29
OIMM – VENTUS PRO
Bearings have to be controlled and cleaned regularly; have to be lubricated adequately to prevent direct metallic
contact between rolling elements, to prevent wear and to project bearing surfaces against corrosion.
The fans with low shaft power are equipped with bearings in a rubber housing which absorbs a part of vibration.
When you change the bearing it is very important to change the rubber housing too. These bearings don’t need
to be lubricated.
The fans with higher shaft power are equipped with bearings with cast iron support. The lubricant filled in a bearing
gradually loses its lubricating properties during operation. Therefore, it is necessary for grease to be replenished
or renewed from time to time. The grease used is always lithium soap type suitable for all temperatures within
the operating range.
Excess grease will cause the operating temperature to rise rapidly, particularly when running at high speeds.
Therefore, only the bearing should be completely filled, whilst the free space in the housing should be partly filled
(between 30% and 50 %) Where bearings are to operate at very low speeds and must be well protected against
corrosion, it is advisable to completely fill the housing.
Relubrication interval depends on the fan speed and bearing internal diameter and is calculated by the following
formula:
t = 10 x {14x106 / (n x
√
d ) – 4 x d }
where:
t = relubrication interval ( h ),
n = fan speed ( rpm ),
d = bearing inner diameter ( mm )
If the fan works in particular conditions, relubrication intervals have to be corrected concerning the temperature
and surrounding factors, according to the following formula:
tc = t x kT x kS
where,
tc = corrected relubrication interval,
kT = temperature correction factor,
kS = surrounding correction factor
Temperature correction factor kT takes into account the reduction of relubrication interval when bearing
temperature raised over 70
º
C.
LUBRICATION OF BEARINGS
3.10.8
FAN SPEED
(rpm)
BEARING INNER DIAMETER (mm)
20
25
30
35
40
45
50
60
250
124 420
111 000
101 040
93 250
86 940
81 680
77 190
69 890
500
61 810
55 000
49 920
45 920
42 670
39 940
37 600
33 740
750
40 940
36 330
32 880
30 150
27 910
26 020
24 400
21 700
1000
30 500
27 000
24 360
22 260
20 530
19 070
17 800
15 670
1250
24 240
21 400
19 250
17 530
16 100
14 890
13 840
12 060
1500
20 070
17 660
15 840
14 370
13 150
12 110
11 200
9 650
1750
17 080
15 000
13 400
12 120
11 040
10 120
9 310
7 920
2000
14 850
13 000
11 580
10 430
9 460
8 630
7 900
6 630
3000
9 630
8 330
7 320
6 480
5 770
5 150
4 600
3 620
4000
7 020
6 000
5 190
4 510
3 930
3 410
2 950
2 110
5000
5 460
4 600
3 910
3 330
2 820
2 370
1 960
1 210
