May 2022 Volume 4

EQUIPMENT & TECHNOLOGY

Loose Connections, Melted Connections Example 1: Busbar Links

Following a breakdown repair of a billet heater at Company A, the customary thermal imaging inspection performed during normal operation revealed a bus ‘link’ connection with a temperature greater than expected for the given conditions.

Image 6: Melted stud on resonant capacitor. Photo courtesy of Integral Power Technologies, LLC. Example 3: Incorrect Hardware Company C requested a maintenance program to improve the overall reliability of their legacy induction units. The intention was to make the units run long enough so that new induction heaters could be ordered and installed. During preliminary inspections it was observed that bolted connections on busbars and links had oversized slots and undersized hardware. The maintenance personnel attempted to compensate for the flaws by stacking washers to provide enough rigidity to keep the connection tight.The conditions reduced reliability and contributed to a lack of confidence in the equipment. To correct the problem, the heavy brass washers seen on the right side were custom specified to correct a problem created by the oversized slots. The left shows a previous attempt to fix it by stacking washers was only partially successful.

Image 4: Infrared image of suspect bus link. Courtesy of Integral Power Technologies, LLC. The link was disassembled, and it was found that significant oxidation of the connection and arcing had occurred. Post analysis concluded that loose hardware, debris, and lack of maintenance contributed to the breakdown.

Image 5: A ‘well-seasoned’ copper bus link, after discovery by infrared imaging. Photo courtesy of Integral Power Technologies, LLC. Example 2: Loose Hardware Company B put in a service call to look at an induction power supply that had problems running at the rated capacity. This resulted in decreased production rates and delays in order fulfillment. The cause? The nut fastening a resonant capacitor terminal to a busbar together came loose and melted, causing arcing. The result was that only some of the available reactive current could be delivered to the inverter. While checking the other fasteners, several more were discovered to be loose.

Image 7: Incorrect hardware contributes to unreliability. Photo courtesy of Integral Power Technologies, LLC.

FIA MAGAZINE | MAY 2022 11