Polychlorinated biphenyls (PCBs)

Polychlorinated biphenyls (PCBs)2023-05-09T12:08:34+00:00

With the best of intentions, good but bad

PCB transformer oil in Australia would certainly represent less than 10% of the transformer oil in service.  But the legislative, environmental, safety and commercial issues that surround its handling, raise this issue to one of great importance.

Although an excellent insulating fluid (a non-flammable liquid with no fire point), polychlorinated biphenyls (PCBs) were found to be probably carcinogenic and certainly environmentally toxic.  Their production and use has been outlawed in most countries for over 30 years.  Despite the ban, transformers and high voltage equipment in service today still often contain remnants of PCB contaminated oil.

Pure or highly concentrated PCB oil is increasingly rare to see, as these instances were likely flagged as high risk many years ago and dealt with accordingly at the time.  Nevertheless some smaller sealed units may have unknown (and sometimes high) PCB levels.  In these cases Benzoil can offer a sampling service where our experienced technician can attend site draw a sample.  The oil sample is then conveyed to a NATA accredited laboratory for analysis, with the result reported usually within a week.  Now that the PCB level is known, next steps can follow.

Although rare, some older equipment will pre-date the ban on PCB use, and if well-built and lovingly maintained these assets may still be in service.  Indeed despite being more than 40 years old some power transformers are still operating today.  This is testament not only to quality craftsmanship, design and materials, but also to the diligence of multiple generations of engineers who have properly monitored and serviced the equipment.  Transformers of this age would certainly have had oil changed out in this time, but depending on the starting level of PCB and number of oil changes some degree of PCB in the oil may still remain.

As a rule of thumb, the PCB level in a transformer is reduced to 10% of its original level once a full retrofill (oil change) is done.  This 10% comes from oil that impregnates the paper windings – as it mixes with new clean oil, the PCB levels find an equilibrium.

Sometimes to the dismay of transformer owners, a relatively new asset may test positive for PCB.  How could this happen?  Careless maintenance practices may have caused cross-contamination, so for instance equipment like a pump or filtration equipment is used on a PCB oil project and then (without being properly decontaminated) used subsequently on another oil project.  Residual PCB oil in the equipment contaminated the “clean” equipment.

Benzoil can provide access to these PCB related services:

  • Disposal (dechlorination) of PCB oil
  • NATA accredited laboratory PCB testing and analysis
  • Oil sampling and data collation
  • Licenced waste transport
  • PCB freight management (including specialised bunded containers)
  • De-oiling of equipment
  • Decontamination of equipment prior to scrapping
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