Lubrication of Slewing Bearing

For a Slewing Bearing to function properly and provide maximum service life, proper re-lubrication and regular maintenance intervals are essential. The primary function of a lubricant is to create an oil film between the rolling elements and raceways as well as between the gears, to prevent metal-to-metal contact.

Slewing Bearings are generally lubricated with grease, which also provides added protection against the ingress of water and contaminants.

As Slewing Bearings normally operate at slow speeds, the free space between the rings can be filled entirely with grease.

Bearing Lubrication

Unless otherwise specified, SoCare® Slewing Bearings are filled with an NLGI class 2 mineral oil

based EP-grease containing a lithium soap thickener. This grease provides extremely good corrosion inhibiting properties and excellent mechanical stability. The grease has a temperature range of –20 up to +110 °C. 

Reliable lubrication according to the SoCare® traffic light concept is in the operating temperature range of +30 to +110 °C. SoCare® recommends re-lubricating Slewing Bearings with SoCare® EP 2, a mineral oil based grease with a consistency of 2 on the NLGI scale. In special cases, where the bearing must operate reliable at low temperature, an NLGI grease with a consistency of 1 or 0 can be used.

Slewing Bearings should be greased immediately after mounting, until fresh grease starts to escape from the seals around the whole circumference.

Gear Lubrication

The gear of a new bearing is normally coated with a preservative but is not greased.After the bearing has been mounted, a lubricant needs to be applied to the gear. This lubricant, which is usually grease, should have

• a base oil viscosity of at least 500 mm2/s at 40 °C

• good adhesive properties

• a high resistance to water washout.

In addition, the grease should be able to withstand temperatures of at least +100 °C.

Relubrication Intervals and Quantities


Relubrication should always be undertaken at a time when the condition of the existing  lubricant is still satisfactory. This time depends on many related factors including bearing type and size, operating temperature, frequency of operation, grease type and the  bearing environment. In order to facilitate good grease distribution, the bearing should 

always be re-lubricated while it is in operation.

The re-lubrication interval tf is an estimated value, valid for an operating temperature of 70 °C, using a good quality grease. If there are severe operating conditions, such as very dirty or damp environments or if operating temperatures exceed 70 °C, more frequent re-lubrication may be necessary. For additional information, contact the SoCare® application engineering service.

The new grease must be identical to, or miscible with, the grease already contained in the bearing. A mixture of two immiscible greases will impair the efficiency of the lubricant.