The impeller and pressure chamber of sewage pumps are the two core elements of sewage pumps. The advantages and disadvantages of its performance represent the superior performance of the pump. The anti clogging performance, efficiency, and cavitation performance of the sewage discharge pump are guaranteed by two major components: the vane pump and the pressure chamber.
The working principle and characteristics of sewage pumps belong to a type of unobstructed pump, mainly used for transporting urban sewage, feces or liquids containing fibers. The medium containing solid particles is usually transported at a temperature not exceeding 80 ℃. Due to the presence of fibers that are prone to entanglement or clumping in the conveyed medium. Therefore, it is easy to block the pump flow channel. Once the pump is blocked, it will not work properly and even burn out the motor, resulting in poor drainage. It has a serious impact on urban life and environmental pollution discharge. Therefore, an important factor in anti clogging and reliability is the quality of the sewage pump.
In terms of performance, sewage pumps have a steep head curve and a relatively flat power curve.
The common type of pressure chamber used in sewage pumps is the volute, and radial guide vanes or flow channel guide vanes are often used in embedded submersible pumps. There are three types of snail shells: spiral, ring, and intermediate. Spiral volutes are basically not used in sewage pumps. Circular pressurized water chambers are commonly used in small sewage pumps due to their simple structure and easy manufacturing. However, due to the emergence of intermediate (semi spiral) pressure chambers, the application range of annular pressure chambers has gradually become smaller. Due to the high efficiency of spiral and high permeability of annular pressurized water chambers, intermediate pressurized water chambers have attracted increasing attention from manufacturers.
Below are the types of impellers for sewage pumps:
1. Type of impeller structure:
The structure of impellers can be divided into four categories: blade type (open, closed), swirl type, channel type, and (including single channel and double channel) spiral centrifugal type. Open semi open impellers are easy to manufacture and can be easily cleaned and repaired when blockage occurs inside the impeller. However, in long-term operation, the clearance between the blades and the sidewall of the pressurized water chamber will increase due to particle abrasion, resulting in reduced efficiency. And increasing the gap will disrupt the pressure distribution on the blades. Not only does it generate a large amount of vortex loss, but it also increases the axial force of the pump. At the same time, due to the increased gap, the stability of the liquid flow in the channel is disrupted, causing the pump to vibrate. This type of impeller is not easy to transport media containing large particles and long fibers. In terms of performance, this type of impeller has low efficiency, with a high efficiency of about 92% of that of ordinary closed impellers, and a relatively flat head curve.
2. Rotating impeller:
Pumps using this type of impeller have some or all of the impeller retracted from the pressure chamber flow channel. So the non clogging performance is good, and the passing ability of particles and long fibers is strong. The particles flow in the water pressure chamber and are propelled by the vortex generated by the rotation of the impeller. The suspended particles themselves do not generate energy, but exchange energy with the liquid in the flow channel. During the flow process, suspended particles or long fibers do not come into contact with the worn blades. The situation of excessive blade wear is relatively mild, and there is no increase in clearance due to abrasion. It will not cause serious efficiency decline during long-term operation. Pumps using this type of impeller are suitable for pumping media containing large particles and long fibers. In terms of performance, the efficiency of this impeller is relatively low, only about 70% of that of a regular closed impeller, and the head curve is relatively flat.
3. Spiral centrifugal impeller:
The blades of this type of impeller are twisted spiral blades that extend axially from the suction port on the conical hub body. This type of impeller pump has both the functions of a positive displacement pump and a centrifugal pump. When suspended particles flow through the blades, they do not hit any part of the pump, so it has good non-destructive properties. Less destructive to the conveyed material.
Due to the propulsion effect of the spiral, suspended particles have strong passability, so pumps using this type of impeller are suitable for pumping media containing large particles and long fibers, as well as high concentration media. It has obvious characteristics in situations where there are strict requirements for the destruction of the conveying medium.
4. Flow channel impeller:
This type of impeller belongs to bladeless impellers, and the impeller channel is a curved channel from the inlet to the outlet. So it is suitable for pumping media containing large particles and long fibers. Good anti blocking performance. In terms of performance, this type of impeller has high efficiency and is not much different from ordinary closed impellers, but the head curve of the pump with this type of impeller drops sharply. The power curve is relatively stable and not prone to over power issues, but the cavitation performance of this type of impeller is not as good as that of ordinary closed impellers, especially suitable for use in pumps with pressure inlets.
5. Closed impeller:
This type of impeller has a normal high efficiency. In long-term stable operation, pumps using this type of impeller have less axial force, and auxiliary blades can be installed on the front and rear cover plates. The auxiliary blades on the front cover plate can reduce the vortex loss at the impeller inlet and the wear of particles on the sealing ring. The secondary blades on the rear cover plate not only serve to balance axial forces, but also prevent suspended particles from entering the mechanical seal chamber and provide protection for the mechanical seal.
However, this type of impeller has poor non clogging properties, is easy to entangle, and is not suitable for pumping untreated sewage media containing a large amount of particles (long fibers).
In summary, regardless of the series of sewage pump impellers, it is only a combination of different types of impellers and different types of pressure chambers according to the requirements of the conveying medium and installation, as long as the impellers and pressure chambers can achieve optimized configuration. The various performance of the pump will be guaranteed.
