Air pressure in the membrane tank. Expansion tanks of open type. What to look for when choosing a tank
Selection Tips
membrane tank It is made in the form of a vessel with two chambers, air is pumped into one of which, and water enters the other. Expansion membrane tanks are used in heating systems to remove additional volume of water when the boiler is heated and the liquid expands and to prevent water hammer. In water supply systems membrane tanks serve to accumulate a certain amount of water in order to supply it under a certain pressure at the right time.
The inactive water supply system in the distribution pipes holds the plate emergency valve in the closed position. When water spills from one or more sprinklers, the pressure in the pipeline decreases. Consequently, the water supply pressure becomes dominant and determines the automatic opening of the plate as needed to supply the nozzles.
When fluid passes, the valve signals the opening of the sprinklers by operating the hydraulic bell. In addition, the expansion vessel avoids false alarms due to slow changes in supply water pressure. A wet sprinkler system can be fed by either a water pumping system or a water supply network.
Calculation of the minimum volume of the membrane tank
As a first approximation, the volume of the expansion membrane tank should be equal to 10% of the volume of water in the system.
To calculate the minimum allowable volume membrane tank, you need to know the maximum allowable number of pump starts per hour, the intensity of water intake and at what pressure values the pump will turn off and on.
A dry sprinkler system has a similar function as described above. It is defined as dry because the distribution pipes use compressed air instead of water. When the sprinkler opens, the change in pressure, as in the previous case, allows the relief valve plate to open. Water invades the pipes and exits the nozzles. These systems are equipped with air compressors and electrical systems control and management.
The use of these systems allows installation where there is a danger of freezing. Various types of components and ease of intervention make sprinkler systems suitable for various applications in the plant. They are tools that allow you to install a drainage system at the point where the fire started. In the event of a fire, the rise in temperature causes the lamp to break, allowing the water to fail.
Approximate formula for calculating the minimum volume membrane tank looks like that:
V = 2Q/N, where V is the volume of the membrane tank in cubic meters, Q - estimated water intake in cubic meters per hour, N - the maximum allowable number of pump on / off 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 allowable, calculated according to the above formula. One system can have two or more membrane tank, but at the same time it is necessary to ensure that the pressure in the air chambers is the same.
Depending on the type of installation you can use. The sprinkler is vertical. Sprinkler suspension. Spinal lateral wall. The particular efficiency of this type of installation, which has dry pipes when inactive, is that, unlike a sprinkler, it delivers the extinguisher from all nozzles at the same time and therefore through the protected zone, regardless of where the fire originated. Therefore, it combines the effectiveness of a localized action with the action of suppressing fire throughout the protected area.
The breeding system consists of a network of pipes, on which special nozzles are provided that deliver the extinguishing liquid. The number, position and size of these nozzles depend on the project data and the risk of the zone. The power line network is connected to a special valve called the discharge valve.
Before installation membrane tank it is necessary to make sure that the parameters were chosen correctly during the technical calculation. Cannot be installed membrane tank with unverified parameters, because this can cause damage to people, the system and the tank itself. membrane tank weighing more than 30 kg is fixed using a special device.
This is controlled by the detection system, which can be of different types. When the valve is activated, a special sealing plate opens, allowing water to flow into the pipes. At the same time, through a special valve opening, the distributed water activates the hydraulic bell to signal the fire alarm.
Another feature is the fire detection and valve insertion system, which is automatic and manual. The compressed air network is installed in a protected environment along which sprinklers are installed. Their intervention leads to a pressure drop in the detection system, which, with the help of a pneumatic actuator, allows the liquid to flow out using a special hydraulic system release of plates; then you activate the discharge valve. This activation can also be done by manual control or electrical control, which implements a solenoid valve.
Calculation of pre-pressure in a membrane tank
Manufacturers membrane tanks set the pre-pressure value to not more than 4 bar. However, it must be adjusted on site to suit the operating conditions. Adjusting the pre-pressure ensures the long life of the diaphragm and the reliable operation of the entire system.
It is understood that the detection system may consist of electrical type sensors connected to the solenoid control panel and the control panel. This type of detection replaces the pneumatic type described above. Various types of components and ease of operation make flood systems suitable for various plant applications.
This is a valve that allows you to control the flood system. The principle of operation is based on the pressure on the pneumatic drive heads. This pressure is controlled by a general, pneumatic or electrical detection network. When detected, there is a pressure change in pneumatic drive, which controls the opening of the diaphragm valve plate. The latter opens, allowing water to flow into the distribution network. Part of the water enters the hydraulic motor bell, allowing acoustic response to the fire alarm system.
The pre-pressure is measured with the tank empty. To accurately set it, use the correspondence table:
Calculation of the maximum and actual volume of the membrane tank
The maximum volume of water in membrane tank is ¾ of its volume, and the actual volume is very noticeably less. If the pressure difference before turning the pump on and off is about 2 bar, then the actual volume of water in membrane tank will be about 30% of the total volume. Actual Volume 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.
Sprinkler temperature sensor. They are tools for identifying fire in the place where it develops. In the event of a fire, the rise in temperature will cause the bulb to rupture, allowing air to escape from the pneumatic detection circuit. This change in pressure allows the control valve to open. These are devices that allow you to spray water and direct it after the discharge valve has been operated. Depending on the type of delivery. Jet cone nozzles.
Fractionated nozzles. The water outlet angle, depending on the need, is 45°, 60°, 90° and 120°. They are suitable for both vertical and horizontal jets. It is mounted in front of the discharge valve and allows the interception of water in the main water supply, both in the case of maintenance of the flood valve, and when restoring the system after a fire. It is manually controlled with a command flyer.
Remember the safety precautions: the pre-pressure must not exceed the level indicated on the label. membrane tank plate.
The organization of water supply in a private house has reached full automation. The minimum set of equipment and the competent use of the laws of physics - and suburban housing is no longer inferior in comfort to a city apartment. Even a conventional expansion tank for water supply has been improved in such a way as to minimize user involvement in the water supply process.
It is intended for acoustic signaling of the operation of the flood system. It is installed so that it can hear the horn in the buildings. Activation occurs by the passage of water, which supplies the hydraulic motor. The nozzle is a water powered off device and usually consists of a tube of suitable resistance with a proper boiling throat. The tube is wound on a special coil and will be constantly connected to a power source.
The fire protection network shall consist of noses having the following characteristics. The length of the pipe that can be achieved with a full jet at each point of the protected area of the hotel. Control valve and closure at the throat at the end of the pipe. The minimum diameter of the inner pipe is 19 mm.
A hydraulic tank (or a hydraulic accumulator, expansion tank) is a metal hermetic container that serves to maintain a stable pressure in the water supply system and create water supplies of different volumes.
At first glance, the choice and installation of this device should not cause difficulties - in any online store you can see many models that differ only slightly in shape and volume, but do not differ significantly in their functionality. But that's not the case at all. There are many nuances in the device of the expansion tank and the principle of its operation.
Throat pressure 1.5 bar. The nozzles can also be powered by a normal water supply, provided they can be supplied by a general user as well as a firefighter at the same time. Preferably, the crevices should be located close to access to the planes and in any case in an easily accessible position which protects the entire protected surface.
The fire hydrant network should consist of a network of metal pipes, preferably from a ring. Cases for cases for fire fighting. The container containing the fire must be placed in a visible spot. Each hose must consist of an approved length of pipe section so that it allows the full jet to reach every point in the protected area.
Externally, expansion tanks can only be divided into horizontal and vertical models, but their operating parameters can be very different.
Design features of hydraulic accumulators
Different models of expansion tanks may have restrictions on how they can be used - some are only designed to work with industrial water, others can be used for drinking water.
It must be made of frost-resistant steel pipes and should be independent of the health network. Flammability and pressure of fire gases. The power supply of the installation and the size of the plant itself must have such characteristics as ensuring the simultaneous operation of two firearms in the worst hydraulic position with a minimum clearance of "30".
Fire suppression systems with low, medium and high foam content
The plant must be permanently pressurized and provided with a firefighters connection application, which must be installed at a visible and easily accessible point on the buses for the connection itself. Foaming systems work with a logic of difference which they use to turn off the water soluble and blowing agent that expands on contact with air.
By design, accumulators are distinguished:
- tanks with a replaceable pear;
- tanks with a fixed membrane;
- hydraulic tanks without membrane.
On one side of the tank with a removable membrane (a tank with a bottom connection - at the bottom) there is a special threaded flange to which the pear is attached. On the reverse side there is a nipple for pumping or bleeding air, gas. It is designed to connect to a conventional car pump.
Foam, like water, is one of the most widely used fire extinguishers in industrial installations for liquid and solid fuel. The mass diffusion of this fire extinguishing agent is due to its relatively low cost, its availability, ease of use, the fact that it does not harm the human body, does not damage materials, and is easily removed from the area where it was used.
The foaming mixture is delivered using special foaming devices capable of creating a compact and extensive foam beam to cover the surface of the flaming zone. Thus, the main effect of foam suppression is the mechanical action of separating the fuel from the mixer; In addition, this property should also have a high cooling effect, which reduces the amount of vapor given off by the fuel, thereby lowering the temperature below that required for combustion.
In a tank with a replaceable pear, water is pumped into the membrane without touching the metal surface. The membrane is replaced by unscrewing the flange held by the bolts. In large containers, to stabilize the filling, the back wall of the membrane is additionally attached to the nipple.
Different types of foam are available on the market depending on the product you want to put out, the type of fire and the type of intervention you want to implement. Foam can be applied to both fixed and mobile systems; In any case, it is important to note that in order to obtain an adequate extinguishing effect, the foam must be brought to certain minimum flow rates, below which it is impossible to obtain extinguishing.
Foam release systems are classified according to the characteristics of the particulate foams and the coefficient of expansion, which basically indicates the number of foam liters that are produced from each liter of blowing agent before air is added.
The service life of the removable bulb depends on the air pressure settings in the accumulator gas compartment. Sometimes, in order to create a larger supply of water, the user reduces the amount of air and increases the amount of water in the bulb. 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 inner surface of such a tank is covered with moisture-resistant paint.
Foam systems are divided into. Low film fire extinguishing systems; Medium expansion extrusion foam systems; Fire extinguishers with high foam foam. While low expansion and medium expansion can be achieved by both fixed and mobile means, high expansion works by saturation, it only uses stationary foam generators.
This type of system is particularly suitable for the protection of the following environments. flammable liquids; hydrocarbon deposits; Alcohol deposits; Paints for paint; Production plants for flammable products; Rubber storage. Regardless of the type, foam systems consist of.
Most often, tanks with a fixed membrane are used for heating systems. Since the membrane is an element that fails much faster, the service life of such a tank is shorter than devices with a removable pear
There are also hydraulic tanks without a membrane. In them, compartments for water and air are not separated by anything. The principle of their operation is also based on the mutual pressure of water and air, but with such an open interaction, the mixing of two substances occurs. The advantage of such devices is the absence of a membrane or pear, which is a weak link in conventional accumulators.
Control system created using a pressure valve; Automatic control device based on fire detectors, which can also be manual; Dispensers in which foam is formed to ventilate the foam solution or, as in the case of dispensing in tanks, from pourers to which the foam has already been formed. The net remains empty behind the foam or foam inlet valve; Mixing system designed to create required mixture foamy water. In the mixing devices of the mixer, the preparation of the foaming mixture is usually carried out in three ways.
A feature of membraneless hydraulic tanks is that, since in such tanks water is constantly in contact with a metal surface, they are forced to be made of stainless steel. As a result, the tank has a high cost - 4 times the cost of a conventional tank, and stainless food steel is even more expensive - its price is 7 times more expensive.
The diffusion of water and air makes it necessary to service the tanks quite often. About once a season it is necessary to pump up air, which gradually mixes with water. A significant decrease in air volume, even at normal pressure in the tank, causes the pump to turn on frequently.
Hydraulic accumulators in water supply systems reduce the likelihood of water hammer, protect pumps from excessively frequent switching on, allow you to form a supply of water and maintain pressure in the circuit
The principle of operation of the hydraulic tank
Closed hydraulic tanks for water supply work according to the following scheme: the pump supplies water to the pear, gradually filling it, the membrane increases and the air is compressed, which is located between the pear and the metal case. The more water enters the pear, the more it puts pressure on the air, and he, in turn, tends to push it out of the container. As a result, the pressure in the tank increases, this leads to the shutdown of the pump.
For some time, when there is a flow of water in the system, compressed air maintains pressure. It pushes water into the plumbing. When its amount in the membrane decreases so much that the pressure drops to the lower limit, the relay is activated, turning the pump on again.
In the hydraulic 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 area of application
Do not confuse tanks for water supply and for heating system, therefore, when choosing, you need to find out their purpose. For clear identification, manufacturers paint accumulators for heating in red, for water supply - in Blue colour. But some do not adhere to such markings, therefore hallmark devices can use the following data:
- for water supply, the maximum temperature for using the accumulator will be up to 70 ° C, the allowable pressure can reach 10 bar;
- devices designed for the heating system can withstand temperatures up to +120 ° C, the operating pressure of the expansion tank is often not higher than 1.5 bar.
All the most important parameters are indicated on the decorative cap (nameplate) that closes the nipple.
A device designed for a heating system serves as an additional reservoir that allows you to remove excess coolant fluid, which expands when heated. Without it, the system is doomed to destruction.
The list of functions that the hydraulic tank performs in the cold water system (cold water supply) is much wider:
- Maintaining an even and constant pressure in the water supply. Due to the air pressure, the pressure is maintained for some time even when the pump is turned off, until it drops to the set minimum and the pump starts up again. Thus, the pressure in the system is maintained even with the simultaneous use of several plumbing fixtures.
- Protection against wear of pumping equipment. The water reserves contained in the tank allow you to use the water supply for some time without turning on the pump. This reduces the number of pump operations per unit of time and prolongs its operation.
- Water hammer protection. A sharp jump in pressure in the water supply when the pump is turned on can reach 10 or more atmospheres, which negatively affects all elements of the system. The diaphragm tank absorbs the shock, equalizing the pressure.
- Creation of water reserves. When the electricity is turned off, the water supply system will give off water for at least a short time, but, nevertheless, for some time.
For piping the water heater, expansion tanks are used that can withstand high temperatures.
Materials for the production of tanks
The expansion tank membrane is made of different materials, which during operation can withstand a different temperature range. In hydroaccumulators are used:
- Natural rubber rubber - NATURAL. The material may come into contact with drinking water, is used to accumulate cold water. Over time, it may begin to leak water. Withstands temperatures from -10 to 50 °C above zero.
- Synthetic butyl rubber - BUTYL. The most versatile, waterproof, used for water supply stations, suitable for drinking water. The operating temperature can vary 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.
- SBR rubber is used only for process water. The temperature of use is the same as that of previous brands.
To organize cold water supply, it is necessary to choose tanks with a pear made of food-grade rubber with improved elastic properties, which will better dampen hydraulic shocks and maintain a stable water pressure in the system.
The tank body is most often made of alloy steel, resistant to corrosion, coated on the outside with a paint and varnish coating. On sale you can also find stainless steel containers, very durable, but at the same time expensive.
How to choose and calculate the volume
Tanks with a capacity of 24 to 1000 liters are on sale. Which one to choose will be prompted by calculations, the result of which should be rounded up. When choosing a tank with a removable membrane, 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 supply will be approximately 30 liters.
The table shows the relationship between the parameters of air pressure in the gas compartment of the accumulator with the settings of the relay and the size of the tank (+)
A feature of small tanks is that they often do not have a valve to bleed air from a rubber bulb. This may create inconvenience during operation. Large tanks have such a valve, and in addition to creating a larger supply of water, they do a better job of maintaining a stable pressure in the system.
Calculation of the total volume of the hydraulic tank for water supply closed type calculated according to the following formula:
Vt=K*Amax*((1+Pmax)*(1+Pmin))/(Pmax-Pmin)*(1+Pair),
Vt is the total volume of the hydraulic 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 the equipment is turned off, bar;
P min - relay settings at equipment startup, bar;
P air - pressure in the hydraulic tank (in its gas cavity), bar.
Table of the coefficient K, depending on the power of the pump, for calculating the total volume of a closed-type hydraulic tank for water supply
Gileks, a company engaged in the production of an extensive line of equipment for water supply and heating systems, offers another formula for express determinations of the volume of a hydraulic tank
Horizontal or vertical type
The choice between a vertical and a horizontal tank lies in the features of the room. If the room is small or the volume of the container is impressive, then in order not to take up much space, a vertical container is installed.
The horizontal tank has a smaller capacity, can be hung on the wall, and also serve as a support for installation surface pump. For its installation, special fasteners are provided. Large tanks are produced only in a vertical version and are installed on legs.
Summing up all of the above, it can be noted that the choice of a hydraulic accumulator is to be made between such distinctive properties:
- operating pressure;
- producing country;
- larger or smaller volume;
- replaceable or not rubber membrane;
- membrane for technical or drinking water;
- body material - stainless or enameled steel.
In order to avoid difficulties in the future with the replacement of components, it is better to choose the most popular models of devices. Rubber pears for them are always on sale, if you need an urgent replacement, you won’t have to wait long for delivery.
Hydraulic tank connection diagrams
For a hot water supply system, the installation of an expansion tank is carried out in the section of the circulation line, the suction line of the pump, closer to the water heater. The tank is equipped with:
- pressure gauge, safety valve, air vent - safety group;
- shut-off valve with a device that prevents accidental shutdown.
In the plumbing system, where there is water heating equipment, the device takes on the functions of an expansion tank.
Scheme of installation in the HW system: 1 - hydraulic tank; 2- safety valve; 3 - pumping equipment; 4 – filtration element; 5 - check valve; 6 - shut-off valve (+)
In the cold water system, the main rule when installing a hydraulic accumulator is installation at the beginning of the piping, closer to the pump. The connection diagram must include:
- check and shutoff valve;
- security group.
Connection schemes can be very different. The connected hydraulic tank normalizes the operation of the equipment, reducing the number of pump starts per unit of time and thereby extending its service life.
Installation scheme in the cold water system with a well: 1 - tank; 2 - check valve; 3 - shut-off valve; 4 - relay for pressure control; 5 - control device for pumping equipment; 6 - security group
In a scheme with a booster pumping station, one of the pumps is constantly running. Such a system is installed for houses or buildings with high water consumption. The hydraulic tank here serves to neutralize pressure surges, and a container of the largest possible volume is installed to accumulate water.
How to install the device
Before starting work, check the accumulator for damage. The installation of the device is carried out in a soundproof room, at a positive temperature. In order to have access to a drain valve, shutoff valves, etc., the distance from the tank to the ceiling and walls is left at least 0.6 m.
In the room it is also necessary to provide for the possibility of filling the tank and draining the water. Fasteners and mounting space must be able to withstand 100% filling of the container.
For expansion tanks 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 static load, it is undesirable to allow the impact of pipes and assemblies on it. The tank is screwed to the floor using rubber pads. At the inlet to the hydraulic tank, a check valve and a drain valve are installed.
Before pouring 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 pressure of water.
Features of adjusting the accumulator
Expansion tanks for water supply are sold with the standard settings of the manufacturer - often the pressure in the air compartment is already set to 1.5 bar. The allowable pressure is always indicated on the label and the manufacturer does not recommend deviating from set parameters, especially in the direction of its increase.
Before proceeding with the adjustment, the system is disconnected from the mains and closed. shut-off valves. The membrane tank is completely emptied by draining the water - an accurate pressure indicator can only be measured with an empty water compartment.
Next, take pressure readings using an accurate pressure gauge. To do this, remove the decorative cap from the spool and bring the device. If the pressure differs from the required one, then it is adjusted by pumping or bleeding excess air.
Considering that the manufacturer is against deviations from the recommended pressure indicators, it is necessary to select suitable 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, such as dry nitrogen. This prevents corrosion of the inner surface. Therefore, users are also advised to use technical nitrogen to increase the pressure.
Setting 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, you can adjust the water pressure. The lower the gas pressure in the hydraulic tank (but not less than 1 bar), the more water it will contain.
At the same time, the pressure will become uneven - strong when the tank is full and weaker when it is empty. 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 supply is set using a relay. These values must be taken into account when setting the pressure in the expansion chamber.
Adjustment of the hydraulic tank in the piping of the water heater
The expansion tank, which is used for hot water supply, should not initially contain water. The pressure in the device is set at a value that is 0.2 more than the upper threshold for turning off the pump. For example, if the relay is configured to turn off the equipment at a pressure of 4 bar, then the pressure in the gas compartment of the expansion tank should 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, then there will always be water in the tank.
Hydraulic accumulator service rules
A scheduled inspection of the expansion tank is to check the pressure in the gas compartment. Valves should also be inspected. stop valves, air vent, check the operation of the pressure gauge. To verify the integrity of the tank, an external inspection is carried out.
During preventive maintenance, the pressure in the hydraulic tank should be measured and corrected if necessary.
Despite the simplicity of the device, expansion tanks for water supply are still not eternal and can break. Typical causes are diaphragm rupture or air loss 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 how a hydraulic accumulator works is the first step to proper maintenance and troubleshooting.
Characteristics and installation of an open hydraulic tank
Device open type is used less and less, as it requires constant user intervention in its work. An open expansion tank is a leaky container that serves to form pressure in the water supply system, accumulate water, and also serves as an expansion chamber.
The following is connected to the tank: a drain valve, branch pipes for the recirculation and supply pipes, control and overflow pipes
The tank is installed above the highest plumbing point, for example, in the attic, water enters the system by gravity. Each meter that the device rises increases the pressure in the water supply by 0.1 atmospheres. To automate the process of providing water, the tank is equipped with a float switch and an automatic relay is installed that will turn the pump on and off.
The container is mounted in a frost-free room, covered with a lid from dust and debris, wrap the walls with mineral wool or other insulation
This method of organizing water supply requires regular monitoring of the user, otherwise the water may freeze at low temperatures (if the room is not heated). The liquid will evaporate, so you will have to constantly add it.
In addition, such a container is bulky and not aesthetic; for it, it is imperative to have an attic space in the house. But the main drawback of the device is that the tank is not adapted to work in conditions of high water pressure in the system.
All about expansion tanks - classification, purpose, adjustment and signs of problems:
Wrong work pumping station often associated with malfunctions of the accumulator:
The nuances of choosing hydraulic tanks for water supply:
Even at the stage of planning and developing a water supply system, it is necessary to think through everything in principle important points and calculate all parameters. If there is no confidence in the infallibility of their calculations and right choice hydraulic tank for water supply, it is better to contact specialists. Many firms that sell professional equipment provide advice or even carry out calculations for free. This will help you avoid mistakes and unnecessary expenses.