Pumps are widely used in conveying water, wet sludge and flocculant liquid in sewage treatment plants because of their variable conveying capacity, self-priming ability, reversibility and ability to transport liquids containing solid particles. Screw pump selection should follow the economic, reasonable and reliable principles. If the design selection of ill-considered, will give future use, management, maintenance trouble, so the selection of a practical production needs, reasonable and reliable screw pump can ensure the smooth production, but also reduce repair costs . Now we use screw pump some experience described below: First, the selection of screw pump speed Screw pump flow and speed into a linear relationship, relative to the low-speed screw pump, screw pump with high speed although it can increase the flow and lift, but the power was significantly increased, high speed accelerated wear between the rotor and stator, must make Early failure of the screw pump, screw rotor and high-speed fixed rotor length is very short, easy to wear, thus shortening the life of the screw pump. Through reducer or stepless speed regulation mechanism to reduce the speed, the exploration speed maintained at a reasonable range of three hundred revolutions per minute, and high-speed operation of the screw pump, the service life can be extended several times. Second, the quality of screw pump Now on the market more types of screw pumps, relatively speaking, the imported screw pump design, excellent material, but the higher prices, some services are not in place, parts prices, ordering a long period of time, may affect the normal production run. Most of the domestic production of imported products imitation, product quality varies greatly in the choice of domestically produced products, considering its cost-effective time, the choice of low speed, long lead, transmission parts of good quality, long life rating of the product. Third, to ensure that debris does not enter the pump body Solid impurities mixed in the wet sludge will damage the rubber material stator of the screw pump. Therefore, it is very important to ensure that the sundries do not enter the cavity of the pump. Many sewage plants add a shredder before the pump and some install Grille device or filter, block debris into the screw pump, grill should be promptly cleared to avoid clogging. Fourth, to avoid broken material Screw pump is never allowed to run in the case of broken material, once occurred, the rubber stator due to dry friction, instantaneous heat generated and burned, so the grinder intact grille smooth is one of the necessary conditions for the normal operation of the screw pump is In this case, some screw pumps are still installed in the pump body off material shutdown device, when there is a broken material, due to its self-priming screw pump features, the cavity will have a vacuum, the vacuum device will make the screw pump stop running. Fifth, to maintain a constant export pressure Screw pump is a positive displacement rotary pump, when the outlet is blocked, the pressure will gradually increase, so that the pressure exceeds the predetermined value. At this time the motor load increased dramatically. Transmission machinery related parts load will exceed the design value, severe motor burn occurs, the transmission parts broken. In order to avoid damage to the screw pump, generally installed at the outlet of the screw pump bypass relief valve to stabilize the outlet pressure to maintain the normal operation of the pump.