Flowserve S-series PolyChem - Manual (Page 39)

USER INSTRUCTIONS POLYCHEM S-SERIES ENGLISH 71569207 11-08
Page 39 of 52
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6.9.4.3 Impeller balancing
Shaft whip is deflection where the centerline of the
impeller is moving around the true axis of the pump. It
is not caused by hydraulic force but rather by an
imbalance with the rotating element. Shaft whip is very
hard on the mechanical seal because the faces must
flex with each revolution in order to maintain contact.
To minimize shaft whip it is imperative that the impeller
is balanced. All open impellers manufactured by
Flowserve are balanced after they are trimmed. If for
any reason a customer trims an impeller, it must be re-
balanced. See note 1 under Figure 6-13 regarding
acceptance criteria.
6.9.4.4 Bearing housing/carrier
Prior to installing the shaft into the bearing housing,
check the following parameters.
Diameter/tolerance, at bearing surface
In order to ensure proper fit between the bearing
housing/carrier and the bearings, verify that the ID of
both the IB and OB bearing surfaces are consistently
within the minimum/maximum values shown in Figure
6-15. An inside caliper should be used to check
these ID dimensions in the bearing housing.
6.9.4.5 Power end
Assembled bearing housing, carrier, bearings, and
shaft.
Shaft/shaft sleeve run-out
Shaft run-out is the amount the shaft is “out of true”
when rotated in the pump. It is measured by
attaching a dial indicator to a stationary part of the
pump so that its contact point indicates the radial
movement of the shaft surface as the shaft is rotated
slowly. If a shaft sleeve is used then shaft sleeve
run-out must be checked. It is analogous to shaft
run-out. Measurement of shaft run-out/shaft sleeve
run-out will disclose any out of roundness of the
shaft, any eccentricity between the shaft and the
sleeve, any permanent bend in the shaft, and/or any
eccentricity in the way the shaft or bearings are
mounted in the bearing housing.
Shaft run-out can shorten the life of the bearings and
the mechanical seal. The following diagram shows
how to measure shaft/shaft sleeve run-out. Note that
both ends need to be checked. The run-out should
be 0.025 mm (0.001 in.) FIM or less.
Runout
Radial deflection - static
Radial movement of the shaft can be caused by a loose
fit between the shaft and the bearing and/or the bearing
and the housing. This movement is measured by
attempting to displace the shaft vertically by applying an
upward force of approximately 4.5 kg (10 lb) to the
impeller end of the shaft. While applying this force, the
movement of an indicator is observed as shown in the
following diagram. The movement should be checked
at a point as near as possible to the location of the seal
faces. A movement of more than 0.05 mm (0.002 in.) is
not acceptable.
Deflection
Shaft endplay
The maximum amount of axial shaft movement, or
endplay, on a Durco pump should be 0.03 mm
(0.001 in.) and is measured as shown below.
Observe indicator movement while tapping the shaft
from each end in turn with a soft mallet. Shaft
endplay can cause several problems. It can cause
fretting or wear at the point of contact between the
shaft and the secondary sealing element. It can also
cause seal overloading or underloading and possibly
chipping of the seal faces. It can also cause the
faces to separate if significant axial vibration occurs.
Endplay
6.9.4.6 Seal chamber
Assembled power end and rear cover.
Face squareness to shaft
Also referred to as “Seal chamber face run-out.” This
run-out occurs when the seal chamber face is not
perpendicular to the shaft axis.