Relubrication

SKF ConCentra roller bearing units are typically relubricated in order to realize maximum service life. All bearing units have a lubrication hole with a 1/8-27 NPSF thread. They are provided standard with a grease fitting AH 1/8-27 PTF, except for the relubrication-free variant, which has the lubrication hole plugged.
Relubrication intervals

The relubrication interval tf for SKF ConCentra roller bearing units excluding the relubrication-free variant can be obtained as a function of:

  • the operating temperature
  • the rotational speed n [r/min]
  • the bearing mean diameter dm [mm] (table 1)
  • the bearing factor bf (table 1, for values of e)
    – bf = 2  when Fa/Fr ≤ e
    – bf = 6 when Fa/Fr > e
  •  the load ratio
    – P ≤ 0,05 C (diagram 1)
    – P = 0,1 C (diagram 2)
    – P = 0,15 C (diagram 3)

The basic dynamic load rating C is provided in the product tables for units in the SYNT series and FYNT series. The equivalent dynamic bearing load P can be obtained from 

P = Fr + Y1Fa  when Fa/Fr ≤ e
P = 0,67Fr + Y2F  when Fa/Fr > e

where
P = equivalent dynamic bearing load [kN]
Fr = radial component of the bearing load [kN]
Fa = axial component of the bearing load [kN]
Y1,Y2 = axial load calculation factors for the bearing (table 1)
e = limiting value for Fa/Fr (table 1)

The calculated relubrication intervals represent the grease life L1, which relates to the time period at the end of which 99% of the bearing units are still reliably lubricated. The intervals are estimated values, applicable for bearing units mounted on horizontal shafts in a relatively clean environment. When operating conditions differ, the relubrication intervals should be adjusted as follows:

  • For a vertical shaft, the interval should be halved.
  • For outer ring rotation or rotating load, the interval should be halved.
  • For contaminated environments, the following reduction factors should be used:
    – 0,5 for moderate contamination
    – 0,3 for severe contamination
    – 0,1 for very severe contamination


Relubrication procedure
Before relubricating, the grease fitting and the area surrounding it should be cleaned. High-pressure cleaning equipment should be avoided. During relubrication, grease should be introduced via the grease fitting (fig. 1) while the shaft is rotating slowly. Excessive pressure and over-greasing should be avoided,otherwise the seals may be damaged.
Relubrication quantity
The appropriate quantity of grease for relubrication of SKF ConCentra roller bearing units is provided in table 2.
Greases for relubrication
To relubricate SKF ConCentra roller bearing units, SKF recommends using SKF LGEP 2 grease, which is fully compatible with the original grease introduced at the factory. Other compatible greases such as SKF’s multi-purpose LGMT 2 and LGMT 3 greases can also be used.
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