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BEARINGS, SEALS & GASKETS FEATURE Bearings: Replace or remanufacture?


That old adage, ‘make do and mend’, has new resonances for companies planning for the future and who may be having difficulties deciding which is wisest: to discard and


replace worn machinery and parts, or to remanufacture. Paul Dysiewicz, engineering manager at SKF, comments


R


egardless of how well they may be engineered


and cared for in service, all rotating, reciprocating or otherwise moving mechanical components will eventually wear and need to be replaced. Taking bearings as an example, the question arises: should a worn bearing be replaced by a completely new, identical one, or would the better option be to recondition or repair the existing unit? Where small bearings are concerned, replacement is probably best because costs are only likely to be mitigated if large volumes of units can be remanufactured in batches. However, for medium to large or specialised bearings, the cost of remanufacturing a single unit is


significantly less than the cost of a new replacement. Moreover, the amount of energy needed to complete a repair job can be up to 90% less than that needed to manufacture from scratch, depending upon the amount of remanufacturing required. Larger, specialised, bearings are likely to involve long manufacturing lead times should a replacement be the chosen option.


Remanufacturing is possible in over 50% of applications


REMANUFACTURING Remanufacturing is possible in over 50% of applications and it may also be possible to remanufacture a bearing, particularly an older one, to a higher standard of quality,


With the belt tensioner serving one of its food conveyors failing every four weeks, a frozen pizza manufacturer turned to NSK for help. Within the framework of NSK’s Added Value Programme (AIP), experts inspected the failed bearings and determined that the damage was mainly due to the production line being frequently cleaned using water. This was damaging the bearing seals, as well resulting in corrosion of the rolling elements and raceways. In addition to this, lubricant was being washed out of the bearings. To solve the problem, NSK recommended


NEW BEARINGS HELP PLANT SAVE €15,360 PER YEAR According to the company, in applications


where the operating environment is moist and dust-contaminated, the service life of Molded-Oil bearings is more than twice that of bearings with conventional grease lubrication. Following the installation of


Molded-Oil bearings at the pizza plant, there were no more failures for a whole year. With the only cost being the investment in the bearings themselves, and the previous costs associated with


bearing replacement, maintenance and lubrication being eliminated, the plant will benefit from annual savings of €15,360.


replacing the existing standard bearings with stainless steel Molded-Oil versions. As well as preventing the ingress of contaminants such as water and particulates, no lubricant can escape the bearing and enter other parts of the machine, where it could potentially contact food. Molded-Oil bearings are equipped with a


proprietary oil-impregnated material that consists of lubricating oil and a polyolefin resin with an affinity for oil. This carrier material releases the lubricant continuously over a long period.


NSK www.nskeurope.com


enabling them to perform better, and for longer, than the original part. Even more compelling, it is possible to save as much as 80% of the cost of a new bearing by remanufacturing it rather than replacing it with a new unit. Typical candidates for remanufacturing


come from a very wide range of heavy industries and include medium to large sized bearings of most types, such as caster bearings, backing bearings, slewing bearings and railway bearings. Bearing housings can also be remanufactured. To determine whether a bearing is


suitable for remanufacture, the installation needs to be inspected to understand why the bearing became worn or, indeed, failed in the first place. A replacement or remanufactured bearing will be subject to the same conditions on reinstatement and may suffer similar problems in service, unless the root cause of the problem is identified and remedial action taken. The next stage is to disassemble the


bearing in order to assess the degree of damage to its component parts. A variety of tools are available to facilitate this, including visual inspection and crack detection, surface hardness measurement and dimensional gauging. Ultrasound testing may be needed to detect otherwise invisible subsurface micro-cracks. A remanufacturing expert, such as


SKF, would subsequently issue a report on these detailed inspection stages, which would provide estimations of remedial work required, how long the job would take, and the costs involved. Of course, it may be judged that the bearing is beyond repair. The remanufacturing procedure itself will be dictated by the severity of the damage and will range from simple polishing and the reuse of existing components, to the wholesale replacement of the bearing’s rolling elements and the regrinding of its raceways. Bearing remanufacturing, especially


if used in conjunction with techniques such as condition-based monitoring, can play an important role in helping manufacturers to reduce their costs, cut their carbon footprint and improve return on investment. Just as importantly, the relatively short lead times of a remanufacturing project mean that, with careful planning, bearings can be remanufactured during normal line shutdown, thereby minimising any loss of productivity.


SKF www.skf.co.uk  DESIGN SOLUTIONS | MAY 2019 17


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