The sludge conveying equipment manufacturer pointed out that the eccentric screw pump is usually used in the sludge pumping system, and the main working parts are the eccentric screw (rotor) and the screw village (stator). When the motor drives the pump shaft to rotate, the screw rotates on its own axis and rolls along the inner surface of the bushing, thus forming a sealed chamber of the pump. Advancing a pitch, with the continuous rotation of the screw and the rod, the transported sludge is pressed in a spiral form from one sealed chamber to the other, and finally the pump body is extruded. The consumable parts of the pump, the stator and the rotor, are usually replaced every 2 months to half a year.

The eccentric screw pump is suitable for short distance, small flow, low conveying pressure and continuous conveying of sludge. The screw pump transports sludge without turbulent pulsation, and has no shear force on the medium.

The screw pump has a simple structure and low one-time investment. In the case of ensuring that the materials are clean and single, there is no problem in stable operation. In engineering applications, the working pressure of the screw pump should be controlled at 1/2-1/3 of the rated pressure; the rotational speed of the pump should be controlled at a relative sliding speed of 0.5 m/s or less; Generally no more than 100m; vertical critical height is 50m, theoretical pressure can reach 4.8MPa. The drawback of the screw pump itself is that the stator and the rotor form a moving closed cavity conveying medium by sliding friction, so the stator and the rotor are extremely wearable. The sediment concentration of sewage sludge in China is large, which will increase the wear rate of the stator and the rotor, which not only increases the maintenance cost, but also directly affects the normal operation of the sludge transportation system. The sediment concentration in the sludge directly affects the service life of the screw pump.

The screw pump has a small adaptability to the moisture content of the sludge. The water content of many sewage sludges is as low as about 75%, and such low moisture content will reduce the pumping capacity by at least 20-40%. As the pumping capacity is reduced, the delivery volume of the screw pump will also decrease, and it is impossible to ensure continuous operation according to the designed flow rate.

Since sludge viscosity is an important parameter affecting transportation, the viscosity is proportional to the concentration, that is, the higher the concentration, the higher the viscosity. The sludge concentration is higher and the viscosity is also increased. In the case of high viscosity, the efficiency of the screw pump is greatly reduced, and the operating energy consumption is greatly improved.

For example, if the sludge contains flexible fibrous substances (such as hair, plant stems, rods, plastic bags, etc.), after passing through the front end of the pump body, the rotor will still be wound around the rotor, causing the sealed chamber to leak, and the system working pressure can generally be reduced by 50-90. %. The sludge will inevitably contain a certain amount of flexible fibrous material, and the structural characteristics of the screw pump itself determine that it cannot guarantee continuous and stable transportation.