Sewage pumps come in many forms: submersible and dry. The most common dry sewage pumps are W-type horizontal sewage pumps and WL-type vertical sewage pumps. Mainly used to transport urban sewage, feces or liquids containing fiber. For the medium of solid particles such as paper scraps, the temperature of the conveyed medium is usually not more than 80°C.
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Because the conveyed medium contains fibers that are easy to entangle or bunch. Therefore, the flow channel of this kind of pump is easy to be blocked. Once the pump is blocked, the pump will not work normally, and even the motor will be burned, resulting in poor sewage discharge. It has a serious impact on urban life and environmental protection. Therefore, blocking resistance and reliability are important factors for the quality of sewage pumps. Like other pumps, the impeller and the pressurized water chamber are the two core components of the sewage pump. The pros and cons of its performance also represent the pros and cons of the pump performance, the anti-clogging performance of the sewage pump, the level of efficiency, and the cavitation performance. The anti-abrasion performance is mainly guaranteed by the two components of the vane pump and the pressurized water chamber.
1. Impeller structure type: The impeller structure is divided into four categories: blade type (open type, closed type), swirl type, flow channel type, (including single flow channel and double flow channel) spiral centrifugal type, open type The semi-open impeller is easy to manufacture. When the impeller is blocked, it can be easily cleaned and repaired. However, in long-term operation, under the abrasion of particles, the gap between the blade and the side wall of the pressurized water chamber will increase, thereby increasing the efficiency reduce. And the increase of the gap will destroy the pressure difference distribution on the blade. Not only produces a large amount of vortex loss, but also increases the axial force of the pump. At the same time, due to the increase of the gap, the stability of the liquid flow in the flow channel is destroyed, causing the pump to vibrate. This type of impeller is not easy to transport the content. For media with large particles and long fibers, in terms of performance, this type of impeller has low efficiency. The highest efficiency is about 92% of that of an ordinary closed impeller, and the head curve is relatively flat.
2. Swirl impeller: The pump adopts this type of impeller, because the impeller is partially or completely retracted from the flow passage of the pressurized water chamber. Therefore, the non-clogging performance is good, the particle passing ability and the long fiber passing ability are strong. The particles flowing in the pressurized water chamber are driven by the vortex generated by the rotation of the impeller. The suspended particles themselves do not generate energy, but only exchange energy with the liquid in the flow channel. In the flow process, the suspended particles or long fibers do not contact the blades, and the blades are more abraded. There is no situation that the gap is enlarged due to abrasion. In the long-term operation, it will not cause the problem of serious decline in efficiency. Pumps with impellers are suitable for pumping media containing large particles and long fibers. In terms of performance, the efficiency of the impeller is relatively low, only equivalent to about 70% of the ordinary closed impeller, and the head curve is relatively flat.
3. Closed impeller: This type of impeller is normally more efficient. And in the long-term operation, the situation is relatively stable. The axial force of the pump adopting this type of impeller is small, and auxiliary vanes can be set on the front and rear cover plates. The auxiliary blades on the front cover can reduce the vortex loss at the impeller inlet and the wear of the sealing ring caused by particles. The auxiliary vane on the back cover not only plays the role of balancing the axial force, but also prevents suspended particles from entering the mechanical seal cavity to protect the mechanical seal. However, this type of impeller has poor non-blocking properties and is easy to entangle, and is not suitable for pumping untreated sewage media containing large particles (long fibers).
4. Flow channel impeller: This kind of impeller is a bladeless impeller. The flow channel of the impeller is a curved flow channel from the inlet to the outlet. Therefore, it is suitable for pumping media containing large particles and long fibers. Good blocking resistance. In terms of performance, the efficiency of this type of impeller is not much different from that of an ordinary closed impeller, but the lift curve of the pump with this type of impeller drops steeply. The power curve is relatively stable, and it is not easy to cause overpower problems, but the cavitation performance of this type of impeller is not as good as that of the ordinary closed impeller, and it is especially suitable for use in pumps with pressure inlets.
5. Spiral centrifugal impeller: The blades of this type of impeller are twisted helical blades that extend axially from the suction port on the conical hub body. This type of impeller pump has the functions of a positive displacement pump and a centrifugal pump. When the suspended particles flow through the blades, they will not hit any part of the pump, so it has good non-destructive performance. The damage to the conveyed material is small. Due to the propelling effect of the screw, the suspended particles can pass through, so the pump adopting this type of impeller is suitable for pumping the medium containing large particles and long fibers, as well as the medium with high concentration. It has obvious characteristics when there are strict requirements on the damage of the conveying medium.
The most common type of sewage pump room is a volute. In the built-in submersible pump, radial guide vanes or flow channel guide vanes are often used. There are three types of volutes: spiral type, ring type and intermediate type. The spiral volute is basically not used in the sewage pump. The annular pressurized water chamber is often used in small sewage pumps because of its simple structure and easy manufacture. However, due to the emergence of an intermediate (semi-spiral) pressurized water chamber, the application range of the annular pressurized water chamber has gradually become smaller. Because the intermediate pressurized water chamber has both the high efficiency of the spiral and the high permeability of the annular pressurized water chamber. It has received more and more attention from manufacturers.