How much should be the air pressure in the accumulator. Choose a hydraulic accumulator. Tank volume calculation
Accumulator (expansion membrane tank) serves to maintain pressure in the pressurized water supply system, and when used in conjunction with a pressure switch, allows you to create an automatic station based on a submersible or surface pump. The main purpose of the accumulator in the system is to maintain and smoothly change the fluid pressure in the system.
Thus, the rise of the latter corresponds to an increase in pressure in the regulator, which led to the rise of a small plunger and the evacuation of water located above the counter-piston, so that the obturator follows all the movements of the small plunger diver. The equilibrium is established when the servomotor is in the normal position, the regulator's water acts on the rod from the bottom up, and the water trapped above the counter current opposes any movement.
Then it can be assumed that with holes cut from a movable wall having different cross sections at different points of their height, their overlapping with fixed holes can give sections along the length of the obturator in accordance with a predetermined law to achieve a constant flow rate regardless of the pressure difference, at which is the flow of fluid during the passage of these holes. When the vehicle’s load is minimal and, consequently, the pressure drop between the battery and the drive presses increases, the plunger is lowered, and the same holds for the obturator and its piston, and then when the water is pressurized.
Additional functions that the accumulator performs are as follows:
- Protection against water hammer (changes in pressure in a liquid caused by an instant change in its speed)
- Minimum water supply
- Limitation of intermittent pump starts
Thus, it is the accumulator that makes it possible to use a pressure switch and automate the water supply process. Without a hydraulic accumulator, the relay cannot work correctly, since an instant change in the pressure in the system (at the moment of opening the valve, turning off or connecting new consumers, turning the pump on or off, etc.) would cause the relay to constantly operate. And this, in turn, leads to instability of the feed, overheating or breakdown of the motor, breakdown of the relay.
In this case, the holes are reduced in cross section due to the relative displacement of the perforated cylindrical walls; when, on the contrary, the maximum vehicle load increases, the pressure drop decreases, the back pressure is discharged and the shutter rises, the cross section of the holes increases to maintain a constant flow.
At that moment, when the vehicle should slow down, the shutter rotates by itself at an amplitude of 50 °, which blinds nine-tenths of the holes and leaves free passage only on the tenth remaining, without changing the height situation or the equilibrium condition of the moving part of the system.
Since water is practically not compressible, turning on the pump in the system with a pressure switch, but without a hydraulic accumulator, would cause an instant increase in pressure in the system and the relay would immediately react to this and turn off the pump. On the other hand, when the tap was opened, the pressure would immediately drop and the relay would react and turn on the pump.
The compressibility coefficient of water \u003d 5 x 10 ^ 10 1 / Pa. Those. an increase in water pressure (pressure created by the pump) practically does not cause a change in its volume (these are hundredths of a percent). Therefore, the pressure would change in the system at high speed, which would cause a constant relay operation.
This drum is provided around the circumference with two corresponding cams, the first at the first station and the second at the ground station and the second stage. When the drum rotates, these cams that protrude lower the branch of the lever, which opens the slider of a small hydraulic press. This press, using a combination of connecting rods and a lever, rotates the movable shutter.
A gear drum receives a gear movement that is connected by bevel gears to a lower return pulley mounted on a large bridge. When the vehicle is on the ground, the cam corresponding to this station presses the lever branch of the small drive press, and therefore the obturator rotates and most of its openings are closed. The toothed drum first slowly rotates, and soon the first-floor cam leaves the lever arm. At this moment, the shutter turns in the opposite direction, and all of its openings become free.
It must be clearly understood that the accumulator does not create any pressure and does not pump water to the consumer - the pump does all this. It only maintains the liquid pressure that is created in it by the pump and delivers water at that moment in time, while the consumer valve is open and the pump does not turn on. For example, the question “How much accumulator do I need if I have two showers?” Is not entirely correct. Because when using a shower (one or two), the accumulator supplies water only until the pump is turned on, and then only the pump delivers water for the remaining time of use. And it will stop only after all the taps are closed and the pressure in the tank rises to the shutdown pressure.
Is it possible to increase the volume of the accumulator?
Since water has a much larger cross section, the speed of the engine pistons increases to a normal value. This happens until the vehicle reaches a level below the first stage, the cam of this station lowers the lever branch again, and a slight press closes the shutter again.
The units of this device are identical to the devices of the previous one. The openings of the movable obturator are designed to reduce the cross-section, when the piston rises as a result of evacuation of water on its upper surface, this occurs in the case of maximum vehicle loading, the pressure difference between the drive presses and the battery increases, while the shutter goes down and opens large openings for the minimum load on the vehicle. The space around the stations is the same as for the previous device.
Sometimes it happens that the pump turns off even while consumers are using water. However, this mode of operation is undesirable (since after a short time the pump will have to turn on again) and indicates that the selection of the pump and / or settings of the entire system were not performed correctly (in most such cases, you need to change the settings of the pressure switch).
Water flowing out of the cruise control and going to the presses at the time of lifting or exiting the presses, to go to the regulator during descent, goes to the connector of the drive presses located between the two previous devices. The connector, which is a common device for raising and lowering, is designed to equalize the pressure on the pistons of the engine and reduce the flow of water by two pistons, which at the moment are more efforts than others. This throttling occurs until equal pressure is established on the two divers.
Any accumulator is divided by a membrane into two cavities: air and water. By supplying pressurized water to the water cavity of the tank, the membrane expands and compresses the air in the air cavity. Thus, the membrane is balanced by pressure from two sides (P1V1 \u003d P2V2). The pressure will increase until the pump shuts off according to the pressure switch set point (pump shutdown pressure). At the beginning of the flow of water, air presses on the membrane, thereby expelling water from the accumulator. The water pressure slowly drops and when the pressure for turning on the pump is reached, the relay closes the contacts and the pump starts. This is the concept of the automatic operation of the pump together with the accumulator and pressure switch.
Thus, this is a safety device in the hand, the purpose of which is to supply water with sufficient pressure to lift it in a small so-called rescue pipe located along the elevator path and to act with the help of the means in the vehicle’s brake cylinders if this is stopped the vehicle on its way as a result of the brakes and when it is necessary to perform a rescue maneuver, up or down to the nearest station.
The multiplier consists of a packaged piston equipped with a large rod and which can be moved in a cylinder of cast iron. The rod goes between it and the cylinder into the annular space, which is currently filled with water under the pressure of the batteries and communicates with the rescue tube.
What should be the air pressure in the air cavity of the accumulator?
The pressure in the air cavity of the accumulator must be 10% less than the pressure on the pump.
Moreover, air pressure should be measured only on a tank disconnected from the system (without water pressure). Air pressure must be regularly monitored and, if necessary, brought back to normal, this will significantly extend the life of the membrane. For the same purpose, it is not recommended to make the pressure drop between turning the pump on and off too large. The optimum is a difference of 1.0-1.5 atm. Larger differences stretch the membrane more strongly (load), thereby reducing its service life, and moreover, large pressure drops are not comfortable when using water.
Installation, testing, connection
If the water also works under the same pressure under the piston, that is, on its solid section, the piston rises, and the water pressure in the annular space is multiplied by the ratio of the internal cross section of the cylinder to the surface of the annular space. This pressure is thus multiplied, sufficient so that the most unfavorable water rises to the top of the road and lifts the vehicle to its brake pistons acting as sockets.
It is necessary to use a small special pump, installed next to a large one, and work for an outlet pressure of 20 kg per cm 3, sufficient to lift the battery at low pressure. This pump draws water from the elevator discharge tank into a common high pressure pipe.
Hydraulic accumulators are recommended to be installed in places not subject to flooding and with low humidity. In this case, the accumulator flange will last much longer. Since no loads are perceived by the tank, there is no need for additional fastening. The accumulator can simply be installed on the floor on regular supports.
In addition, safety devices limit movement in each of these directions. In the case of high-pressure accumulators, at the upper limit of their stroke, they emit a certain amount of water, which is returned to the low-pressure line using a safety relief valve.
This water, so that the apparatus can operate at temperatures below 0 °, mixes strongly with glycerin; the proportion is about 25%. It is always the same water that is used, with the exception of losses due to leakage of the device, and is supplied in a discharge tank installed at the foot of the elevator.
When choosing a particular brand of hydraulic accumulator, attention should be paid to the membrane material, the availability of certificates and sanitary certificates confirming that the hydraulic accumulator is intended for use in systems with drinking water. Also, it will not be amiss to make sure that there are spare membranes and flanges so that in case of problems you do not have to buy a completely new tank.
This amount of water is enough to supply presses, for a blow. In addition, the low pressure accumulator into which the pump is sucked must have the same capacity as the previous one. The practical characteristics of the device are as follows. Therefore, it can vary from 0 to 39%, depending on whether the cabins are empty or full.
The maximum vehicle speed on the road should be about 2.5 m per second. Expected durations for different periods of the course. 1st floor: 30 "First floor: 2nd floor: 30" Second floor: 60 "High-speed from the 2nd to 1st floor: 30" First floor: 60 Downhill from the first floor to the floor: 60 "Stop and change of passengers on the floor: 60 ”Total: 360. Therefore, the return trip must be made in 6 minutes.
The maximum pressure that the accumulator is designed for must not be less than the maximum possible pressure in the system (for example, if the pressure switch breaks down). That is why most tanks are designed for a pressure of 10 bar.
The question often arises as to how much water is in the accumulator?
For example, if you turn off the electricity, how many liters of water can be used?
Each system consists of a high pressure pump, nozzles, manifold and computer. In conventional diesel fuel injection systems, fuel pressure must be generated separately for each injection. Pressure is created on the high pressure pump, which compresses the fuel and delivers it through the high pressure pipe to the ramp, which acts as a common high pressure accumulator for all injectors - hence the name "common rail".
Then the fuel is fed into the nozzles, which, in turn, inject fuel into each cylinder. Clean and efficient fuel injection thanks to extremely short spray intervals and few injections High engine power and regular operation with reduced fuel consumption and emissions Compatible with all car models thanks to the modular design. The high pressure pump compresses the fuel and then doses the required amount. It continuously supplies a high pressure fuel accumulator and maintains system pressure.
This value depends on the settings of the pressure switch. As you might guess, the higher the pressure difference between turning the pump on and off, the more water will enter the accumulator, but this difference must be limited for the reasons stated above.
As an example, we give a table of filling capacity of accumulators.
The required pressure is available even at low speeds, while the generation of pressure is not related to the engine speed. Most conventional rail systems are equipped with radial piston distribution pumps. It is installed in each cylinder of the engine and is connected to the ramp through a high pressure hose. The injector is controlled by an electronic diesel control system, which guarantees the opening or closing of the injector needle by a drive, whether it is an electrovalve or a piezoelectric.
Air Pressure Monitoring Intervals
Both options have a very short switching time and provide pre-injection, main injection and post-injection, thereby ensuring clean and efficient combustion of fuel at each operating point. Secretary of State for Industry.
| P air bar | 0,8 | 0,8 | 1,8 | 1,3 | 1,3 | 1,8 | 1,8 | 2,3 | 2,3 | 2,8 | 2,8 | 4,0 |
| P incl. Bar | 1,0 | 1,0 | 2,0 | 1,5 | 1,5 | 2,0 | 2,0 | 2,5 | 2,5 | 3,0 | 4,0 | 5,0 |
| P off, bar | 2,0 | 2,5 | 3,0 | 2,5 | 3,0 | 2,5 | 4,0 | 4,0 | 5,0 | 5,0 | 8,0 | 10,0 |
| The total volume of the tank, l | Water supply, l | |||||||||||
| 19 | 5,70 | 7,33 | 4,43 | 4,99 | 6,56 | 2,53 | 7,09 | 5,37 | 7,46 | 6,02 | 8,11 | 8,35 |
| 24 | 7,20 | 9,26 | 5,60 | 6,31 | 8,28 | 3,20 | 8,96 | 6,79 | 9,43 | 7,60 | 10,24 | 10,55 |
| 50 | 15,00 | 19,29 | 11,67 | 13,14 | 17,25 | 6,67 | 18,67 | 14,14 | 19,64 | 15,83 | 21,33 | 21,97 |
| 60 | 18,00 | 23,14 | 14,00 | 15,77 | 20,70 | 8,00 | 22,40 | 16,97 | 23,57 | 19,00 | 25,60 | 23,36 |
| 80 | 24,00 | 30,86 | 18,67 | 21,03 | 27,60 | 10,67 | 29,87 | 22,63 | 31,43 | 25,33 | 34,13 | 35,15 |
| 100 | 30,00 | 38,57 | 23,33 | 26,29 | 34,50 | 13,33 | 37,33 | 28,29 | 39,29 | 31,67 | 42,67 | 43,94 |
| 200 | 60,00 | 77,14 | 46,67 | 52,57 | 69,00 | 26,67 | 74,67 | 56,57 | 78,57 | 63,33 | 85,33 | 87,88 |
| 300 | 90,00 | 115,71 | 70,00 | 78,86 | 103,50 | 40,00 | 112,00 | 84,86 | 117,86 | 95,00 | 128,00 | 131,82 |
| 500 | 150,00 | 192,86 | 116,67 | 131,43 | 172,50 | 66,67 | 186,67 | 141,43 | 196,43 | 158,33 | 213,33 | 219,70 |
| 750 | 225,00 | 289,29 | 175,00 | 197,14 | 258,75 | 100,00 | 280,00 | 212,14 | 294,64 | 237,50 | 320,00 | 329,55 |
| 1000 | 300,00 | 385,71 | 233,33 | 262,86 | 345,00 | 133,33 | 373,00 | 282,86 | 392,86 | 316,67 | 426,67 | 439,39 |
According to this table, in a 200 liter accumulator with the following pressure switch settings:
Pump start - 1.5 bar
Pump Off - 3.0 bar
Air Pressure - 1.3 bar
The water supply will be 69 liters, which is about a third of the total volume.
In conclusion, a few words about the required volume of the accumulator.
V t \u003d K x A max x ((P max +1) x (P min +1)) / (P max - P min) x (P air + 1)
At the suggestion of the Director of Regional Action and Small and Medium Industry. At the end of the monitoring of commissioning or, as the case may be, the corrective actions that might have been requested, the inspection body must confirm the end of the monitoring, followed by a hit sign in the vicinity of other regulatory labels. It provides the owner with a certificate that must be attached to the file specified in “Article 9 B” of the relevant press equipment. However, this information is stored at the disposal of the agents responsible for monitoring pressure vessels. The technical documentation provided for in paragraph 3 of the same Appendix 3 may be shared by several families of similar pressure equipment and may be produced once a year, in which case it should be addressed to the Minister responsible for industrial safety until March 31 of the year following the commissioning commissioning such equipment under pressure. The declaration referred to in the first paragraph of Article 15, and, if necessary, the inspection referred to in the second paragraph of this Article, is also required in case of significant changes or a new installation outside the facility where pressure equipment was previously used. Visible and conspicuous interventions should be governed by the special provisions set forth in this section. The criteria for classifying interventions should be specified in a professional manual submitted to the Minister of Industrial Safety for approval after consultation with the Central Commission on Pressure Apparatus. The specification elements referred to in Article 9a This document is an integral part of the file referred to in Article 9 of this Decree. § However, this obligation to belong to a group with such an inspection body does not apply to piping interventions. § In addition, the various elements listed in Appendix 1 to this Appendix are kept at the disposal of agents responsible for the supervision of pressure vessels. However, among the well-known operations carried out on steam generators or steam vessels, the professional guidance referred to in Article 28 determines those that are subject to complete overload. Vessels referred to in the last paragraph of Article 23 above shall be exempted from the hydraulic test referred to in paragraph 2 above. Inspection may be limited to repair or change of parts. Any noticeable interference with pressure equipment should be carried out in accordance with the basic requirements specified in Appendix 1 to the Decree of December 13. However, the final inspection provided for in paragraph 2 of this Annex may be limited to the consideration of supporting documents regarding the operation and visual inspection and related non-destructive tests, which may be limited to repaired or modified parts. This document is an integral part of the descriptive file referred to in Article 9a of this Order. If they are not dependent on any provisions regarding the design or manufacture of the equipment concerned, their benefit should be maintained regardless of the system in which the equipment was manufactured. For such equipment, the documents referred to in subparagraph (a) of Article 9 are established by their operator on the conditions specified by the Minister responsible for industrial safety, after receiving the opinion of the Central Commission for Pressure Vessels. In addition, such equipment must be exempted from the hydraulic test provided for in Article 25 of this Order. The Director of Regional Action and Small and Medium Industry is responsible for the implementation of this Order, which will be published in the Official Journal of the French Republic. Done at Paris on March 15.
A max - estimated maximum water flow (liter / min)
K - coefficient depending on the power of the pump motor (see table below)
P max — pump shutdown pressure, bar
P min - pump start pressure, bar
P air - pressure in the air cavity of the accumulator, bar
| Pump power, kW | 0,55-1,5 | 2,2-3,0 | 4,0-5,5 | 7,5-9,0 | ||||||||
| Coefficient K | 0,25 | 0,375 | 0,625 | 0,875 | ||||||||
We choose the minimum required volume of the hydraulic accumulator for the water supply system based on the Aquarius BCPE 0.5-50 U pump with the following settings:
P max \u003d 3.0 bar
P min \u003d 1.8 bar
P air \u003d 1.6 bar
A max \u003d 2.1 m³ / h (35 l / min)
K \u003d 0.25 (since the pump power is in the range of 0.55–1.5 kW)
V t \u003d 31.41 liters
We select the next closest accumulator volume - 35 l.
Note that the tank volume at the level of 24-50 liters is in excellent agreement with other methods for calculating hydraulic accumulators for domestic water supply systems and the empirical recommendations of various manufacturers of pumping equipment.
A larger volume should be selected if frequent power outages occur, however, it must be remembered that in any case, water fills about a third of the total volume (see the occupancy table above). And of course, the more powerful the pump is installed in the system (relevant for pumps with a capacity of 1.1 kW and above), the larger the size of the accumulator must be preferred, this will reduce the number of intermittent brief starts and extend the life of the pump motor.
When buying hydraulic accumulators of large volumes, one must be aware that water should be used regularly, because with prolonged downtime, its quality begins to deteriorate. After all, using all the water from a hydraulic accumulator with a volume of 24 or 50 liters is much simpler and faster than using 100 or 200 liters.
Models and prices for accumulators can be found in the "
(hydraulic tank) is a water tank with a pear-shaped membrane. It is located inside, while tightly attached to a metal casing connected to a water supply source. You will need it in order to maintain a steady pressure and cushion hydraulic shocks, both at home and in the enterprise.
The principle of operation of the unit
The key task of the device is to provide the necessary pressure when your pump is off.
Let’s take a closer look at the features of the work so that, if necessary, we can carry out minor repairs or adjustments ourselves.
When the fluid enters the hydraulic tank, the size of the membrane increases. And this means that the entire volume of air there is systematically reduced, while increasing pressure in the system.
As soon as the planned pressure level is reached, the pump is turned on and off.
At the same time, the pressure in the system decreases depending on how much water has already been consumed. Only when it falls to a predetermined mark, the contacts will touch, and the device will resume work.
Take a note: be sure to check, at least once every 10-12 months, the air pressure in the accumulator at a time when there is no water in it. If the pressure in the system is below the established norm, it must be raised. The most ordinary car pump will come to the rescue.
Types of appliances
Hydraulic accumulators differ in their installation method and size. On the market you can find vertical and horizontal devices.
If the size of your private home or production hall allows, it is best to opt for the most powerful equipment. This will help fight the dissolved air that will inevitably be present in your system. Because of this, air jams appear periodically.
To eliminate them in devices of large volumes, starting from one hundred liters, a special water supply device called a fitting is used. A valve is mounted on it, which systematically vents excess air.
On units of vertical position, it accumulates in the upper sections and is eliminated by a special valve.
In horizontal, it is etched due to a special section of the pipeline. But if you have a small volume device, then it will not have such advantages.
What pressure should be in the accumulator: check and adjust
The pressure that must be installed in the apparatus, for example, at 24 liters, depends on its location.
If it is on the minus-first floor, then to calculate the minimum value, you need to add six and divide by ten to the height parameter (calculated in meters from the maximum point of your water supply system to the unit).
For a 2-storey country cottage, the height will be approximately 6 meters. Thus, as a result of the calculation, we obtain 1.2 atmospheres. If you assume that the pressure is below this mark, then the water will not be able to stably circulate throughout the building.
The initial value set at the manufacturer, as a rule, is one and a half atmospheres. But in a specific accumulator, this value may turn out to be different, so it must be checked. This must be done using a conventional pressure gauge.
How to choose the right device
When choosing a device, pay close attention to volume. Its significance for the operation of the equipment as a whole is extremely great.
It serves for:
- the formation of a certain supply of water;
- replenishment of extremely high losses with frequent and large water consumption;
- minimize too frequent on / off the pump;
- maintaining a stable pressure in the water system while the device is turned off.
Please note: the smaller the distance between the accumulator and the pump, the better the whole system will function, and the easier it will be to carry out tuning. 
If they are located at the same level, then the filling will occur approximately the same.
Otherwise, the volume of water in the second unit will be less due to the difference in performance. When deciding on the final volume of equipment you need, calculate how much water you will need in the general bill.
Here are the main parameters for the average water consumption per minute in a country cottage:
- a little more than one liter will go to the bathroom;
- for full-fledged work, a shower will require from 9 to 10 liters;
- about 8.5 liters are consumed in a kitchen sink when washing dishes.
Thus, if you have two toilet rooms, and all the points mentioned consume the resource at one time, then, in general, you will need about 20 liters.
Making a discount on the percentage of filling the tank and on the limited number of pump starts in one hour, we conclude that a volume of 80 liters will be sufficient for you.