Abstract
In 1989, trace of PCB (less than 50 mg PCB/kg insulation oil) was found in reclaimed oil used in some pole transformers. It was keenly required to remove the detrimental PCB in a reliable method.
Elimination demonstration tests of PCB and the like were carried out by a solvent cleaning technique using some local transformers operating in site. They were broken down into classified metals by way of chilled crushing, and were subjected to preliminary cleaning for five minutes and then secondary cleaning for ten minutes, thus obtaining harmless iron, coppers and porcelains which could reduce their residual PCB lower than the lowest determination limit (0. 05 mg of PCB/kg of parts). Similarly, papers and woods were subjected to preliminary cleaning for sixty minutes and then secondary cleaning for six hundreds minutes, thus reducing their residual PCB at lower then the lowest determination limit, depending on the types of transformer. Further these tests demonstrated that the solvent cleaning system adapted for this test could be reliably operated, thus securing the ambient and work-environmental safety.
