The principle of operation of the screw pump allows the pumping of liquids and compositions with a high viscosity index. Such devices are used in industry, including the metalworking and chemical industries. These units have a long working life, are reliable and simple in design. Consider the features, characteristics and application of this equipment.
Design and design features
Regardless of the nuances of the principle of operation of a screw pump, its main element is the rotor. This part has a cylindrical configuration, as well as a spiral groove made in the form of a screw. The stator part is made in the form of a pipe, equipped with an elastomeric sleeve and a channel in the form of a spiral. Compared to the rotor core, the stator coil always has one more turn (start).
The working chamber of the pump is divided into several compartments. Their differentiation is carried out using areas that are protected from the ingress of water,located between the stator and the rotor along the line of their contact. Due to the nature of the design, these sections open and close alternately.
Adjustment of the amount of pumped out solution is made by changing the number of rotations of the rotor part. The frequency drive is directly involved in this process. The working elements of the pump are placed in a reinforced frame made of plastic, stainless steel (for models aggregating with deep wells) or cast iron.
- Rotor.
- Stator part.
- Suction connection.
- Outlet.
- Seals.
- Hinges.
The principle of operation of the screw pump
The operation of the equipment in question is based on the transportation of a liquid composition inside a special chamber along the helical axis. The last element is placed between the surface of the core and the screw channels by fixing the adjacent protrusions of the screws in the grooves. This design feature makes it possible to create a closed space inside the unit that does not allow the liquid to move in the opposite direction.
Destination
Due to its principle of operation, screw pumps are used in various household and industrial sectors. The most popular uses for this equipment are:
- Food industry. These units in the process of food production play the role of dispensers.
- Construction industry. Devices supply working solutions intended for pouringfloors and roofs.
- Well construction. Pumps remove polluted water with impurities. The screw type unit can be operated with clean water or liquid with sand.
- Chemistry. These devices are capable of pumping significant volumes of thick mixtures for their subsequent processing.
The popularity of equipment is determined by its high reliability and the ability to function effectively under high loads.
Strengths and weaknesses
The productive principle of operation of a screw borehole pump is not its only advantage. Among other advantages, the following points are noted:
- possibility to work with liquids with increased viscosity, while creating a greater pressure than impeller counterparts;
- high efficiency of units, the indicator of which is close to 70%;
- ability to handle mixtures containing large amounts of solids;
- excludes the formation of pulsating moments observed in the operation of most other equipment;
- self-priming operation with a maximum liquid intake depth of up to 8.5 meters;
- low noise, compact size;
- high reliability, easy maintenance, good maintainability.
Like all types of pumping equipment, screw units are not without drawbacks. Firstly, this is a high price of adaptation, and therefore not all small farms and privateentrepreneurs can allow their exploitation. Secondly, the design does not provide for the ability to adjust the amount of fluid pumped out.
Varieties
Despite the similar principle of operation, screw pumps are divided into several types according to design features. According to the device, the considered equipment is divided into three main categories. The first variety is screw modifications. They are designed to pump a significant amount of mixtures, which include aggressive chemicals and abrasive substances.
Auger equipment functions equally effectively in vertical and horizontal positions. This equipment is often used to service wells and deep wells. Among the advantages of this category are the simplicity of design and relatively low price.
Rod and vacuum versions
The design and principle of operation of a screw rod-type pump allows it to be used in enterprises engaged in the extraction and processing of oil and similar substances with high viscosity. The equipment design includes a wellhead configuration stuffing box, a rotary string and a surface drive unit. Among the advantages of the units of this configuration is high performance. Minus - high cost.
The vacuum screw pump, the principle of operation of which is based on the operation of a pair of rotors, is also designed for pumping liquids of varying degrees of viscosity. Movable elements rotate in different directions, due to which the processed compositionfirst enters the area between the working chambers and the cylinder, and then is fed into the exhaust gas outlet.
It is worth noting that the efficiency and performance of the equipment in question, regardless of type, is mainly affected by correct operation. Therefore, before purchasing the unit, you must make sure that it is suitable for the selected action.
Types of seals and main operating parameters
Deep screw pumps can be equipped with several types of seals: stuffing boxes, cuffs, double or single end elements or a magnetic coupling.
The following are the main parameters of the operating plan specific to the equipment in question:
- The performance index is 0.03-500 cbm/h;
- ultimate pressure for standard version - 6-48 bar;
- number of steps - from one to eight;
- treated fluid viscosity parameter - 1-3000000 cP;
- size of solid impurities to the maximum - 150 mm.
It is worth noting that the maximum pressure is practically unlimited, depending on the number of stages that are mounted in series. Samples available from some manufacturers up to 240 bar.
Comparison of centrifugal and screw models
It is not always possible for users to clearly understand which pump for domestic use is better - centrifugal or screw? Both modifications differ from each otherdesign features and areas of operation.
A centrifugal pump is a rather expensive equipment that does a good job of supplying water to a country cottage or cottage. Such units are focused on servicing well wells. The design of the device includes a wheel fixed on the shaft, which serves to supply water to the top. Such a system is suitable exclusively for the treatment of clean water, has a high efficiency, uses electricity within reasonable limits. The advantage of centrifugal pumps is long service life and reliability.
The operation of screw pumps is focused on industrial purposes. But sometimes it is used for domestic needs. In the latter case, when pumping water, the content of solid particles in it should not exceed 150 g / cu. m liquid.
When choosing pumping equipment among the indicated variations, one should be guided by its final destination. That is, a centrifugal system will be the best option for supplying clean water, and a screw analog for irrigation.
What is the difference between vane units?
Often a vane pump is considered one of the modifications of the screw version. This is not entirely true. Screw devices are usually used in industry. The advantages of equipment of this type include the following points:
- uniform supply of the liquid mixture over the entire working distance;
- presence of self-priming option;
- well balanced main action mechanism;
- work efficiencywith compositions supersaturated with solids;
- strength and reliability of all elements.
Among the minuses are increased friction of mating parts and not always effective cooling.
Blade devices are included in the household category. The advantages of these units include:
- easy operation and maintenance;
- possibility of connecting several devices to one pipeline;
- compact size and light weight;
- affordable price of main components and spare parts;
- high efficiency cooling system.
Disadvantages of paddle modifications
If we compare the principle of operation of a screw pump for a well with a similar parameter of a bladed design, the latter option has a number of significant drawbacks. They include:
- inability to work with contaminated water;
- low efficiency;
- frequent overheating of units when the flow channels narrow;
- poor balance and structural stability.
An important feature of a vane pump is its performance. This indicator is very dependent on the quality of the treated liquid and the power of the pump itself. The lack of the last parameter nullifies all possible pluses. Therefore, when choosing equipment, special attention should be paid to its power indicators, taking into account the length of the main line and the area of \u200b\u200bthe building intended for maintenance.
