Circulation pump?
Circulation pumps are mainly used in heating systems with the so-called forced circulation. They move the coolant (water or gas) in closed pipelines and help it overcome significant pressure.
In order for a pump of this type, it is first necessary to calculate its approximate performance. This is required in order to estimate its maximum load. In addition, the operating conditions of the circulation pump must also be taken into account. The main ones among them are the temperature of the coolant and the diameter of the pipeline. The higher they are, the more expensive and reliable pump you will need.
To choose the right pump, it must be filled with water before starting
Surface pumps are used to pump water from wells up to 8 meters deep. They are divided into so-called self-priming pumps and pumps with normal suction. The first are designed to supply water directly from its natural source; the latter are used to artificially increase pressure in the water supply leading from the source.
To choose the right pump, it must be filled with water before purchase. Especially for this surface pumps equipped with a small hole with a stopper. After that, it is necessary to evaluate the pressure created by the pump, its performance. It is not recommended to use a surface pump in a well in which the pressure exceeds its capacity: it can easily fail.
Choosing the right pump is quite difficult.
Submersible pumps are used for pumping water from a depth of 3 to 10 meters. However, unlike surface pumps, submersible pumps are characterized by a more complex design and high power. At the same time, it is more difficult to take care of them. At least once every six months submersible pump must be cleaned by disconnecting its hose.
When choosing a submersible pump, pay attention to its power. It is a key parameter for this type of pump. The higher it is, the more reliable the pump.
The fundamental difference in the design of the pumps is related to the scope of their application and, consequently, to the way they are installed. For a conventional non-self-priming centrifugal pump, which is used to pump liquids and pressurize or pump liquids to a higher level, a suction valve is required to prevent reverse current fluid when the pump stops. During installation, the pump and suction pipe must be filled with liquid. After filling, the pump is ready for operation.
When the pump is running, the rotation of the impeller throws water to the pressure pipe. This creates a vacuum on the suction side of the impeller. Atmospheric pressure directs the liquid through the valve and suction pipe to the suction port and the impeller, which again pushes the liquid to the pressure port. Thus, the vacuum in the suction pipe of the pump depends on the following factors:
- suction lift
- friction resistance in the valve and suction pipe
- liquid density.
The pressure in the discharge port of the pump depends on the back pressure in the system. If the water is directed in the opposite direction from the discharge pipe, then there is no back pressure in the system, not to mention atmospheric pressure. The work performed by the pump is to lift the pumped liquid from the tank and overcome friction losses in the pipeline.
If we pump water into a tank located 10 meters above the pump, then the pump must lift water from one tank to another, create a pressure of 1 bar above atmospheric pressure, and also overcome friction losses in the suction pressure pipes. The pump operates with an efficiency greater than 73%, and under the following conditions:
- lifting height on the suction side - 3 meters
- pump flow - 40 m3/h
- friction losses in the suction pipe - 2 meters, including valve losses
- losses in the pressure pipeline - 2 meters
NPSH is the height of the liquid column above the suction port of the pump. Simply put, these are the conditions under which the pump will not be able to create an absolute vacuum. All centrifugal pumps have an NPSH characteristic indicating the conditions under which the pump will not be able to pump a water column of 10.33 meters high, which under normal conditions is the specified head of absolute vacuum at sea level.
The NPSH characteristic depends on the flow. It increases with the increase in consumption. An increase in the characteristic indicates a decrease in the ability of the pump to create a vacuum. NPSH is the minimum suction pressure for trouble-free pump operation.
Cavitation occurs when the pump tries to lift water from a greater depth than is possible. In such a situation, the impeller will break up the water flow, causing steam bubbles to form. Since these bubbles have been transferred from an area of low pressure to an area of high pressure, under the influence of this pressure they will begin to explode. The resulting sound wave creates a lot of noise and can cause damage to the pump and its bearings after some time in this mode. In pumps that do not have solid stainless steel impellers, cavitation can cause major damage. Impellers made of cast iron, plastic or bronze are usually damaged.
Mass loss table for various materials in connection with the occurrence of cavitation shows that the loss of stainless steel is only 0.05% of the corresponding mass loss of a cast iron wheel under the same conditions.
The correct selection of the pump depends on the following conditions
- Installation conditions
- Water quality (gas content, corrosivity)
- Drive (energy source): - electric motor - internal combustion engine - solar energy
If the pump is mounted on a base or in a well where it will be protected from “flooding” during heavy rains or rising groundwater levels, good choice there will be a centrifugal self-priming pump or pressure boosting stations. If the distance between the pump and the water surface is more than 6-7 meters, apply borehole pump.
The use of three-phase well pumps is always preferable. The efficiency of a single-phase asynchronous electric motor decreases already at a 5% voltage drop, and at a 10% drop, problems arise when starting the engine. In the case when only a single-phase source of electricity is used and a voltage drop may occur, it is necessary to install an electric motor with a trigger capacitor. Also in this case it is possible to use a motor with a permanently magnetized rotor and a frequency converter providing three-phase starting torque and constant efficiency up to 15% voltage drop. With a voltage drop of up to 35%, even in such an electric motor, efficiency losses and problems during start-up will occur.
A self-priming pump can be used to pump water from a well or reservoir. Since this pump has a valve on the suction pipe, the suction pipe does not need to be filled with water. If the pumped liquid is corrosive, the pump must be made of materials that are resistant to aggressive substances in the water. Corrosion is a problem that often requires the help of a specialist. When determining the aggressiveness of water, the first factor to be established is the pH value. The durability of materials at various pH values is shown above and is an initial reference material. As you can see, stainless steel is a material with a wide range of applications, but it also has limitations.
When stainless steel is exposed to salty liquid, it can be subject to two types of corrosion: pitting and crevice.
Pitting appears in small holes in the surface of stainless steel and increases when there are small imperfections. Pitting corrosion can also occur where there are inclusions of normal carbon steel on stainless steel surfaces, e.g. from filing or grinding. Therefore, a very important point is the cleanliness of the steel surface after machining.
Crevice corrosion appears, as the name implies, in cracks and crevices when stainless steel parts are under load, and also after poor welding.
Theoretically, both types of corrosion are of the same nature and can be very intense and progress very quickly under favorable conditions, i.e. in salt water (presence of chlorides), at high temperatures and low pH.
In places with a reliable source of electricity, where the level groundwater located below 7 meters from the ground, it is proposed to use pumps:
- Downhole pumps (asynchronous)
- Downhole pumps (permanently magnetized rotor)
In places with a reliable source of electricity, where the groundwater level is at least 7 meters above the ground, it is proposed to use four types of pumps:
- Single stage centrifugal pumps (in-line)
- Multistage centrifugal pumps (in-line)
- Horizontal multistage centrifugal pumps
- Self-priming pumps
If there is no power supply, a gasoline or diesel generator can be used, which is suitable for running all types of pumps with standard electric motors.
More economical for the operation of pumping systems is the use of solar energy, but this is not possible everywhere.
In the case of a sufficient number of low-paid labor, it is possible to ensure the supply of water to the house and livestock with the help of hand pumps. But such pumps cannot supply water under pressure.
Before the final choice, it is necessary to know the maximum water consumption and the required pressure. Let's divide water consumers into two categories: one category consumes water periodically, the other - for a long time.
The first category includes draw-off points that consume water for a maximum of 10 minutes, such as washbasins, kitchen sinks, toilets, etc. A distinctive feature of this category is that water never flows from all taps at the same time. A family of two, for example, can usually use no more than two taps at a time, no matter how many there are in the house.
Moreover, washing and dishwashers take water periodically, depending on the installed program. Therefore, it is obvious that choosing a pump with a very high performance is not economically advantageous in terms of cost, since it will not be used to its full capacity.
Possible maximum pump flow - this flow does not actually occur in practice, and it is calculated as the maximum flow that theoretically can occur.
Actual pump head: Several factors influence the operation of a centrifugal pump when pumping water:
- Suction lift (from water surface to pump)
- Friction loss in suction pipe and valve
- Height from pump to highest draw point
- Friction losses in the pressure pipeline (depending on performance)
- Required minimum pressure in taps (depending on fittings)
In practice, 80% of the pumps sold are installed to replace old ones that have worked out their useful life. When selecting a pump for replacement, system parameters such as the age of the pipes, the type of check valve in the well, the type of water taps in the house, and the level of rust and sludge deposits in the pipes often remain unknown. Therefore, it is necessary to predict these factors in order to more accurately determine the friction coefficients.
First, you must find out the type of pump that was previously in this installation. Based on the information received, you will be able to determine the type of new pump. If there is not enough information on the old pump, you should find out from what depth the pump should pump water (for example, 6.05 m) and what is the distance from the pump to the top draw-off point (in the example, 21.5 m). Then add 10 meters corresponding to the required pressure at the top draw-off point. After that, we determine the total pressure:
6.05 + 21.5 + 10 \u003d 37.55 meters, to this value you need to add about 30%, equal to 11.26 meters, the margin for friction losses in the suction valve, pipeline, connections, etc. Thus , the actual pump head will be equal to: 37.55 + 11.26 = 48.81 meters.
In some systems, this procedure can result in either very high or very low pump head.
If a multi-stage pump has been chosen, this problem is easily solved by changing to a model with a different number of stages, without much change in installation.
The last thing to do before installing the pump is to determine if it can provide the required head: Terrain: 300 meters above sea level Water temperature: 17°C Reserve: 1 meter . strength.Nmax = 10.1 - 1.0 - (0.8 + 0.64) - 0.2 - 1.0Nmax = 6.46 meters
This is more than the actual suction lift of 6.05. This means that the correct pump has been selected for installation.
Note: if there are any problems with too high a suction head, the pump must be installed with a larger suction pipe and a non-return valve.
The fundamental difference in the design of the pumps is related to the scope of their application and, consequently, to the way they are installed. For a conventional non-self-priming centrifugal pump that is used to pump liquids and pressurize or pump liquids to a higher level, a suction valve is required to prevent liquid backflow when the pump stops. During installation, the pump and suction pipe must be filled with liquid. After filling, the pump is ready for operation." />
The operation of a well is impossible without the use of a mandatory component of its arrangement - a pump. After all, a bucket is absolutely not suitable for taking water from a narrow trunk. In addition, it would take too much time and effort to lift from the depth and transport the water manually. You don't want to waste either one or the other, do you agree?
Properly selected pumping equipment will fill the containers in the bathhouse, house, garden in a matter of minutes. Now there is an opportunity to purchase equipment for servicing an object of any scale. On its basis, you can easily build an automatic plumbing system that does not depend on centralized supplies and the participation of owners in the pumping process.
We will tell you in great detail how to choose a pump for a well, what you need to take into account and provide for the future owner of the device. A scrupulous explanation of important points for the user is supplemented by photo and video guides.
Before purchasing a suitable pump for a well, it is necessary to clarify a number of indicators of its construction:
- static level;
- dynamic level;
- debit;
- bottom base mark;
- pipe diameter.
Drilling a well or arranging a well on the territory personal plot- this is only a partial solution to the problem of providing oneself with the required amount of water for domestic needs and watering green spaces. To organize the rise of water from an underground source, as well as its transportation through the pipeline system and supply to all points of water intake under the required pressure, a well pump is needed. You will also need additional elements that are equipped with such equipment. On how correctly the selection of the downhole pump is carried out, in other words, whether the device corresponds to the parameters of the underground source itself and the created plumbing system, will depend on the efficiency of the latter.
Given the fact that pumping equipment on the modern market is represented by a wide variety of models, the question of which pump is best for a well is quite relevant. When choosing a water pump for a well, you should get an idea about the types of such devices and their technical specifications, as well as to understand in what situations it is better to use hydraulic machines of various types and modifications.
All pumps used for water wells are divided into two large categories of devices:
- surface type pumps;
- submersible pumps for wells.
To understand which pump to choose for a well, you should consider each of the categories of such equipment in more detail.
Types of surface-type pumping equipment
Surface pumps for wells, installed on the surface of the earth, in close proximity to the source of water supply, in turn, are divided into various types that differ from each other in design and operating principle, as well as technical capabilities.
Surface Type Hand Pumps
Manual surface pumps, which can be installed both on a well and in wells, are the simplest and, accordingly, the most inexpensive pumping equipment. The choice of a borehole pump of this type is advisable if there is still no power supply in the house or in the country house or there are frequent interruptions in its supply. Actuated by the muscular strength of the user, the hand pump in such situations will provide the required amount of water for both watering plants and domestic needs. Drilling a well when choosing a hand pump can be given minimal attention, since its depth will be very small.
The design of a surface hand pump for water, which can be used to service only those sources that are characterized by shallow depth, includes the following elements:
- working cylinder;
- a piston moving along the working cylinder, due to which suction or expulsion of the pumped liquid medium from the internal chamber of the pump occurs;
- air and water valves operating in antiphase;
- the lever by which the piston is actuated.
Often, a hand pump and an electric pump are installed on the well at the same time, connecting them with a tee to make it possible to switch between them. In such cases, the hand pump acts as a backup device to be used during power outages.
Self-priming surface pumps
When selecting a pump for a well, the depth of which does not exceed 10 meters, many owners of cottages and country houses prefer self-priming surface devices. As the latter, centrifugal-type pumping equipment is most often used. The housing of such pumps, installed in close proximity to the water supply source, does not come into contact with the pumped liquid medium, which greatly simplifies their design. The intake of water from an underground source when using such hydraulic machines is carried out using a flexible hose or pipe placed in the well or well shaft to the appropriate depth.
When choosing the simplest surface centrifugal pumps for a well, it should be borne in mind that their drive unit is cooled only by ambient air, so the user of such equipment must constantly monitor the degree of heating of the casing. To organize the operation of a self-priming hydraulic machine in automatic mode, it must be equipped with additional technical devices that will have to be purchased independently.
Due to the low performance indicators, the simplest self-priming pumps are not chosen for a full-fledged water supply to a summer residence or country house. Such hydraulic machines, as a rule, are used to equip the simplest water supply systems, as well as to organize temporary irrigation systems for household plots with water from a shallow well, a special reservoir or a natural reservoir.
Self-priming centrifugal pumps are pumps with a built-in ejector or venturi tube
Domestic pumping stations
Pumping stations are capable of ensuring the efficiency of the functioning of an autonomous water supply system for a house or a summer residence, equipped with a hydraulic accumulator in addition to self-priming pumping equipment. The main purpose of the accumulator, which is a tank with a membrane element, is to maintain the required water pressure in the pipeline system serviced by the pumping station.
Pumping stations, in order to ensure their operation in automatic mode, are equipped with control devices and control mechanisms. Such pumping stations automatically respond to a decrease in the pressure of the pumped liquid medium, to a decrease in the pressure of the liquid flow supplied to the pipeline system, as well as to a decrease and increase in the water level in the accumulator.
If you decide to choose a pumping station for servicing a well, keep in mind that with its help it will not be possible to pump water from underground sources whose depth exceeds 10 meters. This is explained by the fact that the main element of equipping such stations is a self-priming surface pump, which is not capable of creating a flow of a liquid medium with a high head pressure. In addition, the surface pumps that such stations are equipped with create a lot of noise during their operation, which should be taken into account when choosing a place for their installation.
Pump stations with ejector and injector elements
If you, as the owner of a summer house or a country house, are interested in choosing a pump for a well whose depth exceeds 10 meters, pay attention to pumping stations equipped with external ejector or built-in injector elements. When using such elements in the pipeline, an additional circuit with a smaller flow area is created. Moving along this circuit, the pumped liquid medium acquires additional acceleration, which contributes to an increase in the head of the liquid flow in the intake pipe.
Equipment with ejector or injector elements allows the use of pumping stations for servicing wells, the depth of which is in the range of 10–25 meters. Meanwhile, the disadvantages of pumping stations of this type should be taken into account, the most significant of which include:
- not too high performance (this is due to the fact that part of the water pumped out by such equipment from an underground source is not sent to the intake pipe, but for circulation through the ejector circuit);
- loud noise, forcing the user to pumping station take seriously the issue of soundproofing the room in which it is installed.
Submersible pumping equipment
In cases where the depth of the underground source from which water is to be pumped out is significant, it is better to choose submersible (deep) type pumping equipment for the well. A deep well pump, as its name implies, is located in the thickness of the liquid medium it pumps, and the liquid itself is supplied to the surface through a hose or pipe connected to the pressure line of the equipment. The drive motor, which is equipped with submersible pumps for the well, is powered by a well-insulated cable. The submersible pump is lowered into the well and fixed in it at the required depth with the help of a safety cable, the lower end of which is tied to a special eye on the hydraulic machine body, and the upper end to a crossbar installed on the surface of the earth.
The fact that submersible pumping equipment is constantly located in the thickness of the liquid medium pumped by it explains design features such devices. Thus, the housings of submersible pumps, for the manufacture of which corrosion-resistant materials are used, are subject to increased requirements for tightness. The drive motor placed in such a housing, as well as the terminals for connecting the power supply, must be reliably protected from contact with the liquid medium.
When buying a pump for a well, many people think about which one to choose. In this case, it is better to give preference to models with a built-in coarse filter. Such a filter, which is equipped with many modern models well pumps, will reliably protect the working chamber of the equipment from the ingress of solid inclusions contained in the pumped water into it.
How to choose a deep (submersible) pump for a well? In the basic configuration best models there is already such a useful device as a check valve, which does not allow the water pumped by the hydraulic machine to move through the system in the opposite direction. If there is no such valve in the configuration of the purchased pump, you will have to purchase it yourself.
There is another important question that consumers ask: which well pump to buy - surface or deep? Here, one should take into account such advantages of submersible type devices as:
- almost complete absence of noise during operation;
- the impossibility of freezing the liquid in the pump, since it is constantly in the water column, the temperature of which never drops below zero degrees;
- reliable protection against overheating (water pumped by deep pumps simultaneously performs the function of cooling their moving parts);
- high performance and a large value of the created pressure, the value of which for the best pumps for wells can exceed 100 meters of water column.
Before choosing a submersible type well pump, study the disadvantages of such devices, which, in particular, include:
- the complexity of installation, for which it is often necessary to involve third-party specialists;
- the need to use high-quality electrical cable when installing;
- the difficulty of monitoring the operation of the hydraulic machine, as well as performing maintenance and repair.
On the modern market, various brands and types of submersible pumping equipment are offered, differing from each other both in design and characteristics, and in the principle of operation, so it is important to know how to choose the right model for such a device.
Vibration type models
Vibration pumps, which are characterized by a simple design, are among the most inexpensive devices among submersible pumping equipment. Such pumps, which do not have high performance, can be successfully used to solve many problems associated with pumping water from underground sources and reservoirs. The best vibration-type borehole pumps, which are also characterized by low energy consumption, are capable of creating a pressure of a liquid medium reaching up to 20 or even more meters.
For the movement in the inner chamber of the vibration pumps of the piston, which provides suction and expulsion of the pumped liquid, the membrane connected by a rod to the anchor is responsible. The armature is attracted to the core of the electric coil and repelled from it under the influence of an alternating magnetic field.
The most significant disadvantages of vibration type pumps include the following.
- Created by such devices in the pumped liquid medium vibration waves contribute to the destruction of the walls of the wells, if the latter are not protected by anything.
- Such pumps are quite critical of the solid inclusions contained in the composition of the liquid medium.
Thus, if you are faced with the question of how to choose a submersible pump for a well with unprotected walls, the water in which is characterized by the presence of solid impurities in the composition, select another type of equipment.
Centrifugal type models
How to choose a borehole pump that will effectively pump out water from underground sources, even at very considerable depths? In this case, experts recommend paying attention to centrifugal submersible devices. Pumps of this type are presented on the modern market in a wide variety, which allows them to be optimally selected according to the parameters of both the well and the water supply system that is planned to be serviced with the help of such equipment. Centrifugal pumps are also good because they operate almost silently, do not create vibration waves in a liquid medium, demonstrate high performance and form a liquid flow with a strong pressure.
The main structural element of a centrifugal pump is a wheel with blades, which, by moving the pumped liquid in the internal chamber of the device, creates a centrifugal force that helps to throw the liquid medium against the walls and push it out through the discharge pipe. In the middle part of the working chamber of the pump, during the course of the described process, the air becomes rarefied, which ensures the suction of fluid from the well through the inlet pipe of the equipment.
The main disadvantages of centrifugal type deep-well pumps are:
- complexity of installation in the well;
- the need for fairly frequent maintenance;
- quite high cost.
Screw type models
A screw deep pump is a fairly rare equipment used for domestic purposes. The pumping of a liquid medium when using pumps of this type is carried out due to the rotation of a screw or auger in the cavity of their inner chamber. Capturing portions of the liquid medium entering the working chamber through the inlet pipe, such a screw moves them to the pressure pipe.
Screw-type pumps are able to successfully cope with pumping not only water, but also quite viscous and heavily contaminated liquids, as well as service wells, the depth of which reaches 40-50 meters. The most significant disadvantage of pumps of this type is the presence in their design of a large number of friction units, which is the cause of intensive wear of this equipment.
Vortex type models
In cases where it is required to form a liquid flow with a high head pressure at the outlet of pumping equipment, vortex-type equipment can be preferred when choosing. The special design of the impeller of such pumps and the presence of special grooves on the walls of their inner chamber make it possible not only to act on the pumped liquid by centrifugal force, but also to give the liquid additional acceleration due to the formation of turbulent flows.
Along with high performance, vortex-type pumps are characterized by relative simplicity of design and low noise. Such pumps, which is also their advantage, can be used for pumping liquids containing gas bubbles in their composition.
Pump Selection Criteria
When deciding how to choose a pump for a well (choose a vibration, vortex or centrifugal unit, which company or brand), you should be guided by several parameters. At the same time, remember that an incorrectly selected pump will not only not provide the required efficiency of the water supply system, but will also need frequent maintenance and repair.
So, if you do not know how to choose a pump for a well, be guided by the following parameters.