Installation and operating instructions Wilo
–
SCPV pumps
24
9.4.4 Shaft & keys
The sleeve should be examined to see if it
is grooved or generally worn. The outside
diameter of the sleeve should be measured
and a comparison made with the bore of
the bearing bush through which the sleeve
passes. The amount of clearance between
the two can thus be checked to determine
whether or not it is within acceptable
limits.
9.4.5 Bearings
9.4.5.1 Bush Bearing
Under normal conditions the outside dia. of shaft
sleeve are uniformly loaded and provided that an
adequate supply of pumped liquid is maintained
through Flushing line, the bearing will usually
operate until wear is approximately 150% the
original design clearance without detriment to
mechanical performance of the pump. The most
positive indication of the loss in bearing
efficiency will be given by an increase in level of
vibration. This increase may be gradual and
difficult to detect or sudden and prominent. But
when an increase is detected the reason must be
investigated because it is a symptom that the
bearings may require renewal even if the
allowable degree of wear previously indicated
has not been reached.
The Finocot
‘
B
’
bearing bush should be inspected
for:
Excessive clearance by measuring clearance
between O/D of shaft sleeve and bush
bearing. If clearance has become excessive
or if bearing is not usable the same must be
renewed. After renewing the bushes, check
clearances and maintain the record
NOTE:
An incorrect fit can allow one or both of the
bearing tracks to creep, which will affect the
running accuracy and the assembly and
dismantling of a pump. Creep is the slow
rotation of one track relative to its seating, it is
undesirable since the spindle and the bore of
the bearing or the housing and the outside
diameter of the bearing may become worn.
Creep is not due to friction within a bearing but
is generally caused due to radial loads rotating
or oscillating in respect to fixed point on the
track.
If creep has occurred the interference fit of the
bearing must be restored, either by metal
spraying or chromium plating and regrinding
the seating to the correct diameter;
interference fits must not be simulated by
knurling, scoring or distortion of the seating on
which creep has occurred because such
practices are ineffective and creep will quickly
reoccur. Even if the bearing is prevented from
creeping it will usually be distorted by the
seating, and failure will result caused by local
overloading and high frequency vibration.
Examine the abutment. Abutment for ball bearings
must be flat and square with the axis of rotation.
The radius at the root of an abutment must be
smaller than the corner radius of the track located
against the abutment. The edge of the abutment
must be reduced or chamfered; a burred edge can
tilt or distort a bearing track.
If after inspection, the bearing is re-usable,
completely coat all parts with rust preventive oil,
working it well into the internal parts of the
bearing. Wrap in clean greaseproof paper and store
until required for replacement or refit on to the
spindle if needed. In case of immediate use,
coating of rust preventive oil is not necessary.
9.4.5.2 Thrust Ball Bearing
Clean all the components using clean white spirit. Do
not use chlorinated solvents such as
trichloroethylene and carbon tetrachloride because
they introduce a corrosion risk when used on ferrous
materials. If these chemicals are present for any
reason a `No Smoking' rule must be strictly enforced.
Inspect the bearing as follows
Visually inspect the bearing. The balls, the inner and
outer tracks must all be free from chipping, cracks,
abrasions or discolouration.
Check that the parts of the cage are firmly fixed
together.
Visually inspect the bore for any sign of damage.
Burrs or any scratches caused during bearing
withdrawal should be carefully removed by hand
application of a fine oilstone, the treatment being
confined to the minimum possible area.
Visually inspect the outside diameter for signs of
fretting, any stains may be carefully polished off, but
abrasion must be kept to the absolute minimum that
is required, followed by cleaning.
Check that bearing rotates freely and smoothly. If
there is any doubt regarding the serviceability of the
bearing it should be renewed.
Inspect the Bearing Housing as follows
Visually inspect the bore for any signs of fretting, any
stains may be carefully polished off, but abrasion
must be kept to the absolute minimum that is
required, followed by cleaning.
Where fretting has occurred, bearing and housing
should be clean and dry, and trial assembled. It is a
transitional fit and may be described as a sucking fit
without any detectable clearance or play between
the outer race and the housing bore. Any assembly
that achieves this may be considered as being
acceptable, provided the bearing is serviceable.
Assemblies that do not achieve this degree of fitting
may improve if a new bearing is fitted, or Wilo
Mather & Platt may be consulted.
Examine the abutment. Abutment for ball bearings
must be flat and square with the axis of rotation. The
radius at the root of an abutment must be smaller
than the corner radius of the track located against
the abutment. The edge of the abutment must be
reduced or chamfered; a burred edge can tilt or
distort a bearing track.
If after inspection, the bearing is re-usable,
completely coat all parts with rust preventive oil,
working it well into the internal parts of the
bearing. Wrap in clean greaseproof paper and store
