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Screw pump in sewage treatment application process

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Screw pumps are widely used in the transportation of water, wet sludge and flocculant liquids in sewage treatment plants due to their characteristics of variable delivery, strong self-priming ability,
Screw pumps are widely used in the transportation of water, wet sludge and flocculant liquids in sewage treatment plants due to their characteristics of variable delivery, strong self-priming ability, reversibility, and the ability to transport liquids containing solid particles. . Screw pump selection should follow the principles of economy, reasonableness and reliability. If the design is poorly selected, it will cause troubles for future use, management, and maintenance. Therefore, using a practical and reliable screw pump in accordance with actual production needs can not only ensure smooth production, but also reduce repair costs.
    First, the screw pump speed selection
    The flow rate of the screw pump has a linear relationship with the rotation speed. Compared with the low-speed screw pump, the high-speed screw pump can increase the flow rate and the lift, but the power is obviously increased. The high rotation speed accelerates the abrasion between the rotor and the stator, and must ensure that The screw pump fails prematurely, and the fixed rotor length of the high-speed screw pump is very short, which makes it easy to wear, thus shortening the service life of the screw pump.
    By reducing the speed through a speed-reducing mechanism or a stepless speed-regulating mechanism, the speed is maintained within a reasonable range below each minute of three hundred revolutions, and the service life can be extended several times as compared with a high-speed screw pump.
    Second, the quality of the screw pump
    There are many kinds of screw pumps on the market. Relatively speaking, the imported screw pumps are designed with reasonable materials and high quality. However, the prices are relatively high, some services are not in place, the accessories are expensive, and the long order period may affect the normal production. run.
    Most of the domestic production of imitation of imported products, product quality varies greatly, in the selection of domestic production of products, when considering its cost-effective, choose low-speed, long lead, transmission components, material quality, long life rating of the product.
    Third, ensure that debris does not enter the pump body
    Solid debris mixed in the wet sludge will damage the rubber stator of the screw pump, so it is very important to ensure that debris does not enter the cavity of the pump. Many screw mills have installed a pulverizer in front of the pump. There are also installations of grid devices or screens to block debris from entering the screw pump, and the grid should be cleared in time to avoid plugging.
    Fourth, avoid breaking materials
    The screw pump must not be allowed to operate in the event of a broken material. Once it occurs, the rubber stator will produce high temperatures and burn out due to dry friction. Therefore, the crusher is in good condition, and the smooth grille is one of the necessary conditions for the normal operation of the screw pump. For this reason, some screw pumps also have a shut-off device installed on the pump body. When the cut-off occurs, due to the self-priming function of the screw pump, a vacuum will be generated in the chamber and the vacuum device will stop the screw pump.
How to better maintain the high pumping rate of the screw pump
    1. Acoustic level measurement should be performed to determine the relative depth of the liquid level and the pump inlet. If the liquid level is higher than the pump suction, it is impossible for the well to be mined at maximum production. If the gas interference affects the productivity, the liquid level is higher than the pump inlet; if the pumping volume is too large and the production is low, the liquid level should be at or near the pump inlet.
    2. The dynamometer measures the percentage of the pump fullness coefficient. The single-screw pump application integrated data acquisition system can simultaneously obtain the motor power and indication data. One of the main uses of the dynamometer chart is to diagnose how the pump operates and analyze downhole problems. The use of a production level measurement combined with a dynamometer chart reveals whether the well was produced at maximum production, whether the height of the liquid column was greater than the depth of the pump inlet, whether the pump was not fully charged, and whether the free gas migrated upward along the casing annulus.
    3, diagnosis of low energy efficiency wells. The method of diagnosis is to determine the total efficiency of the pumping system, and to determine the total efficiency, only the power of the input prime mover is measured, the downhole production pressure is measured, and the accurate production test data. The general efficiency of beam-type pumping systems should be around 50%. If less than this, the performance should be improved. Techniques that increase overall efficiency include maintaining high volumetric efficiency (pump size matching wellbore injection volume, eliminating air interference, using evacuated controllers or timers to control pumping), and replacing excessively large motors.
    4. Downhole gas separation. Invalid pump operation is often caused by air interference, and screw pump problems can be diagnosed through acoustical level measurements and dynamometer diagrams. It is best to place the pump inlet below the fluid entry section, and to use it above the gas separator. If the seat of the valve seat is arranged at least 10 ft below the bottom of the fluid entering the section, effective gas separation can take place in the annulus, at which time the sleeve acts as the outer cylinder of the separator. However, the condition of the well often does not allow the pump to be placed below the fluid entry layer. Consider a downhole gas separator. Conventional gas separators consist of a fluid entry section (such as a perforating pup joint), an outer cylinder (such as a tubing with a plug at the bottom), and a sealing tube at the bottom of the pump.
Single-screw pump oil and gas multiphase mixing and flow analysis
    The single-screw pump work is that the rotor of the same fixed profile meshes in the stator of the corresponding inner profile to form a special contact line to separate the stator cavity. The contact line is called a seal line. When the rotor rotates on a certain track, its sealing line moves axially, and the stator cavity also moves axially, that is, volume displacement. At this time, the sealing line disappears at one end, and the screw pump problem generates a new sealing line from the other end. , then push the media from one end to the other.
    Due to the use of a rubber-like stator with a good elasticity, the single-screw oil-air mixture pump requires a certain amount of interference in meshing with the rotor, and the metering screw pump produces a reliable seal. When the pump is working, the sealing line can effectively prevent the gas from passing through, so as to achieve the purpose of conveying gas; when the medium contains solid particles, if the solid particles are squeezed in the sealing line, the surface of the stator rubber is compressed due to the elasticity of the rubber stator, the solid As the particles pass over the seal line, the stator rubber springs back to its original shape, so that the single screw pump can achieve the purpose of containing trace amounts of solid particles in the medium.
    The single-screw oil-air mixture pump is suitable for the transportation of corrosive media, gas-containing media, sediment-containing solid particulate media and high-viscosity media. Gas content up to 95%, medium viscosity up to 50000mPa·S, solid content up to 60%, allowing solid particle diameter ≤3.5~32mm, flow rate is proportional to the rotation speed, can maintain the pressure stability at low speed and low flow rate, Has good regulation performance, easy to achieve automatic control.


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