SKF INDUSTRIES, INC BEARINGS GROUP
SKF Industries Inc 1979 Although care has been taken to assure the accuracy of the data complied in this publication SKF does not assume any liability for errors or omsslons
REG NO. 47
SKF Industries Inc 1979 Although care has been taken to assure the accuracy of the data complied in this publication SKF does not assume any liability for errors or omsslons
REG NO. 47
The History of Rolling Bearings . . . . . . . . . 2 Bear ea ring Rolling
Nomenc Nomenclatur lature e Bearing
Types
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4 5
Bearing Bearing Types ypes and and their Function unc tion . . . . . . . . 6 Mounting of Bearings-Shaftsand Housings . . . . . Do’s and Don’ts for Bearings . . . . . . . . . 14 Troubleshooting
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SKF Industries, Inc. Inc. per periodic iodica ally cond c onduc uctts “Bear ea ring Maint Maintena enanc nce e Semina Seminarrs” at the Corporate C orporate Hea Headq dquart uarters ers in King King of of Prussia ussia,, Pa Pa. For informa informattion ion conta contac c t yo your ur loc loc al aut authorized horized SKF Distribut ibutor or or SKF Sales les Office Office.
THE HIST HISTORY OF OF ROLLING BEAR EARING INGS THE BASIC
PRINCIPL INC IPLES of design and applic a pplication ation of roiling bearings bea rings were conc c onceive eived d many c enturies ago. ago. They were
developed deve loped
for
one
purpose
only-- to only--to
lessen
friction.
History records ec ords that down through the ages ages men desir desired to move but
not
always
ac hieved. achieved.
Regardless
of
availa ble available
manpower, ma npower,
heavy heavy objec objects ts ac ross the eart earth’s surfac e, Desired,
sliding
fricti iction
betw between een
the the
eart earth’s
surface fac e
and a nd
the
sometimes made it impossible.
As far back bac k as 1 100 B.C., we know that such fric fricti tion was reduced reduced by the insertion of rollers between the objec objectt and the surfac e over ove r which which it was being be ing moved. move d. Fig. 1 illustrates how, in 1 100 B.C., .C ., the Assyrians and Babylonians used rollers to move enormous stones for their their monuments and pala c es. Thr Throughout oughout histor history y a re rec orded many similar examples
man’s war on friction. iction.
In modern mod ern times, the first first important vic tory ove r fric fric tion was the invention of the wheel. However, the early wheel was based on sliding friction iction (Fig. 2) and a long time elapsed ela psed before be fore this principle inciple was refined. refined. Later, wheels rendered friction a “body blo w” when when Fig.
I
C
they they were rested rested o n an a ssembly ssembly of ba lls or rollers. rollers. Cyc ling and skating, which invo lved p ersonal e ffort, ffort, boo sted sted interest in rolling bearings (Fig. 3)-and started long years of slow development.
Anyone who has has tried to move a
heavy
objec t by sliding, readily eadily
appreciates the ease with which it can be done when rollers are used. Weight of the the o bjec t is not a fac tor-a tor-a s long as bo th the the rolling eleme nts nts and the surf surfac ac e ove r whic whic h they they pa ss c an support it without being pressed out of shape.
Place a heavy book on a flat, smooth surface (Fig. 4) and as you push it ac ross that surf surfac ac e, notic e the amo unt of effort required. This Fig.
wheel,
is
sliding liding
friction. friction.
on sliding friction
Fig. 3-Cycling boosted anti-friction
Fig.
f r i c t i on
Fi g. S -R ol l i ng mo ti on
Now, plac e two round pencils under the book (Fig. 5). Note how easily it can be moved. This is the difference between sliding friction and rolling
motion.
You will note that, when pushing the book with the pencils as rolling elements, a trac king effect is present. The book can go forward or backward with ease.
Now, substitute several balls for the rollers (Fig.
and note the
added ease with which the book moves. Also, note the fact that it can be moved in one direction as easily as in another. These adFig. 6-Improved rolling
motion
vantages are due to point contac t provided by the balls, rather than the line contact of the pencils.
In review
we noted that sliding the book on the surfac e required
a certain effort
that rolling it over the pencils required less effort
but that the direction was limited
and finally, when we substituted
the balls, less effort was required and direction was unlimited.
The book, the surface and the penc ils
o r
balls are the three im-
portant, basic parts of a ball or roller bearing.
If you performed this interesting experiment, you noted several imFig.
b e c o m e s i nn e r
portant fac tors. First, that the book would run off the penc ils and the balls. Sec ond, and this may not have been so apparent, that there was a tendency for
o ne
roiling element not to follow or “trac k”
the same as the other rolling element. This was true of both pencils and
but to a lesser degree in the bail experiment.
Let us imagine that the book in Fig. 6 is curled into the position of Fig. 7. The book is then the equivalent of the inner ring of a ball . bearing.
While our imagination is at play, pic ture the table surfac e of Fig. 6 curled into the position of Fig. 8 Fig.
and the balls in the position
illustrated.
b e c o m e s o u t e r ri n g
Actually, we have c onverted our early experiment into a basic ball bearing in design. The book becomes the inner ring
the surfac e
the outer ring
and the balls the rolling elements (Fig. 9).
This
however,
experiment,
does
not
illustrate
one
other
important
part of a bearing. You will recall that we noted that the pencils or balls did not “trac k”
i.e., roll in the same direction, or keep the
same distance apart. For this reason the bearing requires a c age, or retainer, to keep the rollers or balls in their proper position. In tapered roller bearings the inner ring is called the cone, Fig.
illustrates bask bearing
design
outer ring, the cup.
the
BEARING NOMENCLATURE The illustrations below identify the bearing parts of the eight SKF basic bearing types. The terms used conform with the terminology sec tion of the AFBMA* Standards+nd are mutually accepted by the anti-friction bearing manufacturers *Anti-Friction Bearing
Manufacturers Association, Inc.
Self-Aligning Ball
Single
Bearing
Deep
Row
Angular
Contact
Groove Bearing
Double
Row
Roller
Deep G r o o v e Ball
Cylindrkol
Tapered Roller
Roller
Bearing
Bearing
Spherical Roller
Thrust Roller T h r u s t Bearing
1. 2. 3. 4. 5.
Inner Ring Inner Ring Corner Ring Outer Ring Land Outer Ring
6 . Ball 7. Counter 8. Thrust Face
4
9. 10. 11. 12. 13.
Outer Ring Raceway Inner Ring Raceway Outer Ring Corner Spherical Roller Lubrication Feature (Hole and Groove) 14. Outer Ring Raceway Floating Guide Ring 16. Inner Ring
17. Outer Ring Face 18. Cylindrical Roller 19. Outer Ring Rib 20. C o n e F r o n t F a c e 21. Cone Front Face Rib 22. Cup (Outer Ring) 23. Tapered Roller 24. Cone Rock Face Rib
25. Cone Bock
2 6. U n d e r C u t 27. 28. 29. 30. 31. 32. 33.
Cone (Inner Ring) Cage Cage Guide Sleeve Shaft Washer (Inner Ring) Housing Washer (Outer Ring)
ROLLING BEARING TYPES BALL BEARINGS
Single Row
ROLLER BEARINGS
Radial Thrust
Double Row
Separable Outer Ring
Duplex
Snap Ring and Shield
Shield
Cylindrical Roller Separable Inner Ring
Magneto
Tapered Roller
separable
Seal
Multi-Row
Self- Aligning
Cylindrical Roller
Cylindrical
Roller
Wheel
Roller Thrust
Spherical Roller Double Row
Needle Roller
5
BEARING TYPES AND THEIR FUNCTIONS Designers have a
wide variety of bearing types from which to choose. Each bearing type has characteristics which
make it the best choice for a certain application. The original selection is made to assure maximum bearing performance. Therefore, a replacement should be made
with the same type bearing, The following
of the functions
of eac h bearing type will aid you to better serve your replacement field.
SELF-ALIGNING The Self-aligning
BALL Ball
BEARINGS
Bearing, with two rows of balls roiling on the spherical
surfac e of the outer ring, c ompe nsates for angula r misalignme nt resulting from errors in mounting, shaft deflec tion and
distortion of the foundation. It is
impossible for this bearing to exert any bending influence on the shaft, a most important
consideration
in
applications
requiring
extreme
accuracy,
at
high
speeds. Self-a ligning Ball Bearings are rec ommended for radial loa ds and small
thrust
loads
in
either
direc tion.
SINGLE ROW, DEEP GROOVE BALL BEARIYGS The
Single
Row,
Deep
Groove
Ball
Bearing
will
sustain,
in
addition
to
radial
load, a substantial thrust load in either direction, even at very high speeds. This
advantage
results
from
the
intimate
contact
existing
between
the
balls
and the deep, c ontinuous groove in eac h ring. When using this type of bearing, careful alignment between the shaft and housing is essential. This bearing is also availa ble with sea ls and shields, whic h serve to exc lude dirt and retain
lubricant.
ANGULAR
CONTACT
BALL
BEARINGS
The Angular Contact Ball Bearing supports a heavy thrust load in one direction, sometimes
combined
with
a
moderate
radial
load.
A
steep
contact
assuring the highest thrust capacity and axial rigidity, is obtained
angle,
by a
high
thrust supporting shoulder on the inner ring and a similar high shoulder an the opposite side of the outer ring. These bearings can be mounted singly or, when the sides are flush ground, in tande m for co nstant thrust in one direc tion; mounted in pairs, also when sides are flush ground, for a combined load, either face-to-face
or
back-to-back.
DOUBLE ROW, DEEP GROOVE BALL BEARINGS The Double Row, Deep
G r o o v e Ball
Bearing embodies
the
same
principle
of
design as the single row bearing. However, the grooves for the two balls are so positioned that the load lines through the balls have an outwardly converging contact angle. This bearing has a lower axial displacement than occurs in the single row design . . . substantial
thrust
capacity
in
eithe r direc tion . . . and high radial capacity due to the two rows of balls.
6
SPHERICAL ROLLER BEARINGS The Spherical Roller Bearing, due to the number, size and shape of the rollers, and the ac curacy with which they are guided, has unexcelled capacity. Since the bearing is inherently self-aligning, angular misalignment between the shaft and housing has no detrimental effect and the full capac ity is always available for useful work. The design and proportion are such that, to radial load, heavy thrust load may be
carried in either direction.
CYLINDRICAL ROLLER BEARINGS The C ylindrical Roller Bearing has high radial capacity and provides ac curate guiding of the rollers, resulting in a close approach to true rolling. Consequent low friction permits operation at high speed. Those types which have flanges on one ring only, allow a limited free axial movement of the shaft in relation to the housing. They are easy to dismount even when both rings are mounted with a tight fit. The double particularly
suitable
for
row type
machine
tool
assures maximum radial rigidity and is spindles.
SPHERICAL ROLLER THRUST BEARINGS The Spherical Roller Thrust Bearing is designed to carry heavy thrust loads, or combined loads which are predominantly thrust. This bearing has a single row of rollers which roll on a spherical outer race with full self-alignment. The cage, centered by a cage guide sleeve, is constructed so that lubricant is pumped directly against the inner ring’s unusually high guide flange. This insures good lubrication between the roller ends and the guide flange. The spherical roller thrust
bearing
operates
best
with relatively heavy oil lubrication.
TAPERED ROLLER BEARINGS Since the axes of its rollers and
an angle with the shaft axis,
the Tap ered Roller Bearing is espec ially suitab le for c arrying radia l and axia l loads ac ting simultaneo usly. A bea ring of this type usually must be ad justed toward a nother bea ring c ap ab le o f c arrying thrust loads in the oppo site
direction.
Tape red
(inner rings) with rollers and
Roller
Bea rings
are
separable -their
co nes
their cups (outer rings) are mounted separately.
SHIELDS, SEALS AND SNAP RINGS
Shield
Suffix
Two Shields
Red Seal
Tw o Red
Sna p Ri ng On O uter Ring
Suffix
Sna p Ri ng On O uter Ring O n Opposite Side To O ne Sh ie ld
Suffix NR
Suffix ZNR
Sna p Ring On O uter Ring On Some Side A s O ne Sh ie ld
Snap Ring On Snap Ring On Outer Ring On Outer Ring On Opposite Side Same Side To O ne Re d Se a l A s O ne Re d
Suffix
RSNR
Suffix
ANGULAR CONTACT BALL BEARINGS IN DUPLEX MOUNTINGS
FACE-TO-FACE
TANDEM
BACK-TO-BACK
PARTS AND ASSEMBLY OF
Tapered Bore Bearing
SIC
F
ADAPTER BEARINGS
Adapter Mounting
MOUNTING OF BEARINGS -SHAFTS AND HOUSINGS CLEANLINESS
MOUNTING DESIGNS The
successful
application
of
a
ball
or
roller
bearing
l l
The importanc e of protec ting the be aring from the intrusion of dirt and other foreign matter ca nnot be over emphasized. Seals must be designed to prevent
depends to a great degree on two factors: the mounting design the accuracy of the various machined surfaces upon which the bearing is supported.
the entranc e of any type of foreign matter to the bearing. Dirt will act as a perfect lapping c ompound and
Unless care is exercised mounting and
in both designing the bearing
machining the various parts, a prema-
ture failure may result. This is true, even though the capacity of the bearing specified may be well above the applied load.
will grind the bearing surfaces. This will result in
excessive wear of the rolling elements and of the inner and
outer
rings.
In
addition,
foreign
matter
will
con-
taminate the lubric ant-and gradually break d own the oil or greose to the point where effective lubrication ca nnot be obtaine d. Dirt will also ca use noisy operation.
The narrow width of a ball or roller bearing provides a comparatively small surface area for the applied
The cavity in the housing around the bearing should
load. Hence, the unit pressures are high and must be
be large enough to provide for an adequate amount
uniformly distributed to the supporting surfac es of both
of lubricant. Seals should be
the shaft and the housing. Therefore, it is evident that
lubricant in the housing.
effective in retaining the
both the inner and outer rings must be properly mounted on the shaft and in the housing respec tively. Serious distortion is eliminated and uniform distribu-
MOUNTING AND DISMOUNTING
tion of the Ioad is obtained. Bearings may be mounted directly on the shaft or on This same care must also be used with respect to the
tapered
odapter
sleeves.
pedestal on which the bearing housing is mounted. Distortion of the bearing housing will occur, unless the
When mounted direc tly on the shaft, the inner ring should be
pedestal is firm and the surface true.
height.
located against a
Proper
shaft
shoulder
shaft shoulder of proper heights
are
listed
in
the
A bearing housing should be designed to permit a
Bearing C atalog s. This shoulder must be mac hined
simplified
square with the bearing seat and a shaft fillet should
assembly and
disassembly of the
component
pa rts. Suc h design should a lso provide for simple
be used. The radius of the fillet must clear the corner
methods of ca sting, with few mac hined surfac es-to reduce costs to a minimum.
mounting the outer ring in the housing. Generally
Shaft filler Too Large
radius of the inner ring. This also applies when
Correct
Fillet
9
Shaft Shoulder Diameter Too Large
Shaft Shoulder Diameter Too Small
speaking,
bearing
applications
have
a
rotating
inner
Correct Shaft Shoulder Diameter
speed of the shaft (planet gear) would be greater
ring with a stationary load applied to the bearing. In
than the speed of the inner ring (ring gear)-and
such cases, it is necessary to mount the inner ring with
sliding
a press fit on the shaft-and the outer ring with a slip fit in the housing.
and
This
will
result
in
overheating,
excessive
wear
contact erosion between the shaft ond the inner
ring. The explanation of creeping action can be simplified by the use of this c ompa rison. C ompore the ac tion of on internal gear in mesh with a planet pinion. If
the
planet
toke
place.
Therefore, it is an obvious conclusion that a preventive measure must be token to eliminate creeping and its
If the inner ring is loose o n the shaft, c reeping will occur.
would
pinion
(representing
the
shaft),
hod
one
harmful results. Mount the inner ring with a sufficient press fit on the shaft! This will insure that both inne r ring ond shaft act as a unit-and both rotate at the same spee d. It is also de sirable to use a loc knut to clamp
the inner ring agoinst the shaft shoulder.
If the opplied load is of a rototing nature, for example -vibrating
screens
where
unbala nc ed
weights
are
tooth less than the internal gear (representing the
attached to the shaft, then the outer ring becomes the
bearing inner ring), the latter would slip back one geor
critical
tooth in each full revolution of the shaft. Hence, the
case, the outer ring must be mounted with a press fit
member.
In
order
to
V-Belt ond Sprocket Drive, Resulting in Stationa ry Loa ds and Rotating Inne r Rings
10
eliminate
creeping
in
this
in the housing. The rotating inner ring, when subjected to a rotating load, c an be mounted with a slip fit on the shaft
A loc kwasher between the inner ring and the loc knut prevents the nut from loosening. The use of micronized graphite
It is evident, therefore, thot when the applied load is sta-
will greatly fac ilitate assembly and help prevent contact erosion of the parts A light coating of graphite is applied
tionary with respec t to the outer ring, a tight shaft fit is required When the applied load is stationary with respec t to the inner ring, a tight housing fit is required
-
on the 0.D adapter sleeve. It is good prac tice to apply a coat. of oil to the housing and c omponent parts before the
bearing unit is assembled.
Small bearings may be pressed on the shaft by using a piece of tubing. Pressure is applied to the inner ring of the bearing by the tubing. The assembly of larger open bearings can be simplified by a “heating” procedure Boil the bearing in an
INTERNAL BEARING FITS It is evident that a press fit between the parts will stretch the
emulsion of 10% to 15% soluble oil in water. Make sure the bearing is placed on a grating so it does not touch the sides or bottom of the container Temperature c ontrol is automatic
inner ring. This holds true when mounting the bearing directly on the shaft or by means of an adapter sleeve. Thus, there
but sufficient time should be allowed to assure that the bearing is heated throughout This will sufficiently expand the
anc e in the bearing.
bearing and permit it to slide easily over the shaft to its proper location Care should be taken to prevent cocking of the inner ring as this may c ause it to seize before the bearing is properly located If this happens, it is best to remove the bearing promptly and reheat When the bea ring coots, it will shrink and grip the shaft It requires only a little ingenuity to
provide the tools to facilitate this procedure An elec tric hot plate or an induction heater can also be used to heat an open beoring. Temperature should not exceed 121 ° “C (250°F) Assembly of sealed bearings can be accomplished by heating the bearing to a maximum of 107°C
(225°F) with either a hot plate or an induction heater and proceed as mentioned above for mounting the bearing.
SHAFT AND HOUSING FITS A ball or roller bearing has extremely accurate component parts which fit together with very close clearances. The inner ring bore and the outer ring outside diameter must be manufactured within close limiis to fit their respective supporting members-the shaft and the housing It follows that the shaft and housing must also be machined to close limits Only then, will we obtain the required fits when the bearing is mounted. It is advisable to refer to the tables of shaft and housing fits as published in the SKF Engineering Data C atalog. These tables list recommended dimensions and tolerances for various types of shaft and housing fits suitable for various operating conditions.
ADAPTER SLEEVE The use of a topered adapter sleeve on standard shafting will greatly simplify the mounting of the bearing. The outer surface of the sleeve is tapered to match the tapered bore of the beoring inner ring. This will provide the required tight fit between the inner ring and the shaft The adapter sleeve is slotted to permit easy contrac tion and is threaded at the small end to fit a locknut When the loc knut is tightened to
the recommended Reduction in Internal Radial Looseness, the correct interference between inner ring and shaft is achieved.
will be a tendency to reduc e the initial internal radial c lear-
If an exc essive press fit is used, it is possible to reduce the bearing clearance sufficiently to make the bearing tight. However, if the rec ommended shaft fits are used a nd operating temperatures have been taken into account, the internal clearance remaining after mounting the bea ring will be sufficient to insure proper operation. When an adapter mounting is used, some additional cautions should be heeded If these are taken into consideration, the
bearing will not be tight internally. The following is the recommended prac tice for mounting selfaligning ball bearings on adapters. Mount bearing on adapter sleeve, starting with the large bore of the inner ring to match the taper of the adapter. With the bearing hand tight on the adapter, locate bearing to the proper axial position on the shaft [Do not apply lockwasher at this time because drive up procedure may damage lockwasher.) Apply the loc knut with chamfered fac e toward the bearing after lubricating the face of the loc knut next to the bearing.
Hand tighten the nut with a spanner wrench until the adapter sleeve can neither be moved axially nor rotated on the shaft. Then with a hammer drive the spanner wrench until the loc knut has been turned 90’ or ¼ turn on the adapter sleeve. CAUTION: A loose adapter sleeve c an lead to the inner ring turning on the adapter sleeve and/ or the adapter sleeve turning on the shaft. To insure that the nut is not excessively tight, make certain the outer ring of the bearing rotates freely. When mounting a normal fit bearing, swiveling the outer ring will result in a slight drag If the bearing is a C 3 fit, the outer ring will swivel freely. Before mounting spherical roller bearings on adopters, the internal c leoronce should be checked and recorded Measure the unmounted internal clearance in the bearing by inserting progressively larger feeler blades the full length of the roller between the most vertical unloaded roller and the outer ring sphere Do not roll the feeler blade through the c learance; slide it through Rec ord the measurement of the largest size blade that will slide through. This is the unmounted internal clearance. The bearing should be resting upright on a table when making this check
11
reduces
the
internal
clearance
in
the
bearing-in
addi-
tion to the reduction due to the tight fit on the shaft. To
compensate
for this additional
reduction
of
internal
clearance in the bearing, some provision must be made. Bea rings
with
an
internol
c lea rance
than
standa rd should be used. This ad ditional c lea ranc e will Adapter Mounting
to
After mounting the bearing on the shaft and adapter sleeve,
the locknut is tightened
to reduce
the initial c lea rance by the required a mount. This is checked in the same manner as above, by using the feeler
gauge.
The
dec rease
mounting c an b e found
in
internal
clearance
after
in SKF Engineering Data
Catalog 140-l 10.
compensate the
for
temperoture
internal
clearance
differential
between
reduction the
inner
due and
outer rings. There are other cases where
bearings with
internal
are
clearance
greater than
standard
required.
Among these are dryer c ylinder bearings in pape r mac hinery where stea m pa sses through the hollow shaft
shaker sc reens where tight housing
required
high
speed
applications
where
are
the
tem-
perature rise in the bearing, due to speed and load, is abnormal
etc.
It is desirable that such c ases, and applications where extremely
high
temperatures
are
involved,
be
referred
TEMPERATURE CONDITIONS
to the SKF App lic ations Enginee ring Department.
C ertain types of bea ring ap plic ations require the
If this ad ditional internal c lea ranc e is not provided ,
consideration
the bea ring will be e xc essively tight internally a nd
of
variable
temperature
conditions.
cannot
operate
successfully.
subsequent
high
For Example: An induced draft fan handling gases at
temperotures
high temperature. The fan wheel is mounted on the
lubricant due to carbonization will occur.
shaft. Therefore,
and
Excessive
operating
break-down
of
the
of the shaft in the fan casing
is subjected to the high temperatures. The bearings are usually
mounted
direc tly
outside
the
fon
casing.
Thus,
FREE AND HELD BEARINGS
the temperature of the shaft at the bearing location is c onsiderably highe r than the room temperature. It
A temperoture va riation will expa nd or c ontrac t the
follows that the inner ring of the bearing (mounted on
component parts of any machine. Due to this condition,
the shaft) will be considerably hotter than the outer
it is essential that such
ring. This is true,
or contract without restriction. For that reason, only one
as the outer ring is mounted in
the
housing whic h is isolated from the fan a nd not to the high temp eroture. As a result,
the
Free
12
Bearing
to expond
bearing on any one shaft should be fixed axially in the inner
ring will expand more than the outer ring. This action
CLEARANCES TO PERMIT AXIAL MOTION
parts be permitted
housing (c alled a “held” bearing) to prevent axial or end motion. STABILIZING RING TO LOCATE BEARING AXIALLY MOUNT IT ON LOC KNUT SIDE
Held Bearing
All other beorings on that same shaft should have
adding
adequate
to
added, remove the plug (preferably at the lower holf
bearings will permit the
of the housing) while the bearing is in operation. This
axial
clearance
in
as “free” bearings). Such free shaft to
elongate
and
the
contrac t
housing without
(referred
lubricant to the bearing. After the lubricant is
permits the exc essive lubric ant to flow
restriction.
out of the
housing and relieve the internal pressure. When the In
gear
reducers
where
herringbone
gears
are
used,
only one bearing on one of the shafts should be “held,” usually the input shaft. It is evident that the “V” shape of the gear teeth will locate the other shaft axially.
flow of grease ceases, be sure to replace the plug. Speed
and
other
operating
conditions,
in
some
cases,
require that oil lubrication be used. In that event, the bearing housing should be equipped with adequate oil fittings. Such fittings should provide a static oil level
When a flexible coupling is used to connect two shafts,
at the center of the lowest ball or roller in the bearing.
a “held” bearing is required on each of the shaftsas a flexible coupling permits end motion of both shafts.
It is preferable to use sight gla ss oil ga uges whic h can be c learly marked for static and operating levels. The operating level is slightly lower than the static
LUBRICATION
level due to agitation of the oil.
The bearing unit can usually be lubricated with a good
The static level can be marked on the gauge before
grade of lithium and be
operating filled
base grease for normal loads, speeds conditions.
approximately
The
bearing
one-third
full
housing with
should
grease.
the unit is assembled. The op erating level c an be determined only after the bearing is in operation. The gauge should also be marked for the operating level and the lubricant, at no time, should be
An e xc essive q uantity of grea se will “build up” in-
drop below this point.
ternal pressure in the bearing housing and result in
to the static
permitted to
But, never restore the oil level
marks while the bearing is running.
high temperatures-and subsequent damage to the The subjec t of lubrication is discussed
bearing.
in greater detail
in anothe r public ation, A G UIDE TO BETTER BEARING Here is a safety
measure to combat this danger when
LUBRICATION,
144-l
10.
13
DO’S AND DON’TS FOR BEARINGS assembly, maintenance, inspection and lubrication Do work as close to the ideal conditions pictured here.
Don’t work under the handic ap of poo r tools, rough
Dividends
bench, plenty of dirt.
in
bearing
performance
will
result.
DO work with clean tools, in clean surroundings.
DON’T work in dirty surroundings.
DO
DON’T use wooden mallets or work on rough or dirty
remove
exposing
all
outside
dirt
from
housing
before
bearings.
DO handle
bench tops.
with clean, dry hands.
DON’T use
dirty, brittle
DO treat a used bearing as carefully as a new one.
DON’T handle
DO use clean solvents and flushing oils.
DON’T
DO lay bearings out on clean paper.
DO p rotec t disassembled
spin
DON’T spin
bea rings from dirt and
moisture.
DO use clean, lint-free rags if bearings are wiped.
bearings
uncleaned
any
or chipped
with
dirty,
tools.
moist
hands.
bearings.
bearings with
compressed
air.
DON’T use same c ontainer for c leaning a nd final rinsing
of
DON’T
use
bearings.
c otton
waste
or
dirty
c loths
to
wipe
bearings. DO
keep
bearings
wrapped
in
oil-proof
paper
when
not in use. DON’T expose bearings to moisture or dirt at any time. DO c lean inside
DO
install
without
new
of housing before replacing bearings.
bearings
as
removed
from
packages,
DON’T scratch
or nick
bearing
surfaces.
washing. DON’T remove grease or oil from new bearings.
DO keep bearing lubricants clean when applying and cover containers when not in use.
14
DON’T use
incorrect kind or amount of
lubricant.
To press bec ring oh shaft,
Proper core begins in the stock room. Store bearings in
clean piece of tubing aver the shaft and rest it an inner ring
originol unopened packages, in o dry plac e. The bearing number isplainly shown on the
pressure is applied tc bearing, apply a coat of Iighl oil or micronized graphite to the
wrapping. Before packaging, the manufacturer protected the bearing with a grease coating. An unopened age means continued protection. Do not open c arton until reody to use.
bearing seat and the bearing bare This will facilitate
an shaft, then apply pressure by tapping end of pipe with
To shrink an open bearing an a
bearing with clean, dry hands and with clean rags. Lay bearing on clean paper and keep c overed. Never expose bearing on a dirty bench or floor. Never use o beoring as o gauge check either the housing bore or the shaft Note: To shrink a sealed bearing an a shaft, use only method 2, and limit temperature to 107°C
slushing oil should not be removed. Old grease can be washed from a used bearing with a solvent but fluid and container must be clean. After this cleaning, wash the bearing out thoroughly with light oil and then relubricate. Bearings should be washed only when necessary.
Before mounting, be sure shaft size is within the specified tolerances recommended for the bearing. The bearing seat should be perfectly round and not tapered. It should be c lean and free from nicks ond burrs. Shaft shown is too worn properly seat bearing-don’t use it. Support firmly in a clean place-if in a vise, protect it from vise jaws. Protectors can be soft metal, wood, cardboard or paper.
hom-
mer or using arbor press. Refer to illustration (A) an page 16
Open package only when ready to install bearing.
Don’t wash o new it is already clean and the
assem-
bly Be sure bearing is square
(225°F).
shaft, expand bearing by: 1. Boiling in emulsion of 10% to 15% soluble oil in water for 15 to 30 minutes .Be sure to plac e supports under bearing to isolate it from bot container as c ontact will overheat bearing 2 Heat in a clea n temperature-c on. trolled electric oven or on a hot plate to a maximum of 121°C 125O°F) for about fifteen minutes Thoroughly bearing but do notoverheat This will prevent seizing on the cold shaft Alter bearlng isinplace against shaftshoul. der. lock it immediatelv with a lock nut Otherwise, in shrinking, bearing may move away from its proper posi. tion againstshaft shoulder
When mounting in a split housing, chec k bore of housing to see that it is within specified perfectly
tolerances round.
not be pinched
and
Bearing
is
must
by small bore
or because of a cocked outer
ring. Don’t switch housing caps -they are not interchangeable. An undersized housing bore or on out-of-round bore will pinch the bearing cause early failure.
and
Some precaution must be e xercised when mounting bearing in a solid housing; i.e., the outer ring should be perfectly square with the housing bore before any pressure is applied. Here again, the housing bore should be within the specified tolerances for the bearing size and should be perfectly round. The housing bore and bearing outside diameter should be coated with light oil or micronized graphite to facilitate assembly.
15
(A) An arbor press is equally good for either mounting or removing beorings.
Cover the unfinished job when left for only a few hours or until the next day. Rewrap eac h bearing to keep out dirt and moisture. When this necessary, use grease-proof paper. lf you do not take c are of bearings during installation, they will not lost long.
Type of lubricant usually depends on operating conditions -follow machine builder’s instructions. When oil is used, cover about half of bottom ball or roller. It is preferred that o sight oil gauge be used and marked so as to show static and operating oil levels. This will greatly help to determine when additional oil is required. The operating level is different than the static level and can be determined only when the bearing is in operation. Bearing pullers which may be used separately or in various combinations to pull or push complete beorings or individual rings.
Be sure bearing is square with and held fhmly against shaft shoulder. Secure it with a loc knut and loc kwasher. Housing covers must be tight to keep lubricant in and dirt wt. After heid beoring has been positioned, the free bearing should be loc ated centrally in its housing to permit expansion and of the shaft.
Never pound directly on o bearing or ring. It will likely damage both
can-
trac tion
shoft and bearing.
To remove o bearing from the shaft, force inner ring with press or draw bar and plate. Shaft shoulder must be smaller than inner ring to make such removal. A variety of beoring pullers are ovailable. The use of such speciaiized tools will more than pay for themselves by preventing damage to serviceable bearings. Refer to group at right.
16
of
illustrations (8)
To drive shoft of beoring, use soft metal slug which will not mar the shaft.
INSPECTION and ASSEMBLY REQUIRE CLEAN BEARINGS Don’t try to judge the condition of a beoring until after it has been cleaned. while
Don’t spin dirty bearings. Rotate them slowly washing.
Don’t spin ony bearings with an air hose. Rotote one ring by hond when using air to expose all parts of bearing. Bearings with a shield or seal on
o ne
side only should
be washed, inspected ond handled in the same manner as bearings without shields or seals. Do not spin b e a r i n g s b e f o r e c l e a n i n g D i rt c a n c a u s e s e r io u s sc r a t c h i n g .
Bearings with shields or seals on both sides should not be woshed. Wipe them off to keep dirt from working inside. Smooth turning bea rings c an b e c oated with protective lubricant, then wrapped in
their
original
and stored or used
application.
If a small tank and wire baskets for soaking and washing
bearings
are
not
available,
a
clean
grease
can or bucket filled with solvent can be used. Let the bearings soak long enough to loosen the grease and i
dirt. Thot may toke several hours or longer. Then slosh the bearing around near the top of the container, giving it
turn now and then until it is clean. Rinse in a
clean container of clean
solvent.
Bearing cleaning solutions are generally petroleum vents intended
sol-
for bearing c leaning and are preferred.
So a k b e a r in g s t h o r o u g h l y i n p l e n t y o f s o l v e n t
Rinse them i n c l e a n s o l v e n t , li g h t o i l o r k e r o s e n e .
Do n o t
spin
b y f o r c e o f a i r . H o l d both rings. U se c l e a n , d r y a ir.
17
All solvents are highly inflammab le a nd prec autions
other foreign matter. Any clean cloth or paper will do
should be taken to prevent fires.
as long
A short, clean bristle brush from which the bristles will
DO’S
OS
the bearings are well covered.
I
on LUBRICATION
not come out or break off is helpful in removing dirt, scale or chips.
Follow
instructions
when
furnished
with
machinery.
Use
only grease where grease is spec ified and o il where After the be arings hove be en thoroughly c lea ned,
oil is spec ified. Be sure to use exac tly the kind of
inspect
lubricant
them
Inspected
immediately.
bearings which
are
considered
good
enough
to use again, but can’t be reossembled in the equipment on the same doy, should be dipped in slushing compound
Store
the
grease
instructions in
clean
spec ify.
containers.
Handle
grease
with
clean paddles or grease guns. Keep grease containers
covered.
stored ove rnight in a tightly c ove red Don’t overfill. Grease or oil will purge out of overfilled
pan.
housings past seals and closures, collect dirt and cause If inspec ted be arings are to be stored for more than a few days, dip them in a protective lubricant or coat all surfac es with a light grease, rototing them to work the grease thoroughly around the rolling members and on the rac eways. Wrap the be orings in greaseproof
trouble. Too much lubricant will also cause overheating. This is particula rly true of bea rings running at high speeds where the churning of the lubricant will cause the bearings to run excessively hot.
paper and place in o clean box or carton. Where
Don’t permit any machine to stand around for months
cartons ore not obtoinoble, wrap them in o waterproof
without turning it ove r once in a while so that all
paper and mark the outside of the
surfaces of the bearings will be covered with lubricant.
to identify
Oil tends to drain down off a standing bearing and
the bearing.
moisture may c ondense in the housing and c ause
DO
not
C over
leave
the
bearings
bea rings
exposed
until
in
ready
portial to
assemblies.
c omplete
Bearings
will collect if left
18
too long.
dust or dirt
corrosion.
the
assembly, to prevent damage by moisture, dirt or
Inspect seals and
,
vents regularly.
C o v e r w i t h c / eon c l o t h o r- p a p e r, especially if assem bly w ill not hours or until n e x t doy be completed for several
TROUBLESHOOTING This sec tion presents some helpful hints on be aring troubleshooting-what to look for when a c ustome r complains, how
to
recognize
the
reason
for
the
trouble
and
practical
solutions,
wherever
possible.
C ompla ints of bea ring trouble c an be reduc ed to a few c lassific ations-listed in the following order. For ease of relating them to conditions and solutions, they are coded A to G
A
inclusive.
Overheated bearing
-
Noisy bearing
CUSTOMER’S
C
COMPLAINT
D
Replacements are too frequent
- Vibration - Unsatisfactory
E F
G
The following table
performance
-
Bearing is loose on shaft
-
Hard turning shaft
lists some typical
of
equipment
conditions that will result in bearing failures.
The first c olumn numeric ally c ode s eac h typic al c ondition (Nos. 1 to 54 inclusive). The
third column is the customer-complaint code (A toG) to which the condition
may apply.
TYPICAL
RESULTING IN BEARING FAILURES
EACH CONDITION COULD CAUSE
ONE OF THE COMPLAINTS LISTED OPPOSITE THE RESPECTIVE CONDITION IN COLUMN
CODE
CONDITION
COMPLAINT
1.
lnadequote lubrication (Wrong type of grease or oil). . . . . . . . . . . . . . . . . . . . . . . . . . .
2.
Insufficient
3.
Excessive lubrication (Housing oil level too high or housing packed with grease). . . . . . . .
4.
Insufficient
oil level - l o s s of
lubrication (Low
clearance
in
bearing
(Selection
of
lubricant
wrong
5.
Foreign
matter
ac ting
as
on
abrasive
(Sand,
carbon,
6.
Foreign
matter
ac ting
as
a
corrosive
(Water,
ac ids,
7.
Bearings
pinched
8.
Bearings
pinched
in
9.
Uneven
shimming
of
10 .
Chips
in
the
housing
the
housing
housing
in
bearing
housing
velocity
over
11.
High
air
12 .
Seals
too
tight
(Cup
base
(Chips
bearings
(Bore
out
of
fit). . . . . . . . . . . . . . . . . . . . . . . . . etc.). . . . . . . . . . . . . . . . . . . . . . . . paints,
etc.). . . . . . . . . . . . . . . . . .
A- G A-B-C-E-G B-C-D-E-G B-C-D-E-G
. .. . .. .. . .. . .. .. . .. . .. .. . .. .
A-B-C-D-E-G
(Distorted
housing
(Oil
A-B-C-G
A-B-C-D-E-G
warped).
dirt left
seals). . . . . . . . . . . . . .
round). . . . . . . . . . . . . . . . . . . . . . . . . . . .
(Housing
or
through
A-5-C-G
in
bore
possible
cracking
of
base).
.
housing]. . . . . . . . . . . . . . . . . . . . . . . . . .
leakage). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
seals). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
A-B-C-D-E-G B-C-D-E-G C
A-G
19
TYPICAL CONDITIONS RESULTING IN BEARING FAILURES (Continued) CODE
COMPLAINT
CONDlTlON
13.
Seals misaligned (Rubbing against stationary parts). . . . . . . . . . . . . . . . . . . . . . . . . . . .
14.
Oil return holes plugged (Oil leakage). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
A
15.
Preloaded
A-B-C-G
bearings
(Opposed
mounting). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.
Preloaded bearings (Two held bearings on one shaft). . . . . . . . . . . . . . . . . . . . . . . .
17.
Bearing loose on shaft (Shaft diameter too small). . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18.
Bearing loose on shaft (Adapter not tightened sufficiently). . . . . . . . . . . . . . . . . . . . . . .
A-B-G
A-B-C-E-G B-C-D-E-F B-C-D-E-F
19.
Bearing
20.
Split pillow block with uneven surfaces (Oil leakage). . . . . . . . . . . . . . . . . . . . . . . . . . .
C
21.
Spinning of outer ring in housing (Unbalanced load). . . . . . . . . . . . . . . . . . . . . . . . . . .
A-C-D-E
22
Noisy bearing (Flat on roller or ball due to skidding). . . . . . . . . . . . . . . . . . . . . . . . . . .
B-D-E
23.
Excessive shaft expansion (Resulting in opposed mounting). . . . . . . . . . . . . . . . . . . . . . .
A-B-C-E-G
24.
Excessive shaft expansion (Resulting in insufficient clearance in bearing). . . . . . . . . . . . .
25.
Tapered shaft seat (Concentration of load in bearing). . . . . . . . . . . . . . . . . . . . . . . . . .
26.
Tapered housing
27.
Shaft shoulder too small (Inadequate shoulder support-bending of shaft) . . . . . . . . . . .
28.
Shaft shoulder too large (Rubbing against bearing seals). . . . . . . . . . . . . . . . . . . . . . . .
A-B-C
29.
Housing shoulder too small (Inadequate shoulder support). . . . . . . . . . . . . . . . . . . . . . .
C-D-E-G
30.
Housing shoulder too large (Distortion of bearing seals). . . . . . . . . . . . . . . . . . . . . . . .
B-C-G
31.
Shaft fillet too large (Bending of shaft) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
32.
Housing fillet too large (Inadequate support). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
33.
Insufficient
34.
Oil gauge breather hole clogged
35.
Shafts out of line (Linear misalignment). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
36.
Shafts out
37.
C onstant oil level c ups (Inc orrec t level). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
A-C
38.
Constant oil level cups (Located against rotation of bearing]. . . . . . . . . . . . . . . . . . . .
A-C
39.
Lockwasher prongs bent (Rubbing against bearing). . . . . . . . . . . . . . . . . . . . . . . . . . .
A-B-E-G
40.
Incorrect positioning of fingers
A-B-C-G
41.
Pedestal surface uneven (Bending of housing causing pinching of bearing). . . . . . . . . . .
A-C-D-E-G
42.
Ball or roller denting (Hammer blows on bearing). . . . . . . . . . . . . . . . . . . . . . . .
B-C-D-E
43.
Noisy
44.
Lubricant leakage and entrance of dirt into bearing (Worn out seals). . . . . . . . . . . . .
C
45.
Vibration (Excessive clearance in bearing). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
D-E
46.
Vibration
D-E
47.
Hard turning shaft (Shaft and housing shoulders out of square with bearing seat). . . . . . .
C-E-G
48.
Bearing loose on shaft (Knurling
A-F
49.
Discoloration of bearings (Use of blow torch to remove bearing). . . . . . . . . . . . . . . . . .
a
50.
Oversized
A-B-C-E-G
.
too tight internally
bore
(Adapter tightened excessively), . . . . . . . . . . . . . . . . . . . . .
(Concentration of load
in bearing). . . . . . . . . . . . . . . . . . . . . . .
clearance in labyrinth seals (Rubbing). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
of line
bearing
(Shows incorrect oil level). . . . . . . . . . . . . . . . . . . . . .
(Angular misalignment). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
(Extraneous
(Unbalanced
(Rubbing against covers). . . . . . . . . . . . . . . . . . . . . . . . . .
c onditions). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
loading). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
and center punching of shaft for bearing seat). . . . . . .
shaft (Overheating and noise). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
A-E-C-E-G
A-C-E-G C-D-E C-D-E C-D-E-G
C-D-E-G C-D-E-G A-B-C-G A-C A-C-D-E-G A-C-D-E-G
B
51.
Undersized housing
52.
Oversized
53.
Enlarged housing bore (Excessive peening of non-ferrous housings). . . . . . . . . . . . . . .
A-B-C-D-E
54.
Noisy
B
20
housing
bearing
bore bore
(False
(Overheating (Overheating
of bearing). . . . . . . . . . . . . . . . . . . . . . . . . . . .
A-B-C-E-G
. . .. . .. . .
A-B-C-D-E
of
bearing-spinning
of
outer
ring).
brinelling). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
A pplic a tion Re po rt
No.592
DETERMINE THE CONDITION OF
ANTI-FRICTION BEARINGS
by Robert E. Ellis Balancing & Consulting Service Manager IRD
Corporation
INTERNATIONAL RESEARC H A ND DEVELO PMENT C O RPO RATIO N Subsidiary
of
H. H. Robertson Co.
6150 Huntley Road, Worthington, Ohio
(Columbus)
Phone 885-5376
Using IRD Model 600 Vibration Analyzer to DETERMINE THE C ONDITION OF ANTI-FRICTION BEARINGS How do you know when bearings are worn and need ? Many times the answer is obvious to be replaced because of machine failure, poor quality in finished parts, and unscheduled downtime. When you dismantle you may find pits in the raceways or on the balls or rollers. You may find flaked areas, discoloration, broken retainers, dirt, corrosion, and a host of others. If a faulty bearing is continued in operation it always gets worse, never better. The whole mac hine may be c ome noisy, the shaft may bec ome loose and other parts of the mac hine may fail.
perpendicular to shaft axis orthe shaft is not in line with the housing.
b) Angular and/ or offset misalignment between different mac hine components of a system, such as a motor driving a fan through a gear box. This condition refers to misalignment between motor and gearbox or gearbox and fan, and occurs when the shaft axis is not parallel to the axis tbrough the bearing c enters.
2) Dirt or Foreign Matter-dirt or metal part-
icles in the lubricant or from flaking will be Bearings with pitted or rough rac eways and balls pressed between the rolling elements of the impose forces on the c ages when the rolling elebearing and the rac eway c ausing forces that ments contac t the rough spots. These forces show produce indentation and pits. up as vibration in the machine structures. It is 3) Lac k of Lubrication-A dry bearing may prothese forces that result in dec reased bearing life, vide excessive heat, rubbing bearing disfatigue failure, heat and noise. Eventually, the tortion showing up as vibration. bearings become unserviceable. It is also these forces that allow us to detec t the bearings’ condi4) Corroded Parts-can start from: rust, oxition through vibration analysis before a costly dation of lubricant, contaminating infailure oc curs. In many c ases the minute vibrafluence. tions present in a mac hine structure c lose to the 5) Pits-can be caused by c orrosion or elec tribearing contain the information needed to detercal arcing. Electrical leakage may occur mine the bearing’s condition. Vibration is often through bearings from static elec tricity on a good indicator of bearing performance. A high line shafts and in direct currentmotors. vibration level can indicate damage by unbalance Sparking at regular intervals burns away or misalignment, excessive radial or axial load, metal leaving holes and pits. dirt and corrosion, or brinelling in assembly. 6) Lack of Concentricity-usually becomesapThe IRD Vibration Analyzer can be used to anaparant only at a low level of vihration-may lyze these and other vibrations so that a rapid show up as vibration at rotor speed. The evaluation of the bearing’s condition may be obcharac teristics are such that it ac ts like tained a nd c orrec tive ac tion take n if neede d. unbalance which shows up on one radial dirCauses of Bearing Vibration ec tion (horizontal, vertical, or atsome other specific angle). The equipment can generSources of vibrations in bearings are: ally be balanced to a low level of vibration 1) Misalignment-two kinds in one direction but will not show a low a) Angular misalignment between inner and level of vibration in another. outer rac es-the bearing rotates with the inner ring at an angle to the shaft axis, 7) Pinch and Ove rload -bea rings installed in the balls will wear a track which wobout-of-round housings or on out-of-round bles from one side of the rac eway to the shafts may distort enough to cause vibration other. Common causes of this condition overload, and failure. Early fatigue failure are: shoulder out-of-square, burr between at opposite sides of the rac eways may result. the shoulder and bearing and fillet too large. 8) Bearing-Retainer Rattle-loose retainers may be a sourc e of vibration. Misalignment difficulties c an also arise when bearing housing shoulders are not 9) Excessive Clearance-mostly found in sleeve
bearings. Can be detected by the difference in amplitude readings taken on the bearing
Analyzing Bearing Faults with the Model 600
housing and on the shaft. Shaft readings are
bearing housing as close to the bearing moving
obtained by measuring directly on the shaft
parts as possible. One exception is when making
running in the bearing, using a shaft stick.
direct shaft measurements using the shaft stick.
10) Cracks in Rings and Parts-damage that has occurred during installation through excessive force, hammering or forcing the bearing onto a tapered seat.
M a k e all vibration measurements directly on the
Things to look for when analyzing bearing vibration: Filter Out
1) Small erratic increases and dec reases in am-
Many of the above conditions will show vibrations
plitude meter reading. May be random or periodic. Amount of vibration will depend on
in the axial direction on pre-loaded bearings.
severity of fault.
A rough anti-friction bearing where the roughness
2)
will appear at several positions. May oc cur as a multiple image slowly rotating. Strob
tive high frequenc y of vibration. The vibration frequenc y may be several times the frequenc y of
pattern appears related
in the bear-
ing. The frequency of vibration may not be a direc t
3)
and
Critical
Speeds
radial load, which
c onsumes
some of the bearing’s capacity and which, if excessive, can lead to beoring failure. Balancing is
essential;
Apparent erratic frequency meter readings.
Often the best frequency indications are ob-
Both unbalance and operation at critical speed will cause a rotating
to shaft speed.
Generally, the frequency meter will indicate a muc h higher frequency than shaft speed.
multiple of the shaft speed.
Unbalance
or multiple firing of the
strob lamp. Referenc e mark on the shaft
due to pits, holes, dirt, etc., results in a rela-
the rotating member which is mounted
Apparent erratic
tained using the velocity position. F i l t er I n 1)
Steady
vibration displacement
readings-low
and limits should be set such that the
or
amplitude-high
velocity
frequency-
frequency indications not a direct multiple of shaft speed. Velocity measurements usually most useful.
unbalanc e load on the bearing is not more than one-tenth of the bearing capacity at speed. Ball bearings will sometimes operate for limited
Steady frequenc y meter indications at high
periods of time at or near a shaft critical speed, provided that the critical speed is low. The effect
speeds. May or may not be direct multiples
of operation at a c ritical speed is unpredictable bec ause of the unknown damping fac tors, and it is, therefore, best to keep the shaft critical speed either well above operating speed or well below it. High vibrations on bearings that are misaligned, overloaded,
etc., will show high frequency char-
ac teristics as noted above.
forces due to unbalanc e of rotating parts
or misalignment moy mask many bearing troubles.
Unbala nc e,
3)
Variable
vibration
amplitude
readings-rel-
atively low amplitude-high frequency. Amplitude readings “beats” or slowly varies up and down. Frequency meter steady. Frequency may or may not be a direct multiple of the shaft speed. The vibrations due to rough bearings are easily distinguished from high frequency electrical vib-
C AUTION Large
of the shaft speed.
misalignment,
loose,
and
damaged parts must be c orrected before bearing analysis is attempted. Balance the rotating parts to a low vibration level if required.
The information given below describes the use of the IRD Model 600 Vibration Analyzer for analyzing bearing faults.
rations .Vibrations due to rough hearings will continue after the electrical power has been shut off and while the rotating member is coasting toa stop. Vibrations from electrical causes, however, will cease immediately when the electrical power is shut off.
Use of an Oscilloscope An Oscilloscope connected to the scope outlet jack of the IRD Vibration
Analyzer will allow
a
direct visualobservation of the bearing vibration pattern as measured at the pic kup loc ation. The presence of high frequency noise and hash, spikelike pulses or erratic and rapid c hanges in amplitude are bearing condition indicators. Either displacement or velocity may be used but velocity measurements usually give better high frequenc y indications The higher the speed, the more sensitive the bearing is to theadverse effects of misalignment, poor lubrication, improper fitting prac tice, poor heat dissipation and c ontamination.
-
IRD #592
DO’S AND
DON’T’S
FOR BEARINGS
assembly, maintenance, inspection and lubrication
. . .
Do work as close to the ideal conditions pictured here.
Don’t work under the handicap of poor tools, rough
Dividends
bench, plenty of dirt.
in
beoring
performance
will
result.
DO work with clean tools, in clean surroundings.
DON’T work in dirty surroundings.
DO
DON’T use wooden mallets
remove
exposing
DO
all
outside
dirt
from
housing
before
bearings.
handle
or work on rough or dirty
bench tops.
with-c lean,
dry
hands.
DON’T use
DO treat a used bearing as carefully as a
new one.
DO use clean solvents and hushing oils.
DO protec t disassembled
DON’T handle
DON’T spin
DO lay bearings out on clean paper.
brittle
or
chipped
bearings with
uncleaned
bea rings from dirt and
bearings.
compressed
air.
DON’T use same c ontainer for c lea ning and final rinsing
rags if beorings are wiped.
tools.
dirty, moist hands.
DON’T spin any bearings with
moisture.
DO use clean, lint-free
dirty,
of
bearings.
DON’T use c otton waste o r dirty c loths to wipe bearings.
DO
keep
bearings
wrapped
in
oil-proof
paper
when
not in use. DON’T expose bearings to moisture or dirt at any time. DO
clean
inside
DO
install
new
without
of
housing
bearings as
before
removed
from
bearings.
packages,
DON’T scratch
or
nick
DON’T remove
grease
bearing
surfaces.
washing.
DO keep bearing lubricants
or oil
from new
bearings.
clean when applying and
cover containers when not in use.
14
replacing
DON’T use incorrect kind or amount of lubricant.
