Temperature factor
Working temperature
Technical Characteristics
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Load capacity of cylindrical roller bearings
The dimensioning of cylindrical roller bearings is based on their load capacity and lifetime. About rotating bearings, the dynamic load coefficient must be taken into consideration; for roller bearings that have an occasional rotation, the static load coefficient must be considered. The load coefficients and the calculation procedures refer to DIN ISO 281/1 and ISO 76 regulations. Load capacities for cylindrical roller bearings are adequate to their practical use and performance.
Dynamic load capacity of cylindrical roller bearings
Dynamic coefficient “C” is necessary for the calculation of rotating bearings, that is to say bearings subject to dynamic strain. It indicates the maximum possible load that a bearing can bear (in Kg/N): in theory the lifetime is 1 million rotations.
Static load capacity of cylindrical roller bearings
Static coefficient Co is used for the calculation of non-
Axial load capacity of radial cylindrical roller bearings
C.R. cylindrical roller bearings can bear high axial thrusts and very high radial loads. The axial capacity of radial bearings depends on the dimensions of the edges, in relation to the front surfaces of the rolling bodies. The load capacity of the contact surfaces depends on the shearing speed and on the lubrication. With specific formulas it is possible to obtain axial load values that C.R. bearings can bear: continuous, temporary and alternate loads.
Lubrification
Regular lubrication and maintenance are essential for a long lifetime of revolving bearings. The lubricant has the following functions:
- It provides a film, which is enough to separate the surfaces of contact.
- It allows the removal of heat (oil lubrication)
- It prevents the entry of liquid or solid agents inside the bearing (grease lubrication).
- It decreases the noise of the bearing
- It protects against corrosion.
Revolving bearings can be lubricated – according to a technical choice – with grease or oil, depending on:
- Form of construction and dimension of the bearing.
- Type of execution of the housings and of the parts in contact with the bearing.
- Working condition.
Grease lubrication
The choice of the lubricant grease must be executed according to the specific instruction of lubricant suppliers. Revolving bearings are usually provided with lubricant greases that do not have high density at low temperature. Bearings working at high speed are provided with greases with low dynamic viscosity. In case the bearing is subject to high strain, C.R. recommends the use of EP greases and high viscosity of the oil.
Normally, the bearing should not reach higher temperature than 90° C. In this way, the characteristics of the grease will not be altered. The lifetime of the lubricant is influenced by environmental conditions. According to C.R. experience, the lifetime of the lubricant is guaranteed for three years, provided that the following conditions are fulfilled:
- Closed environment (warehouse)
- Temperature range 0°-
40°C - Air humidity below 70%
- Non-
contamination by chemical agents.
After 3-
In case the bearing is still functional, it must be cleaned and lubricated with the
same quantity of grease used which was used at the beginning. When possible, re-
The necessary quantity of grease can vary from 20% to 80% compared to the original one.
It is necessary to verify that the old grease can go out without any problem.
Lubrication range can be exactly calculated only with verifications made during real working conditions. It is possible to establish an indicative value of lubrication range following specific formulas.
Oil lubrication
Oil lubrication guarantees a good distribution of the lubricant and of the bearing surfaces. Oil lubrication is used when the mechanical elements adjacent to the bearing are already lubricated with oil, or in case it is necessary to remove heat from the support. Oils with mineral base or synthesis oils are suitable for oil lubrication.
Mineral oils with additive can be used for continuous working temperatures up to 120° C; synthesis oils up to 210° C.
For working security, C.R. recommends lubricant oils with EP additive.
They must be used in the following cases:
- Radial cylindrical roller bearings subject to very high loads and axial thrusts.
- Axial cylindrical roller bearings: before using lubricant oils, it is necessary to
verify their compatibility with plastic materials, non-
ferrous metals or light alloys.
These are the most popular lubrication systems:
- Drop oil lubrication: it is used for high speed radial bearings provided with a lubrication hole on the outer ring.
- Oil bath lubrication, immersion lubrication or oil sump lubrication: it is used for radial bearings.
- Oil mist lubrication, and oil-
air lubrication: they are particularly suitable for radial bearings working at very high speed with low load. - Oil recirculation lubrication: it is possible to filter the lubricant and cool it continuously. It is particularly suitable to remove heat from bearings working at high temperature.
During the run-
According to C.R. experience, it is enough to change the oil once a year, if the bearing temperature is kept below 60° C with a minimum amount of impurities.
In case of unfavourable working condition, C.R. recommends to control the lubricant on regular basis, according to the manufacturer’s instructions.
Assembling, disassembling and washing
C.R. cylindrical roller bearings are precision products.
This is the reason why they need to be treated with very high care, before and during the assembling. Correct functioning mainly depends on good maintenance.
Assembling
The environment where the bearings are assembled must be clean and without dust. Before the assembling, it is useful to have a suitable equipment and a press. If a press is not available, the assembling can be done by strokes on the bushing’s edges. Warning!
During the assembling, no thrusts nor strokes must be transferred on the revolving bodies! Deforming actions on the bearing rings must be avoided.
The assembling of the outer and inner rings can be facilitated by grooves or radii manufactured for this reason, and by a light lubricating treatment of the different surfaces.
The assembling of the inner rings on the shaft, with interference, is made through their heating with a suitable induction device.
If this device is not available, the heating of the rings can be done in an oil bath or in an oven at a temperature of about 110° C. C.R. recommends the cooling of the housing, before assembling the bearing in it.
It is necessary to make a working test of the bearing, once the assembling is finished.
Disassembling
During design phase, bordering holes or suitable cavities for the extractor should
be foreseen in order to allow the bearing to be disassembled. If the bearing is re-
Washing
The following cleansers can be used to degrease and wash the bearings:
- Water-
based cleansers - Organic cleansers
Water-
Organic cleansers are: petroleum, provided that it is without water or acids, -
Lifetime calculation
The lifetime of the bearing depends on the applied load and number of rotations, and it is calculated in the following way:
L = (C/P)p Lh=(16666/n) • (C/P)p
L=106
The lifetime of the bearings depends on the load. Rated duration in million of rotations, which is achieved or overcome by 90% of a representative number of equal bearings, before the material shows signs of wear.
Lh = h
Rated duration in hours of working corresponding to L.
C = N
Dynamic load coefficient. With reference to radial bearings, C corresponds to a load with constant entity and direction. The test on a representative number of bearings proved that the rated duration is one million rotations. With reference to axial bearings, C corresponds to the axial load which operates in central position.
P = N
Equivalent load on the bearings for radial or axial bearings.
P
Lifetime exponent
p=10/3 for needle roller and cylindrical roller bearings
n=min-
Number of rotations
Basic lubrication range
Basic lubrication range “tf” depends on the GKW speed coefficient and is shown in diagram 02 according to the following formula, considering KL bearing type, the number of rotation n and the medium diameter dM of the bearing.
GKW = KL • 270.000
(n • dM)
BEARING TYPE
Support rolls and cam followers, with full-
Support rolls and cam followers, with full-
Cylindrical roller bearings
Axial cylindrical roller bearings
KL
0,3
0,15
0,8
0,08
Tab. 01
GKW = Speed coefficient
KL = Tab 01
n = Number of rotation
dM = Medium diameter
PREMISES
Bearing temperature
Load ratio
Number of rotations and load
Load in the main direction
Lubrication grease
Rotation axis
Inner ring
Influence of the external
CONDITIONS
Up to 70°c
Co/p=20
steady
radial on radial bearing – axial on axial bearing
grease with lithium soap
horizontal for radial bearings
revolving
no influence
Premises about lubrication range
DIAGRAM 02
Basic
Lubrication
Range
Possibility of
re-
Re-
is necessary
a
b
Speed coefficient GKW
Static security coefficient
Static security coefficient defines the security grade against bearing deformations and is calculated with the following formula:
With a static security coefficient So < 8, the bearings are very pressed and with coefficient So•8, the bearings are medium or lightly pressed.
Approximate values of static security coefficient
Influence of temperature on the bearing
Temperature influences the bearing by decreasing the dynamic load capacity “C”; such output is calculated according to this correction formula:
The reduction of hardness due to the increase of temperature does not affect the static load capacity “Co”, therefore it can be overlooked for temperatures up to +300° C.
S0 = C0 / F0
S0 =
C0 =
F0 =
static security coefficient
static load coefficient
maximum load of the bearing
(N)
(N)
Silent working with few vibrations and normal working with minimum need for quietness:
bearing with minimum rotation.
Normal working with more need for quietness.
Working with high impact loads.
Supports with high demand for precision of rotation and quietness.
Application Case
SO
≥1
≥2
≥3
≥4
CT = fT . C
CT =
fT =
C =
effective dynamic load coefficient for high temperatures
temperature factor according to graph 03
dynamic load coefficient
Bearing clearance and working clearance
The good functioning of revolving bearings depends on a correct working.
This depends on radial clearance and on the change of radial clearance as a consequence of the assembling interference and of working temperature.
Working clearance
The radial moving of the shaft with regard to the outer ring of the bearing determines the working clearance.
The working clearance depends on the reduction of the radial clearance, as a consequence of the assembling interference and the temperature.
The reduction of the radial clearance of the assembled bearing – due to the couplings – is the result of the inner ring expansion and the contraction of the outer ring.
The difference of temperature between inner ring and outer ring can cause a reduction or an increase of working clearance
Radial clearance of the bearing
The radial clearance of the disassembled revolving bearing is expressed through the value of the radial shifting from edge to edge of the inner ring towards the outer ring.
The bearing radial clearance is divided into four groups (see table 04).
C.R. bearings manufactured with normal CN clearance guarantee a correct working clearance in normal working conditions, considering the suitable tolerances for shaft and housing. C3 and C4 radial clearances are taken into consideration for bearings having big dimensions, subject to high loads; in case of assembling interference and big difference of temperature between the inner ring and outer ring.
Bearings with C2 radial clearance are to be employed only in special cases (for example, in case of high combined alternate loads with swinging movements or a limited number of rotations).
In these particular cases it is highly recommended to check the bearings during the functioning, since they are subject to heating.
The values of C2, CN, C3 and C4 radial clearances are listed in table 05.
The customer must specify the bearing clearance, except for CN clearance.
MEANING
Bearing radial clearance lower than CN
Normal bearing radial clearance
Bearing radial clearance higher than CN
Bearing radial clearance higher than C3
FIELD
C2
CN
C3
C4
Tab. 04
More than
-
24
30
40
50
65
80
100
120
140
160
180
200
225
250
280
315
355
400
450
Tab. 05
Up to
24
30
40
50
65
80
100
120
140
160
180
200
225
250
280
315
355
400
450
500
min.
0
0
5
5
10
10
15
15
15
20
25
35
45
45
55
55
65
100
110
110
max.
25
25
30
35
40
45
50
55
60
70
75
90
105
110
125
130
145
190
210
220
min.
20
20
25
30
40
40
50
50
60
70
75
90
105
110
125
130
145
190
210
220
max.
45
45
50
60
70
75
85
90
105
120
125
145
165
175
195
205
225
280
310
330
min.
35
35
45
50
60
65
75
85
100
115
120
140
160
170
190
200
225
280
310
330
max.
60
60
70
80
90
100
110
125
145
165
170
195
220
235
260
275
305
370
410
440
min.
35
35
45
50
60
65
75
85
100
115
120
140
160
170
190
200
225
280
310
330
max.
75
75
85
100
110
125
140
165
190
215
220
250
280
300
330
350
385
460
510
550
d
C2
CN
C3
C4
Rated Ø of the
holes in mm.
Bearing radial clearance in µm.
Dimensional and tolerance symbols
d
Ddmp
Vdp
Vdmp
D
DDmp
VDp
VDmp
DBs
VBs
DCs
VCs
Kia
Kea
Sd
SD
Rated hole diameter
Tolerance of the medium diameter of the hole in a plan
Variation of hole diameter in a single radial plan
Variation of the medium diameter of the hole
Rated outer diameter
Tolerance of medium outer diameter in a single radial plan
Variation of medium outer diameter in a single radial plan
Variation of medium outer diameter
Tolerance of one single size of inner ring width
Variation of inner ring width
Tolerance of one single width of outer ring
Variation of outer ring width
Radial defect of inner ring rotation, to be measured on the assembled bearing
Radial defect of outer ring rotation, to be measured on the assembled bearing
Defect of quadrature of the surfaces with regard to the hole
Variation of outer cylindrical surface inclination related to lateral surfaces
circularity
parallelism
circularity
parallelism
parallelism
parallelism
concentricity
concentricity
flatness
flatness
Symbol
d
C4
Radial bearing tolerances
The tolerances of cylindrical roller bearings are according to DIN 620 part 2 and 3. Generally C.R. bearings correspond to PN class; in case of need of higher precision bearings, the tolerances can be reduced to the values of classes P6 and P5.
More than
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Tab. 06 -
Up to
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
max
10
10
10
13
15
19
25
31
38
44
50
56
63
-
-
-
-
-
max
8
8
8
10
12
19
25
31
38
44
50
56
63
-
-
-
-
-
max
6
6
6
8
9
11
15
19
23
26
30
34
38
-
-
-
-
-
max.
6
6
6
8
9
11
15
19
23
26
30
34
38
-
-
-
-
-
max
10
10
10
13
15
20
25
30
40
50
60
65
70
80
90
100
120
140
sup.
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
max
12
15
20
20
20
25
25
30
30
35
40
50
60
70
80
100
120
140
∆dmp
Vdp
Vdmp
VBs
More than
0,6 (*)
2,5
10
18
30
50
80
120
180
250
315
400
500
630
800
1000
1250
1600
Up to
2,5
10
18
30
50
80
120
180
250
315
400
500
630
800
1000
1250
1600
2000
inf.
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
d
8,9
0
2,3
mm
mm
Kia
∆Bs
Tolerance
Range of diameters
Tolerance
(*) This diameter is included
Tolerance values in µm
More than
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Tab. 06.1 -
Up to
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
max
10
10
12
14
16
19
23
31
38
44
50
56
63
94
125
-
-
-
-
max
8
8
9
11
13
19
23
31
38
44
50
56
63
94
125
-
-
-
-
max
6
6
7
8
10
11
14
19
23
26
30
34
38
55
75
-
-
-
-
max.
6
6
7
8
10
11
14
19
23
26
30
34
38
55
75
-
-
-
-
max
15
15
15
20
25
35
40
45
50
60
70
80
100
120
140
160
190
220
250
Identical to ∆Bs and VBs for inner ring of same bearing
(see tab. 06)
∆dmp
Vdp (**)
VDmp
VCs
More than
2,5 (*)
6
18
30
50
80
120
150
180
250
315
400
500
630
800
1000
1250
1600
2000
Up to
6
18
30
50
80
120
150
180
250
315
400
500
630
800
1000
1250
1600
2000
2500
D
8,9
0
2,3
mm
mm
Kea
∆Cs
Tolerance
Range of diameters
Tolerance
(*) This diameter is included
(**) Valid before the assembling of the bearing and/or after disassembling the outer and inner spring rings.
Tolerance values in µm
More than
0
0
0
0
0
0
0
0
0
0
0
0
0
Tab. 07 -
Up to
-
-
-
-
-
-
-
-
-
-
-
-
-
max
9
9
9
10
13
15
19
23
28
31
38
44
50
max
7
7
7
8
10
15
19
23
28
31
38
44
50
max
5
5
5
6
8
9
11
14
17
19
23
26
30
max.
5
5
5
6
8
9
11
14
17
19
23
26
30
max
5
6
7
8
10
10
13
18
20
25
30
35
40
sup.
0
0
0
0
0
0
0
0
0
0
0
0
0
max
12
15
20
20
20
25
25
30
30
35
40
45
50
∆dmp
Vdp
Vdmp
VBs
More than
0,6 (*)
2,5
10
18
30
50
80
120
180
250
315
400
500
Up to
2,5
10
18
30
50
80
120
180
250
315
400
500
630
inf.
-
-
-
-
-
-
-
-
-
-
-
-
-
d
8,9
0
2,3
mm
mm
Kia
∆Bs
Tolerance
Range of diameters
Tolerance
(*) This diameter is included
Tolerance values in µm
More than
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Tab. 07.1 -
Up to
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
max
9
9
10
11
14
16
19
23
25
31
35
41
48
56
75
max
7
7
8
9
11
16
19
23
25
31
35
41
48
56
75
max
5
5
6
7
8
10
11
14
15
19
21
25
29
34
45
max.
5
5
6
7
8
10
11
14
15
19
21
25
29
34
45
max
8
8
9
10
13
18
20
23
25
30
35
40
50
60
75
Identical to ∆Bs and VBs for inner ring of same bearing
(see tab. 07)
∆dmp
Vdp (**)
VDmp
VCs
More than
2,5 (*)
6
18
30
50
80
120
150
180
250
315
400
500
630
800
Up to
6
18
30
50
80
120
150
180
250
315
400
500
630
800
1000
D
8,9
0
2,3
mm
mm
Kea
∆Cs
Tolerance
Range of diameters
Tolerance
(*) This diameter is included
(**) Valid before the assembling of the bearing and/or after disassembling the outer and inner spring rings.
Tolerance values in µm
Class of Tolerance P6
Class of Tolerance PN (normal tolerance)
More than
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Tab. 08.1 -
Up to
-
-
-
-
-
-
-
-
-
-
-
-
-
-
max
5
5
6
7
9
10
11
13
15
18
20
23
28
35
max
4
4
5
5
7
8
8
10
11
14
15
17
21
26
max.
3
3
3
4
5
5
6
7
8
9
10
12
14
18
max
5
5
6
7
8
10
11
13
15
18
20
23
25
30
∆dmp
Vdp (**)
VDmp
VCs
More than
2,5 (*)
6
18
30
50
80
120
150
180
250
315
400
500
630
Up to
6
18
30
50
80
120
150
180
250
315
400
500
630
800
D
8,9
2,3
mm
mm
Kea
∆Cs
Tolerance
Range of diameters
Tolerance
Tolerance values in µm
Class of Tolerance P5
More than
0
0
0
0
0
0
0
0
0
0
0
Tab. 08 -
Up to
-
-
-
-
-
-
-
-
-
-
-
max
5
5
5
6
8
9
10
13
15
18
23
max
4
4
4
5
6
7
8
10
12
14
18
max.
3
3
3
3
4
5
5
7
8
9
12
max
4
4
4
4
5
5
6
8
10
13
15
sup.
0
0
0
0
0
0
0
0
0
0
0
max
5
5
5
5
5
6
7
8
10
13
15
∆dmp
Vdp
Vdmp
VBs
More than
0,6 (*)
2,5
10
18
30
50
80
120
180
250
315
Up to
2,5
10
18
30
50
80
120
180
250
315
400
inf.
-
-
-
-
-
-
-
-
-
-
-
d
8,9
2,3
mm
mm
Kia
∆Bs
Tolerance
Range of diameters
Tolerance
Tolerance values in µm
(*) This diameter is included
Identical to ∆Bs and VBs for inner ring of same bearing
(see tab. 08)
max
5
5
5
5
6
8
8
8
10
11
13
15
18
20
(*) This diameter is included
(**) Valid before the assembling of the bearing and/or after disassembling the outer and inner spring rings.
C.R. s.r.l. -
