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News Release from: AV Technology | Subject: AV Technology root cause analysis
Edited by the Engineeringtalk Editorial
Team on 26 March 2007
Analysis identifies recurring bearing
problem
AV Technology has a broad experience in providing structured and sustainable RCA solutions in industrial situations involving some form of persistent equipment failure.
Using root cause analysis (RCA), Stockport-based AV Technology (AVT) has identified the reasons behind a recurring bearing problem on a large electric motor operating at Solvay Interox' Warrington site AV Technology has a broad experience in providing structured and sustainable RCA solutions in industrial situations involving some form of persistent equipment failure
This article was originally published on Engineeringtalk on 11 Feb 2002 at 8.00am (UK)
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The 350kW, variable speed, inverter-driven motor drives a screw compressor providing process air for the Hydrogen Peroxide plant.
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AVT's Senior Engineer Andy Mellor explains how his company got to the root of the problem: "We were awarded a condition monitoring contract for the site and soon identified a developing bearing problem on the motor".
"A bearing change was scheduled for a production outage and we asked for the damaged bearing to be returned to us so we could conduct an RCA".
"Interviewing a range of staff, we found out that based on noise, bearings had been changed approximately every two years and the unreliability of the motor was well known".
"Inspection of the bearing revealed fluting on the outer race and darkening of the balls - a sure sign that an electric current was passing through the bearing during operation".
"A call to the motor manufacturer revealed that the bearing should have been insulated to prevent shaft voltages causing circulating currents to pass through the bearing and frame".
"The motor and plant were both mature - we believe that at some time in the past the insulated bearing fitted by the manufacturer was replaced by a motor repairer for a non-insulated type".
"Each time a replacement bearing was damaged through the passage of current another un-insulated bearing was fitted and the mistake had perpetuated". Request a free brochure from AV Technology ...
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