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Acoustics used to monitor condition of 500-tonne hoists
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March 2008
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Corus Northern Engineering Services (CNES) is using acoustic emission techniques to monitor the condition of the main hoist gearboxes on the 500-tonne casting crane and the 500-tonne teeming crane, which are used to hoist ladles containing molten iron at the company’s BOS (Basic Oxygen Steelmaking) plant in Scunthorpe.
Acoustic emission monitoring techniques are ideal when it comes to monitoring the condition of critical, slow-moving (0.25-80rpm), high capital value plant and machinery, particularly where there are fluctuating load conditions and where a breakdown would have a significant impact on production.
After successfully using its in-house developed fixed acoustic emission monitoring system, Aquilla AE Pro, to monitor the condition of BOS vessel tilt bearings at Scunthorpe, CNES engineers are now using the portable version of the system, Aquilla AE Pro I-MON, to monitor the condition of the two 500-tonne overhead cranes, which are driven through two large epicyclic gearboxes.
The overhead cranes are used to move the ladles that carry molten iron to the BOS vessels. As Ian Taylor, business development engineer Plant Condition Monitoring at CNES explains: “Working with the gearbox manufacturer, we positioned five acoustic sensors on the outside of each gearbox, and four sensors on the inside of each gearbox, as close to the internal bearings as possible. Once each month, while the crane is in hoist mode, an engineer uses the I-MON portable monitoring system on the gearboxes to carry out a complete download of the acoustics emissions. After one year doing this, we’ve already got repeatability of data, which when analysed will enable us to predict the life of the gearbox.”
As part of Corus’ asset management programme, the two crane gearboxes are normally returned to the manufacturer for refurbishment after a maximum of five years of service. By monitoring the condition of the gearboxes with acoustics, Taylor believes the life of the gearboxes can now be increased, saving on refurbishment costs. But equally important, if any internal damage to bearings or gear teeth occurred earlier, for example, this can be picked up earlier than with the traditional planned maintenance route and the necessary repairs can be scheduled during the next available shutdown period.
Taylor added: “So far, we’ve found nothing that concerns us, as you’d expect with two relatively new gearboxes, but we’re already trending the data from Aquilla AE Pro I-MON.”
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Author
Chris Rowlands
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