Assembly problems of segmented multi-stage centrifugal pumps
Thread Content
Assembly issue with segmented multi-stage centrifugal pumps: During assembly, it was found that the ring at the inlet of the first impeller on the rotor keeps coming into contact with something whenever it rotates to a certain position. Do any of you have any methods to solve this problem?
Check whether the lower ring and the mounting area are deformed, and whether they are concentric with the shaft and impeller. :)
Check whether any impurities have entered, and measure the runout of the shaft impeller
Based on what you’ve described, the pump shaft should not be bent. Check whether there is any local deformation in the pump’s mouth ring; also, apply some red lead to the mouth ring and check it again after that.
In my opinion, the impeller may have been damaged by impurities that got inside it during operation. It’s necessary to check whether the impeller and the ring are deformed or scratched; if the impeller is made of 304 material, there’s a high chance of deformation, and such damage cannot be repaired using a file – a lathe is required for that. Another possibility is that when installing each stage of the multi-stage pump, its position must be the same as it was before disassembly, otherwise the impeller and the pump casing will not be aligned properly. It’s important to make marks before disassembly.
It seems that in the situation described by the poster, there are high points or misalignment in the shell’s mouth ring, as well as misalignment, high points in the impeller’s mouth ring, or a bent shaft; these conditions cause the assembly to rotate to a fixed angle, resulting in scraping.
First, check whether the roundness of the mouth ring is satisfactory; then check whether the roundness of the surface where the rotor contacts the mouth ring is acceptable. If these conditions are met, it is necessary to measure whether the shaft is bent. In the case of multi-stage pumps, there is a higher likelihood of the shaft being bent
Get on the lathe and check whether the shaft is bent, especially at the shaft head – it’s likely that this is the cause.
The bearing housings of segmented multi-stage pumps are generally located at both ends of the pump; if the shaft is bent, it is likely that the ring at the impeller inlet of the middle stages will get scratched； If it is the first-stage impeller retaining ring that needs lapping, it is very likely that there are high spots on the shell mouth ring!
Check whether the ring at the inlet of the first-stage impeller and the ring in the first-stage pump casing are deformed.
Is this pump horizontal or vertical?