The principle of operation of a screw pump. Characteristics of screw pumps Types of screw pumps

EVN5 submersible screw electric pump units of all standard sizes are manufactured according to the same design diagram with two working bodies connected in parallel, which provides:

• - doubling the feed with the same transverse dimensions;
• - the working bodies (screw pairs) are hydraulically mutually balanced, which eliminates the transfer of significant axial forces to the pump support bearings and the electric motor heel.

The EVN5 submersible screw electric pump unit (Figure 5) consists of the following elements: starting claw clutch centrifugal action, a base with a drive shaft, strainers installed at the pump inlet, working elements with right and left cages and screws, two eccentric swivel couplings, a safety valve and a slurry pipe.

When the unit is operating, the torque from the electric motor is transmitted to the working screws through the hydraulic protection protector shaft, the starting clutch and the eccentric couplings of the pump. According to the principle of operation, pumps are classified as positive displacement, and according to the method of transferring energy to liquid, they are classified as rotary. The main working bodies are single-thrust helical rotors with a right and left spiral direction and two rubber-metal cages, the internal cavity of which is a double-threaded screw surface with a pitch 2 times greater than the pitch of the screw, made of oil-gasoline-resistant rubber or other elastomer.

The operating principle of the pump is that a series of closed cavities are formed between the screw and the holder along the entire length, which, when the screw rotates, are filled with the pumped liquid, moving from the pump intake to its discharge. The screws rotate around their axis and in a circle with a radius equal to the eccentricity.

The liquid enters simultaneously into the left and right parts of the pump through receiving mesh filters. In the chamber between the screws, the flows are connected, and following further along the annular channel between the pump body and the upper casing, the liquid enters the pressure line through the safety valve.

Reservoir fluid is pumped practically without pulsation, without creating a stable emulsion of oil and water. The pump flow is equal to the sum of the flows of the working pairs, and the pump pressure is equal to the pressure of each working pair.

All main components and parts of diaphragm pumps are unified and are used, with some exceptions, in all pumping units.

Screw pumps of the EVN5 type have a number of specific parts: a starting cam clutch, eccentric swivel couplings, a safety valve, a slurry pipe, a strainer.

Starting jaw clutch centrifugal type connects the protector and pump shafts and, using retractable cams, ensures that the pump starts when the maximum torque is moving on the engine shaft, corresponding to a rotation speed of 800-1200 rpm.

This is due to the fact that the screw pump has a large static inertia and, in order to start it (overcome frictional forces), an increased starting torque is required. In addition, the starting clutch does not allow the pump shaft to rotate in the opposite direction.

During reverse rotation due to the bevel on the cams, the clutch does not engage, and the cams slip and thereby protect the pump from turning loose threaded connections. The coupling also protects the pump from emergency mode work, because When one of the working parts fails, the last one is switched off. Inside the pump base there is a shaft with bearings and support feet made of siliconized graphite.

There is no oil seal at the base, and the rubbing surfaces are lubricated with formation fluid. The drive shaft is fitted with protective bushings made of stainless steel, which rotate in bronze bushings. The end fixed heels rest on rubber gaskets for uniform transfer of forces to the entire surface of the heel.

The eccentric clutch allows for complex planetary rotation in the cages. Due to this, the liquid is pushed along the axis of the screw and the necessary pressure is created to lift the liquid to the surface.

At the top of the pump there is a spool safety valve, which consists of a housing, spool, piston, shock absorber and housing parts. The valve performs the following functions:

• - passes liquid into the tubing string during descent pumping unit into the well;
• - ensures drainage of liquid from the tubing string when lifting the unit from the well;
• - prevents the drainage of liquid from the pipe string through the working parts of the pump when the pump is stopped (all liquid is drained through the valve into the annulus);
• - protects the pump from dry friction and high blood pressure in the pressure line;
• - ensures fluid bypass from the pressure line back into the well either when there is insufficient influx of fluid from the formation, or when the fluid contains large quantity gas

The slurry pipe protects the pump from mechanical impurities and scale that fall out of the tubing string when the pump is stopped, installed, and acts as a sump.

Purpose and scope of pumps

Submersible screw pump units with a surface drive are often called UShVN (rod screw pump units) and are designed for pumping high-viscosity formation fluid from oil producing wells.

The installation is a submersible rod pump(ShVN), the stator of which is fixedly attached to the tubing string, and the screw to the rod string. A valve assembly is attached to the bottom of the stator. Ground equipment includes column head, preventer-tee, gearbox, modular insert, electric motor.

The rotation of the screw is carried out by a string of rods located inside the tubing string, from a ground drive consisting of a rotator (gearbox) and an electric motor.

The screw pump provides high performance when pumping high-viscosity liquid with a high gas factor and a significant content of mechanical impurities.

In directional wells, to reduce friction forces and wear of tubing pipes, centralizing couplings are installed, which act as intermediate radial supports and can be presented in two designs:

• - non-separable, placed directly on a full-size or shortened rod along special technology in factory conditions;
• - dismountable, installed between the couplings of standard rods.

It is most rational to use rod centralizers, ensuring their immobility relative to the tubing string, which leads to a reduction in energy consumption and pipe wear. Several lower rods located directly close to the eccentrically rotating rotor are not equipped with centralizers.

A rational area of ​​application for water pressure pumps is vertical wells or wells with low rates of curvature development with high-viscosity formation fluids with a high content of gas and mechanical impurities. Most often, pump pumps are used for flow rates from 3 to 50-100 m3/day with a head of up to 1000-1500 m, however, some standard sizes of pump pumps can have much greater production capabilities.

Screw pump - a pump in which the pressure of the pumped liquid is achieved by displacing the liquid by screw rotors (one or more) rotating inside a stator of the appropriate shape. According to the nature of the action of the working parts, screw pumps are classified as positive displacement pumps.

Screw pumps are rotary-gear pumps and can be made from gear pumps by reducing the number and increasing the angle of gear teeth.

Types of screw pumps. Single screw, double screw, triple screw.

Single Screw Pumps– are a horizontal displacement pump. The main components of such pumps are a static rubber casing, which has a double-thrust screw surface and a single-threaded screw made of metal, which performs rotational movements in the casing. During rotation, cavities are created between the screw and the surface of the holder, into which the pumped liquid is first sucked in and then moves along the axis of the screw to the discharge cavity.

Twin Screw Pumps– are used mainly when pumping sea, fresh and mineral water with an admixture of petroleum products.

Twin screw fuel oil pumps– are mainly used when pumping fuel oil and other viscous liquids. This type of pump has a single mechanical seal, a heating jacket, and the durable part is made of structural steel.

Three Screw Pumps– are used mainly when pumping non-aggressive liquids that have lubricity and do not contain abrasive mechanical impurities. Minimum indicator viscosity is limited by the lubricity of the liquid, the maximum is limited by the power of the electric motor and the suction capacity of the pump.

Differences between screw and screw pumps

Screw pumps are often grouped together with screw pumps, due to the fact that both types of pumps are displacement pumps. However, according to the nature of the impact of the working parts, screw pumps are dynamic.

The main component of a screw pump is a gerotor (screw) pair, which determines the properties of the pump unit and also determines the mechanism of its operation. The screw pair consists of a static element, the stator, and a moving part, the rotor. The stator is an internal spiral with the number of entries “m+1”. This item made of elastomer and combined with an iron cage. The rotor is an outer spiral with a number of entries “m”. This element is made of steel with or without further coating. The most common classic model is pumps with a double-start stator and a single-start rotor.

Screw eccentric screw pumps have many qualities that make them indispensable when working with heterogeneous viscous substances, substances with various impurities, as well as in those areas where it is simply impossible to use other pumping units due to different underlying conditions. These pumps are self-priming and do not require “priming”, in other words, the pumped substance is not a working fluid.

Screw eccentric pumps can pump heterogeneous substances with various impurities. The size of permissible inclusions depends on the size of the closed cavities between the rotor and stator. One rotation of the rotor corresponds to a certain size of the pumped substance, which allows fine tuning of the unit. In pumps of this type There is no pulsation or interruption of flow, despite the fact that they are able to withstand any production load at sustained pressure.

Main nodes

The design of screw pumps includes such elements as: drive motor-gearbox, adapter stand, stator-rotor pair, outlet pressure pipe, chamber, hinge, shaft sealing device.

Main working part screw pumping unit - screw pair. Inside the stator, made of elastomer, there is a metal helical rotor. The rotational movements of the robot lead to a change in the volume of the cavities inside the pair and the pumped liquid moves along the axis of the pump. The liquid is displaced, and the change in volume in the cavities creates a suction effect.

Operating principle of a screw pump

The screw pump consists of a rotor (the only moving part, number of strokes “m”) and a stator (internal spiral, number of strokes “m+1”). The liquid is pumped by moving along the axis of the screw, without being able to move backwards due to confined space, which is created by screws when the screw protrusions enter the grooves of an adjacent screw.

Temperature

The pump stator type determines maximum level operating temperature liquids.

In addition, the temperature can be determined by the nature of the liquid and the operating conditions of the pumping unit.

Liquid collection parameters

The screw pumping unit is self-priming, even with small supply volumes, and when working with water with temperatures such as 20 ° C, specific gravity 1 and viscosity level 1 °, the pressure it creates is 7 m of water column.

Feed characteristics

Screw pumps operate on a positive displacement principle with direct displacement of liquid, which promotes a constant, even flow of material that is not subject to sudden fluctuations.

Permissible fluids

Screw pumps have increased level chemical and mechanical resistance due to the fact that the stator is made of elastomeric material. These pumps are used for pumping any liquids with abnormal (non-Newtonian) viscosity. In addition, screw pumps are capable of pumping liquids containing solid particles (except abrasive ones) without compromising performance levels.

Commissioning and adjustment

To protect the pump stator, the pump must be filled with pumping fluid. After this, it is necessary to check that the shut-off valves of the pump inlet and outlet pipes are open. If the pump has a constant motor with adjustable speed, in order to regulate the flow rate of the substance, it is necessary to set the desired flow rate directly on the pump or install a control valve between its inlet and outlet.

Security measures

When turning on the pump, a number of safety precautions must be observed. Turning on the pump without filling the medium can lead to deformation of the stator, so turn on the pump without liquid is prohibited!

You should also avoid adjusting the pump flow rate by closing the supply valve, because this leads to deformation of the drive mechanism and motor if they do not have an overload protection relay.

Key parameters to consider when choosing a pump

To select the most suitable pump for your operation, there are a number of key parameters to consider. The first step is to determine the type of pump installation and how the pump will be used in the system. In addition, it is important to take into account the flow rate of the pumped liquid (l/min or m³/h), the total supply pressure (bar), as well as the height of the liquid column under the pump suction pipe (NPSN). The list of key parameters that must be taken into account when choosing a pump also includes the nature of the pumped substance (chemical composition, density, viscosity, pH, temperature), as well as the level of suspended solids in it and the degree of abrasiveness. In addition, the level of supply voltage and frequency of the network for connecting the motor, as well as the type of transmission mechanism between the motor and the pump, should be taken into account.

Design Features

• Durability. The screw is driven by an electric motor and does not come into contact with inner surface pump housing. This reduces friction to a minimum, which ensures a long service life.
• The medium moves in the pump with a constant axial flow direction. Thanks to this, the pump will output the product in an even flow, without pulsations. The pump has low noise pollution. Also, since the moving parts of the pump have low energy, the starting torque and vibration will have low values.
• The pump has high suction capacity.
• In order to ensure safe work pump, motor, piping system, all pumps increased power equipped with safety valves. If operating pressure exceeds maximum pressure, for which the system is designed (for example, a discharge pipeline), the safety valve is activated and the excess product will be directed through the bypass back into the suction chamber.

Advantages of a screw pump

Screw pumps have a number of advantages over other types of pumping units. So, unlike centrifugal pumps, screw pumps pump liquid with a smooth, non-pulsating flow, which allows you to avoid mixing the liquid and preserve its structure.

Unlike impeller pumps, self-priming screw pumps work better with thicker substances, and also have output pressures of up to 4-24 bar.

Compared to piston and plunger pumps, the advantage of screw pumps is the uniform supply of liquid, as well as the ability to pump mixtures of liquid and solid phases without damaging solids.

Among a number of advantages of screw pumps, it should be noted the high self-priming ability of these installations, as well as the simplicity of the design, which makes the pump convenient to service. The pump consists of three main parts: a stainless screw, a rubber race and a shaft seal. The fluid supply in a screw pump is proportional to the rotation speed, which ensures easy adjustment of pump parameters in the presence of a frequency drive. The cage design with self-adjusting gap ensures high pressure pump with a small size. As the pressure increases, the gap between the working surface of the screw and the cage remains constant.

Like other types of volumetric pumps, screw pumps have the ability to self-prime liquid from a depth of up to 10 meters. In addition, screw pumping units have an optimally balanced mechanism and, as a result, low noise levels. These types of pumps are unpretentious in operation.

Industrial Applications

The first models of screw pumps appeared in the 1920s and 10 years later they were used in production. Maximum indicator the operating pressure of pumps of this type can be up to 30-35 MPa.

Screw pumps are used for pumping liquids of various viscosities, gas, steam, and their mixtures. As a result, screw pumps are widely used in waste treatment, tobacco production, textile and paper industries, metal processing, food and chemical industry.

Since the 1980s, screw pump installations have been actively used in oil production and are still one of the most promising technologies in this industry.

Screw pumps are used for pumping petroleum products without mechanical impurities: fuel oil, oil, butter, diesel fuel, paraffin and other liquids with lubricating properties.

Sanitary single screw eccentric pumps have been developed especially for the food, chemical and pharmaceutical industries. These products have a classic configuration with hinged sealed units, which ensures the strength of the unit, as well as ease of operation and maintenance.

In systems autonomous water supply, as well as the functioning of systems for pumping various liquids, different ones are used. For wells and wells in the private sector, I most often use submersible models, which also include a screw pump for a well. This type of equipment is widely used not only in everyday life, but also in industry due to its simple and practically trouble-free design.

Screw pumps, also called screw pumps, operate using a simple mechanism based on a rotating screw (screw) located inside a cylindrical or cone-shaped housing. The supply and movement of liquid inside the working chamber occurs due to the constant movement of the screw. During the continuous movement of the auger, grooves on its surface force the liquid to move only forward, preventing it from flowing back. Thus, submersible screw pumps maintain a constant water pressure in the system without increasing the operating pressure in the chamber.

Rice. 1 Screw pump device

Features of the functioning of screw models of pumping equipment involve their immersion directly into the working environment - into a well or well. This is explained by the fact that such a design of the equipment does not allow it to work on the so-called. Idling. For stable operation The unit needs a constant fluid level, and without access to the working medium, the equipment simply stops.

Advantages and disadvantages of technology

Screw borehole pump(or centrifugal - as it is also called) is considered one of the preferred types of pumping equipment for supplying water to an autonomous water supply system, as well as in production for pumping and circulating various liquids - petroleum products, liquefied gas, aggressive working environments with a high content of chemical reagents.

The main advantages of submersible screw pumps are:

• high performance;
• ease of maintenance;
• no noise during operation;
• ability to work with working environments of varying quality.

The last point is one of the most important for many users of pumping equipment. While other models are quite sensitive to the composition of the working medium and can fail even with a small inclusion of sand in the water, screw pumps are insensitive to water contamination and can work even with heavily contaminated and even viscous media. This is one of the most critical parameters for many well owners, where even coarse filters cannot cope.

Compactness is another advantage that screw pumps for wells have. Usually this submersible pumps, geometric parameters which coincide with the well parameters. Most often, the size of the cylindrical body of the equipment does not exceed 12-15 cm in diameter. At the same time, due to the principle of operation - the creation of centrifugal force and turbulence in the working chamber, screw units show high productivity.

The latter directly depends on the rotation speed of the screw: the higher it is, the more water capable of pumping the unit in a unit of time. Standard models For home use capable of maintaining a stable water level in the system at up to 1500-2000 liters of liquid per hour.

Disadvantages of screw pumps

This equipment has a number of disadvantages, which you also need to know about before choosing screw models:

• high price;
• fixed working volume;
• inability to work “idle”.

When choosing screw type dirty water pumps, the user must be willing to pay the seller a large amount compared to others standard types equipment. The average cost of one model, depending on the manufacturer, is several hundred dollars for imported equipment. You can also take domestic models, for example “Malysh”, “Vodomet”, “Belamos” and others. But the market leaders both in Russia and abroad are foreign trade marks, such as Grundfos, Gadrena, Aquatica, Werk and others.

Equipment classification

All screw pumps for wells are divided into standard and deep. The former are suitable for installation in shallow wells and boreholes, for example, for extracting water from sandy aquifers. Such models have lower productivity and are usually installed at a depth of no more than 20-25 meters. The deep well pump has a longer body and auger and is intended for installation in artesian wells, the drilling of which reaches several hundred meters in depth. Such models are characterized by greater productivity and, accordingly, a higher price.

In answer to the question of which screw-type pump to choose for a well, you need to take into account the parameters hydraulic structure. The depth of the water surface, as well as the facility’s need for water supply, are the main technical factors influencing the choice of unit. You should also take into account the power of the equipment itself, because it will require a constant power supply to operate.

Deep and standard screw electric pumps consume an average of 1.5 kW of energy per hour, which will allow them to be connected to a standard 220V power source. But manufacturers recommend selecting a separate source of electricity for pumping equipment and additionally protecting it with a circuit breaker.

A screw pump, or as it is also called a screw pump, is one of the varieties of rotary gear pumps. The pressure of the injected liquid in it is created due to its displacement by one or more screw metal rotors rotating inside the stator.

A screw pump can be easily obtained from gears by increasing the angle of their teeth and reducing the number of gear teeth.

Working principle of auger pump

Due to the movement of liquid between the surface of the housing and the screw grooves along the axis of the screw, it is pumped. The screws engage with their protrusions into the grooves of the adjacent screw and thereby prevent the liquid from moving backwards.

Scope of application of screw pump

It is used for pumping steam, gas, their mixtures and liquids of varying degrees of viscosity.

Screw pumps were first introduced into production in 1936. Their simple design allows you to work, including in the presence of mechanical impurities with viscous fluids at pressures up to 30 MPa. Such characteristics are important when solving various practical problems.

Screw pump installations in large quantities are used in wells for the extraction of methane from coal seams to pump water from there. They are also suitable for water, oil and other gas wells.

Design features of screw pumps

In order to improve the quality of seals and reduce the number of leaks, screw pumps use conical or cylindrical elastic casings. The conical screw is reliably pressed by the spring and pressure from the pumped liquid, which significantly reduces leakage. However, pumps with elastic casings can withstand much less pressure than their counterparts with metal casings. A rigid casing is also suitable for a pump with a conical screw.

The most common type of screw pumps is three-screw pumps.

In practice, they have found the most widespread use.

Their characteristic advantages include:

• uniform supply of liquid (gas, steam);
• the ability to pump liquids with solid inclusions without damaging them;
• ability to self-absorb liquids;
• without many injection cascades it is possible to obtain high outlet pressure;
• low noise level during operation;
• good balance of the mechanism.

The disadvantages of this type are:

• high cost and complexity of pump manufacturing;
• inability to adjust the working volume;
• inadmissibility of empty use (without pumped liquid).

The operating principle of screw pumps

Modern screw pumps, according to their operating principle, are classified as volumetric rotary hydraulic machines. The working bodies are screw pair with internal gearing. The moving element of the working pair, the screw (rotor), performs planetary motion in the cage (stator).

The cage has an internal helical surface with a pitch twice the screw pitch. Being in constant contact, the cage and the screw form several closed cavities along the length of the screw - cage. When the screw rotates, the cavity on the suction side increases in volume and a vacuum is created in it, under the influence of which the cavity is filled with the transported medium. Further rotation of the screw moves the cut-off volumes of the transported medium towards the injection side.

At a set screw rotation speed, the speed of movement of the transported medium and the productivity that screw pumps have during operation are constant, because the flow area of ​​the screw and the holder remains unchanged.

Screw (screw) pumps are positive displacement pumps, the design of which allows for the creation of stable pressure and allows for adjustment of performance without loss nominal pressure. Screw pumps have a long service life, high efficiency, reliable and versatile when working with a wide range of tasks.

A screw pump is a device in which the pressure of the injection material is created by displacing the pumped liquid by one or more screw metal rotors that rotate inside a stator made of an elastomer in the appropriate shape.

The production of screw (screw) pumps requires precise manufacturing of parts, such as the working pair - rotor and stator, in the development and manufacture of which special high-precision equipment is used. Computer calculation using special programs - guarantee High Quality, which increases the service life of the equipment and reduces energy consumption during pump operation.

Screw pumps are used to work both with thick, viscous and viscous masses, and when pumping low-viscosity products. Depending on the design of the pump and its material performance, it is possible to pump resins, pastes, oils, food products, abrasive or even aggressive liquids so that the particles included in their composition are not crushed or destroyed when mixed with the base liquid.

Screw pumps are designed to operate in food production, mining or chemical industry, processing Wastewater in the municipal and industrial sphere, petrochemical production, pumping out sludge deposits, for work in gas and oil production, shipbuilding, wherever reliable and simple equipment is required for continuous operation, unpretentious in operation and subject to simple maintenance and repair. The applications for this type of pump are almost endless, thanks to its special design, materials used, technical features and special operating mechanisms.

Advantages of screw pumps

• The most uniform fluid flow of any positive displacement pump. No pulsation;
• Pumping liquids containing solids, impurities and abrasives, multiphase media with a high gas content;
• Pumping products with low and high viscosity (1 mPa*s to 5 million mPa*s);
• Pumping aggressive (pH from 1 to 14) and toxic media;
• Screw pumps are self-priming;
• The pressure does not depend on the speed of the pump (capacity adjustment);
• Quiet operation;
• Easy to maintain.

Screw screw pumps have a wide range of applications due to their design features, ability to pump dissimilar liquids and other significant advantages over other types of pumps.

Screw screw pump and its features

Such features of a screw screw pump as a valveless design, the ability to change the direction of flow of the pumped type of liquid and the direct dependence of performance on the number of engine revolutions allow this species pumps carry out pumping of various types of liquids. The list of liquids that a screw screw pump can pump is constantly growing. The rotor-stator pair plays the role of the main working part of a pump of this type. The metal rotor is made in the form of a screw and is located inside the cage, that is, the stator. When the rotor rotates, the volume of the cavities inside this pair changes, therefore, the liquid begins to move along the axis of the pump itself through displacement due to the rotation of the rotor. In this case, a suction effect is created in the cavities by changing the volume.

What liquids can a screw pump handle?

Capable of pumping dissimilar liquids, which are characterized by various characteristics. It is capable of pumping abrasive, emulsion, heterogeneous liquids, as well as liquids containing solid particles. The viscosity of the pumped liquids can reach a million centipoise, and the temperature can reach nine hundred degrees in continuous operation and 1200 degrees in intermittent operation.

Where are screw pumps used?

Screw screw pump can be used in various types industry. In heavy industry, these pumps are used to pump anti-corrosion agents and siliceous suspensions. Latex, paints, and silicones are also pumped. IN Food Industry fermentation wort, honey or vegetable pulp, juices, fats, etc. are pumped. When processing milk, milk, condensed milk, sour cream and yogurt are pumped, processed cheeses And so on. Screw pumps are also widely used in the cosmetics industry when pumping creams, oils and various cosmetic solutions, as well as liquid soap and shampoos. Screw pumps are widely used in construction for pumping out groundwater, transporting river water containing sand. Similar pumps are also used for water purification. Pumps are used to dose the supply of flocculants, polymers, polyelectrolytes, demineralized water and various chemicals.

Based on materials from optovik.net