Design and principle of operation of centrifugal pumps. Types of impellers of centrifugal pumps. Impeller for Centrifugal Pump: Role in the Design We will manufacture impellers for pumps

The widespread use of centrifugal pumps in everyday life and industry is due to their high performance characteristics and simplicity of design. For the right choice Installation Consider the design of a centrifugal pump and the main types.

In the spiral housing of the unit on the shaft there is an impeller (or several multistage pumps). It consists of front and rear discs (or just the rear), between which there are blades.

The pumped liquid is supplied to the central part of the wheel using a suction (receiving) pipe. The shaft is driven by an electric motor. Due to centrifugal force, water is pushed from the center of the impeller to its periphery. This creates a rarefied space in the center of the wheel, an area low pressure. This promotes the influx of new water.

At the periphery of the impeller, it’s the other way around: water, under pressure, tends to exit through the discharge (discharge) pipe into the pipeline.

Types of centrifugal pumps

1. By number of impellers(stages) centrifugal ones are distinguished:
   • single-stage – models with one working stage (wheel);
   • multi-stage - with several wheels on the shaft.

1. By the number of impeller disks:
   • with front and rear discs - they are used for low pressure networks or pumping thick liquids;
   • only with rear disc.

1. :
   • horizontal;
   • vertical.

1. Based on the amount of water pressure created centrifugal pumps are:
   • low (up to 0.2 MPa) pressure;
   • medium (0.2-0.6 MPa) pressure;
   • high (from 0.6 MPa pressure).

1. According to the number and location of suction pipes:
   • with one-way suction;
   • with double-sided suction.

1. According to the rotation speed of the installation:
   • high-speed (high-speed) - in these models the impeller is located on the sleeve;
   • normal running;
   • slow-moving.

1. By method of liquid removal:
   • models with a spiral outlet - in them, water masses are discharged directly from the periphery of the blades;
   • with a bladed outlet - the liquid exits through a guide vane with blades.

1. According to its purpose:
   • sewer;
   • water pipes, etc.

1. According to the method of connecting the installation to the drive motor:
   • using a pulley drive or gearbox;
   • using couplings.

1. By installation location during operation:
   • surface (external) pumps - during operation they are located on the surface of the earth, and in the reservoir ( cesspool, pit, etc.) the water intake hose is lowered;
   • submersible centrifugal models - such devices are designed to be immersed in the pumped liquid;

Types of centrifugal pump impellers

The impeller is one of the important parts of a centrifugal pump. Depending on the power of the unit and the place of its operation, they differ:

1. according to the material:
   • cast iron, steel, copper are used for the manufacture of wheels operating in non-aggressive environments;
   • ceramics and similar materials – when the pump operates in chemically active environments;

1. by manufacturing method:
   • riveted (used for low-power pumps);
   • cast;
   • stamped;

1. according to the shape of the blades:
   • with straight blades;
   • curved in the direction opposite to the direction of rotation of the impeller;
   • curved in the direction of rotation of the impeller.

The shape of the blades affects the water pressure created by the unit.

Working shaft

This is the part of the installation that is most susceptible to damage during operation. It needs precise balancing and alignment. Materials from which the shaft is made:

• forged steel;
• alloy steel (for installations operating under increased loads);
• stainless steel (for use in aggressive environments).

Types of shafts:

• hard (for normal operating modes);
• flexible (for high speeds);
• connected to the drive motor shaft (used for household models pumps).

The operating principle of a centrifugal pump, as well as the design of a centrifugal pump, is the same for all types of units. It is based on the force effect of rotating blades on the flow of pumped liquid with transmission to it mechanical energy from the working mechanism. The differences between the types of installations lie in their power, the water pressure created and the design.

The main components and parts of centrifugal pumps include the impeller, guide vane, pump housing, shaft, bearings and seals.
Working wheel -. the most important detail pump It is designed to transmit energy from the rotating shaft of a liquid pump. There are impellers with one-way and two-way water inlet, closed, semi-open, axial type.

A closed impeller with one-way water inlet (Fig. 2.2, a) consists of two disks: front (outer) and rear (inner), between which the blades are located. Disc 3 is secured to the pump shaft using a bushing. Typically, the entire impeller (discs and blades) is cast from cast iron, bronze or other metals. But some pumps use prefabricated impeller structures in which the blades are welded or riveted between two disks.

The semi-open impeller (see Fig. 2.2, o) is distinguished by the fact that it does not have a front disk, and the blades are adjacent (with some clearance) to a stationary disk fixed in the pump housing. Semi-open wheels are used in pumps designed to pump suspensions and heavily contaminated liquids (for example, silt or sediment), as well as in some well pump designs.
An impeller with a two-way liquid inlet (see Fig. 2.2, c) has two outer disks and one inner disk with a sleeve for mounting on the shaft. The design of the wheel ensures fluid inlet from both sides, resulting in more stable pump operation and compensation of axial pressure.
Centrifugal pump wheels usually have six to eight blades. In pumps intended for pumping contaminated liquids (for example, sewage), impellers with a minimum number of blades (2-4) are installed.
The impeller of axial-type pumps (see Fig. 2.2, d) is a bushing on which wing-shaped blades are attached.
In Fig. 2.2, d shows a diagram of an impeller with impellers, which serve to unload the axial force or protect the seals from solid particles.
The outlines and dimensions of the internal (flow) part of the wheel are determined by hydrodynamic calculations. The shape and structural dimensions of the wheel must ensure its necessary mechanical strength, as well as ease of casting and further machining.
The material for the impellers is selected taking into account its corrosion resistance to the influence of the pumped liquid. In most cases, pump impellers are made of cast iron. The wheels of large pumps, which can withstand heavy mechanical loads, are made of steel. In cases where these pumps are designed to pump non-aggressive liquids, carbon steel is used to make the wheels. Pumps designed for pumping liquids with a high content of abrasive substances (pulps, sludge, etc.) use impellers made of manganese steel of increased hardness. In addition, in order to increase durability, the impellers of such pumps are sometimes equipped with replaceable protective discs made of abrasion-resistant materials.
The impellers of pumps intended for pumping aggressive liquids are made of bronze, acid-resistant cast iron, of stainless steel, ceramics and various plastics.
The pump housing combines components and parts that serve to supply fluid to the impeller and discharge it into the pressure pipeline. Bearings, seals and other pump parts are mounted on the housing.

The pump housing can be with an end or axial connector. In pumps with an end connector of the housing (Fig. 2.3), the plane of the connector is perpendicular to the axis of the pump, and in pumps with an axial connector (Fig. 2.4) it passes through the axis of the pump.
The pump housing includes inlet and outlet devices.
The doweling device (supply) - the section of the flow cavity of the pump from the inlet pipe to the entrance to the impeller - is designed to ensure the supply of liquid to the suction area of ​​the pump with the least hydraulic losses, as well as to uniformly distribute liquid velocities over the live cross-section of the suction opening.
Structurally, pumps are made with an axial (Fig. 2.5, a), lateral in the form of an elbow (Fig. 2.5, b), lateral annular (Fig. 2.5, c) and lateral semi-spiral (Fig. 2.5, d) inlet.
The axial inlet is characterized by the lowest hydraulic losses, however, when manufacturing pumps with such an inlet, the dimensions of the pumps in the axial direction increase, which is not always convenient structurally. The lateral annular inlet creates the greatest hydraulic losses, but ensures compactness of the pump and convenient mutual arrangement suction and pressure pipes.

In double-entry pumps, the impellers are unloaded from the axial pressure that occurs during pump operation. These pumps usually use a side semi-spiral inlet, which ensures uniform flow of liquid into the impeller.
A diverter device (discharge) is a section designed to drain fluid from the impeller into the pump discharge pipe. Liquid leaves the impeller at high speed. In this case, the flow has high kinetic energy, and the movement of the liquid is accompanied by large hydraulic losses. To reduce the speed of fluid leaving the impeller, convert kinetic energy In the potential (increasing pressure) and reducing hydraulic resistance, diverting devices, as well as guide devices, are used.

Rice. 2.6. Bend diagrams for centrifugal pumps

There are spiral, semi-spiral, two-helix and annular bends, as well as bends with guide devices.
A spiral outlet is a channel in the pump housing that surrounds the impeller around the circumference (Fig. 2.6, a). Cross section this channel increases according to the flow rate of liquid entering it from the impeller, and average speed the movement of fluid in it decreases as it approaches the outlet or remains approximately constant. The spiral channel ends in an output diffuser, in which a further decrease in speed occurs and the kinetic energy of the liquid is converted into potential energy.
An annular outlet is a channel of constant cross-section that covers the impeller in the same way as a spiral outlet (see Fig. 2.6,6). An annular outlet is usually used in pumps intended for pumping contaminated liquids. Hydraulic losses in annular bends are much greater than in spiral ones.
A half-spiral outlet is an annular channel that turns into a spiral, expanding outlet.
The guide vane (see Fig. 2.6, c) consists of two annular disks, between which guide blades are placed, bent in the direction opposite to the direction of bending of the impeller blades. Guide vanes - more than complex devices than spiral bends, the hydraulic losses in them are greater and therefore they are used only in some designs of multistage pumps.
In large pumps, compound bends are sometimes used (see Fig. 2.6, d), which are a combination of a guide vane and a spiral bend.
The pump shaft serves to transmit rotation from the pump motor to the impeller. The wheels are secured to the shaft using keys and lug nuts. Forged steels are most often used to make shafts.
The bearings in which the pump shaft rotates are either ball bearings or sliding friction bearings with liners. Ball bearings are used, as a rule, in horizontal pumps. Some large pump bearing designs incorporate cooling and forced circulation oils Based on the location of the bearing supports, a distinction is made between pumps with outrigger supports, isolated from the pumped liquid, and pumps with internal supports, in which the bearings are in contact with the pumped liquid.
Oil seals serve to seal the holes in the pump housing through which the shaft passes. The seal located on the discharge side should prevent water from leaking from the pump, and the seal located on the suction side should prevent air from entering the pump.

Working wheel

In the “General” section we will consider impellers for pumps or impellers, as they are often called. – is the main working part of the pump. The purpose of the impeller is that it converts the rotational energy received from the engine into the energy of fluid flow. Due to the rotation of the impeller, the liquid in it also rotates and is acted upon by centrifugal force. This force causes fluid to move from the central part of the impeller to its periphery. As a result of this movement, a vacuum is created in the central part of the impeller. This vacuum creates the effect of liquid being sucked into the central hole of the impeller directly through the suction pipe of the pump.

The liquid, reaching the periphery of the impeller, is released under pressure into the discharge pipe of the pump. The outer and inner diameters, the shape of the blades and the width of the working gap of the wheel are determined using calculations. Impellers can be different types radial, diagonal, axial, as well as open, semi-closed and closed. The impellers in most pumps have a three-dimensional design that combines the advantages of radial and axial impellers.

Impeller types

The design of the impeller is open, semi-closed and closed. Their types are shown in (Fig. 1).

Open (Fig. 1a) the wheel consists of one disk and blades located on its surface. The number of blades in such impellers is most often either four or six. They are very often used where low pressure is required and the working environment is contaminated or contains oily and solid inclusions. This wheel design is convenient for cleaning its channels. Efficiency The open wheels are small and amount to approximately 40%. Along with the indicated disadvantage open impellers have significant advantages; they are less susceptible to clogging and are easy to clean from dirt and deposits in the event of clogging. And further, this design The wheels are characterized by high wear resistance to abrasive components of the pumped medium (sand).

Semi-closed (Fig. 1b) The wheel differs from a closed one in that it does not have a second disk, and the wheel blades, with a small gap, adjoin directly to the pump housing, which acts as a second disk. Semi-closed wheels are used in pumps intended for pumping heavily contaminated liquids (sludge or sludge).

Closed(Fig. 1c) the wheel consists of two disks, between which the blades are located. This type of wheel is most often used in centrifugal pumps, as they create good pressure and have minimal fluid leakage from the outlet to the inlet. Closed wheels are made in various ways: casting, spot welding, riveting or stamping. The number of blades in the wheel affects the efficiency of the pump as a whole. In addition, the number of blades also affects the steepness performance characteristics. The more blades, the less pulsation of fluid pressure at the outlet of the pump. Exist various ways landing the wheels on the pump shaft.

Types of impeller landings

The seat of the impeller on the motor shaft in single-wheel pumps can be conical or cylindrical. If you look at the seat of impellers in multi-stage vertical or horizontal pumps, as well as pumps for wells, then the seat can be either cross-shaped, or in the form of a hexagon, or in the form of a hexagonal star. (Fig. 2) shows impellers with various types landing

Conical (conical) fit (Fig. 2a). Conical fit provides simple landing and removal of the impeller. The disadvantages of this fit include the less precise position of the impeller relative to the pump housing in the longitudinal direction than with a cylindrical fit. The impeller is firmly seated on the shaft, and it cannot be moved on the shaft. It should also be said that the conical fit generally causes large wheel runouts, which negatively affects the mechanical seals and stuffing box packings.

Cylindrical fit (Fig. 2b). This fit ensures the exact position of the impeller on the shaft. The impeller is fixed to the shaft by one or more keys. This landing is used in, and. This connection has an advantage over a conical connection due to a more precise position of the impeller on the shaft. The disadvantages of a cylindrical fit include the need for precise machining of both the pump shaft and the hole itself in the wheel hub.

Cross-shaped or hexagonal fit (Fig. 2c and 2e). These types of plantings are most often used in. This fit allows for easy installation and removal of the impeller from the pump shaft. It rigidly fixes the wheel on the shaft in the axis of its rotation. The gaps in the impellers and diffusers are adjusted using special washers.

Hex star fit(Fig 2d). This fit is used in and where the impellers are made of stainless steel. This is the most complex design seat, requiring very high class processing of both the shaft itself and the impeller. It rigidly fixes the wheel in the axis of rotation of the shaft. The gaps in the impellers and diffusers are adjusted using bushings.

There are other types of impeller mountings on the pump shaft, but we did not set ourselves the goal of disassembling everything existing methods. This chapter discusses the types of impellers most commonly used.

Operation, maintenance and repair

As is known, impeller or impeller is the main element of the pump. The impeller determines the main specifications and pump parameters. The service life and use of pumps largely depends on the service life of the impellers. The service life of the impeller is influenced by many factors, the most significant of which are the quality of the installation performed and the operating conditions of the equipment.

Installation quality. It seemed that this was complicated, I connected a pipe or hose to the suction and pressure pipes, filled the pump and suction pipe with water, plugged the plug into the socket and everything was fine. The pump began to supply water and now you can reap the fruits of your labor. It seems so at first glance, but in reality everything is much more complicated. The service life of the equipment and its operating conditions greatly depend on the quality of the installation. The most common installation mistakes:

• connecting a pipe of smaller diameter than the pump inlet. This leads to an increase in resistance in the suction line and, accordingly, leads to a decrease in the suction depth of the pump and its performance. Manufacturing plants pumping equipment It is recommended to increase the diameter of the suction line by one standard size when the suction depth is over 5 meters. Truncating the diameter of the suction pipe also leads to a loss of pump performance. A truncated suction pipeline is not able to pass the volume of liquid that the pump can deliver. If a hose is connected to the suction pipe of the pump, it must be corrugated and of a suitable diameter; It is strictly prohibited to connect simple hoses to the suction pipeline. In this case, due to the vacuum created by the impeller at the suction, the hose is compressed and the suction line is truncated. The pump will supply water poorly at best, and at worst not at all;
• absence check valve with a mesh on the suction line. In the absence of a check valve, after turning off the pump, water may flow back into the well or borehole. This problem is relevant for pumps in which the suction pipe is located below the suction axis of the pump, or for pumps in which the suction pipe is under pressure when it stops. The suction axis of the pump is the center of the suction pipe;
• sagging of the pipe in a horizontal section or counter slope from the pump in the suction pipeline. This problem leads to “airing” of the suction pipeline and, accordingly, to a loss of pump performance or to a complete cessation of its operation;
• a large number of turns and bends in the suction. Such installation also leads to an increase in resistance in the suction pipeline and, accordingly, to a decrease in the suction depth and pump performance;
• poor tightness in the suction pipe. In this situation, air leaks into the pump, which affects the suction ability of the pump and its performance. The presence of air also leads to increased noise during equipment operation.

Equipment operating conditions. This factor includes operation of equipment in cavitation mode and operation without fluid flow “dry running”

• Cavitation. In cavitation mode, the pump operates when there is a lack of water at its inlet. This mode of operation of the equipment depends entirely on the correct installation. If there is a lack of water at the pump inlet due to the vacuum created by the impeller, in the zone of transition from low to high pressure, the so-called “cold boiling of liquid” occurs on the surfaces of the impeller. In this zone, air bubbles begin to collapse. Due to these numerous microscopic explosions in areas with more high pressure(e.g. at the periphery of the impeller) microscopic explosions cause pressure surges that damage or may even destroy hydraulic system. The main symptom of cavitation is, increased noise during pump operation and gradual erosion of the impeller. In (Fig. 3) you can see what the brass impeller has become when it was operated in cavitation mode.

• NPSH. This characteristic determines the minimum additional value of the inlet pressure in a particular type of pump necessary for its operation without cavitation. The NPSH value depends on the type of impeller, the type of liquid being pumped, and the speed of the motor. The value of the minimum backwater is influenced by external factors, such as the temperature of the pumped liquid and atmospheric pressure.
• Operation without fluid flow “dry running”. This operating mode can occur both in the absence of pumped liquid at the pump inlet, and when the equipment is operating with a closed valve or tap. When operating without fluid flow, due to friction and lack of cooling, the fluid quickly heats up and boils in the working chamber of the pump. Heating first leads to deformation of the working elements of the pump (Venturi tube, diffuser(s) and impeller(s)), and then to their complete destruction. In (Fig. 4) you can see the deformation of the impellers when operating pumping equipment in the “dry running” mode

Consequences of the “Dry Run”

To eliminate such situations, it is necessary to prevent such cases and install additional protection against equipment operation in “dry running” mode. You can learn about some protection methods . It is also necessary to carry out periodic inspection and maintenance of equipment to increase its service life. During the inspection, you need to pay attention to air leaks (suction pipeline) and the absence of leaks in the connections and mechanical seal. This is especially true in cases where pumping equipment has been idle and not in use for a long period of time. If problems are detected, you must fix them yourself or invite a specialist from service center, if, for example, there is a need for replacement. Repairs in such cases will not be long or expensive. Much more difficult and more expensive repairs worth it when you need to change all the insides of the pump and, in addition, also rewind the stator. Repair in this case can cost approximately the same as a new pump. Therefore, if deviations in the operation of the equipment are detected (pressure and flow have decreased, noise has appeared during operation), it is necessary to carefully examine and inspect the entire system yourself and eliminate the problems. It should be added that when repairing pumping equipment, very often when replacing the impeller, you may encounter the following problem: how to remove it? This is true for pumps that have a brass or noril impeller, but with a brass insert, or cast iron with a cylindrical fit under a key. During operation, such wheels “stick” to the shaft. The quality of our water also contributes to this, with a high content of hardness salts or iron. It is very difficult to remove such wheels from the shaft without damaging anything. To remove wheels, you must first clean them of scale and hardness salt deposits using the household product “SANTRI” or something similar. This product perfectly cleans the insides of the pump from deposits of hardness salts. If the impeller cannot be removed after cleaning, you should use a “WD” product that is used in car repairs or any liquid lubricant that you have on hand. Due to its high fluidity, “WD” liquid penetrates deeply into all voids and pores, thereby wetting and lubricating working surfaces. Then, using a bushing (the bushing should have a diameter of 3-5 mm larger than the diameter of the shaft, but not extend beyond the brass insert, this is important for plastic impellers) and a hammer, try to move the impeller from its seat. You also need to pay attention to the shaft itself, so as not to damage the thread onto which the nut securing the impeller is screwed. To do this, we put the bushing on the motor shaft and hit it with a hammer. You need to hit with such force as not to damage the mechanical mechanical seal, which is located on the shaft, immediately behind the impeller. As you know, the moving part of a mechanical mechanical seal has a spring that constantly presses the working surfaces of the moving and stationary parts of the mechanical seal against each other. By compressing this spring, we can move the impeller by 1-2 mm. along the motor shaft. Then we need to move the impeller along the shaft in the other direction. To do this, you will need two slotted powerful screwdrivers. Screwdrivers are inserted between the engine support (caliper) and the impeller opposite each other, always under the partitions of the blades (so as not to break the blades of the plastic impeller). We prop up the impeller and try to move it along the shaft in reverse side. Then we take a hammer, a bushing and carry out the procedure described above. There may be several such attempts until the impeller is removed. Brass and cast iron impellers had to be removed in the same way. At correct installation and compliance with operating conditionsimpeller or impeller, like the pump itself, can last long and reliably for many years.

Thank you for your attention.

The impeller of a centrifugal pump is the main part of the device. This is an element that converts rotational energy into pressure in the housing where the liquid is pumped.
What is the role of the impeller in a centrifugal pump, how to correctly calculate it and replace it in a device with your own hands, this article suggests that you get acquainted with it.

How does a centrifugal pump work?

Inside the spiral-shaped pump housing, an impeller consisting of two disks is rigidly attached to the shaft:

• Rear.
• Front.
• Blades, between the discs.

The blades are bent from the radial direction in the direction opposite to the rotation of the wheel. The pump housing is connected to the pressure and suction pipelines using pipes.
When the pump body is completely filled with liquid from the suction pipeline, when the impeller rotates from the electric motor, the liquid located between the blades, in the channels of the impeller, from the center, under the influence of centrifugal force on it, is thrown to the periphery. In this case, a vacuum is created in the central part of the wheel, and the pressure increases at the periphery.
As the pressure increases, liquid will begin to flow from the pump into the pressure pipeline. This will cause a vacuum to form inside the housing.
Under its action, the liquid will simultaneously flow from the suction pipeline into the pump. In this way, liquid is continuously supplied to the pressure pipe from the suction pipe.
Centrifugal pumps are:

• Single-stage, which has one impeller.
• Multistage, have several impellers.

In this case, the operating principle is the same in all cases. The liquid, under the influence of centrifugal force on it, developing due to the rotating impeller, begins to move.

How are centrifugal pumps classified?

Instructions for classifying centrifugal pumps include:

• Number of stages or impellers:

1. single stage pumps;
2. multi-stage, with several wheels.

• Location of the wheel axle in space:

1. horizontal;
2. vertical.

• Pressure:

1. low pressure, up to 0.2 MPa;
2. average, from 0.2 to 0.6 MPa;
3. high, more than 0.6 MPa.

• Method of supplying fluid to the working element:

1. with one-way entrance;
2. double-entry or double suction;
3. closed;
4. half-closed.

• Housing connector method:

1. horizontal;
2. vertical connector.

• Method of draining liquid from working area into the housing channel:

1. spiral. Here the liquid is immediately drained into the spiral channel;
2. scapular In this case, the liquid first passes through a special device, which is called a guide vane and is a stationary wheel with blades.

• Speed ​​factor:

1. low speed pumps;
2. normal;
3. high-speed.

• Functional purpose:

1. for water pipes;
2. sewerage;
3. alkaline;
4. oil;
5. thermoregulating and many others.

• Motor connection method:

1. driven, the system contains a gearbox or pulley;
2. connection to the electric motor using a coupling.

• Pump efficiency.
• The method of positioning the pump in relation to the water surface:

1. superficial;
2. deep;
3. submersible

Features of the device impeller

Tip: Timely replacement of a worn impeller will increase the service life of the centrifugal pump.

The impeller converts the rotational energy of the shaft into pressure, which is created inside the body of the device where the liquid is pumped. Hydrodynamic calculation of the impeller of a centrifugal pump according to specified requirements is carried out to determine the size of the flow or internal and external parts of the impeller, the shape and number of blades.
You can find out in detail how the element is calculated in the video in this article.

The shape of the wheel and its structural dimensions provide the element with the necessary mechanical strength and manufacturability:

• Possibility of obtaining a high-quality casting.
• Ensure continued compliance with the machining process.

When choosing a material, the following requirements must be met:

• Resistant to corrosion.
• Chemical resistance to the elements of the pumped liquid.
• Resistance to the required operating mode of the device.
• Long service life, according to the passport specifications.

Most often, cast iron grades SCh20 - SCh40 are used to make the impeller.
When working with harmful chemicals and corrosive environments, the impeller and housing of the centrifugal pump are made of stainless steel. For operation of the device in intense conditions, which include: long period of switching on; the pumping liquid contains mechanical impurities; high pressure, for the manufacture of wheels, chromium cast iron is used, as shown in the photo.

How to turn an impeller

During operation, sometimes it is necessary to adapt the characteristics of pumps to specific conditions. In this case, it is best to reduce outside diameter D 2 wheels having trimmed it. (Fig. 1) .

Rice. 1. Schemes for refining the device impeller
a) centrifugal
b) axial
When trimming the working elements of centrifugal pumps, the change in pump parameters can be approximately calculated using similarity equations:

• where Q is the nominal feed;
• H – head;
• N – power;
• D 2 - outer diameter (before trimming the wheel);
• Q', H', N', D' 2 the same designations, after trimming.

In Fig. 2 shows the working dimensions of the wheel after finishing its turning. As you can see, after this process the flow and pressure for pumps of this type significantly expands.

The efficiency is practically not affected by a decrease in diameter from the original by 10...15% for devices with n s = 60...120. With a higher increase in n s, the decrease in efficiency will be significant, as can be seen from Fig. 3.

How the parameters change when trimming an element for axial pumps can be calculated using the formulas:

• where Q is the nominal feed;
• H – head;
• D 2 - outer diameter of the element;
• d—hub diameter (before wheel trimming);
• Q', H', D' 2 - the same designations, after trimming.

The flow rate of an axial pump can also be reduced by replacing the impeller with another one, with the same blades and a larger bushing diameter. In this case, the pressure characteristic of the pump is recalculated using the formulas: where d’ is the larger diameter of the sleeve.
For centrifugal pumps (see

Rice. 5. Scheme of changing the blades of the pump impeller

Tip: When performing such operations, the price of a centrifugal pump will be significantly reduced than when purchasing a new device.

The use of centrifugal pumps in good condition increases their service life, which significantly reduces costs when pumping liquid.

At the client’s request, the Elektrogidromash company will supply spare parts for the pumps own production: X, AH, AHP, ANS 60, ANS 130, S569M, S245. And also to the pumps various types: D, 1D, SDV, SM, SD, TsNS, VK, K, KM, NKU, KS, NK, SM, TsVK, SE, Sh, NMSh, VVN, and many other pumps. In particular, such components as the rotor assembly, impeller, sealing ring, shaft, protective sleeve, guide vane, and pump housing are supplied.

What does installing new spare parts give:

Spare parts for pumps are not only extending the service life of the unit, but also significant savings money. We can give the following example: the efficiency of a pump D 320/50 with a 75 kW electric motor has decreased by 10% over 5 years of operation on a water pipeline. This led to a slight decrease in flow (from 320 to 304 m3/h) and pressure (from 50 to 47.5 m). However, the corresponding losses of electricity turned out to be very significant: over the year they amounted to 65,700 kW/h, i.e. RUB 45,990, which significantly exceeds the cost of a new wheel ( 4600 rub.)