Membrane tank for water supply - selection of the optimal model and installation example. Expansion tank for water supply: selection, installation, connection

Tips for choosing

Membrane tank  is made in the form of a vessel with two chambers, one of which is pumped with air, and the other receives water. Expansive membrane tanks  They are used in heating systems to drain additional water when heating the boiler and expanding the liquid and to prevent a hydraulic shock. In water supply systems membrane tanksserve to accumulate a certain amount of water for the purpose of supplying it under a certain pressure at the right time.

Calculation of the minimum volume of the membrane tank

In the first approximation, the volume of the expansion a membrane tank  should be equal to 10% of the water volume in the system.

To calculate the minimum allowable volume a membrane tank, you need to know the maximum allowable number of pump starts per hour, the intensity of the water set and at what pressure values ​​the pump will turn off and on.

An approximate formula for calculating the minimum volume a membrane tank  looks like that:
V = 2Q / N, where V denotes the volume of the membrane tank in cubic meters, Q is the expected water intake in cubic meters per hour, N is the maximum allowable number of pump starts / stops per hour.

If you want the pump motor to last as long as possible, you need to choose membrane tank , the volume of which slightly exceeds the minimum allowed, calculated by the above formula. In one system, you can install two or more membrane tanks, but you need to make sure that the pressure in the air chambers is the same.

Before installation a membrane tank  it is necessary to make sure that during the technical calculation the parameters were chosen correctly. Do not install membrane tank  with unchecked parameters, because it can damage people, the system and the tank itself. Membrane tank  mass of more than 30 kg is fixed with a special device.

Calculation of the pre-pressure in the membrane tank

Manufacturers membrane tanks  set the value of the preliminary pressure no more than 4 bar. However, it must be adjusted on site in accordance with the operating conditions. The pre-pressure setting provides long service  membrane and reliable operation of the entire system.

The pre-pressure is measured when the tank is emptied. To accurately expose it, use the matching table:

Calculation of the maximum and actual volume of the membrane tank

The maximum volume of water in a membrane tank  is ¾ of its volume, and the actual volume is much noticeably smaller. If the pressure drop before switching on and off the pump is about 2 bar, then the actual volume of water in the a membrane tank  will be about 30% of the total volume. Actual volume a membrane tank  directly depends on the difference between the pressures when the pump is turned on and off, the larger it is, the greater the actual volume.

Remember the safety precautions: the pre-pressure should not exceed the level indicated in the a membrane tank  nameplate.

• Description, types of construction
• Select a device
• Installation and connection

What is the purpose of a membrane tank for water supply? When organizing an autonomous water supply to a private house from wells or wells, it is necessary to create an emergency water supply. For these purposes, the expansion tank for water supply is perfectly suitable. These tanks are practical, have a large volume, but to ensure a normal operating mode, you need to apply a number of devices, rather than just one installation. When the tank is switched on the water supply system, the autonomy of the water supply significantly increases. The created stock will solve the problems with water supply, which can occur during pump breakdowns and during maintenance maintenance of equipment and wells. At the moment, the industry produces a huge number of different models, which significantly complicates the choice.

When the tank is switched on the water supply system, the autonomy of the water supply significantly increases.

Description, types of construction

Expansion tank  For water supply it is used to maintain the required pressure level for autonomous water supply. Most often for these purposes, membrane (expansion tanks) are used. These are the containers, inside which there are rubber membranes, which divide the tank into chambers. One camera is water and the other is air.

The tank is connected to the water supply of the autonomous water supply system so that the input branch feeds water into the tank, filling it, and only after filling a certain volume, water supplies to consumers.

The principle of operation is as follows: when the system is switched on (started), the pump pumps the water into the water chamber until it is filled. The volume of the second chamber is significantly reduced. When the air chamber is reduced, the air volume inside it does not change, so the pressure on the membrane increases. Accordingly, the pressure in the system increases.

The expansion tanks use a membrane that divides it into 2 tanks, one of which is with air and the other with liquid. In this case, it is necessary to have pressure monitoring equipment in the tank (pressure switch). This is necessary to automatically turn off the pump, the same sensor the pump automatically starts when the pressure in the tank falls below the programmed value. This will allow automatic operation  of the entire water supply system.

To monitor the pressure, you need to install a separate pressure gauge that will duplicate the pressure switch in case it breaks down. It is important to carefully and precisely adjust the pressure sensor, because the pressure in the water supply depends on its operation. Installation of expansion (membrane) reservoirs in the system of autonomous water supply solves several problems at once:

1. Maintenance of pressure in the system when the pump is disconnected and if it is stopped for maintenance or repair. In addition, such tanks can significantly reduce the power of the water supply pump.
2. Protection of the water supply system against hydraulic shocks, which can occur due to voltage drops in electrical networks, which significantly increases the survivability of the system.
3. Protects against pressure drops and other unpleasant nuances associated with the ingress of air into the system (for example, when the water level in the well falls).
4. In the event of an emergency shutdown, the pump will maintain some pressure in the system.
5. Reduces wear of pumping equipment, thereby prolonging the period of its operation. This is due to the fact that the pump pumps water only after lowering the water pressure in the tank, and not after lowering the water pressure in the system.
6. In the case of low water consumption, it is generally not possible to include pumping equipment, but only use water that is in the tank.

Membrane tanks are different designs. At the moment, there are only 2 types:

1. With replaceable diaphragm. Its main advantage is the ability to replace the membrane when it wears out or breaks. For replacement, a flange is provided, through which the old membrane is removed and a new one is laid. The flange is bolted to the tank body. If the reservoir has a large volume, additional attachments  membrane. Most often, the back of the membrane is attached to the nipple. Therefore, to remove, it is necessary to remove the nipple, otherwise the membrane can be torn.
2. The peculiarity of the functioning of such a device is the absence of water contact with the tank. Because water remains inside the membrane. This protects the metal case from rust, water does not get dirty when exposed to the surface. Thus, the life of such tanks is substantially extended. Devices with similar designs are available in vertical and horizontal versions. The main disadvantage is the increased wear of the membrane (which requires its frequent replacement) and the need to closely monitor the chemical composition of the membrane itself to prevent poisonous substances from entering the system (so you can not buy cheap Chinese or Polish membranes!).
3. Have a stationary diaphragm. They have a permanently fixed membrane (diaphragm), which divides the tank into 2 parts. The main difference is the impossibility of replacing the diaphragm in the event of its breakout or wear during operation. Similarly to the previous design, in one compartment there will be air, in the other - water. In this case, water has direct contact with the tank body. In the case of using metal as a body, it is possible for it to rust and clog the system with rust. Therefore, to protect against the appearance of rust, the inner surfaces of such tanks are painted with a special paint. It should be noted that over time, the paint is washed away, this leads to contact of the metal with water.

Tank closed type

The expansion tank is an auxiliary equipment, but without this device, it is not possible to operate the heating system efficiently. In order for the network to function properly, it is necessary to correctly select and configure the parameters of all its elements. One of the most important indicators in this case is the pressure in the expansion tank.

Why this design?

Before talking about the functions and tuning of the expansion tank, you need to understand the types and operation of this equipment. Why do we need such a design in the heating system? The main task of the device is to compensate for thermal expansion in the network. After all, during heating and cooling, the coolant changes its density and volume.

Note! If this device is not installed in the utility network, as the water warms up, the water will increase in volume and influence the walls of pipes and radiators. With a strong increase in water pressure, the system can simply break. Installing the expander allows you to save not only the pipeline, but also the boiler. After all, his work is initially calculated for a certain pressure of water in the system.

Expansion devices can vary in volume. When choosing a model that is suitable for a particular network in terms of technical parameters, it must be taken into account that the volume of this element must be at least 10% of the volume of the coolant circulating in the system. To perform this calculation, the volume in the radiators, pipes and boiler is summed. The easiest way to determine the volume is at the time of system injection. It should be remembered that a volume of 10% is a minimum, but it is better to take a model with a small margin.

About expansion tanks for wall-mounted gas boilers is worth mentioning separately. Most modern models with wall mounting have a built-in device mounted on the back or side wall and equipped with a nipple. With the help of a nipple, the pressure is inflated.

The device and the principle of operation

All kinds of expansion tanks have the same device. Inside the metal case there are two sealed compartments. On one side there is a nipple, and on the other - a neck for connection to the pipeline. Inside the case there is a diaphragm. In an empty container, it will occupy most of the volume, while the rest of the space is filled with air.

During the operation of the system, the coolant heats up, increases in volume, and its excess enters the cavity between the body and the diaphragm. When the water temperature in the system decreases, its volume decreases, and the injected air squeezes it back into the pipeline.

Installing the Expansion Element

Boiler equipment is designed to work at a certain head of water. This means that in the expansion tank for its normal operation, too, should be certain pressure. It is supported by air or nitrogen, which is filled with the body. The air is pumped into the tank at the factory. During installation, make sure that air is not released.  Otherwise the device will not be able to function.

The pressure is monitored using a manometer. The running arrow indicates that the air has come out of the expander. In general, this situation is not a serious problem, since air can be pumped through the nipple. The average pressure of water in the tank is 1.5 atm. However, they may not be suitable for a particular system. In this case, the pressure must be adjusted independently.

Normal indices are at 0.2 atm. less than in the system. Strictly do not exceed the pressure in the expansion tank in comparison with this indicator in the network. In such situations, the increased heat carrier can not enter the reservoir. The tank is connected to the pipeline through the connection size.

It is important not only to properly connect the expansion tank, but also to choose the right place for its installation. Despite the fact that modern models can be mounted anywhere, experts advise installing this element of the system on the return between the boiler and the pump.

To ensure maintainability of the structure, a ball valve is installed on the pipe through which the expander capacity is connected. In the event of equipment failure, the shut-off valve will remove it without pumping the coolant out of the system. During operation of the system, the crane must be open.  Otherwise, it will sharply increase pressure, and it will flow at its weakest point.

Installation in the boiler room

AT open systemsoh with natural circulation  coolant tanks are installed of other types. Such a tank is an open tank, usually welded from sheet steel. Install it at the highest point of the engineering network.

The principle of operation of such an element is very simple. As the volume increases, fluid is displaced from the pipes, rising along them along with the air. Cooling, the coolant returns to the pipeline under the influence of gravitational forces and natural air pressure.

Why does the pressure drop?

The pressure in the expansion vessel must be constant, but the situation when it falls during the operation of the system is not uncommon.

There are several reasons why pressure can decrease:

• Leakage of coolant. Most often, a similar problem occurs in systems where the coolant is not water, but antifreeze. Such liquids can penetrate into the smallest cracks, causing leakage. In this case, it is necessary to eliminate leaks and fill the tank with air.
• Pressure drop in the boiler. If the indicators are significantly reduced, you need to contact a specialist. If the pressure decreases slightly and is equalized after the start-up of the system, it can be operated, since such failures do not cause harm.

Pressure adjustment

The water pressure in the expansion element of the heating system is a configurable parameter. The setup is simple enough, and all the actions can be done independently.

To configure the necessary settings, you need the following:

Principle of connection

• Make the calculation and determine the required indicators - by 0.2 atm. less than in the system.
• Set these indicators before installing the tank into the system, dropping air or pumping it through the nipple.
• Connect the tank to the pipeline and fill the system with water. This should be done slowly, monitoring the pressure indicators in the pipes and the tank. To pump the coolant should be until the pressure indicators are not equal.
• After this, it is necessary to connect the pumping equipment and continue to pump the coolant. It is necessary to pump the water until the operational pressure calculated before the installation of the network is reached in the tank. This will ensure that there is a reserve volume of water in the body.
• The first activation of the system must be carried out in the maximum temperature mode. Under this condition, the volume of the heat carrier increases by the value of the specific increment. This ensures that a quantity of water equal to its capacity enters the tank. The pressure in the tank rises to the maximum.

Conclusion

The expansion tank is the most important additional element in any heating system. If for open systems with gravitational circulation it is sufficient to install a simple open reservoir at the top point, then for complex systems closed systems  The installation of industrial models is required.

These tanks are leakproof. In the production process, air is pumped into the body, maintaining the pressure necessary for the normal operation of the systems with forced circulation. You can adjust the required pressure indices yourself using a pressure gauge and a conventional automotive compressor.

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The organization of water supply in a private house has reached full automation. The minimum set of equipment and competent use of the laws of physics - and suburban housing is already in no way inferior in terms of the comfort of a city apartment. Even a conventional expansion tank for water supply is improved in such a way as to minimize the user's involvement in the water supply process.

The hydraulic tank (or hydraulic accumulator, expansion vessel) is a metal hermetic vessel that serves to maintain stable head  in the aqueduct and the creation of different in terms of water reserves.

At first glance, the choice and installation of this device should not cause difficulties - in any online store you can see a lot of models that only slightly differ in form and volume, but do not differ significantly in their functionality. But this is not so. In the device of the expansion tank and the principle of its operation, there are many nuances.

Externally, the expansion tanks can only be divided into horizontal and vertical models, but their operating parameters can be very different

Features of the design of accumulators

Different models of expansion tanks may have limitations on the way they are used - some are designed only for working with industrial water, others can be used for drinking water.

According to the design, hydraulic accumulators are distinguished:

• tanks with replaceable pear;
• containers with a fixed membrane;
• hydraulic tanks without a membrane.

On the one side of the tank with a removable diaphragm (the tank with the lower connection - at the bottom) has a special threaded flange, to which the pear is attached. FROM reverse side  there is a nipple, for pumping or bleeding air, gas. It is designed for connection to a normal car pump.

In the tank with a replaceable pear, the water is pumped into the membrane, not touching the metal surface. The membrane is replaced by unscrewing the flange that holds the bolts. In large containers, to stabilize the filling, the rear wall of the membrane is additionally attached to the nipple.

The service life of the removable pear depends on the settings of the air pressure in the gas compartment of the accumulator. Sometimes, to create a larger water supply, the user reduces the amount of air and increases the amount of water in the pear. This causes the membrane to touch the tank wall, and causes rapid abrasion

The internal space of the tank with a fixed membrane is divided by it into two compartments. One contains gas (air), the other receives water. The internal surface of such a tank is covered with a moisture resistant paint.

Most often, fixed membrane tanks are used for heating systems. Since the membrane is an element that breaks down much faster, then the life of such a tank is less than that of devices with a removable pear

There are also hydraulic tanks without a membrane. In them the compartments for water and air are not divided in any way. The principle of their action is also based on the mutual pressure of water and air, but with such an open interaction, mixing of two substances occurs. The advantage of such devices is the absence of a membrane or a pear, which is a weak link in the usual accumulators.

A feature of membrane-free tanks is that, as in such tanks, water is constantly in contact with the surface of the metal, they are forced to make them from stainless steel. As a result, the tank has a high cost - 4 times higher than the cost of a conventional tank, and stainless steel food, and even more - its price is 7 times more expensive

Diffusion of water and air makes servicing tanks often enough. About once a season you have to pump up air, which gradually mixes with water. A significant reduction in air volume, even at normal pressure in the tank, causes frequent pump starts.

Hydraulic accumulators in water supply systems reduce the likelihood of water hammering, protect the pumps from excessively frequent inclusions, allow to form a water reserve and maintain pressure in the circuit

The principle of the hydraulic tank

Closed water tanks for water supply work according to this scheme: the pump delivers water to the pear, gradually filling it, the membrane increases and air is compressed, which is between the pear and the metal casing. The more water enters the pear, the more it presses on the air, and the one, in turn, tends to push it out of the container. As a result, the pressure in the reservoir increases, this causes the pump to shut down.

Some time, when the system consumes water, compressed air maintains pressure. He pushes water into the water pipe. When its amount in the membrane decreases so much that the pressure drops to the lower limit, the relay trips, again turning on the pump.

In the tank there is a constant interaction of water and gas, separated from each other by a rubber membrane. The volume of liquid inside the device is regulated by the amount of gas (its pressure) (+)

Classification by field of application

Do not confuse the tanks for water supply and for the heating system, so when choosing you need to find out their purpose. For clear identification, manufacturers paint hydroaccumulators for heating in red, for water supply - in blue. But some do not adhere to this marking, so the distinguishing feature of the devices can serve as such data:

• for water supply, the maximum temperature of use of the accumulator will be up to 70 ° C, the permissible pressure can reach 10 bar;
• devices designed for the heating system can withstand temperatures up to +120 ° C, the working pressure of the expansion tank often does not exceed 1.5 bar.

All the most important parameters are indicated on the decorative cap (label), which closes the nipple.

The device intended for the heating system serves as an additional reservoir, which allows to remove the excess liquid of the coolant, which expands upon heating. Without it, the system is doomed to destruction

The list of functions that the tank performs in the HV (cold water supply) system is much broader:

• Maintenance of an equal and constant pressure in a waterpipe.  Due to the air pressure, the head is maintained for a while even when the pump is switched off, until it falls to the set minimum and the pump is not switched on again. Thus, the pressure in the system is maintained even with the simultaneous use of several plumbing fixtures.
• Protection against wear of pumping equipment.  Reserves of water contained in the tank, allows some time to use the water supply, not including the pump. This reduces the number of pump trips per unit of time and prolongs its operation.
• Protection against water hammering. A sharp pressure jump in the water pipe when the pump is switched on can reach 10 or more atmospheres, which negatively affects all elements of the system. The membrane tank takes the blow, leveling the pressure.
• Creation of water reserves.  When the electricity is cut off, the water supply system is at least for a short while, but, nevertheless, some more time will give away the water.

To strap the water heater use expansion tanks, which can withstand high temperatures.

Materials for the production of tanks

The expansion tank membrane is made of different materials that can withstand a different temperature range during operation. In hydroaccumulators apply:

• Natural rubber rubber - NATURAL. Material can be contacted with drinking water, is used for accumulation cold water. In time, it may start to flow through the water. Withstands temperatures from -10 to 50 ° C above zero.
• Synthetic Butyl Rubber - BUTYL. The most universal, waterproof, used for water supply stations, suitable for drinking water. The operating temperature can range from -10 to 100 ° C.
• Synthetic rubber from ethylene-propylene - EPDM. More permeable than the previous one, can contact with drinking water. The range of permissible temperatures is from -10 to 100 ° C.
• Rubber SBR is used only for technical water. The temperature of use is the same as that of previous brands.

For the organization of cold water supply, it is necessary to choose tanks with a pear made of food rubber with improved elastic properties that will better quench hydraulic shocks and maintain a stable head of water in the system.

The tank body is most often made of alloy steel, resistant to corrosion, covered with paint and varnish on the outside. On sale, you can also find stainless steel containers, very durable, but expensive.

How to choose and calculate the volume

The sale of tanks with a capacity of 24 to 1000 liters. Which one to choose, prompt calculations, the result of which should be rounded up. When choosing a tank with a removable diaphragm, it should be remembered that the volume of water occupies 30% of the total volume of the tank, that is, in a 100-liter tank, the water reserve will be approximately 30 liters.

The table shows the relationship between the air pressure parameters in the gas compartment of the accumulator with the relay settings and the tank size (+)

A feature of small tanks is that they often do not have a valve to bleed air from a rubber pear. This can create inconvenience during operation. Large tanks have such a valve, and in addition to creating a larger water supply, they are better able to maintain a stable head in the system.

Calculation of the total volume of the tank for water supply of a closed type is calculated according to the following formula:

Vt = K * Amax * ((1 + Pmax) * (1 + Pmin)) / (Pmax-Pmin) * (1 + Pst.),

Vt is the total volume of the tank;

Amax - the maximum possible consumption of water per minute, liter;

K - coefficient (see table), depending on the pump power;

P max - relay settings when equipment is disconnected, bar;

P min - relay settings when the equipment is started, bar;

P air. - pressure in the tank (in its gas cavity), bar.

Table of the coefficient K, depending on the pump power, for calculating the total volume of the closed type water tank for water supply

The company Gileks, engaged in the production of an extensive line of equipment for water supply and heating, offers one more formula for express determination of the volume of the tank

Horizontal or vertical type

The choice between a vertical and a horizontal tank is in the features of the room. If the room is small or the volume of capacity is impressive, then to not take up much space, set the vertical capacity.

The horizontal tank has a smaller capacity, can be hung on the wall, and also serves as a support for installation surface pump. For its installation, special fasteners are provided. Large tanks are manufactured only in vertical design and installed on the legs.

Summarizing all of the above, it can be noted that the choice of the accumulator is to be performed between such distinctive properties:

• operating pressure;
• manufacturer country;
• greater or lesser volume;
• replaceable or missing rubber membrane;
• membrane for technical or drinking water;
• the body material is stainless or enamelled steel.

That in the future there were no difficulties with replacement of accessories, it is better to choose the most running models of devices. Rubber pears are always available for free, if you need an urgent replacement, you will not have to wait long for delivery.

Schemes for connecting hydraulic tanks

For the hot water supply system, the expansion tank is installed on the section of the circulation line, the suction line of the pump, closer to the water heater. The tank is equipped with:

• manometer, safety valve, air vent - safety group;
• a shut-off valve with a device that prevents accidental overlapping.

In the water supply system, where the water heating equipment is present, the device takes over the functions of the expansion tank.

The installation scheme in the HW system: 1 - the tank; 2 - safety valve; 3 - pumping equipment; 4 - the element of filtration; 5 - check valve; 6 - shut-off valve (+)

In the HV system, the main rule when installing a hydraulic accumulator is the installation at the beginning of the strapping, closer to the pump. The connection scheme must contain:

• reverse and shut-off valve;
• security group.

Connection schemes can be very different. The connected hydraulic tank normalizes the operation of the equipment, reducing the number of pump inclusions per unit of time and thereby prolonging the service life of the pump.

Scheme of installation in the HV system with a well: 1 - a tank; 2 - the non-return valve; 3 - shut-off valve; 4 - the relay for pressure adjustment; 5 - control device for pumping equipment; 6 - security group

In the scheme with the pump station, one of the pumps works constantly. Such a system is installed for houses or buildings with high water consumption. The tank here serves to neutralize pressure surges, and to store water, the capacity of the largest volume is set.

How to install the device

Before starting work, check the accumulator for damage. Installation of the device is carried out in a soundproofed room, at plus temperature. To have access to the drain cock, shut-off valve, etc., the distance from the tank to the ceiling and walls is at least 0.6 m.

The room should also provide for the possibility of filling the tank and draining the water. Fasteners and mounting locations must be 100% full capacity.

For expansion tanks with a volume of up to 30 liters, a wall mount is used, large tanks are mounted on legs

The hydraulic accumulator should not be subjected to mechanical and statistical loading, it is undesirable to allow the impact of pipes and aggregates on it. The tank is screwed to the floor using rubber gaskets. At the entrance to the tank installed check valve, drain cock.

Before you pour water into the tank for the first time, it is advisable to remove air from the pear. In order not to damage the membrane, fill the tank slowly using a small head of water

Features of adjusting the accumulator

Expansion tanks for water supply go on sale with standard manufacturer settings - often the pressure in the air compartment is already set at 1.5 bar. The permissible pressure is always indicated on the label and the manufacturer does not recommend deviating from the set parameters, especially towards increasing it.

Before proceeding with the adjustment, the system is disconnected from the mains and the shut-off valves are closed. The membrane tank is completely emptied, draining the water - an accurate pressure reading can only be measured with an empty water compartment.

Further, the pressure readings are taken using an accurate pressure gauge. To do this, remove the decorative cap from the slide and bring the device. If the pressure differs from the required, it is brought into line by pumping or bleeding excess air.

Given that the manufacturer is against deviations from the recommended pressure indicators, it is necessary to select the right equipment at the design stage, the parameters of which will not conflict with each other

When adjusting the pressure in the gas compartment of the tank, the manufacturer fills it with an inert gas, for example, with dried nitrogen. This prevents corrosion of the inner surface. Therefore, users are also encouraged to use technical nitrogen to increase pressure.

Adjustment of the tank pressure in the water supply system

The pressure in the closed tank is always set slightly lower (by 10%) than the pressure level when the pump is started. By adjusting the pressure in the device, the water head can be adjusted. The smaller the gas pressure in the tank (but not less than 1 bar), the more it will contain water.

The pressure will become uneven at this - strong with a filled reservoir and weaker at its emptying. To ensure a strong and even flow of water, set the pressure in the chamber with air or gas within 1.5 bar.

The water pressure in the water pipe is set by means of a relay. When adjusting the pressure in the expansion chamber, these values ​​must be taken into account

Adjusting the tank in the water heater

The expansion tank, which is used for hot water supply, initially should not contain water. The pressure in the device is set at a value that is 0.2 more than the upper cut-off threshold of the pump. For example, if the relay is configured to shut off the equipment at a pressure reading of 4 bar, then the pressure in the gas chamber of the expansion tank must be set to 4.2 bar.

Installed in the piping of the water heater, the tank does not serve to maintain pressure. It is designed to compensate for the expansion when the water is heated. If you set the pressure in it to a lower value, the water will always be in the tank.

Maintenance rules for the hydraulic accumulator

Planned inspection of the expansion tank is to check the pressure in the gas compartment. It is also necessary to inspect the valves, stop valves, air vent, check the operation of the manometer. To verify the integrity of the tank, an external examination is carried out.

During preventive maintenance, the pressure in the tank should be measured and corrected if necessary

Despite all the simplicity of the device, the expansion tanks for water supply are still not eternal and can break down. Typical causes are rupture of the membrane or loss of air through the nipple. Signs of breakdowns can be determined by the frequent operation of the pump, the appearance of noise in the water supply system. Understanding the principle of the hydraulic accumulator is the first step to proper maintenance and troubleshooting.

Characteristics and installation of an open tank

Device open type  It is used less and less, as it requires constant user intervention in its work. An open expansion tank is an unpressurized tank that serves to create pressure in the water pipe, accumulates water, and also serves as an expansion chamber.

The tank is connected to: drain cock, pipes for recirculation and supply pipes, control and overflow pipe

The tank is installed above the highest sanitary point, for example, in the attic, the water enters the system by gravity. Each meter, which the device rises, increases the pressure in the water pipe by 0.1 atmospheres. To automate the water supply process, the tank is equipped with a float switch and an automatic relay is installed that will turn the pump on and off.

The capacity is mounted in a non-freezing room, covered with a lid from dust and debris, wrapped with mineral wool or other insulation

This way of organizing water supply requires regular monitoring of the user, otherwise water at freezing temperatures can freeze (if the room is not heated). The liquid will evaporate, so you have to constantly top up it.

In addition, this capacity is cumbersome and not aesthetic, for it is necessary to have an attic space in the house. But the main drawback of the device - the tank is not able to work in conditions of high water pressure in the system.

All about expansion tanks - classification, purpose, adjustment and signs of malfunctions:

Incorrect work pumping station  often associated with hydraulic accumulator faults:

Nuances of choosing hydraulic tanks for water supply:

Even at the stage of planning and development of the water supply system, it is necessary to think through all the fundamentally important points and calculate all the parameters. If there is no confidence in the infallibility of your calculations and the correct choice of the tank for water supply, it is better to turn to specialists. Many companies that are engaged in the implementation of professional equipment, provide advice or even conduct calculations for free. This will help to avoid mistakes and waste.

  Membrane tank  functions as follows: after installation of the system and connection to the mains, the pump turns on and starts pumping water into the water chamber; while the volume of air in the air chamber of the tank is reduced by the amount of incoming water in the tank. When the volume of air decreases, the pressure in a membrane tank  increases. After the pressure in the diaphragm tank exceeds the shutdown pressure of the pump preset at the pressure switch, the pump switches off and remains in the off state until the pressure in the system drops as a result of the draw-off (   The water is supplied directly to the consumer from the membrane tank), after which the pump is switched on again, etc.

Since the air pressure in the membrane tank is balanced by the water pressure, the membrane is constantly in a free state, not experiencing internal stresses - it "floats" in the tank between water and air. The pressure in a membrane tank  can be controlled by a manometer. On it also, the pressure switch is adjusted to the required operating range of the membrane tank.

  Where is the membrane tank used?

Use of membrane tanks in heating systems
When the boiler is heated, the temperature of the heat-transfer fluid in it rises and the liquid expands. The liquid is practically incompressible, and if the heating system is not equipped with an additional device that allows to divert an additional volume, then its destruction will inevitably occur. To exclude this, expansion tanks are used.

Use of membrane tanks in water supply and water treatment systems
Tanks for water (hydraulic accumulators) serve to accumulate a certain amount of water, so that it can be dispensed at the right pressure at the right time.

Other functions of the membrane tanks
Expansion tanks can be used to prevent the destruction of the system from a hydraulic shock. Also, tanks can be used both as containers with extinguishing liquid in fire extinguishing systems, and as backup tanks in cases where electricity is cut off. Hydraulic tanks are used not only in domestic, but also in industrial and agricultural water supply systems. In this case, the professional series is designed for operating pressure up to 16 bar.

  What are the designs of membrane tanks?

Tanks with replaceable diaphragm
There are horizontal and vertical executions. A distinctive feature - the liquid is entirely inside the membrane and does not contact the metal surface of the tank. The membrane is replaced by a flange, which is fixed with a few bolts. At large volumes of the expansion tank, the balloon type membrane is fixed by the rear end to the nipple through the threaded connection to stabilize the filling.

Fixed diaphragm tanks
The inner surface of the tank is divided into two volumes by a membrane. Membrane  - diaphragm, irremovable, rigidly fixed around the perimeter of the tank section. In one volume there is air, in the other - coolant or drinking water. The outer surface of the tank is covered with enamel, and the inner surface, which comes into contact with the liquid, is damp-proof.

  How to install a diaphragm tank correctly?

Before installing the tank, it must be ensured that the parameters are correctly determined in the technical calculation. It is strictly forbidden to install membrane tank, without checking the technical calculations and parameters, as this can cause damage to people, heating system  or the tank itself.
  The membrane tank should only be installed by a trained technician.  The membrane tank must be technically correctly installed and reliably connected to the pipeline and foundation. If the mass of the tank exceeds 30 kg, it is necessary to fix it with a special device to avoid damage.
On systems equipped with a diaphragm tank, safety devices must be installed that limit the pressure and ensure that the maximum operating pressure can not be exceeded.
To prevent electrolytic corrosion, the tank must be reliably grounded.

  Preliminary pressure in the membrane tank
At the factory, a pre-pressure of air (no more than 4 bar) is set in the membrane tank. The pre-pressure can be adjusted on site in accordance with the operating conditions. Correct setting of the pre-pressure ensures reliable operation of the entire system and long term  service membrane.
During the installation of the system, it is always recommended to check the pre-pressure in the diaphragm tank. Before changing the pre-pressure, the tank must be emptied. The pre-pressure should be lower than the pump start-up pressure. For correct installation of this pressure, we recommend using the setup table presented here.

  The maximum and actual volumes of the membrane tank
The maximum volume of water contained in the membrane tank can be no more than
  75% of its total volume. The actual volume of water contained in it, as a rule, is much less, because only in rare cases, provided by the specifics of a particular technological process, the pressure of a membrane tank  water reaches 10 bar. Therefore, if the pressure drop between on and off of the pump does not exceed 2 - 2.5 bar (the most acceptable range in an autonomous water supply range), the actual volume of water in the membrane tank will be approximately 30-35% of its total volume.
The greater the difference between pump on and off pressures, the greater the actual volume of the membrane tank.

  The minimum volume of the membrane tank
The minimum allowable volume of the membrane tank depends directly on the maximum allowable number of pump starts per hour and on the intensity of the draw-off, as well as on what pressure values ​​the pump will turn on and off.
  Minimum allowable volume a membrane tank  can be determined from the following approximate expression:
  V = 2Q / N,
  where V is the volume of the membrane tank, m3
  Q - prospective water analysis, m3 / h
  N - the maximum permissible number of pump inclusions per hour
In order to extend the service life of the pump motor, it is recommended to select a diaphragm tank, the volume of which is slightly higher than the minimum allowable. It is allowed to install two or more membrane tanks in one system, and the pressure in the air chambers of these membrane tanks must be the same.

  Maintenance of diaphragm tanks
It is necessary that the operation is carried out only by qualified specialists.
Membrane tanks should be serviced at least once a year, and the results of preliminary air injection should correspond to the value indicated on the label +20%.
When carrying out preliminary air injection, the tank must be completely drained.
If, during the pre-injection of air, the pressure differs from the pressure indicated on the label, it must be restored to its original level.
Do not disconnect the expansion tank until it is completely drained with a drain cock. The tank must be protected from strong cold.

  Safety precautions
Preliminary pressure should in no case exceed the level indicated on the information plate and fixed on each tank. Membrane tank  should never be disassembled or dismantled during operation. It is forbidden to ream the tank and open it by applying force. Always respect specificationsindicated on the information plate. Never exceed the maximum operating temperature and maximum operating pressure. Do not use the diaphragm tank for other purposes.
  Each membrane tank  tested, tested individually or jointly, packaged at the factory.