Tolerance design of multistage radial flow submersible pumps

Abstract

Axial play between the impeller and its casing is
one of the critical dimensions in a multistage submersible
pump assembly. The axial play is introduced in the assembly
using a coupling that connects the motor and pump sub
assemblies. The length of the coupling could not be standardized
by the industry where this analysis was conducted.
Tolerance analysis is conducted on the pump subassembly
to identify the causes of variation of coupling
length. It has been found that there are n possible tolerance
loops in a n stage pump. Since the tolerance design is to be
conducted for the worst case, the assembly condition that
yields the largest tolerance loop has been considered for
the analysis. The methodology currently adopted by industry
to overcome the problem of variation of coupling
length involves machining operation during the assembly
stage. It results in unreasonably longer assembly time. The
concept of selective assembly is suggested in this paper to
overcome the problem of coupling length variation.