Application of screw pump in sewage treatment process

Due to its variable capacity, self-priming ability, reversible, and ability to transport liquids containing solid particles, screw pumps are widely used in sewage treatment plants for conveying water, wet sludge and flocculant liquids. . The selection of screw pump should follow the principle of economy, reasonableness and reliability. If the design and selection are not well thought out, it will bring trouble to the future use, management and maintenance. Therefore, choosing a screw pump that is reasonable and reliable according to actual production needs can ensure smooth production and reduce repair costs. Now we will introduce some of the experiences in the application of screw pumps as follows:

First, the speed of the screw pump is selected
The flow rate of the screw pump is linear with the rotational 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 rotational speed accelerates the wear between the rotor and the stator, which must make The screw pump fails prematurely, and the high-speed screw pump has a short stator length and is extremely wearable, thus shortening the service life of the screw pump.
The speed is reduced by the speed reduction mechanism or the stepless speed regulation mechanism, and the rotation speed is maintained within a reasonable range of less than three hundred revolutions per minute. Compared with the high speed running screw pump, the service life can be extended several times.

Second, the quality of the screw pump

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At present, there are many kinds of screw pumps on the market. Relatively speaking, the imported screw pump has reasonable design and excellent materials, but the price is high, the service is not in place, the price of accessories is high, and the order period is long, which may affect the normal production. run.
Most of the domestically produced products are imitation imported products, and the quality of the products is mixed. When selecting domestically produced products, when considering the cost performance, the products with low speed, long lead, good transmission parts and long service life are selected.

Third, to ensure that debris does not enter the pump body
The solid impurities mixed in the wet sludge will cause damage to the rubber material stator of the screw pump, so it is very important to ensure that the debris does not enter the pump cavity. Many sewage plants install the pulverizer in front of the pump, and some installations are also installed. The grille device or the filter screen blocks the debris from entering the screw pump, and the grille should be cleaned in time to avoid blockage.

Fourth, avoid breaking materials
The screw pump is never allowed to run under the condition of breaking the material. Once it happens, the rubber stator burns due to dry friction and instantaneously generates high temperature. Therefore, the crusher is intact and the grille is unblocked, which is one of the necessary conditions for the normal operation of the screw pump. Therefore, some screw pumps also have a material shut-off device installed on the pump body. When the material is broken, due to the self-priming function of the screw pump, a vacuum is generated in the cavity, and the vacuum device stops the screw pump.

Fifth, maintain a constant export pressure
The screw pump is a positive displacement rotary pump. When the outlet end is blocked, the pressure will gradually increase so as to exceed the predetermined pressure value. At this time, the motor load increases sharply. The load of the parts related to the transmission machinery will also exceed the design value. In severe cases, the motor will burn out and the transmission parts will break. In order to avoid damage to the screw pump, a bypass relief valve is usually installed at the outlet of the screw pump to stabilize the outlet pressure and keep the pump running normally.

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