How was all this created?

Already in ancient times, from the very beginning of using water to deliver it to homes, irrigate fields, supply water to urban structures, fill defensive ditches around cities and castles, people searched for technical capabilities lifting and transporting water.

To collect water from a source and bring it to a dwelling, a person had to use large leaves of plants, and when water became scarce, he “invented” a ladle, which was the first step towards the invention of a jug. Time passed, the shapes of the jugs changed, their volume increased and design features. The jug "acquired" handles, a flat or curved bottom. But gradually, a person began to realize that the transportation of water takes him a huge amount of time and effort. Thus was born the idea of ​​using not one jar, but several (and quite simple ones) that would be hung on a chain or wheel. This device was powered by either human or animal efforts. At the same time, the volume of water supply and the rate of its supply depended both on the volume of jugs used in the mechanism and on the speed of movement of this mechanism. The volume and speed of water supply was limited by the force that had to be created to move both the scoop wheel itself and to lift the jugs. Archaeological finds prove the existence of such bucket mechanisms in Egypt and China as early as the 10th century BC. The figure shows a schematic design of a Chinese scoop wheel. It's about about the wheel, to which clay pots are attached, the filling of which occurs when the wheel moves inside the water source, and emptying at the highest point of the rise. At the same time, water fell into the tray, through which it flowed by gravity to the places of its use.

Limitations on the volume and speed of water supply, arising from the use of muscular strength, led to the fact that a person began to look for alternative sources energy to rotate the scoop wheel. This is how “water supply installations” appeared, using the movement of air (windmills) or the movement of water as a lifting force. This solution made it possible to pump huge amounts of water (at that time), while spending minimal money, because. neither the wind nor the course of the river required food, shelter or any other conditions of existence. And yet, a huge part of the water was lost only at the stage of its rise in the scoop wheel. These water losses were associated with the insufficient strength of earthenware jugs and their incomplete filling due to "jamming", as well as due to the fact that the fastening of the jugs and the process of filling/emptying them required rotation of the jugs around their own axis. The latter circumstance extremely limited the number of jugs located on the scoop wheel.

A breakthrough in the design of the scoop wheel occurred only in the Middle Ages, in 1724, when J. Leipold proposed to reinforce curved tubes instead of scoop wheel jugs. When the wheel rotated, the water rose to its middle axis. This lifting device is also driven by the flow of the river. In this design, the shape of the curved tubes is striking. They bear a striking resemblance to the channels of a modern pump impeller.

And yet the founder of all modern pumps should be considered the greatest scientist and mathematician Ancient Greece Archimedes, who back in 250 BC. described a screw named after him. Water rose to the top due to the rotation of the screw in the pipe or tank. But since reliable seals and methods for centering the screw itself in the pipe were not yet known at that time, a sufficiently large amount of water flowed back along the pipe walls. And yet, by changing the angle of the screw, our ancestors achieved amazing success. Screw pumps already at that time were designed in such a way that during their operation it was possible to choose the optimum between the maximum amount of pumped water and maximum pressure. According to various historical sources, it is established that the screw pumps of that time were used with the blade angle of 37° and 45° (compare modern pumps). This achieved a head of 2 m to 6 m, and the maximum flow was approximately 10 m 3 /h.

The research of our ancestors helped to establish a certain relationship between the inclination of the propeller and the power of the pump: "The greater the angle of inclination of the pump blades, the greater the pressure is achieved with a decrease in the volume of pumped water." And again, there is a striking resemblance to a modern centrifugal pump in its manufacture and operation.

Structurally, modern pumps are not much different from those used by our ancestors. Of course, modern construction materials, stuffing box and screw seals have appeared, the drive mechanism has changed, etc. And yet, neither the screw nor the angle of inclination of its blades have undergone any changes ... As before, when designing pumps, we focus on the ratio of head and volume of pumped environment (so-called operating characteristic pump). As before, when designing pumps, we determine what angle of inclination of the blades is best to use in a particular case, i.e. what is more preferable for us - the pressure or the volume of the pumped medium, and so on and so forth ...

What are the main types of pumps currently in existence?

Currently, pumps play a huge role in the engineering design of various technological processes. They perform all sorts of functions: from the usual "pumping" of water from tank to tank or sewer water into the drainage, ending with the supply to the processes of obtaining ultrapure water. Not a single house, not a single production, not a single technological process can do without the existence of pumps.

The main characteristics of the operation of any pump are performance, head and suction height.

First of all, it is necessary to list those pumps that are the most "popular" in water supply systems, as well as the main "pluses" and "minuses", which under certain circumstances can be the main "criteria" when selecting a pump:

Piston pumps, which, oddly enough, are the most common type of pump currently used in domestic and industrial applications. The principle of operation of this type of pump is based on the reciprocating movement of one solid cylinder (piston) inside another hollow cylinder (body), as a result of which a rarefaction / injection effect is created inside the second cylinder. Depending on the position of the full-bodied cylinder (piston), either a vacuum pressure (suction process) or discharge pressure (creation of pressure in the pressure line) is created in the pump chamber (casing). The process is controlled by a system of suction and discharge valves. Piston pumps can be single, double acting, and have direct or indirect drive. A separate type of piston pumps should be distinguished - piston pumps of the diaphragm (membrane) type, in which the contact between the pumped medium and the piston occurs through an elastic membrane (diaphragm). The latest series of piston pumps include both ordinary household pumps of the Malysh and Rucheyok brands, as well as metering diaphragm pumps from such well-known companies as TEKNA, EMEC, Prominet, etc.

The main advantages of using piston pumps are:

• high accuracy of pumped liquid supply;
• high efficiency;
• low dependence of pump performance with increasing pressure;
• no decrease in efficiency at ultra-low costs;
• compactness;
• simplicity of device and operation.

The main disadvantages of using piston pumps are:

• uneven supply of the pumped liquid;
• the impossibility of pumping large volumes of liquid;
• the impossibility of pumping contaminated liquids (up to particles with a size of 10 mm).

Based on this, the main areas of application of piston pumps were determined. This is:

• water supply for domestic needs from wells, open reservoirs, etc.
• accurate dosing of either water or any components in water treatment systems;
• pressure increase in water supply systems.

The selection of piston pumps and the conditions for their use must be carefully coordinated either with manufacturers or with designers of water supply systems and water treatment plants.

Centrifugal pumps, the principle of operation of which is based on the rotation of the notorious "Archimedes screw" inside the injection chamber (body). The process of liquid transfer is controlled by a system of suction and discharge valves. This type of pumps includes both conventional circulation pumps and multistage high-pressure pumps, which have not one, but several (up to 15) stages of liquid pressure increase in the discharge chamber. When describing centrifugal pumps, a very significant detail must be mentioned. These pumps cannot run dry. Therefore, when designing water supply systems, it is necessary to take into account both the suction conditions and the discharge conditions of centrifugal pumps.

The scope of this type of pumps is very large. They primarily depend on the properties, conditions and source of the pumped medium. And yet ... We will try to list at least some of them. This is:

• water supply from artesian wells, wells, etc.;
• pumping of drainage and sewer drains;
• pressure increase in water supply systems;
• water circulation in closed systems (hot water supply, cooling, ultrapure water circuits, etc.).

The selection of centrifugal pumps and the conditions for their use must be carefully coordinated either with manufacturers or with designers of water supply systems and water treatment plants.

The main advantages of using centrifugal pumps are:

• uniform supply of the pumped liquid (at a certain pressure);
• the ability to pump large volumes of liquid;
• the possibility of pumping contaminated liquids (up to particles with a size of 10 mm);
• compactness;
• the growth of the device and operation;

The main disadvantages of using centrifugal pumps are:

• lower efficiency (compared to piston pumps);
• the need to install devices that prevent dry running;
• decrease in pump performance with increasing pressure;

a sharp decrease in efficiency at ultra-low costs.

Dosing pumps.

We will continue our further review of pumping technology with a discussion of piston pumps, as the most common in industry. And in particular, we will focus on their varieties - dosing pumps. This choice was not made by chance. It is this type of piston pumps that is most in demand on the market, both domestically and internationally.

The reasons for the popularity of dosing equipment lie in the technological processes of water purification: coagulation, flotation, disinfection, correction of the composition of the treated water, etc. None of these processes can do without adding reagent solutions to the water. An important factor in the treatment of water with chemical reagents is the accuracy of their application. Here, no matter how, by the way, one of the main advantages of piston pumps turned out to be the high accuracy of the pumped liquid supply. The second advantage of using piston pumps for dosing processes is the small working space of the injection chamber, which, as it reduces the loss of chemical reagents (sometimes very expensive) during their dosing, also allows the chamber itself to be made of corrosion-resistant materials that can withstand contact with almost any aggressive medium. And, finally, the third factor that influenced such wide application piston pumps for dosing processes, is the possibility of increasing or decreasing the working space of the discharge chamber by adjusting the length of the piston stroke.

So what tasks are solved with the help of dosing pumps in modern systems water treatment? This is:

• dosing solutions of biocides (oxidizing agents) in the processes of water disinfection;
• dosing of coagulant solutions before clarifying filters;
• dosing of the inhibitor in reverse osmosis plants;
• adjustment of the chemical composition of water in the preparation of various kinds of drinks;
• adjustment of the chemical composition of water in heat and power processes (water for hot water and steam boilers, water for circulating water supply systems, treatment of steam condensate systems, etc.);
• dosing of reagents for disinfection of water in swimming pools and adjustment of its chemical composition.

And this is not the whole list of possible applications of metering pumps, since we have only touched on two industries (food and heat power). In the course of the subsequent discussion of the design features of a particular group of dosing equipment, we will pay attention to the areas of their preferred application.

Such a wide range of applications for dosing pumps caused a real "storm" in design development, which led to the birth of dosing pumps. various types, capacities and modifications. Now let's try to understand all the variety of dosing equipment that is currently on the market.

Classification of dosing pumps

With all its diversity, dosing pumps are divided into:

• depending on the design of the piston - on plunger and diaphragm;
• depending on the type of drive - for pumps with a mechanical and hydraulic drive.

Dosing pumps are characterized by the feed rate of the dosed liquid, maximum operating pressure, dosing accuracy, type of working chamber (depending on whether the pump is plunger or diaphragm), type of material from which the working chamber is made. Table 1 presents the main structural materials of the working chamber and piston for plunger and diaphragm (diaphragm) type metering pumps.

Accepted designations of structural materials:

PTFE- polytetrafluoroethylene (fluoroplast);

PVC- polyvinyl chloride;

RE- polyethylene;

RR- polypropylene;

PVDF- polyvinyl difluoride.

The structural materials from which the working chamber and the piston (or membrane) are made must be comprehensively subject to examination for the chemical compatibility of the material with the pumped medium.

The supply of reagents by dosing pumps is regulated by changing the length of the piston stroke or the number of strokes (working cycles). The piston stroke length can be changed either with the help of a micrometer screw or with the help of special mechanical dividers that limit the piston stroke. The change in the number of piston strokes is carried out by electrical circuit pump control. As a rule, metering pumps have safety valves and devices for bleeding air from the working chamber.

Almost all modern dosing pumps are equipped with electronic controllers for their control, which allow not only to change the reagent supply from the pump control panel, but also to adjust the dosing rate according to signals from external control and measuring devices (for example, pulse counters, devices (or sensors) monitoring of water quality indicators, etc.). The main types of controllers used to control dosing pumps are listed in Table 2.

table 2

Description of controllers

Pump control for constant dosing with adjustable stroke rate (10..100%).

Pump control for constant dosing with adjustable stroke rate (10..100%) with the possibility of connecting a reagent level sensor in the supply tank.

Pump control for constant dosing with adjustable stroke number (10..100%) and adjustable stroke volume (0..100%).

Control of a constant dosing pump with an adjustable number of strokes (10..100%) and an adjustable stroke volume (0..100%) with the possibility of connecting a reagent level sensor in the supply tank.

Pump control for constant dosing with adjustable stroke volume (0..100%) with the possibility of connecting a reagent level sensor in the supply tank; Equipped with LCD display and microprocessor control.

Pump control for proportional dosing controlled by a standard analog signal (0..20 mA, 4..20 mA) from a peripheral device.

Pump control for proportional dosing controlled by a standard analog signal (0..20 mA, 4..20 mA) coming from a peripheral device, with the possibility of connecting a reagent level sensor in the supply tank.

Pump control for proportional dosing with an integrated controller of a standard analog signal (0..20 mA, 4..20 mA) coming from a peripheral device, with the possibility of connecting a reagent level sensor in the supply tank.

Pump control for proportional dosing controlled by a standard analog signal (0..20 mA, 4..20 mA) coming from a peripheral device, with the ability to connect a reagent level sensor in the supply tank; Equipped with LCD display and microprocessor control.

Pump control for proportional dosing on a signal from a pulse water meter; equipped with a divider and/or multiplier for input pulses.

Pump control for proportional dosing by a signal from a pulse water meter, with the possibility of connecting a reagent level sensor in the supply tank; equipped with a divider and/or multiplier for input pulses.

Pump control for proportional dosing by a signal from a pulse water meter, with the possibility of connecting a reagent level sensor in the supply tank; equipped with a 60 second (0..60") timer.

Pump control for proportional dosing via RS 485 interface.

Plunger-type metering pumps

Plunger dosing pumps are usually used where a powerful pressure of the dosing medium is required (up to 20-30 MPa and more) or where a large volume of dosing reagent is required. They are designed for volumetric pressure dosing of neutral, aggressive, toxic and harmful liquids, emulsions and suspensions with high kinematic viscosity (about 10 -4 - 10 -5 m 2 /s), with a density of up to 2000 kg/m 3. Depending on the type of pump (piston diameter, pump characteristic and number of piston strokes), the delivery can vary from a few tenths of a milliliter to several thousand liters per hour.

The principal design of metering pumps of this type is shown in Fig.1. The principle of operation of plunger pumps is based on the reciprocating movement of one solid cylinder (piston) inside another hollow cylinder (body), as a result of which a rarefaction / injection effect is created inside the second cylinder. Depending on the position of the full-bodied cylinder (piston), either a vacuum pressure (suction process) or discharge pressure (creation of pressure in the pressure line) is created in the pump chamber (casing). The process is controlled by a system of suction and discharge valves. These pumps provide very accurate dosing as both the piston and the working chamber are made of materials that are practically not subject to any mechanical changes during the operation of the pump (with the exception of corrosion and mechanical wear of moving parts).

The design feature of such metering pumps is that the pumped medium is in direct contact with the material not only of the working chamber, but also with the piston. Therefore, when selecting the materials from which the working chamber and piston will be made, special attention should be paid not only to the chemical compatibility of structural materials and the pumped medium, but also to the content of abrasive materials in the latter. The presence of abrasives in the dosing liquid (especially micron sizes) can lead to their accumulation in the cavity formed between the cylindrical surfaces of the piston and the working chamber, which will cause additional mechanical wear, and, ultimately, a violation of the dosing accuracy (up to "jamming" pump), and the tightness of the working chamber. To protect the piston from the action of dosed aggressive reagents, plunger pumps are equipped with high-alloy steel bellows or fluoroplastic membranes that separate the flow part of the pump and the drive chamber with the piston (plunger) moving in it.

As a drive for plunger pumps, a mechanical type of drive is most often used with the transmission of the torque of the electric motor to the reciprocating movement of the piston through various modifications of the crank mechanisms.

Membrane (diaphragm) dosing pumps

In membrane (diaphragm) dosing pumps, the suction and expulsion of the substance from the working chamber occurs for due to the forced oscillation of the membrane, which is actually one of the walls of the working chamber. The principal design of metering pumps of this type is shown in Fig.2. The use of an elastic membrane as a kind of “piston” causes both advantages and disadvantages of diaphragm pumps.

The advantages of using this type of pumps, first of all, include the absence of any moving parts in the working chamber, which eliminates the ingress of any mechanical impurities into the pumped medium during pump operation. That is why diaphragm type pumps are used for dosing ultrapure reagents or ultrapure water in the electronics and pharmaceutical industries. The second indisputable advantage of diaphragm dosing pumps is the possibility of complete manufacturing of the working chamber from corrosion-resistant materials that can withstand contact with almost any aggressive medium. This advantage of metering pumps has led to their widespread use in the chemical industry. And, finally, the absence of “stagnant” zones in the working chamber of the pump makes it possible to pump liquids containing abrasives (for example, coolants) with their help. Therefore, diaphragm dosing pumps are the most demanded on the market.

The main disadvantage of diaphragm dosing pumps should be considered not high precision dosing (compared to plunger). It's related:

a) with the membrane vibration cycle (it is impossible to predict the elastomer stretching/compression mode, especially when the temperature of the pumped medium changes);

b) with “fatigue” of the membrane material accumulating over time (the elastomer loses its original characteristics, stretches and, ultimately, not only dosing accuracy worsens, but also the main characteristics of the pump).

The second negative factor in the use of this type of metering pumps is again associated with membranes, more precisely with their mechanical strength. The impact of any large mechanical inclusions on the surface of the membrane can lead to destruction, and, as a result, to the loss of tightness of the working chamber. The third disadvantage is the low productivity of membrane pumps and the rather low working pressure developed. This is again due to the use of an elastic membrane as a "piston".

These shortcomings do not give rest to design thought. Manufacturers constantly make changes to the design of diaphragm pumps, change the composition of elastomers, introduce fillers to improve the strength characteristics of membranes, etc. For example, dosing pumps with a double diaphragm have appeared, the design of which allows you to "determine" the state of the working membrane and even "notify" the owner about destruction ... And yet these changes are only of a narrowly focused nature and do not concern the basic principle of operation and design of the diaphragm dosing pump.

As a drive for diaphragm dosing pumps, the most traditional is an electromagnetic (solenoid) drive. In this case, the oscillatory motion of the rod moving in the electromagnetic field of the solenoid is transmitted to the membrane wound. Dosing adjustment is carried out by changing the amplitude and stroke frequency of the rod. The features of this drive design determine the equal duration of relatively short periods of suction and discharge of the pump during one operating cycle. The second most common drive for diaphragm pumps is the drive with the transfer of the torque of the electric motor to the reciprocating movement of the piston through the crank mechanism, which we already mentioned when discussing plunger pumps.

And, finally, the most "exotic" drive for diaphragm dosing pumps is a hydraulic drive. Hydraulically driven diaphragm dosing pumps are very accurate dosing, but still somewhat inferior to plunger pumps. They are used for corrosive, toxic, abrasive, contaminated or viscous liquids. They may have a single or double diaphragm. The supply of reagents by pumps of this type can reach 2500 l / h at high pressure. The occurrence of oscillatory movements of the working membrane when using a hydraulic drive is carried out due to vibrations of the fluid located on the other side of the membrane. These fluctuations are caused by contraction/increase in the volume of this liquid, both due to traditional drives and due to pneumatic devices. Their main advantage is that the working membrane of such pumps is affected not by the rod (piston), but by the liquid. This makes it possible to evenly distribute the load on the entire surface of the membrane, and extend the life of the elastomer.

How to choose the right dosing pump?

Choosing a dosing pump is not an easy task, so it is better to entrust it to specialists. Nevertheless, within the framework of our discussion, it is necessary to determine the range of questions that you will have to answer.

First of all, it is necessary to determine the main characteristics: pump capacity (l / h) and its working pressure (MPa). Then characterize the pumped medium: name of the reagent (if a solution is used, then the concentration of the main substance,% or g / l), viscosity (cP or m 2 / s), density (kg / m 3), temperature (o C), presence suspended solids (% or mg/l). And finally, decide on the design of the pump itself: explosion protection, enclosure protection class (IP), pump control (manual, proportional to the main water flow (while determining the main flow, m 3 / h), proportional to the standard external analog signal (0 ..20 mA, 4..20 mA), the need for weekly programming, LCD equipment, etc.).

When choosing a control scheme for a dosing pump using a standard external analog signal (0..20 mA, 4..20 mV), you should specify which of the water quality indicators will be decisive for the operation of the dosing pump. Currently, the following devices (sensors) are most often used to control pumps:

• pH values;
• the content of active chlorine (both organic and inorganic);
• Red-Ox (redox) potential values;
• values ​​of electrical conductivity (resistivity);
• turbidity value.

The listed indicators are, as a rule, determining at individual stages of water treatment, therefore, on secondary measuring instruments, the upper and lower limit the value of the controlled parameter. The dosing pump maintains the value of this parameter within the specified limits.

Installation of dosing pumps

When discussing dosing pumps, it is impossible to ignore the basic requirements for their installation, as well as their piping schemes. This is due to the fact that in addition to the dosing pump itself, additional devices should be provided in the pump installation scheme to ensure both stable operation of the pump and obtaining a homogeneous mixture of the dosed reagent with the treated water.

First of all, let's pay attention to the containers for dissolving and storing the dosed reagent. When choosing them, the following points should be considered:

• The height of the tank must not exceed the suction height of the pump (if the pump is installed directly on the tank).
• The container must be provided with a lid for internal inspection and a place for attaching a mixing device (if necessary).
• For communication with the atmosphere, a threaded fitting must be provided (possibility of connecting a filter).
• The material from which the container is made must be chemically compatible with the dosing medium.

When dispensing small volumes of reagents, most often special containers made of either polyethylene or polypropylene are used to dissolve and store the dosed reagents. Such containers have the following range of standard volumes: 50 l, 100 l, 200 l, 500 l and 1000 l. When dispensing large volumes, special warehouses for chemical reagents should be provided, where dosing media will be prepared, filtered and stored.

A non-return valve and a liquid level sensor in the tank must be installed at the end of the suction pipeline located inside the tank (for pumps with the possibility of connecting such a sensor). The non-return valve and the level control sensor must be located strictly vertically in order to avoid their “sticking”. When dosing aggressive liquids, a shut-off valve must be installed in the suction line of the pump.

On the discharge line of the dosing pump, a check valve and a shut-off valve should also be installed to cut off the pump pressure line from the pipeline (or vessel equipment) where the dosed liquid is supplied. For homogenization (better mixing) of the dosing reagent and the main water flow, a static mixer should be installed on the main pipeline after the reagent inlet unit (especially when dosing viscous liquids).

The dosing pump must be rigidly fixed so that there is no vibration during its operation. The suction and discharge valves of the dosing head (working chamber) must be located strictly vertically in order to avoid their “sticking”. The piping of the dosing pump must be made in such a way that it is Free access to the pump, and so that the dosing head can be easily dismantled.

If the piping of the metering pump is carried out with flexible hoses, they must be laid freely without any kinks or tension. Any hose bends should be smooth without "breaks". The suction hose must be routed in such a way that air pockets cannot form, i.e. with an upward slope.

The same requirements apply to the piping of metering pumps with rigid pipelines.

Figures 3, 4, 5 show typical schemes installation of dosing pumps.

CIRCULATORS

Elements of the circulation system.

Starting our discussion of circulation pumps, first of all, attention should be paid to the functional differences between the operation of a pump in a heating system (or cooling system) and a pump that serves for the normal pumping of liquid. In our case, we will talk about a closed-type circulation system, the design of which does not allow any "harmful ingredients" to enter from the outside. Such circulation systems are used both for heating buildings and structures, and for cooling systems of process equipment.

The main purpose of the circulation pump is to increase the flow rate of water (or liquid) in the heat supply / removal system. As a result, the circulation system can more quickly respond to temperature fluctuations of heat carriers, the heat transfer coefficient increases, and, thereby, the control process is simplified. There is also by-effect from the installation of a circulation pump - this is the ability to use pipes with a smaller conditional passage. Thus, in the pipeline circulation system there may be a smaller amount of water, which reduces the inertia of the system as a whole.

In general, any circulation system can be divided into the following components: elements that produce heat, elements that consume heat, a heat transfer system and control elements. The first ones are heating boilers, circulating water heaters, plate heat exchangers, refrigerated equipment. The heat transfer and heat distribution system includes pipelines, switchgear, storage stations and, of course, a circulation pump. Heat consumers should be understood as heating units (radiators, convectors, plate heating elements, etc.). During normal pumping (for example, from tank to tank), the pump overcomes not only friction losses in pipelines, but also expends energy on “punching” various local resistance(liquid column, various kinds of filtering loads, creation of back pressure). At the same time, head losses in these systems are primarily due to the creation of the necessary back pressure (Hg), and the remaining loss components, although not constant, their fluctuations have little effect on the fluid pumping rate (Fig. 4).

Fig.4. Schematic diagram of the operation of the pump in the pumping mode.

In the circulation circuit, it is necessary to distinguish two fundamentally different kind pressure:

• Static pressure, i.e. total pressure in the circulation system. This pressure is determined by the operating conditions of heat consumers and producers.
• Dynamic pressure, i.e. pressure resulting from the operation of the circulation pump, which serves to overcome the sum of all pressure losses due to friction in the pipeline. It is due to the dynamic pressure that the constant movement of water in the circulation circuit is maintained.

Fig.5. Schematic diagram of the operation of the pump in circulation mode.

In the case of a pump in a circulation system, it must be imagined that the water in the pipeline must be constantly in motion. In this case, the pressure loss in the circulation system consists only of friction losses in pipelines and local resistances of the elements of the circulation network. These pressure losses remain practically constant throughout the entire operation of the pump (if we do not take into account the resistance that occurs due to the "overgrowth" of pipes with deposits). Therefore, the speed of fluid movement in pipelines, first of all, will be determined by the operation of the pump itself (Fig. 5). In order to regulate the speed of water flow in the circulation circuit, depending on the operating modes of consumers or heat producers, it has recently been customary to equip the electric motors of circulation pumps with step speed controllers, i.e. devices that allow switching the number of revolutions of the electric motor either automatically or manually.

The first circulation pumps for heating systems.

Already at the beginning of the twentieth century, a large number heating engineers had ideas for installation in pipelines heating systems, the so-called "circulation accelerators". However, during this period of the development of our civilization, electric motors were still equipped with open contacts, so the use of such units in water systems could lead to numerous accidents.

The breakthrough occurred thanks to the invention by engineer G. Bauknecht of the first closed (sealed) electric motor. After that, in 1929, V. Oplender developed the design of the “circulation accelerator”. To increase the speed of water circulation in the pipe elbow, a propeller-shaped wheel (axial type wheel) was installed. The wheel drive was carried out through a shaft connected to an electric motor. The shaft was sealed with gland seals. Similar "circulation accelerators" were made almost until 1955. The only thing that has drastically changed in the design of these pumps over time is the type of seal. They are more commonly known as dry rotor pumps.

The weakest point of the described design is the gland seal, the wear of which depended not only on the material of the gland itself, but also on the condition of the shaft surface. Even with a slight wear of the shaft surface, leaks appeared in the stuffing box seals of the pumps. The seals had to be stuffed again and again, and in case of severe wear of the shaft, it was necessary to grind and polish its surface. The solution to this problem was proposed by the Swiss engineer Ryutchi, who invented the "sealless" circulation pump. In this design, the electric motor was mounted directly on the body of the elbow, through which water passed, and was completely sealed. In this case, water played the role of lubricant. Such pumps are now called "wet rotor pumps". These pumps have been manufactured since 1952.

Later, instead of a knee, both in the first and in the second design, a “snail” began to be used, and this is how the design of modern circulation pumps was born.

Wet Rotor Pumps Figure 6 shows a section of a wet rotor circulation pump. The main design feature of this type of pumps is that the rotor of the electric motor (3), mounted on the shaft, operates completely submerged in water. This lubricates the graphite or ceramic bearings (4) and cools the motor. The thrust bearing is fastened with a retainer (6). The energized stator is separated from the pumped medium by a sleeve (2) made of non-magnetizable stainless steel (the wall thickness of the sleeve is 0.1 to 0.3 mm). The sleeve is attached to the pump housing (7) through a sealing gasket. A plug is installed on the end part of the motor housing, the purpose of which is to remove air from the sleeve. The impeller (5), fixed on the shaft with a stud or pin, is made of composite polymer material(usually made of polypropylene with reinforcing and heat-resistant additives). The shaft that drives the impeller is made of either stainless steel or sintered metal.

Fig.6. Basic design of a wet rotor pump. The numbers indicate: 1 - terminal box with frequency control 2 - sleeve 3 - electric motor 4 - bearing 5 - impeller 6 - retainer 7 - body

Recently, modifications of pumps with a wet rotor have appeared, in the design of which the shaft with bearings and the rotor form a single unit, the so-called "cartouche".

This design eliminates air stagnation in the housing and facilitates its removal when the pump is started. This also facilitates the repair of pumps, as simple replacement of individual components and parts. True, all these design changes negatively affect the cost of pumps and, above all, their operating cost. Glandless circulating pumps have a number of advantages. First of all, pumps of this type practically do not require Maintenance. They are quiet in operation optimal values between supply and pressure. The disadvantages of such pumps can only be attributed to their limited performance. This is due to the difficulty of sealing the sleeve that separates water from the stator, when switching to large rotor diameters.

Glandless pumps are equipped with single-phase or three-phase electric motors, depending on the dimensions and power. Depending on the conditional passage (capacity), they have both threaded and flanged connections to the pipeline.

As already mentioned above, the bearings of this type of pumps are lubricated with water from the circulation circuit. Therefore, when installing the pump, continuous circulation of water through the sleeve separating water from the stator must be ensured. This is only achieved when the pump shaft is in a perfectly horizontal position. If, during installation, the shaft is in a vertical or inclined position, this can cause unstable operation of the pump and its rapid failure.

Dry rotor pumps.

Pumps of this type are widely used when pumping large volumes of water. Unlike glandless pumps, this pump design requires the use of a motor seal to separate it from the pumped medium. These seals are of two types:

The stuffing box seal is the most traditional shaft seal. The disadvantages of this type of seal are well known to all organizations that operate conventional centrifugal pumps. The typical service life of gland seals is one to two years. However, if the stuffing box seals are under low load, then they can serve for quite a long time. On the contrary, if the operating conditions of the pump are close to extreme (high contamination of the pumped medium with mechanical impurities, overheating of the pump, etc.), the stuffing boxes fail very quickly.

Sliding mechanical seal. If we consider its design in a simplified way, this type of seal consists of two rings with carefully ground surfaces. These rings are pressed against each other with the help of a spring. When the pump shaft rotates, the rings also rotate relative to each other. Under the pressure of the water in the circulation circuit, a thin film of water is formed between the sliding surfaces of the rings, which seals the pump. The rings are usually made of graphite, but when the pump is working in difficult conditions, they can be made of either ceramic or stainless steel. It should be noted that the operating conditions of pumps with mechanical seals, as well as stuffing box pumps, greatly affect the service life. However, during the operation of pumps with mechanical seals, it is necessary to pay attention not only to the degree of water pollution, but also to the dust content of the surrounding air, since during the operation of the pump, vortex flows inevitably arise that can “pull in” along with air and dust particles. If these particles get on the surface of the plates, the latter can be damaged, which will lead to a violation of the tightness. In this respect, pumps with mechanical seals differ from pumps with stuffing box seals in terms of operating conditions.

Figure 7. Basic design of a dry rotor pump. The numbers indicate: 1 - lantern 2 - clutch cover 3 - clutch 4 - pump housing 5 - vent plug 6 - shaft 7 - impeller 8 - gap seal 9 - mechanical seal 10 - sealing ring.

General and very important point when operating pumps, both with stuffing box and mechanical seals, the sealing surfaces are destroyed when the pump is operated in the “dry running” mode, since both the first and second type of seal require the presence of a “lubricating” liquid. According to the type of execution, pumps with a dry rotor can be classified into two main types: Vertical pumps (or "in line" pumps), i.e. pumps in which the suction and discharge pipes have the same passage and are located on the same axis. In this case, the electric motor driving the impeller is located vertically. Horizontal pumps, i.e. pumps in which the suction pipe of the pump is located at the end of the "snail", and the discharge pipe is located radially on the shell of its casing. In this pump design, the motor is attached to the pump in a horizontal position.

We will consider the advantages and disadvantages of pump designs with a vertical and horizontal arrangement of the electric motor in our other publication. Now let's return to the discussion of circulation pumps and, as an example, consider a pump with a vertical type mechanical seal. Figure 7 shows a section of such a pump.

The electric motor through the coupling (3) drives the pump shaft (6), on which the impeller (7) is located. The water entering through the mouth of the impeller in the axial direction changes its direction of movement in the channels of the impeller to radial. The centrifugal forces acting on each particle of the liquid cause an increase in static pressure, as well as an increase in speed as the liquid passes through the channels of the impeller. After the impeller, the liquid is collected in a spiral housing (“snail”), while, due to the special design of the housing, the speed of the liquid slows down, due to this energy conversion, a further increase in static pressure occurs. Thus, the operation of any modern centrifugal pump is described.

Selection of a circulation pump.

The algorithm for selecting a centrifugal pump for a circulation system differs little from the process for selecting a pump for operation under normal conditions. In this section, we will try to focus your attention precisely on those distinctive steps that are unique to circulating systems.

As you know, the performance of a centrifugal pump depends on the pressure and, therefore, to a large extent on the hydraulic resistance of the network, i.e. pipelines and apparatus through which liquid is transported. Therefore, the pump-network system should be considered as a whole, and the choice of pumping equipment and pipelines should be decided on the basis of an analysis of the joint operation of the elements of this system.

The joint operation of the pump and the network is characterized by the point of material and energy balance of the system. To determine this point, you need to calculate energy costs in system. In the practice of hydraulic calculation pumping units and when analyzing the operating modes of pumps, the graphical-analytical method for calculating the joint operation of pump-network systems is widely used (Fig. 8). The pressure H, which the pump must create, is determined by the equation:

H= H g + h p, (1)

where N g - head loss (m) to overcome the hydraulic column of liquid (see Fig. 7 and 5)

h p - pressure loss (m) to overcome the local resistance of the network.

moreover, the pressure loss to overcome the local resistance of the network can be represented as follows: h p \u003d a·Q 2 (where a is the proportionality coefficient). Then the network characteristic is expressed by the parabola equation:

H \u003d H g + a Q 2 (2)

Here the first and main difference between a closed circulation system and a conventional liquid pumping is manifested. We have already drawn your attention to the fact that pressure losses in the circulation system are made up only of friction losses in pipelines and local resistances of the circulation network elements. Indeed, the component Hg in equations 1 and 2 for the circulation network will be equal to zero, because the energy costs to overcome the liquid column during its rise are compensated by the pressure of the same liquid column on the suction line of the pump. Now back to Figure 8. The intersection point of two curves A, reflecting the characteristics of the pump and the network, is called the operating or regime point. This point corresponds to the maximum liquid supply Q 1 pump in this network. If you need to increase the flow to the network, then you should increase the number of revolutions of the impeller. If this is not possible, then you need to install a new, more efficient pump or somehow reduce the hydraulic resistance of the network. If it is necessary to reduce the flow to the value of Q 2 by partially blocking the discharge pipeline, the lost pressure will increase to overcome the hydraulic resistance of the valve or valve on this pipeline. Such regulation (reduction) of the flow is permissible only in the case of low pump capacities.

Fig.8. Joint characteristic of centrifugal pump (1) and networks (2).

For high flow conditions, consideration should be given to replacing a smaller pump with a larger pump or reducing the impeller speed. Thus, centrifugal pump must be chosen so that the operating point corresponds to the given capacity and pressure at the highest possible efficiency. But such conditions are extremely rare. The operation of the circulation system is due to constantly changing parameters of heat supply / removal. Therefore, when choosing a pump for a circulation system, it is necessary to focus not only on the maximum performance, but also on the nominal and minimum performance. Right now it becomes clear (the second difference of the circulation system) why the electric motors of the circulation pumps are equipped with stepwise speed control. When changing the speed of the pump shaft with unchanged technical parameters of the circulation system, there is a cubic dependence of the power consumption (P) on the speed (n):

P 1 / P 2 \u003d (n 1 / n 2) 3 (3)

where n 1 and n 2 - speed before and after the change, respectively, (rpm)

P 1 and P 2 - power consumption before and after changing the speed, respectively, (W).

In this way, the performance of the pump can be rationally adjusted and adapted optimally to the heat demand of the circulation system.

All information in this publication has been for single pumps. But in practice, situations often arise in which a single pump cannot perform the tasks assigned to it. In such cases, two or more pumps are installed. In this case, both series and parallel connection of pumps is used. In the next publication, we will focus on the operation of such systems and try to dispel the myth that two identical pumps, when connected in series, will give double the pressure, and two identical pumps, when connected in parallel, will give twice the performance.

The MTZ dosing pump is an integral part of the hydrostatic complex that controls the tractor. It contributes to the correct distribution of fluid and its supply to the hydraulic cylinders, which, in turn, greatly simplifies the control of the tractor.

This allows the operator to apply much less effort to turn the wheel, which is very important when the tractor is heavily loaded.

1 What is the principle of operation of the MTZ pump?

The MTZ dispenser pump is produced at the tractor plant in Minsk. The manufacturer has simplified the device as much as possible to ensure good wear resistance of the mechanisms and ease of maintenance. The unit includes 3 main components:

There are several parts in the oscillating pump assembly: a fixed stator and a rotor, to which the spool of the device fits. The spool is attached with 2 springs and connected to the steering column shaft. Moving, the steering column drives the spool and, moving relative to the central axis, supplies oil to the inside of the pump.

The special valve block of the body contains anti-vacuum, safety, check and shock valves. check valves required in case of hydraulic motor failure. Then the valve closes the drain channel of the hydraulic amplification system, preventing the movement of fluid. Safety valves regulate the pressure in the oil pipeline system.

Anti-vacuum valves assist in the movement of oil into the hydraulic cylinders in the event of a system failure. Anti-shock valves regulate the pressure in the lines at a very high load when driving on uneven sections of the route.

It is necessary to install the dosing pump on equipment moving at a speed of no more than 50 km / h, and place it in the volumetric hydraulic drive of the machine.

Acting on the control system, the dosing pump supplies the working fluid to the hydraulic cylinder and enhances the operator's actions. In the absence of influence on the control system, the position of the pump becomes neutral, and it passes the liquid directly to the drain system.

2 How to properly install the dosing pump?

When installing a dosing pump on MTZ 80 and MTZ 82, partial replacement power steering systems (hydraulic steering control) on the HSC (hydraulic volumetric steering).

The GRU set includes:

If necessary, they also buy a crane that blocks the differential of the HSC mechanism. It is used to replace the lock used on power steering. This crane provides the ability to lock the steering wheel on unstable road sections, which improves trafficability.

2.1 Installation algorithm

1. First of all, remove the power steering box (distributor). To do this, remove the control levers, then remove the anther plates, seals and anthers. Then you need to remove the covers and pull out the spools.
2. At the next stage, the bearings are changed if the existing ones are worn out.
3. Remove the worm of the unit.
4. In place of the worm, a dispenser shaft is installed.
5. The dosing device is screwed to the required bar. Hidden bolts are used for installation.
6. Then the pump is checked and after that the dosing pump is installed on the MTZ in the hydraulic amplification system.

The rest of the HSC kit is changed before the unit is installed.

2.2 INSTALLING THE UNIT ON THE MTZ WITH YOUR HANDS (VIDEO)

3 Pump malfunctions

Any malfunction of the dispenser on the MTZ 82 or the steering volumetric control system can cause complications in the functioning of the control system. To restore the system to working capacity, a clear understanding of what exactly has become unusable is necessary. This can be judged by the following signs:

Also, contamination of the hydraulic boost circuit can lead to a malfunction.

If the pump valves become clogged with dirt and other particles, they will not be able to pass fluid through the system and regulate pressure. The result will be a decrease in system performance, and it may break.

Pumps batchers in the systems of water treatment

keywords: pump batcher, water treatment, reagent, station of dispensing, plunger pump

Many processes of water treatment demand use of reagents, actively apply them at the industrial enterprises, in the housing sector, in sports and improving complexes to chemical water treatment of pools. The majority of chemical reagents are active agents, and exact dispensing of these substances generally is required to provide their necessary concentration in the purified water. Pumps batchers, or as they are called still, the dosing pumps are used to these purposes.

Description:

Many water treatment processes require the use of reagents, they are actively used in industrial enterprises, in the field of housing and communal services, in sports and recreation complexes for the chemical water treatment of pools. Most chemical reagents are active substances, and in general, accurate dosing of these substances is required to ensure their required concentration in the treated water. For these purposes, dosing pumps are used, or, as they are also called, dosing pumps.

Many water treatment processes require the use of reagents, they are actively used in industrial enterprises, in the housing and communal services sector, in sports and recreation complexes for TOVP pools. Most chemical reagents are active substances, and in general, accurate dosing of these substances is required to ensure their required concentration in the treated water. For these purposes, dosing pumps are used, or, as they are also called, dosing pumps. They are designed for volumetric dosing under pressure of various liquids, as well as emulsions and suspensions.

Dosing pumps are used for the following processes in modern water treatment systems:

• dosing of biocide solutions for water disinfection;
• dosing of coagulant solutions before clarifying filters;
• dosing of inhibitors for reverse osmosis plants;
• correction of the salt composition of water, control and maintenance of its physico-chemical parameters in a given range for food production and for the heat and power industry;
• dosing of reagents for water disinfection in swimming pools and water parks.

There are various dosing stations on the market. The main elements of the dosing station are the container that contains the reagents and the dosing pump itself. The required concentration of the chemical reagent solution is prepared in the tank. Depending on the required flow rate of the finished solution and the pressure in the main network, the necessary dosing pump is selected. To automate the work process, a microprocessor controller is included in the dosing stations.

Depending on the purpose of the water treatment system, dosing stations can vary significantly in the accuracy of control and dosing of the reagent.

Accordingly, when choosing a dosing pump for technological process the following parameters must be taken into account:

• productivity;
• maximum back pressure;
• type of pumped liquid (reagent solution), which is especially important for working with aggressive liquids. In this case, one should take into account such parameters as viscosity, density, temperature, the presence of suspended solids;
• type of control system, which may be fully or partially automated. To control the system, sensors can be used that control the pH value of the active chlorine content, turbidity values, reagent levels, etc.

Dosing pumps differ depending on the piston design. They are of two types: plunger and diaphragm or membrane.

Depending on the type of drive, there are:

• mechanically driven pumps;
• hydraulic driven pumps.

The dosing pump belongs to the positive displacement pumps of the reciprocating type, it consists of a drive motor, a gearbox and a pump head. The gearbox reduces the engine speed by converting the rotary motion into reciprocating motion of the piston in the pump head.

Plunger systems are designed to dispense large volumes or generate high pressure. Plunger pumps operate on the principle of movement of the piston of the structure, inside which a vacuum or strong pressure is formed. When a vacuum is formed in a plunger device with a dispenser, the system sucks in liquid, and when it is pumped, it pushes it out. Such pumps can provide high precision dosing. Since the pumped reagent solution is in direct contact with the piston in such pumps, special attention must be paid to the compatibility of chamber and piston materials with chemical composition solution.

It is also important to evaluate the content of abrasives in the solution, as they can cause additional mechanical wear, which can lead to loss of tightness of the pump. These pumps are often equipped with mechanical drives.

The design of diaphragm dosing pumps is characterized by the presence of a closed chamber, which is separated from the drive by means of an absolutely tight diaphragm. Regulation of the pump is carried out by means of a system of valves at the inlet and outlet of the system. This design of the pump ensures the tightness of the internal space, which prevents the ingress of the pumped medium into the surrounding space. For such pumps, the advantage is the possibility of using for especially chemically aggressive solutions, since it is possible to manufacture the chamber from corrosion-resistant materials. Also, such pumps are capable of pumping solutions containing abrasives.

At the same time, diaphragm pumps cannot provide high dosing accuracy compared to plunger pumps. Also, the pressure developed by them cannot be large due to design features.

Most diaphragm metering pumps use a solenoid drive. Less commonly used hydraulic drive: it provides a higher accuracy of dosing reagents. For chemical water treatment in swimming pools, diaphragm dosing pumps are most often used.

The system for dosing reagents for swimming pools should include:

a) container (tank) for working solutions;

b) a device for suction of the working solution from the container;

c) a device for injecting a working solution into the pipeline for supplying water to the pool;

d) a metering pump connected to the suction / injection devices with hoses / tubes made of chemically resistant materials.

The water quality control system should include:

a) sensor-sensors for measuring the relevant monitored water quality parameters, usually placed in a flow cell;

b) a sensor for the flow of analyzed water through a cuvette with sensors.

According to GOST R 53491.2–2012 “Pools. Water preparation. Part 2. Safety requirements" "... The quantity and necessity of using reagents for water treatment should be strictly justified not only in order to ensure the safety of the health of users, but also in relation to environmental protection."

The material was prepared by N. A. Shonina, teacher of the Moscow Architectural Institute

1. Only qualified mechanics and locksmiths who have been instructed in safety precautions, who know the design of the units, have certain experience in operating, maintaining and repairing units, who have passed the exam for the right to install and maintain pumping equipment and are familiar with the operation manual for diaphragm pumps, are allowed to install and operate the units. NDM Areopagus.
2. The electrical equipment of the units is installed in accordance with GOST 12.2.007.0 and the current SNIP (Building Norms and Rules), PUE (Electrical Installation Rules) and is operated in accordance with the Rules technical operation consumer electrical installations.

The place of installation of the units must meet the following requirements:

Provide free access to the unit during operation, as well as the ability to assemble and disassemble units;

The mass of the foundation must be at least four times the mass of the units;

Units must only be installed in a horizontal position.

3. Units intended for operation in explosive and fire hazardous areas are equipped with explosion-proof driving and auxiliary electric motors and other explosion-proof electrical equipment with the level of explosion protection required by the operating conditions.
4. The explosion protection marking of the electric motor and pump is indicated in the Passport for the unit.
5. The electric motor and the diaphragm pump head, which has a ground bolt, are grounded.
6. Heating of frozen or crystallized products in the chamber of the flow part of the membrane pump head and in pipelines is carried out according to the Design.

Recommendations for the operation of dosing diaphragm pumps

1. It is recommended, if necessary, to provide for flushing the chamber of the flow path with a neutral liquid to perform routine and repair work; creation of a bypass line for bypassing 100% of the dosed liquid from the discharge line to the suction line when a safety valve is installed on it.
2. During the operation of the unit, there is a pulsation of the volume of the dosed liquid and pressure at the outlet of the unit. Pulsation can lead to vibration, leakage and destruction of pipelines. To equalize the fluid flow, it is recommended to install air (gas) caps (pneumohydraulic accumulators, pulsation compensators), placing them as close as possible to the unit valves.
3. It is necessary to ensure that the gas chamber of the cap is always filled with neutral gas or air at the pressure specified by the Project. When dosing liquids, whose vapors with air can form explosive mixtures, the caps must be filled only with neutral gas according to the Design. In critical cases, perform a verification calculation of the dosing system that ensures the operation of the dosing pump outside of resonance modes for the entire range of pump flow control.
4. To prevent accidents from exceeding the discharge pressure, it is recommended to provide for the installation electrocontact pressure gauge, which turns off the engine of the unit when the discharge pressure exceeds the limit, and, if necessary, a safety valve, a membrane safety device installed before the shut-off equipment.
5. When dispensing aggressive, polymerizing and crystallizing liquids with the unit, ensure that the pressure gauge is connected only through a media separator (separating diaphragm) or in another way that ensures that the internal cavities of the pressure gauge do not come into contact with the dosed liquid.

Operating instructions for dosing diaphragm pumps

1. All pipelines must be equipped with compensating devices to prevent deformation and rupture due to thermal stresses due to fluctuations in product temperature.
2. Expansion joints should not have U-bends in the vertical plane when pumping liquids prone to sludge.
3. Installation of all pipelines should be carried out so that their weight and forces from deformation are not transferred to the diaphragm pump head.
4. Typical malfunctions and methods for their elimination.
5. It is forbidden to troubleshoot or repair the unit on the go.
6. Under certain operating conditions, as well as depending on operating temperature dosing liquid, the surfaces of the units can become very hot (> 80°C, risk of burns). In these cases, appropriate safety measures (eg touch protection) must be provided.

Leak tightness of seals in dosing diaphragm pumps

• During the operation of the unit, it is necessary to monitor the tightness of the seals, avoiding the leakage of the dosed liquid to the outside.
• Minor leakage of the drive fluid through the gaskets of the sealing device is allowed.
• In order to avoid abnormal leaks and corrosion damage, the parts of the flow path of the unit must be periodically replaced with new ones. The frequency of replacement is calculated by the Consumer, based on the resistance of the materials of the flow path in dosing media. The depth of penetration of corrosion of parts of the flow path should not impair the performance of the unit.

Dismantling of dosing diaphragm pumps

• Before dismantling the diaphragm pump head, it is necessary to free the chamber of the fluid end from the dosing liquid, taking all precautions.
• If the dosing liquid is acid or alkali, toxic, flammable or explosive, the chamber of the flow path must be flushed according to the Design before disassembly, for example, by switching to the “inlet-outlet” line of the flushing fluid. All operations for dismantling and disassembling the diaphragm pump head must be carried out using the appropriate type of dosing liquid. individual means protection, and in the immediate vicinity of the work site there should be a container with an appropriate neutralizing solution.

Dosing pumps are special units whose function is to dose liquids circulating under pressure. Regardless of the design and manufacturer, these pumping systems are an essential attribute in many industries.

The principle of operation of the dosing pump and its device

The dosing pump is driven by an electric motor powered by current through a magnetic element. In addition to the motor, the design of the dosing pump includes the following elements:

• Reducer;
• Adjustment mechanism;
• Hydraulic cylinder;
• Control buttons.

The adjusting mechanism is used to convert the torque generated by the drive shaft. The result of this is the generation of reciprocating motion of the piston. The dosing pump device also makes it possible to adjust the stroke length of the piston. A hydraulic cylinder is required to carry out the workflow of the entire device.

The principle of operation of the pump is based on the suction of a certain dose of liquid, after which it is pushed into the dosing line.

By changing the length and stroke rate of the devices, operators can set the required capacity of the units. At the same time, the range of this indicator will be quite wide - from 5 ml / h. up to 40 thousand l/h

Selecting the type of dosing pumps - classification of devices

Dosing pumps can be used in the most different areas. At the same time, the units are divided among themselves by modification, performance and type. Due to the large number of types of pumps, the experts decided to divide the devices into three main types. On sale you can find the following systems:

• A plunger pump is a high-pressure device designed to work with large amounts of liquid or to create a constant strong pressure of flowing water. The unit can also be used when working with toxic substances with a density of up to 2 thousand kg / m 3. The plunger unit operates on the principle of piston displacement, in which high pressure or rarefaction;
• Membrane unit - in this device, suction is performed by vibrating the membrane. In this case, the membrane also plays the role of a working chamber. In their design, units of this kind resemble piston devices. For continuity of flow diaphragm pump equipped with two working chambers, each of which has a valve. When air is supplied to the air chamber, the air displaces liquid into the pipeline;
• Peristaltic pump - successfully cope with the intake and pumping of crystallizing and corrosive substances.

According to the type of drive, dosing pumps are divided among themselves into the following types:

• Hydraulic;
• Mechanical;

Each of these types of equipment has found its application in specific areas. In everyday life, their operation is considered impractical due to the high cost of the units.

Applications for dosing pumps

Wide functionality, high reliability and durability have made dosing pumps one of the most popular units in the industry. Today, this equipment is successfully used:

• In chemical plants for mixing, dissolving and dosing chemical substances and their compounds;
• At factories for the processing of petroleum products for the purpose of dosed addition of various additives to fuel and other combustible materials;
• On oil rigs for the purpose of adding additives and additives to wells and mouths;
• At spraying stations for water treatment;
• The units are used in steam generators and power plants for the purpose of processing chemicals;
• Most often dosing pumps are used in facilities for water treatment. The equipment is used for dosing of ferrous sulfate and other chemicals for the purpose of high-quality liquid purification;
• At food enterprises for the purpose of dosing and serving tomato, mayonnaise, butter, syrups and all kinds of sauces;
• For the purpose of making beverages, pumps supply dyes and other food additives in a dosed form;
• For self-service car washes in the production of steel and other metals;
• For the production of ceramic products. The pumps are used for the pool where the ceramic products go through the cooling phase.

Today it is quite difficult to find pumping equipment that could compete with dosing units in terms of popularity. They are used almost everywhere where liquid supply in exact quantity is required.

Dosing pumps type ND - features and benefits

These units consist of a pump and a drive. The role of the drive in the design is played by a gear motor and an electric motor.

The design of the units also includes a double or single driving mechanism and one or two hydraulic cylinders.

The advantages of this equipment include:

• Good build quality and parts;
• Long terms of operation;
• Ease of repair and ease of maintenance;
• High performance.

Dosing pumps of this brand are most often used in the oil industry and in the production of chemicals.

Aqua brand units - equipment applications

Pumps of this brand are widely used in the treatment of large amounts of water. They cope well with the intake and pump over especially large volumes of liquid.

Nowadays, these pumps are also used in pharmacology and food production. Among the advantages of devices of this brand should be highlighted:

• Simple design;
• Long warranty period;
• Ease of maintenance;
• Chemical resistance;
• Ability to withstand extreme loads.

The disadvantages of the pumps of this manufacturer include a relatively high cost, which makes them inaccessible to some buyers.