The diaphragm tank (accumulator) protects the autonomous water supply system from constant pressure drops. Its main tasks are:
- Maintaining constant pressure in the system
- Reducing the number of pump on / off cycles during intensive use, thereby increasing the resource of pumping equipment
- Protection against water hammer, which significantly reduces the service life of the borehole pump and all components of the water supply system.
The secondary functions of the hydroaccumulator (GA) include: water accumulation in the event of a power outage. I would like to draw your attention to the fact that the volume of water accumulated in the membrane tank will be 30-40% of its actual volume. For example, a 50 liter one holds 19 liters of water, provided that: the air pressure in the accumulator is 1.8 bar; pump activation pressure (minimum pressure in the water supply system) - 2.0 bar; pump cut-off pressure (maximum pressure in the water supply system) - 4.0 bar. Under the same conditions, a 100 liter Zilmet membrane tank holds 38 liters of water. Therefore, if you are pursuing the goal of accumulating water in case of a power outage, you will need to install an additional tank.
So, what is a hydraulic accumulator and what should be guided by when choosing it?
Diaphragm tanks are of two types: horizontal and vertical.
The principle of operation and design are practically the same. The only difference is the position of the membrane. As a rule, vertical accumulators are more convenient to place in a room, due to their design, they take up less useful space.
The figure shows the design of a vertical accumulator:
HA is a steel vessel with a membrane installed inside it, which is a working cavity. The membrane must be made of butyl or food grade rubber (EPDM)... The water supply to the accumulator is carried out using a threaded fitting mounted on the flange in the lower part of the GA. When buying a hydraulic accumulator, pay attention to the fact that the flange was made of stainless steel- this will help to avoid leaks during operation. Air is pumped into the cavity between the membrane and the HA body through the air nipple (it is located under the plastic cap in the upper or lower part of the accumulator). The air pressure in the HA should be 10% lower than the pump activation pressure. This condition is a compromise between the durability of the membrane (the membrane is a replaceable element) and the comfort of water use. Typically, manufacturing plants pump air at a pressure of 1.5 bar. You can increase the pressure in the GA using a conventional car pump.
How to choose the volume of the accumulator?
When choosing the volume of the accumulator, one should start from:
- Number of water consumers
- Number of points of water intake
- Average value of water consumption, m 3 / h
- The number of permissible pump on / off cycles (as a rule, it is taken equal to 20, do not have restrictions on the number of on / off, since they have a soft start).
Water and wastewater experts recommend using membrane tanks volume from 50 liters. On average, if your family consists of 3 people, there are 2-3 water intake points in the house - it will be enough to use a 50 liter hydroaccumulator. If 3-4 people live in your house and 4-5 points of water intake - use a GA with a volume of 100 liters. With a water supply scheme with a storage tank, it will be enough to use pumping station... They, as a rule, are equipped with a standard hydraulic accumulator with a volume of 24 or 60 liters.
Accumulator maintenance
During operation, the GA requires preventive maintenance. Firstly: after buying a membrane tank, check the air pressure using a car pressure gauge, it happens that the manufacturer forgot to pump air, or the pressure in the GA is not enough for your needs. Air should be pumped into a “dry” accumulator (drain the water from the membrane before pumping). Check the air pressure periodically during operation (once every half a year), and if necessary, pump it up.
Secondly: the water contains dissolved oxygen, and over time it will accumulate in the membrane of the accumulator, to avoid this - bleed air from the membrane. HA with a volume of 100 liters or more are equipped with a special bleed valve, and for smaller accumulators, you can perform this operation by disconnecting the pump from the network and releasing the pressure from the system (open the tap in the house), if necessary, repeat this operation several times.
Thirdly: the membrane tank should be located or stored at a positive temperature. If your room is not heated in winter period time - take the accumulator to a warm place, thereby increasing the service life of the membrane.
Today, there are membrane tanks of both domestic and foreign production on the market. We recommend using hydroaccumulators of the brand (Italy), since they have long been presented on the Russian market and have proven themselves only from the best side. The flanges of these diaphragm tanks are made of stainless steel, all supplied by HA are factory tested and certified in accordance with the requirements of the European Directive 97/23 / EC.
To create an even and constant flow of water in private water supply systems, hydroaccumulators, pressure or expansion tanks are used. These devices smooth out pressure surges during operation (switching on / off) of pumping equipment or when analyzing a resource by consumers.
The reservoir of such a tank is divided into two compartments by a powerful and elastic membrane. Water enters one compartment (lower) through a filter fitting. The other part of the total tank capacity (top) is filled with air. Work begins by turning on the pump. The increase in pressure in the network provokes the injection of liquid into the lower compartment, while the membrane begins to stretch. When the pressure drops, it squeezes the water back. This is how the destructive shocks of water in the pressure pipes and nodes are smoothed out.
Video review - The principle of operation of the accumulator
A special relay box automatically shuts off the pump when the pressure tank is full. And for some time the energy of the membrane does not allow the pressure to decrease. When the accumulator is empty, the pump starts up again. Such an arrangement relieves the unit pumping water from short-term and frequent start-ups / shutdowns. This reduces the wear rate of its parts. For everything to work correctly, the pressure tank must correspond in capacity to the volume of the required water analysis. Normally, the tank must hold from a quarter to a half of the displacement, which the pipes are able to pass per minute.
Correctly selected volume of the device ensures its frequency of operation from five to fifteen times per hour. In this mode of operation, it is imperative to use a reliable and elastic membrane that can withstand heavy loads.
Since accumulators work in domestic water supply systems, the material from which they are made must be non-toxic, with a permit for use in contact with clean drinking water.
Water entering accumulators for water supply mainly comes from underground wells or wells. Hence, its saturation with oxygen, which is released during the operation of the system, accumulating in the membrane. For this, most modern devices of this type have a safety valve, bleeding air if necessary. As a rule, accumulators are used on cold water supply lines, so the temperature regime in which they are used is more gentle.
It is advisable to install such a pressure element before the water supply circuit begins to branch. The best place is right after the water supply pipe enters the housing. Also, it will not hurt to install a check valve .. Especially if there is no such valve in the pump. In addition, it is recommended to install a pressure gauge to control the generated pressure.
Installation of equipment in the water supply system
Hydroaccumulators are of vertical and horizontal design. Choose one of them that fits more compactly in the allotted place. The mounting position is selected as high as possible. This makes it easier for the whole circuit to function. The fact is that by raising the unit to a height of, for example, 5 m, we get a water column, which “helps” the working membrane with an additional pressure of ½ atmosphere.
Devices such as hydraulic accumulators for water supply are auxiliary devices for cold and hot water systems. They provide the water pressure necessary for the operation of the line. The operation of such systems reduces the number of pump starts and reduces the likelihood of water hammer. They also contain some supply of water, which will be important during a power outage.
How to choose the right one?
It is necessary to choose accumulators for water supply, taking into account the volume of water that this system uses. By their configuration, they are divided into two types:
- vertical, the main advantage is that they take up less space;
- horizontal, it is more convenient to accumulators of the first type, since they have mounts for installing an external pump.
Also important in choosing a hydraulic accumulator is the question of its volume. A tank with a small volume will make the pump cycle more frequent. Still, such devices of small volume are subject to frequent pressure surges within the system. A large tank will allow you to store enough water.
Especially the moment with frequent activation of the pump should be taken into account. Due to frequent switching on, it overheats, which, accordingly, significantly reduces the service life.
However, here you can also pay attention to the choice of the pump itself. Submersible pumps have a limit of 20-30 starts per hour, but external ones are not so picky about frequent starts, therefore they work great with low-volume tanks.
The subjective factor responsible for right choice the size of the accumulator, is an approximate calculation of how many times the pump will turn on in an hour. Or, how many people will simultaneously use water in a room that uses the work of the water supply system. Today there is a patented method for calculating the volume of a hydraulic accumulator, which was developed by Italian engineers. It is intended directly for private houses with sewerage, the presence of bathrooms and other equipment that consumes a sufficient amount of water.
Any design of an autonomous water supply ends with the installation of a hydraulic tank. This is usually a small capacity that is needed to accumulate the media. Simply put, there is water under pressure, which, if something happens, can be used for domestic needs. Let's talk about how to choose the right hydraulic accumulator for water supply systems and what to look for when buying.
General information
In most cases, the hydraulic tank has a plastic body, more expensive models have a metal one. The inner space is divided in half by a membrane, on one side of which there is a carrier, and on the other - air. This design allows you to create a pressure inside the tank of the order of 1.5-2.5 bar, depending on the volume and manufacturer of the product. It must be understood that a hydraulic accumulator for water supply systems is not a storage tank for hundreds or even thousands of liters. In our case, we are talking about a volume of 50-100 liters.
So that's why you need air in the tank's hydro-chamber. The fact is that any pipeline, be it autonomous or central, can be subject to hydraulic shocks. This is a very undesirable phenomenon that destroys the highways. To get rid of it, the system uses an air chamber. It is more malleable than water and allows you to extinguish water hammer. In addition, as noted above, it is needed to maintain constant pressure in the system.
A little about the principle of operation of the device
The hydraulic tank, despite its high efficiency, is extremely simple. From a well or well, as well as any other source, water gets into it. Consequently, the elastic membrane is stretched due to the pressure of the carrier. The volume of air between the wall of the tank and the membrane decreases, and therefore a large pressure is created. When it reaches its maximum, a special sensor is triggered to turn off the pump.
Then the following situation turns out. We turn on the water in our tap, and it comes out of the hydraulic tank under pressure. In the latter, the pressure on the membrane gradually decreases. When it drops to its minimum, the pump turns on. This is roughly how the device works. It is extremely important that the pressure in the accumulator is constantly kept at an optimal level, this allows water to be supplied to the consumer under pressure. It is advisable to carry out maintenance work annually and, if necessary, add air through a special nipple to the tank using a car pump.
Hydraulic accumulator for water supply systems: price and something else
Well, now let's move on to the most interesting thing - the cost of equipment. In most cases, prices vary depending on the manufacturer. Domestic companies are more accessible by pricing policy than European ones. As for the quality, we make quite normal hydraulic tanks. If you follow the operating rules, then problems should not arise.
For example, good hydraulic tanks are made by the Dzhileks company. The hydraulic accumulator of this company for 50 liters will cost you 3,000 rubles. Moreover, its weight is only 8 kilograms. The unit for 24 liters will cost an order of magnitude less - 1,200 rubles. As for European manufacturers, prices are higher by about 7-15%. If the volume of the tank is small, then the difference is insignificant. But in any case, before moving on to the price, you need to calculate how much volume is right for you.
Determining the type of hydraulic tank
The accumulator for water supply systems can be vertical and horizontal. As for the installation method, there is no fundamental difference for the consumer. The main difference between the two is the way the accumulated air in the membrane is removed. Models with a volume of more than 100 liters have a fitting through which air is periodically removed. Notice if there is a fitting. If not, then find a model where it is present.
In vertical accumulators, all the air accumulates in its upper part. In this case, it will not be difficult to remove it. There is a special valve for this. Horizontal hydraulic tanks provide for the installation of an additional pipeline unit. It is a sewer outlet with an outlet nipple. A ball valve is provided to remove air. Which is better, you ask? As noted above, there is not much difference, but it is easier to carry out air removal in vertical-type devices.
About calculating volume
Hydroaccumulators for water supply, the device of which we have considered, have a different volume. The efficiency of the system depends on how correctly it will be chosen. But since the device is often used for different purposes, it is sometimes difficult to calculate the appropriate volume.
If you use a hydraulic tank to reserve water, then its volume must be large. For example, the capacity should be enough for several days of autonomous media consumption for household needs. The situation is quite the opposite in the case of using a device for constant pressure maintenance in the system when the pump is off. There will be enough tank for 20-100 liters. If an automatic water supply station with a hydraulic accumulator is necessary in order to exclude too frequent activation of the electric pump, then a 50-liter tank will be sufficient. Note, it is not recommended to run the pumps more often than once a minute. Considering that a shower can consume 5-8 liters per minute, and a toilet no more than 2 liters, then such a tank is more than enough.
"Dzhileks" (hydroaccumulator) and its features
First of all, I would like to say that it makes sense to pay attention to domestic companies. There are several reasons for this. As noted above, these are more affordable products. But besides this, Russian companies are developing such accumulators that are more suitable for our water intake systems. The result is more stable operation of the device for many years.
As far as this manufacturer is concerned, only good things can be said about him. First, the excellent value for money. All other things being equal, the Jilex tank will cost a little cheaper compared to any “European”, while it will not be inferior in performance characteristics, such as generated pressure, head, volume, etc. In general, this is an excellent solution, and not because it is cheap, but because it is really high quality and convenient.
Frequency of use and volume
These two parameters are closely related to each other. The fact is that the connection of the accumulator to the water supply system is carried out with the expectation that the unit will operate in an intensive mode, that is, under a constant load. Here we are talking about about 5-15 switchings per hour. But often this figure turns out to be different. Why, you ask? It's simple - you miscalculated the choice of tank volume. Let's say they took a volume of 50 liters for a large family, which was not enough. So it turns out that the unit is overloaded. This is not good for a whole host of reasons. Firstly, the pump, whether submersible or surface, is constantly switched on and off, which directly affects its service life. Secondly, the membrane of the hydraulic tank is also subject to intense wear, which is also bad. That is why it is recommended to always take a small stock. Buy a tank not for 50, but for 75 liters. This will be more than enough in most cases. Even if you spend 500-700 rubles more, the device will function for a longer period.
Everyone should know when buying
The water supply circuit with a hydraulic accumulator must necessarily provide for the presence of a hole in the tank for bleeding air. This is due to the fact that, to one degree or another, the carrier contains oxygen, which needs to go somewhere from the hydraulic tank. If you have a model with less than 100 liters, then there may not be a special valve. In this case, it is recommended to carry out preventive maintenance at intervals of 1-2 times a year. The tank is completely emptied and the accumulated air is removed. Otherwise, the system will high blood pressure, which will lead to a decrease in the useful capacity of the equipment.
Conclusion
It is recommended to give preference to hydraulic tanks with metal housings. Let them be somewhat more expensive, but such a solution is effective for the simple reason that the unit is not afraid of mechanical damage.
And horizontal. The name fully characterizes the way they are installed. Which one to choose if the dimensions of your room allow you to use both types.
Choice of accumulator
The selection of a hydraulic accumulator depends on many factors. Here we would recommend paying attention to the method of removing accumulated air inside the rubber membrane. The fact is that in water supply systems there is always dissolved air in the water. Over time, during the operation of the system, this air is released from the water and accumulates in various places, forming air locks. One of these places is the cavity A of the accumulator. To remove this air, as well as air congestions that arise during the installation and repair of the system, an additional nipple is provided in the design of large accumulators (100 liters or more), through which the air accumulated in the system is periodically vented. When using a vertical accumulator with a capacity of more than 100 liters, air accumulates at the top and can be removed with this air separating valve.
In accumulators for horizontal water supply, air removal can be done using an additional section of the pipeline, consisting of an outlet air nipple, ball valve and discharge into the sewer. In this case, the accumulated air should be released periodically once a month. Accumulators with small volumes are not equipped with an air separating nipple. Therefore, the choice of the accumulator is carried out exclusively by the convenience of the layout in your room. Removal of the accumulated air in them is carried out by periodic complete emptying. For this, an additional ball valve can be provided in the pipeline diagram. In addition, air can be removed from systems with a small accumulator simply by periodically (once a week) turning off the power supply to the unit and bleeding the accumulated air through the washbasin or shower tap or another draw-off point closest to the accumulator. However, for greater efficiency, this procedure should be repeated several times. That is, turn off the power supply to the pump, open the cold water tap, completely drain the water, close the tap and turn on the power supply to the pump. And so two or three times in a row.
How to choose the size of the water supply accumulator?
The correct selection of accumulators for individual water supply systems is quite difficult. There is a large amount of background data to consider. In addition to the traditional shower and faucet in the kitchen, modern homes can be equipped with a bath, bidet, drain, washing machine and other equipment that requires water to operate. In addition to the equipment, the number of people in the house may vary. These are objective factors, but when choosing the size of the accumulator, subjective factors also have to be taken into account. For example, how many times per hour can you turn on the pump and fill the accumulator? What happens if several people use water at once? What happens if the washing machine is running at this time?
Note that until now, in our opinion, there have been no methods for choosing the volume of accumulators in Russia. First, because there were no individual water supply systems in Russia. Secondly, people have too different requirements for such systems. We offer you a method for selecting the volume of a hydraulic accumulator, which is based on the international calculation method UNI 9182.
To begin with, if you only have a water tap, a shower and a watering tap in your house, then you don't need to count anything. You need a standard water supply installation with a 24 liter accumulator. Feel free to buy it. It is optimal in cases where the number of permanent residents in the house is up to four people. Even if you need to increase the number of water sampling points in the future, you can simply buy separately and install another 24-liter hydroaccumulator at any point in the system.
If you have a house without a sewerage system, but with more than three points of water parsing, then in any case a volume of a hydraulic accumulator of 50 liters is enough for you.
The method for calculating the volume of the accumulator is intended for individual houses equipped with a sewage system (septic tank), with baths and other equipment that consume a significant amount of water.
1. Determine the total coefficient of water consumption Su. To do this, make a list of parsing points in your home and indicate the amount of each type of equipment.
2. Complete Table 1. Its second column is a table of frequency factors for each type of equipment (Cx). In the third column, indicate the number of devices of each type of equipment in your home (n). In the right column of the table, multiply Cx by n. Sum the values for this column. You will receive the total water consumption ratio of your home.
Table 1. Determination of the total consumption coefficient Su
|
Equipment type |
Utilization factor Cx |
The number of each kind n |
Product Cx x n |
|
Sink faucet |
|||
|
Faucet in the kitchen |
|||
|
Dishwashing machine |
|||
|
Watering tap |
|||
|
The total coefficient Su is = _______ |
|||
3. Depending on the obtained value of the total coefficient Su, determine the value of the maximum water consumption required for your home. These values are presented in Table 2.
For example, if you have a toilet, shower, a faucet in the sink, a faucet in the kitchen (one of each device) in your house, then your consumption coefficient is Cy = 3 + 2 + 6 + 2 = 13. The closest value of Cy in the table is 12, therefore, for the normal functioning of the water supply system at home, you need to ensure a maximum flow rate of about 36 liters per minute.
4. To determine the volume of the accumulator, it is necessary to decide how many times per hour (s) it is allowed to turn on the accumulator at the maximum consumption rate. 10-15 times an hour is considered normal. It is also required to assign thresholds for the pressure switch of the water supply station (Pmin and Pmax). The lower Pmin threshold for two-storey houses is usually 1.5 bar, and the upper Pmax threshold is 3 bar.
Calculation of air pressure in the accumulator
What is the initial air pressure in the accumulator? If you have installed a hydraulic accumulator in the basement, then its minimum value is easy to calculate. It is necessary to take the height in meters from the basement to the top of your water supply system. For example, for two-storey house this is 6-7 meters, three-story - about 10 meters, then add 6 to this value and divide by 10. You will get the required value in atmospheres. For example, for a two-story house, 7 + 6 = 13/10 = 1.3 atmospheres. This is the minimum value of the air pressure in the accumulator. Otherwise, water from it will not flow to the second floor of your house. However, these values should not be overestimated, otherwise there will simply be no water in the accumulator. Usually the manufacturer sets the air pressure to 1.5 atm., But it may happen that the air pressure in the accumulator you bought will be different. You should initially check it with an ordinary pressure gauge, connecting it to the nipple of the accumulator and, if necessary, increase it using a car pump.
The difference between the response thresholds Pmax - Pmin determines the amount of water produced by the hydraulic accumulator. The greater this difference, the more efficient the operation of the accumulator, but in this case the membrane is loaded more heavily and may rupture.
The Pmin value (pump activation pressure) is determined based on the hydrostatic pressure (water height) in the water supply system of your home. For example, if the height of the pipes in your system is 10 meters, then the pressure of the water column will be 10 meters, which is equal to the pressure of 1 bar.
What should be the minimum pressure Pmin? The air pressure in the back pressure chamber of the accumulator must be equal to the hydrostatic pressure, that is, in our case, 1 bar. The lower response threshold Pmin should then be slightly higher (by 0.1 bar) than the air pressure in the accumulator.
However, we need the system to work steadily. The most critical, from the point of view of stability of operation, is the highest parsing point (for example, a faucet or a shower on top floor). The valve works normally if the pressure drop in it is at least 0.5 bar.
Therefore, the pressure must be 0.5 bar plus the hydrostatic pressure of this point. Thus, the minimum value of the gas pressure in the accumulator is 0.5 bar plus the value of the reduced hydrostatic pressure at the point where the accumulator is located (the distance in height between the upper point of parsing and the point where the accumulator is located). In our case, if the accumulator is located at the lowest point of the water supply system, then the minimum gas value in it should be assigned 1 bar + 0.5 bar = 1.5 bar, and the threshold of operation (switching on) of the pump Pmin = 1.5 + 0.1 = 1.6 bar. If the accumulator is located at the upper point, and the pressure sensor is at the lower point of the system, then the gas pressure in the accumulator should be set to 0.5 bar, and the pump activation threshold Pmin = 1.6 bar.
When setting the upper threshold for the automatic water supply system, it is necessary to take into account several points, first of all, the pressure characteristic of the pump. The value of the head created by the pump in meters of water column divided by 10 will show the maximum pressure value. However, it is necessary to consider:
The characteristics of the pump indicate the maximum parameters without taking into account the hydraulic resistance of the pipelines;
The voltage in the electrical network often does not correspond to the nominal 220 V;
At maximum head values, the pump flow is minimal and your system will take a very long time to fill.
With prolonged operation, the pump performance decreases.
There are quite a few GA models on the market, differing in characteristics, manufacturer and price. And this makes the choice of a product somewhat difficult. It is pointless to list the entire range of accumulators; moreover, not all of them meet the criteria of "quality, reliability, durability". If you look at the information on thematic forums (and it is the most objective), then most often the following GAs for water supply are honored with praise from users.
1. Reflex
Products from Germany under the well-known brand "Reflex DE" are specially designed for installation in water supply circuits. The range of products on the market allows you to choose the most suitable model. The tanks differ both in capacity (from 8 to 500 liters) and maximum pressure (up to 10 bar).
The body material of all accumulators is high-quality steel, protected on top by a polymer layer. The type of all vessels is closed. Installation options are not limited, as you can choose a floor-standing model or with a wall mount.
2. Gilex
Russian GA, which is not inferior to imported counterparts (judging by the reviews of the owners of private buildings). But the price is about 1.8 times lower.
In production, only "galvanized" steel is used. The "control" compartment in industrial models is initially filled with inert gas, household samples - with air. Depending on the modification of the accumulator inside the tank, there may be either a flexible membrane or a "pear" (which is preferable from the point of view of maintainability), where water comes from the water supply pipe.
3. Unipump
Another domestic company that develops and supplies various pumping equipment and components for engineering systems, including water supply, to the market. Hydroaccumulators "UNIPUMP" differ in a more significant model range.
There are mini-tanks with a capacity of only 2 liters (323 rubles), which are advisable to install to protect the pump from overloads, for example, on summer cottages... That is, where the internal volume of GA (as a water reserve) is not one of the defining criteria. All products are made of steel, both vertical and horizontal.
4. Stout
These accumulators of a well-known Italian brand are now produced in our country. In fact, they are expansion tanks of a membrane type and of sufficient capacity (from 50 liters). They are able not only to protect the system from water hammer, but also to provide the house (for some time) with a supply of water in case of force majeure. For example, when you turn off the prom / voltage.
Execution - horizontal and vertical, steel body, design pressure - up to 10 bar. Prices are quite reasonable, even for large-capacity samples.
What to consider
The accumulator is selected individually for each water supply system. Its optimal parameters are determined based on engineering calculations. What can mistakes lead to, which often happens when choosing a GA "by eye" or on the advice of a "knowledgeable person"?
- Accelerated development of the pump resource due to frequent switching on / off. As a result, the service life is reduced.
- The absence of a hydraulic accumulator in the water supply scheme leads to increased wear and tear of all plumbing installed in the house.
- Incorrect operation of household appliances (malfunctions, protection activation, and so on).
- Inconsistency of pressure, especially with the simultaneous opening of several taps in the cold water system (for example, in the bathroom + in the kitchen), draining water into the toilet.
- Systematic water hammer in pipes. Consequences - equipment breakdown, the occurrence of leaks at the joints in certain sections of the circuit.