Lubrication

SKF insert bearings are supplied capped on both sides and are greased.

Greases for capped bearings

Insert bearings are filled with one of the following greases (table 1):

  • zinc-coated and stainless steel insert bearings
    → food-grade grease GFJ, registered by NSF as category H1
    The NSF registration confirms the grease fulfils the requirements listed in the US Food and Drug Administration's guidelines under 21 CFR section 178.3570 (lubricant acceptable with incidental food contact, for use in and around food processing areas).
  • all other insert bearings
    → standard grease VT307
Grease life for insert bearings
  • is presented as L10, i.e. the time period at the end of which 90% of the bearings are still reliably lubricated
  • depends on the load, operating temperature and the ndm value (diagram 1)
The indicated grease life is valid for the following combination of operating conditions:
  • horizontal shaft
  • very light to moderate loads (P ≤ 0,05 C)
  • stationary machine
  • low vibration levels
Where the operating conditions vary, the grease life obtained from the diagram should be adjusted as follows:
  • vertical shafts → 50% of the obtained value
  • heavier loads (P > 0,05 C) → apply reduction factor (table 2)
The values for adjusting the grease life are estimates. Vibration can have a negative influence on grease life. The extent cannot be quantified, and the influence increases with increasing operating temperature.
Relubrication

Insert bearings do not need relubrication if the grease life (→ Grease life for insert bearings) exceeds the SKF rating life of the bearing.

Relubrication can extend bearing service life under any of the following conditions:

  • The bearings are exposed to high humidity or severe contamination.
  • The bearings accommodate normal or heavy loads.
  • The bearings operate for extended periods at high speeds or at temperatures above 55 °C (130 °F).
  • The bearings are subjected to high vibration levels.

To relubricate insert bearings, the following greases can be used:

  • zinc-coated and stainless steel insert bearings
    → food-grade grease SKF LGFP 2
  • all other insert bearings
    → SKF LGWA 2, LGMT 2 or LGMT 3 grease

If relubrication is needed, the relubrication intervals can be estimated by following the method explained under Estimating the relubrication interval for grease.

When relubricating, the shaft should be turned and the grease pumped slowly until fresh grease starts to escape from the seal(s). Excessive pressure from pumping too quickly can damage the seals. When machines and equipment are used for a limited period of time, SKF recommends relubricating each bearing at the end of the operational period, i.e. immediately before being laid up.

Relubrication features

SKF insert bearings are designed to facilitate relubrication. They have two lubrication holes in the outer ring as standard, one on each side, positioned 120° apart. Bearings without lubrication holes can be supplied on request (designation suffix W).

The following bearings do not have the standard relubrication features:

  • Stainless steel insert bearings with grub screws have a lubrication groove in the outer ring located on the side opposite the locking device and one lubrication hole within this groove.
  • Insert bearings with a standard inner ring without designation suffix B and insert bearings with 5-lip seals are lubricated for life and cannot be relubricated. They do not have any lubrication holes.
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