Shaft Bearings

Bearing Refurbishment with DuraKapp™ Babbitt

There are typically four general steps in bearing surface refurbishment. Each is critical to the overall quality of the bearing surface:

1.   The old Babbitt is melted out of the bearing, and saved for recycling. Bearing surfaces are then typically cleaned with a solvent to remove any oil or other contaminant residues. On very well-worn and old surfaces, this can be the most difficult part of the bearing refurbishment. Often, the lubricants and contaminants have worked well into the Steel and old bearing Babbitt. You may find that you think the surface is clean, but on heating, more contaminants and oil surface from the Steel. These contaminants can be drawn out by alternating:

A) Heat while scrubbing with a Stainless Steel brush, and

B) Solvent treatments

Removing these contaminants is critical to a uniform Babbitt bond.

2.   Once the surface is clean and oil-free, the surface is typically “tinned” using either the same #2 Babbitt that forms the bearing surface, or a premixed Tin-Flux compound like KappaTinning™ Compound.

 In using the same #2 Babbitt wire, the surface is prepared using a chemical flux, heat is applied to the part (not the solder) and the wire is applied as evenly as possible. Then, the surface is LIGHTLY hand wire brushed to check the uniformity and bonding of the tinned surface. Any areas of imperfection or poor bonding are typically re-tinned using the same procedure.

 A pre-tinning compound like KappaTinning™ Compound contains a powder or crystalline flux and pure Tin powder. For example, our KappaTinning™ Compound is 50% Flux / 50% High Purity Tin. Remember that the main purpose of this tinning is to ensure a uniform bond between the Babbitt and the Steel bearing shell. Thus, even with pre-tinning compounds, the surface is still hand wire brushed to check the uniformity and bonding of the tinned surface. Any areas of imperfection or poor bonding are typically re-tinned using the same procedure.

3.   Once the bearing shell surface is prepared, the Babbitt surface layer is poured, laid down as a bead with automatic soldering equipment, or sprayed onto the tinned surface using a spraywire system.

4.   The final surface is prepared to specification. The process involved in this step depends greatly on the process in step 3. The bearing may require machine turning out, grinding and/or polishing to meet the final specifications. Always grind opposite to rotation and polish in the direction of rotation.

Engineering characteristics for common Babbitt alloys are shown below.

DuraKapp™ & KappaTinning™ Compound in Shaft Bearing Repair

In the rebuilding and repairing of engine, motor, generator, and rolling mill bearings, the first step is always to determine why the bearing surface failed. This will allow you to design a maintenance program going forward to avoid or minimize the chances of similar failure. Please review the article on “Babbitt Bearing Failure Analysis” to learn more about the causes of bearing failure and how to avoid them.

DuraKapp™ #1, #2, #3, and #4X Babbitt Bearings in Modern Rolling Mills

DuraKapp™ Tin-based Babbitt alloys #1, #2, #3, and #4X are the most common alloys for bearing linings in modern rolling mills. These Babbitt alloys offer an unsurpassed combination of compatibility, conformability, and embed ability. They easily bond to the bearing housing and will hold a lubricant film. Foreign matter not carried away by the lubrication is embedded below the surface and rendered harmless. Even under severe operating conditions, where high loads, fatigue problems, or high temperature test the limits of the Babbitt bearing, DuraKapp™ Babbitt alloys will retain their critical properties to protect vital rolling mill surfaces.

More information can be found at DuraKapp™ #1 Babbitt , DuraKapp™ #2 Babbitt , DuraKapp™ #3 Babbitt , and DuraKapp™ #4X Babbitt.

KappaTinning™ Compound for Preparing Bearing Shell Surfaces for New Babbitt

KappaTinning™ Compound is a dry mixture of pure powdered Tin and flux specifically designed for pre-tinning Cast Iron, Steel, Bronze, and Brass bearing shells. A one-pound container has about twice as much Tin and goes further than other tinning compounds currently on the market.

Applications

• Provides a uniform strong bond between the Babbitt alloy and the bearing shell surface on Brass, Bronze, Steel, and Cast Iron

Properties