Electrical Troubleshooting Quiz, Sept. 25, 2012

Your facility's electrical testing firm preformed a plant-wide thermographic imaging survey and it confirmed some anomalies

Recently, your facility's electrical testing firm preformed a plant-wide thermographic imaging survey. Unfortunately, it confirmed some anomalies discovered during the normal thermography scans conducted as part of some PMs. Last year, the same survey showed a huge number of overheated connections.

The amount of work required to fix these was beyond the capability of the maintenance department, so a contractor was awarded that work. The fact the problem has come back so soon prompted a visit from the Division VP, who wants to know what's going on and how you're going to fix it.

What are some issues to explore?

Determine if the contractor tightened the loose connections without using torque wrenches/ screwdrivers. Though a typical cause, it might be one of several. Also take these steps:

  • Characterize the failures. Make a spreadsheet showing failure by voltage level and application.
  • Examine the repair methods. You can usually get by with retightening low-current, low-voltage connections in, say, a control panel. But almost anywhere else, it's critical to use new hardware and correctly torque it. Replace, don't retighten.
  • Reduce thermal cycling. Use thermographic surveys to determine thermal cycling risks. Reduce the heat peaks by installing cabinet coolers. Consider using the refrigerant-free devices that refrigerate using plant air.
  • Mitigate vibration. You may need to "stiffen" the mechanical aspects of cabinets and panels. Consider installing isolation devices and/or adopting seismic standards.
  • Buy accessories. In nearly all cases, today's test equipment accessories eliminate the need to break connections to measure.
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