This is a 1945 vintage OCB that we were asked to do an internal inspection on. We had done a sister unit the previous year. After the initial set up and drain of the tanks, the bushings were in the process of being cleaned when the bushing bases were found to be cracked. The cement that holds the porcelain in place had become porous and chalky. This became saturated with water and froze causing the cast aluminum base to expand and split. Hard to tell how long this condition existed. The unit was left out of service.


We did a similar project at another company with the same circuit breaker model and found the same condition. Not as many bushings had failed. We were able to take several good bushings from a scrap unit and repair their other in service OCB. The bushing bases were all inspected on the unit, cement cleaned up and sealed.

 

 

Out of the 6 bushings on this unit, 5 were found to have split bases. The customer was advised of this condition and our recommendation was that a new circuit breaker be purchased and the unit scrapped.

When the sister breaker was done, it required all new contacts. This one was in the same condition.

 

 

Bushing base with 2 cracks that go thru from the top to the bottom.