Testing Not Enough, Transformer Damage By Chains Was Junk
MIDWEST was asked if we ever rejected a transformer even though it passed all our electrical tests. The answer was “yes.” We scrapped an old 1000 kva dry type transformer used in a fairly clean room. We had purchased the old transformer after replacing it with a larger unit in a paper mill. The transformer was trucked to MIDWEST. But an outer high voltage winding had physical damage that was found during the “hard focus” visual inspection. The riggers had damaged the outside of one winding with the tie down chains. All the standard test results were very good. And we energized the transformer at full voltage. Everything tested out great. But our inspection told us the transformer could not be used. It was junk. Not worth repairing. It had what we call an “Incipient Failure.” It was damaged and was going to fail. When, who knows. A day, a week, two years? We didn’t know. But we did know it was not reliable. The high voltage windings were going to fail, short out. It was just a matter of time before the used transformer became scrap. We just hurried it up and declared it junk. Here is another great example of pure technical knowledge just not being enough. Experience and Knowledge were needed.