What pressure should be in the expansion tank. Membrane expansion tank of the heating system: the principle of operation, how to choose. Expansion membrane tank for water supply: functional features and subtleties of connection Membrane tank for heating

The volume of the coolant varies depending on the shift 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 tank can be used for this.

Purpose and design features

In heating systems, the heat carriers are liquids that are in the process of weak compression. For safe work 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.

Membrane expansion tanks have a number of advantages over other devices of the same purpose, namely:

suitable for any water, even if it contains a large number of calcium;
safe to use for drinking water;
have a larger useful volume to be displaced than a pressure tank without a membrane;
minimal air intake is required;
economical and fast installation;
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 heat by the coolant to the expansion mat, heat losses increase;
increased risk of rust formation.

To avoid uncontrolled heat loss, experts advise insulating the device.

Differences from the 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 tank compensates for the expansion of water due to heating in the heating system. The hydraulic accumulator accumulates the volume of water under pressure in the water supply system that has a pressure pump in order to reduce the frequency of switching on 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, water does not come into contact with the tank body. 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

A membrane tank is a hermetically sealed metal container divided into two compartments (chambers) by an elastic membrane. One of these chambers is the pneumatic chamber, which contains pressurized gas or air. The coolant enters the second chamber - the hydro-chamber.

The device works as follows:

the air pressure, which is in a state of 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 pressure of the liquid rises in the system, including when heated, there is an increase in pressure 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, opposite actions occur. 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 eliminates the possibility of contact between the coolant and air, reducing the likelihood of rust not only in the tank, but also in other parts of the heating system - pipelines, boilers. 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 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 of the system to create the required level of increased pressure;
it is necessary to constantly monitor the level of the liquid;
there is a risk of rust in the system due to prolonged contact of the heated coolant with air.

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

Balloon-type membranes have such advantages as:

a wide range of operating pressures, making it possible to use a hermetic expansion tank;
the possibility of changing the membrane, which helps to make repairs this device cheaper and faster;
simple setting of the minimum pressure for any systems.

The diaphragmatic membrane is a non-removable septum, which is most often made of an elastic polymer or thin metal. This membrane is characterized by low self-capacitance 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 privileges of this device is its low price. In addition, the diaphragm tank is simple in design and reliable in operation.

Choosing the right expansion tank means ensuring the safety 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, rust resistance;
compliance with sanitary and hygienic standards;
execution (mounting 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 impose clear requirements on the properties and composition of the fluid in the heating system. The content, for example, of ethylene glycol in the antifreeze solution is limited. The use of a diaphragm expansion tank at temperatures exceeding allowable norms pressure is prohibited. It is mandatory to install a safety group that controls and limits the pressure in the tank. In heating systems of apartments autonomous heating and private houses, equipment is used, the working pressure of which is at least 3 bar.

Volume calculation

The volume is main characteristic, according to which the expansion tank is selected. Many sources advise choosing the volume of the expansion tank within 10% of the total volume of 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 of +100 degrees, do not exceed 0.08. This calculation method does not take into account the pressure in the system, so it may give inaccuracies. There is a more accurate method for calculating the volume of a membrane expansion tank. The ratio is used here:

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 is the initial pressure in the tank;
Pmax - allowable pressure in the system.

The volume of 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 coolant in heating systems is related to the heating power - for every kW there is 15 liters of liquid. The coefficient of thermal expansion of a liquid is determined using its composition - most often, in the heating systems of apartments and houses, it is possible to add glycols to water to improve its characteristics. This coefficient may also depend on the temperature of the coolant. You can find the required values in the tables of the volume of water in the pipe.

The maximum pressure in the heating system is determined using the minimum of the values \u200b\u200bthat are allowed for different nodes. The transfer valve is adjusted exactly to it. The initial pressure in the heating system with a cooled coolant corresponds to the setting (minimum) pressure. For many devices, it is possible to accurately regulate it by common means (bleeding air from the tank or pumping it up with a pump). The pressure in the tank is controlled 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 specialized literature.

Installation

Installing a membrane expansion tank is not difficult, 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 tank must not be opened or dismantled. It is simply connected to the pipeline closest to the boiler. Safety devices are installed to prevent pressure build-up.

When installing the tank, the following rules should be considered:

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

the device must be in a place comfortable for maintenance and adjustment;
when attaching the tank to the wall, it is necessary to maintain a height on the bracket that will be convenient for access to the shutoff valves and to the airspace;
the underwater pipe and the crane should not overload the expansion tank with their weight, the liner must be strengthened separately;
to a membrane tank located on the floor, it is impossible to lay an eyeliner across the floor across the passage;
there must be a distance between the wall and the tank for inspection.

A device such as a membrane expansion tank of a heating system is used to compensate for changes in water volumes. Such changes are usually caused by its heating. The body of the membrane expansion tank of the heating system is divided into two parts by an elastic membrane. In one of them - a liquid substance, in the second - a gas. The first part is coolant, and the second is filled with air under high pressure or nitrogen.

Membrane expansion tank of the heating system

Where membrane expansion tanks are used and their advantages

Membrane tanks are used in the following areas:

Heating systems with autonomous heat sources;
Heating systems that are connected to centralized heat supply networks according to an independent scheme;
On systems using solar collectors and heat pumps;
They can also be used in other systems where there are closed circuits and a variable temperature of the working medium.

There are several advantages to using membrane tanks. Among them:

The suitability of membrane tanks for absolutely any water - even if it contains a lot of calcium;
Suitability of butyl and natural rubber membranes for drinking water applications;
Ease of membrane replacement;
A membrane tank, in comparison with a pressure tank without a membrane, has a large displaced useful volume;
There is no risk of contamination of drinking water;
No loss of coolant to evaporation;
Air pumping is minimal;
Mounting such a tank is economical and relatively fast;
Operating costs are low.

Peculiarities

The membrane expansion tank of the heating system will show the purpose of the tank: at all stages of operation, it must regulate the balance of the pressures of the cavities and compensate for excessive pressure or even its differences in the heating system. Thus, the membrane tank prevents increased loads in the heating system circuit, and, accordingly, emergencies with malfunctions.

The membrane tank for heating can be with a replaceable and non-replaceable membrane. The main feature of the first type is that the heat carrier is completely located in the flexible container of the membrane, thus not being able to interact with the inner steel surface. All actions for the installation and dismantling of the membrane are carried out through the flange, which is bolted.

If you have a tank with a fixed diaphragm in front of you, then it will have an internal cavity divided into two parts. The membrane in this case is diaphragmatic, non-replaceable and rigidly fixed.

Of course, the choice of a membrane tank for heating should be made exactly for a specific system, it depends on the amount of coolant.

If your expansion tank has insufficient volume, then this can lead to negative consequences - the appearance of cracks, the flow of hot water through the threads. Also, the pressure in the system may decrease below the minimum allowable, because of this, air can get inside the tank. That is why the choice of a tank should be based on its exact compliance with the maximum possible pressure parameters.

Membrane expansion tank for heating is used in closed system circulation of liquids in order to compensate for the thermal expansion of the heat carrier due to changes in the temperature of the liquid, maintain optimal pressure heat carrier and prevent water hammer. The water chamber and the gas chamber in constant mode have the same pressure, so the tightness in the system is not violated.

Water circulates without impurities of oxygen and other aggressive gases, so there will be no corrosion of the tank, which will allow it to work for a long time. The pressure expansion tank is located in the boiler room. Therefore, it does not require frost protection.

Expansion heating tank in the boiler room

The choice of tank is individual for each system, but, in general, several features must be taken into account. The initial pressure in a device such as a membrane tank for heating, which is connected to cold system, should be equal to the static pressure in the system plus 30-50 kPa. In addition, a reserve volume of heat carrier must enter the tank, which is required to compensate for leaks.

Also, the expansion tank must be selected so that, when taking the maximum increase in volume corresponding to maximum temperature heat carrier, the pressure did not exceed the maximum allowable value.

To protect the system with a closed circuit and a tank from overpressure, safety valves must be installed.

Installation of a membrane expansion tank

Membrane expansion tanks are first supplied with an excess initial gas pressure, it fills the entire volume with itself. Before installing the expansion tank, it must be inflated to the pre-calculated pressure. You need to install safety valve. It is also recommended to install a drainage device in front of the tank.

Installation instructions for the expansion tank must be included in the technical documentation. Yes, and to install, as a maximum, a specialist should, at least, it is best to consult with him on this important issue. When installing the tank, there are a few things to consider:

It is best if the tank is installed before the branching of the water supply. The room should be able to drain water and feed the system. Since freezing of water is unacceptable, the temperature in the room must be above 0.
The place where you are going to mount the tank must be load-bearing, since the tank should not receive additional load from other devices, pipes, etc. If you have a tank with a volume of 8-30 liters, then it is mounted on the wall, and if this volume is larger, then it is placed on legs.
Before installation, make sure that the calculations are correct!
The tank must be grounded so that there is no electrolytic corrosion process.
At the inlet to the tank, a check valve must be installed if it is not in the pump design. At the outlet - a device such as a pressure gauge to be able to control the pressure and an automatic valve to release air.

If there is no tank stop valves, then you need to put it at the installation site.

The expansion tank is a very important element in the heating system. With it, pressure build-up in the heating system is prevented when it heats up. Tanks can be open and closed. Open tanks have a number of disadvantages that do not exist in membrane tanks. They are bulky, have a large heat loss, do not work under great pressure. Membrane tanks are more perfect, and they do not have the disadvantages that open ones have.

What is a diaphragm expansion tank

An expansion tank is an important element in heating, because it prevents the coolant from boiling, which can lead to bad consequences.

Such tanks can be used in different systems:

with heat pumps and solar collectors;
With autonomous source heat;
connected to the district heating network according to an independent scheme;
with closed loops.

Membrane tanks regulate the pressure in the heating system in case of its increase and in case of pressure drops, which prevents emergency dangerous situations and sometimes malfunctions of heating systems.

The expansion tank can be with fixed and replaceable baffle. The first, made with an internal cavity divided into two parts by a securely fixed membrane, which is located along the perimeter of the section.

Tanks with a replaceable baffle differ from fixed ones in that the coolant is in a membrane tank and does not come into contact with the steel surface. Mounting and dismantling of the membrane quite simple, through a flange that is bolted.

Advice. When installing a membrane tank, it is necessary to securely attach it, because during operation, the mass of the tank increases.

Advantages of membrane expansion tanks

Expansion tanks have a huge number of advantages:

do not pollute water;
low costs during operation;
easy installation;
safety, reliability;
installation in any part Houses;
the impossibility of pouring water from the tank;
no heat loss;
minimum air supply;
natural rubber and butyl membranes can be used in drinking water supply;
apply to any type of water;
convenient to use;
radiator and boiler due to lack of contact between water and air last longer, than usual.

Expansion membrane tanks are used in closed heating systems and ensure reliable operation of the boiler.

Advice. When choosing a membrane tank, you should give preference to closed tanks, which are much better than open ones.

The design of the expansion membrane tank

flat or balloon metal body, internally separated by a rubber membrane. One part contains air or gas, which is compressed to a certain required level. The level of air compression can be found in the passport. The other part of the tank in working condition will be filled with water and due to this, the level of gas compression will be the same as in the entire heating system. Tank compressor maintains pressure in the air chamber.

One of the most important element of a membrane expansion tank is the membrane, which can be two types:

balloon;
diaphragmatic.

Diaphragm valves are used in tanks with a small volume and cannot be replaced. Balloon can easy to replace if necessary, this type of expansion tank is more reliable due to the fact that the water is in the membrane and does not touch the tank body.

Advice. When choosing a membrane expansion tank, it is necessary to pay attention to the material from which the membrane is made.

Choosing a membrane tank

In heating systems, the membrane load, as well as the expansion of water, does not change very significantly, but the heating temperature of the liquid can be approximately 90 ° C.

Choosing an expansion membrane tank, Special attention need to be given to the material from which the membrane is made. The material must be of high quality, reliable and resistant to high temperatures and drops.

You should also pay attention to the following characteristics of the membrane:

range operating temperatures;
long life time;
sanitary and hygienic requirements;
impact resistance high temperatures;
dynamism.

Advice. When choosing an expansion membrane tank, it is necessary to select tanks with a durable and reliable body so that it lasts longer.

Calculation of the volume of the expansion membrane tank

In order to determine the volume of the expansion membrane tank, you need to determine the total volume of the heating system, which consists of several volumes:

pipeline;
heating device;
boiler.

The easiest way to determine the required tank volume is calculate 10% of the total volume of the heating system. If it is 500 liters, then you need a tank with a volume of 50 liters.

If the volume of the expansion membrane tank is less than necessary, then this will lead to bad consequences. Cracks will begin to appear, hot water will leak through the thread, and the tank itself can deteriorate very quickly and it will have to be changed.

The membrane tank is selected individually for each heating system.

Advice. If safety valves are installed in a closed heating system, pressure build-up can be avoided and the entire system protected.

Installing an expansion membrane tank

To install and connect a membrane tank to the heating system, you will need skill and knowledge. You should not take on the installation of the tank yourself if you are not sure that everything will be done correctly.

For installation you will need:

stepped key;
gas key;
plastic pipes;
wrench.

When installing a membrane expansion tank in the heating system, you need to very carefully and carefully check tightness connections.

The expansion tank must be sealed, it cannot be dismantled, opened, it is simply connected to pipeline which is closest to the boiler . It is also necessary to install safety devices to prevent pressure build-up.

When installing the tank, take into account a few rules:

Advice. In order to extend the service life of heating systems, it is not necessary to use water with oxygen impurities and aggressive gases.

Possible breakdowns

The most common breakdown of a membrane expansion tank is considered to be membrane rupture in case of exceeding the permissible pressure and uneven loads. Replaceable membranes break much more often than pressed ones, because for the latter, more durable materials are used, since they can be changed at any time, but pressed ones are not.

Due to the rupture of the membrane, if it is not replaced, the tank will eventually falls into disrepair because water gets on inner surface tank and it becomes unusable under the influence of corrosion.

The quality and reliability of the membrane expansion tank is also affected by the choice of material from which it is made. quality material will cost much more.

Membrane expansion tanks are an important part of the heating system, because it is thanks to them that pressure control in the heating system is possible. To select a tank, you must consider individual characteristics systems and choose for it.

Due to temperature fluctuations, the volume of the heat carrier of the heating system may change, which can lead to accidents. Therefore, everything must be done so that it works stably and this does not happen.

For this, apply special devices e.g. diaphragm expansion vessel. 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 think that to solve the problem it is enough to put a valve to squeeze out the excess volume of the heated carrier, but this is not so. When cooled, the liquid will shrink, and air will enter the circuit in its place, which will become an obstacle to circulation. Therefore, air will need to be constantly bled from radiators, and adding a new coolant and heating water will be very expensive.

For this reason, it is recommended to install a membrane expansion tank for heating. It is a tank connected with a pipe to the system. Excessive pressure in it will be compensated by volume, which will ensure full operation of the circuit. The expander takes in a certain amount of liquid when the volume and pressure increase, and then, when these indicators decrease, it 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 use for drinking water;
have a large useful displaced volume (compared to tanks without a membrane);
air pumping is required in a minimum amount;
installation is fast and does not require large expenses;
operating costs will be minimal.

But it has an expansion tank and cons. Sometimes you can run into problems when installing it, because it is quite large. Heat losses increase due to the fact that the coolant gives off heat to the expander.

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

The choice of expansion tank for heating and water supply systems

How and where is the expansion tank for heating installed

Product design

In rooms, heating networks can have open and closed circuits. The first type is used in centralized networks, thanks to which it is possible to directly withdraw water for the needs of hot water. 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 refers to closed type, then a design with a membrane inside is used.

The expansion tank of the membrane type device is relatively simple. It includes a water tank and a rubber membrane, which can be balloon or diaphragm.

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

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

It has a small capacity and compensates for minor pressure drops. If it fails, 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. Principle of operation, 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-carrying liquid can be placed in the tank. The principle of operation of the membrane expansion tank of the heating system at structures different kind is not different:

The constant pressure is adjusted automatically. In order for the system to work stably, you need to choose the right tank and make calculations. The necessary pressure cannot be formed if the tank is larger than necessary, and if it is smaller, it may not contain excess fluid. This can cause an accident.

Selection rules

In order for the product to work fully, it is necessary not only to correctly select it by volume, but also to take into account its other characteristics. 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 a suspiciously low price should alert. 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 coolant in the heating system. The fact is that the coefficients of thermal expansion, even with high heating, cannot be higher than 0.08. Therefore, calculations should be carried out as accurately as possible, taking into account indicators such as:

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

When selecting the volume, it is necessary to take into account all the nodes of the heating system. This can be found out by studying the project documentation. If it is absent, then it is allowed to perform an approximate calculation, focusing on the fact that 15 liters of water will fall on 1 kW. The coefficient of thermal expansion of the coolant is determined using the composition of the fluid. In apartment buildings it often contains glycols which improve its performance.

Also, the coefficient can be calculated from the temperature of the coolant. The system pressure limit is determined using the minimum value allowed for the nodes. A transfer valve is set on it. The initial pressure in the system, under the condition of a cooled coolant, corresponds to the minimum pressure. On some devices, it is regulated by pumping or bleeding air. In the tank, the pressure 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 applies to limiting the amount of antifreeze and ethylene glycol in its composition.

In addition, expansion tanks must not be used when the marginal indicators pressure. Also, a security group must be installed without fail, which limits and controls it.

Installation Requirements

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

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

the branch pipe must have a three-quarter circumference, 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;
to regulate or maintain pressure in the gas compartment, the expander must be equipped with an air valve.

If the system is closed, then every time after it is turned on, the membrane is high pressure. Therefore, it should be checked at least once every 2 years and, if necessary, replaced. In some cases, everything changes completely.

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

The expansion tank in the heating system is very important. It depends on him how correctly it will work. Installing it is not difficult, but special attention must be paid to this process, since even a small oversight can cause an emergency in the future.

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

Purpose, pros and cons

they can be used in any water, even if it contains a lot of calcium;
allowed to use for drinking water;
have a large useful displaced volume (compared to tanks without a membrane);
air pumping is required in a minimum amount;
installation is fast and does not require large expenses;
operating costs will be minimal.

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

The choice of expansion tank for heating and water supply systems

How and where is the expansion tank for heating installed

Product design

In rooms, heating networks can have open and closed circuits. The first type is used in centralized networks, so that you can directly take water for hot water needs. 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 is of a closed type, then a design with a membrane inside is used.

The expansion tank of the membrane type device is relatively simple. It includes a water tank and a rubber membrane, which can be balloon or diaphragm.

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

Expansion tank. Principle of operation, selection, pumping pressure

Principle of operation

Selection rules

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

When selecting the volume, it is necessary to take into account all the nodes of the heating system. This can be found out by studying the project documentation. If it is absent, then it is allowed to perform an approximate calculation, focusing on the fact that 15 liters of water will fall on 1 kW. The coefficient of thermal expansion of the coolant is determined using the composition of the fluid. In apartment buildings, it often contains glycols, which improve its performance.

In addition, expansion tanks cannot be used when the pressure limits are exceeded. Also, a security group must be installed without fail, which limits and controls it.

Installation Requirements

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

the branch pipe must have a three-quarter circumference, 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;
to regulate or maintain pressure in the gas compartment, the expander must be equipped with an air valve.

If the system is closed, then each time after it is turned on, a high pressure is applied to the membrane. Therefore, it should be checked at least once every 2 years and, if necessary, replaced. In some cases, everything changes completely.