into one part under pressure, and the other part is intended for excess coolant. The membrane inside the tank is elastic, therefore, when the coolant enters there, the volume of the air chamber becomes smaller, the pressure in it increases, thus compensating for the high pressure in the heating system. During cooling, the opposite process takes place.

The device of closed expansion tanks

A closed expansion tank for heating a flat tank can be flanged (have a replaceable membrane) and with a non-replaceable membrane. The second type is in high demand due to its relatively low cost. But flanged expansion tanks are in many ways better - the pressure here can be higher, and if the membrane bursts, then it can be replaced.

The flanged expansion tank of the heating system can be either vertical or horizontal.

Here, the liquid, when it enters the tank, does not have contact with the metal surface, since it is inside the membrane. If the diaphragm is damaged, it can be replaced through the flange.

Vertical and horizontal flanged tanks

Tanks in which a replaceable membrane is not provided, it is fixed rigidly along the entire perimeter. The diaphragm is pressed against the inner surface from the very beginning, since the volume of the expansion tank for heating is completely filled with gas. After that, the pressure in the expansion tank of the heating increases, and the liquid goes inside. When the system starts up, the pressure can rise sharply, so it is at this point that the membrane can be damaged.

Expansion tank selection

Choosing an expansion tank for heating is a responsible business. In this case, it is imperative to pay attention not only to its type and size, but also to the membrane - such indicators are important: resistance to the diffusion process, operating temperature range, durability, compliance with sanitary requirements.

Today on the market there is a wide range of expansion tanks for the heating system.

In addition, it is necessary to determine the ratio of the limits of the pressure range, which is the maximum permissible. It is imperative to clarify before buying a tank whether it complies with existing quality and safety standards.

Tank volume calculation

First of all, let us determine the dependence of the required volume and the parameters that affect it. When calculating, it must be borne in mind that the larger the capacity of the heating system and the higher the maximum temperature of the heat carrier in it, the larger the tank should be. The higher the permissible pressure in the heating expansion tank, the lower it can be. Of course, the calculation method is quite complicated, so it is better to consult a specialist. After all, a mistake in choosing an expansion tank can cause frequent actuation of the safety valve or other troubles.

The volume is calculated using a special formula. Here, the main value is the total volume of the coolant that is present in the heating system. This value is calculated taking into account the power of the boiler, the number and types of heating devices. Approximate values: radiator - 10.5 l / kW, underfloor heating system - 17 l / kW, convector - 7 l / kW.

To make a more accurate calculation of a device such as a vacuum expander for heating, the formula is applied: Tank volume = (Heating water volume * Heat carrier expansion coefficient) / Expansion tank efficiency. The expansion coefficient for water is 4% when it is heated to 95 degrees. Another formula is applied to determine the efficiency of the tank: Tank efficiency = (Highest system pressure - Initial pressure in the air chamber) / (Highest system pressure + 1).

Expansion vessel useful volume coefficients

Thus, the vacuum expansion tank for heating is selected taking into account the characteristics of strength and temperature, which should not be higher than the permissible values ​​at the connection point. The volume of the tank can either be equal to or be greater than the result that was obtained as a result of the calculations.

Expansion tank installation

Installation of the expansion tank of the heating system is done in accordance with the project and instructions. The best option for you is to have it done by a specialist. If this is not possible, then at least consult with him. The installation of an expansion tank for heating, if it is of an open type, is carried out at the highest point of the heating system. A closed tank can be placed almost anywhere, but not directly after the pump.

One of the options for installing an expansion tank in the heating system

It is necessary to pay special attention to such an issue as the fastening of the heating expansion tank, since the mass of the tank, which is filled with water, increases significantly. Also an important point is the possibility and convenience of service of the tank, free access to it.

Expansion tank maintenance

The role of a device such as an expansion tank of a heating system cannot be underestimated. The instruction of this device provides a list of rules for its maintenance. These include:

• Once every six months, it is necessary to check the tank for external damage - corrosion, dents, smudges. If suddenly such damage is found, then it is imperative to eliminate their cause.
• Once every six months, it is necessary to check the initial pressure of the gas space for compliance with the calculated indicator.
• The integrity of the membrane is checked once every six months. In case of detection of its violation, it is necessary to replace it (if such a possibility is provided).
• If the tank will not be used for a long time, then you need to keep it in a dry place, draining the water from it.

Next, how to check the heating expansion tank - its initial pressure of the gas space. To do this, disconnect the tank from the heating system, drain water from it, connect a pressure gauge to the nipple of the gas cavity. If the pressure is lower than that which was set at the same time when the expansion tank for heating was adjusted, the tank must be pumped through the same nipple with a compressor.

Pressure gauge readings for correct operation of the expansion tank

Checking the integrity of the membrane is also an important point. If suddenly, during the pressure check of the gas space after you have drained the water, air flows through the drain valve, and the pressure in the gas space has decreased to atmospheric, then the membrane is broken.

To replace the membrane, you need to go through several stages. First of all, the tank is disconnected from the heating system, then it needs to be drained. Further, the pressure of the gas cavity is released through the nipple. The diaphragm flange is dismantled. It is located in the area of ​​the pipe connection. The membrane that goes into the expansion tank device for heating is removed from the hole at the bottom of the housing.

Then you need to check the inside of the case so that there is no dirt and corrosion, if any, you need to remove them and rinse with water, and then dry. To remove corrosion, do not use products that include oils! The diaphragm holder is inserted into the hole at the top of the diaphragm. The bolt is screwed into the diaphragm holder, it is inserted into the body, and the holder is retracted into the hole in the bottom of the body. Then the holder is fixed with a nut. After that, the diaphragm flange is placed on the body.

At the present time, a membrane expansion tank has gained great popularity as a compensating device for a coolant. Gravity heating systems with natural circulation are rarely used, and therefore open containers are gradually becoming a thing of the past. Such devices are also needed by modern water supply systems, where pumping stations and indirect heating boilers are installed. This material will tell you how to choose and connect such a tank to a particular system.

The device and principle of operation of the membrane tank

Let's start with the fact that structurally devices intended for heating and water supply (hydraulic accumulators) have some differences and should not be confused with each other. At the same time, the principle of operation of the diaphragm tank is the same regardless of its design.

The general structure of such tanks is as follows: inside a sealed cylindrical metal body there is a rubber membrane (popularly called a "pear"). It is of two types:

• in the form of a diaphragm dividing the internal space approximately in half;
• in the form of a pear, with its base attached to the water inlet.

Note. The second type of diaphragm must be replaced by unscrewing the pipe flange. The first type cannot be replaced, only together with the body.

The difference between the vessels for different systems is that the membrane expansion tanks for heating systems are filled with a coolant that is in contact with the metal walls from the inside. In containers for water supply, water never comes into contact with metal, and in some models even the "pear" washing is provided. These modifications are recommended for use in drinking water supply networks.

Another difference is that membranes for expansion tanks for water are manufactured:

• from food grade rubber;
• adapted to a higher pressure than for heating.

Accordingly, the "pear" in the tank for heating systems is adapted to work at a higher temperature. The very principle of operation of the devices is simple: under the influence of external forces (thermal expansion or pump action), the container is filled with water and stretches the membrane to certain limits. The enlargement of the "pear" on the other hand limits the air under a certain pressure. To create this pressure, the tank device provides for a special spool.

When the external influence ceases and the pressure in the pipeline network drops due to the drawdown or cooling of the coolant, the membrane gradually pushes the water back into the system.

To begin with, a membrane expansion tank for water supply cannot be used in heating networks and vice versa. The reason is that each of the systems has its own pressure and temperature, as well as requirements for water quality. Meanwhile, they look very similar, manufacturers even manage to paint the bodies of the tanks in one color (most often - in red). How can you tell?

Each product has a plate with the words - nameplate. It contains all the information that we need. When the nameplate says that the maximum operating pressure is 10 bar, and the temperature is 70 ºС, then in front of you is an expansion tank for cold water supply. If the inscription says that the maximum temperature is 120 ºС, and the pressure is 3 bar, then this is a membrane tank for heating, everything is simple.

The second selection criterion is the volume of the tank, it is determined as follows:

• for the heating system: the total amount of coolant in the house network is calculated and a tenth is taken from it. This will be the capacity of the tank with a margin;
• for water supply: here the volume of the vessel must ensure the comfortable operation of the water pump. The latter should not be switched on and off more often than 50 times per hour. A sales representative will help you to more accurately determine the number;
• for hot water supply (boiler tank). The principle is the same as with heating, only you need to take a tenth of the capacity of the indirect heating boiler;

Attention! To compensate for the thermal expansion of water in the boiler, it is necessary to take a tank intended for water supply.

How to install a diaphragm tank correctly

Not only the performance of a particular system, but also the service life of the tank depends on how correctly the membrane-type expansion tank is installed and connected. The first thing to do is to place and fix the tank to the wall or floor in the position required by its operating instructions. If there is nothing about this in it, then below in the text we will clarify this issue.

The second point is that a shut-off valve must be installed on the supply pipe. By closing it, you can always remove the diaphragm pressure vessel for repair or replacement. And in order not to flood the floors of the furnace room, between the shut-off valve and the container, it is worthwhile to provide a drain fitting and another tap. Then it will be possible to empty the tank before removal.

Heating tanks

In a situation where the documentation for the tank does not prescribe how to correctly orient it in space, we advise you to always put the tank with the inlet pipe down. This will allow for some time to extend his work in the heating system in the event that a crack appears in the diaphragm. Then the air at the top will not rush to penetrate into the coolant. But when the tank is turned upside down, the lighter gas will quickly flow through the crack and enter the system.

It does not matter where to connect the tank supply - to the supply or return, especially if the heat source is a gas or diesel boiler. For solid fuel heaters, the installation of a compensating vessel on the supply is undesirable; it is better to connect it to the return. Well, at the end, adjustment is required, for which the device of the expansion membrane tank provides a special spool on top.

The fully assembled system must be filled with water and vented. Then measure the pressure around the boiler and compare it with the pressure in the air chamber of the tank. In the latter, it should be 0.2 bar less than in the network. If this is not the case, it must be ensured by deflating or pumping air into the membrane water tank through the spool.

Water supply tanks

Unlike expansion tanks for heating, hydraulic accumulators can be oriented in space as you like, this does not matter much. It will also be useful to install fittings on the inlet to the tank to isolate it from the network and empty it.

But the setting for cold and hot water supply is different. The fact is that the pressure in the pipelines is created by a pump, which has an upper and lower shutdown threshold. It is necessary to navigate by them. It is necessary to set the pressure in the membrane tank operating in the cold water supply circuit by 0.2 bar less than the lower threshold for turning off the pump. This will avoid water hammering in the system.

As for the hot water supply, here the air pressure in the tank should be 0.2 bar higher than the upper shutdown threshold of the pumping station. This is necessary so that water does not stagnate in the container. You can find out more useful information by watching the video:

Conclusion

It would seem that such a simple unit as a water tank, but requires so much meticulousness in the little things. In fact, a serious approach is needed when installing any element of the house network, otherwise the same minor troubles will befall you very soon.

Due to temperature fluctuations, the volume of the heating system coolant may change, which can lead to accidents. Therefore, everything must be done to make it work stably and this does not happen.

For this, special devices are used, for example, a diaphragm expansion tank. It is one of the key components of the heating circuit.

Purpose, pros and cons

When the coolant heats up, the pressure in the heating system circuit and boilers increases due to an increase in the volume of liquid. Since it is an incompressible medium, and the system itself is sealed, this can lead to breakage of pipes or boilers.

Some people believe that to solve the problem, it is enough to install a valve to squeeze out the excess volume of heated media, but this is not the case. When cooled, the liquid will be compressed, and air will enter the circuit in its place, which will become an obstacle to circulation. Therefore, the air will need to be constantly drained from the radiators, and it will be very expensive to add a new coolant and heat the water.

For this reason, it is recommended to install a membrane expansion tank for heating. It is a reservoir connected by a pipe to the system. Excessive pressure in it will be compensated for by volume, which will provide the circuit with full operation. The expander takes in a certain amount of liquid when the volume and pressure increase, and then, when these indicators decrease, returns it back. Such devices differ from similar devices of another type. a number of advantages:

• they can be used in any water, even if it contains a lot of calcium;
• allowed to be used for drinking water;
• have a large usable displaced volume (compared to tanks without a membrane);
• air pumping is required in a minimum amount;
• installation is quick and low-cost;
• operating costs will be minimal.

But it has an expansion tank and disadvantages. Sometimes you can run into problems when installing it, because it is quite large. Heat loss increases due to the fact that the coolant gives off heat to the expansomat.

In addition, there is an increased risk of rust formation in such devices. To avoid uncontrolled heat loss, it is recommended to insulate the device.

Choosing an expansion tank for heating and water supply systems

How and where is the expansion tank installed for heating

Product design

In rooms, heating networks can have open and closed circuits. The first type is used in centralized networks, so that it is possible to directly take water for hot water needs. The devices are placed in the upper part of the circuit. Expansion tanks will not only allow you to control the process of pressure drops, but will also perform the function of separating air from the system. If it belongs to the closed type, then a design with a membrane inside is used.

The expansion tank of the membrane type has a relatively simple device. It includes a water reservoir and a rubber membrane that can be balloon or diaphragm.

If the membrane belongs to the first type, then the coolant is located inside the rubber cylinder, and outside there is nitrogen or air. If necessary, such a part can be replaced, which will save on repairs and not change the entire device.

The diaphragm diaphragm for the expansion tank is a non-removable partition based on a thin metal or elastic polymer.

It has a small capacity and compensates for small pressure drops. If it breaks down, it is impossible to replace it, so you will have to change the tank completely. But compared to a balloon membrane, it is cheaper.

Expansion tank. Operating principle, selection, pumping pressure

Principle of operation

For each system, the gas pressure is adjusted according to the instructions for the device. The type of membrane does not affect the efficiency of the device. But if it belongs to the balloon type, more heat-transfer fluid can be placed in the tank. The principle of operation of the diaphragm expansion tank of the heating system for structures of different types does not differ:

Constant pressure is automatically regulated. For the system to work stably, you need to choose the right tank and make calculations. The required pressure will not be able to form if the tank turns out to be larger than necessary, and if it is smaller, it may not hold the excess liquid. This can cause an accident.

Selection rules

In order for a product to work fully, it is necessary not only to correctly select it in terms of volume, but also to take into account its other characteristics. You should pay special attention to the following nuances:

Now on the market you can see a large number of models of Russian and foreign production. They differ in cost, while the suspiciously low price should alert you. It may be due to the fact that low-quality materials of Chinese origin were used in the production. Domestic models are much better in quality, they are cheaper than foreign counterparts from well-known brands, but they are not inferior to them in terms of characteristics.

As already mentioned, the main characteristic that you need to focus on when buying a tank is its volume. Some experts recommend choosing products whose size is within 10% of the total volume of the coolant in the heating system. The fact is that the coefficients of thermal expansion, even at high heating, cannot be higher than 0.08. Therefore, calculations should be carried out as accurately as possible, taking into account indicators such as:

• the maximum allowable pressure of the heating system;
• coolant volume;
• initial pressure in the tank;
• thermal expansion coefficient.

When selecting the volume, you must take into account all the nodes of the heating system. This can be found out by examining the project documentation. If it is absent, then the calculation is allowed to be performed approximately, being guided by the fact that 15 liters of water will fall on 1 kW. The thermal expansion coefficient of the coolant is determined using the composition of the liquid. In apartment buildings, it often contains glycols, which improve its performance.

Also, the coefficient can be calculated from the temperature of the coolant. The ultimate pressure of the system is determined using the minimum value allowed for the components. The transition valve is adjusted to it. The initial pressure in the system, provided the coolant is cooled, corresponds to the minimum pressure. On some devices, it is regulated by inflating or bleeding air. The pressure in the tank is controlled by installing a pressure gauge.

The use of a membrane tank for heating has a number of limitations, depending on the manufacturer, design and material of manufacture. In some cases, the requirements for the composition of the coolant are very strict. In particular, this concerns the limitation of the amount of antifreeze and ethylene glycol in its composition.

In addition, expansion vessels cannot be used when the pressure limits are exceeded. Also, it is imperative that a security group be established that limits and controls it.

Installation requirements

It is not so difficult to install a membrane tank with your own hands; it is not necessary to involve a specialist for the work. Installation requirements are as follows:

If the container has a volume of 30 liters or more, it is prohibited to attach it to supporting structures. Most often it is equipped with special legs and is placed on the floor. When installing, it is recommended to observe such tips:

• the branch pipe must have a circumference of three quarters, respectively, a similar threaded channel must be present in the return;
• installation is carried out so that parts of the system or other objects do not interfere with work;
• it is recommended to use paronite gaskets that are resistant to high temperatures or pressure;
• in order to regulate or maintain the pressure in the gas compartment, the expander must be equipped with an air valve.

If the system is closed, then every time it is turned on, a high pressure is applied to the diaphragm. Therefore, you should check its condition at least once every 2 years and, if necessary, replace it. In some cases, everything changes completely.

During installation, gross mistakes must not be made, otherwise the equipment will not function normally. The most common miscalculation is the incorrect indication of the maximum pressure in the gas compartment, which is about 90% of the critical one. If this is allowed, the membrane will not expand towards the compartment. As a result, the pipe will burst, because of which the heating batteries will not be able to work. To correct the error, you need to install a certified pressure gauge. You also need to make sure that there is no tank in the boiler itself. If, after calculations, it is established that its volume is small, then additional capacity will be required.

The expansion vessel in the heating system is very important. It depends on him how correctly it will work. It is not difficult to install it, but you need to pay special attention to this process, since even a small oversight can cause an emergency in the future.

The volume of the coolant changes depending on the change in temperature conditions, which can lead to dangerous consequences. For safe and long-term operation of the coolant, it is necessary to maintain its stable characteristics. A diaphragm expansion vessel can be used for this.

Purpose and design features

In heating systems, fluids that are in the process of weak compression act as heat carriers. For the safe operation of the heating system, it is necessary to use a stabilizing device - a membrane expansion tank, which is able to receive a certain amount of liquid in the process of increasing pressure and volume, and then return it to the circulation circuit when these indicators decrease.

Diaphragm expansion vessels have a number of advantages over other devices for the same purpose, namely:

• suitable for any water, even if it contains a large amount of calcium;
• safe to use for drinking water;
• have a larger displaced useful volume than a pressure tank without a membrane;
• minimum air pumping is required;
• economically and quickly assembled;
• low operating costs.

However, these devices also have disadvantages, namely:

• the large size of the expansion tank makes the installation process quite problematic;
• due to the release of its heat by the coolant to the expansomat, heat loss increases;
• the risk of rust formation increases.

To avoid uncontrolled loss of heat, experts advise to insulate the device.

Differences from a hydraulic accumulator

The design of sealed expansion tanks is similar to the design of hydraulic accumulators, however, the purpose of these devices is different. The expansion vessel compensates for the expansion of the water due to heating in the heating system. The hydraulic accumulator accumulates the volume of water under pressure in a water supply system with a pressure pump in order to reduce the frequency of activation of this pump and smooth out water hammer. In addition, more often inside the accumulator there is a pear made of food-grade rubber. It is she who is pumped with water, as a result, the water does not come into contact with the tank body. The expansion tank for heating systems is made with a membrane made of technical rubber. It divides the body into two compartments, and the coolant has contact with the body.

Device and principle of operation

The membrane tank is a hermetically sealed metal container, divided into two compartments (chambers) by an elastic membrane. One of these chambers is a pneumatic chamber that contains gas or air under pressure. The second chamber, the hydrochamber, receives the coolant.

The device operates as follows:

• the air pressure, which is in equilibrium, in the pneumatic chamber compensates for the fluid pressure in the heating system, the volume of the coolant and the hydrochamber is minimized;
• when the fluid pressure rises in the system, including during heating, the pressure also increases in the hydrochamber, where the excess coolant enters;
• due to the elasticity of the membrane, the volume of the pneumatic chamber decreases, which is accompanied by an increase in gas pressure;
• when the pressure in the pneumatic chamber increases, the increase in pressure in the hydraulic chamber is compensated, and the system returns to a state of equilibrium.

With a decrease in the pressure of the coolant in the system, the opposite actions take place. The gas (air) compressed in the pneumatic chamber expands and displaces the liquid from the hydraulic chamber into the system until the pressure difference is restored. The design makes it possible to exclude the possibility of contact between the coolant and air, reducing the likelihood of rusting not only in the tank, but also in other parts of the heating system - the pipeline, the boiler. Sealed expansion tanks are equipped with safety valves to limit the maximum pressure in the heating system to an acceptable level. This also characterizes the tank as a protection device for the heating system.

Types and selection criteria

To compensate for the volume of the coolant in the system during temperature changes, two types of expansion tanks are used: open and closed (sealed).

Open expansion tanks are widespread, but have the following disadvantages:

• high installation costs, since such tanks are mounted at the top point of the system to create the required level of increased pressure;
• it is necessary to constantly monitor the liquid level;
• there is a risk of rust in the system due to prolonged contact of the heating coolant with air.

Sealed expansion tanks do not have these disadvantages. For heating systems, tanks are produced that differ in the use of a membrane. Membranes are divided into balloon and diaphragm types. A balloon membrane is a container installed inside the tank, made of high quality rubber that can withstand significant temperature fluctuations. The flange mounting of such a membrane will allow it to be replaced quickly and easily.

Balloon diaphragms have such advantages as:

• a wide range of operating pressures, making it possible to use a sealed expansion tank;
• the ability to change the membrane, which helps to make the repair of this device cheaper and faster;
• simple setting of the minimum pressure for any system.

The diaphragm membrane is a non-removable baffle, which is most often made of elastic polymer or thin metal. This diaphragm has a low intrinsic capacity and the ability to compensate for small pressure drops in the system. If such a tank fails, it will need to be completely replaced. One of the perks of this device is its low price. In addition, the tank with a diaphragm membrane is simple in design and reliable in operation.

Choosing the right expansion tank means ensuring the safe operation of the heating system, therefore when choosing an expansion tank, you should pay attention to the following main characteristics:

• membrane material, its resistance to high absolute values ​​of temperatures, pressures and differences in these indicators;
• body material and coating, resistance to rust;
• compliance with sanitary and hygienic standards;
• execution (installation method).

Restrictions

Manufacturers impose certain restrictions on the use of membrane expansion tanks, which depend on the design and materials used in the manufacture of the device. Manufacturers have clear requirements for the properties and composition of the liquid in the heating system. The content, for example, of ethylene glycol in the antifreeze solution is limited. The use of a diaphragm expansion vessel at pressures exceeding the permissible standards is prohibited. It is mandatory to install a safety group that controls and limits the pressure in the tank. In the heating systems of autonomous heating apartments and private houses, equipment is used, the working pressure of which is at least 3 bar.

Volume calculation

Volume is the main characteristic by which the expansion tank is selected. Many sources advise choosing the volume of the expansion tank within 10% of the total volume of the coolant in the heating system. This method of determining the capacity of the device is based on the fact that the coefficients of thermal expansion of the coolant, even with a glycol content of up to 90% and heating +100 degrees, do not exceed 0.08. This calculation method does not take into account the pressure in the system, therefore it can give inaccuracies. There is a more accurate method for calculating the volume of a diaphragm expansion tank. Here the ratio is used:

V = C * Bt / (1 - (Pmin / Pmax)), where

• C is the volume of the coolant in the system;
• Bt is the coefficient of thermal expansion of the coolant;
• Pmin - initial pressure in the tank;
• Pmax - allowable pressure in the system.

The volume of the coolant in the heating system is determined taking into account all its nodes. This parameter is obtained from the design documentation for heating. If this is not possible, you can use an approximate calculation, which is based on the fact that the volume of the coolant in heating systems is related to the heating power - for every kW there are 15 liters of liquid. The coefficient of thermal expansion of a liquid is determined using its composition - most often, in heating systems of apartments and houses, it is possible to add glycols to the water to improve its characteristics. This coefficient may also depend on the temperature of the coolant. The required values ​​can be found in the tables for the volume of water in the pipe.

The maximum pressure in the heating system is determined using the minimum of the values ​​that are allowed for different nodes. The transition valve is tuned to it. The initial pressure in the heating system with cooled heat carrier corresponds to the setting (minimum) pressure. For many devices, it can be precisely controlled by common means (bleeding air from the tank or pumping it up with a pump). The pressure in the tank is monitored during the installation of a pressure gauge on it. The calculated data will give an increase in the volume of the coolant in the system during its heating. To select a tank, the fill factor is rounded up. The coefficient depends on the maximum and initial pressure and can be found using tables provided by manufacturers or in special literature.

Installation

It is not difficult to install a diaphragm expansion tank, but it is better to entrust it to a specialist. First of all, the instructions for the device must be used. When installing this device in a heating system, it is important to carefully check the tightness of the connections. The expansion vessel must not be opened or disassembled. It is simply connected to the pipeline closest to the boiler. To prevent pressure build-up, safety devices are installed.

When installing the tank, the following rules should be taken into account:

• the tank is installed before the bifurcation;
• the temperature in the room must be constantly above 0;
• you need to double-check all calculations before installing;
• a tank with a volume of more than 30 liters is not mounted on the walls, but placed on legs;
• to control the pressure at the outlet of the tank, a pressure gauge is installed, at the inlet - a check valve (if there is no pump);

• the device must be located in a place that is comfortable for maintenance and adjustment;
• when connecting the tank to the wall, the bracket must maintain a height that will be convenient for access to the shut-off valves and to the air space;
• the underwater pipe and the crane should not overload the expansion tank with their weight, the liner must be strengthened separately;
• to the membrane tank located on the floor, it is impossible to lay the supply line across the floor across the passage;
• there must be a distance between the wall and the container for inspection.