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IR Inspections of Electrical Bus Ducts

Electrical bus ducts are a common feature found in many commercial and industrial electrical systems. When used to supplement regular PM, infrared inspections can help to detect loose or deteriorated connections that can lead to costly catastrophic failures.

Electrical bus ducts are used to distribute low voltage power throughout many industrial facilities. Modern bus ducts are unitized structures that contain insulated conductors within a steel casing. Individual sections of bus duct, each typically 10 feet long, are joined with bolted connections at the end of each bus section. Published industry standards recommend that bus duct connections be manually tightened every six months.

Even with regular tightening of bus duct connections, loose/deteriorated connections are difficult to detect. With the bus duct under load, a thermal imager can readily detect the temperature differentials associated with loose connections. Properly functioning bus ducts should exhibit no temperature differential in the vicinity of bolted connections. Because bus duct conductors are hidden from direct line of sight, any inexplicable temperature differentials should be investigated and corrected immediately. Disconnect switches and cable connections should be checked for thermal anomalies as well.

To ensure complete coverage, bus duct should be inspected from both sides of the duct along its entire length. Termination cabinets should also be inspected once the covers have been removed. Annual or semi annual infrared inspections performed by certified, experienced thermographers should be used to supplement regular bus duct maintenance.

Infrared inspection of bus ducts and electrical distribution systems are two of the many topics covered in the Level I Infraspection Institute Certified Infrared Thermographer® training course. For information on thermographer training or to obtain a copy of the Standard for Infrared Inspection of Electrical Systems & Rotating Equipment, visit us online at www.infraspection.com or call us at 609-239-4788.