Calculation of pumping equipment. Calculation of a pump for a well in a suburban area
The reason is not in the quality of equipment, but in the fact that the project and selection are carried out not by professional designers, but by the owners of private organizations. For example, a “layman” cannot know that the engine of a pump selected with a large margin can burn out if the pump is not brought into the operating range during installation and setup of the system. How to avoid such mistakes when choosing a pump?
DEFINITION OF PUMP PARAMETERS
In all cases, for the correct choice of the pump, first of all, it is necessary to determine its operating parameters - flow Q and pressure H... The required water consumption is determined from the total productivity of all water points of the facility, taking into account the likelihood of their simultaneous use.
In a simplified calculation, you can use the following water consumption rates for plumbing fixtures: washbasin - 60 l / h; toilet flush cistern - 83 l / h; kitchen sink - 500 l / h; bathroom - 300 l / h; watering tap - 1080 l / h (watering lawns and flower beds requires 3-6 m 3 of water per square meter, while the consumption also depends on the method of irrigation and the intensity of irrigation); a sauna or bath will require about 1000 l / h. The following formula is used to calculate the required pump head:
H tr \u003d H geo + S + H free
Where H geo - the height of the pipeline inlet in the building relative to the dynamic water level in the well (the numerical expression of the dynamic level must be present in the well certificate); S - the sum of the friction head losses in the pipeline and local resistances (fittings, fittings, filters, etc.); H free - the pressure that must be created at the entrance to the building, with the calculation of the provision at the most remote and high-located water draw-off point of pressure equal to 0.5 atm.
Well parameters are fundamentally important to the user, as they are used to calculate the required head and performance of the selected pump. In the well passport, the drillers must have work. Obviously, the calculation results will turn out to be incorrect if, in determining the dynamic level of the well, a pump of obviously lower power was used than is required to supply the facility in accordance with the consumer's requests.
And although it is difficult for the user to expect to quickly obtain an official passport for an artesian well (this is a state document that requires many permits and approvals), it is necessary to require the submission of detailed data on the well together with the act of work performed, incl. inquire about the power of the pump, which was used to pump out water when determining the dynamic level. When concluding a contract for drilling work, you should pay attention to the availability of a license from the contractor.
At the end of the work, only serious companies always give the client a guarantee and a detailed well passport, where all the mentioned characteristics are clearly stated, as well as the diameter of the casing string, the list of soils passed, information about the trial pumping of the well, etc. - up to the recommended pump brand and installation depth.
Parameters required Q and H for additional equipment (jacuzzi, washer, sprinklers, "sprinklers", etc.) are indicated by the manufacturers. When installing water-purifying filters, head losses (usually about 2 atm.) And water consumption for washing them are taken into account. For the pool, only the filling time is indicated.
EXAMPLE OF CALCULATION AND SELECTION OF A PUMP
The initial data are as follows:
It is required to provide water supply to a suburban area with a two-story cottage (a kitchen, two bathrooms and a shower with hydromassage require a flow rate of 1 m 3 / h and a pressure of 4-5 atm.), A garage, a house for service personnel (contains a bathroom), a bathhouse, a 45 m swimming pool 3, irrigation of the territory, water treatment system.
A family of four and two of the staff permanently reside on the site. A well 80 m deep was drilled for water supply of the site; casing diameter - 150 mm; static level - 46 m; dynamic level - 50 m; the flow rate measured during pumping is 3.5 m 3 / h.
The calculation is done like this:
Taking into account the water consumption rates (see the beginning of the article), we get the total consumption and pressure of consumers:
Q sum \u003d 500 + 3 x (60 + 83 + 500) + 1000 + 1000 + 2 x 1060 \u003d 6500 l / h \u003d 6.5 m 3 / h,
H tr \u003d 50 + 8 + 20 + 2 +30 \u003d 110 m.
Due to the inexpediency of using all the taps at once, the required flow rate can be determined as 5 m 3 / h.,
The design data is satisfied, for example, a pump
Grundfos SP 5A (Q \u003d 5m 3 / h, H \u003d 120m).
This ensures sufficient consumption for the kitchen, one bathroom and watering. It is understood that the owners will not use the bathhouse and take a bathroom, take a shower and fill the pool at the same time as watering the area from both taps. It is cheaper to use separate pumps to ensure pressure on irrigation installations and hydromassage - this will allow not to keep the entire water supply system under high pressure and will make the operation of the submersible pump more stable, and the system flexible and independent (with an additional pump you can always get high pressure at any point of parsing). The pool will fill up at night. In this case, with the help of a valve on the head, the pump should be "throttled" (create additional resistance) so that when working on filling the pool, the flow does not exceed the permissible - 6.5 m 3 / h.
IF PUMP OUTPUT IS OVERHANCED
Self-selection of a pump by a customer with excessive requirements for flow and head often leads to the selection of a pump with too high power. In the case of the initial data discussed above, such a pump can be Grundfos SP 14A-25. As already mentioned, when installing an overpowered model, complications are possible.
Firstly, since with such a choice, the nominal flow significantly exceeds the average water demand, the pump will operate in a frequent on / off mode. Manufacturers allow up to 30 pump starts per hour, but only for one hour per day, with a general limit of 60 cycles per day. In any case, frequent switching on negatively affects the service life of the electric motor and starting automatics. To avoid this, a large diaphragm tank will need to be installed.
Secondly, if the pump power is overestimated, as a result, the water pressure at the entrance to the house will be overestimated. At the moment of starting such a pump, strong hydraulic shocks will inevitably occur. Some fittings may simply not be designed for such pressure (dishwashers and washing machines, mixers), additional installation of pressure reducers will be required to reduce the pressure. Thirdly, during the filling of the pool, the pump will work on the "open pipe" without creating pressure.
In such conditions, there is a large flow of water at minimum pressure. The duty point of the pump shifts on the characteristic curve to the right, into an area that does not correspond to the working area of \u200b\u200bthe pump. The shaft power will be at its maximum and the engine will fail during prolonged operation.
The consequence of using a pump with an overestimated capacity will be a general rise in the cost of the entire system, caused by the use of more powerful electrical equipment, materials and fittings with a high permissible operating pressure, an increase in the diameters of the pipeline and wells, as well as an increase in the cost of water treatment. If the nominal pump flow exceeds the well flow rate, it is necessary to install additional dry running protection.
Choking and adjusting the pump will result in excessive energy consumption. In other words, with the provision of the possibility of simultaneous use of all water points by installing an overpowered pump, the cost of the water supply system will increase. At the same time, the real water consumption will be much lower. Therefore, although the final choice will always remain with the customer, it is cheaper and more correct to choose a pump taking into account real needs and with the help of specialists.
It is possible to satisfy the user's requirements for the water supply system, subject to the rules for its installation and operation, by choosing the pump with a flat operating characteristic that is optimal in this situation.
For the water supply system from the example above, a Grundfos SP 8A-25 pump can be selected. In the zone of possible feeds (from 4 to 8 m 3 / h) for this model, the curve of the dependence of the head on the flow rate has a flat form, that is, at low water flow rates, there will not be too much pressure increase. At the same time, a certain allowable reserve when calculating water consumption will exclude the possibility of water shortages.
INSTALLATION OF SUBMERSIBLE PUMP
In any case, whichever pump is chosen, during installation it is necessary to adjust its operating point in all possible modes of operation. During commissioning, the supplied flow rate should be measured (determined by the filling rate of a container of a known volume, for example, a barrel), the generated pressure (according to the pressure gauge on the head) and the current consumed (measured by current tongs).
The obtained characteristics are checked against the pump passport data from the catalog. If the operating parameters are exceeded (a power reserve is provided, for example, for the subsequent installation of filters), it is necessary to close the valve at the exit from the well, create additional local resistance sufficient to set the correct operating point - the middle of the Q (H) characteristic.
The installation, as well as the selection of the pump, must be carried out by trained specialists, and the installation company must be licensed.
SUBMERSIBLE PUMP PROTECTION
Before choosing and purchasing a pump, it is necessary to obtain accurate information about the power supply voltage at the facility. This is especially important when choosing an imported pump. All equipment supplied from abroad meets, first of all, the industrial standards of the country of origin. So, for German pumps, the permissible deviation of the mains voltage from the nominal is -10 ... + 6%.
Despite the built-in protections, the pump is not designed to operate from a network with a voltage below 200 V, all possible drawdowns and voltage surges will negatively affect the service life of the electric motor. Here it is necessary to provide for an adjustable voltage protection as part of the control cabinet, and for three-phase pumps also against "non-phase" operating modes. It is not recommended to install powerful single-phase pumps. The starting current of a 2.2 kW motor can exceed the rated current by 4.4 times!
To stabilize the voltage within the operating range with such surges, a stabilizer with a fivefold power reserve will be required (more precisely, the choice will be made by the manufacturers of the stabilizer).
Sometimes it is cheaper for the user to provide a 380 V power supply at the facility than to ensure the correct operation of a single-phase pump. According to statistics, about 85% of failures occur precisely with the electrical part of the pump. The main reason is the turn-to-turn closure of the stator windings due to overheating due to hydraulic overload, or when operating at low or abruptly changing voltage. Both can be avoided with proper overcurrent protection.
A conventional starter with overcurrent protection does this quite well, but some installers forget to adjust to the required current value. The result of such negligence is easy to calculate: you will have to pay for lifting the pump from the well, repairing it (the price of a new engine), for lowering the pump again and putting it into operation. The accumulated amount can easily exceed the cost of a new pump.
Glossary of terms
Pressure - excess pressure generated by the pump.Consumption - the volume of water by the transfer pump per unit of time.
Working point - the point of intersection of the curve of the pump characteristics Q (H) with the resistance characteristic of the pipeline SQ2, corresponding to the effective values \u200b\u200bof the head and flow when operating on a specific water supply system.
Throttling - creation of additional resistance on the pressure pipeline.
Performance characteristic - graph of the dependence of the operating parameters of the pump - head and flow rate Q (H).
Shaft power - the power consumed by the pump.
Static level - constant water level in the well.
Dynamic level - the water level in the well, which is established when pumping out the specific flow rate.
Well flow rate - stable water flow provided by the well.
Our Company offers a wide range of domestic and industrial submersible pumps: for water supply, irrigation and drainage. With assortment and technical characteristics You can find it on the website page.
The range of pumps on the market that provide water delivery from wells and wells is diverse, and includes downhole, submersible and self-priming modifications. We are more interested in borehole pumps, which have such advantages as high power, small size, large potential volume of produced water.
Compared to surface pumps, these installations differ primarily in the installation features: the apparatus is immersed in a well, where it lifts the water up. The most widespread are pumps made of stainless steel or composite. Due to their compactness, it is not difficult to place them in a tight underground space. But, despite such a small size, these units are able to provide water production from depth up to 650 meters.
Borehole diameter
To find out the value of this parameter, you should refer to the passport that is attached to the purchased well. From it you can learn and about the type of casing, the number of columns and so on. Based on this information, it will be much easier for you to choose the optimal pumping unit for the well. This should not be neglected, given that the proposed borehole pumps have different diameters. If the value of this parameter of the downhole pump is larger than the casing, then you will not be able to insert it into it. In this case, you will have no choice but to look for a more suitable pump.
- GRUNDFOS model - diameter 75 mm.
- Model PEDROLLO - diameter 100 mm.
- SPERONI model - diameter 100 mm.
- AQUARIUS model - diameter 100 mm.
Importance of considering diameter
If you have an idea of \u200b\u200bthe diameter of the well, which is the casing, then it will not be difficult for you to find a suitable downhole pump. However, you should consider important point: selectable diameter should be 1 cm more than the calculated... Such a gap is necessary to create a cooling effect on the pump, as a result of which air will enter the space between the pump and the pipe wall.
Most often on sale there are pipes with the following standard sizes:
- Casing pipe 100 mm (suitable for Grundfos SQ models);
- Upsetting pipe 133 mm (suitable for Grundfos SQ, Pedrollo 4Blokm, Aquarius models);
- Casing pipe 159 mm (suitable for the above models).
Well productivity
Manufacturers also provide information about this characteristic in the certificate for the well. Such information will also make it easier for you to select the right downhole pump. Let's say if the recommended performance indicator given in the passport is 3 cubic meters per hour, then you should not exceed this value by purchasing a pump model that can provide high performance. The fact is that by using such equipment, you create a threat of well failure.
Static and dynamic water level
You can also find out such information from the well passport, which, as a rule, is issued upon completion of drilling. Based on these indicators, you can determine distance from the wellhead to the water. From this data, you can find out to what depth the borehole pump will have to be lowered. Moreover, this indicator should be taken into account not in its original value, but with a slight adjustment: 3-5 meters will have to be added to it, given that the borehole pump will have to be located below the water surface.
In this case, naturally, one should take into account the fluctuations in the water level due to the seasonal factor. For example, in summer, the water level may drop within the range from 1 to 5 meters. The exact value depends on the well itself, as well as on the specific area. In other words, in order not to be mistaken when choosing a pumping unit, you should pay attention to the minimum water level observed throughout the year.
Let's say for a well, drilled to a depth of 50 meters, in which the indicator of the static level is 15 m, and the dynamic level is 20 m, the distance from the water surface to the wellhead will be 20 m. This value will correspond to a pressure of 2 atmospheres.
Distance from home to well
At first glance, it may seem that this parameter is not so important. Naturally, it will not be possible to find out this indicator from the passport for the well. However, you cannot do without it in order to find the right pump model. Based on this indicator, you will find out what additional load the Grundfos borehole pump will have to cope with to raise water, say, into a hydraulic accumulator located in a house.
Please be aware that for every 10 meters horizontally there will be 1 meter vertically, in other words, this will correspond to 0.1 atmosphere, which will be created in the pipe placed in the trench.
- Pressure in the hydraulic tank accumulator... Given the purpose of the borehole pump, most often the produced water enters the hydraulic tank, and from there it goes into the system under pressure. But before that, the pump will have to cope with the resistance that is maintained in the hydraulic tank system. Therefore, in order to select an efficiently operating borehole pump, you need to take this point into account. For example, in a hydraulic tank with a capacity of up to 300 liters, the maintained pressure is usually at the level of 3.5 atmospheres. As for models with a volume of more than 300 liters, then a pressure of 5 atmospheres is created in them.
- Required design water flow... To determine this indicator, it is necessary to proceed from the number of people permanently living in the house, including those who will arrive for a while and will use the water supply system. Another parameter that you need to pay attention to is the number of draw-off points. On average, if we consider a standard country house as an example, it should have about 120-180 liters per person per hour. To calculate the required indicator for a borehole pump, this value should be multiplied by the number of people living in the house. It is also important to remember that the average value is meant here, and therefore it is necessary to provide a margin when selecting a pumping unit. It may happen that when all the tapping points are used simultaneously, the water consumption rate may exceed the consumption rate of 120-180 liters. In other words, so that such fluctuations do not leave any point of consumption without water, it is desirable that for each resident there are about 300-400 liters per hour.
Determination of pressure
When the maximum flow rate is calculated, taking into account the characteristics of the well, it will be necessary to determine the required maximum head. To simplify the solution of this problem, you can use the following formula:
H \u003d Ptapx10.2 + Hgeo + SHf ,
where Ptap is the pressure that must be maintained in the system. Most often, it corresponds to an indicator of 2-3 bars. It is this level that is maintained in a conventional urban network;
Hgeo - geodetic head. This parameter is calculated as the distance between the dynamic level and the maximum draw-off point, water meters are used as the unit of measurement;
SHf is the total number of head losses along the length resulting from the movement of water through the pipeline, losses occurring on specific sites systems - bends, tees, valves, etc.
It should be noted that local losses are taken an indicator of 15-20% of the length loss... An important parameter to be taken into account is the presence of a filter in the system. It can also lead to loss of head and can be seen as a source of local losses. Moreover, their value can be quite large. The difference in their number may be related to the type and size of the filter. To get more accurate information about this indicator, you should look in the passport for the installed filter.
After we learned the necessary information and characteristics of our system, only one problem remains unresolved - the choice of a downhole pump. Let's assume that the calculated data turned out to be as follows:
Based on the borehole diameter, the optimal choice for us would be a pump with a diameter is in the range of 3-4 inches... After that, you need to turn to performance: it is important to understand which pump model will be able to maintain the required head.
- The dynamic level indicator is 20 m, which corresponds to 2 atmospheres.
- The well is located at a distance of 15 m from the house, which is equivalent to 0.15 atmospheres.
- With the pump running at the time of water injection, the hydraulic accumulator tank will be 3.5 atmospheres.
Perform some simple calculations, we get that the minimum head of our installation, taking into account the specified characteristics of the well will be 57 meters (2 + 0.15 + 3.5 \u003d 5.65 atm.).
However, it is important to foresee the loss of pressure and productivity in the pipeline, which can be quite significant. This can often be observed in a system in which the water supply pipes are noticeably inferior in diameter to the pump outlet. Let's say a pump from the Danish manufacturer Grundfos SQ has an outlet diameter of 40 mm.
In such a situation, it would be unacceptable for us to lay a 25 mm line. However, these are not the only losses that can occur during system operation. They can be present on a variety of bends, tees, taps, which can reduce pressure by 0.1-0.4 atmospheres per node. In addition to this, voltage instability in the mains should be taken into account, and this can adversely affect the efficiency of the pump. Most often, the amount of losses occurring on pipes and fittings is about 10-20%. For high-quality water supply, the selected borehole pump must maintain pressure in the system at the level of 1.2-1.6 cubic meters per hour.
- Decrease in liquid level - 0.5 atm.
- Losses in the pipeline - 0.4 atm.
- Losses as a result of voltage drops in the network and a margin for pump wear - 1.5 atm.
Therefore, if we take into account the pressure loss, the likelihood of a decrease in the water level in the well, the instability of the voltage in the household network, the optimal choice for us would be a pump model that will be able to provide a pressure of at least 8.05 atmospheres (5.65 + 0.5 + 0.4 + 1.5). In other words, its capabilities should allow lifting water to a height of 80 meters.
Conclusion
The choice of a borehole pump seems to be a difficult task, given that it is necessary to take into account a large number of different characteristics... It should be remembered that not everything depends on the operating parameters of the pump purchased. Attention must also be paid to the characteristics of the well. If there is a discrepancy between them at least according to one criterion, then there can be no question of the efficient operation of the water supply system. When choosing a pump for a well, one should also take into account the fact that certain losses will be observed during the rise of water.
For this reason, the selected pump model should create a pressure in the system slightly higher than the calculated one. It must also be remembered that the system may experience peak periodswhen all the draw-off points are work to the limit... And if such situations arise quite often, then the previously calculated indicator of the design pressure should also be increased.
All of the listed parameters are not the only ones, which complicates the procedure. correct selection pumping unit. In this regard, it is desirable that both the installation of the pump itself and the selection be carried out by specialists who can take into account all the nuances, starting with the characteristics of the well and ending with the water consumption in the house, as well as ensure the efficient operation of the water supply system after the completion of installation work.
- Date: 28-06-2015
- Views: 534
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- Rating: 11
- Pump parameters
- Calculation example
- Overpower
- Installation and protection
To ensure uninterrupted operation of the well, it is necessary to use special equipment... One of the highlights on this list is the pump. To ensure quiet operation, a submersible unit is used, which is of high quality and compact size; it does not generate noise during operation. But the choice of the pump is not so simple, it is required to take into account numerous parameters, to carry out the calculation in accordance with all requirements and norms.
For uninterrupted flow of water from the well, you need to choose the right pump in terms of power.
Pump parameters
When it is important to carry out calculations that will show what performance is required. You cannot buy a unit that is too weak or powerful, as this will immediately cause many problems, additional financial costs will be required. The calculation necessarily includes obtaining data on the water pressure H and water flow rate Q.
When calculating data for the specified parameters, you can use the following indicators:
- washbasin - consumption is 60 l / h;
- toilet tank - 83 l / h, if an economical model is not used, which reduces consumption by about 3-4 times;
- kitchen sink - 500 l / h;
- taps for watering lawns and other things - about 1080 l / h. Additionally, it is required to summarize greenhouses, etc., if they are available on the site;
- for flower beds, approximately 3-6 cubes per 1 m² of area are needed;
- bath, sauna - consumption is 1000 l / h.
All points for determining the flow rate are summed up, the total value for water consumption per hour is obtained. The calculation of the pressure is made using the following formula:
Htr \u003d Hg + S + Hsv
Here Hg is the height of the pipeline level relative to the observed dynamic well level. S is the total head loss, local resistance. This applies to plumbing fittings, filters, fittings and others. Нсв is the head that is required when the pipe is introduced into the building. The pressure at the highest point and farthest from the source should be 0.5 atmosphere.
If a jacuzzi, sprinklers, irrigation systems will be used in the house, then the parameters specified by the manufacturer in the instructions must be taken into account. Pools require filling times to be considered, but it is best to use the data from the company that installed them. For the installation of equipment in the pool, it is worth inviting a specialist who will make the necessary calculation exactly. Calculation of the pump is an important and responsible process, errors lead to the fact that installation is very difficult, there is a need for additional costs for equipment and maintenance of the entire system.
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Calculation example
The calculation of the pump for the well can be done independently. The whole process of calculations is demonstrated more clearly by an example.
Initial data for calculations:
- It is necessary to arrange water supply for a two-story country cottage. The watershed points include a kitchen, 2 bathrooms, a shower room with a hydromassage system, a garage, a staff house with one bathroom, a swimming pool, a sauna, watering for the site, and a water purification system. For a house, the total water consumption is approximately 1 m³ / h at a pressure of 4-5 atmospheres. The pool volume is 45 m³.
- There are 6 people permanently living on the site, of which a family of 4 people and 2 are attendants.
A well was drilled for the site, the depth of which is 80 m, the diameter of the used casing string is 150 mm. The dynamic water level is 50 m, and the flow rate during pumping is 3.5 m³ / hour.
When performing a calculation for choosing a pump, it is necessary to take into account the consumption rates of consumers under given conditions:
Q \u003d 500 + 3 * (60 + 500 + 83) + 1000 * 2 + 1060 * 2 \u003d 6500 l / h
Hence it follows that the total consumption is 6.5 m³ / h.
The result is:
Нтр \u003d 8 + 50 + 20 + 30 + 2 \u003d 110 m.
Since all the water intake points are not switched on immediately, the observed flow rate can be set at 5 m³ / h. To select a pump, just such data will be taken into account. For information on possible pump models, you can contact any dealer of the selected brand. For example, the Grundfos SP 5A pump provides the following operating characteristics: Н - 120 m, and Q \u003d 5 m³ / h.
The choice of such a pump allows you to provide the necessary flow for the simultaneous operation of several points in the kitchen, filling one bath, watering the territory. But such a pump is suitable if the taps of the bathhouse and all bathrooms are not turned on at the same time, the pool is filled.
Experts advise purchasing a separate pump for irrigation installations, in which case the required high pressure level will be constantly provided.
As for the pool, it is best to fill it at night when no other points are in use. But at the same time it is recommended to create the so-called throttling on the dampers so that the necessary resistance appears. Thus, during filling, the water supply will not exceed the calculated 6.5 m³ / h.
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Overpower
When choosing pumps for wells and wells, it sometimes happens that the requirements are too high. This leads to the fact that the installation and use of such a pump can be complicated:
- The nominal flow exceeds the average demand, the pump for the well operates in the mode of constant frequent on / off switching, and this negatively affects the condition of the equipment, it wears out quickly. This situation can be corrected, but additional financial costs are required. For example, you can install a diaphragm tank that has a large volume.
- If the power value is too high pumping equipment the inlet pressure to the house will be high, and this will cause severe water hammer when turned on. The fittings may not be designed for them, it may fail some time after the installation of the entire system. Here it is already necessary to install additional gearboxes, which will "extinguish" such drops, but this is again additional financial costs.
- If there is a pool, the pump will operate in the "open pipe" mode, the required pressure will not be created. The flow rate becomes too high, high pressure is applied to the motor shaft, it quickly fails.
Setting up can help in this situation, when the choice is made incorrectly, but the participation of a specialist is necessary. In any case, the purchase of an unnecessarily powerful pump only leads to an increase in the cost of the system, more complex maintenance. And the cost of maintaining the system will be higher. Good submersible pumps must be selected in strict accordance with the calculations, you cannot take too powerful equipment "just in case". It is not only unnecessary, but also creates additional problems.
To choose a pump for a well, you need to know the required head, and one of the parts of determining the required head is to calculate the head loss in the pipeline. This article is devoted to this part of the question.
