Selection of impeller design
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I am an amateur who started working with pumps later in my career; I have dealt with centrifugal pumps and screw pumps from imported brands such as Grundfoss, Alfa Laval, and Alvital. To achieve technical professional sales, I also studied the pipe losses in water supply systems as well as the losses associated with the series and parallel connection of pumps. I am now in contact with chemical pumps used to transport a ferrous complex solvent that contains sulfur particles (with a particle size of around 280 microns) at a mass ratio of less than 1%; the pH value of this substance is at most 10. My client mentioned that sulfur tends to crystallize, and it turns out that the impellers used in such pumps are of the open-type design. In their actual use, they found that the open impeller is not the best option either, and they want to know whether an open impeller or a closed impeller is better Open impellers are further divided into fully open and semi-open types; which one is suitable? This truly leaves me unable to find an answer, so I have to turn to the forum and ask for help from kind-hearted people with expertise in this field.
Fine particles in liquid can be clarified using a closed impeller. For mud, waste residues, and large-particle viscous media, use an open impeller. A semi-open type that lies between the two options is available. Select the appropriate impeller based on the operating conditions.
Solvent for complexed iron containing 1% sulfur particles (with a particle size of about 280 microns): either a semi-open or closed system can be used; aside from the impeller, what’s more important is the mechanical seal. 、
This post was last edited by wghrxy on 2018-4-19 at 16:28. We are indeed considering different types of mechanical seals as well, but the issues need to be addressed one by one. Currently, a double-seal PLAN54 is being used; I’m not sure if there is a more suitable option. And as for whether there is any special design for the internal flushing flow channel of the mechanical seal, I’m powerless to tell
The particles in the medium are still relatively small; therefore, a closed impeller can be used. However, given the tendency of sulfur to crystallize, it is recommended that the equipment run continuously. Once it stops operating, the pump body should be cleaned to prevent sulfur from entering the sealing chamber and causing the sealing springs to fail.
Yes, sulfur tends to stick to the machine seal springs, causing failures and leaks; as a result, some owners have changed from dual seals to single seals in order to make it easier to remove and clean the seal when the machine is shut down. Personally, I don’t think this is a good solution – it might work, but it’s not worth promoting.
Regarding on-site use, what makes people unsatisfied with open-type designs is that, under current conditions, open-type designs are the most convenient for cleaning and least prone to crystallization. If there are concerns regarding efficiency or flow rate and head, the impeller can be redesigned to meet the specific requirements of on-site use. Nevertheless, it is still recommended to use open-type or semi-open-type impellers; closed-type impellers are not advised. If cleaning is not carried out promptly when the system stops operating, crystallization and blockages can occur. Additionally, if the inlet and outlet valves cannot be closed properly, this too can lead to crystallization and blockages, thereby causing more problems.
Oh, I’ve received your suggestion, thank you
We have many actual cases regarding the operating conditions in this area, and in most of them the pump equipment remains unmaintained for two to three years!