PCBs AND ASSOCIATED AROMATICS 907
been completed then, according to the letter of the law, the
unit can be reclassified as “PCB contaminated”. However,
experimental data on units which have been retrofilled with
a simple vapor cleaning process have shown that the PCB
leaching rate under normal load conditions is in the range
of 1.5–2.5 ppm PCB per day. If the trapped PCBs are able
to leach out into the bulk retrofill fluid at a rate of as little as
1 ppm PCB per day, it would need approximately one year
before the fluid concentration had climbed above 500 ppm
PCB and the unit would have to be regarded once again as
a PCB transformer.
The following cost elements enter the business alterna-
tives of replace vs. retrofill:Replacement- Basic cost of transformer and dielectric coolant.
- Miscellaneous fittings: stress cones, etc.
- Possible rental of mobile substation during
changeover. - Crane rental.
- Labor (probably at overtime rates).
- PCB packaging, transport and disposal.
- Purchase cost of flushing solvent to prepare trans-
former carcass for landfill disposal. - Packaging, transport and disposal of flushing
solvent. - Transport to and disposal in EPA-approved land-
fill for transformer carcass.
Retrofill- An initial, fundamental decision must be made
concerning whether to change the classification
of the transformer to “PCB contaminated” i.e.,
500 ppm PCB, or to 50 ppm PCB to remove
the unit from TSCA purview.- Dielectric fluid costs.
- Solvent flushing fluid, depending upon the retro-
fill method. - Transport of oil, solvent and materials to and from
the site. - Gaskets, parts, hosing, fittings etc.
- PCB disposal, solvent disposal.
- Downtime 4 h to 48 h, depending upon the level of
decontamination required and the process used. - Repeated electrical outages, depending upon the
retrofill process chosen. - PCB-in-oil analyses, dielectric fluid properties
report.
The following cost comparison compares the options of retro-
fill or replacement of askarel filled transformers. The compar-
ison is complicated by the many variables which are involved
and therefore a range of costs has been considered as they
apply to two different sizes of PCB filled transformers.
EPA has completed an analysis of the costs of retrofilling
PCB transformers to reduce the PCB concentration to below
500 ppm PCB and has estimated that the cost will vary in the
range from $15,500 for a 50 KVA transformer to $32,000
for a 3,000 KVA transformer. The example above is for an
“average” or “typical” size transformer or about 225 gal. oil
capacity and shows that the cost savings over replacement
will be about $20,000 per unit. Clearly, the larger and more
inaccessible a transformer the more cost effective retrofilling
becomes (Table 40).
Despite the extensive work which has been done over
the last few years on the validation of different fire hazard
assessment methods for askarel replacement fluids there is
still no consensus of opinion. Experience derived from theTABLE 40
Transformer descriptionTransformer 1 Transformer 2kVA 500 1500
Location Indoors Indoors
Primary Voltage (110 kV BIL) 12470 13800Y/7970
Secondary Voltage 480Y/227 480Y/277
°C Rise 65°C 55/65°C
Oil Cooled OA OA
Winding Temperature Yes No
Indicator
HV Connection Throat Throat
LV Connection Throat Throat
Pressure Relief Device Cover mounted Cover mounted
Sudden Pressure Relay Cover mounted Cover mounted
Taps 2 21/2% 2 21/2%
Dimensions 4 6 6 5 7 7
# of Gallons Oil 190 225
(continued)C016_003_r03.indd 907C016_003_r03.indd 907 11/18/2005 1:12:39 PM11/18/2005 1:12:39 PM