The screw pump mainly consists of five parts: the spiral part, the lower bearing, the upper bearing, the driving device and the pumping groove, and the auxiliary equipment.
(1) The spiral part is the main body of the screw pump, generally consisting of welding steel blades outside the central steel pipe. Usually, the diameter of the steel pipe is about 1/2 of the outer diameter of the spiral, and the thickness of the blade is 5-10 mm. For corrosion protection, the blade can be used. Made of stainless steel, the blade adopts three-headed spiral or double-ended spiral, which is generally rotated at a speed of 30-120r/min, and forms a rising sealing area with the pump tank to achieve the purpose of lifting sludge or sewage.
(2) The lower bearing is immersed in the sewage, so it is also called the underwater bearing, which bears 1/2 radial load. The housing is a sealed housing with a radial ball bearing. The housing is filled with grease, the upper part has a gasket and stuffing box to prevent the infiltration of sewage and mud, and the mechanical seal is used to protect the bearing. In order to prevent the effects of thermal expansion and contraction due to the length of the spiral, the bearing bracket is floating.
(3) The upper bearing is completely working above the water surface, by the casing, radial ball bearing
(4) The screw pump has a simple structure and does not require auxiliary pumps such as a vacuum pump or a lubricating cooling water pump. The spiral blades are open for installation and maintenance is very convenient. Impurities smaller than the pitch can pass without being blocked by the sludge. The speed of the spiral pump is low, there is no cavitation of the high-speed pump, and the wear is small. Even if it is worn, it is easy to repair, so the service life is long and the reliability is high. When the sludge is transported, the integrity of the activated sludge flocs is not damaged, which is beneficial to the activity of the return sludge after entering the aeration tank.
(5) The disadvantage of the screw pump is that it has a large volume and a low lift. It is not suitable for high-lift pumping stations and where the water level changes greatly. The outlet side cannot be equipped with pressure pipes, and can only be open channels or gravity flow pipes. It must be installed obliquely, the volume of the pump body is also large, so the floor space is large, and the tank body is open and volatile odor is easily generated.

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