Solvent cleaning of pole transformers containing PCB contaminated insulating oil

In 1989, it was discovered that the recycled insulation oil in pole transfo rmers for electric power supply was contaminated with trace amounts of poly chlorinated biphenyls (PCBs; maximum 50 mg-PCB/kg-insulation oil). In order to remove the PCBs from transformer components using n-hexane as a solvent , we investigated the relationship between progressive stages of dismantlin g and cleaning results. The results are summarized as follows: (1) Based on the cleaning test results, we made an estimate of the residual PCB amount on iron and copper components. By dismantling the test pole transformers in to the "iron core and coil portion" and cleaning the components, we achieve d a residual PCB amount that was below the limit of detection (0.05 mg-PCB/ kg-material). To achieve a residual PCB amount below the limit of detection for the transformer paper component, it was necessary to cut the paper int o pieces smaller than 5 mm. We were unable to achieve a residual PCB amount below the limit of detection for the wood component. (2) Compared to Japan 's stipulated limited concentration standard values for PCBs, the results o f the cleaning test show that cleaning iron or copper components with PCBs only on their surface with the solvent n-hexane will satisfy the limited co ncentration standard values when care is taken to ensure the component surf aces have adequate contact with the cleaning solvent. (C) 2001 Elsevier Sci ence Ltd. All rights reserved.