Device and principle of operation piston pumps

Piston pump called a reciprocating pump, the working parts of which are made in the form of pistons. By number of pistons these pumps are divided into single-piston, double-piston, triple-piston and multi-piston . Based on the number of discharge and suction cycles per double stroke of the piston distinguish between pumps single acting, double acting and differential .

Diagram of a single-acting single-piston pump presented on

rice. 3.1.

When the piston moves to the right, a vacuum is created in the left cavity of the cylinder and in the working chamber. Due to the vacuum, the upper discharge valve K n presses against the seat, and the lower suction valve K in rises, and liquid is sucked into the gap created through the suction pipe from the source into the working chamber. When the piston moves to the left, a high blood pressure, under the influence of which the suction valve K in closes and the discharge valve K n rises and the liquid is forced out of the cylinder into the pressure pipeline.

With repeated reciprocating movement of the piston, water moves through the suction pipe through the pump cylinder into the discharge pipe and further to the point of consumption. In this case, the supply of liquid to the discharge line is uneven, which is significant drawback single acting pumps. To eliminate this drawback, double-acting pumps are used.

On rice. 3.2 presented double acting pump diagram (with two working chambers). The suction process in one chamber occurs simultaneously with the injection process in the other.

To ensure uniform flow, differential pumps (piston and plunger) are used. On rice. 3.3 shown differential pump diagram with piston diameters D 1 And D 2 . On the suction side it operates as a single-acting pump, on the discharge side as a double-acting pump. His distinctive feature is that during one revolution of the crank shaft it produces suction during one stroke of the piston, and injection of liquid during both strokes of the piston, displacing it alternately from the chambers A And B into the discharge pipeline.

In the direction of the axis of movement of the working bodies piston (plunger) pumps can be horizontal And vertical .

Basic concepts used in pump theory

On rice. 3.4 shown pumping installation diagram , consisting of a pumping unit 1 , which includes a pump and a motor (the motor is not shown in the diagram), a suction pipe 2 and pressure pipeline 3 , removing liquid from the pump to its destination.

There is a mesh at the bottom of the suction pipe 4 , which protects the suction pipe from foreign objects and a check valve necessary for filling the pump with liquid before starting (in vane pumps) and preventing the reverse movement of liquid if the pump stops.

Pump theory uses a number of terms and definitions that apply to pumps of all types, including piston pumps.

Pump head

When the pump is running, the fluid is reported extra energy, which is spent on overcoming resistance in the pressure pipeline and lifting liquid into the reservoir. Vertical distance h Sun from the free surface of the reservoir to the center of the pump is called vacuum suction lift . Energy losses in the suction pipeline are called absorption losses Vertical distance h n from the center of the pump to the water level in the tank is called geodetic injection height . Energy losses in the pressure line are called pumping losses . Sum of geodetic heights h sun + h n, added to the sum of energy losses in the system, is called pump pressure N :

N = h sun + h n + h wsun + h wн. (7.9 )

Pressure, developed by the pump, represents the amount of energy supplied by the pump to a unit mass of the pumped liquid. Pressure measured in meters of column of pumped liquid or in pressure units.

The pressure developed by a running pump can also be determined by the formula ( 7.9 ) using the readings of a vacuum gauge and pressure gauge, which are usually equipped pumping units (rice. 3.4):

H = h m + h in + Δh + (w n 2 – w in 2) / (2 g) , (7.10 )

Where N – pump pressure, m;

h m– pressure gauge reading, expressed in meters of the pumped liquid column;

h in– vacuum gauge reading, expressed in meters of the pumped liquid column;

Δh– vertical distance between the connection points of the pressure gauge and vacuum gauge, m;

w n, w V– speeds in the discharge and suction lines (at the points where the pressure gauge and vacuum gauge are connected), m/s;

g m/s 2.

One of the main technical indicators of the pump is also pump pressure R:

R = R To - R n + ρ (w to 2 – w n 2) / (2 g) + ρg (z To - z m), (7.11 )

Where R To, R n– pressure at the outlet and inlet of the pump, Pa;

ρ – density of the liquid medium, kg/m 3;

w to, w n– velocity of the liquid medium at the outlet and inlet to the pump, m/s;

g- acceleration of gravity, m/s 2;

z to, z n– height of the center of gravity of the cross-section of the outlet and inlet of the pump, m.

Pump head N and pump pressure R interconnected by dependence

N =R/ (ρg) , (7.12 )

Where ρ – density of the liquid medium, kg/m 3;

g- acceleration of gravity, m/s 2.

Piston pump

Piston pump(plunger pump) - one of the types of volumetric hydraulic machines in which the displacers are one or more pistons (plungers) performing reciprocating motion.

Rice. 2. Differential circuit for switching on a piston pump. During the movement of the piston to the left, part of the liquid is diverted into the rod cavity, the volume of which is less than the volume of the displaced liquid due to the fact that part of the volume of the rod cavity is occupied by the rod

Unlike many other positive displacement pumps, piston pumps are not reversible, that is, they cannot operate as hydraulic motors due to the valve distribution system.

Piston pumps should not be confused with rotary piston pumps, which include, for example, axial piston and radial piston pumps.

Principle of operation

The operating principle of a piston pump (Fig. 1) is as follows. When the piston moves to the right, a vacuum is created in the working chamber of the pump, the lower valve is open and the upper valve is closed, and liquid is sucked in. When moving in the opposite direction, excess pressure is created in the working chamber, and the upper valve is already open and the lower one is closed - liquid is pumped.

One type of piston pump is the diaphragm pump.

Fighting pulsation

One of the disadvantages of piston pumps, like other positive displacement pumps, is the pulsation of flow and pressure. Pulsations can be reduced by arranging several pistons in a row and connecting them to one shaft so that their operating cycles are shifted in phase relative to each other at equal angles. Another way to combat pulsation is to use a differential pump activation circuit (Fig. 2), in which liquid is pumped not only during the forward stroke of the piston, but also during the reverse stroke.

Double-acting pumps are also widely used, in which both the piston and rod chambers have (in contrast to the differential switching circuit) their own valve distribution system. Such pumps have a lower pulsation coefficient and higher efficiency than single-acting pumps (Fig. 1).

To combat pulsation, hydraulic accumulators are also used, which at the moment highest pressure They store energy and release it when the pressure drops.

Application

Piston pumps have been used since ancient times. Their use for water supply purposes has been known since the 2nd century BC. Currently, piston pumps are used in water supply systems, food and chemical industry, at home. Diaphragm pumps are used, for example, in fuel supply systems in internal combustion engines.

see also

Literature

1. Hydraulics, hydraulic machines and hydraulic drives: Textbook for mechanical engineering universities / T. M. Bashta, S. S. Rudnev, B. B. Nekrasov and others - 2nd ed., revised. - M.: Mechanical Engineering, 1982.
2. Geyer V. G., Dulin V. S., Zarya A. N. Hydraulics and hydraulic drive: Textbook for universities. - 3rd ed., revised. and additional - M.: Nedra, 1991.

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See what a “piston pump” is in other dictionaries:

piston pump- A reciprocating pump, the working parts of which are made in the form of pistons. [GOST 17398 72] Subjects pump EN piston pump DE Kolbenpumpe FR pompe à pistons ...

A positive-displacement pump whose working body is a piston that performs a reciprocating movement in a cylinder... Big Encyclopedic Dictionary

A positive-displacement pump whose working body is a piston that performs a reciprocating movement in a cylinder. * * * PISTON PUMP PISTON PUMP, a volumetric pump, the working element of which is a piston that performs a reciprocating movement in ... ... encyclopedic Dictionary

piston pump- stūmoklinis siurblys statusas T sritis automatika atitikmenys: engl. piston pump; positive displacement pump vok. Kolbenpumpe, f; Pumpe in Verdrängungsbauart, f; volummetrische Pumpe, f rus. piston pump, m pranc. pompe à piston, f; pompe… … Automatikos terminų žodynas

piston pump- stūmoklinis siurblys statusas T sritis fizika atitikmenys: engl. piston pump vok. Kolbenpumpe, f rus. piston pump, m pranc. pompe à piston, f … Fizikos terminų žodynas

piston pump- stūmoklinis siurblys statusas T sritis Energetika apibrėžtis Slankiojamojo judesio siurblys, kurio pagrindinis darbinis mechanizmas yra stūmoklis. Skysčio tiekimo netolygumui sumažinti naudojami daugiacilindriai siurbliai arba pneumatiniai ar… … Aiškinamasis šiluminės ir branduolinės technikos terminų žodynas

See Art. Pump... Great Soviet Encyclopedia

A reciprocating pump, the working parts of which are made in the form of pistons (see figure). The unevenness of fluid supply is reduced by using multi-cylinder P. n., as well as pneumohydraulic. batteries. Head 10,000 m or more. They find... ... Big Encyclopedic Polytechnic Dictionary

piston pump- volumetric pump... Dictionary of Russian synonyms for automatic control technologies

axial piston pump- A rotary piston pump, in which the axis of rotation of the rotor is parallel to the axes of the working elements or makes an angle with them less than or equal to 45°. [GOST 17398 72] Subjects pump EN axial piston pump DE Axialkolbenpumpe FR pompe à pistons axiaux … Technical Translator's Guide

Hand pump will be useful to every owner of a country or country house, to which the public water supply is not connected. Of course, you can use a simpler design, such as a “crane”, but if the depth of the well or well is large, it is still better to give preference to a pump. If the depth of groundwater is up to 10 meters, then you can successfully use a manual piston pump for water, which is easy to make with your own hands.

Features of using a piston pump

In the private sector it is not always possible to connect to centralized water supply. Therefore, amateur gardeners often have to use groundwater for their purposes. However, not all gardeners know how to extract water with the least amount of labor, and what equipment to use for this.

However, you can be sure that constructing cheap, simple and at this time reliable driven wells on your own will be affordable for every amateur summer resident. And at the same time, it is not necessary to carry water in buckets; it is enough to simply install a pump that can ensure its supply directly to the house.

To lift water from a well, two types of pumps are mainly used: centrifugal and piston. Moreover, the centrifugal apparatus requires forces that are almost 3 times greater than that required by a piston pump. In addition, a centrifugal apparatus cannot provide water suction to such a height as a piston apparatus. Therefore, interest in piston pumps has recently increased significantly.

Such pumps are usually used when the water surface has high level, that is, the water is close to the ground. The maximum limit of water occurrence for such pumps is 8 - 10 meters. Atmospheric pressure will not allow a piston pump to lift water from a greater depth.

In addition, you don’t always want to use a powerful pump, if you only need a little water - a bucket or two. It is also worth noting that devices powered by power are not always electrical network, can perform their function without failure. In this case, a manual piston water pump can be extremely useful. A non-volatile piston pump will come in handy if there are network failures, the lights are turned off for a while, or garden plot simply not.

Water piston pump design

A piston pump is called so because the process of pumping liquids is provided by a working element called a piston. The pump itself is a metal body with a piston and rod that drives the working element. The piston, in turn, is located in a pipe that is connected to the bottom of the device. The working body moves up and down in the cylinder under the force of the rod, which is driven by a special lever. In this case, a simple multiplier is usually used, which increases the traction force from the handle.

When the piston moves down, water flows through the valve in the piston into the space above the piston (under water pressure the lower valve is closed). When the piston begins to move upward, water will be forced out of the space above the piston and pours into the outlet pipe. At the same time, a vacuum is formed in the sub-piston space, the lower valve opens, and water is sucked up along the piston. Then the cycle repeats automatically.

Deep versions of the piston pump are used if the waters lie at a depth of more than 8 - 10 meters. In its design, such a device completely repeats the model described above, but there are some differences. For example, the piston rod “walks” in the exhaust pipe, which is located on the top cover of the cylinder, and not on the side.

Types of piston water pumps

Piston water pumps can be mechanically or manually driven. Mechanically driven pumps, in turn, are divided into two types: drive units, in which the piston is activated using a connecting rod and crank mechanism from a motor, which is located separately and connected to the pump by transmission; direct-acting pumps in which the piston performs reciprocating movements using a rod.

Based on the type of working body that ensures fluid displacement, the following pumps are distinguished:

1. Piston (the piston has the shape of a disk);
2. Plunger (the piston has a cylindrical shape);
3. Diaphragm (the working fluid is separated from the piston by a special diaphragm, and the cylinder contains an emulsion or oil).

In accordance with the operating method, the following types of piston pumps for lifting water are distinguished:

• Single action pump.
• A double-acting pump that supplies liquid more evenly compared to differential or single-acting devices, because it is equipped with two working chambers, and the piston pumps liquid twice in one revolution.
• Differential pumps. Such pumps are double-acting devices and are equipped with 2 working chambers: one has no valves, and the other contains a working and suction valve.

By location, piston pumps can be horizontal or vertical, and by the number of cylinders - those equipped with one, two or more cylinders. Pumps with one, two or more pistons are distinguished based on the number of pistons. In addition, there are piston pumps with large pistons with a diameter of more than 150 millimeters, medium ones with a diameter of about 50 - 150 millimeters and small pistons with a diameter of less than 50 millimeters.

In accordance with the speed of the working body, low-speed piston pumps, medium-speed devices and high-speed pumps are distinguished. Piston pumps can be used to pump cold water(conventional pumps), hot water(hot pumps), as well as for working with various acidic substances (acid pumps) and clay solutions (mud pumps).

Drilling a well for a piston pump

The pump is hung in a well or well. Before installing a piston pump for water, you need to drill a well, having first found out the approximate depth of groundwater in your area. It is recommended to carry out the work in the following sequence:

1. To make drilling more convenient, it is necessary to dig a pit at the site of the well, which has a depth of 1-1.2 meters. Place a tripod made of thin logs in the center above it. You need to hang the block on a tripod. Screw the drill onto the lower end of the pipe, and secure the wrench onto the upper end.
2. It is recommended to install the pipe vertically in the center of the hole. Its upper end will rest on a tripod or be suspended on a block. Rotating the pipe to the right with a collar, it must be buried the entire length of the drill into the soil - about 30-40 centimeters.
3. Then the pipe must be raised to the level of the bottom of the hole, the soil must be cleared out of the drill, and then continue drilling the well again. It is necessary to work in this way until the entire pipe goes into the ground.
4. Then screw the second pipe link onto it using a coupling and continue drilling until the drill reaches the soil, which is saturated with water.
5. After this, replace the drill with a filter, carefully seal the joint with the filter pipe with tow, impregnated with red lead. Lower the pipe with the filter into the well and push it into the ground with a sledgehammer.
6. To protect the upper end of the pipe from damage, screw the coupling onto it and place a gasket made of hardwood on top. Make marks on the pipe to observe the immersion level of the pipe.
7. The gasket will have to be replaced from time to time. Periodically measure the distance to the water in the pipe with a cord and weight.
8. When the layer of water in the pipe rises above the filter head by 30-40 centimeters, that is, it will be equal to 1.2-1.3 meters, you can stop clogging.
9. Check the rate of water flow into the well. Pour water from a bucket into the upper end of the pipe. If the water, having filled the well, does not decrease, then it means that you have not drilled the well enough and you will have to continue drilling. If the water from the pipe is quickly absorbed by the well, then the work can be considered completed.

DIY piston pump for water

The question of making a piston pump with your own hands is the most pressing for gardeners and summer residents. Manufacturers nowadays offer a wide range of water pumps, but their main drawback is price. In addition, the vast majority of them are electric, and in conditions of periodic use of water, it is more advisable to stock up on a backup unit for pumping water in any conditions.

So, you can make your own manual piston water pump from scrap materials using the following instructions:

1. We make the body. The body of a manual piston pump is a metal cylinder, which you can use as a piece of pipe, a hydraulic cylinder body, or a liner from a diesel engine. Selecting a case will not be difficult if you understand what you want to get in the end. But it is best to use a piece of pipe as a body that has a diameter of 80 millimeters or more. The length of the segment is about 60-80 centimeters. Perfect option, if you can grind on lathe the insides of the pipe or at least remove the internal irregularities with a scraper. Then the piston pump will be of high quality and will easily pump water. By the way, the body does not have to be cylindrical. It can be 4- or 6-gonal, the main thing is that throughout working length there was the same cross-section, and the piston had a similar shape.
2. Cut out the lid. Lids can be made of thick plastic or metal. You can even make them from wood! If you use larch or oak, then such covers will last longer than one season. The wood will swell in water and reliably seal the gap between the body walls. You need to make a hole in the cap for the rod, cut off the bottom and insert a piston inside, and insert a new cap with a valve into the bottom. The exhaust pipe is welded to the side.
3. Install the piston. The piston can be made from different materials- wood, metal, plastic. The main thing is that it is sealed with a rubber ring. Oddly enough, the piston can form a large gap between the walls of the housing. But it is advisable to install it more tightly, but so that it moves freely without much tension. A small amount of water will seep between the housing walls and the piston, but the bulk of it will pass through the valves.
4. Inlet pipe. All components of a homemade piston water pump must be reliable. The inlet pipe, through which water is supplied into the apparatus, must be rigid so that its walls do not collapse when water is sucked in. It is better to use special hoses that are reinforced with a steel spring, plastic or metal pipes.
5. Check valves. A fairly important part of the pump is check valves, the performance of the entire piston pump depends on them. They must be strong enough so that water cannot flow back into the incoming hose. Remember, if the valves “poison”, you will uselessly drive half the water back and forth, and a pump left idle will slowly drain all the water from the pipes back into the well. Therefore, pay close attention to lapping the valves. The simplest of them are membrane and ball. If you are using a round valve, it will be better if it is made of glass, heavy plastic or hard rubber. Great option consists of making diaphragm valves from fairly durable rubber, but not too thick. A piece of such rubber must be attached to the valve hole. You can use rivets or screws - nuts.
6. Other components. The outlet pipe, like the rod, must have a length that allows the pump to be immersed in a layer of water with a depth of half a meter or a meter. To make it lighter, a rod made of thin duralumin pipes is usually used.

Thus, to draw water from a well in a country house, it is customary to use piston pumps, which enable gardeners to use groundwater for their own purposes. You can make a piston-type hand pump with your own hands, and it will become your assistant in case of power outages. In addition, such a device can be adapted to lift water from a pond that is located near your site.

The figure shows basic device a single-action pump driven by rotating machines, such as an electric motor.

The piston pump consists of a working chamber 1, inside of which there are suction B(k) and discharge H(k) valves; cylinder -5, piston-3, performing reciprocating movements inside the cylinder; 2 suction and 6 pressure pipes. To convert the rotational movement of the crank 9 into the reciprocating movement of the piston, a rod 4, a slider 7 and a connecting rod 8 are used.

Depending on their purpose, operating conditions and design features, piston pumps are classified as follows: By type of action By method of actuation By design of the working body By purpose

Piston pumps by type of action

1) pumps simple action;

2) pumps double acting.

Double-acting pumps have working chambers 1 and 2 on both sides of the cylinder, each of them has discharge valves 3 and 4 and suction valves 5 and 6. Therefore, both when the piston 10, driven by the rod 12, moves to the left and to the right in the cylinder 11, suction and discharge occur simultaneously. For example, when the piston moves to the right, in chamber 1 the suction valve 5 is open and liquid is sucked in, and in chamber 2 the discharge valve 4 is open, the liquid is supplied to the pressure pipeline. Thus, during one working stroke of the piston (movement to the right and left), almost double the volume of liquid is pumped in comparison with single-action pumps. Air caps 7 on the suction and 8 on the discharge, connected by tube 9, serve to reduce the pulsation of the pumped liquid;

3)built pumps. They consist of three single-acting cylinders, the pistons of which are mounted on a common crankshaft, with the cranks located at an angle of 120° to each other. Thus, for every third revolution of the shaft, one portion of water is sucked in and released, thereby achieving more uniform operation;

4) twin double acting pumps.

The pump consists of two double-acting pumps with common suction and discharge connections;

5) differential pumps.

In a differential pump, the liquid is supplied more evenly, in two stages; During the stroke of piston 2 to the left, part of the liquid enters the right cavity of cylinder 1, and during the stroke of the piston to the right, it is supplied to the pipeline with only two valves 4 - suction and 5 - discharge, instead of four. In Fig. shown: 8 - suction air cap, 6 - discharge air cap, 7 - discharge pipe, 8 - rod. The dimensions of a differential pump are almost the same as a simple one. The rod 8 of the differential pump is made with a cross-sectional area equal to half the area of ​​the piston; then equal volumes are supplied for each move.

Piston pumps according to the method of actuation:

1) drive, powered by a separately located engine connected to the pump by a crank mechanism or other transmission;

2) steam - direct acting; their pistons of pump 1 and 3 and steam cylinder 2 have a common rod 4

3) manual, manually actuated. These BKF type pumps are widely used.

According to the design of the working body:

1) piston engines themselves, in which a disk piston moves in a bored cylinder. O-rings or cuffs are used to seal the piston;

2) plunger (rock) ones, in which the working body is a plunger in the form of a hollow glass, which moves in the sealing gland without touching the inner walls of the cylinder. These pumps are easier to operate, since they do not have replaceable piston rings, cuffs, etc.; in Fig. a diagram of such a pump is given, where 1 is a rolling pin; 2 - cylinder; 3 - oil seal; 4 - discharge air cap; 5 - suction air chamber; V(k) and N(k) - suction and discharge valves;

3) diaphragm, in which the working body is a flexible diaphragm made of rubberized fabric or leather;

4) deep-sea pumps with a through-flow piston.

By purpose:

1) water;

2) sewer;

3) acidic and alkaline;

4) oil, etc.

Water jet pumps

The operating principle of a water jet pump or hydraulic elevator is based on the transfer of kinetic energy by the working fluid to the pumped liquid. The working (auxiliary) fluid has a large energy reserve compared to the energy reserve of the pumped liquid. Pumping occurs due to the action of one fluid flow with a large supply of energy on another without any intermediate mechanisms. The hydraulic elevator installation consists of an auxiliary (feed) pump 1, a supply pipeline 2, a hydraulic elevator 3, a suction pipeline 4, a pressure pipeline 5. Water under high pressure passes through the converging nozzle of the hydraulic elevator 3.

Due to a sharp increase in the speed at the narrowing of the hydraulic elevator nozzle, the pressure p in the mixing chamber drops and becomes less than atmospheric. Under atmospheric pressure, liquid from the reservoir

Annotation: Considered design features, theoretical processes, applications of the most common positive displacement pumps.

7.1 General characteristics of positive displacement pumps

Unlike centrifugal pumps, that are hydrodynamic machines, in positive displacement pumps fluid occurs due to a forced change in the volume of the cavity, which is filled with liquid. A positive displacement pump, regardless of design, has three main elements:

1. Working chamber- a cavity in the flow part of the pump, which is filled with liquid and the volume of which changes.
2. Displacer- an element whose movement changes the volume of the working chamber.
3. Distributor- a device used to direct the flow of liquid from the suction pipe into the working chamber or from the working chamber to the discharge pipe.

7.2 Piston pump design

A single-acting piston pump has the following main elements, rice. 7.1: cylinder 4, piston 8, piston rod 9, working chamber 5, suction pipe 7, discharge pipe 2, suction valve 6, discharge valve 1, pneumatic compensator 3 and crank mechanism 10 is connected to the engine.

When the piston 8 of the pump moves from left to right, a vacuum is formed in the working chamber 5, due to which the liquid rises through the suction pipe 7, opens the suction valve 6 and enters the working chamber, filling the space. When the piston moves back, the pressure in the working chamber increases, as a result of which the suction valve closes, and the discharge valve 1 opens and the liquid is displaced into the discharge pipe 2. Thus, for one revolution of the engine shaft, which corresponds to a double stroke of the piston, suction occurs in the pump once and once injection.

Disadvantage of a single piston pump single-acting - its uneven operation - the maximum feed is 3.14 times higher than the average. During suction, no liquid enters the network and the engine runs almost without load. At the beginning of the injection cycle, there is a sharp increase in the fluid flow rate in the injection pipeline, which, due to low compressibility, leads to the phenomenon of water hammer - the pressure behind the pump becomes significantly higher than average.

Rice. 7.1.

Rice. 7.2.

Such uneven operation of the pump leads to its premature wear. To reduce pressure fluctuations and flow of piston pumps, a pneumatic compensator is used 3 - chamber divided by a flexible membrane into two cavities. The lower one is connected to the pressure pipe, and the upper one is filled with compressed gas, which absorbs fluctuations in pressure and flow.

A double-acting piston pump has two working chambers A and B, two suction and two discharge valves, fig. 7.2. When the piston 8 moves from left to right, the liquid, under the action of vacuum, which is created, flows from the suction pipe 7 into chamber A, and at the same time, from chamber B, the liquid is pushed into the discharge pipe.

Three piston pump is a combination of three single-acting pumps driven by a common crankshaft, the cranks of which are offset from each other by 120°. Such pumps have significantly greater uniformity of operation than single- and double-acting single-piston pumps - the maximum flow exceeds the average by only 1.047 times. They use engine power more efficiently and supply fluid in an almost continuous flow. Disadvantage of three-piston pumps- their bulkiness and low reliability when working with abrasive slurries.

Compared to centrifugal pumps, piston pumps have the following advantages: the ability to create significant pressure with a small supply; rigid characteristic - with increasing pressure, the pump flow remains practically unchanged; self-priming ability - the pumps do not require priming before starting.

The disadvantage of such pumps- significant design complexity, especially many piston pumps, the presence of a reduction gear and a crank mechanism, valves, which results in low reliability of the pumps, significant dimensions and weight, complicates maintenance and protection from abrasive wear when transporting hydraulic mixtures. In addition, the disadvantage is the unevenness and limited supply, while the pumps have very large dimensions of 20-45 tons.

7.3 Design of plunger pumps

Plunger pumps are single-acting positive displacement pumps. Their operation scheme is the same as in three-cylinder single-acting piston pumps. The main advantages of plunger pumps c - opportunity to work for high pressures(10 MPa and more), simplicity of design, relatively low cost, ease of use, as well as ease of protection against abrasive wear. Structurally, plunger pumps are driven by a crank mechanism. The arrangement of the cylinders is horizontal or vertical. Hydraulic boxes are usually made with valve distribution.

Hydrotransport of solid materials is not the main application area for plunger pumps, but given the low cost (compared to membrane-piston ones), they are used for hydrotransportation of highly abrasive materials, such as polymetallic sludge. In plunger pumps, the seals and, to a lesser extent, the plunger body are subject to intense wear. In addition, in plunger pumps that are used for hydraulic transport, it is possible to flush the plunger.

Rice. 7.3.

Plunger pump, Fig. 7.3, as opposed to a piston pump, has plunger 1 as a moving element - a smooth metal rod. Moving forward or backward, it changes the volume of the working chamber 9. Thanks to this, the liquid enters the working chamber from the suction pipe 11 through the valve 10 or is forced into the pressure pipe 6 through the valve 8.

The main advantage of a plunger over a piston- simplicity of sealing, which is carried out similarly to the sealing of piston pump rods - using an oil seal 3. To protect the seal and plunger from abrasive particles, clean water is supplied into cavity 4 through hole 12 under pressure, which exceeds the liquid pressure in the working chamber. Clean water enters the working chamber in a small amount through the gap between the bushing and the plunger and flushes this gap, preventing solid particles from entering it.

Plunger pumps for transporting solid materials operate at a stroke rate of 80 ... 120 min-1, depending on the medium being transported. To increase the flow of plunger pumps, the number of plungers in one unit is increased (up to seven). However, due to the multi-cylinder design, the number of wearing parts increases.

7.4 Progressive cavity pumps

Screw pumps are designed for pumping clean water and water contaminated with sand, silt, particles of coal and rock, and is used for local drainage when driving horizontal workings and slopes, as well as for cleaning sludge from catch basins and settling basins.

Screw pumps of three standard sizes are used in mines: 1B6/5, 1B20/5 and 1B20/10 (1B - single-screw, numerator - flow in liters per 100 shaft revolutions, denominator - pressure in MPa.) At a pump shaft speed of 1450 rpm These pumps provide respectively: flow - 6; 17 and 17 m3/h; pressure - 50, 50 and 100 m, efficiency - 0.48; 0.60 and 0.64. Vacuum suction height 6m.

Screw pumps belong to the class of positive displacement machines. The main parts of a type 1B screw pump, Fig. 7.4 is a steel holder 3, a rubber stator 4, a steel rotor 5 and a cardan shaft 6. In the stator, which is a rubber cylinder with a cavity in the form of a two-lead spiral, a rotor rotates planetarily in the form of a single-lead screw with a pitch half the pitch of the stator spiral. Between the rotor and stator there are cavities that move progressively from one end of the stator to the other. Due to this, a vacuum is formed on one side of the stator and water is sucked through pipe 1, and water is pumped into the pipeline through pipe 9.

The cardan shaft 6 is connected via a drive shaft 11 and an elastic coupling to the engine shaft. Shaft 6, equipped with hinges 2 and 8, allows rotor 5 to perform planetary rotation in the stator. The hinge 8 is protected from sand and dirt by a rubber bellows 7. The shaft seal is provided by an oil seal 10. The shaft 7 is located in two angular contact ball bearings 13 located in the slots of the frame 12.

Thanks to the rubber stator, the pump can pump contaminated water. Water moves in space and serves as a lubricant between the rotor and stator. Without water in this space, you cannot run the pump, as the stator will fail.

Key terms:

Piston pump(plunger pump) - one of the types of volumetric hydraulic machines in which the displacers are one or more pistons (plungers) performing reciprocating motion.

Piston- a cylindrical part that performs a reciprocating movement inside the cylinder and serves to convert changes in pressure of a gas, steam or liquid into mechanical work, or vice versa - reciprocating movement into a change in pressure. In a piston mechanism, unlike a plunger mechanism, the seal is located on the cylindrical surface of the piston, usually in the form of one or more piston rings.

Screw or screw pump- a pump in which the pressure of the injected liquid is created by displacing the liquid by one or more screw metal rotors rotating inside a stator of the appropriate shape.

Control questions

1. List the main pumps for pumping contaminated liquids.
2. What parts does a positive displacement pump consist of?
3. What are the disadvantages of a piston pump?
4. What are the advantages of plunger pump?
5. Why are plunger pumps used to pump contaminated liquids?
6. What are the advantages of screw pumps?
7. What are the disadvantages of screw pumps?

Brief summary

• We examined pumps for pumping contaminated liquids
• We got acquainted with the design, advantages and disadvantages of plunger, screw and piston pumps.