|
Don't open a pump for general inspection |
|
Don't open on general inspection unless there
is definite evidence that the pump performance has fallen
of or unless noise or driver overload indicated internal trouble
.
|
| Great
care need be exercised in the dismantling operation |
|
Use care during a complete overhaul . With
horizontally split casing pumps, lift the upper half straight
up so as not to damage internal parts . Lift the rotor out
vertically to prevent injury to impellers , wear rings etc.,
Mark all parts as they are removed . Examine all parts and
important joints . Make records of all clearances and compare
with original clearances .
|
| Special
care is needed in examination and reconditioning of metal-to-metal
fits |
|
Take special pains to do the job right where
stationary parts such as casing rings seat in the casing
|
| Clean
casing waterways thoroughly and repaint |
|
This should be done during a complete overhaul
. Examine waterways for corrosion or erosion . If severe signs
of wear are apparent , consult the manufacture on the possibility
of substituting more resistant material .
|
| New
gaskets should be available for complete overhaul |
|
Except for some special designs , most centrifugal
pump casings have gaskets which may be damaged on opening
the pump . New gaskets should be the same thickness as the
original . Inner gasket edges must be trimmed accurately along
the internal portion of pump waterways . Gasket mounting surfaces
should be absolutely clean before applying the gasket .
|
| Examine
impellers for corrosion , erosion or cavitation |
|
Here again , if the wear is severe , a better
material may be available . If serious cavitation signs are
apparent , it may be possible to relocate the pump and improves
suction conditions or obtain a specially designed impeller
which will operate satisfactorily under existing suction conditions
|
| Check
concentricity on new wearing rings after mounting on impeller
|
|
If necessary , make a slight cut after this
check to obtain a true circle .
|
| Check
all parts mounted on rotor |
|
Check for concentricity and trueness of faces
against bores . This will prevent bowing of the haft when
tightening up the shaft nuts .
|
| Restore
shaft or shaft sleeves to proper service condition at stuffing
box |
|
In some cases , It may be possible to rebuild
these surfaces by welding or metallizing . Generally , however
, such practice is not fool proof and new parts are to be
preferred .
|
| Exercise
great care in mounting anti-friction bearing on shaft |
|
It is far safer practice to heat the bearings
slightly and expand the inner race than to force it on the
shaft . If the bearing is forced on the shaft , the force
should be applied by an arbor press or by gently hammer blows
alternately on opposite sides of a tubular sleeve held against
the inner race .
|
| Keep
a complete record of inspections and repairs |
|
Such records should form a basis of preventive
maintenance which will reduce the frequency and cost of maintenance
work .
|
| |
