Getting the best out of industrial gearboxes
In any industrial environment, the management of plant-critical assets is integral to maintaining productivity and reducing downtime, says Jeremy Salisbury.
At the heart of many manufacturing processes, the industrial gearbox often has to perform under arduous conditions. Employing effective maintenance and repair procedures can significantly reduce the risk of premature gearbox failure. Indeed, paying particular attention to factors including lubrication, oil and vibration analysis can help sustain a gearbox's service life, avoiding costly replacements and rebuilds.
Where unplanned downtime is simply not an option, gearboxes must be inspected regularly and repaired and refurbished as necessary to allow their continued operation. In addition to regular visual inspections, one way in which companies can help to maintain production schedule adherence and maximise production efficiency and asset effectiveness is by using condition monitoring equipment. Condition monitoring - for example vibration analysis - can help identify a problem before it leads to a line stoppage, allowing for maintenance to replace or repair the gearbox, with minimal disruption, during the next convenient plant downtime. Furthermore, it removes the need for gearboxes to be changed on a time basis - possibly when change may not be required - and instead allows for change on a condition basis, which can extend service life and maintenance intervals.
The problems of contamination
As with many other industrial components, contamination is a major cause of gearbox problems. Oil contamination can result in reduced operating life in rolling element bearings. Any failure of these bearings will certainly damage other components and may lead to catastrophic failure of the gear train. Water contamination of gear oil will cause the oil to break down, affecting the performance of the oil between the teeth of the running gear train, causing increased wear rates. Finally, corrosion-induced fatigue failure is a possibility if pitting is allowed to occur. However, this is a far less likely outcome than a problem created by solids in suspensions and sludge formation inside the unit: these issues can be minimised through regular, planned maintenance. A detailed maintenance schedule with reports on condition and actions undertaken is also critical to maintaining the conditions of warranties and guarantees.
It goes without saying that gear oil should be changed at the interval specified by the manufacturer. If contamination is an issue, additional filtration systems may be required.
Noise and vibration analysis of the gearbox under normal operating conditions will help identify any problems, and a detailed visual inspection should also occur. For this, the gearcase inspection covers should be removed, with the interior inspected for any signs of contamination and the gear teeth and rotating components checked for visible wear.
A full inspection, required less frequently, should involve removing gear internals from the gearcase, removing shaft end covers, inspecting bearing bores, removing sludge deposits and thorough cleaning. The gear train should be completely dismantled, with all components cleaned and inspected. All oilways should be checked to ensure they are clear, and any sludge removed, gears and shafts should be checked for excessive wear, cracking and concentricity. Once these steps have been taken, the gearbox can be reassembled and reconnected.
Industrial gearboxes generally have a considerable service life and, if they do fail, can usually be repaired or reconditioned. However, their performance and energy efficiency even after reconditioning may make replacement with a more energy-efficient product advisable. Each application should therefore be thoroughly examined and a decision made as to whether replacement is the right way forward. Energy savings of up to 20% are achievable over traditional worm boxes by installing either a helical bevel or planetary gearbox, depending on the application.
In plants with numerous gearboxes, maintenance time can be considerable, particularly if maintenance intervals are simultaneous, placing an undue burden on in-house maintenance teams. An increasingly popular option is to outsource the entire gearbox management and maintenance function to a specialist partner familiar with all makes of gearbox. Outsourcing in this way gives the flexibility for gearboxes to be overhauled at the same time, with independent advice available on when it makes more sense to replace than to repair, and on the most economical and energy-efficient way forward when replacement is indicated. The partner can also supply and configure all new gearboxes as well as developing a detailed maintenance regime.
The availability of a reliable partner for technical support and advice, product supply and repair is delivering major benefits for many companies who are enjoying more efficient operation and reduced energy bills from the service and advice they are receiving.
Jeremy Salisbury is head of marketing at Brammer UK
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