Repair – a valuable alternative to replacement
September 1st 2007

Bearing repair is not a new concept, nor has it changed a great deal over the years – and that's good news. Repairing damaged bearings is a precise science that has been fine-tuned over time through careful and gradual enhancements to provide superior results says Roger Oberweiser, business development manager, Metals at Timken Europe

Initial bearing design takes into account the use and application of the bearing and establishes an appropriate prediction for service life and fatigue life. No matter the design or manufacturer, bearings often deviate from these expectations due to factors such as contamination, inadequate lubrication or misalignment.

When a bearing is damaged, the entire operation of which it is a part will suffer.

Conventional practices would suggest that the damaged bearing would be scrapped and replaced. The growing popularity of bearing repair has helped companies understand its value by providing a more efficient or cost-effective way to resolve the problem.

Bearings often can be returned to original specification in less time and for less money than purchasing new ones. A quality repair and reconditioning program can result in significant savings.

Depending on the scope of work, bearing repair can save as much as 50 to 90% of the cost of purchasing new. Beyond the cost, repairs often save time compared to ordering replacement bearings, reducing costly downtime.

Deciding when to seek repair Although it offers many benefits, reconditioning is not always the best option for a damaged bearing. The challenge of properly using bearing repair services is determining if and when bearings need to be repaired, and deciding which option is the best economical and long-term decision.

Regular visual inspections serve as the first step in deciding if a bearing needs repair. Consider: The bearing is nearing or has exceeded its suggested life expectancy Operating temperatures have exceeded 200°F (93°C) Exposure to excessive vibration Sudden changes in lubrication and its temperatures Early detection of a problem through routine checks can spare unnecessary downtime and expense and help to capitalise on the capabilities and benefits of bearing repair. Regardless of the original bearing manufacturer, type of bearing or application, proper treatment may preserve the bearing and restore it to "like new" condition for continued use.

Bearings with little or no damage often can be reconditioned and recycled easily and at a low cost.

At The Timken Company, once a bearing is damaged, it undergoes a rigorous process to determine if it is a candidate for repair.

First, all bearings received for repair undergo a thorough cleaning process.

Next, and the most critical step, is a detailed inspection on 100% of the bearing. Inspection begins with a careful review for major damages such as fractures, major spalling or bluing due to excessive heat. Any evidence of these usually results in the scrapping of the bearing. If the bearing passes the first stage of inspection, it undergoes further review. This serves to reveal a mode of damage, assessment of damage and the scope of repair. The degree of bearing repair typically fits into three types.

Type I reconditioning is used for minor trouble spots and includes polishing, resetting of internal clearances, and spot grinding of any small surface defects to prevent further damage.

Bearings with more extensive damage require a Type II repair. This level involves major procedures such as regrinding of races, new spacers, and polishing of bore and cup outside diameter (OD). The regrinding of raceways will generally necessitate the manufacture of oversize rollers to maintain bearing geometry and clearance.

Type III remanufacturing takes Type II repair one step further by replacing one or more of the major components of the bearing that are not repairable.

These levels of repairs have traditionally been suited for bearings with a bore size of eight inches OD and greater. However, reclamation service, like the one provided by The Timken Company, cares for bearings as small as three inches in OD.

Smaller bearings that were often thrown away can now be handled if received in large quantities and returned to service.

Cleaning, inspection and the application of a polishing finish can return these used bearing to good-as-new condition for a fraction of the cost of replacement.

Turnaround time on reconditioning and repairs can be as short as 2 to 4 weeks, depending on the needed repairs.

Companies using bearing repair should always request a complete quote, including cost and estimated repair time, when requesting any type of repair service.

Common reconditioning mistakes include: Improper roller polishing that creates flat spots Excessive deep spot grinding Mixing of preset components In addition to expertise, proper equipment is required not only to fix the problem, but also to ensure all damage has been reviewed and addressed.

Magnifying glasses, proper lighting and measuring equipment are essential to perform thorough inspections and repairs.

For additional information on bearing repair services enquire below: