SKF insert bearings are supplied capped on both sides and are greased.
Insert bearings are filled with one of the following greases (table 1):
bearings with zinc-coated rings and stainless steel bearings
→ food-grade grease GFM, 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).
Additional certifications for the grease have been secured for use in halal and kosher food production processes.
all other bearings
→ standard grease VT307
- 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)
- horizontal shaft
- very light to moderate loads (P ≤ 0,05 C)
- stationary machine
- low vibration levels
- vertical shafts → 50% of the obtained value
- heavier loads (P > 0,05 C) → apply reduction factor (table 2)
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 that have lubrication holes, the following greases can be used:
- SKF LGWA 2
- SKF LGMT 2
- SKF LGMT 3
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.
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 insert bearings are lubricated for life and cannot be relubricated. They do not have any lubrication holes:
Bearings with grub screw locking:
- with zinc-coated rings
- made of stainless steel
- Bearings with a standard inner ring without designation suffix B
- Bearings with 5-lip seals