Diaphragm heating tank operating principle. Expansion tank for closed heating: device and principle of operation. Setting the pressure in the expansion tank
Today no one will be surprised by an autonomous water supply system. Such designs are very convenient and practical, but their operation often requires devices that a person using only centralized water supply, may simply not know. For example, an autonomous water supply system will long time work smoothly only if it is included expansion tank for water supply. Modern industry produces many of the most different models such devices. To choose for yourself best option, it is necessary to navigate the types of equipment and have a good understanding of the principle of its operation.
Design and functions of this equipment
Types of membrane tanks
There are two main types of expansion membrane equipment.
Device with replaceable membrane
The main distinguishing feature is the ability to replace the membrane. It is removed through a special flange, which is held on by several bolts. It should be taken into account that in large-volume devices, in order to stabilize the membrane, it is additionally secured with its rear part to the nipple. Another feature of the device is that the water filling the tank remains inside the membrane and does not come into contact with the inside of the tank. This protects metal surfaces from corrosion, and the water itself from possible contamination and significantly extends the life of the equipment. Such models are produced in both horizontal and vertical versions.
Devices with a replaceable membrane have a longer service life, since the most vulnerable element of the system can be replaced and water does not come into contact with the metal body of the device
Device with a stationary diaphragm
In such devices inner part The tank is divided into two parts by a rigidly fixed membrane. It cannot be replaced, therefore, if it fails, the equipment will have to be replaced. One part of the device contains air, the other contains water, which is in direct contact with the internal metal surface device, which can provoke rapid corrosion. To prevent metal destruction and water pollution inner surface The water part of the tank is coated with special paint. However, such protection is not always durable. Devices are available in horizontal and vertical types.
A type of device with a rigidly fixed membrane. The design assumes that water is in contact with the walls of the equipment
In our next material Expert recommendations on choosing a membrane tank are presented:
How to choose the right device?
The main characteristic on the basis of which equipment is selected is its volume. In this case, the following factors must be taken into account:
- Number of people using the water supply system.
- The number of water intake points, which include not only showers and taps, but also Appliances, for example, washing machine and dishwasher.
- The likelihood that water will be consumed by several consumers at the same time.
- Limit number of start-stop cycles in one hour for installed pumping equipment.
- If the number of consumers does not exceed three people, and installed pump has a capacity of up to 2 cubic meters. m per hour, a tank with a volume of 20 to 24 liters is selected.
- If the number of consumers is from four to eight people and the pump capacity is within 3.5 cubic meters. m per hour, a tank with a volume of 50 liters is installed.
- If the number of consumers is more than ten people and the productivity of the pumping equipment is 5 cubic meters. m per hour, choose an expansion tank of 100 liters.
When selecting the desired model device, it is worth considering that the smaller the volume of the tank, the more often the pump will turn on. And also the fact that the smaller the volume, the greater the likelihood of pressure surges in the system. In addition, the equipment is also a reservoir for storing a certain supply of water. Based on this, the volume of the expansion tank is adjusted. You should know that the design of the device allows the installation of an additional tank. Moreover, this can be done during the operation of the main equipment without labor-intensive dismantling works. After installing the new device, the volume of the tank will be determined by the total volume of the containers installed in the system.
Except technical characteristics When choosing an expansion tank, special attention should be paid to its manufacturer. The pursuit of cheapness can result in much more significant expenses. Most often, to produce models that are attractive for their cost, the cheapest materials are used, and, as practice shows, they are not always of high quality. The quality of the rubber from which the membrane is made is especially important. Not only the service life of the tank, but also the safety of the water that comes from it directly depends on this.
When purchasing a tank with a replaceable membrane, be sure to check the cost of the consumable element. Very often, in the pursuit of profit, not always conscientious manufacturers significantly increase the price replaceable membrane. In this case, it will be more appropriate to choose a model from another company. Most often, a large manufacturer is ready to be responsible for the quality of its products because it values its reputation. Thus, it is worth considering the models of these brands first. These are Gilex and Elbi (Russia) and Reflex, Zilmet, Aquasystem (Germany).
The volume of the expansion tank for water supply may vary; it is selected based on the needs of the users. If a larger volume is subsequently required, an additional device can be installed
Features of self-installation
All expansion tanks can be divided into two groups, determined by the connection method. There are vertical and horizontal models. There are no special differences between them. When choosing, they are guided by the parameters of the room where the equipment will be placed. During the installation process, you should adhere to the following recommendations:
- The expansion tank is installed in such a way that it can be easily accessed for maintenance.
- It is necessary to provide for possible subsequent dismantling connecting pipeline to replace or repair equipment.
- The diameter of the connected water supply cannot be less than the diameter of the pipe.
- The device must be grounded to avoid electrolytic corrosion.
The device is installed on the suction side of the pump. On the segment between pumping equipment and the connection point, it is necessary to exclude all elements that can introduce significant hydraulic resistance into the system. We connect the make-up line to the circulation circuit of the entire system.
According to the type of installation, expansion tanks of horizontal and vertical connection are distinguished
Please also pay attention to the material about what malfunctions most often occur in pumping stations, and how to fix them yourself:
The expansion tank is an integral part autonomous system water supply It supports, prevents premature damage to the pump and retains a certain supply of water. However, all these functions are performed only if the structure is correctly selected and installed correctly. Therefore, if you lack experience, it is better not to get carried away with amateur activities, but to find qualified specialists who will install any device with high quality.
A well-installed and adjusted heating system will work reliably with rational consumption of energy resources. One of the main components on which the flawless operation of the boiler and circuit depends is the expansion tank.
The tank parameters are calculated taking into account the boiler power and coolant volume. The difference between the modifications is the size of the pipes and the maximum pressure.
Watch a video about the features of the expansion tank
The main function of the design is to extinguish high blood pressure liquids in the system. If the system is not equipped with such a device, a water hammer may occur, as a result of which pipes will rupture or heating equipment will be destroyed.Externally, the tank is a metal casing with filling inside and a pipe going out for connection to the heating system.
Heating expansion tank device
The expansion tank device consists of the following elements:
Safety valve;
Membranes;
Safety valve;
Water chambers;
Gas chamber;
Pipe.
Depending on the type, the design configuration may vary.
An autonomous heating system must have an expansion tank for heating, or a compensator. Its function is to compensate for the excess pressure that occurs in the system when the coolant expands due to heating. With a rapid increase in temperature, the coolant liquid expands and a pressure surge occurs, the so-called water hammer. It can destroy pipeline elements and connecting fittings. Other names for expansion devices: hydraulic accumulator, expansomat.
Design and principle of operation of expansion tanks for heating
Heating systems can be open or closed. Accordingly, heating expansion tanks exist open type and closed.
Open type tanks
An open expansion tank for heating is a parallelepiped-shaped container made of stainless steel. Such a tank is placed at the highest point of the open heating system, usually in the attic.
Pipes connected to the tank:
- mainline;
- circulation;
- alarm, with locking device.
In this type of heating system, the coolant (water) circulates naturally, without pumps. Despite the comparative cheapness and simplicity of such heating, it is gradually becoming a thing of the past due to numerous shortcomings.
- In an open tank, the coolant constantly evaporates, so you need to monitor the water level and add it as necessary. For the same reason, it is problematic to use another coolant, such as antifreeze - it evaporates even faster.
- It is possible for water to overflow from the tank, so it is necessary to provide for its drainage into the sewer or drainage system.
- An open expansion tank requires good thermal insulation so that the water does not freeze in severe frosts.
- Installation in the attic will require additional pipes and fittings.
- Air entering the system from the expansion device provokes corrosion of the pipeline and radiators, and also leads to the appearance of air locks.
The open compensator system is suitable for heating small one-story houses. Larger houses are heated with closed systems.
Closed tanks
A closed or membrane expansion tank of a heating system contains an elastic membrane inside that divides internal volume compensator tank into two compartments, gas and liquid. The gas part contains air under pressure (in some models - nitrogen or inert gas), and the liquid part receives excess coolant when heated.
Tank closed type(membrane)
The higher the temperature, the more the liquid part of the accumulator is filled. At the same time, the gas part contracts and the pressure in it increases. When the threshold value is reached, it triggers safety valve, excess pressure is released. And when the heating system cools down, the reverse process occurs and the coolant returns from the tank to the pipeline.
Operating principle of a membrane expansion tank
There are two types of membrane compensators.
- With a diaphragm type membrane. These are small sized tanks. The diaphragm membrane in them is non-removable and cannot be replaced: if it breaks, you will have to completely replace the device.
- With a balloon (pear-shaped) membrane. It can be changed when worn out; it is used in large thousand-liter tanks.
The volume of expansion tanks for heating can vary widely from two to several thousand liters. The shape of the closed hydraulic accumulator is flat or cylindrical. In a flat expansion tank, the membrane-diaphragm is located vertically, in a cylindrical tank it is horizontal.
It is worth paying attention: a membrane compensator is sometimes mistakenly called a vacuum expansion tank for heating. However, this device does not use a vacuum. The heating system may have a vacuum deaerator to remove air microbubbles from the water.
Installing a membrane expansion tank
Unlike open membrane accumulator For ease of maintenance, you can install it directly in the heating point, next to the boiler. Usually it is placed in a straight section in front of the circulation pump, preferably so that water (or other coolant) enters the compensator from above. It must be equipped with a pressure gauge, a safety valve and connected to the return line.
Hydraulic accumulators with a volume of up to 30 liters are mounted on the wall, larger ones are installed on the floor. When mounting on a wall, the tank should be securely fastened, since its weight increases sharply when filled with water.
Several membrane tanks in a heating point
Important performance characteristics and compensator volume calculation
When selecting an expansion tank, take into account the maximum operating temperature and pressure. For example, the coolant can heat up to +120° C, and the peak pressure in the heating expansion tank can reach 6-10 bar (the usual average value is 2-4 bar). Therefore, the characteristics of the membrane, its durability, heat resistance, compliance sanitary standards.
The volume of the compensator depends on the volume of coolant as a whole in the system. It is not necessary to calculate the volume mathematically accurately; a simplified method is often used: select a tank with a capacity equal to 10% of the total volume of the coolant. And if this volume is unknown, then they proceed from the power of the boiler and the type of heating devices. The ratios are as follows: for heating radiators they take – 11 l/kW, for heated floors – 17.5 l/kW, for wall-floor heaters – 7.5 l/kW.
If the capacity of the selected compensator is insufficient, the safety valve will release pressure too often. In this case, it is enough to purchase and connect in parallel another expansion tank.
It is quite difficult to take into account all the nuances, especially since in each house the heating system necessarily has its own characteristics. In order not to make a mistake when choosing and installing a device, it is better to contact a specialized company.
Video: installation of an expansion tank
When planning to create a water heating system in own home, the owner is faced with a choice of several options. The list of the most important questions includes the type of system (will it be open or closed), and what principle will be used to transfer coolant through pipes ( natural circulation due to action gravitational forces, or forced, requiring the installation of a special pump).
Each of the schemes has its own advantages and disadvantages. However, nowadays preference is increasingly given to closed system with forced circulation. This scheme is more compact, easier and faster to install, and has a number of other operational advantages. One of the main distinctive features is a completely sealed expansion tank for closed-type heating, the installation of which will be discussed in this publication.
But before purchasing an expansion tank and proceeding with its installation, you need to at least become familiar with its structure, operating principle, as well as which model will be optimal for a particular heating system.
IN What are the advantages of a closed heating system
Although V Lately many appeared modern devices and space heating systems, the principle of heat transfer through a liquid with high heat capacity circulating through pipes - without a doubt remains the most widespread. Water is most often used as a carrier of thermal energy, although in some circumstances it is necessary to use other liquids with a low freezing point (antifreeze).
The coolant receives heat from the boiler (ovens with water circuit) and transfers heat heating devices(radiators, convectors, “warm floor” circuits) installed in the premises in the required quantity.
How to decide on the type and number of heating radiators?
Even the most powerful boiler will not be able to create indoor comfortable atmosphere, if the parameters of heat exchange points do not correspond to the conditions of a particular room. How to do it right - in a special publication on our portal.
But any liquid has common physical properties. Firstly, when heated, it increases significantly in volume. And secondly, unlike gases, this is an incompressible substance; its thermal expansion must be compensated in some way by providing free volume for this. And at the same time, it is necessary to ensure that as it cools and decreases in volume, air does not enter the pipe contours from the outside, which will create a “plug” that prevents the normal circulation of the coolant.
These are the functions that the expansion tank performs.
Not yet in private construction, there was no particular alternative - an open expansion tank was installed at the highest point of the system, which completely coped with the tasks.
1 – heating boiler;
2 – supply riser;
3 – open expansion tank;
4 – heating radiator;
5 – optional – circulation pump. In this case, a pumping unit with a bypass loop and a valve system is shown. If desired or if the need arises, you can switch forced circulation to natural circulation, and vice versa.
You may be interested in information on how to properly carry out
Prices for circulation pumps
circulation pumps
A closed system is completely isolated from the atmosphere. A certain pressure is maintained in it, and the thermal expansion of the liquid is compensated by installing a sealed tank of a special design.
The tank in the diagram is shown pos. 6, embedded in the return pipe (item 7).
It would seem - why “fence the garden”? A regular open expansion tank, if it fully copes with its functions, seems to be a simpler and less expensive solution. It probably doesn’t cost much, and besides, with certain skills, it’s easy to make and weld it yourself from steel sheets, use unnecessary metal container, for example, an old can, etc. Moreover, you can meet examples applications old plastic cans.
Does it make sense to spend money on purchasing a sealed expansion tank? It turns out that there is, since a closed heating system has many advantages:
- Complete tightness absolutely eliminates the process of evaporation of the coolant. This opens up the possibility of using, in addition to water, special antifreezes. The measure is more than necessary if country house V winter time They do not use it all the time, but only occasionally, occasionally.
- IN open system heating expansion tank, as already mentioned, must be mounted at the highest point. Very often, an unheated attic becomes such a place. And this entails additional efforts to thermally insulate the container so that even in the most severe frosts the coolant in it does not freeze.
And in a closed system, the expansion tank can be installed in almost any area. The most appropriate installation location is the return pipe directly in front of the boiler entrance - here the tank parts will be less exposed to temperature effects from the heated coolant. But this is by no means a dogma, and it can be mounted in such a way that it does not create interference and does not disharmonize its appearance with the interior of the room, if, say, the system uses a wall-mounted boiler installed in the hallway or in the kitchen.
- In an open expansion tank, the coolant is always in contact with the atmosphere. This leads to constant saturation of the liquid with dissolved air, which causes increased corrosion in the circuit pipes and radiators, and increased gas formation during the heating process. Aluminum radiators are especially intolerant of this.
- A closed heating system with forced circulation is less inert - it warms up much faster when starting up, and is much more sensitive to adjustments. Completely unjustified losses in the area of the open type expansion tank are eliminated.
- The temperature difference in the supply pipe and in the return pipe in the connection currents with the boiler is less than in an open system. This is important for the safety and longevity of heating equipment.
- Closed circuit with forced circulations to create contours, it will require tons of pipes of smaller diameter - there is a benefit both in the cost of materials and in simplifying installation work.
- An open type expansion tank requires control to prevent overflow when filling, and to prevent the liquid level in it from falling below a critical level during operation. Of course, all this can be solved by installing additional devices, for example, float valves, overflow pipes, etc., but these are unnecessary complications. In a closed heating system, such problems do not arise.
- And finally, such a system is the most universal, as it is suitable for any type of battery, allows you to connect underfloor heating circuits, convectors, thermal curtains. In addition, if desired, you can organize hot heat supply by installing an indirect heating boiler into the system.
Of the serious shortcomings, only one can be mentioned. This — mandatory “safety group”, including control and measuring instruments (pressure gauge, thermometer), safety valve and automatic air vent. However, this is more likely no no wealth, and the technological cost that ensures safe operation heating systems.
In a word, the advantages of a closed system clearly outweigh, and spending on a special sealed expansion tank looks completely justified.
How does an expansion tank for closed heating work and how does it work?
The design of an expansion tank for a closed type system is not very complicated:
Usually the entire structure is housed in a stamped steel body (item 1) cylindrical(there are tanks in the form of a “tablet”). For production, high-quality metal with an anti-corrosion coating is used. The outside of the tank is covered with enamel. Products with a red body are used for heating. (There are tanks of blue color– but these are water accumulators for the water supply system. They are not designed for elevated temperatures, and all their parts are subject to increased sanitary and hygienic requirements).
On one side of the tank there is a threaded pipe (item 2) for insertion into the heating system. Sometimes fittings are included in the package to facilitate installation work.
WITH opposite side there is a nipple valve (item 3), which serves to pre-create the required pressure in the air chamber.
Inside, the entire cavity of the tank is divided by a membrane (item 6) into two chambers. On the side of the pipe there is a chamber for coolant (item 4), on the opposite side there is an air chamber (item 5)
The membrane is made of elastic material with a low diffusion rate. It is given a special shape, which ensures “orderly” deformation when the pressure in the chambers changes.
The principle of operation is simple.
- In the initial position, when the tank is connected to the system and filled with coolant, a certain volume of liquid enters the water chamber through the pipe. The pressure in the chambers is equalized, and this closed system acquires a static position.
- As the temperature rises, the volume of coolant in the heating system expands, accompanied by an increase in pressure. Excess fluid enters the expansion tank (red arrow), and its pressure bends the membrane (yellow arrow). In this case, the volume of the coolant chamber increases, and the air chamber correspondingly decreases, and the air pressure in it increases.
- As the temperature decreases and the total volume of the coolant decreases, excess pressure in the air chamber causes the membrane to move backward (green arrow), and the coolant moves back into the pipes of the heating system (blue arrow).
If the pressure in the heating system reaches a critical threshold, then the valve in the “safety group” should operate, which will release excess liquid. Some expansion tank models have their own safety valve.
Different tank models may have own characteristics designs. So, they can be non-separable or with the ability to replace the membrane (a special flange is provided for this). The kit may include brackets or clamps for mounting the tank on the wall, or it can be provided with stands - legs for placing it on the floor.
In addition, they may differ in the design of the membrane itself.
On the left is an expansion tank with a membrane diaphragm (it has already been discussed above). As a rule, these are non-separable models. A balloon-type membrane (picture on the right), made of elastic material, is often used. In fact, it itself is a water chamber. As pressure increases, such a membrane stretches, increasing in volume. It is these tanks that are equipped with a collapsible flange, which allows you to independently replace the membrane in the event of its failure. But the basic principle This doesn't change the work at all.
Video: installation of Flexcon brand expansion tanks FLAMCO»
Prices for Flexcon expansion tanks FLAMCO
Flexcon expansion tanks
How to calculate the required parameters of the expansion tank?
When choosing an expansion tank for a specific heating system, the fundamental point should be its working volume.
Calculation using formulas
You can find recommendations to install a tank, the volume of which is approximately 10% of the total volume of coolant circulating through the system circuits. However, a more accurate calculation can be made - there is a special formula for this:
Vb =Vwith ×k / D
The symbols in the formula indicate:
Vb– required working volume of the expansion tank;
Vс– the total volume of coolant in the heating system;
k– coefficient taking into account the volumetric expansion of the coolant during heating;
D– efficiency coefficient of the expansion tank.
Where to get the initial values? Let's look at it one by one:
- Total system volume ( VWith) can be determined in several ways:
- You can use a water meter to determine how much total volume will fit when filling the system with water.
- The most accurate method used when calculating a heating system is the summation of the total volume of pipes of all circuits, the capacity of the heat exchanger of the existing boiler (it is indicated in the passport data), and the volume of all heat exchange devices in the premises - radiators, convectors, etc.
- The simplest method gives a completely acceptable error. It is based on the fact that to provide 1 kW of heating power, 15 liters of coolant are required. Thus, the rated power of the boiler is simply multiplied by 15.
2. The value of the coefficient of thermal expansion ( k) is a tabular value. It varies nonlinearly depending on the heating temperature of the liquid and the percentage of antifreeze in it ethylene glycol additives The values are shown in the table below. The heating value line is taken from the calculation of the planned operating temperature of the heating system. For water, the percentage value of ethylene glycol is taken as 0. For antifreeze - based on the specific concentration.
| Coolant heating temperature, °C | Glycol content, % of total volume | |||||||
|---|---|---|---|---|---|---|---|---|
| 0 | 10 | 20 | 30 | 40 | 50 | 70 | 90 | |
| 0 | 0.00013 | 0.0032 | 0.0064 | 0.0096 | 0.0128 | 0.016 | 0.0224 | 0.0288 |
| 10 | 0.00027 | 0.0034 | 0.0066 | 0.0098 | 0.013 | 0.0162 | 0.0226 | 0.029 |
| 20 | 0.00177 | 0.0048 | 0.008 | 0.0112 | 0.0144 | 0.0176 | 0.024 | 0.0304 |
| 30 | 0.00435 | 0.0074 | 0.0106 | 0.0138 | 0.017 | 0.0202 | 0.0266 | 0.033 |
| 40 | 0.0078 | 0.0109 | 0.0141 | 0.0173 | 0.0205 | 0.0237 | 0.0301 | 0.0365 |
| 50 | 0.0121 | 0.0151 | 0.0183 | 0.0215 | 0.0247 | 0.0279 | 0.0343 | 0.0407 |
| 60 | 0.0171 | 0.0201 | 0.0232 | 0.0263 | 0.0294 | 0.0325 | 0.0387 | 0.0449 |
| 70 | 0.0227 | 0.0258 | 0.0288 | 0.0318 | 0.0348 | 0.0378 | 0.0438 | 0.0498 |
| 80 | 0.029 | 0.032 | 0.0349 | 0.0378 | 0.0407 | 0.0436 | 0.0494 | 0.0552 |
| 90 | 0.0359 | 0.0389 | 0.0417 | 0.0445 | 0.0473 | 0.0501 | 0.0557 | 0.0613 |
| 100 | 0.0434 | 0.0465 | 0.0491 | 0.0517 | 0.0543 | 0.0569 | 0.0621 | 0.0729 |
3. Expansion tank efficiency coefficient value ( D) will have to be calculated using a separate formula:
D = (Qm – Qb)/(Qm + 1 )
Qm— maximum permissible pressure in the heating system. It will be determined by the response threshold of the safety valve in the “safety group”, which must be indicated in the product passport.
Qb— pre-pumping pressure of the air chamber of the expansion tank. It may also be indicated on the packaging and in the product documentation. It is possible to change it - paging using car pump or, conversely, bleeding through the nipple. It is usually recommended to set this pressure within 1.0 – 1.5 atmospheres.
Calculator for calculating the required volume of the expansion tank
To simplify the calculation procedure for the reader, the article contains a special calculator in which the indicated dependencies are included. Enter the requested values, and after pressing the “CALCULATE” button you will receive the required volume of the expansion tank.
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 housing of the membrane expansion tank of the heating system is divided into two parts by an elastic membrane. In one of them there is a liquid substance, in the second there is a gas. The first part contains coolant, and the second is filled with air under high pressure or nitrogen.
Diaphragm expansion tank for heating system
Where are membrane expansion tanks 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 using 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 variable temperature of the working environment.
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 use in drinking water supplies;
- 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 drinking water contamination;
- There is no loss of coolant due to evaporation;
- Minimal air pumping is required;
- Installing such a tank is economical and relatively quick;
- Operating costs are low.
Peculiarities
For a membrane expansion tank of a heating system, the instructions will show the purpose of the tank: at all stages of operation, it must regulate the balance of pressure in the cavities and compensate for excessive pressure or even pressure drops in the heating system. So, membrane tank prevents increased loads in the heating system circuit, and, accordingly, emergency situations with faults.
A membrane tank for heating can have a replaceable or non-replaceable membrane. The main feature of the first type is that the heat carrier is completely contained in the flexible membrane container, thus not having the opportunity to interact with the inner steel surface. All installation and dismantling of the membrane is carried out through a flange that is bolted.
If in front of you is a tank with a fixed diaphragm, then it will have internal cavity, divided into two parts. The membrane in this case is diaphragm, non-replaceable and rigidly fixed.
Of course, the choice of a membrane tank for heating should be made exactly according to a certain system, it depends on the amount of coolant.
If your expansion tank does not have enough volume, this can lead to negative consequences– appearance of cracks, leakage hot water through the threads. Also, the pressure in the system may decrease below the minimum permissible, due to which air may get inside the tank. That is why the choice of tank should be based on its exact compliance with the maximum possible pressure parameters.
A membrane expansion tank for heating is used in a closed liquid circulation system in order to compensate for the thermal expansion of the coolant due to changes in the temperature of the liquid, maintain optimal pressure of the coolant and prevent water hammer. Water chamber and gas in constant mode have the same pressure, so the tightness of the system is not broken.
Water circulates without 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 will not require frost protection.
Heating expansion tank in the boiler room
The choice of tank is individual for each system, but in general there are several features to consider. The initial pressure in a device such as a membrane heating tank, which is connected to cold system, should be equal static pressure in the system plus 30-50 kPa. In addition, the tank must receive a reserve volume of coolant, 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 the maximum temperature of the coolant, the pressure does not exceed the maximum permissible value.
To protect the closed loop and tank system from overpressure, safety valves must be installed.
Installation of a membrane expansion tank
Diaphragm expansion tanks are initially supplied with an excess initial gas pressure, which fills absolutely the entire volume. Before installing the expansion tank, it must be inflated to a pre-calculated pressure. A safety valve must be installed. It is also recommended to install a drainage device in front of the tank.
Instructions for installing the expansion tank should be included in technical documentation. And, at a maximum, the installation should be carried out by a specialist; at a minimum, it is best to consult with him on this important issue. When installing the tank, you need to consider several points:
- It is best if the tank is installed before the water supply branch. The room must be able to drain water and recharge the system. Since water freezing is unacceptable, the room temperature should 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, be sure to make sure that the calculations are correct!
The tank must be grounded to prevent electrolytic corrosion.
- At the entrance to the tank you need to put check valve, if it is not included in the pump design. At the outlet there is a device such as a pressure gauge to be able to control the pressure and an automatic valve for releasing air.
If there is no shut-off valves, then you need to place it at the installation location.
