Page 240 - Know and Understand Centrifugal Pumps

Failure Analysis of Mechanical Seals

Straightness
and roundness
of the shaft
.003" Maximum.

U
Figure 14-22

pump wear rings, and the motor and coupling. The same reading
should be taken on the motor end of the shaft.
With the indicator fixed to the volute mounting collar, place the needle
on the end of the shaft (Figure 14-23). Push and pull the shaft axially
by hand (see the arrows). This will read the tolerance in the axial
bearing. This tolerance affects the spring tension holding the faces
together. If the play in the axial bearing is too loose, the movement can
open or even crush the seal faces.

t
Axial Play nC

.003" Maxima d
nr-----
I I

U

Fiaure 14-23

223