By Eric Smith, Ph.D.
Owners of PCB transformers ultimately face the decision whether to "replace" their askarel transformers with new units or "reclassify" them to non-PCB status using the perchlorethylene process. Until now, owners of PCB transformers particularly those in inaccessible locations, had virtually no alternatives to the perchlorethylene method.
PCB Transformer Reclassification
As most people know by now, reclassification of a PCB transformer occurs when the PCB concentration in the transformer's dielectric is reduced to less than 50 ppm, a formidable task considering the initial PCB levels of askarel transformers are typically 300,000 to 700,000 ppm. It should be re-emphasized that various provincial environment ministries may have specific criteria for re-confirming the "status" of a transformer (PCB analysis of core, coils, tank, fins, etc.) when the unit is removed from service, sold, or scrapped.
The process of reclassifying an askarel transformer to non-PCB status involves 5 basic steps:
1) draining the askarel from the transformer;
2) re-gasketing the transformer
3) retrofilling the unit with perchlorethylene
4) installing an external distillation apparatus next to the transformer until PCB levels are < 50 ppm
5) re-gasketing the unit and retrofilling it with a suitable dielectric.
Replacement of the askarel with perchlorethylene as the dielectric to gradually leaches the PCBs from the porous components of the transformer core. As the PCBs leach from the core, they are removed from the perchlorethylene as the liquid continuously circulates from the transformer through the external distillation apparatus and back through the transformer. The PCBs are collected for disposal and the process is allowed to continue until the PCB levels in the perchlorethylene drop to less than 50 ppm; a process that has been shown to take up to 4 years to complete.
Factors Affecting Decision Making
Sseveral factors that are taken into account when trying to decide whether to replace or reclassify an askarel transformer:
1) the life expectancy of the transformer
2) the accessibility of the unit and the logistics of extraction and installation
3) the time frame for reclassification
4) the choice of dry-type versus liquid insulated units
5) costs comparisons
6) the need to up-grade to a larger KVA rating, and so on.
The Insurance Issue
Despite all of the other factors that are considered, under current market conditions, the primary impetus for deciding to replace askarel transformers is "insurance" related. Owners of PCB transformers are finding that their insurance policies will not cover them for environmental contamination created from spills or fires involving PCBs.
More importantly, the standard insurance policies for buildings and similar structures would also not cover cleanup costs associated with spills or fires involving perchlorethylene, the replacement fluid used in reclassifying askarel transformers. This potential ìexposureî is simply not acceptable to most PCB transformer owners.
Concerns About Perchlorethylene
Insurance companies and PCB generators have several concerns about using a chlorinated hydrocarbon such as perchlorethylene as a dielectric:
1) like polychlorinated biphenyls, the chlorinated hydrocarbon perchlorethylene would also produce toxic by-products in a transformer vault fire;
2) unlike PCBs, perchlorethylene is acutely toxic and a spill in a substation could potentially cause serious health problems or even death of exposed workers;
3) like PCBs, perchlorethylene would not be readily biodegraded if it was to find its way into terrestrial or aquatic environments;
4) unlike PCBs, cleaning up a perchlorethylene spill in a transformer substation would necessitate the use of a self-contained breathing apparatus for all exposed workers;
5) like PCBs and other organo-chlorine compounds such as DDT, perchlorethylene would undergo bio-accumulation and bio-magnification in the food chain;
Some of these concerns about perchlorethylene, which is the solvent used in the dry-cleaning industry, has tempted regulatory authorities to consider banning its use altogether. It still remains to be seen whether this will happen or not.
Logistical Concerns
In addition to the potential health and environmental concerns, there are various other contributing factors to consider regarding transformer reclassification using perchlorethylene. For example:
1) the perchlorethylene must remain in a transformer until the PCB level drops and remains below 50 ppm, so the potential risks associated with this solvent would be extended for several years.
2) the perchlorethylene is kept in a transformer as the dielectric fluid even after the PCBs are reduced to below 50 ppm and the external distillation unit has been removed; this is to facilitate re-connection of the distillation unit where PCB levels increase to greater than 50 ppm as the transformer core continues to leach PCBs over time.
3) following reclassification, if silicone is used as a replacement fluid and the PCBs leach from the core to levels > 50 ppm, PCB-contaminated silicone will have to be dealt with and the draining and retrofilling with new silicone and subsequent disposal of the PCB-contaminated silicone is very expensive and time-consuming.
Until now, these have been some of the problems that have prevented PCB owners from tackling their askarel transformers.
Accessibility of Transformers
To date one of the major reasons for deciding to use the reclassification process was the fact that transformers were considered to be inaccessible. When high-rise office buildings were constructed, the structures were built around askarel transformer substations where transformers were lifted into place by cranes sometimes 30 or more stories off the ground. Prior to construction, no thought was given to ever having to replace the transformers since PCBs were not an issue at the time.
Consequently, there are several situations where askarel transformers are so far off the ground as to be inaccessible by ground level cranes or there would be so many problems with removing walls and/or floors, that it would be totally unfeasible or the associated costs would be prohibitive.
Even if the substation wall was removed, attempting to extricate an askarel transformer from a high-rise office tower using a roof-mounted crane to ìswingí the unit out and away from the building would not be considered a very desirable option for the PCB owners, the regulatory officials or the insurance companies.
No Transformers are Inaccessible
In response to these various challenging issues, PCB Disposal has developed an approach to askarel transformer replacement which will:
1) immediately eliminate the liability associated with PCBs and perchlorethylene;
2) allow transformers to be removed from any location, regardless of where the transformers are situated;
3) completely eliminate the concern about spills or leaks of liquid insulated transformers.
In cooperation with the transformer manufacturer, PCB Disposal can now offer a turn-key process for askarel transformer replacement which involves replacing askarel transformers with dry-type transformers. Particularly in those instances where transformers are virtually inaccessible, askarel transformers are drained, disassembled and removed in pieces and the new replacement transformers are brought to the site in pieces and assembled in the substation.
PCB Disposal has received approval from the Ontario Ministry of Environment and Energy (MOEE) to remove and disassemble askarel cores and decontaminate and cut transformer tanks to allow for extraction of the units from any substation location despite site constraints such as size, weight and height restrictions i>