The principle of operation of a 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, they are reliable and simple in design. Consider the features, characteristics and application of this equipment.
Device 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 rotary main element, the stator spiral always has one more turn (run).
The working chamber of the pump is divided into several compartments. Their differentiation is carried out using sites that are protected from water penetration, located between the stator and the rotor along the line of contact. Due to the design features, these sections open and close alternately.
The adjustment of the amount of pumped 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 that aggregate with deep wells) or cast iron.
- Rotor.
- Stator part.
- Suction pipe.
- Outlet pipe.
- Sealants.
- Hinges.
The principle of operation of a screw pump
The work 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, which does not allow the fluid to move in the opposite direction.
Appointment
Due to its principle of operation, screw pumps are used in various economic and industrial sectors. The most popular areas of use of the specified equipment:
- Food industry. These units in the process of food production play the role of dispensers.
- Building sector. Devices supply working solutions intended for pouring floors and roofs.
- Arrangement of wells. Pumps remove contaminated water with impurities. The screw type unit can be operated with clean water or liquid with sand.
- Chemical field. 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.
Advantages and disadvantages
The productive principle of a screw borehole pump is not its only advantage. Among other advantages, the following points are noted:
- the ability to work with liquids with high viscosity, while creating a greater pressure than impeller analogues;
- high efficiency of units, the indicator of which is approaching 70%;
- the ability to handle mixtures involving a large amount of solid impurities;
- formation of pulsating moments observed in the operation of most other equipment is excluded;
- self-priming operation with a maximum depth of fluid intake of up to 8.5 meters;
- reduced noise, compact size;
- high reliability indicator, easy maintenance, good maintainability.
Like all types of pumping equipment, screw units are not without drawbacks. Firstly, this is the high price of the device, and therefore not all small farms and private entrepreneurs can allow their operation. Secondly, the design does not provide for the possibility of adjusting the amount of pumped liquid.
Varieties
Despite the similar principle of operation, screw pumps are divided into several types according to design features. According to the device, the equipment in question is divided into three main categories. The first variety is screw modifications. They are focused on pumping a significant amount of mixtures, which include aggressive chemical and abrasive substances.
The screw equipment functions equally effectively in a vertical and horizontal position. This equipment is often used to service wells and deep wells. Among the advantages of this category are simplicity of design and relatively low price.
Rod and vacuum versions
The device and principle of operation of a rod-type screw pump allows it to be used in enterprises engaged in the extraction and refining of oil and similar substances with high viscosity. The equipment design includes a wellhead configuration oil seal, a rotary column and a surface drive unit. Among the advantages of units of this configuration is high performance. The downside is the high cost.
A vacuum screw pump, the principle of which is based on the operation of a pair of rotors, is also intended for pumping liquids of various viscosity levels. The movable elements rotate in different directions, so that the processed composition first enters the area between the working chambers and the cylinder, and then is fed into the exhaust outlet.
It is worth noting that the efficiency and performance of the equipment in question, regardless of type, are mainly affected by the correct operation. Therefore, before purchasing the unit, you need to make sure that it matches the selected action.
Seal types and main operating parameters
Deep screw pumps can be equipped with several types of seals: gaskets, cuffs, double or single end elements or a magnetic coupling.
The following are the main parameters of the operational plan specific to the equipment in question:
- performance indicator - 0.03-500 cubic m / h;
- ultimate pressure for standard execution - 6-48 bar;
- the number of steps is from one to eight;
- the viscosity parameter of the processed fluid is 1-3000000 cps;
- the size of solid impurities to a maximum of 150 mm.
It should be noted that the maximum pressure is practically unlimited, it depends on the number of steps that are mounted in series. Some manufacturers have specimens that can handle pressures up to 240 bar.
Comparison of centrifugal and screw models
Not always, users can clearly understand which pump in domestic use is better - centrifugal or screw? Both modifications differ in design features and areas of operation.
A centrifugal pump is a rather expensive equipment that copes well with the water supply of a suburban cottage or cottage. Such units are focused on the maintenance of well wells. The design of the device includes a wheel fixed on the shaft, which serves to supply water up. Such a system is suitable exclusively for the treatment of clean water, has a high efficiency, and uses electricity within reasonable limits. The advantage of centrifugal pumps is their 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 these variations, you should focus on its final destination. That is, a centrifugal system will be the best option for supplying clean water, and a screw analogue for irrigation.
What is the difference between blade 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 this type of equipment include such moments:
- uniform supply of liquid mixture over the entire working distance;
- the presence of self-priming options;
- well-balanced mechanism of the main action;
- the effectiveness of work with compositions oversaturated solid inclusions;
- durability and reliability of all elements.
Among the minuses are increased friction of the mating parts and not always effective cooling.
Blade devices are classified as household appliances. The advantages of these units include:
- simplicity of operation and maintenance;
- the ability to connect multiple devices to one pipeline;
- compact dimensions and low weight;
- reasonable price of the main components and spare elements;
- high efficiency cooling system.
Disadvantages of blade modifications
If we compare the principle of operation of a screw pump for a well with a similar parameter of a blade design, the latter option has a number of significant drawbacks. They include:
- inability to work with contaminated water;
- low efficiency;
- frequent overheating of units with narrowing of flow channels;
- poor balance and stability of the structure.
An important feature of a vane pump is its performance. This indicator is very dependent on the quality of the processed fluid and the power of the pump itself. The lack of the last parameter resets all possible pluses. Therefore, when choosing equipment, special attention should be paid to its power indicators, taking into account the length of the highway and the area of the building intended for maintenance.