How bearings are remanufactured

Perhaps the most significant way to optimize bearing life is to take advantage of bearing remanufacturing. Repaired bearings, given proper maintenance and usage, will have a life equal to or greater than that of a new bearing. The key is an effective preventative maintenance program that removes the slewing ring bearings from the fleet for repair before significant wear takes place. Most thrust and radial bearings, multi-row ball and roller bearings, tapered roller bearings, and thin-section bearings from 8" to 20' in diameter can be economically remanufactured. This approach not only reduces downtime significantly, but also lowers replacement and inventory costs. In addition, remanufacturing provides a product that meets or exceeds new equipment standards.

Typically, a bearing is remanufactured within a two- or three-week lead time and at about half the cost of a new replacement. In emergencies, a 24-hour repair service may be available. If the bearing is deemed unrepairable, a new replacement can be supplied. Look for a one-year warranty, whether the bearing is new or repaired.

The process begins with a thorough inspection of the bearing. Inspectors first measure and document critical dimensions. Then the bearing is disassembled and cleaned to prepare it for non-destructive testing. A magnetic particle inspection is performed in order to detect cracks or defects.

Engineers carefully examine the test results and establish whether the bearing meets the criteria for remanufacturing. For example, if excessive wear is apparent, or if defects or impurities are found in the raceways, the bearing is eliminated as a candidate for the remanufacturing process.

If the bearing is found to meet the criteria, an appropriate remanufacturing sequence is established. The specific operations vary depending on the results of the engineering analysis.

In remanufacturing, the bearing is precision-ground to standards higher than those used for new bearings. For instance, a new slewing ring bearing typically has mounting faces machined to an axial runout of 0.005–0.010 inches; for a remanufactured slewing ring bearing, axial runouts range from 0.0002–0.0030 inches. The raceways are individually ground, whereas new bearings may be ground in large lots and therefore do not receive the same type of individual attention.

The internal geometry of the bearing is another important factor to consider. Operators take care to grind raceways to the correct geometry in order to optimize the load-carrying capacity. For example, most crane applications utilize a four-point contact bearing with a 60-degree contact angle. In tapered roller bearings, the extensions of the lines of contact between rollers and raceways must all meet at a common axis of the bearing.

After regrinding, the bearing is then reassembled with new seals, rolling elements, and separators or cages. The new raceway components are slightly oversized in order to compensate for the material removed during grinding. Thus the remanufactured bearing has an internal geometry identical to the original bearing.

After assembly, each bearing is lubricated, inspected, and serialized for traceability.

Proven performance
The US military has been a proponent of bearing remanufacturing for more than 40 years.

• Remanufacturing is aggressively pursued even in the most critical applications, such as aerospace. The US Air Force San Antonio Air Logistics Center has a comprehensive remanufacturing facility serving the US Air Force.
• Search, radar, and communication antennas are integral systems in US Navy vessels. Hundreds of precision antenna bearings are remanufactured annually by commercial bearing manufacturers.
• The US Army remanufactures hundreds of thousands of dollars worth of bearings annually at their tank refurbishment operation at a dedicated remanufacturing facility in Anniston, Alabama. These bearings are utilized in tank turrets and gun mounts.

Payoffs
Many industries rely heavily on equipment and machinery that rotate on large bearings. New replacement bearings usually cost several thousand dollars and can take months to deliver. However, a remanufactured bearing can be supplied at about half the cost of a new one, with a standard lead time of only 2-3 weeks. Another option is to replace the worn bearing with a new one, and have the worn bearing remanufactured to maintain as a spare. Either option provides sizable savings in both time and money.

Consider Kaydon
At Kaydon, the same equipment used to manufacture new bearings is used in the remanufacturing process. In addition, the same stringent quality control standards that apply to new bearing production are applicable to remanufactured bearings. Kaydon offers warranties for remanufactured bearings that are equal to those offered for new bearings. Learn more about the Kaydon Bearing Remanufacturing Program.