Ohio Electric Cooperative & Sonic Inspection

 

The Situation

On Aug. 7 and 8, 2018, Osmose inspected 36 poles on an Ohio electric cooperative’s distribution system that were inspected by a company utilizing their sonic inspection device earlier in the year. The original inspection company has been doing the coop’s pole inspections for a decade. Director of Business Development Paul Brewster convinced the pole owner to allow Osmose to perform partial excavations or full inspections on the group of poles. The only information available to us at the time of our inspections was whether the inspection company had passed or rejected the poles based on the tagging and flagging that was attached to each pole.

 

Inspection Example 1

   
 
Passed using sonic testing   Rejected after Osmose inspection
     

Inspection Example 2

   
 
Passed using sonic testing   Rejected after Osmose inspection

 

The Solution

The Osmose team inspected each pole by initially excavating the pole 360˚ to a depth of approximately 8 inches after performing a visual inspection. If external decay was observed, the pole was excavated to the depth required to effectively determine the extent of the decay and provide an accurate remaining strength (RS). After excavation, each pole was sound and bore inspected and any external decay was removed to determine RS. Poles with an RS of less than 67 percent were rejected. The coop’s Operations Manager witnessed several of the inspections.

As a result, Osmose passed six of the poles the original inspection company rejected and rejected six poles the original inspection company passed. With sonic testing specifically, pole attributes such as knots, wind-shake, checks, and environmental factors, such as high moisture, can produce inaccurate readings and is limited to locating internal decay. If a pole has decay several inches below ground, which is where decay is most likely to occur, sonic testing is unable to locate that decay.

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