Problems with multi-stage pump assembly
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Now, the assembly is carried out by starting from the discharge section, where the balance disc is fitted against the balance ring; then the middle section, guide vanes, and impeller are installed one by one. When adjusting the clearance, once the nuts are tightened, the rotor does not shift out of place and cannot rotate either. Upon disassembling to check the parts, their dimensions turn out to be correct. One unit has already been assembled and all tests have been completed…… Several attempts at assembly and disassembly have shown no issues. I would appreciate it if everyone could share their experience
Apply dark purple paint to the surfaces of areas prone to wear due to small gaps; rotate the assembly disc, and then disassemble it to check for signs of wear
That’s exactly what they plan to do, TMD
Check the other end of the balance disc, and adjust the serial quantity at each stage while moving the axial edge. Are there shims between the links at all levels as well? Thickness?
The wheel won’t rotate once the nut is tightened; it’s likely due to friction between the impeller and the guide vanes, or friction caused by deformation of the mouth ring. Only disassemble and inspect
This post was last edited by 3983596_FPPZ on 2018-11-1 19:17. Those are just rough assembly and testing methods. The proper method should be to refer to the drawings, install a portion of the components and check the dimensional tolerances and cumulative tolerances, as well as the axial and radial runouts. Special attention should be paid to the position of the balance discs and balance drums; any signs of wear or friction must be repaired immediately. It is absolutely not acceptable to assemble the components with defects or in a rough manner. Thermal installation or forced compression should be used with caution (except for bearings), as neither too loose nor too tight fit between the components is desirable. The tightening force of the bolts should be applied symmetrically and in stages, especially in pumps where flat gaskets are used for sealing between stages. Mark what needs to be marked, and apply dark purple where it’s necessary; it’s a task that requires precision and skill, as well as specific strategies and plans. Without some experience, it’s really difficult for ordinary people to handle. I’m afraid the shaft will bend.
The reason has been found; one impeller wasn’t installed properly, although they claimed it was installed correctly. Damn, I’ve been looking for it for days; I even started doubting myself
There are two main reasons: first, radial dimension errors (accumulated errors resulting from spindle bending and radial runout of the impeller’s mouth ring); second, axial issues (long lengths of the spacers between impeller stages, as well as improper installation of the impeller and guide vanes).