Earlier we were discussing the basics of roller bearing & its various types and also ball bearing and its types, we have
also seen the bearing removal and cleaning procedure in our last post. Today we
will see here the basic procedure of bearing installation.
We will discuss here each and every step that must
be followed for securing the correct installation and better service life of bearing
and simultaneously we will also look here the importance of tools, installation
guidelines and other various factors such as cleanliness during bearing
installation.
So let us first see, what we will have to inspect
before going for bearing installation
Shaft and bearing housing condition
Before going for installation of bearing, we must
have to check the condition of bearing seat on shaft and seat in housing bore.
Shaft and bearing housing bore must be cleaned and there should not be any
dust, metal burr or any dent.
We must have to check the dimensions of bearing seat
in housing bore and diameter of bearing seat on shaft and these dimensions must
be within preferred tolerances provided by the manufacturer.
Seal condition
Sometime, it is observed that maintenance crew team members
replace bearings but they do not replace the seals. Seals are provided to avoid
the entry of dust, foreign particles and moisture in to the bearings. In my
point of view, whenever we go for replacement of bearings, we should also
replace the seals with new one of similar specifications.
Before replacement of
seals, we must have to inspect the seat of seals and there should not be any
sharp edges or metal burr as these sharp edges or metal burr will damage the
seals and allow the entry of dust, foreign particles and moisture in to the
bearings and finally we will not be able to secure the desired service life of
bearings just because of damage seals.
Seals provided next to the bearings will also avoid
the flow of lubricant out of the bearings.
Working area
Working area, surrounding area where bearing
installation job is being carried out, must be clean so that bearing
installation job could be carried out safely and successfully.
Tools and other resources must be clean before the
installation of the bearings.
We should not remove the bearings from its box until
we are ready for installation. After removing bearings from their box, we
should not remove the protective lubricants provided by the manufacturer over
the bearing surface as these lubricants are provided by the manufacturer to
avoid the damaging of bearings from corrosion or dust.
Shaft and housing fits
Selection of optimum shaft and housing fit is very
important factor for securing the long service life of a bearing. Type of fit
for shaft and housing depends on various factors such as operating temperature,
bearing type, load and material of shaft and housing.
Fit which is explained as the amount of interference
that should be available between mating parts e.g. shaft and bore of bearing or
bearing outer diameter and bore of housing.
Shaft and housing fits are divided in three types as
mentioned here
Loose fit
It will allow the easy installation of bearing but
we must have to note here that too loose fit will permit the bearings to slip
in the housing or on the shaft and may lead the vibration and noise during
operation and further premature failure of bearings.
Press fit
Press fit installation of bearings are quite difficult
but if followed the guidelines of manufacturer then it will surely provide the
long service life of bearings. If inner ring is press fit with shaft then it
will run with the shaft and if outer ring is press fit then outer ring will run
with the housing.
If we have to press fit the inner ring with shaft,
in this case shaft diameter will be slightly higher than the bore diameter of
bearing. If press fit is beyond the specified tolerance then it will eliminate
the internal clearance of bearing and hence rolling elements of bearing will
not be able to rotate smoothly and will lead the rising in temperature and
further premature failure of bearing will be there.
Transition fit
Transition fit means slight press fit i.e. the
amount of interference that should be available between mating parts, in this
case, will be between loose fit and press fit.
Mounting the bearing
Now we have idea about the various points that must
be considered before installation of the bearings. Now we will see here how a
bearing will be installed over the shaft with press fit. First of all we will lubricate
slightly the bearing seat on shaft with recommended lubricant.
We will start the installation of bearing with
rounded corner of bearing going first over the shaft and we will check here
that bearing is square over the shaft and bearing centre matches with the shaft
axis.
Now we will apply the pressure force to the ring of
the bearing which is being press fit and we will force the press fit race of
bearing against shaft shoulder.
For applying the pressure force over the press fit
race of bearing, we may use equipment named as arbor press as shown in figure.
We
can exert the pressure force here continuously and bearing installation could
be completed within short period of time. For inner press fit, we will have to
support the inner ring of bearing with the help of two flat bar or attachment
for supporting the inner ring of bearing.
Once the bearing inner race is properly supported,
we will check that bearing is in center or square over shaft. Now we will exert
the pressure force with the help of arbor press and we must have to take care
here about the pressure applying by the press because excessive pressure
applied by the press will surely damage the bearings or slightly bend the shaft.
Once bearing will be installed over the bearing seat
provided on shaft, we will release the press and remove the shaft carefully.
Do you have suggestion? Please provide in comment
box.
Reference: SKF bearing maintenance manual
Image Courtesy: Google
We will discuss the lubrication of bearing in our
next post.
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