What are single stage pumps. Centrifugal Multistage Pumps for Cottages: Scheme of Operation. Multistage pump device - what the unit consists of

Practical filters reverse osmosis give the owner the opportunity to significantly improve the characteristics and taste of water, regardless of the location of the home and natural conditions terrain. Thanks to a well-thought-out design, which includes a complex of several cartridges with different fillers, they effectively rid the liquid of mechanical impurities such as clay, peat fibers or grains of sand, eliminate salt deposits of heavy metals, chloride compounds and bacteria, organic substances and foreign odors.

For proper operation of the system, the pressure in the water supply system must not fall below 3 atmospheres. This value does not always reach the desired value - for example, in country houses or on the upper floors it may be somewhat lower. In this case, together with the filters, it will be necessary to install a pump capable of increasing the pressure.

Operating principle

The device operates from electrical network, connecting to it using an adapter, which can be supplied in the kit or purchased separately. For operation, the device also needs sensors that signal the level of pressure in the system. When its value falls below the required value, the pump turns on and works until storage tank will not fill with filtered water.

Thus, this easy-to-use device allows you to provide and maintain pressure at the proper level, ensuring the smooth operation of the filtration system and invariably high quality drinking water in the house.

Advantages

The advantages of pumps for reverse osmosis systems include:

the ability to increase pressure to a level of about 8 atmospheres;
ease of installation and use;
economical consumption of electricity;
low noise level during operation;
compact dimensions;
universal design that allows using one pump for filters of different manufacturers.

Centrifugal pumps are widely used both in everyday life and in industry. Depending on the design, they are referred to as multistage or single-stage pumps. Pumping equipment belonging to each of these categories not only has a special internal organization, but also differs in specific technical characteristics and, accordingly, areas of application.

Design differences

The centrifugal pump, which becomes clear from its name, is a device that pumps liquid media due to the centrifugal force acting on them. The main working body of pumping equipment of this type, which ensures the formation of such a force, is a wheel (or drum), on the outer cylindrical surface of which special blades are fixed.

The casing of the pumps of this type can be made of cast iron or steel alloy. Inside such a housing are placed a drive motor and a rotation shaft connected to it, on which a wheel with blades is fixed. According to its design Working wheel pump can be open or closed. Open impellers consist of one disk, on outer surface which the blades are fixed, closed - from two disks interconnected by working blades.

The blades are located at a certain angle, their bend is directed in the direction opposite to the direction of rotation of the impeller. This arrangement of blades provides more efficient work pumping equipment. The suction of the pumped liquid medium into the internal chamber of the pump, as well as its ejection into the pressure line, is carried out through the nozzles.

The principle by which both single-stage devices and multi-stage pumps work is as follows.

The liquid inside the pump before starting it is captured by the blades during the rotation of the impeller and begins to move along with them.
Under the influence of centrifugal force, the liquid is thrown to the walls of the inner chamber, due to which a high pressure is created near them.
When moving through the area of the discharge pipe, the liquid under high pressure is pushed into it.
When the liquid pumped by the pump is thrown back to the walls of the working chamber, a rarefaction of air is created in the central part of the latter, which contributes to the suction of the liquid medium through the inlet pipe.

Due to the above principle of operation in pumps of both single-stage and multi-stage types, the process of suction and expulsion of the pumped liquid is ensured during the rotation of the impeller. The scope of application of pumping equipment of this type is significantly expanded by the fact that, unlike piston devices, it does not create pulsations of fluid pressure in the pipeline system it serves.

As mentioned above, single-stage and multi-stage centrifugal pumps have design features that determine the differences in their technical specifications. So, the main structural elements of a single-stage pump are:

the body, which is often called the "snail";
impeller with blades;
shaft sealing elements;
a shaft connected to a drive motor and providing rotation of the impeller;
sealing elements of the chamber with an oil bath;
support for the bearing unit;
bearing support;
a hole through which the oil level in the chamber is controlled.

A single-stage centrifugal pump, unlike multi-stage models, is equipped with one impeller. Centrifugal multistage pump can be equipped with two or more impellers with blades, which can significantly increase the efficiency of such equipment.

Due to the presence of several impellers, centrifugal multi-stage devices, when compared with single-stage ones, have certain advantages.

With the help of multistage pumps, it is possible to pump liquid with a higher productivity, which characterizes the amount of liquid medium that the hydraulic machine passes through itself per unit time.
Multistage pumps are capable of generating a fluid flow with higher head values, measured in meters of water column. In fact, the pressure of the liquid, which is created by electric pumps of a multistage type, is the sum of the pressures created by each of its stages. This quality of multistage hydraulic machines allows to achieve a higher fluid pressure in the pipeline systems they serve and move it through them over longer distances and greater heights.

A multistage centrifugal pump, depending on its design, can be sectional or scroll. In sectional-type devices, the liquid medium in the process of pumping moves sequentially from the first section of the pump to the last, while the pressure of the liquid also increases sequentially. Modern models multistage pumps of the sectional type are capable of providing the capacity of the liquid pumping process, the value of which reaches 900 m 3, while the pressure of the working medium created by such devices can reach up to 1900 meters of water column.

Advantages and disadvantages of centrifugal pumps

Both multistage and single-stage pumps have a number of advantages that make these devices so popular among consumers. The advantages of the considered hydraulic machines include:

compact dimensions and low weight (since the working shaft of the pumping equipment is directly connected to the drive motor, which eliminates the need for additional transmission mechanisms);
high reliability and long service life, no need for regular maintenance Maintenance;
minimizing the risk of pressure surges (the liquid medium pumped by pumps of this type is supplied to the pressure line in a smooth mode);
lack of valve elements (this makes it possible to pump contaminated liquid media containing insoluble solids in their composition);
simplicity of design (which is why any multi-stage or single-stage pump is affordable).

Among the disadvantages of single- and multi-stage pumps are:

rather low efficiency when operating in low productivity mode (this becomes a problem when it is required to pump a small volume of liquid medium under high pressure);
the impossibility of a quick start (in order for such devices to start working, their working chamber must first be filled with liquid).

Grounds for classification

Centrifugal pumps (both multi-stage and single-stage) are divided into various categories according to a number of their parameters and design options. So, depending on the spatial position of the axis of the working shaft, they can be one of the following types:

horizontal centrifugal pumps;
devices with a vertical arrangement of the working axis.

A centrifugal horizontal pump, the axis of rotation of the shaft and the impeller of which are located strictly in a horizontal plane, is, as a rule, a large-sized installation used for industrial purposes. Centrifugal horizontal pumps used to equip pumping stations that ensure the operation of autonomous water supply systems in which such devices are used in conjunction with a hydraulic accumulator. Thus, a horizontal pump requires more space for its installation.

Centrifugal pumps with a vertical shaft axis and impeller are more common in the household sector. In such a design, it can be represented as a surface multistage pump used to service an autonomous water supply system, as well as a drainage or fecal pump.

Another criterion by which different categories are distinguished among single- and multi-stage pumps is the location of such equipment in relation to the liquid medium being pumped. So, depending on this parameter, pumps can be surface (or ground), submersible and semi-submersible. Surface devices, which can be a vertical multi-stage and single-stage or horizontal multi-stage and single-stage pump, are located on the surface of the earth, outside the well, but close to it.

Place such equipment, reliably protected from moisture, in a pit, on a specially prepared site or in separate room. One of the most significant drawbacks of this type of pumping equipment is that it makes a lot of noise during operation. It should also be borne in mind that surface centrifugal pumps can only be selected if the depth of the well from which it is planned to pump water with their help does not exceed ten meters.

Submersible centrifugal pumps are completely immersed in the pumped medium during operation. Some models of vertical submersible centrifugal pumps can even be placed in a pipe through which a liquid medium is pumped out. Using submersible pumps water from a serviced well can be lifted from a depth of 40 meters or more. Submersible pumps are capable of pumping a liquid medium with a capacity of up to 16 m 3 / hour, while its pressure can reach 200 meters of water column. Submersible pumps make almost no noise during their operation, since they are completely in a liquid medium.

Centrifugal pumps are called dynamic hydraulic machines. The functional task of such equipment is to pump liquid, which is carried out if the kinetic energy of rotation is converted into hydrodynamic energy of the flow. To rotate the pump shaft, an electric motor or internal combustion engine is provided. The liquid reaches the impeller, which has vanes on the casing, which are necessary to act on the particles of the liquid and transfer that energy.

Centrifugal forces act in such a way that the liquid is directed towards the periphery of the impeller. In this area, through a special annular channel, which is also called a cochlea, the liquid is supplied to the pressure pipe, that is, the diffuser. And already the task of this element is to convert part of the dynamic energy into static.

A multistage centrifugal pump is a more advanced equipment, the device of which involves several impellers and stages located one behind the other. When choosing a centrifugal pump, you should pay attention to how the shaft is sealed. Modern models feature mechanical seals, while older models have stuffing box packing. The first configuration is good because it keeps the structure tight and prevents leaks. Even if the pump works with vibrations or its shaft is slightly displaced, this will not cause leakage.

On the this moment There are a considerable number of pumps for pumping liquid and the most common of them are centrifugal. They differ in their design features and are single or multi-stage.

Multistage pump and its scheme

Centrifugal equipment is assembled from elements such as a discharge pipe, guide vane, wheels and a spiral outlet.

When the wheels begin to rotate, the part that has special bends on the blades is filled with liquid.

It must be understood that there are many models of such pumps that differ from each other in the assembly design - how the shaft is located, what shape the pipes are and how many impellers are installed. When choosing, you should also build on the power and dimensions of the equipment.

Design features

Single-stage equipment is equipped with one impeller, while a multi-stage pump is expected to have two or more. As for the principle of operation, it is identical, the number of wheels is directly related to the performance of the unit. Thus, multistage pumps are able to pump more water in a certain time, and also have an increased pressure, that is, the liquid can be pumped over long distances, compared to a single-stage pump.

Multistage centrifugal pumps also have different design and are sectional or spiral. As for the sectional, it pumps the liquid sequentially, that is, from one drum to another. The maximum performance level of the described equipment is 900 cubic meters water per hour with a head of 1900 meters.

Strengths and weaknesses of centrifugal units

Such pump equipment, involving centrifugal force is now in great demand. The reason for this is the various operational advantages that we highlight below:

since the rotation shaft is directly connected to the motor, the pumping equipment is compact and light in weight. The design itself does not provide for transmission mechanisms;
reliable and durable device that does not require regular maintenance;
since the working medium is supplied as smoothly as possible, this guarantees the absence of water hammer in the system;
the pump may use a contaminated liquid, which contains mechanical particles. This is due to the fact that the design of the device does not imply the presence of valves;
again, max. simple design pump allows you to distribute it at an affordable cost;
simple operation, which even a beginner can handle.

Even an unprepared user can understand the scheme of a multistage pump. These devices serve the purpose of pumping liquid, but they can also work with other compounds, as long as they are not chemically aggressive.

There are also negative sides, one of which is low efficiency if the low performance mode is activated. A similar problem becomes critical if it is necessary to pump a small volume of water under high pressure.

In addition, it will not be possible to quickly put the pump into operation, since before starting to pump liquid, water must be introduced into the device body.

If you do not pay attention to these shortcomings, then if you need really productive work - centrifugal pumps are considered the best equipment for these purposes.

Types of multistage pumps

Based on the position of the equipment piston, the device can be:

horizontal. Allows you to increase the pressure of the water supply, so it is popular for use in apartments and country houses. If it's necessary autonomous water supply, such pumps also successfully cope with the task. Often, such equipment involves surface work, that is, they do not need to be immersed in a liquid to function. Thus, a multistage centrifugal pump allows you to: speed up the filling of the pool or organize an irrigation system on the site;
vertical. Such a well is best suited if the site has a well located near the house. The pump effectively pumps water from a depth of about 20 meters, which is enough for many users.

The main components of a multistage pump

frame. Its task is to ensure the tightness of the structure and its fixation;
the rotor is the basis of the entire unit. Since high technology is accumulated, this element is distinguished by reliability and performance. Design features allow the device to interact with various liquids;
balancing disc. Allows you to reduce the load to the optimum, as a result of which the service life of the bearings is extended;
main shaft. Provides shaft stability in one place, which, in turn, increases the service life of seals and bearings;
seals;
deflectors. Provide a guaranteed volume of oil in the bearing assembly, and also protect it from mechanical particles;
impellers and impellers. Minimize shaft vibrations and make its movements balanced.

A huge variety of pumping units used both in everyday life and in industry makes designers come up with more and more advanced models, increasing performance.

About how multistage pumps for water can be useful to you, we will consider in this article.

Design features

Depending on the design and number of impellers, pumps are divided into single-stage pumps - with one impeller and multi-stage - with two or more impellers.

The principle of operation of a multistage pump does not change: in the area of the fluid inlet into the suction cavity, a rarefaction area is formed, at the outlet of the pump in the guide vane, an injection area is formed. Due to the pressure difference, the centrifugal pump moves the medium through the pipes.

Differences between single-wheel and multi-wheel pumps in terms of performance change only in terms of delivery. The flow of multi-wheel pumps is equal to the sum of the feeds of each of the wheels, i.e. the feed increases as many times as the wheels are mounted on the shaft.

The principle and scheme of operation of a multistage pump

The pressure created by the wheel of a centrifugal machine is determined by the product U * C, where U is the peripheral speed of the fluid in the wheel, C is the absolute speed, or the speed of the fluid relative to the fixed body.

In order to achieve a high head in a pump with one impeller, it is necessary to have a high circumferential speed.

But the circumferential speed is limited by the strength of the wheels and cavitation.

The speed U for cast iron wheels is limited by strength to 40 m/s, for steel wheels - about 300 m/s.

In special designs of transport superchargers for high-strength light alloy wheels, circumferential speeds of more than 500 m/s are allowed.

In pumps that supply water and technical fluids, the rotation speed, and hence the pressure, are limited by the conditions for the occurrence of cavitation.

A multistage centrifugal pump is a series of single-stage units, the impellers of which are located on a common shaft and connected in series.

When the wheels are turned on in series, the pressures created by them add up so that the total pressure of the machine is equal to the sum of the pressures of the individual stages.

In most cases, when supplying incompressible liquids, the geometric dimensions of all stages are the same and therefore the total head of such a machine is equal to the head of one stage multiplied by the number of stages of the machine.

The fluid flow enters through the inlet chamber 1 into the impeller 2 of the first stage of the machine, from where, having received a certain amount of energy from the impeller blades, it is ejected into the guide vane 3 of this stage.

From the second stage, the flow is directed to the third, and so on.

Reverse guide vane

The reverse guide vane is a characteristic element of a multi-stage centrifugal machine.

When leaving the guide vane of the first stage, the fluid flow has a significant absolute velocity, i.e. it is twisted about the center of the machine. If such a flow is brought to the blades of the impeller of the second stage, then it will receive another increment of energy.

If a vane guide device is placed on the path between the outlet of the first stage guide vane and the entrance to the second stage impeller, then it will work as efficiently as the first stage impeller.

The purpose of the reverse guide vane is to provide optimal flow swirling in order to efficiently transfer energy to the flow in the next stage of the pump.

The pressures created by modern centrifugal multistage pumps reach 400 meters of water column. Pumps with up to 30 stages are available.

Horizontal and vertical multistage pump

Depending on the purpose and field of application, the design of a multistage centrifugal pump can be of the following types.

- as the name implies, these pumps are installed vertically. Due to the design, they create a very high pressure with moderate flow. The main area of application in Everyday life- This is the provision of water supply from a well or well.

The vertical multistage centrifugal pump is used for well maintenance, besides, this design is used in the manufacture of drainage and sewage pumps.

Vertical multistage submersible pumps are used to supply water from wells (borehole pumps). During operation, they are completely immersed in water. Some models can even be placed in a pipe through which fluid moves.

Modern designs of multistage submersible pumps are capable of lifting water to a height of up to 100 at a flow rate of up to 50 cubic meters per hour.

Horizontal multistage pumps- starting from the name, we come to the conclusion that such a unit is mounted horizontally. This type of design also allows you to increase the pressure as many times as it has steps. All wheels of the horizontal multistage pump are mounted on common shaft and form a single rotor.

Centrifugal horizontal pumps are used when equipping pumping stations and where a large pressure is required at a flow determined by the technical project.

Sectional multistage pumps

In the case when a centrifugal machine at a given pressure must provide such a flow that the dimensions of the flow path are structurally unacceptable, a parallel connection of the impellers is used.

At high pressures and high feeds, centrifugal machines of a multi-flow type with pressure stages are used. Such machines consist of two or four groups of pressure stages. Such pumps are called sectional multistage pumps.

In each group, the steps are connected in series to increase the pressure, and the groups of steps are connected in parallel. As an example of the connection of stages and groups in a mixed type centrifugal machine, a diagram of the operation of a three-stage two-flow machine with a symmetrical arrangement of stages and their groups is given.

Video about multistage pumps

A very big advantage of a multistage pump is that the thrust balancing system, bearings and seals are combined in one common housing for all stages, which makes the pump compact, reduces weight and reduces cost.