REXROTH IndraDyn A Series, Project Planning Manual

Page: 186 / 220

9-30
Application Notes Rexroth IndraDyn A
9.16 Grease Service Life
The grease service life (t
f
) is the time from the start until the failure of the
bearing as a result of a failure of the lubrication.
Please observe that unfavorable operating and environmental conditions
result in a reduction of the grease service life. When determining the
expected grease service life (t
fq
), certain reducing factors for unfavorable
operating and environmental conditions must therefore always be taken
into consideration for each individual application. The following table
indicates the reduction factor, based on the FAG Kugelfischer AG
Publication No. WL 81 115/4 DA.
Description Description Influence Factor Note
moderate 0.9....0.7
severe 0.7....0.4
Influence of dust and
moisture on the
functional surfaces of
the bearing
f
1
very severe 0.4....0.1
Rexroth offers the „radial shaft seal“
option for this environment.
By the use of this option
f
1
= 1
moderate 0.9....0.7
e.g. in machine tools and printing
machines
severe 0.7....0.4 e.g. in conveying equipment (gantries)
Influence of load due
to shock, vibration and
oscillations
f
2
very severe 0.4....0.1 e.g. in punches and pressers
moderate (to 75°C) 0.9....0.6
severe (75...85°C) 0.6....0.3 Influence of high
temperatures
f
3
very severe
(85..0.120°C)
0.3....0.1
The bearing temperature depends on the
load on the motor.
Through the use of a special high-
temperature grease the following load
results in the following factor:
- load 0...70% f
3
= 1
- load 71...100% f
3
= 0.99...0.7
P/C=0.1...0.15 1.0....0.7
P/C=0.15...0.25 0.7....0.4
Influence of a high
load
f
4
P/C=0.25...0.35 0.4....0.1
With a corresponding load to the
shaft/bearing acc. to the respective shaft
load diagram, the following results for
IndraDyn A motors
- load 0...70% f
4
= 1
- load 71...100% f
4
= 0.99...0.7
low currents 0.7....0.5
Influence of air
currents through the
bearing
f
5
high currents 0.5....0.1
In proper operation, there is no effective
air current in the motor
f
5
= 1
In case of a centrifugal
effect or vertical
installation, depending
on the type of seal
f
6
vertical 0.7....0.5
When the motor is installed horizontally
f
6
= 1
Fig. 9-35: Factors that reduce the grease service life
6 5 4 3 2 1 f fq
f f f f f f t t
⋅ ⋅ ⋅ ⋅ ⋅ ⋅ =
Fig. 9-36: Calculation of the grease service life to be due
Note:
Ensure that the permissible loads in Chapter 9.13 “Bearing
and Shaft Loads”, are not exceeded.
Reduction Factor
Calculation