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LUBRICATION

(5) Mixing Different Types of Grease with increasing bearing load and size. Oil Replacement Intervals If moisture may enter or if foreign matter may be
Table 12.4 gives generally recommended viscosities for mixed in the oil, then the oil replacement interval must
In general, different brands of grease must not be bearings under normal operating conditions. Oil replacement intervals depend on the operating be shortened.
mixed. Mixing grease with different types of For use when selecting the proper lubricating oil, Fig. conditions and oil quantity. Mixing different brands of oil must be prevented for
thickneners may destroy its composition and physical 12.11 shows the relationship between oil temperature In those cases where the operating temperature is the same reason given previously for grease.
properties. Even if the thickeners are of the same and viscosity, and examples of selection are shown in less than 50˚C, and the environmental conditions
type, possible differences in the additive may cause Table 12.5. are good with little dust, the oil should be replaced
detrimental effects. approximately once a year. However, in cases where
Table 12. 4 Bearing Types and Proper the oil temperature is about 100˚C, the oil must be
12.3.2 Lubricating Oil Viscosity of Lubricating Oils changed at least once every three months.

The lubricating oils used for rolling bearings are Bearing Type Proper Viscosity
usually highly refined mineral oil or synthetic oil that at Operating
have a high oil film strength and superior oxidation and Temperature Table 12. 5 Examples of Selection Lubricating Oils
corrosion resistance. When selecting a lubricating oil,
the viscosity at the operating conditions is important. Ball Bearings and Higher than 13mm2/s Operating Speed Light or normal Load Heavy or Shock Load
If the viscosity is too low, a proper oil film is not Cylindrical Roller Bearings Higher than 20mm2/s Temperature Less than limiting speed −
formed and abnormal wear and seizure may occur. On Higher than 32mm2/s ISO VG 15, 22, 32 (refrigerating
the other hand, if the viscosity is too high, excessive Tapered Roller Bearings and − 30 to 0 °C machine oil)
viscous resistance may cause heating or large power Spherical Roller Bearings
loss. In general, low viscosity oils should be used at
high speed; however, the viscosity should increase Spherical Thrust Roller Bearings

Remarks 1mm2/s=1cSt (centistokes) Less than 50% of limiting ISO VG 32, 46, 68 (bearing oil, ISO VG 46, 68, 100 (bearing oil,
speed turbine oil) turbine oil)
0 to 50 °C
50 to 100% of limiting ISO VG 15, 22, 32 (bearing oil, ISO VG 22, 32, 46 (bearing oil,
Redwood Saybolt speed turbine oil) turbine oil)
(Seconds) (Seconds) mm2/s
More than limiting speed ISO VG 10, 15, 22 (bearing oil) −

5 000 5 000 2 000 ISO Viscosity Grade 50 to 80 °C Less than 50% of limiting ISO VG 100, 150, 220 (bearings oil) ISO VG 150, 220, 320 (bearing oil)
2 000 2 000 1 000 assumed V.I.80 speed
1 000 1 000 ISO VG 46, 68, 100 (bearing oil, ISO VG 68, 100, 150 (bearing oil,
500 A : VG 7 H : VG 100 50 to 100% of limiting turbine oil) turbine oil)
500 500 300 B : VG 10 J : VG 150 speed
300 300 200 C : VG 15 K : VG 220 ISO VG 32, 46, 68 (bearing oil, −
200 200 100 D : VG 22 L : VG 320 More than limiting speed turbine oil)
E : VG 32 M : VG 460
Viscosity 100 100 50 F : VG 46 N : VG 680 Less than 50% of limiting ISO VG 320, 460 (bearing oil) ISO VG 460, 680 (bearing oil,
80 80 40 G : VG 68 speed gear oil)
60 60 30 A B C D E F GH J KL MN 80 to 110 °C ISO VG 150, 220 (bearing oil)
50 50 20 50 to 100% of limiting ISO VG 220, 320 (bearing oil)
0 20 40 60 80 100 120 140 160 °C speed ISO VG 68, 100 (bearing oil,
40 40 10 20 40 60 80 100 120 160 200 240 280 320 °F turbine oil) −
More than limiting speed
5 Temperature
4 -20 Remarks 1. For the limiting speed, use the values listed in the bearing tables.
Remarks 2. Refer to Refrigerating Machine Oils (JIS K 2211), Bearing Oils (JIS K 2239), Turbine Oils (JIS K
-20 0
Remarks 2213), Gear Oils (JIS K 2219).
3. If the operating temperature is near the high end of the temperature range listed in the left column,
Remarks
select a high viscosity oil.
Fig. 12.11 Temperature-Viscosity Chart 4. If the operating temperature is lower than -30°C or higher than 110°C , it is advisable to consult

NSK.

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