What is a screw pump？
The screw pump is a kind of transportation equipment that relies on the mutual meshing of the eccentric screw and the rubber stator to move the material.
It is a kind of positive displacement pump with a long history. Compared with other pump products on the market, the characteristics of the screw pump are stable flow without pulsation, and it can handle a wide range of media, including high viscosity and solid particles.
How does the screw pump work?
When the screw pump is running, the screw (rotor) is driven by the motor, and the rotary motion is performed in the stator (elastic bushing). The rotor (screw) and the stator (elastic bushing) form several sealed cavities that do not communicate with each other. When the screw rotates, the sealed cavity moves from the suction end to the discharge end in the axial direction, and the medium continuously flows from the suction end to the discharge end in the cavity. The rotor of the screw pump can be one, two, or three.
Screw pump advantages and disadvantages
1. Advantages of screw pump:
1). Wide range of pressure and flow.
2). transport wide range of liquid types and viscosities;
3). Because the inertial force of the rotating parts in the oil-free screw pump is low, a high speed can be used;
4). Good suction performance and self-priming ability;
5). The flow is uniform and continuous, and the vibration is small;
6). Compared with other pumps, it is less sensitive to incoming gas and dirt;
7). Solid structure, easy installation, and maintenance;
2. Disadvantages of screw pump:
The processing and assembly requirements of the screw are relatively high.
What is the difference between a single and a twin screw pump?
The single-screw pump can literally be understood as having only one screw. The single-headed male helical rotor rotates eccentrically in a special double-headed female helical stator (the stator is soft), can swing back and forth along the center line of the pump, and is always meshed with the stator, forming a space that separates the suction cavity and the discharge cavity. Seal the cavity so that the pump can work efficiently.
The twin-screw pump literally means connecting two screws and connecting two sets of screws. There is no contact between the screws and no mechanical friction, so the service life will be relatively longer.
Compared with the single screw pump and the twin screw pump, each has its own advantages and disadvantages.
The single screw pump has the lowest volumetric efficiency and low-pressure resistance, but the conveying medium has the highest tolerance. It is suitable for conveying media with particulate matter, viscous slurry, etc., and the flow and pressure do not need to be too large.
The volumetric efficiency of the twin-screw pump is high, but the pressure is high. If the viscosity is low, the efficiency will decrease rapidly, the medium range of conveying is also very wide, the displacement is also large, and it is somewhat sensitive to particle size. The medium, such as fuel oil and crude oil, is generally used as a transfer pump when the flow rate is relatively large and the pressure is high.
Features of single screw pump:
- It can transport medium with high solid content;
- The flow is uniform and the pressure is stable, which is more obvious at low speeds;
- The flow is proportional to the speed of the pump, so it has good variable regulation;
- One pump can be used to transport media of different viscosity;
- The installation position of the pump can be inclined arbitrarily;
- It is suitable for conveying sensitive items and items that are easily damaged by centrifugal force;
- Small size, lightweight, low noise, simple structure, and easy maintenance.
Features and advantages of twin screw pump:
- The conveying liquid is stable, with no pulsation, no stirring, small vibration, and low noise.
- It has strong self-priming performance. When multiphase is mixed, the gas content is not higher than 80%, and the sand content is not higher than 500g/m3.
- The external bearing structure adopts independent lubrication, which can transport various non-lubricating media.
- Driven by synchronous gears, the two rotors do not contact each other, even if they are idling for a short time.
- The pump body is equipped with a heating jacket, which can transport various clean or low-viscosity or high-viscosity media containing small solid particles (generally, the particle diameter is less than 0.12-0.2mm)
- With the correct selection of materials, it can even transport many corrosive media.
- Double suction structure, there is no axial force on the rotor.
- The shaft end adopts mechanical seal or bellows mechanical seal, which has the characteristics of long service life, less leakage, and wide application range.
Why are screw pumps used?
The screw pump is a widely used general mechanical equipment, and in petroleum, mining, national defense, and other fields. It also has good anti-cavitation performance, which not only reduces the excavation depth of the pump chamber of the screw pump, but also does not corrode the screw pump, and the operation of the screw pump is also very good. Stable, the life of the screw pump is also very long.
1. Handle complex components, high viscosity
The screw pump can handle high-concentration media with complex components, such as thin mud water, waste sewage, glue, jam, etc. These media have high viscosity, and the general pump products will inevitably block when transporting these media, while the screw pump can be free It has the advantages of certain self-priming ability, low noise, high efficiency, long life, and reliable operation.
2. Handle sewage media and also clean water or oil-class medium
The screw pump can handle the media that the general water pump cannot handle, such as sewage containing particulate debris, sewage, river pond mud, wastewater discharge from enterprise production, etc. In addition to these sewage media, the screw pump can also pump clean water and clear oil class medium. On the whole, the adaptability of the screw pump to the medium is quite wide, so the use is also very wide. For customers with special process requirements, you can also contact the manufacturer in advance to customize the screw pump in batches.
3. Widely used in the oil exploration industry
In addition to industrial production and urban sewer systems, screw pumps are also widely used in the oil exploration industry. Compared with other transportation equipment, screw pumps have low one-time investment costs, good adaptability to oil, and can be used on the oil field ground. The driving system is formed, and then dynamic oil recovery is carried out on this basis. Its working characteristics and technology can avoid the adverse effects of traditional technology on production, and can fully guarantee the oil production output.
To sum up, why is the screw pump widely used, its structural characteristics make it have more special advantages than other pumps and a wider range of applications. Progressive cavity pumps are known for their good qualities such as simple and durable design, high efficiency, ability to pump raw water even if it contains a certain amount of solids and debris, and reliability over a lifetime.
Is priming needed in a screw pump?
The self-priming capacity of the screw pump is relatively strong. Generally, it can pump the medium without priming the pump in advance. However, in order to avoid idling and dry grinding and reduce the friction of the machine seal, it is recommended to prime the pump in advance, and only need to prime the pump once before use. That’s it, and you don’t need to do this extra operation for subsequent use.
Growing Applications for Screw Pumps
The use of the screw pump is extremely wide, and the selection of various types of screw pumps is comprehensive. In terms of the medium to be transported, its ability to transport various media exceeds that of all other pumps. For different types of screw pumps, their characteristics and application range are different.
In general, screw pumps can be used in the following fields:
1. Water Supply Plants, Sewage Plants, Chemical Solutions
Quantitative dosing in water supply plants, transportation, and discharge of sediment, sludge transportation after dewatering in sewage plants, feeding of plate and frame filter presses, and addition of chemical agents, such as flocculant, lime milk, and other chemical solutions.
2. Shipbuilding Industry
lubricating oil pump, fuel oil transfer pump, and cargo oil pump. The ship transports fuel oil, sweeps warehouses, removes floating oil at sea, discharges sewage and dirty oil to shore, and loads and unloads various materials.
3. Oil fields, Coalfield
Extraction and transportation of crude oil, heavy oil, oil, gas, sand, and other mixtures in onshore and offshore oil fields. In recent years, it has been especially successful in extracting the mixture of crude oil and water deep underground, and the mixture of coal gas and water in the coalfield, thus greatly reducing the cost of oil production and coal gas mining in Jicheng. The screw pump injects polymer into the formation to increase oilfield recovery.
4. Food Industry
Conveying various viscous pastes, emulsions, various ointments, cosmetics, etc. Conveying food raw materials, dairy materials, carbonated beverages and seasonings, straw thick starch, cooking oil, honey, fruit pulp, fruit juice, cream, surimi, minced meat, fermented viscous liquid, concentrated distiller’s grains, grain product residue, various recommended sauces, pulp and mucus containing lumpy solids, etc.
5. Ceramic industry, High Territory Production
Spraying and conveying of cement mortar, lime mortar, paint, and other pastes. The transportation of slurry, porcelain oil, and refractory clay suspension in the production of ceramic industry, the production and use of coal-water slurry. Delivery of raw material slurries in high territory production.
6. Mine, Chemical Fiber
Discharged the underground and slurry water that contains solid particles in the mine to the surface. Transportation of various suspensions, emulsions, polymers, dyes, organic materials, inorganic materials, grease, various colloids, synthetic fibers, viscose, and nylon powder. High-viscosity ink for wallpaper.
Delivery of syrups, health products, and pharmaceuticals.
Conveying pulp, adhesives, auxiliaries, etc.
9. Oil Depot Terminal
Unloading oil pump, loading pump, unloading pump, loading pump.
10. Thermal Power Plant
Heavy oil transfer pump, heavy oil fuel oil pump.
11. Hydropower plant
Lubricating oil pump.
12. Gas Filling Station
LPG tanker loading and unloading, tank dumping, etc.
Lubrication pump, oil supply pump, fuel injection pump, water-glycol and other delivery pumps