Sewage pump belongs to one kind of non-clogging pump, which has many forms: diving pump and dry pump. At present, the most common type of diving pump is WQ submersible sewage pump, and the most common type of dry sewage pump is W horizontal sewage pump and WL vertical sewage pump. Mainly used to transport municipal sewage, faeces or liquids containing fibers. Solid particles such as paper scraps are usually conveyed at temperatures not more than 80 degrees Celsius. Because the medium being transported contains fibers that are easily wound or bunched. Therefore, the flow passage of this kind of pump is easy to be blocked, once the pump is blocked, it will make the pump not work properly, or even burn down the motor, thus causing blockage. It has a serious impact on urban life and environmental protection. Therefore, blockage resistance and reliability are important factors for the quality of sewage pumps.
Like other pumps, impeller, pressure chamber are the two core components of sewage pump. Its performance also represents the performance of the pump, anti-clogging performance of sewage pump, efficiency, and cavitation performance, anti-abrasion performance is mainly guaranteed by two parts, vane pump and pressure chamber. Following is an introduction:
Impeller structure type: Impeller structure is divided into four categories: blade type (open type, closed type), swirl type, flow channel type, and spiral centrifugal type (including single channel and double channel). Open semi-open impeller is easy to manufacture and clean up and repair when blockage occurs in the impeller, but in long-term operation, it is easy to maintain the impeller. Under the abrasion of particles, the clearance between the blade and the side wall of the water pressure chamber will be increased, thus the efficiency will be reduced. And the increase of clearance destroys the pressure difference distribution on the blade. It not only produces a large number of eddy losses, but also enhances the axial force of the pump. At the same time, due to the increase of clearance, the stability of liquid flow in the flow passage is destroyed, resulting in the vibration of the pump. This type of impeller is not easy to transport medium containing large particles and long fibers. In terms of performance, this type of impeller is inefficient and most efficient. The ratio is about 92% of the common closed impeller, and the head curve is relatively flat.
Swirl impeller: Pump with this type of impeller, because the impeller partially or totally shrinks the pressure chamber runner. Therefore, the non-clogging performance is good, the ability of passing particles and the ability of passing long fibers are strong. Particles move in a pressurized water chamber driven by eddy currents generated by impeller rotation. Suspended particles do not generate energy by themselves, but exchange energy with liquid in the flow passage. In the process of flow, suspended particles or long fibers do not contact with the blades, the wear of the blades is lighter, and there is no gap increased due to wear. In the long run, the efficiency will not be seriously reduced. The pump with this type of impeller is suitable for pumping medium containing large particles and long fibers. From the performance point of view, the efficiency of the impeller is low, only about 70% of the ordinary closed impeller, and the head curve is relatively flat.
Closed impeller: This type of impeller has higher normal efficiency. The pump with this type of impeller has smaller axial force and can install auxiliary vanes on the front and rear cover plates. The secondary vanes on the front cover plate can reduce the eddy loss at the impeller inlet and the wear of particles on the sealing ring. The secondary blades on the back cover plate not only balance the axial force, but also prevent suspended particles from entering the mechanical seal chamber to protect the mechanical seal. However, the impeller has poor plug-free performance and is easy to winding. It is not suitable for pumping large particles (long fibers) and other end-treated sewage media.
Runner impeller: This kind of impeller belongs to vaneless impeller. The impeller runner is a curved channel from the inlet to the outlet. Therefore, it is suitable for pumping medium containing large particles and long fibers. Good plugging resistance. In terms of performance, the efficiency of this type of impeller is not much different from that of ordinary closed impeller, but the head curve of this type of impeller pump drops sharply. The power curve is relatively stable, and it is not easy to cause the problem of overpower. However, the cavitation performance of the impeller is not as good as that of the ordinary closed impeller, especially suitable for the pump with pressure inlet.
Spiral centrifugal impeller: The blade of this impeller is twisted helical blade, extending along the axis from the suction port on the conical hub body. The pump with this impeller has the function of both volume pump and centrifugal pump. The suspended particles flow through the blade and do not impact any part of the pump, so it has good nondestructive performance. It is less destructive to the conveyor. Because of the propelling effect of screw, the passing ability of suspended particles is strong, so the pump with this type of impeller is suitable for pumping medium containing large particles and long fibers, as well as medium with high concentration. It has obvious characteristics when there are strict requirements for the destruction of conveying media.
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