EPA 560/6-77-008
ASSESSMENT OF THE USE OF SEL£C1
REPLACESW FLUIDS FOR PCBS
IN ElfCTRICAL
March 1979
U. S. Environmental Protection Agency
Office of Toxic Substances
Washington, D. C. 20460
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.This document is available in limited quantities through the U.S.
Environmental Protection Agency, Industry Assistance Office, Office of
Toxic Substances (TS-793), 401 M Street, S.W., Washington, D.C. 20460.
This document will subsequently be available through the National
Technical Information Service, Springfield, Virginia, 22151.
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EPA 560/6-77-008
ASSESSMENT OF THE USE OF SELECTED REPIACEMENT
FLUIDS FOR PCBS IN ELECTRICAL EQUIPMENT
FINAL TASK REPORT
Sutmitted to:
U. S. Environmental Protection Agency
Office of Toxic Substances
Washington, D. C. 20460
Attention: Mr. Thonas Fbpp
Project Officer
Contract No. 68-01-3259, Task VII
Submitted by:
VERSAR, INC.
6621 Electronic Drive
Springfield, Virginia 22151
(703) 750-3000
March 1,.1979
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This report has been reviewed by the Office of Planning and
Management, U.S. Environmental Protection Agency, and approved for
publication. Approval does not necessarily signify that the contents
reflect the views and policies of the Environmental Protection Agency, nor
does mention of trade names or comiercial products constitute endorsement
or recommendation for use.
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PREFACE
This report on the substitutes for PCBs in electrical equipment is one of
a series of reports that have been prepared by Versar for the Environmental
Protection Agency under contract 68-01-3259. All of this work has been in
support of regulatory activities involving PCBs. Mr. Thomas E. Kbpp of the
Office of Toxic Substances, has been the EPA Program Manager throughout the
performance of this contract.
The electrical equipment manufacturing industry was faced with a serious
problem when the use of PCBs was banned by the Toxic Substances Control Act.
PCBs had unique properties when used as fire resistant dielectric liquids in
transformers and capacitors, and had-been almost the only liquid used in these
electric applications over the past 45 years. The equipment manufacturers were
faced with the challenge of redesigning their products to achieve adequate per-
formance and fire safety from substitute liquids which did not equal PCBs in
either property.
This report has been under preparation for over two years, and has been
constantly updated as the technology of replacement liquids has evolved. Por-
tions of the material that was prepared for this report were used by Versar in
support of the PCB Work Group that prepared the'regulations, and Versar's
analyses of the economic impacts of the regulations also relied heavily on the
material in this report. The report is being published now as a summary of the
developments in the electrical equipment industry at the time that the EPA is
promulgating the final PCB Ban Regulations.
Special thanks are due to Mr. Kopp for his patient support during the
performance of this contract over the past three years. Thanks are also due the
many technical experts in the electrical equipment industry who discussed their
problems and developing solutions with Versar and so made this report possible.
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TABLE OF CONTENTS
PREFACE
1.0 INTRODUCTICN 1
2.0 TRANSFORMERS 6
2.1 The Use and Operation of Transformers 6
2.2 Heat Generation in Transformers 10
2.3 Desired Properties for Transformer Heat Transfer Fluids . . 10
2.4 Use of PCBs in Electrical Transformers 11
2.5 Alternatives to the Use of PCBs in New Transformers .... 17
2.5.1 Non-PCB Askarels . 18
2.5.2 High Fire Point Transformer Liquids 22
2.5.3 Oil Insulated Transformers 23
2.5.4 Air Insulated Dry Type Transformers 32
2.5.5 Gas-filled Sealed Transformers . . . 36
2.6 Relative Costs of Substitutes for Askarel Transformers . . 37
2.7 Effect of the PCBs Ban on New Transformer Installations . . 38
2.8 Maintenance of PCB Transformers 41
2.8.1 Make-Up Liquids for Askarel Transformers 41
2.8.2 Retrofilling Askarel Transformers 44
2.8.3 Renoval of Residual PCBs frcra Non-Askarel Trans-
former Liquids 49
3.0 ELECTROMAGNETS 53
4.0 ELECTRIC MOTORS 55
4.1 The Use of Liquid-Cooled Motors in Mining Machinery .... 55
4.2 Substitutes for PCBs in Electric Motors 58
5.0 CAPACITORS 61
5.1 Principles of Capacitor Operation 61
5.2 Uses of Electrical Capacitors in Alternating Current
Circuits 65
5.2.1 High Voltage Power Factor Capacitors 66
5.2.2 Industrial Capacitors 67
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TABLE OF CONTENTS (Continued)
5.3 Desired Properties for Capacitor Dielectric Liquids .... 70
5.4 Use of PCBs in Capacitors ' 74
5.4.1 Power Factor Capacitors 75
5.4.2 Other Snail and Low Voltage Capacitors 75
5.5 Alternatives to PCS Capacitors 76
5.5.1 Synchronous Condensers 77
5.5.2 Dry film capacitors 78
5.5.3 Conventional Capacitors Using Non-PCB Liquid
Dielectrics 80
5.5.3.1 Alkyl Phthalates 83
5.5.3.2 Isopropylbiphenyl 86
5.5.3.3 Butylated Monochloro Diphenyl Ether .... 87
5.5.3.4 1,1-Pnenyl Xylylethane 89
5.5.3.5 Other Capacitor Dielectric Liquids .... 90
6.0 CONCLUSIONS 94
iii
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LIST OF TABLES
i
Table Kb.
2.4-1 Major Trade Namest and Producers of...Transformer. Askarel . . 13
2.5-1 Installation Reqoiranents for Electrical Transformers . . 19
2.5.2.-1 High Fire Point Transformer Liquids 24
2.6-1 Cost Comparisons of Oil Filled Versus Other Transformer
Designs Intended for Hazardous Locations 39
5.4.1 Non-PCB Power Factor Correction Capacitors 75
5.5.3-1 Properties of Capacitor Dielectric Liquids 81
5.5.3.5-1 Properties of Potential Capacitor Dielectric Liquids ... 92
iv
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1.0 INTRODUCTION
Polychlorinated biphenyls (PCBs) are a family of chlorinated organic
chemicals that have been used in various industrial applications in the
United States since 1929. PCBs have been used in numerous applications
because of their chemical stability/ low vapor pressure, lew water solu-
bility, and moderate price. These characteristics, combined with special
electrical properties, led to the nearly universal use of PCBs as dielectric
liquids in A.C. lighting, ballast capacitors, industrial capacitors, and
power factor capacitors. PCBs have also been widely used as fire-resistant,
heat transfer electrical insulating liquids in those liquid-cooled trans-
formers, electromagnets, and electric motors-that were installed in hazard-
ous locations. PCBs were widely used in non-electrical applications such as
heat transfer and hydraulic fluids, dye carriers in carbonless copy paper,
and as plasticizers. It has been estimated that about 75 percent of the
1,250 million pounds of PCBs used in the United States was used in electrical
equipment.
The major manufacturer of PCBs in the United States was Monsanto Chemi-
cal Company,.which marketed various mixtures of PCBs under the trade name
"Arcclor" - 1200 series. The PCBs were made by reacting biphenyl with chlorine
in the presence of ferric chloride, resulting in the substitution of chlorine
for hydrogen on the biphenyl molecule. The average degree of chlorination
depended on the time that the reaction was allowed to continue. After further
processing to remove residual EC1 and byproducts, the mixture of various
chlorinated species was described by the average weight percent of chlorine
in the mixture, i.e., Aroclor 1242 contained 42 percent chlorine by weight.
The reaction can be described by the following equation:
(I) Versar, Inc., FCBs in the United Statest Industrial Use and Environ-
mental Distribution. Springfield, Va.: National Technical Information
Service (OTIS PB 252-012/3WP), February, 1976.
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HHHH
HHHH
BIPHENYL(C12H1()) . X-dorH
This reaction can theoretically result in any of 209 different chlori-
nated biphenyls/ depending on which hydrogen atoms are replaced by chlorine
and the number of hydrogen atoms replaced. Most commercial Aroclors con-
tained only 30 to 40 different species of PCS in significant amounts.
Monsanto marketed mixtures containing from 21 percent chlorine to 68 percent
.chlorine for various electrical and non-electrical uses.
Prior to 1968, PCBs were recommended for a great number of uses because
of their chemical stability and the wide range of viscosities that could be
obtained as a function of average chlorine content. Little thought was given
to the eventual fate of the PCBs, and the only health effects publicized were
related to chloracne caused by skin contact. In 1969 and 1S70, a number of
events occurred that demonstrated the chronic toxicity of PCBs and their
presence in the environment at significant levels. In 1968, an industrial
accident in Japan caused the contamination of cooking oil with FCBs. Distri-
bution and use of this oil resulted in 1037 reported poisoning cases. In
1969, analytical procedures were developed that allowed PCBs to be identified
in concentrations of parts per million in environmental samples. In 1970,
PCBs were identified as the contaminant in Coho salmon from Lake Michigan.
The reproduction rate of commercial mink had been affected when they were fed
contaminated salmon. The mink reproductive problems had first been reported
in 1965; identification of PCBs as the cause awaited development of satis-
factory analytical procedures.
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In 1971 / Monsanto voluntarily discontinued the sale of PCBs for all uses
except totally enclosed electrical systems. In 1972, the U.S. Food and Drug
Administration (FDA) established temporary tolerances for PCBs in food, and
FDA surveillance resulted in the rejection of numerous lots of fish and
occasional lots of chicken and eggs. By 1975, evidence of the presence of
PCBs in industrial effluents and in the environment had been accumulated,
and reports of PCB contamination were featured in the non-technical press.
On March 26, 1976, Senator Gaylord Nelson of Wisconsin introduced into the
Senate an amendment to the Toxic Substances Control Act (TSCA) which re-
quired the eventual elimination of the use of PCBs in the United States.
This amendment was the basis of Section 6 (e) of TSCA, and the eventual
ban on the manufacture of PCBs became a legislated requirement on October
11, 1976, when TSCA. was signed into law.
At the same time they were considering the PCB amendment to TSCA, the EPA
proposed toxic pollutant effluent standards for PCBs under Section 307 (a) of
the Federal Water Pollution Control Act. The proposed regulation was pub-
lished in the Federal Register on July 23, 1976; it proposed banning PCB
discharges by any PCB manufacturer. It placed severe limitations on PCB
discharges by capacitor and transformer manufacturers. Following extensive
hearings, the PCB effluent standard was promulgated on February 2, 1977.
The regulation required the elimination of discharges of PCBs by PCB
manufacturers, transformer manufacturers, and capacitor manufacturers using
PCBs by February 2, 1978. A one year compliance deadline for manufacturers
of electrical equipment was allowed to enable plants to phase out the use of
PCBs, convert to substitutes, make appropriate.technological or process
changes, or take such other steps as are necessary to achieve compliance.
Regulatory Implementation of the various requirements of Section 6 (e) of
TSCA. has occurred in several steps. EPA proposed regulations on the marking
and disposal of PCBs on May 24, 1977. These regulations were promulgated
on February 17, 1978. They establish labeling and disposal requirements for
PCB material and equipment and require EPA approval of incinerators and land-
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fills used for the disposal of PCBs. Additional regulations banning the
manufacturing, processing, distribution in commerce, and use of PCBs were
proposed by EPA on June 7, 1978. An analysis of the economic impacts of
this proposed regulation was presented in a separate contractor's report
(2\
published by the EPA.v '
The action to ban the continued use of PCBs in the United States was
not completely unexpected. PCBs were banned in Japan in 1972, and adequate
substitutes were developed within a year or two. In 1972, Monsanto intro-
duced a new PCB mixture, Aroclor 1016, which contained about 40 percent by
weight chlorine and was marketed as a "more biodegradable PCB" for capacitors.
General Electric Company, among other capacitor manufacturers, had been
testing dielectric liquids for several years and announced the limited availa-
bility of non-PCB fluorescent light ballast capacitors late in 1976. The
Dow Chemical Company developed a substitute for PCBs in large capacitors;
the availability of capacitors using this dielectric fluid was announced late
in 1976 by the McGraw Edison Company. By late 1977, all manufacturers of
large power factor capacitors had discontinued the use of PCBs, and by late
1978, all small capacitors were being manufactured without PCBs.
PCBs have never been used in more than about five percent of all liquid-
filled transformers, and substitute liquids having higher fire points than
regular transformer oil were under test as early as 1974. Silicone dielectric
fluid has been used for the same purposes as PCBs in both electromagnets and
liquid-filled electric motors since the early 1970s. Bailroad locomotives
had been built in Japan using silicone liquid-cooled transformers in 1973
and were reported to operate satisfactorily.
Although a number of substitutes for PCBs have been developed during the
past 5-10 years, sufficient time has not elapsed for experience to prove
which, if any, of the materials will be satisfactory in each application. It
(2) Versar, Inc., Microeconomic Impacts of the Proposed PCB Ban Regula-
tions, Springfield, Va.: National Technical Information Service
(Beport No. NTIS PB-281-881/3WP), May, 1978.
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is the purpose of the following sections to discuss the performance require-
ments for substitutes for PCBs and to evaluate the degree to which presently
available materials meet these requirements. Because there are no materials
available that are exact replacements for PCBs, alternative technologies for
performing the functions previously filled by PCB equipment are also dis-
cussed.
No attempt has been made in this study to exhaustively investigate sub-
stitutes for PCBs. Much work is being done and is planned to meet the
requirements mandated by the banning of PCBs. This work is reviewed where
relevant. Thus, the following sections should be considered an in-depth
status report rather than a comprehensive monograph.
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2.0 TRANSFORMERS
Polychlorinated biphenyls have been used as liquid coolants in elec-
trical transformers located where fires might endanger human life and
property. PCBs have the advantage of nonflanznability in contrast to mineral
oil, the other major liquid coolant used in transformers. Gaseous coolants
are also nonflammable, but gas-cooled transformers have certain disadvantages
when compared to liquid-cooled transformers. Dry type transformers are
generally more expensive than the liquid-cooled units, and they usually have
increased operating noise levels and a lower capacity of withstand temporary
overheating caused by surges of power in the electrical circuit. Alternative
liquid coolants are available but none have the fire resistance of PCBs.
The following discussion includes a summary of the purposes of transformers
in electrical circuits, heat generation in transformers, ideal heat transfer
.fluids for transformers, and the present status of substitutes for PCBs as
transformer coolants.
2.1 The Use and Operation of Transformers
A transformer consists of two coils of wire connected magnetically
by an iron core as shown schematically belcw. An alternating current applied
to one winding (the primary winding) creates an alternating magnetic field
in the iron core. This alternating magnetic field induces an electric current
in the other, or secondary, winding. In a simple transformer, the ratio of
voltages in the primary and secondary windings is equal to the ratio of turns
in the windings, or
Vi _ NI CORE
vT " NT • "~
N2TURNS
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There are two types of transformers used in the electrical power
industry: power transformers, used generally for "stepping up" voltage
(e.g./ at the power plant) and distribution transformers, used to "step
down" voltages at or near, the site of power use. The distinction between
power and distribution transfonrers is actually not well defined. As will
be seen below, some transformers used for voltage step-up are classed as
distribution transformers and vice versa. However/ whether a transformer
is used for voltage step-up or step-down, the operating principle is the
same: step-up transformers have a greater number of turns on the secondary
winding, and step-down transfonrers have a greater number of turns on the
primary winding. In theory, a step-up transformer can be converted to a
step-down transformer by simply reversing the position of the transformer
in the circuit.
A typical power plant generates about 1,000 megawatts, or a mil-
lion kilowatts, which would be enough power to light 10 million 100-watt
bulbs -if none of the power generated at the power plant were lost in the
transmission wires carrying the power to the bulks. Since the wires carry-
ing electricity fron a power plant to the electrical loads in homes and
factories offer resistance to the flow of electricity, a certain amount of
energy must be expended to get the electrical power from the power plant to
the home or factory. This lost energy — or power, since it is lost at some
rate per unit of time — is radiated in the form, of heat from the transmis-
sion wires. Transformers are used as one method of minimizing these trans-
mission losses. The less the wires heat up/ the less the amount of energy
lost in the wires during the transmission of power.
The energy losses in a power transmission line (or simply, power-
line) running from a power plant to a community of homes and factories are/
as with the purely resistive loads/ a product of the voltage difference
between the ends of the powerlines (one end being at the power plant and
the other being at the site of power use) and the amount of'current being
pushed through the powerline. However/ the losses in a powerline can also
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be written as the product of the electrical resistance of the power line
(measured in ohms) and the square of the current being carried in the lines
so that
P = i2R
where P is the power lost in the wire, i is the current, and R is the re-
sistance of the wire.
Since the resistance of the wire can be minimized only by increas-
ing the diameter of the wire (which is expensive because the wires are made
of costly metals such as copper or aluminum), the best way to minimize
power losses in the transmission wire is to minimize the current. In order
. to transmit power from, the power plant to a community at a lower current,
the voltage must be increased by the same factor by which the current is
decreased. For example, if a 1,000-megawatt power plant transmitted its
power at 120 volts, the current in the transmission wires would be more .
than 8 million amperes. If the transmission voltage were 120,000 volts, the
current would be only about 8 thousand amperes. Since losses in the trans-
mission wire are proportional to the square of the current, in the first case
losses would be proportional to 8 minion squared, or 64 trillion; the
losses in the second case would be proportional to 8 thousand squared, or
64 million. The resistive power loss at the higher transmission voltage
would be a million times less than if the power were transmitted at 120
volts.
The function of transformers used in power distribution is to
transfoxm electrical power from, low^-voltage and high-current characteristics
to high-voltage and low-current characteristics, and then to transform it
back to the relatively low voltage commonly used in hones. However, because
transformers contain a great deal of current-carrying wire, a certain anount
of electrical energy is lost in transformers. This energy loss manifests
itself as heat. If the heat is not removed, the temperature of the trans-
former's electrical insulation might burn out, or the wire windings could
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short circuit and even melt. Therefore, electrical transformers must be
kept cool so that they can operate reliably for long periods of time. They
must also be kept cool because they operate more efficiently, i.e., with
less energy loss, at lower temperatures.
Small transformers of the type found in radios and television
sets are cooled by the thermal conduction of excess heat into the air around
the transformer. When the air is warmed, it rises so that new, cool air
is continuously brought into contact with the transformer. This is the
reason for ventilation holes in television sets and radios; the holes allow
' the free flow of cooling air. In larger transformers used to step up the
voltage at the power plant, or to step down the voltage near the sits of
use, use of air to cool the outer surface of the transformers may not remove
heat rapidly enough from the middle of the transformer. There are many
large air-cooled transformers in service, but they have certain disadvantages
which are discussed below. Liquid-cooled transformers are the most common
types; most are cooled with mineral oil, which is inexpensive but is
flammable and can catch fire if the transformer undergoes an internal short
circuit.
It is important to place the distribution (step-down) trans-
former as closely as possible to the point where the power is used to
minimize transmission losses. Therefore/ these transformers are often
located in buildings or on. the roofs of buildings where fires would consti-
tute serious risks. For large .transformers used in locations where trans-
former fires might endanger people, polychlorinated biphenyl formulations
have been used as the cooling liquid because of their combination of fire
resistance, low cost, and electrical properties.
Other cannon applications of PCB-filled transformers include:
Distribution transformers in electric generating stations
to supply power to pumps and conveyors.
Step-up transformers used to generate high voltage electricity
for electrostatic predpitators on tall stacks.
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Railroad locomotive and transit car transformers where the
power to the train is supplied as high voltage electricity
from an overhead catenary.
2.2 Heat Generation in Transformers
Since the wires that carry electrical power froti the site of
generation (be it a battery or an electrical generator) to an electrical
load also offer resistance to the flow of electrical current, a portion of
the power generated is lost through heating of the wires connecting the load
to the electrical power source. For a given wire diameter, electrical re-
sistance is proportional to the length of the wire. In many circuits (e.g.,
an automobile electrical system), tie power lost in the transmitting wires
is i-mall in comparison to the power delivered at the load (such as the head-
lights) . However, in transmitting electrical power over long distances, the
resistance of the wires could cause the dissipation of a significant portion
of the energy intended for the load.
The wire in the transformer winding offers resistance to the flow
of electricity and results in the production of heat in the windings. Since
the electrical resistance of most conducting materials increases with
temperature, the efficiency of the transformer (i.e., the ratio of the out-
put power to t2ie input power) is greatest when tiie transformer is kept at
a lew operating temperature.
Hie generation of an alternating magnetic field in the core
material is never completely reversible. Not all of the energy stored in
the magnetic field is recovered as electric power when the direction of the
field is reversed; the lost power appears as heat. The magnetic field can
induce electric currents in the core material as well as in the wind-
ings; these eddy currents are also dissipated as heat. Only the resistive
losses are proportional to the load on the transformer. The total heat
generated is typically 0.3 to 0.6 percent of the power passing through the
transformer. Therefore, all transformers used in the electrical industry
have provision for cooling with either gaseous or liquid coolants.
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2.3 Desired Properties' for Transformer Heat Transfer Fluids
.. The purpose of the heat transfer fluid in a transformer is to
absorb the heat produced in the windings and core, to transfer the heat to
cooling fins, and to provide electrical insulation within the transformer.
The ideal fluid should, have the following properties:
Thermal.;
a. High heat capacity - able to absorb heat generated in the
transformer during overload conditions with minimum in-
creases in temperature.
b. Low viscosity - able-to increase convective heat transfer
and/or reduce pumping costs.
c. High coefficient of thermal expansion - able to provide
good thermal siphoning action.
d. High thermal conductivity - able to maximize conductive
heat transfer.
e. Low freezing point - able to withstand very cold tempera-
tures (freezing could distort the coils and damage the trans-
former) ..
f. High boiling point - able to withstand at least maximum
expected temperature. (A boiling point below that would
require the use of a pressure vessel to prevent boiling and
loss of fluid.)
Chemical:
a. Chemical stability when exposed to high temperatures and
intense electric field for long periods of tire in the
presence of copper and other potential catalysts.
b. Nbn-flanroability in the event of a spill.
c. Non-flammable degradation products in the event an electri-
cal arc occurs inside the transformer.
d. Non-corrosive degradation products formed by arcing.
e. Low solvency toward other mat-ta-n *1« of construction.
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Electrical;
a. High dielectric strength - the liquid acts as an electrical
insulator filling any cracks that develop in solid insula-
tion.
b. High resistance to corona formation.
c. Low loss tangent to minimize dielectric heating of the liquid.
d. Minimal degradation of electrical properties if contaminated
with moisture.
Toxicity;
a. Non-toxic - both acute and chronic.
b. Biodegradable.
c. Non-toxic degradation products - from biodegradation, arcing,
and fires.
Cost: Low Cost.
Availability; Multiple sources with standard and reliable
properties.
2.4 Use of PCBs in Electrical Transformers
The most commonly used non-flammable transformer coolant liquids
have been mixtures of PCBs known as askarels. Askarel is defined by the
National Electrical Code as "a generic term for a group of non-flammable
synthetic chlorinated hydrocarbons used as electrical insulating media.
Askarels of various compositional types are used. Under arcing conditions
the gases produced, while consisting predominantly of non-combustible
hydrogen chloride/ can include varying amounts of combustible gases depend-
ing on the askarel type."
The most commonly used askarel compositions are Inerteen (Westing-
house trade name for 70 percent PCB mixture prior to 1968, 100% Aroclor 1242
since 1368)' and Pyranol (General Electric trade name for 70 percent mixture).
The exact composition of both Pyranol and Inerteen have been changed from time
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TABIE 2.4-1
MAJOR TRADE NAMES AND PRODUCERS OF TRANSFORMER ASKAREL
TRADE NAME MANUFACTURER
Asbestol American Corporation
Chlorextol . Al lis-Chatoers
Inerteen * Wsstinghouse Electric
No-Flarool Wagner Electric
Pyranol General Electric
Saf-T-Kuhl Kuhlman Electric
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to time. Table 2.4-1 lists trade names and producers of various askarel
formulations. Prior to the mid-1950 's, the insulating liquid used in many
transformers (General Electric formulation) was a 50-50 mixture of Aroclor
1260 (60 percent chlorine) and tri-chlorobenzene. In the late 1950 's/ the
chloro-benzene component was changed to a mixture of tri- and tetrachloro-
benzenes. In September 1971, at Monsanto 's suggestion/ the Aroclor com-
ponent was changed to Aroclor 1254 (54 percent chlorine) . The most recent
Westinghouse formulation (Inerteen) used Aroclor 1242 (42 percent
chlorine).
The volume of askarel used in transformers ranges from 3 to 3,400
gallons (33 to 38,000 -Ibs) , with an average of about 230 to 320 gallons
(2,500 to 3,500 Ibs). About 135,000 to 140,000 transformers using PCBs
have been put into service since 1932. These units represent about 15
percent of all large transformers in service. Virtually all askarel
transformers are still in service. The production rate of askarel trans-
formers until recently was about 5,000 units per year, requiring some
10 to 15 million Ibs of PCBs. (1)
One manufacturer of askarel transformers classified its pro-
duction in this manner:
- Power transformers;
a. Railroad transformers used on board electric locomotives
or multiple unit electric railroad cars. (Receive up to
25,000 volts and contain 700 to 2,400 Ibs of askarel in
each unit depending on the rating and size of the transfor-
mers.)
b. Furnace transformers used in proximity to glass melting and
induction furnaces, which require high-current, low-voltage
power supplies. (Receive up to 15,000 volts and contain
2,000 to 4,000 Ibs of askarel.)
c. P^Ttifi^f transformers used for large rolling mills and DC
industrial power supplies. (Receive up to 15,000 volts AC
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and deliver low-voltage high-amperage B.C. Each unit con-
tains about 19,000 Ibs of askarel.)
d. Shunt reactors, which provide reactance. (Receive up to
15,000 volts under normal operating conditions and deliver
voltage and current as received.) The purpose of shunt
reactors is to suppress voltage rise at light loads, control
output voltage, and generally to act as an electric governor.
e. Grounding transformers. (Receive up to 15,000 volts.)
Distribution Transformers;
a. Secondary unit substation (Receive up to 15,000 volts and
deliver less than 1000 volts.)
b. Pad-mounted (Receive up to 14,400 volts and deliver 120, 240,
and 480 volts.)
c. Pole-mounted (Receive up to 14,400 volts and deliver 120, 240,
and 480 volts.)
d. Precipitator power supply (Receive 480 A.C. volts and deliver
56-60 kilovolts low-amperage D.C.)
Quantities of askarel used in these distribution transformers are
usually in the range of 3 to 400 gallons in each unit depending on the rating
and the size of the unit.
The service life of an askarel transformer is expected to be greater
than 30 years. The failure rate for transformers presently in service is
about 0.2 percent per year. Only 1 percent of these failures actually results
in rupture of the transformer casing, so the total uncontrolled loss is prob-
ably less than 8000 Ibs out of about 420 million Ibs of askarel in transformer
use.
Obsolescence of existing transformers is 1 to 2 percent per year.
Obsolete transformers are moved to new locations or sold on the used equipment
market, or the askarel may be reclaimed and sold for transformer maintenance.
T.irpi-M coolants in transformers have better heat transfer and heat
capacity characteristics than gaseous coolants. PCBs have the additional advan-
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tage of being non-flamtiable. The other advantages of PCBs are their high
dielectric strength, outstanding chemical stability, relatively low vis-
cosity/ and low freezing point. The chemical stability of PCBs assures
reliable transformer performance without frequent maintenance. On the other
hand, oil-filled transformers require a great deal of maintenance. Naphthenic
base mineral oil gradually decomposes resulting in the formation of sludge,
which interferes with transformer heat transfer. The decomposition also
degrades the electrical properties of the mineral oil. This reaction is
accelerated if the oil is exposed to air. Therefore, it is common practice
to test the. properties of oil in oil transformers every year or two and to
treat or replace the oil if it has degraded. PCBs are also subject to
degradation of electrical properties" if minor arcing occurs in the trans-
former or if moisture is absorbed from air leaking through faulty busings
or gaskets. However, the rate of degradation of PCB is usually less than
that of transformer oil, and routine testing of PCB transformers is conducted
less frequently than for oil-filled units.
Disadvantages to PCBs, in addition to the environmental threat,
tcxicity, and pungent smell, were cost (about eight times as much as mineral
oil, on a volume basis) and the highly corrosive HC1 they produce if arcing
occurs in a transformer.
Most askarel-filled distribution transformers are located inside
public, commercial, or industrial buildings or are mounted on the roofs of
such buildings. No special enclosures or vaults are required except as are
necessary to prevent accidental electrical or mechanical contact with the
equipment. However, the National Electrical Code does specify vaults for the
indoor installation of PCB-filled transformers rated at more than 35,000 volts,
Askarel-filled transformers are limited by the dielectric strength of the
liquid to ratings below 69,000 volts.
-16-
-------
ffost power trans formers are situated in remote locations where a fire
or an explosion would not be a threat to property. Mineral oil is usually used
in power transformers installed in these safe locations. However/ some util-
ities use askarel-filled power transformers at generating stations.
Step-up transformers are used to supply high voltage electricity to
electrostatic precipitators. These units are usually mounted on or very near
the small stack. This minimizes the problems associated with the in-plant
distribution of high voltage power. These transformers are usually askarel
filled to minimize fire hazard in the crowded area of the stack and to reduce
the requirement for routine monitoring of oil properties of these rather in-
accessible transformers.
Railroad equipment powered by high voltage A.C. power from over-
head catenaries is used in the U.S. Northeast Corridor. Askarel-filled
transformers are mounted in engines and under self-propelled passenger cars
to reduce the catenary voltage to that required by the traction motors. The
primary use of this equipment is in passenger service on the Northeast AMCRAK
routes and on the commuter lines around Philadelphia and New York. A total
of 1009 askarel-filled transformers are in use in rolling stock including the
old GG-I locomotives, in the Metroliner cars, in various commuter cars and
in the new E-60 locomotives. (Twenty-six E-60 locomotives were built for
AMTRAK by General Electric about three years ago; each locomotive contains
710 gallons of askarel.) Conrail (formerly Perm Central) operating rules
have required the use of askarel transformers in all cars and locomotives
using the tunnels and stations in New York. This fire safety rule was
established after an early GG-I locomotive containing a mineral-oil-filled
transformer caught fire just outside an entrance to a tunnel early in the
1940's.
2.5 Alternatives to the Use of PCBs in New Transformers
The installation of transformers in office buildings, apartment
buildings, and factories is governed by local regulations which are generally
-17-
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based on the provisions of the National Electrical Code (NEC). The NEC is
incorporated by reference into OSHA regulations and therefore applies to
all workplace transformer installations except in electric utilities, rail-
roads, and mines.
Prior to the publication of the 1978 NEC, the only types of trans-
formers recognized by the code were askarel transformers, dry type transfor-
mers, and oil-insulated transformers. Installation requirements were specified
for each type depending on whether the transformer was located inside or
outside a building. The 1978 NEC defines a new type of transformer, "high
fire point liquid insulated transformers," for use as an alternative to
askarel transformers. Installation requirements for these transformers are
summarized in Table 2.5-1.
The Toxic Substances Control Act (TSCA) of 1976 established an
eventual ban on the manufacture of transformers containing PCBs. In
anticipation of the restrictions on PCBs, all transformer manufacturers
except one ceased production of askarel transformers by mid 1977. The
remaining manufacturer anticipated the cessation of production by the end
of 1977.
The choice among the available types of non-PCB transformers will
depend upon availability, technical suitability, and total installed cost for
each installation. Consideration should also be given to fire safety,
efficiency, toxicity, and environmental acceptability for each type of non-PCB
transformer. The following sections suranarize the advantages and potential
disadvantages of using various substitutes for PCB-filled transformers.
2.5.1 Non-PCB Askarels
In the past, askarels have consisted primarily of complex mixtures
of PCBs diluted with lesser amounts of chlorinated benzenes. There is no
requirement in the definition of askarel for the inclusion of any PCBs in
the mixture. Therefore, it is possible to formulate askarels frccn chlorinated
hydrocarbons without using PCBs.
-18-
-------
Table 2.5-1*
Installation Requirements for Electrical Transformers
Location
Type
Askarel
< 25 KVA, < 35,000 V
> 25 KVA
> 35,000 V
High Fire Point Liquid
< 35,000 V
> 35,000 V
Dry Type
< 112 1/2 KVA, < 600 V
Completely enclosed
< 112 1/2 KVA, < 600 V
Not completely enclosed
> 112 1/2 KVA, < 35,000 V
> 35,000 V
Oil-Insulated
< 600 V, < 10 KVA
< 600 V, < 75 KVA
< 112 1/2 KVA
> 112 1/2 KVA
Indoors
No vent or vault re-
quired
Pressure relief vent
and outside venting
required
Vault required
Catch basin required
Vault required
No requirements
Separated from combustible
material by at least 12"
or by a fire-resistant
heat-insulating barrier
Install in fire-resistant
transformer room (excep-
tions for totally enclosed,
ventilated transformers,
and transformers with 80°C
rise installation)
Vault required
Catch basin required
Catch basin required
4" thick concrete vault
required
Transformer vault
required
Outdoors
No requirements
No requirements
No requirements
No requirements
No requirements
Weather proof
enclosure required
Weather proof
enclosure required
Weather proof
enclosure required
Weather proof
enclosure required
Diked floor and/or
sprinklers required for
roof mounted and other
hazardous locations
*National Fire Protection Association, National Electrical Cede 1978,
Boston, Ma. :1977, Article 450, Section B.
-19-
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There have reportedly been a. number of askarel transformers recently
built in Canada that use as a coolant liquid an eutectic mixture of tri- and
tetra-chlorobenzenes with no PCBs. This mixture results in a non-flammable
liquid that meets the definition of Prodelec (France). This material is
reportedly a mixture of 1,2,3 trichlorofaenzene, 1,2,4 trichlorcbenzene, 1,2,3,4
tetrachlorobenzene, and 10% to 20% terphenyl; it is being marketed in the U.S.
by GE under the trade name Iralec.
Use of straight chlorinated benzenes as a coolant may require
changes in the design of askarel transformers. The most important difference
is in the choice of materials; the straight benzene askarel mixtures have a
greater solvency than askarels based on PCBs, and different insulation, gaskets,
and enamels may be required. The use of paper as a wire insulation would
result in an increase in the size and weight of the transformers. The freez-
ing point of the chlorinated benzene mixture used in Canada is about 9°C, so
the transformers must be shipped in the summer and protected against freezing
after installation. If title liquid were to freeze, it could distort
the coils in the transformer. Significant distortion could cause transformer
failure. Presence of the hydrocarbon material in the Prodelec mixture would
be expected to widen the freezing range and reduce the danger of distorting
the transformer windings.
A change to a mixture of chlorinated benzenes would not result in
any significant supply problems. According to a recent study, the 1973 U.S.
production of 1,2,4 trichlorobenzene was over 28 million pounds and the 1973
production of 1,2,4,5 tetrachlorobenzene was over 18 million pounds.
The use of 1,2,4 trichlorobenzene as a functional fluid (a use category in-
cluding askarel) in 1975 was about 5 million pounds.
(3) West, W.L. and S.A. Ware, (Ebon Research Systems), Investigation of
Selected Environmental Contaminants; Halogenated Benzenes — Draft
Report, Washington, D.C., Office of Toxic Substances, USEPA, March
1977.
-20-
-------
Chlorinated benzenes are extensively used in industry, and consider-
able quantities are entering the environment. Because of their toxicity,
environmental stability, and potential for bioaccuraulation, all of the
chlorinated benzenes have been included on the Interagency Testing Committee's
Priority List of chemical substances recommended for testing under Section 4
of the Toxic Substances Control Act. The chlorinated benzenes are also listed
as toxic pollutants under Section 307 (a) of the Clean Water Act.
Chlorinated benzenes present less of an environmental problem than
PCBs. An evaluation of these materials should compare their health effects,
their environmental distribution, and their environmental fates to those same
characteristics in other available substitutes for PCBs. Chlorinated benzenes
are quite volatile; their use in a transformer located indoors would require
that the transformer be vented outside the building. Such venting would
eliminate high concentrations of vapor inside the building resulting from
arcing within the transformer. Inhalation has been found to be the major
entry path of paradichlorobenzene into the human body. This is probably also
true for tri-chlorcbenzen. A recent study of the presence of chlorinated
compounds in humans found that people in the Tokyo Metropolitan area had three
tiroes as much dichlorobenzene in their blood as PCBs. Concentrations within
fA\
adipose tissue were the same for PCBs and dichlorobenzene. This result is
due both to the greater tendency of PCBs to accumulate in fatty tissue and to
the ability of the body to metabolize and excrete chlorinated benzene. Even
tetrachlorobenzene is slowly metabolized and excreted. A test with rabbits
indicated that only 10% remained in the body after six days. It was deter-
mined that 43% of the ingested tetrachlorobenzene was converted to 2,3,4,5-
tetrachlorophenol prior to excretion and that the remainder was excreted
intact. The metabolism of tetrachlorofaenzene is accompanied by significant
changes in liver function at exposures considerably below the LD,-n dosage, and
(6)
is estimated at 1500 mg/kg (rats) and 1035 mg/kg (mice). The single oral
(4) Monta, M. and G. Ohi, "Paradichlorobenzene in Human Tissue and Atmos-
phere in Tokyo Metropolitan Area," Environ. Pollut., 8, 1975.
(5) Jondorf, W.L., et al., "Studies in Detoxication — The Metabolism of
Halogenobenzenes. 1:2:3:4-, 1:2:3:5- and l:2:4:5-Tetrachlorobenzenes."
Biochem. Jour. 69:181, 1958.
(6) Fomenko, V.N., "Determination of the Maximum Permissible Concentrations
of Tetrachlorobenzene in Water Basins," Hyg. Sanit. 30:8, 1965.
-21-
-------
acute ID_n for 1,2,4-trichlorQbenzene has been estimated to be 756
(7T
'
2.5.2 High Fire Point Transformer Liquids
The 1978 edition of the National Electrical Code added a new
specification for high fire point liquid insulated transformers. Coolant
liquids meeting these specifications must have a fire point of at least
300 °C, must not propogate flames, and must be approved.
A number of methods for evaluating the relative fire safety of
high fire point transformer liquids have been developed by Factory Mutual
Research. This work was performed under a research program sponsored by
the transformer committee of the National Electrical Manufacturers Associa-
tion. Because test protocols are incomplete, Factory Mutual has not formally
approved any liquids as "high fire point transformer liquids." However, they
have given tentative acceptance to a number of commercially available liquids
based on silicones, synthetic hydrocarbons, and paraffinic hydrocarbons.
Acceptance means that Factory Mutual recommends that insurance companies
insure facilities where high fire point liquid-filled transformers containing
accepted liquids are installed in accordance with the requirements of the
National Electrical Code. However, the insurance company reserves the
right to require additional fire protection at a later time if such a need
is demonstrated by experience.
Formal, approval requirements have not yet been established by
Factory Mutual, but draft approval requirements are in the process of review
by the standards group. The suggested criteria would require (a) that
transformers filled with.. approved less flammable liquids be installed in
a diked area where the diked volume is sufficient to contain all of the
liquid and Qb) that the diked area be drained to a safe location if this
is feasible. Any approved liquid having a fire point above 300 °C could be
used in transformers in flammable buildings having sprinkler systems. In build-
(7) Brown, V.K.H., "Acute ToxLcity and Skin Irritant Properties of 1,2,4-
Trichlorobenzene," Ann. PGUP. Hyg. 12:209, 1969.
-22-
-------
ings of nonconfaustible construction (without sprinklers), the minim™ allowable
ceiling height over a high fire point liquid-filled transformer would be
based on the heat release rate of the particular liquid used in the transformer.
The heat release rate used in this calculation would be treasured for each
liquid in a test involving a burning quiescent pool of standard size/ temper-
ature, and ignition source.
The properties of the liquids presently accepted by Factory Mutual
are sunmarized in Table 2.5.2-1 as abstracted from manufacturers1 literature.
The major contenders for this market at present are the dimethyl silicones
and the RTEmp parafinic hydrocarbon. The silicone dielectric is more costly,
but it has a lower heat of combustion than ETEmp. The importance of the heat
of combustion of a non-propcgating liquid is also being investigated by the
National Bureau of Standards under a program sponsored by the U.S. Department
of Energy.
There are a number of questions not yet satisfactorily answered con-
cerning the use of the high fire point transformer liquids. The most important
question is: how realistic are the test conditions? It has been suggested
that catastrophic arcing followed by case rupture is a relatively unusual mode
of transformer failure and that a more frequent problem is prolonged minor.
arcing which generates flammable gases caused by the breakdown of transformer
fluid. Because of flammabilily of these gases/ tests based on the flash point
or flammability of unused liquids may not be reliable indications of their
relative fire safety under actual transformer operating coalitions.
2.5.3 Oil Insulated Transformers
If fire safety were not a consideration, oil-filled transformers
could be used in all applications. Askarel transformers historically cost
about 1.3 t^ray* more than oil-filled units of the same capacity. As the result
of costs/ most users have preferred to use the oil type unit where possible.
The oil filled transformers are the same size as the askarel units and are con-
siderably lighter in weight. Furthernore, mineral oil has somewhat better heat
transfer characteristics than askarel/ and an electrical arc in mineral oil
-23-
-------
Table 2.5.2-1
High Fire Point Transformer Liquids
Type of Liquid
Chemical Ccnpositlon
Cannerclal Products
Dielectric Constant
ASIM D-924
Dielectric Strengtli
ASTM D-877. A9TM D-1816
Resistivity ol«n-cm
ASTM D-1169
Dissipation Factor
AfTlft p-924
Flash Point
Fire Point
Heat of Combustion
Pour Point
Arc Docuivoaltion Products
Specific lleat
Coefficient of Expansion'!)
Specific Gravity
Silicons
Polydimsthyl siloxane
- |si(aii)iO-in-
DC 561 - Dow Oorning
EC 200 - Dow Corning
SF 97 - General Electric
L 305 - Union Carbide
F 101 - SWS Siliconea
F 190 - SWS Siliconea
2.72
35 KV (45 KV at 50 ppn water)
guarantee
7.1 x lO1*
1.8 x 10~s (100 hz, 23°C)
- 300°C
- 360°C
7.67 kca I/gram
- 55"C
Hydrogen, methane, ainorplious
silica
May form GO on burning
.34
.00104
.961 (25°C)
Hydrocarbon
Paraffinic oil refined from
crule oil - (ai2) - plus additives
RTBip - RTE Corp.
2.30
43 t 2 KV
8 x 1012
1 x 10~* (25°C)
285°C
312°C
11.0 kcal/gram
- 30°C
Hydrogen, methane, SOJIIB higlter
hydrocarbons
May form OO on burning
.46
.00085
.876 (25°C)
Synthetic Hydrocarbon
Poly alpha olefins - (CIlj) -
FR Dielectric Fluid -
Gulf Oil Chemicals Co.
PAO-13CB - Uniroyal Oicmlcal
2.11 (FR)
2.11 (PW>-13CE)
46 KV (FR)
39 KV (PAO-13CE)
7 x 10* " (FR)
6 x 10IS (PWJ-13CE)
2 X 10~ 5 (FR)
1 x 10"* (2"W1 tPWVlVEl
298°C (FR)
290 °C (PAD-13CE)
320°C (FR)
307°C (PAO-13CE)
10 kcal/graia (FR)
- 45°C (FR)
- 44 °C (PWJ-13CE)
Hydrogen, methane, saic higher
hydrocarbons
Hay form CO on burning
.42 (FR)
.00081 (FR)
.00075 (PAD-13CE)
.857 (FR)
.84 (PWV13CE)
*— •— '•« ^» — r
•b
t
-------
Table 2.5.2-1, (Continued)
High Fire Point Transformer Liquids
Viscosity - CS<2)
25"C
100 °C
150°C
Corroalvlty
Solvency
Acute Itoxiclty
Oral
Inlialation .
Denial
Bye Contact
Chronic Ibxlclty
Mitagenlcity
50
16
12
Not corrosive to normally
used transformer materials
Swells silicons rubber, may leach
plasticlzars from plastics causing
ahrjnkftje and hardening. O)
Non toxic (4'5)
U>5fl > 20 gmAg
Non toxic*4'
Nan irritating'4'
Very sllgnt %nd transient irrlta-
tta,.«
47 tjiv/kg/day - no toxic
effect (guinea pigs)
20 9i\/kg/day - no toxic
effects (rats)
FW allows polymQtliyl siloxanes
as food additives tip to 10 ppn
No effects noted' '
3!>0
16
5.5
Not corrosive to normally
used transformer materials
Swells butyl rubber, no effect
on most materials
Non toxic .,.
ID5Q > 10 gmAg|D'
May contain up to 2t ncn-
parafflnlc additives .including
aromatic compounds
lang tetra exposure limit = 5 rog/ra
(Note - higlter tlian can be
achieved under normal mfg or use
contlitions)
No dermal effects Identified
in industrial hygeite survey (5)
Very allcjht and transient
irritatlon<5).
Nr>t test o.l
Ames test did not show any affect
of chemical in eitl\or pure or rat
liver activated cultures (IW)-20E)
PAO-13CB PR
1 87 (38°C)
14 i n
? ?
Not corrosive to normally
used transformer materials
Swells butyl rubber, no effect
on most materials.
Nan toxic
ID^frats) > 40 mlAg (PAO-13Q
No skin irritations after 72
hour exposure - rabbit
(P7\Q - 13CE)
No ocular reactions observed -
rabbit (PAO - 13CH)
Ames test did not sliow any
affect of chemical in either
pure or rat liver activated
cultures (PAO- 13CE) (FR)
N)
-------
Table 2.5.2-1, (Continued)
High Fire Point Transformer Liquids
Carcinogenic! ty
Uloaccunul a tion
Diottegradation
Environmental Fate
Ultimate Disposal
Experience in transformers
Cost
No effects noted <4>
U*,«>
IA\
Does not biodegrade '
Stable In environment; may
eventually deocxrpose to silica
on activation by UV light <4>
n\
Incineration1 '
~ 12.00/gal-large quantities
~ 15.00/gal-srnall quantities
Non carcinogenic ' baBed ujxxi
nutogenicity testing.
I^'6)
Biodegradable (6)
Degraded to water and carbon
dioxide
Incineration
Used since 1970
i ' i
6.90/gal 4500
-------
NOTES: Table 2.5.2-1
1. All liquid-filled transformers contain a vapor space that is filled with
nitrogen gas. The increased pressure due to thermal expansion of the
liquid depends both on the volume of the vapor space and the solubility of
nitrogen in the liquid. Tests reported by Dow Corning indicate that the
pressure rise in operating transformers is about the same for both liquids
/Q\
even though the silicone expands more.v '
2. Most transformers depend on natural convection to circulate the dielectric
liquid between the core and the cooling fins. The efficiency of the con-
vective cooling depends on the change in density of the fluid over the
range of temperatures experienced and on the viscosity of the fluid
over this temperature range. The silicones have a greater coefficient
of thermal expansion than the hydrocarbon liquids, but they also have
a higher viscosity at temperatures above 100°C. Since the limiting fac-
tor in transformer life is the maximum hot spot temperature/ which
controls the rate of degradation of the solid dielectric material, the
performance of the liquid coolant at the maximum temperature is perhaps
more important than the average liquid temperature. At the maximum temp-
eratures found in a transformer, the hydrocarbon liquids would be expected
to have a lower viscosity than the silicones, but this lower resistance
to convection is offset at least in part by the lower thermal expansion
of the hydrocarbons which results in a Lower driving force for convection.
In general, both silicones and the hydrocarbon oils are less effective
coolants than askarel, although changes in the design of new transformers
can compensate for this difference. Preliminary tests have indicated
that paper insulation degrades less rapidly in both silicone and hydro-
carbon liquids than in askarel, perhaps due to the absence of acid
(8) Page, William C. and Terry Michand (Dew Corning Corp.), Development of
Methods to Retrofill Transformers with Silicone Transformer Liquids,
Technical Paper presented at 1977 EEI Conference.
-27-
-------
NOTES: Table 2.5.2-1 (Continued)
degradation products. Therefore, transformer life might not be signi-
ficantly reduced even if the non-askarel liquid operates at somewhat
higher temperatures than would be experienced with askarel.
3. Hurley/ J.S. and A. Torkelson, (General Electric Co.), "Silicone .
Dielectric Fluids for Liquid Filled Transformers," IEEE Paper
C-74-264-8, Jan. 27, 1974.
4. Summaries of health, environmental, and fate effects of silicones:
Howard, P.H., P.R. Durkin and A. Hanchett, (Syracuse University Research
Corp.), Environmental Hazard Assessment of Liquid Siloxanes (Silicones),
Washington, D.C., Office of Toxic Substances, "u.S. Environmental Protection
Agency (Report No. EPA-560/2-75-004), September, 1975.
Calandra, J.C. et al., "Health and Environmental Aspects of Polydimethyl-
siloxane Fluids," Polymer Preprints, 17(1), 12, April 1976.
5. Toxicity of Combustion Products of Polydimethyl Siloxane
The products of complete combustion of polydimethylsiloxane are water,
carbon dioxide, and amorphous silica. Some of the silica is present in
the smoke as finely divided particles, and the balance remains as a solid
on the surface of the burning silicone fluid. Incomplete combustion of
silicone fluids produces methane, carbon monoxide, and hydrogen in addition
tq\
to the previously mentioned compounds.x '
The toxicological effects of amorphous silica are of more concern than
those of the other combustion products. OSHA is presently in the process
of setting new exposure standards for amorphous silica. The present OSHA
standard limits workplace exposure to 80 mg/m /% SiO- and is based on the
results of tests run with amorphous silica in the form of diatomaceous
earth. Diatomaceous earth generally contains small amounts of crystalline
silica which is a known cause of silicosis. The industry contends that the
79)Burrow, R. F. and T. Orbeck (Dow Corning), Performance of Silicone
Fluids as Insulating Liquids for High-Voltage Transformers, Doble
Engineering Client Conference, Boston, Mass., April 22-24, 1974.
-28-
-------
NOIES: Table 2.5.2-1 (Continued)
presence of crystalline silica in diatomaceous earth produces biased test
results which implicate amorphous silica. The industry has submitted
additional test results which indicate that the chronic toxicity of amor-
phous silica, uncontaminated with crystalline silica, is very low and
that any lung damage caused by inhalation of amorphous silica particles
reverses itself after exposure ceases.' ' ' A NIOSH study entitled
"Comparative Chronic Inhalation Studies of Synthetic Amorphous Silica" is
currently in progress and should resolve this issue.
A study of the reports available indicated that short-term inhalation of
smoke from the combustion of polydjmethylsiloxane would probably cause no
lasting effects attributable to the products of combustion.
6. Piotrowski, Margaret (REE Corporation), Toxicity and Environmental Impact
of Askarel Substitutes, Waukesha, Wise.: KTE Corp., Sept. 23, 1977.
7. All of the high fire point liquids can be ultimately disposed of by incin-
eration. The hydrocarbons could be easily added to residual fuel oil
and burned in industrial boilers. The silicones, however, would yield
considerable amounts of amorphous silica which could present a problem
in contributing to stack gas opacity.
(10). Sarnac Laboratories, Regarding the Biological Activity of Hi-Sil
'Dust 101, New York: December 21, 1950.
(11)- Schepers, G.W.H., The Biological Action of Inhaled Submicron Amor-
phous Silica; Hi-Sil 233, Ann Arbor, Michigan; University of
Michigan, April 30, 1958.
-29-
-------
results in breakdown products that are non-corrosive. Compared to high
fire point liquid-filled transformers, the oil-filled transfOCTETS should
be cheaper, lighter, smaller, and operate at lower temperatures.
Flarniability. The major disadvantage to mineral oil is flanmability.
Transformer mineral oil has a flash point of 145°C, and if an arc occurs
within the transformer, the breakdown products will be hydrogen and methane,
both of which are flammable. Detailed records of such failures are main-
(12.)
tained by the electrical industry.v ' Where oil-filled transformers are
not specifically prohibited as on-site replacements for askarel-filled
units, the National Electrical Code imposes certain restrictions on their
mode of installation. (See Table 2.-5-1)
Oil-filled transformers are used in almost all power transformer
applications and for most substation distribution applications where the
high voltage from the transmission lines is reduced to 12.8 kv for local
distribution. Most pole-mounted, transformers that reduce the voltage to
220 volts are also oil-filled. The issue of flattmability becomes important
if a distribution transformer must be buried (as in many urban applica-
tions) or located close to, within, or on the roof of the building it serves.
An oil-filled transformer can be used in these applications only if it is
suitably isolated from flammable structures or if these structures are suit-
ably safeguarded against fires.
When a transformer is located outside the building it services,
the low-voltage power must be brought into the building via cables or
insulated buses, incurring arfrrHtiorv*! energy losses caused by heating of the
longer low-voltage transmission lines. For large buildings such as tall
office buildings or large shopping centers or for heavy loads such as
electric furnaces, the cost of these losses of electrical energy can easily
exceed the higher cost of installing the transformer nearer the loads.
(12) Edison Electric Institute, Report on Power Transformer Troubles,
Publication No. 71-20, 1971.
-30-
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Vaults. The installation of oil-insulated transformers in
buildings must comply with local electrical and bin Iding codes.. These codes -
are usually based on provisions of the National Electrical Code (NBC). The
NEC requires that all oil-filled transformers, except small low voltage units,
be installed in fire resistant vaults with the following exceptions (NBC:
Section 450-24):
1. If the total capacity of the transformer does not
exceed 112-1/2 KUA, vault walls need only be 4
inches thick instead of 6 inches as specified in
Section 450-42.
2. Where voltage -does not exceed 600, a vault shall not
be required if suitable arrangements are made to
prevent a transformer oil fire from igniting other
materials.
Sections 450-43 through 450-47 of the NEC give detailed
specifications for vault doors, ventilation, drainage, pipe, and ductwork.
Vaults in buildings are constructed as integral parts of the buildings.
Accordingly, the costs of such vault construction cannot be easily estimated
since the presence of a vault affects building design (i.e., strength of the
supporting structure). Further, vault construction is performed as part of
the general construction of the building. Transformer vault construction
is so costly that very few oil insulated transformers have been used
in buildings. Cost estimates based on a standard 1000 KV&. 15 KV transformer
indicate that the cost of the vault would be 133% of the transformer, compared
to a 75% premium for an askarel transformer installed with a catch basin and
outside vent. Oil insulated transformers may be located adjacent to build-
(13) Vfestinghouse, Is There Another Way?, Sharon, Pa.
-31-
-------
ings if adequate safeguards for fire protection are installed. In many urban
areas, precast concrete manholes are used to house transformers in underground
vaults adjacent to the buildings they serve. The steel gratings in the side-
walks of downtown areas are often the vent openings for transformer manholes.
Availability. Transformer oils currently used are naphthenic
base ma-haT-iais, Although there are no problems with the present supply of this
special grade of oil, it is likely that naphthenic crude oils will be in
short supply by 1385. To overcome possible future shortages of suitable
transformer oils, the Electric Power Research Institute is funding studies
by -fee Vfestinghouse Research and Development Center, the McGraw-Edison Company,
and General Electric Company. The purpose of these studies is to evaluate the
performance of paraffinic-base transformer oils with heat transfer properties
(14}
comparable to presently used oils. Tests are being performed to compare
various properties of the two types of oil including lubricity, gasing
tendencies, oxidation stability, material compatibilities, aging at elevated
temperatures, corona and high-current arcing characteristics, and simulated
transformer performance. In addition, General Electric is revie/fing future
availability of insulating fluids. GE has reported that the paraffinic oils,
which have been processed to reduce the temperature of wax formations to below
-40 °C, compare favorably with the presently used naphthenic oils and that no
significant supply problems for paraffinic oils are anticipated.
2.5.4 Air Insulated Dry Type Transformers
The operating life of any transformer depends on the rate of degrada-
tion of the insulation on the windings. The standard organic insulations
(14) Dougherty, John J., "R&D Status Report, Electrical Systems Division,"
EPRI Journal, November 1977, p. 45.
(15) ~~ Rouse ,_J\O. (General fiiectric_Co.'), "Evaluation of Alternate Mineral
Oils' for Use in_ Transfonnefs""and Other Electrical "Apparatus,11 Cofifer-
"ence Record of 1978 TKRF. International Symposium on Electrical Insula-
' (78CH1287-2-EI), Piscataway, N.J.: TKEF! Service Center, 1978.
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that have been used for many years, such as paper and fabric, have performed
satisfactorily when limited to the standard temperature rise of 65°C set by
ANSI C57.12.10-1977. Liquid cooling, either convective or forced, has been
used--to ensure that this temperature rise is not exceeded.
The development of insulations based on glass, nomex , and high
temperature potting compounds has allowed the design of transformers with
a 220°C temperature limit. These transformers can be designed for
operating with direct air cooling of the coils which eliminates the require-
ment for liquid coolants. Although the design of an air-cooled transformer
sacrifices certain desirable properties, the SC units are cost competitive
with oil-filled transformers on a 'first-cost basis where the oil-filled
units must be installed in a vault,
Open Conventional Wound Transformers. Open coil air-cooled trans-
formers are available in sizes up to 750 KVA in single-phase and 5,000 KVA
in 3-phase units and are therefore generally available as alternatives to
oil-filled transformers where a vault would be required for the oil-filled
unit. Complete specification of air-cooled transformers must consider
many details as summarized in the specification guide prepared by Lazar.
The major factors that must be considered in choosing between oil-filled and
air-insulated transformers include:
Vault requirements. Oil-filled transformers above 112 KVA must
be installed in 6-inch thick concrete vaults. 'Dry air-cooled transformers
above 112 KVA, must be installed in a "transformer room of fire resistant
construction."
Voltage. Liquid-filled transformers below 600 volts do ncrc
.require vaults. Dry air-filled transformers are limited to a maximum of
34,500 volts because air is a poorer electrical insulator than liquid.
(16) Lazar, Irwin (The 'Heyward-Robinson Co.), "Making the Choice Among Dry ,
Liquid, and Gas Transformers," Specifying Engijneer, June, 1977,
pp 92-96.
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Basic Impulse Level (BID: This is the voltage at which the insula-
tion breaks down resulting in internal arcing. A high BIL provides additional
protection against transformer failures caused by transient high voltage from
lightning strikes and switching surges. Dry air-cooled transformers have
Basic Impulse Levels 25 to 50 K7 lower than liquid-filled transformers, al-
though ratings up to 150 K7 are available as an option. The lower resistance
to transient voltages requires that more attention be given to proper sizing
of lightning arresters installed with dry transformers.
Overland Characteristics. The coolant in a liquid-filled trans-
former provides a heat sink which absorbs heat generated when a transformer
operates at greater than design loads. Liquid-filled transformers are
designed for normal coil temperatures of 55 °C above ambient at full load
conditions and have insulation rated at 120°C. This 40°C allowable tempera-
ture increase, together with the heat sink provided by the oil, allows
liquid-filled transformers to operate at 200% of rated capacity for one half
hour.
Dry transformers are designed for either 80°C or 150°C normal tempera-
ture rise and have insulating systems good to 220°C. The lack of the heat
sink provided by oil results in more rapid temperature buildup during overload
operating conditions. Although an 80°C temperature rise transformer will be
better able to handle temporary overloads than a 150°C transformer, both types
of dry transformer are limited when compared to liquid-filled units. There-
fore/ if widely fluctuating loads are encountered, dry transformers must often
be specified 20% to 30% larger (in KVA rating) than liquid-filled units to
ensure comparable operating life.
Efficiency. Energy losses occur in a transformer due to both
hysteresis losses in the core and resistance heating of the windings. The
amount of loss is a function of many different design factors. The lower
temperature rise in an 80°C temperature rise winding vs 150°C winding is
; 'achieved by using larger wire and thereby reducing resistance losses. The
effect of these energy losses on the economics of transformer loss and
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operation was recently discussed in an article by Frank. ' Since load
losses and total losses are a result of design choices resulting from
economic trade-offs, comparison of long-term electrical operating costs of
liquid air-cooled transformers must be based on consideration of the
•operating characteristics of specific transformers. - .
Noise Levels. Dry transformers have an operating noise level
3 to 6 db greater than liquid-filled units (i.e., 2 to 4 times as noisy) .
This may be an important consideration if the transformer is to be installed
in a building. Additional sound proofing may be required to make indoor dry
transformer installations acceptable. '
Environment. Open coil air-cooled transformers must be
located in fairly clean, dry areas *and require protection from weather.
Intermittent operation of open coil dry transformers is difficult since the
coil insulation can absorb moisture from the air which degrades the
electrical properties of the insulation. This is not normally a problem
when the transformer is energized because the no-load losses generate enough
heat to dry out the insulation. However, care must be taken to dry out
open coil transformers before returning them to service if they have been
allowed to cool. These transformers are also subject to clogging by the
electrostatic attraction of dust to the coils from the cooling air, and
periodic maintenance is required to remove the accumulated dust.
Weight and Size. Dry air-cooled transformers generally weigh
about the same as liquid-filled units but require up to 20% more floor
space. In the case of oil- filled transformers located in buildings, the
required vault results in even greater space and weight penalties.
Cast Coil Transformers. Cast coil transformers differ from
conventionally wound dry-type transformers in that the high voltage coils
or both primary and secondary I lg are imbedded in vacuum cast epoxy
resin reinforced with fiberglass. This type of construction increases
the BIL rating, decreases the noise level, and eliminates the sensitivity
to environmental moisture. The cast coil transformers are generally more
(17) Frank, Jerry (Sorgel Electric Corp.), ."Watch Out for Energy Losses in -
Transformers," Electrical Construction and Maintenance, Aug. 1975, pp. 53,4.
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compact, lighter/ and more shock resistant than either liquid-cooled or
open coil dry transformers. The epoxy also provides a heat sink so that
the cast coil transformer can withstand temporary overload conditions better
than the open coil units.
Satisfactory thermal performance of cast coil transformers is achieved
by reducing resistance losses in the coil conductors. This significantly
increases manufacturing costs and initial price but decreases electrical
•operating costs compared to open coil air-cooled transformers.
Although -die cast coil transformers are among the nest expensive in
terms of initial cost, they are being used more and more where reliability,
small size, and fire safety are important considerations as in underground
coal mine load centers.
2.5.5 Gas-filled Sealed'Transformers
A dry transformer can be provided complete protection from environ-
mental effects by sealing it in a pressure tight container and using an inert
gas as the coolant. Gas-filled sealed transformers have the same overload
limitations as dry air-cooled units, but better control of the insulating
media raises the maximum achievable voltages to the same levels possible with
liquid filled units. '
Several different gases have been used as the coolant in sealed
gas-filled transformers. The most commonly used gas in the United States is
hexafluoroethane (CzFs). Although chlorofluorocarbons are regulated by the
EPA, the use of this gas in transformers will probably not be affected by
*
the regulations. Nitrogen and sulfur hexafluoride have also been used
successfully as transformer coolants in certain applications.
Because the inert gas increases in pressure when heated, gas-filled
transformers must be enclosed in heavy pressure vessel housings. The
pressure vessel increases both the size and weight of the gas-filled trans-
* Phone conversation with Perry Scunner, Office of Toxic Substances, USEPA.
Washington, D.C., December 22, 1977.
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former compared to open air-cooled units. The price of the sealed gas-filled
units is also considerably higher than open air-cooled units. Because of
the poorer heat transfer characteristics of the gas compared to liquids, 'the
gas-filled transformers are designed to operate at 150°C coil temperature
rise and have insulation systems limited to 220°C. Best spots in the coils
can approach 220 C; accordingly/ there is no allowance for even short-term
operation at loads higher than rated capacity.
Successful engineering development of a hybrid gas/boiling-liquid
transformer could solve many of the heat transfer limitations of the sealed
gas-filled design. Such a hybrid transformer could in concept be achieved
by using an inert liquid coolant having a .low surface tension and an
atmospheric boiling point of about-100°C. The amount of liquid used could
be one tenth the total void volume with a conventional dielectric gas filling
the other 90% of the volume. When the transformer is operating, the liquid
would wet the solid insulation by capillary action and would boil off the
hot spots providing localized cooling where most required. The vapors would
then condense in the cooling coils and run down into the sump. Perfluoro-
carfaon liquids that have the required electrical and physical properties are
commercially available. The present high cost of these liquids (on the
order, of $300 per gallon) would require that the transformer design be
optimized to make efficient use of the boiling heat transfer characteristics
and to minimize the amount of liquid required.
2.6 Relative Costs of Substitutes for Askarel Transformers
Askarel transformers have been used primarily in those applications
where fire safety, reliability and small size have been important factors.
Installation of high fire point liquid-filled transformers is allowed by
the requirements of the National Electrical Code in the same conditions as
PCB-askarel transformers. The only exception is that no outside vent is
required for the high fire point liquid units. Since the nigh fire point
liquid units are less expensive than askarel transf oncers, it is anticipated
that the ban on the use of PCBs will have little economic impact provided
-37-
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the high fire point liquid units prove to give equivalent fire safety and
performance. It must be realized that the high fire point liquid units
have •• not been proved by long field experience and tnat questions of relative
flammability and the heat of combustion of various liquids have not been
thoroughly investigated. Nevertheless, it appears likely that adequate
substitutes for new askarel transfontvars will be developed.
The final choice of a transfonner depends on a wide range of techni-
cal factors. Given the availability of alternative transformer designs, the
final decision must depend on total installed cost, maintenance costs and
electrical operating costs. The relative installed costs of alternatives to
PCS transf outers are summarized in Table 2.6-1.
2.7 Effect of. the PCBs Ban on New Transformer Installations
Power Transformers. Very tea power transformers have utilized PCBs.
The availability of high fire point liquid-filled transformers should provide
necessary fire safety at reduced cost. Design alternatives for each installa-
tion/ including vaults and safer siting of transformers, could allow safe use
of oil-filled transformers.
Distribution Transformers. Presently available alternatives to
PCB-filled transformers include high fire point liquid-filled transformers
and air-cooled, gas-filled and oil-filled transformers in vaults. The high
fire point liquid units have not been formally approved, and the evaluation
of fire safety is not yet complete. However, this type of transformer is
being used and is both less expensive and lighter than equivalent PCS units.
Cast coil transformers are also available in sizes to meet most of the pre-
vious demand for askarel units, and the higher initial cost is at least
partially offset by lower operating costs compared with equivalent liquid-
filled units.
Precip-itator Transformers. PCBs have apparently been used more to
assure long-term reliability with no routine maintenance than to reduce
-38-
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Type
Oil
PCS (1976)
High fire point
hydrocarbon liquid
High fire point
silicons liquid
Dry open coil"
air-cooled
Dry gas-filled
Dry cast coil
Table 2.6-1
Cost Comparisons of Oil Filled Versus Other Transformer
Designs Intended for Hazardous Locations*
UOOO KVA, 15 KV Transtonrer)
Catch
First Cost Vault
Basin Vent
Total
Installed Cost
100%
140%
120%
140%
150-170%
200%
150-200%
90-133%
10%
10%''
**
10%
**
2%
***
***
190-233%
150%
120-130%
150%
150-170%
200%
150-200%
* Adapted from: Westinghouse, "Is There Another Way," Sharon, Pa., p. 18
undated; and Deaken/ R.F.J., and Smith, P.D. (Polygon Industries Ltd.),
"Epoxy Insulation - A Netf Generation of Dry-Type Transformers," Paper
presented at the 64th Annual Meeting of the Canadian Pulp and' Paper
Association, Montreal, Quebec, January 31, 1978.
**Catch basin is not required by law or regulation but is required as a
condition for insurance coverage by certain industrial insurers.
***Not required by National Electrical Code, but recotraended by Westinghouse.
-39-
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flammability. Manufacturers anticipate no problems from using oil in all
new precipitator transformers.
Railroad Transformers. The use of PCBs in railroad locomotives and
passenger cars in the United States Northeast Corridor results from a rail-
road operating rule. Similar equipment using oil-filled transformers has
operated successfully in Europe for many years. An experimental locomotive
was built in France about 14 years ago to demonstrate the performance of a
(18)
totally enclosed gas-cooled (sulfur hexafluoride) transformer.v The
transformer performed well on tests, though it was limited in peak power output
because of the overload limitations inherent to dry transformers. That dry
gas-filled transformer was not a commercial success because it was more
expensive than equivalent oil-filled and PCB-cooled transformers in their
electric powered units. During 1973 and 1974, a total of 117 locomotives
with silicone-cooled transformers were put in service on the high speed
*
passenger trains serving the Tohoku and Ne^ Tokaido Lines. These silicone-
f 11 led transformers have continued to perform adequately.
U.S. railroads changed their operating rules on transformer coolants
after the ban on continued use of PCBs was mandated under the Toxic Sub-
stances Control Act. AMIRAK tested a locomotive built in Sweden by ASEA,
which used a transformer designed to operate with either silicone oil or
PCBs. The transformer was initially filled with silicone oil manufactured in
Germany and has operated successfully during the AMIRAK tests. Conrail has
no restrictions on the entry of the locomotive into the tunnels entering
New York City. AMIRAK has indicated that it will probably specify silicone
oil as the coolant in all new transformers. The New Jersey D.O.T. is
presently taking delivery on 230 new "Jersey Arrow 3 " commuter cars which are
equipped with silicone-filled transformers.
715) "Transformateur dans le gaz" ("Gas-Cooled Transformer"), Chemins de
Fer, CCXLVI (Issue 3), pp 96-97, 1964.
* Personal Communication: Y. Naka (Hitachi America, Ltd.) to G. Robinson
(U5EPA), March 17, 1976.
-40-
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Silicone oil as a transformer coolant is more expensive than
pCBs because of poorer heat transfer characteristics and higher cost of
silicone. High fire point hydrocarbon liquids have not yet been tested in
railroad transformers. If they prove to have adequate fire resistance and
performance characteristics, their use would substantially reduce the cost
increases caused by the ban on PCBs.
2.8 Maintenance of PCS Transformers
The manufacturing of new PCS transformers essentially ended in 1977.
As of 1977, there were about 140,000 units in service. Assuming that the
average PCB transformer is 15 years old, it would be expected that the average
remaining service life would be 25 years and that the last PCB transformer
would not be removed fron service for perhaps 60 to 80 years. Calculations of
expected remaining service life depend on the accuracy of two assumptions:
first, that there will be no regulatory action taken requiring that PCB
transformers be removed fron service and second, that routine transformer
maintenance will be possible and allowable.
2.8.1 Make-Up Liquids for Askarel Transformers
PCB transformers require little maintenance other than occasional
checks for leaks and other mechanical damage and routine testing to assure
that the liquid has adequate dielectric strength. Significant leakage and
degradation of the liquid can lead to both overheating and potential catas-
trophic failure of the transformer. Leakage can occur at sight glass
connections and at gasketed access panels to the taps. Degradation is some-
times attributable to Corona discharge through the liquid. Gradual degrada-
tion of the liquid can be due to prolonged exposure to high temperatures and
severe electrical fields in the presence of chemically active metal surfaces.
Another mechanism for degradation is the absorbtion of moisture from air
that may be drawn into the transformer through malfunctioning relief valves
or gasket leaks in the vapor area.
-41-
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Testing the dielectric strength of the PCS liquid in askarel
transformers is a routine maintenance practice. Chemical degradation of the
liquid and absorbtion of moisture may both cause a decrease in dielectric
strength. Should dielectric strength of the PCBs fall below the range of
normal values/ dielectric properties can be restored by filtering the liquid
through Fuller's earth (Diatomaceous earth) to remove moisture and degrada-
tion products. Such filtering can be performed using mobile equipment without
moving the transformer. Checking the electric properties of the PCBs is
normally done at intervals of a year or more. The interval between tests
depends on factors including the relative humidity in which the transformer
operates, the load factor (determinant of normal operating temperature) /
and the potential problems that might occur if a major failure was experienced.
PCBs have been routinely used to make up for liquid lost because of
leakage, because of removal for sampling, or because it was retained by the
filtering equipment while being reprocessed. The ban on the manufacturing and
distribution in commerce of PCBs ends the availability of PCBs for trans-
former make-up. The lack of availability will cause a maintenance problem
unless suitable substitutes evolve.
Most transformer asfrarel-q have been mixtures of PCBs and tri-
chlorobenzene (TCB) . Accordingly, the most obvious make-up liquid would be
straight TCB. Increasing the concentration of TCB results in increasing
solvent strengths in the dielectric fluid mixture. Since the insulation
enamel and other materials of construction were chosen to be compatible with
the original dielectric fluid design mixture, there is a maximum safe con-
centration of TCB. Dilution of the transformer liquid with up to a few per-
cent TCB will probably not cause any problems. However, the transformer
manufacturer should be contacted to determine the maximum safe TCB concentra-
tion for each particular unit prior to TCB use as a make-up liquid dielectric.
Important factors to consider in converting any askarel transformer
to a different "Mqm'ri •in^l"^0 compatibility of the ligniri with the materials
of transformer construction, maintenance of existing levels of fire safety
-42-
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of the unit, and complete miscibility with the askarel in use. Silicone
liquids/ for instance, are soluble in askarel up to a concentration of one
half of one percent (0.5%). Topping off askarel transformer dielectric
fluid with silicons would result either in a layer of silicone floating on
top of the askarel or an emulsion of silicone in the askarel. Any such
two-phase mixture would be subjected to very high dielectric stresses at
the phase boundries. This could lead to corona formation or arcing within
the transformer.
The natural and synthetic high fire point hydrocarbon liquids
are miscible with PCBs. Tests conducted by RTE Corporation indicated that
*
for various canbinations ranging frau 100% askarel to 100% KTEmp:
a. The dielectric strength of the mixture did not fall
below that of pure KEEmp.
b. The fire point of the mixture did not fall below that of
pure KTEmp.
c. No liquid volume problems occurred since the coefficient of
thermal expansion is about the same for askarel and KCEmp.
d. The viscosity of the mixture increased with increasing concen-
trations of KCEmp, and the transformer operating temperature
increased with the viscosity. This effect was negligible at
the low concentrations of RTEmp that would normally be encoun-
tered in a make-up fluid situation.
e. Mixtures of askarel and REEmp having a density of about 1.0
could conceivably result in any water present forming a two-phase
suspension instead of floating or sinking. This could cause
internal arcing in the transformer, although it is unlikely
that this much moisture could be present without seriously
degrading the dielectric strength of the mixture. RTE Corpora-
tion recommended that the concentration of KFEmp used as
make-up be limited to less than forty percent by volume to
avoid this density range, at least until additional work
determines whether a real problem may exist.
Personal Communication: James B. Caldwell (HIE Corporation) to Robert
Westin (Versar), October 14, 1977.
-43-
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The National Fire Protection Association (NFPA) has not yet con-
sidered the status of mixtures of askarel and high fire point transformer
liquids in the context of the National Electric Code. The NFPA definition
of askarel as being a chlorinated liquid would appear to exclude mixtures
of PCBs and hydrocarbons from this class of transformer liquid. However,
the only difference between the installation requirements for askarel trans-
formers and high fire point liquid-filled transformers is the requirement
of outside venting for askarel transformers to prevent the accumulation
of toxic gases inside a building following the occurrence of an arc within
the transformer. It seems unlikely that the presence of small amounts of
hydrocarbons in the askarel would make any significant change in the
toxicity of the gases and, accordingly, tne need for outside venting. Since
the principal consideration is the effect of the addition of make-up
dielectric liquid oh the insurability of each installation, the insuring
company should be contacted for advice on a case-by-case basis until
recognized national guidelines have been developed.
•
2.8.2 Retrofi 1.1 ing Askarel Transformers
• •. . *
Two conditions that might, require complete replacement .(retro-
filling) of the dielectric liquid -in an askarel transformer are:
1. Loss of liquid because of a spill and
2. Such severe degradation of tne liquid tnat it cannot be
reclaimed by conventional filter processing.
Replacement with non-PCB liquid would also reduce the liability for damage
that would otherwise be caused by a spill of PCBs.
Problems encountered in retrofilling a transformer are the result of
differences in lubricity and heat transfer capabilities of the replacement
liquid and of the difficulty in removing all of the PCBs from the insulation
and windings prior to adding the replacement dielectric fluid. The same
considerations apply to the choice of a retrofill liquid as were previously
discussed for high fire point transformer liquids and conventional transformer
oils.
-44-
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Extensive experimental work has been done to test the feasibility
of retrofilling PCB transformers with substitute liquids. Much of this
work has involved the replacement of PCBs with silicone. Three potential
problems were investigated in this work:
1. Silicone is less efficient as a heat transfer medium;
accordingly, transformers run hotter after being retrofilled
with silicone.
2. Silicone has a higher coefficient of thermal expansion, so
increased pressures might be expected in a silicone-retro-
filled transformer.
3. It is difficult to remove all PCBs from the transformer
prior to retrofilling, and residual PCBs remaining in the
unit have limited solubility in silicone fluid.
This leads to formation of liquid phase boundries, areas of high electrical
stresses, and breakdown of the silicone dielectric fluid. These problems
and the basic problems caused by limited irascibility of PCBs and silicones
(19)
were discussed by Morgan and Osthoff of General Electric.v ' Dew Corning
later summarized their experience gained in laboratory and field retrofilling
since 1972. According to Dow Coming:
The pressure increase is about the same in transformers retro-
filled with silicone as when filled with askarel because the
gas (usually nitrogen) that fills the vapor space is more soluble
in silicone than in askarel.
Silicone filled transformers operate 3 to 10 C hotter than do
askarel transformers at rated load. However, loss of tensile
strength of kraf t paper (insulation) on aging in silicone is
less rapid than on aging in askarel. Therefore, the higher opera-
ting temperatures are not expected to decrease the service life of
the transformers.
(19) Morgan, L.A. and R.C. Osthoff, (General Electric Corporation), "Problems
Associated with the Retrofilling of Askarel Transformers," TKKK Paper
A77-120-9, presented at the TFRR winter Meeting, 1976.
(20) Page, William C. and Terry Michaud, (Dew Corning Corporation), "Develop-
ment of Methods to Retrofill Transformers with Silicone Transformer
Liquid," TTTRF. Paper 22-477, presented at the E.I.C. Conference, Chicago,
Illinois, September 1977.
-45-
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Although all of the askarel could not be removed from the
coils when the transformer was initially flushed, and
although the concentration of PCS continued to increase in the
silicone for several years after the transformer was retrofilled,
field experience with a number of retrofilled askarel trans-
formers has not indicated any electrical failure of the silicone
fluid or other evidence of premature failure of the transformers.
Operating experience with silicone-retrofilled askarel transformers
indicates that the retrofilled transformers operate satisfactorily, although
somewhat hotter, than when filled with PCBs. However, it has not been
demonstrated that it is feasible to flush the transformers sufficiently
to assure that the concentration of residual PCBs in the silicone will be
below 500 parts per million (one pound PCS per 2000 pounds silicone). If the
concentration of PCBs exceeds 500 ppm, the EPA marking and disposal regula-
tions will require that the transformer be marked as a PCB unit and that the
disposal of the contaminated silicones be in accordance with the special dis-
posal requirements for PCBs. Dew Corning has reported that, based on experi-
ence with ten transformers, proper solvent flushing of small askarel trans-
formers (167 to 1000 KVA) has resulted in an initial level of PCB contamina-
(21)
tion in the silicone of between 0.13 and 0.77 percent. The concentration
of PCBs in the silicone slowly increased after the transformers were placed
in service. The increased level of PCBs was caused by residual askarel
slowly leaching out of the paper insulation and coils into the silicone.
PCBs concentration reached a level of from one to four percent after the
transformers were in service for 2 to 3 years. This concentration is
well below the solubility limit of PCB in silicone (reported by GE to be
10% at 25°C and 12% at 100°C - Morgan and Osthoff, 1976). 'At concentrations
of 1 to 4%, no phase discontinuities will occur in the silicone coolant
liquid. However, the leaching process is accompanied by the presence of
PCB and silicone -liquid phases in the insulation and kraft paper. The
practical limit for reduction of PCB concentration in field retrofilling has
(21) Page, William C. (Dow Corning Corporation), Statement on retrofilling
made at the EPA public meeting on the implementation of the proposed
PCB ban, Chicago, 111., July 19, 1977.
-46-
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been estimated to be in the range of 0.3 to 1% PCS in the silicone
when the transformer is initially returned to service. The cost of
such a retrofill program to replace askarel with silicone was estimated
(22)
to be about $30.00 per gallon. Detailed retrofill instructions are
(23)
available from Dow Corning.
The feasibility of removing PCBs from a transformer by flushing
with solvent depends on both the procedure used and the design of the
transformer. The Federal Bailroad Administration has sponsored two research
projects which have retrofilled and tested transformers from commuter cars.
The transformers were 418 KVA units containing 168 gallons of askarel. The
projects were performed by General Electric Company and Westinghouse.
f
The work performed by General Electric Company indicated that
hot draining of the transformer removed 85% of the askarel and that cir-
culating hot silicone fluid through the transformer for 288 hours reduced
the residual askarel to 107 pounds. FCBs and trichlorobenzene were removed
at the same rate, and the rate of leaching of residual askarel into the
silicone was found to be diffusion limited. Operating tests showed that
the transformers ran 9.7°C hotter with silicone than when filled with askarel.
GE suggested that the temperature increase would have been 1S°C had the
cooling fins not been steam cleaned during the flushing procedure. GE did
not report any conclusions as to the long-term performance reliability of
the retrofilled transformer, but they did suggest that the two-phase liquid
(24)
existing in the coils might eventually cause problems.
Westinghouse retrofilled a similar transformer. Initial flushing
was with mineral spirits/ followed by circulation of silicone. Performance
(22) Transformer Consultants (Akron, Ohio), "Silicone Eetrofill of Askarel
Transformers," The Consultor, January 1977.
(23) Dow Corning Corporation (Midland, Mich.), Retrof ill ing with Dow Coming
.: 561(R) Silicone Transformer Liquid, October 19, 1976.
(24) Foss, Stephen D., John B. Higgins7 Donald L. Johnston, James M.
McQuade,. (General Electric Company), Retrofi 11 ing of Rai 1 road Trans-
formers, Report No. DOT-TSC-1293, July, 1978.
-47-
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tests indicated no increase in the winding to fluid temperature differen-
tial and a 2.7 C increase in the liquid temperature following retrofilling
with silicone. Continued operation of the retrofilled transformer resulted
in an increase in the concentration of PCBs in the silicone to 3.47% after
two weeks of operation and 4.37% after four months of operation. The
final report concluded that there was no reduction in operating performance
of the retrofilled transformer and that long-term performance should be
satisfactory, although it could not be determined what the equilibrium con-
(25)
centration of PCBs would be in the silicone.v
There has been little information published on the performance
of askarel transformers retrofilled. with other liquids. Both conventional
transformer oil and the natural and synthetic high fire point transformer
liquids are completely miscible with askarel. Because of this miscibility
there should be no problems associated with liquid phase boundries. If an
askarel transformer were retrofilled with transformer oil, it would need the
fire protection normally required for oil-filled transformers, such as a
vault and/or sprinkler. The unit would also be considered a PCB unit for
purposes of marking and disposal as long as the concentration of residual
PCBs exceeded 500 ppm. A transformer retrofilled with a hydrocarbon liquid
would be subject to the same marking and disposal restrictions, but it
would need venting and vault protection as either a high fire point trans-
former or an askarel unit depending on the advice obtained from the insurer.
In either case, the retrofilled unit would be expected to operate satisfac-
torily. Guidelines for flushing and retrofilling askarel transformers with
hydrocarbon liquid are available fron KEE Corporation. *
WaIsE7~ETj77 D.E. Voytik, H.A. Pearce, (Westinghouse Electric Corp.)
Evaluation of Silicone Fluid for Replacement of PCB Coolants in Railway
Industry, Final Report, Report No. DOT-TSC-1294, December 1977.
(26) Olnstead, John (RLE Corporation), Comments and Recommendations on
Retrof1111ng of Transformers,. Waukesha, Wisconsoji: REE Corporation,
October 31, 1977.
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2.8.3 Removal of Residual PCBs from Non-Askarel Transformer
T.-iqmrfe
Eetrofilling an askarel transformer with a non-PCB liquid reduces
the potential damage that might occur if the transformer were to fail or be
ruptured. Significant cost savings would only be achieved if residual PCBs
could be reduced below the minimum concentration that requires labeling
and disposal as PCB-contaminated equipment. This degree of decontamination
cannot be achieved in a short period of time by flushing the transformer
with solvent since complete removal of PCBs from the insulation and coils is
limited by the rate of diffusion of PCBs into the bulk liquid. The concen-
tration of PCBs in transformers retrofilled with silicone fluid has been
observed to increase for several years following the return of the trans-
former to service. If the contaminated dielectric liquid were replaced
every year or two with clean transformer liquid, residual PCBs would be
eventually eliminated from the transformer. Demonstration of feasible
dielectric fluid decontamination processes allowing immediate use of the
fluid would make this alternative highly attractive.
Recent evaluations have demonstrated that PCBs and trichloroben-
zene are selectively adsorbed, from silicone liquid by activated carbon. Dow
Corning has demonstrated this process on a laboratory basis using contaminated
silicone from a retrofilled transformer that had been in service for ten
months. When the transformer was retrofilled, the concentration of residual
PCS in the silicone was 0.7%. This concentration increased to 2.53% after ten
months. The silicone also contained 5.47% trichlorobenzene at this time.
Filtering the 180 gallons of liquid tiirough 120 pounds of activated carbon for
eight hours reduced the concentrations to 0.43% PCB and 1.80% TCB. Five weeks
later these concentrations had increased to 0.615% and 2.09%, respectively.
The contaminated liquid was then filtered for 5 hours through 120 pounds of
fresh activated carbon, and finally through 60 pounds of a third batch of
activated c^.rhpn filters for one hour. The residual copcsntraf "* <*»"« after
. m\
(27' Dow Coming Corporation, Removal of PCB frcm Dow Corning 561;
Transformer t.igmri by
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this treatment were 472 ppm KB and 0.296% TCB. This left a total of
0.68 pounds of PCS in the liquid and an unknown amount in the coils and
insulation. The filtering was done by pumping the silicone liquid at a
(R)
rate of 5 to 8 gallons per minute through Brute Cartridge Filters
manufactured by DC Filter and Chemical, Inc. Each of the filters con-
(R)
tained 20 pounds of Nuchar W-XG granular activated carbon manufactured
by Westvaco.
For those transformers equipped with a pump, it appears possible
to install a carbon cartridge filter of the type used by Dow Corning adja-
cent to the pump. The filter would continually scavenge residual PCBs
from the silicone after most of the PCBs 'had already been replaced by retro-
filling of the transformer. This procedure might prevent the level of PCBs
in the liquid from increasing to concentrations above 500 ppm. The trans-
former then would no longer have to be classified as a PCS unit. In addition
to the reduction in spill risks, successful decontamination of an askarel
transformer would mean that when the transformer is finally scrapped, special
PCS disposal procedures would not be required. The decontaminated trans-
former could then be sold for scrap instead of being drained, flushed, trans-
ported to an approved chemical waste landfill, and buried. Disposal savings
could be considerable, as present charges for disposal in chemical waste
landfills are in excess of one dollar per cubic foot.
The decontamination of silicone transformer liquids is still
in the experimental testing stage. Westinghouse Electric Corp. has report-
edly applied for .a patent on the process of using activated carbon to remove
* *
PCBs from silicone. No results have been made public on techniques to
remove PCBs from hydrocarbon transformer liquids, although RTE Corporation
is reportedly doing research in this area at the present time.
2.9 The Economic Impacts of Changes in the Expected Service Life of
Presently Used Askarel Transformers
The EPA ban regulations will apparently allow the continued use of PCB
transformers but will ban maintenance that would require removal of the
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transformer coils from the tank. Continued use of the transformer would
require that the user assume any risks associated with a PCBs spill.
The resulting economic impact on transformer users will depend
on both the availability and suitability of make-up liquid and'on the avail-
ability and price of replacement transformers with size and fire safety
characteristics comparable to askarel units in use. Assuming that trichloro-
benzene or high fire point transformer liquids will prove to be satisfactory
as make-up liquids, and assuming that high fire point transformers will be
available for use as specified by the 1978 National Electrical Code, the only
economic impacts associated with the reduction in transformer service life
will be due to the ban on a major rebuilding of failed transformers.
Most transformer maintenance involves cleaning of tap changers,
replacement of gaskets and busings, filtering of dielectric liquid, repair
of minor leaks, and repainting. None of these repairs require that the core
be removed from the transformer casing. Electrical failure can be caused by
deterioration of the insulation or exposure to voltage surges due to light-
ning or other causes. The resulting arcing from phase to phase, .phase to
ground, or phase to core damages the transformer winding. Repair of this
damage requires that the transformer be completely disassembled, the damaged
windings replaced, and the transformer then essentially rebuilt. These major
repairs return the transformer to "like-new" condition but would not be
possible if the removal of the transformer core were banned by the regula-
tions.
Major rebuilding of an askarel transformer costs from fifty to
seventy-five percent of the price of a replacement transformer. The failure
of an askarel transformer often results in complete power loss to the
installation serviced by the unit until the transformer is repaired or
replaced. Because there are many types of askarel transformers in service
and few spares available, it is rare that an equivalent transformer can be
substituted for a failed transformer. Electrical service to the insta.lla-
tion will remain disrupted until the -transformer is repaired or replaced.
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The transformer repair industry is geared to providing emergency service,
with major repairs to most failed transformers accomplished in seven to ten
days. In contrast, delivery of new transformers usually requires 12 to 18
weeks from, the date of order. T his time is required primarily to specially
fabricate the core and casing.
Although many large factories and buildings depend on three or
more identical transformers for power so that the failure of one transformer
will not disrupt the operations of the entire facility, many small operations
(less than 500 employees) are serviced by a single transformer. Disruption
of service for the three to four months required to purchase a new transformer
could have serious economic consequences.
s
Because of the expected demand for replacement transformers on a
priority basis, it is expected that the transformer manufacturers will
increase their inventories of new or leaner units to meet the needs of their
customers. Although incidents of production loss (that could be reduced by
the availability of rebuilding services) will probably continue, the likely
response of industry will be to provide the ecjuipment to minimize these
losses. The effect of the ban on PCBs in transformers will therefore result
in changes in transformer technology and changes in the structure and
responsiveness of the transformer manufacturing industry.
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3.0 ELECTPCMAQ1ETS
Polychlorinated biphenyls have been used as an electrical insulating liquid
in sane electromagnets used to scavenge tramp iron from coal carried on conveyor
belts. These separator magnets are similar in construction to a transformer,
having a single coil on a magnetic core immersed in liquid and contained in
a leak proof case. "Hie heat generation of the unit and the required properties
for the insulating liquid are similar for both transformers and separator electro-
magnets.
PCS filled magnets were supplied on special order by three different manu-
facturers:
Sterns Magnetics, Cudahy, Wise.
Eriez Magnetics, Erie, Pa.
Dings Co., Milwaukee, Wise.
The separator electromagnets manufactured by these companies are suspended
over the conveyor belts where they attract any tramp iron from the coal before
it can be carried into the crusher and possibly damage the equipment. Each of
the magnets of the type used over coal conveyors contains about 135 gallons of
liquid. The standard insulating liquid used by all of these manufacturers was
transformer oil, but special liquids, including PCBs, were used when required by
the customer's specifications. About 200 PGB magnets were manufactured in the
U.S. before manufacturers voluntarily stopped manufacturing them. Sternes
Magnetics stopped using PCBs in 1972, Eriez Magnetics stopped in 1971, and Dings
Co. stopped in 1976.
The PCB-filled magnets were furnished only for coal conveyors in the U.S.
and for a few grain conveyors in Canada.
The failure rate of separator electromagnets has been estimated to be less
than cue percent per year. Failure has usually been caused by mechanical damage
to the case rather than to electrical arcing ard failure. The ban on the use
of PCBs-is not expected to have a"significant impact on the operation of the magnet
manufacturers or the continued maintenance and use of existing magnets.
All three electromagnet manufacturers have successfully used transformer
grade siliccne fluid as an insulating liquid in separator electromagnets of
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standard design. It is expected that other high fire point transformer
liquids will be developed and will be usable in separator electromagnets,
In addition Eriez offers a proprietary air-cooled electromagnet which has
Underwriters Laboratory approval for use 'in dusty and dirty environments.
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4.0 ELECTRIC MOTCRS
Reliance Electric Co. built the only electric motors known to use PCBs
as a coolant. Those motors were installed on certain coal mining machinery
manufactured by Joy Manufacturing Co.
4.1 The Use of Liquid-Cooled Motors in Mining Machinery
The designing of electric motors for use on mining machinery pre-
sents a number of geometric and operational problems. Mining machines for
underground use in low coal seams are designed to an overall height limita-
tion as lew as 22 inches. The width of continuous miners must be less than
the width of the cutting heads, and other equipment must be able to operate
in narrow, low seams. Accordingly/;the space available for mounting electric
motors is very limited. In addition/ the motors must be able to operate in
wet, dirty environments and perform under an intermittent duty cycle.
A basic limitation to the size of electric motors in imposed by
the generation of heat and the need to remove this heat from the windings and
rotor. This heat is generated in much the same manner as heat is generated
in transformers. The motors used in mining equipment are totally enclosed
to protect the them from dust and moisture in the mine and to isolate
flammable dust and methane gas from flame or sparks emitting from the motor
if methane is ignited inside the motor. The motor casing is either air
cooled or water jacketed to remove heat. Heat transfer limitations are
governed by the transfer of heat from the windings and rotor to the fins
or water jacket of the motor. Most motors are designed so that heat con-
vection by the air between the rotor and stator windings will be sufficient
to transfer heat to the cooling surfaces. As in the case with transformers,
greater efficiency in heat transfer can be obtained by immersion of the heat
generating components in a liquid. Because they have more efficient heat
transfer characteristics, liquid-cooled motors can be built smaller than
air-cooled motors of equivalent horsepower.
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Motors cooled with petroleum based hydraulic fluid were first used
in mining machinery in the early 1960s. . However, the potential flammability
of this liquid made it unsuitable and led to the decision to use a less
flanroable liquid as the coolant.
A number of mining machines built in the late 1960s by Lee Norse
used silicone-ccoled motors manufactured by Westinghouse. Because silicone
is expensive, its use was not a satisfactory solution and only a few of
these machines are presently in service.
/2g)
According to Mr. Warner of Joy Manufacturing Company, POB-
ccoled motors manufactured by Reliance Electric were used in three types
of mining machinery built by Joy: ~
1. Fifteen type CU43 continuous miners were manufactured in the
period 1963 through 1967. Each of these machines used three
PCB-cooled motors. Two motors were installed at the front of
the machines adjacent to the cutting heads; they supplied
power to the cutters. The third motor was installed on the
frame of the machine to provide power to the hydraulic sys-
tem that adjusts the cutter heads. These motors were 13 h
inches in diameter, 26 inches long, and were rated at 115
horsepower. Each motor contained about three gallons of
PGBs. The motors were water jacketed and were cooled by
the water that was then sprayed on the face of the coal seam
to reduce dust. A survey by Versar in late 1977 identified
only one mine that was still using CU43 miners. This mine
had three operational machines and was using two machines
full time in production and one as a spare. Most of the
motors on these machines had been converted to silicone
oil coolant. In addition, the mine bought a number
(28) Warner, Edmund M., (Joy Manufacturing Company), Presentation to
Environmental Protection Agency sponsored public meeting on PCBs,
Chicago, HI., July 19, 1977.
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of other used CU43 miners which it now uses as a source
of repair parts. This is a rather large mine, and the
CU43 miners account for probably less than ten percent
of the total production of coal.
2. Fifty-seven type 9CM continuous miners ware sold by Joy
Manufacturing for use in the United States fron 1967 to 1970.
Three PCB-ccoled motors are used in each machine, two built
into the cutting heads to provide power to the cutters and
one on the frame to power the hydraulic system. The motors
are jacketed and are cooled by the water that is sprayed on
the face of the coal. A survey conducted by Versar in
November 1977 determined the status of these 9O1 miners
as follows:
Idle/junked 23
Full time production 11
Operational spares 2
Non—production mine use 2
BducationaVtraining use 1
Unknown 18
3. Five hundred fourteen type 14BU10 loaders were sold to a total
of 88 different customers frcm 1965 to 1973. These loaders
are used in conventional mining where the coal is broken by
blasting and then loaded onto shuttle cars which carry it
to a conveyor. ..The loaders are used to scoop up the coal
and dump it onto the shuttle cars. Each of the 14HJ10
loaders has two PCB-ccoled motors which are used to provide •
traction power to the machines. Each motor is 17 % inches
in diameter/ is 20 1/8 inches long, has fins cast into the TOtor
casing to provide heat transfer surfaces to the surrounding
air, and is rated at 25 horsepower. Each motor contains about
three gallons of PCS which significantly reduces the operat-
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ing temperature of the motor, thereby increasing significantly
• its expected service life. As of July 1977, Joy had con-
verted 353 of these motors to dry (non-PCB) operation. Many
of the 14BU10 loaders were originally purchased by small ,
mines, and it is not known how many of these machines remain
in service.
4.2 Substitutes for PCBs in Electric Motors
The only motors using liquid coolant are those that have been
designed for applications where space is extremely limited. The use of a
liquid coolant introduces two new problems into the design of a motor: first,
the bearings must be able to operate in the liquid, and second, the shaft
seals must be able to prevent leakage of the liquid when it is under pressure
caused by thermal expansion of the liquid when the motor generates heat.
These problems have never been completely resolved, and there are no new
machines presently being built that utilize liquid-cooled motors.
The need for substitutes for PCBs in electric motors is based on
"the need for maintenance of the existing Joy continuous miners and loaders
using PGB-cooled motors. Beginning in 1974, Joy provided a conversion kit
to change the 14BU10 loader motors to conventional dry construction. Joy
estimates that the normal failure rate of the PCB-filled motors would result
in all of the motors being rebuilt as dry type motors by the end of 1981 if
4
the EPA forbids the continued use of PCBs in maintaining this equipment.
The PCB-ccoled motors in the continuous miners cannot be converted
to dry operation. A number of these motors have been rebuilt using trans-
former grade silicone oil as a coolant and have performed sati sfactori ly.
They were converted because previously, silicone oil-filled motors had been
supplied by Lee Norse on certain mining machines that had been approved by
the Mining Enforcement and Safety Administration (MESA) for use in under-
ground mines.
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Review of the use of silicone liquids in coal mines has identified
a potential problem with the methane detectors that are used in these mines
and are mounted on the raining machines. The concentration of methane in the
air is measured by determining the amount of heat generated on a platinum
catalyst by catalytic oxidation of hydrocarbons in the air. It has been
found that silicone vapors will poison the catalyst, thereby gradually reduc-
ing the sensitivity of the detector. It is standard practice in the coal
mines in Great Britain to protect the methane detectors from silicone poison-
ing by using an activated carbon cloth to selectively adsorb any silicones
from the air before the air is passed over the catalyst. However, in Great
Britain the methane detectors are carried by safety inspectors and are
calibrated every shift. Periodic maintenance of the detector and replacement
of the carbon cloth is therefore fairly easy. In the U.S., the detectors
are mounted on the machines and operate in a wetter environment than would
be experienced by units that are carried by inspectors. This moisture
may tend to reduce the effectiveness of the carbon. It would also be
difficult to ensure proper maintenance of machine-mounted detectors.
The U.S. Mine Enforcement and Safety Administration is reportedly
planning to inform all coal mine operators of the potential problems that
might be caused by the use of silicones as motor coolants for mining equip-
ment. Both the U.S. Bureau of Mines and the major manufacturer of methane
detectors are investigating the feasibility of protecting the detectors
should a spill of silicone occur. Therefore, the acceptability of silicones
as a replacement fluid for PCBs in the motors on the Joy continuous miners
must be considered problematical, in spite of recent satisfactory experience.
Peliance Electric has evaluated a number of other liquids as
potential substitutes for PCBs in these motors. The criteria for accept-
able flanmability which they have established requires that no flames or
generation of flammable gases occur following a major electrical arc through
the liquid. None of the high fire point hydrocarbon transformer liquids (or
the silicones) can p^s fh^s test. Trichlorobenzene was determined to have
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adequate fire resistance, but the smell of the vapors was felt to be too
irritating to allow tne use of tnis chemical in motors used in underground
mines. Therefore, Reliance and Joy have reported that a satisfactory sub-
stitute for PCBs does not exist for the motor application.
Fortunately, the lack of an adequate substitute will not have a
major economic impact. A ban on the continued use of PCBs would result in
the early retirement of twelve continuous miners fron coal production.
Most of these machines are already near the end of their economic life and
would not have been used for more than an additional two or three years.
An informal survey of manufacturers of mining machines in late 1977
indicated that the lead time for delivery of new continuous miners was two
to six months, depending on the manufacturer and the model ordered. The
manufacturers do not feel that an immediate demand for 25 or.30 machines
would have a significant impact on this delivery schedule. In addition,
used machines are available which could replace the Joy continuous miners
that use PCB-ccoled motors.
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5.0 CAPACITORS
PCBs have been used as a dielectric liquid in alternating current
capacitors since 1930. The PCB units are about one half the size and are
much more reliable than the previously used mineral oil impregnated capacitors.
PCBs also have the major advantage of being non-flammable. Alternative
dielectric liquids and capacitor designs that do not use a liquid dielectric
have been developed, but none of these combine the features of long life,
high dielectric constant, and low price that have made PCBs so attractive.
The Toxic Substances Control Act banned the use of PCBs in manufacturing
capacitors effective January 1, 1979. Since no equivalent liquid dielectrics
are available, capacitor manufacturers have been forced to redesign their
products and introduce capacitors using new liquids after limited service
testing.
The following sections discuss the use of PCBs in capacitors and the
substitute materials which are being used and considered for use.
5.1 Principles of Capacitor Operation
Electrical capacitors are devices that store energy in the form
of an electric field between two parallel conducting plates when a voltage
differential is applied across the plates. This stored energy reappears as
electrical current when the voltage difference is decreased. The capacitor
therefore performs an electrical function equivalent to that of a spring
in a mechanical system.
If an alternating voltage is applied across a capacitor, the
electric field between the plates opposes the applied voltage. This apparent
resistance varies throughout each cycle and will control the flow of current
through the capacitor. At the start of the cycle when the voltage across the
capacitor is zero, there is no opposing electric field and therefore no
resistance to the flow of current. When the voltage is at a maximum, the
opposing field is also at a maximum., and the current is therefore at a
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minimum. As the voltage decreases to zero, the energy stored in the electric
field reappears as current in a direction opposing the applied voltage. Thus,
the current flowing through a capacitor leads, or precedes in time, the
voltage across the capacitor.
The amount of energy stored in the electric field in a charged
capacitor depends on the intensity and size of the electric field. The
intensity of the field increases with increasing voltage and decreasing dis-
tance between the plates, and the size of the field increases with increas-
ing plate area. The amount of energy that can be stored in a capacitor of
a given size and configuration is measured in units of capacitance.
If a dielectric material:is placed in an electric field, surface
charges appear on the material in such a way that the surface charges oppose
the applied voltage. The dielectric material absorbs energy from the electric
field in developing this resisting field, so the total amount of energy
stored in a capacitor (i.e., the capacitance) is increased when a dielectric
material is present between the plates. The ability of the material to
increase the capacitance is referred to as its dielectric constant. The
dielectric constant is defined as the ratio of the capacitance of a device
when the material fills the space between the plates to the capacitance when
there is a vacuum between the plates.
An ideal dielectric material would give up all of the stored
energy in the form of current when the imposed electric field was removed.
Real materials always absorb a certain amount of the energy which then
appears as heat. As a result of this absorbtion of energy, the charging
current in a real capacitor will lead the voltage by slightly less than the
90 degrees that would be expected for a perfect capacitor. The angle by
which the current differs fron 90 degrees is known as the dielectric loss
angle and is a measure of the efficiency of the dielectric material in storing
energy. 'This relationship is often reported as the loss tangent, which is
the tangent of the loss angle. 'The total portion of energy lost through
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dielectric heating of the naterial is the dielectric power factor, which
for most materials is approximately equal to the product of the dielectric
constant and the loss tangent. .
Energy can also be generated in a capacitor via the conductance of
electricity by the dielectric material which results in resistance heating.
The resistivity of the material is a measure of the degree to which the
conduction of current is resisted by the material.
The distribution of voltage between the plates of a capacitor
depends on the distance between the plates, the average imposed voltage, and
the geometry of the plates. In general, the voltage stress (rate of change
of voltage with distance) is proportional to the diameter of the charged sur-
face, so high voltage stresses are experienced at plate edges and at any
rough areas or projections fron the plates.
Sufficiently high levels of applied voltage stress can cause
electrons to be separated from the molecules of the material and to thereby
become available to conduct current. The voltage stress at which this
ionization will be initiated for a particular material is known as the
corona inception voltage. If this voltage stress is exceeded, the dielec-
tric material becomes a conductor, resulting in greatly increased resist-
ance heating. Once corona discharges start in a material, they continue
until the voltage is decreased to a level below that at which the discharge
started. Capacitors operating on alternating current would be expected to
have small areas of corona discharge every cycle at localized edges and
rough areas of the conducting plates. To minimize the time that this
. condition continues when the voltage decreases, it is important that the
corona extinction voltage be as high as possible.
If several dielectric materials are present between the conducting
plates, the voltage stress is distributed across the materials in a ratio
inversely proportional to the dielectric constants of the materials. For
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instance, if the dielectric material is porous paper having a dielectric
constant of 6 which contains air having a dielectric constant of 1, the
voltage stress across the air vail be 6/7 of the total applied voltage, and
the stress across the paper will be 1/7 of the total.
Air has a fairly low corona inception voltage and a dielectric
constant of about 1. Therefore, air bubbles in the dielectric material in
a capacitor will be subjected to high voltage stress levels which will
result in corona formation at relatively low levels of applied voltage. For
this reason, most A.C. capacitors are impregnated with a dielectric liouifl
that displaces the air from the porosity of the solid dielectric and fills
the gaps between the plates (usually metal foil) and the solid dielectric
material that structurally separates the plates.' This liquid also absorbs
gases formed by corona discharges and flows into any vapor pockets which may
be formed by corona or minor arcing. Therefore, liquid impregnated capa-
citors are to some extent self healing, a feature that explains their relia-
bility.
The charges in a capacitor are carried by the surface of the plates.
There is no requirement that these plates be thick to ensure mechanical
strength or current carrying capability provided the solid dielectric mater-
ial (1) supports the plates and maintains close, constant spacing between the
plates and (2) prevents short circuits. The normal construction of ac capa-
citors uses alternating layers of aluminum foil and special kraft paper
tightly wound on a mandrel. This core is then vacuum impregnated with a
dielectric liquid and sealed into a metal can. Where the voltage stress is
expected to be high, as in high voltage power factor capacitors, plastic
film or bi-layer plastic film/kraft paper solid dielectric materials may be
used.
The production of satisfactory A.C. capacitors depends on careful
control of the design and of the material properties. Many different com-
binations of plate spacing and solid and liquid material properties' are
available. Optimum capacitor design depends on careful engineering backed
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by the data fron extensive long-term performance tests. Since the service
life of the capacitors will depend on the slow degradation of the dielectric
materials, long-term testing is necessary to determine the most appropriate
material combinations, voltage stress, temperature, and manufacturing pro-
cesses.
5.2 Uses of Electrical Capacitors in Alternating Current Circuits
If a voltage is applied across a device that generates a magnetic.
field, .such as a motor winding, energy is used to create the magnetic
field. This energy reappears as current when the voltage decreases and the
magnetic field collapses. In the case "of a winding energized by alternating
current, the alternating magnetic field opposes the applied voltage, so the
voltage drop across the device is proportional to the rate of change of
current. When the magnetic field is at a maximum, the opposing voltage is
also at a maximum, and the voltage drop across the device is at a maximum.
Therefore, the current flow is zero. As the voltage decreases, the magnetic
field collapses resulting in a current in the same direction as the voltage
drop, but lagging the voltage drop in time. Therefore, such a device results
in a shift in the time relationship between voltage and current opposite, to
that caused by a capacitor. This type of phase shift is caused by electric
currents induced by changing magnetic fields, and such equipment is called
inductive.
In an A.C. circuit that has a capacitor and an inductive device in
series, the current generated by a collapsing magnetic field occurs at the
same time that the electric field is being formed in the capacitor. When
the capacitor is discharging current, the magnetic field is increasing and is
taking energy from the circuit. Because of the difference in the direction
of phase shifts, energy is transferred back and forth between the magnetic
field in the magnetic .device and the electric field in the capacitor. If
. the phase shift caused by an inductive device is not compensated for by a
capacitor, the electric energy generated by the collapsing magnetic fields
will be transmitted back toward the generator and will be dissipated as
heat in the transmission lines.
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A.C. capacitors are widely used to compensate for the phase shifts
caused by magnetic devices. PCBs have been used as dielectric liquids in
these capacitors since the 1930's. A.C. capacitors containing PCBs usually
have a very low failure rates; the rate depends on the particular design
and use/ but id is usually no more than one or two percent per year. Be-
cause of this low failure rate, most of the PCS capacitors manufactured are
still in service. The present location of these capacitors depends on their
particular design and use.
5.2.1 High Voltage Power Factor Capacitors
The normal loads imposed on utility distribution systems
are a combination of resistive (resistance heating, lighting) and partially
corrected inductive loads. As a result, the current lags voltage. This
condition results in excessive transmission losses and lowered efficiency
unless the phase relationship is corrected by installation of extra capa-
citors in the system near the inductive loads.
The power lost in transmission because of the resistance
in lines is proportional to the square of the current. However, the power
delivered to the user is equal to the voltage times the current. Transformers
are therefore used (1) to raise the generated power to high voltages (and
low amperages) for long distance distribution on high towers, and (2) bo
lower the voltage to intermediate levels at substations for local distribution,
and (3) to further lower the voltage to line voltages (110 volts to 660 volts)
near the site of its use.
Large high voltage power factor capacitors are installed
by the utilities on the intermediate voltage transmission lines to compen-
sate for the phase shifts caused by the use of the electricity. These ca-
pacitors operate at from 4800 to 13800 volts (occasionally at 2400 volts).
There is some heat generated in an operating capacitor, which must be
radiated or conducted from the surface of the unit. To prevent overheating,
-66-
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commercial power factor capacitors are limited to that size where heat loss
from the capacitor case will be adequate to prevent overheating. The
usual size of such capacitors may be 4" x 8" x 2' high, weighing 100 to 150
pounds including 3 gallons (30 Ib) of PCBs. These capacitors are usually
installed at substations in frames which hold a large number of identical
units. The capacitors are also often mounted at the top of distribution
poles.
There are presently four companies in the United States
that manufacture large high voltage power factor capacitors:
Westinghouse Electric Corp.
General Electric Go.
McGraw Edison Co.
Sangamo Electric Co.
Approximately ten million pounds of PCBs per year were used
in the manufacture of these large capacitors from 1972 to 1975. Total
production was probably on the order of 300,000 to 400,000 units per year,
and there are probably four to six million of these large high voltage power
factor capacitors currently in use. Most of these capacitors are owned by
utilities and are located in secure locations such as in substations and on
power poles.
The market for these large capacitors has been very compe-
titive. Although capacitors made by all of the manufacturers contained PCBs
prior to 1977, the capacitor designs were constantly modified in a contin-
uing effort to decrease manufacturing costs.
5.2.2 Industrial Capacitors
Capacitors made for various A.C. industrial applications have
in the past all been based on the use of aluminum foil, kraft paper, and
PCB liquid dielectric. This combination of materials has provided- good life
and excellent fire safety at low cost. Most of these capacitors are rated
at 330V, 370V, or 440 volts. The conditions under which these capacitors
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operate in various applications will affect the usability of proposed sub- .
stitutes for PCBs. Seme of the major types of industrial capacitors are as
follows:
Motor Run Capacitors: Capacitors are used in single phase
A.C. motors both to provide starting torque and to increase the electrical
efficiency of the motors by correcting the power factor of the equipment. In
a capacitor run motor, the windings are connected as shown below:
PSIMiSY w:M!NG
SCTCR
SECONOASY WINDING
Capacitor
The effect of the capacitor in series with the secondary winding is to shift
the phase relationship of the voltage and current through this winding so
that the magnetic fields in the primary and secondary windings are out of
phase by approximately 90 degrees. As a result, the stator "sees" an
essentially rotating magnetic field that causes a high starting torque.
Because of the inductive effect of the starting winding, the voltage in this
leg of the circuit is substantially above the line voltage. Most motors are
designed so that the capacitor operates at an effective applied voltage of
370 volts A.C.
The motor run capacitor also provides significant power
factor correction, thereby increasing the efficiency of the motor. Small
A.C. motors, such as those used in refrigerators and small fans, do not reouire
a high starting torque and do not presently have capacitors. However,
regulations promulgated by the Department of Energy which establish goals of
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Improved efficiency of appliances are expected to greatly increase the
demand for small motor run capacitors over the next few years,
Ballast Capac'itOYs: Most fluorescent lights and high
intensity discharge (mercury and sodium vapor) lights operate on 110 volt
circuits. However, a voltage of at least 300 volts across the buUbs is
required to produce a sufficient flow of current to operate them. This
high voltage is produced by a ballast transformer (in the case of fluorescent
lights, an autotransformer). Control of the current is important, because
the bulbs have a high resistance when first started, and this resistance drops
as the bulbs are heated.
Most small fluorescent lights do not have ballast capacitors.
These include the 15 watt and 20 watt single tube household fixtures. The
ballasts of dual - 40 watt fluorescent fixtures and larger fluorescent and
high intensity discharge lamps have ballast capacitors in series with the
transformer and bulb to limit the current flow and correct the power factor
of the fixture. For instance, the small fixtures have a power factor of about
0.7; the larger units with ballast capacitors operate at a power factor of
0.9 or above.
The standard ballast used in fluorescent light fixtures with
dual 40 watt or single 80 watt bulbs consists of a small 4 uf capacitor and
an autotransformer which are both encased in a steel can and potted in a
mixture of asphalt and sand. The capacitor is of the usual foil-paper-liquid
dielectric construction which is sealed in a metal can before being assembled
into the ballast.
Ballasts for high intensity lighting fixutres also consist
of a transformer and one or more capacitors which are usually mounted as
separate components rather than being permanently sealed into a ballast
container. Standard highway HID fixtures often use two capacitors, each
being about 2" x 4" x 6". In explosion-proof HID fixtures, the light, trans-
"former, and capacitors are hermetically sealed into an explosion proof hous-
ing. The temperature of the capacitors may exceed 90° C in these fixtures
because of the poor heat transfer characteristics of the fixture.
-69-
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Appliance capacitors: Snail capacitors are widely used in
microwave ovens as part of the high frequency generating circuits and in sane
television sets in the circuit that compensates for fluctuating line voltage.
Surge capacitors: The circuit breakers (switches) used on
large inductive machines must be protected from excessive arcing across the
terminals. If an inductive device such as a transformer or motor is dis-
connected while the coils are energized, the magnetic field will collapse and
the energy will appear as an electric field in the lines between the device
and the circuit breaker. These lines will act as a capacitor, the energy
being proportional to the capacitance and the square of the voltage. Since
the capacitance of the connecting lines is quite small, several thousand volts
may appear as a transient which will cause arcing across the terminals. The
addition of a surge capacitor on the machine side of the circuit breaker
increases the capacitance, thereby reducing the maximum transient voltage and
protecting the circuit breaker.
Industrial capacitors: A.C. capacitors are also used in surge
protection for silicon controlled rectifiers; in the power supplies of arc
welders and induction furnaces; and in business machines, electronic controls,
and similar electronic equipment.
5.3 Desired Properties for Capacitor Dielectric Liquids
The primary dielectric in the A.C. industrial capacitors is the solid
dielectric which maintains a constant distance between the aluminum foil
plates. The purpose of the liquid is to displace air, thereby raising the
corona inception voltage of the device and the maximum operating voltage of
the capacitor. The liquid also absorbs any gases that are formed and flows
to fill any bubbles that may result from minor arcing; this makes the capa-
citor self-healing. It is important that the chemical, physical, and elec-
trical properties of the ligind be compatible with those of the other mate-
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rials and with the way the capacitor will be inanufactured and used. Important
liquid properties include:
Electrical properties:
Dielectric Constant: Should be close to that of the solid
dielectric (6.15 for paper; 2.2 for polypropylene).
Loss Tangent (dissipation factor): As low as possible to
minimize dielectric heating of the capacitor which
wastes energy and shortens the life of the device.
Resistivity:- As high as possible initially, and remaining
high after extended use to minimize resistance
heating.
Dielectric Strength: As high as possible to prevent arcing.
Corona Inception Voltage: As high as possible/ to allow
the capacitor to be built with minimum plate spacing
and high electric field strengths. High corona
inception voltage will also minimize corona at the
edges of the foil and at other rough or sharp areas.
Corona Extinction Voltage: As close to the corona inception
voltage as possible to minimize the length of time
that corona discharge will occur during each voltage
cycle.
Physical Properties:
Viscosity: Capacitors are impregnated with liquid by placing
them in a vacuum chamber, evacuating the air, and
flooding the chamber with liquid that soaks into
the pores of the solid dielectric by capillary
attraction. It is important that the viscosity
of the liquid be sufficiently low to allow it to
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flow into the capacitor at a temperature where the
vapor pressure of the liquid is also low. The
liquid must also wet the solid dielectric, since
high interf acial energy will prevent through im-
pregnation.
Freezing Point: The liquid must have a freezing point be-
low the minimum temperature anticipated in storage
or use; freezing would result in expansion which
might distort the capacitor windings or container
causing a short circuit and failure of the device.
Boiling Point: The liquid must not boil at the maximum
expected operating temperature, and must have a
maximum vapor pressure during operation sufficiently
low to prevent distortion of the metal container.
Chemical Properties:
Stability: The liquid must be sufficiently stable to resist
the degradation caused by extended use at high
temperatures in an intense electric field and in
the presence of corona discharges and active metal
surfaces.
Solvency: The liquid must not cause excessive swelling of
the solid dielectric.
Corrosiveness: The liquid must not react with any of the
metal or non-metallic materials in the capacitor.
Toxicity:
Acute Toxicity: The liquid must have a low level of acute
toxicity both for skin contact and inhalation.
Contact of the liquid with humans must be expected
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during both the manufacturing of capacitors and
due to accidental damage of the units in use.
Chronic Toxicity: The liquid must not exhibit mutagenic,
teratogenic, or carcinogenic activity. Low levels
of exposure over long periods of time would be
expected in the capacitor manufacturing plants
unless new and expensive totally enclosed manu-
facturing equipment were installed.
Environmental Stability; The liquid will probably enter the
environment because of accidental damage of capa-
citors, rupture of capacitors upon failure or dur-
ing material reclamation processing, or leaching
frcm landfills used to dispose of failed or obsolete
capacitors. Susceptibility to environmental degra-
dation or biodegradation is usually not conpatible
with the high degree of chemical stability required
to ensure successful long-term performance of the
capacitor. Bswever, if the chemical is not at
least slightly degradable, it will eventually
accumulate to significant levels in the environment
as PCBs have done.
Bioaccumulation: Although low levels of any capacitor liquid
may eventually be expected in the environment, sig-
nificant health risks would probably only result
frcm an active accunn.ilat.ion of the chemical in the
food chain as has occurred with PCBs. A low tend-
ency to bioaccumulate, as measured by a low
octanol/water partition coefficient, would decrease
the potential risk frcm this exposure mechanism.
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5.4 Use of PCBs in capacitors
PCBs have been used in A.C. capacitors since the early 1930s.
Prior to the availability of PCBs, this type of capacitor used mineral oil
as a dielectric liquid. PCBs were considerably more expensive than mineral
oil per gallon of liquid, but they could be used in a capacitor about half
the size of a mineral oil capacitor of equivalent capacitance. Their use,
therefore, resulted in much longer service life and inherent fire safety. '•
• The use of PCBs in the manufacture of capacitors gradually decreased
from 30 mi 1 ] inn pounds per year in 1965 to about 20 million pounds per year
(29)
in 1975. ' This decrease was the result of both improved capacitor desiqns
which required less liquid dielectric and a maturing of the market for power
factor correction capacitors. The demand was expected to increase considerably
between 1975 and the early 1980s because of requirements of the Department of
Energy for improved efficiency of electrical appliances.
In Section 6(e) of the Toxic Substances Control Act, Congress man-
dated an end to the use of PCBs in the manufacture of capacitors by January 1,
1979. In a separate regulatory action, the Environmental Protection Agency
banned the discharge of PCBs to waterways by capacitor manufacturers after
February 1, 1978, under the authority of the Federal Water Pollution Control
Act (33 U.S.C. 1251 et. aeqJ. *30) The effect of this effluent standard
was to encourage the early conversion of capacitor manufacturing to the. use .
of non-PCB substitute liquid dielectrics. Since different types of capacitors
have different performance requirements, it is perhaps not surprising that
the various segments of the capacitor industry have had differing degrees of
success in cxxmercializing non-PCB capacitors within the tight deadlines man-
dated by the Federal statuatory and regulatory actions.
(29) Versar, Inc., PCBs in the United States: Industrial Use and Environmental
DJstrJbution, Springfield, Vail Ngti*?n^l Technical Information Service
(OTIS No. PB 252 012), February 25, 1976. p. 214.
(30) Environmental Protection Agency, "Proposed Toxic Pollutant Effluent
Standards for"Pblychlbrjhated Biphenyls (PCBs), Final Decision,"
Federal Eegister, Vol. 42, pp. 6531-6555 (February 2, 1977).
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5.4.1 Power Factor Capacitors
There are four U.S. manufacturers of large high voltage
power factor correction capacitors. All four of these companies discontinued
using PCBs in this type of capacitor by mid 1977 and essentially eliminated
inventories of PCS units by the end of 1977. The non-PCB capacitors now
offered by these companies all perform the same electrical function, but they
are constructed of different materials as is shown in Table 5.4.1-1.
TABLE 5.4.1-1
NCN-PCB POWER FACTOR CORRECTION CAPACITORS
Manufacturer Solid Dielectric Liquid Dielectric
Westinghouse Paper and plastic film Isopropyl biphenyl
combination
Sangamo Electric Co. " Phthalate ester**
General Electric " Phthalate ester**
General Electric Plastic film Phenyl Xylylethane
McGraw Edison Plastic film Butylated monc-
chlorcdiphenyl ether
. * All of the liquid dielectric materials contain small amounts of additives
as free radical scavengers, etc. The identity of these minor constituents
is proprietary information.
** The phthalate ester based liquids reportedly contain a significant amount
of trichlorobenzene as an additive to raise the corona extinction voltage.
f
5.4.2 Other Small and low Voltage Capacitors
The development of marketable non-PCB small capacitors has
been more difficult than the development of power factor capacitors for several
reasons. Each of the different applications of small capacitors requires
special performance characteristics which can be proved only by long-term
testing.
-75-
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Problems resulting fron fire safety and product liability
are more difficult with the small capacitors than with the large high voltage
capacitors. Power factor capacitors are sold to the users (primarily utilities)
directly by the manufacturers, so responsibility for product guarantees is
clear cut. • There would be little additional service cost to replace a failed
power factor capacitor, and there is little fire hazard if a power factor
capacitor should fail since most of them are located out of doors in substations
or mounted on distribution poles. The small capacitors are sold as components
of lighting fixtures, electrical appliances, and industrial machinery. Failure
of a capacitor results in warranty claims on the manufacturer of the equipment
although he may be several steps removed from the manufacturer of the capacitor.
For this reason, the customers of the capacitor manufacturers are hesitant to
use any new or modified type of capacitor until its satisfactory performance
has been demonstrated by considerable testing. An additional problem .is that
many of the small capacitors are used in applications where rupture of the
capacitor case following failure of the capacitor could lead to significant
fire hazards.
Much of the equipment using small capacitors must be approved
by Underwriters laboratories or other national testing organizations to be
commercially successful. Underwriters Labs, which is the acknowledged leader
in establishing safety criteria for appliances, is requiring that non-PCB
capacitors used in lighting ballasts be protected by a pressure sensitive or
thermally activated circuit breaker to prevent case rupture and decrease the
risk of fire.
Non-PCB small capacitors have been developed by the manu-
facturers who previously manufactured PCS units. These companies now have
established non-PCB products for most of the applications where they previously
offered PCS capacitors.
5.5 Alternatives to PCS Capacitors
PCS capacitors will not be available after mid 1979 unless
EPA grants exemptions from, the bans on processing and distribution in coanserce
of PCBs that are specified in section 6 (e) of the Toxic Substances Control
-76-
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Act. Therefore, replacement devices must be developed to perform the function
of PCS capacitors in the future. Possible alternatives include increased use
of synchronous condensers for power factor correction, the development of
satisfactory dry capacitors, and the use of other dielectric liquids as
replacement for PCBs in liquid-filled capacitors. The feasibility and
economic attractiveness of each of these alternatives depends on the particu-
lar performance requirements of the various types of capacitors in which PCBs
have been used.
5.5.1 Synchronous Condensers
Most electric motors depend on current induced in the rotor
by the rotating magnetic field from, the stator to provide the coupling mag-
*
netic field. Synchronous motors have the rotor winding separately energized
by D.C. current through a comiutator on the shaft. Therefore, the synchoronous
motors are not pure inductive devices, and their apparent power factor can be
adjusted by controlling the relative currents in the stator and rotor windings.
If the current to the stator results in an exact balance of magnetic field
strength, no current is induced from the stator windings and the motor runs
at a power factor of unity. If the stator is over energized, the motor oper-
ates at a leading power factor and will perform an electrical function similar
to that of a power factor capacitor.
Synchronous motors are more expensive than induction motors
and require more maintenance to ensure proper adjustment of the commutator
brushes. Synchronous motors provide the advantage of constant speed under
varying loads, and are therefore used where close speed control is required as
with drag lines used in open pit mining. Mines using equipment powered by
this type of motor often depend on the motors to provide overall power factor
correction for the installation and therefore do not use power factor correction
capacitors.
The phase relationship in a synchronous motor depends only on
the relative magnitude of the rotor and stator currents. An unloaded syn-
chronous motor is capable of acting as an adjustable power factor capacitor,
the adjustment being provided by control of the current to the rotor. If the
-77-
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machine is used solely for purposes of power factor correction, a shaft
extension is not necessary; • such a machine is known as a synchronous con-
denser. ' ...
The major advantage offered by synchronous condensers is
that they provide completely adjustable power factor correction. In most
distribution applications/ the inductive load varies throughout the day as
the amount of current demanded changes. Banks of power factor capacitors can
provide partially responsive power factor correction if groups of capacitors
are switched into and out of the circuit in response to changing requirements.
However, this response will be by steps of capacitance; a synchronous condenser
could provide an exact match to varying requirements. This advantage of
synchronous condensers is offset by their higher maintenance requirements,
higher noise levels, and much higher price. Installed cost of capacitors
banks may run four dollars per KVAR, compared to an installed cost of twenty-
four dollars per KVAR for synchronous condensers. Synchronous condensers
are only used in those applications where their responsiveness to varying
conditions justifies their higher cost. However, they can be used in place of
power factor correction capacitors in almost all applications, and therefore
provide a real, if expensive, alternative to the use of banks of power factor
capacitors in electrical distribution systems.
5.5.2 Dry film capacitors
A major function of liquid dielectrics used in capacitors
is to increase the corona resistance at points of high voltage stress such
as the edge of the metal film and at rough spots and holes in the film.
A liquid dielectric is not required if the capacitor is operated at a voltage
below the corona discharge voltage of air. The corona discharge voltage of
a dry capacitor depends both on the inherent breakdown strength of the gas
' (about 300 volts for air around sharp edges) and on the design of the
capacitor, since voltage stress is a function of both the applied voltage and
the sharpness of the edge or discontinuity.
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The capacitors used with lighting fixtures and appliances in
Europe and Japan have traditionally been dry film units that have not used
a liquid dielectric. These capacitors have been installed so as to operate
at the normal line voltage of 220 volts, which is below the voltage at which
corona discharges would occur in air. To achieve equal capacitance at the
normal U.S. line voltage of 110 volts would require a capacitor four times
the size of that required at 220 volts. Therefore, it has been carmen prac-
tice in the U.S. to install the capacitors so that they operate in series with
the ballast transformer or motor secondary windings and are subjected to the
voltage of 330 to 500 volts usually developed at this point in the circuit.
Some capacitors in high intensity lighting fixtures operate at voltages exceed-
ing 1000 volts, although the fixtures operate at a line voltage of 110 volts.
Successful use of dry capacitors in the U.S. would require
either that the electrical circuits be redesigned to lower the voltage applied
to the capacitors or that the capacitors themselves be carefully designed to
eliminate areas of high voltage stress. The better the design of the capacitor,
of course, the higher the allowed voltage, so dry film capacitors might be
developed to meet the requirements of some of the applications presently
handled by liquid filled capacitors, even if the corona problem were never
solved for the high voltage applications.
The most promising technology presently being developed for
dry capacitors is the metalized film capacitor. In this design, the conduct-
ing plate is an extremely thin film of aluminum that has been applied to the
surfaces of thin polypropylene film by vapor deposition. Polypropylene is
used because it has lower dielectric losses than other thermoplastic materials.
The metallized film is then thightly wound on a mandrell to exclude as much
air as possible from the windings. Properly constructed small metalized
film capacitors have reportedly operated successfully at voltages exceeding
300 volts. H3wever, the construction of these capacitors requires different
equipment than does the manufacture of paper/foil capacitors because of the
need for a permanent core and the closer control required during the winding
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operation. Acceptance of metalized film capacitors for the lower voltage
appliance applications is now more a matter of economics and industry
practice than of unsolved scientific problems. Dry film capacitors would
not be expected to take a significant portion of the market unless they
were cheaper than liquid-filled units for the same applications, and there
is apparently not yet sufficient difference in the potential costs of the
two types of capacitors to justify the new equipment and the marketing effort
required to successfully sell them.
5.5.3 Conventional Capacitors Using Non-PCB Liquid Dielectrics
The Toxic Substances Control Act established a deadline for
ending the manufacture of FCBs, and consequently, the capacitor manufacturers
were faced with the immediate need to develop acceptable substitutes for
their entire lines of PCS capacitors within a period of one to two years.
General electric already had experience in using phthalate esters as a replace-
ment for PCBs in capacitors manufactured for export to Sweden and Japan where
the importation of PCBs was banned in the early 1970's. Substitutes for PCBs
had .been fairly well developed in Japan in the four or five years after the
government banned the use of PCBs, and it was therefore apparent that non-PCB
capacitors could be built without major changes in manufacturing technology
or equipment by using suitable substitute liquid dielectrics. The substitute
materials presently being used all have lower dielectric constants than PCBs,
so the non-PCB capacitors are all somewhat larger than the PCS units they
replace. In addition, the non-PCB liquids are all more flammable than PCBs,
so additional features have been necessary to protect against rupture and fire
of failed non-PCB units used in appliances and other inherently hazardous
applications.
Although many different liquids have been used in capacitors,
including castor oil and mineral oil, there are only a few chenicals that
have sufficient chemical stability and suitable electrical properties to be
used successfully in capacitors as a direct substitute for PCBs. The electri-
cal and physical properties of PCBs and several of the more premising sub-
stitute materials are summarized in Table 5.3.3—1.
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00
TADU3 5.5.3-1
Properties of Cnpacitor Dielectrio
Dutylated
d tan Leal
Electrical Properties
Dielectric Constant
Dielectric Strength
Dissipation Factor
Resistivity ulni-aa
Physical Properties
Specific Gravity
Viscosity
four Point
Surface Tension
nls(2-ethylliexyl)
Phthalate
5.33
28 KV
.14
2 x 10"
0.99
Bl cps (20°C)
-50°C
Diisononyl
Phthalate
4.66
30 KV
.05
3 x 10' *
95 cps
(20°C)
-48°C
Expansion Coefficient
Flaslipoint
Firepoint
218°C
246°C
221°C
257°C
Manochlorodiphenyl-
Ethor*
4.4 to 4.8 (20°C)
3.2 to 3.4 (85°C)
45 KV
.04 max
34 x 10'* (26°C)
1.09
10.5 cs (30°C)
14 cs (25°C)
<-45°C
40 dynes/on
7.4 x loT1' cc/cc/'C
174-C
199°C
Isopropyl niptienyl Phenyl XylyleUiano
*t ***
2.83 (25°C) 2.6 (25°C)
45 KV 60 KV
.002
1 x 10" 1.0 x 101*
i i
0.90fl (25"C) 0.9U8
4.9CS (3fl°C) 6.5 cs (30°C)
20CS (25°C)
-51aC -47.5
140°C 155°C
165°C WO'C
pen
(Aroclor 1016)
5.85 (25°C)
4.85 (100°C)
35 KV
.0025
5 x 10"
1.362
71 to Bl SlIS (100°F)
-19°C
6.8 x 10~% cc/C3t:/°C
141°C
None
Onrrosivity
• Noit-corrosivo
-------
Clianical
TABUS 5.5.3-1 (Oont'd)
Properties of Capacitor Dielectric Liquids
Dutylated
Ills (2-e thy Ihexyl) Diisononyl Monochlorodlphenyl- Isopropyl Biphenyl
Pt it ha late Phtlialate ' Ether* **
Phcnyl Xylylethane
***
pen
(Aroclor 1016)
I
CD
10
Toxicity
Acutes
Oral
Dormal
Inhalation
Chronici
Mutacjenicity
Teratocjen ici ty
nioaocnmulatiom
Excretion Rate:
LD50: >128gAg
(Kbuse)
LD50: 31gAg
(rats)
(rat)
Yea (rats)
1/500 tinea POte
>10 g/kg. (rats)-
Mo effect (rabbits,
guinea pigs)
No effect (rats)
U)50z B.SgAo (ratfl) u>50: 1.7 or 2.3 gAg
(rats)
Slight"irritation
(rabbits) , ,
Slight effect
(920 pun, rats)
>5
tto effect (Anes test) No effect
(Ames test)
No effect (Rat, Rabbits)
1/22 times PCD
50% in 11 hours (inonkey
and rats)
No effect (Ames test)
Ho effect (mice, rats)
<.l value for PCD
Yes
Yes
*Gimerclal mixture of mocio-, di-, and tri soc butyl derivatives manufactured by Dow ClMiilcaT Oo.
**Cumercial mixture of 95% mono- and 5% di- and tri- isopropyl bl|4K>nyl tradaiwirked Suresol 2^0 ai»1 manufactured by 5
Petroleum Piotlucta Oo.
***Nis.'jel;i Comlonser Oils or Nlssekl Ilisol SAS manufactured by Nippon Petrochemicals.
-------
The impregnation of a capacitor with a liquid dielectric requires that
the air be removed fay establishing a vacuum and that the solid dielectric wick
the liquid into the windings of the capacitor. Polypropylene cannot be used as
a direct replacement for the kraft paper used as the solid dielectric/spacer in
conventional small capacitors because it is solid and therefore does not act as
a wicking agent and because it is not wetted by most liquids. Development of a
completely new technology may eventually allow use of synthetic dielectric
materials in small film/foil capacitors. Sandia Laboratories has demonstrated the
feasibility of a metalized film capacitor using a perfluorcalkane liquid (at
$200 per gallon) as the dielectric liquid. Large high voltage power factor
capacitors using all film (polypropylene) construction are presently being manu-
factured by McGraw Edison and by General Electric. The McGraw Edison units use
aikylated monochloro biphenyl ether as the liquid dielectric. The General
Electric all-film capacitors use 1,1-phenyl xylylethane as the liquid dielectric
The present state of technology in the production of commercial
capacitors is based mainly on the methods used to produce PCB capacitors. The
following sections discuss the chemicals that are presently finding wide use as
substitutes for PCBs in the U.S., or that are being considered for use in this
application. Most capacitor manufacturers also add small amounts of additives .
to the liquid which act as antioxidants/ corona suppressants, etc. These other
chemicals are usually present in concentrations of no more than a few tenths of
one percent.
5.5.3.1 Alkyl Phthalates
_ AUcyl phthalates, such as bis (2-ethylhexyl) phthalate and diisononyl
phthalate, are being used as the basis for the dielectric liquid in all small
capacitors that previously used PCBs and in some of the large power factor
capacitors ttiat have been manufactured by Sangaroo and General Electric.
Total U.S. production of phthalate esters was 382/501 metric
tons in 1976. Over 95% of the phthalate esters are used as plasticizers,
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particularly in polyvinyl chloride resins in which the phthalate ester may
account for up to 40% of the weight of the material. Stanford Research
Institute estimated that over 53,000 metric tons of phthalates were used as
plasticizers for plastics in electrical equipment in 1976. A major electri-
cal use of phthalates is as a plasticizer in vinyl resins used as wire and
insulation.
Approximately 30 different phthalate esters are manufactured
in the United States. The material produced in the greatest amount is
bis (2-ethylhexyl) phthalate/ comprising 35% of the 1976 production. This
material is produced at nine different plants in the U.S.
• The phthalate esters are noted for their low acute toxicity.
Although laboratory tests have demonstrated that bis (2-ethylnexyl) phthalate
is teratogenic and mutagenic in mammals at high dosages, the relevance of
chronic biological effects at low dose rates has not been assessed.
In rats, teratogenic effects of bis (2-ethylhexyl) phthalate include fetal re-
sorptions, gross abnormalities, and decreased fetal weights. Effects on mice
include a pronounced decrease in fertility, an increase in early fetal deaths,
and reduced numbers of fetal implants.
The only substantiated health effects caused by long-term work place
exposure to phthalate esters have been occasional cases of mild skin irritation.
Industrial workers exposed to phthalate vapors or aerosols at ambient levels of
10 to 66 mg/fa were observed by Milkov. * ' Duration of occupational exposure
ranged from. 6 months to 19 years. The most frequent complaint by the workers
was pain in the upper and lower extremities, accompanied by numbness and spasms.
Studies of the nervous system revealed polyneuritis increased with length of the
(30) flurhian, John, "Toxicity and Eiealth Threats of Phthalate Esters: Review of
the Literature11 Environmental Health Perspectives, June 1973, pp. 3-26.
(31) Environmental Protection Agency. Criteria and Standards Division.
Draft Water 0*^1 jty Criteria Docunent for Phthalate Esters. March 2, 1978.
(32) Milkov, L.E., et. al. "The status of health of workers subjected to the
effects of phthalate plagf-i rripgrg in the production of &etifTaiai lea-
ther and film (with PVC base) " [translated title! Gig. Tr. Prof. Zabol.
13, 14 (1969) as cited in: Peakall, David B. "Phthalate Esters: Occurrence
and biological effects, * Residue Reviews Vol. 54 (p. 1) 1975.
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employee's service. Functional disturbance of the nervous system was noted in
fifteen percent of the workers. However, these workers were also exposed
to vapors fron phosphate ester plasticizers and to vinyl chloride. Both of
these chemicals are known to produce the health effects noted in the workers,
so this study does not prove that phthalates' are toxic.
The phthalates may enter the environment by slowly leaching or
volatilizing from plastic resins and by direct discharges by manufacturers and
users. Because the phtiialates have low solubility in water and high solubility
in fat/ 'environmental levels of phthalates will bioaccumulate in fish and
.manuals. Bis(2-ethylhexyl)phtfialate has been found to bioaccurnulate in fathead
(34)
minnows to concentrations 115 to 886 times the concentration in water.
Phthalates are known contaminants in both drinking water and food (33, pp. 19,
20; 35). However, the amounts of phthalates present in food have not been
found to be toxicologically significant. Although the phthalates are stable
in their industrial uses, they have been shown to be biodegradable in soil and
(37)
water. Phthalate esters are listed as toxic pollutants under section 307(a)
of the Clean Water Act, and the Interagency Toxic Substances Testing Cormittee
has recommended additional environmental effects testing for phthalates.
Diisononyl phthalate has been promoted as a liquid dielectric pri-
(38)
marily by Exxon Chemical Co. under the tradenarne ENJ-2065. As noted in
Table 5.5.3-1, this liquid has a lower dielectric constant than bis (2-ethylhexyl)
phthalate, but it also has a significantly lower loss factor, and a higher
dielectric strength.
(33) Environmental Protection Agency. Criteria and Standards Division. Draft
Water Quality Criteria Document for Pfrtfialate Esters. March 2, 1378.
(34) Mehrle, P.M. and F.L. Mayer. 1976. Di-2-ethylhexyl Phthalate; Residue
Dynamics and Biological Effects in Rainbow Trout and Fathead Minnows.
Colurrbla, Missouri: Fish and Pesticide Research Laboratory.
(351 Environmental Protection Agency. 1975. Preliminary Assessment of Sus-
. pected Carcinogens in Drinking Water. EPA/560/4-75-003, p. 9.
(36) Pftnd afid m-ng aAniryig+ya-Hnn. 1Q7A. Compliance Program Evaluation,
FY 1973 Phthalate Esters in Fish Survey (7308.OTA). Washington, D.C.:
Bureau of Foods, Food and Drug Administration, Nov. 15.
(37). Englehardt, G.; P.R. Wallnofer; and 0. Hutzinger. 1975. "The Micrcbial
" Metabolism of Di-n-butyl Phthalate and Related Dialkyl Phthalates,"
Bulletin of Environmental Contamination and Toxicology, Vol. 13, pp. 342-347.
(38) Inchalik, E.J. (Exxon Chemical Co.) "ENJ-2065-An Electrical Insulating
Fluid" in Conference Proceedings, National Conference on Polychlorinated
Birhenvls (EPA-560/6-75-004), March 1976. pp. 334-337.
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The particular chemical composition of dielectric liquid used in
capacitors is kept a trade secret by each company/ so the total consumption
of each of the different types is not known. However, it is likely that most
of the material used is either bis(2-ethylhexyl)phthalate or diisononyl phthalate.
It is known that General Electric affis a substantial quantity of chlorinated
benzene to the phthalate ester in their Dielektrol-H high voltage power factor
capacitors to increase the corona, resistance of the liquid. Sangamo Electric
reportedly uses a similar mixture in the power factor capacitors that they
manufacture.
Total consumption of PCBs by the capacitor manufacturing industry
never exceeded 20 million pounds per'year of which 55% was used in small capac-
itors and 45% in power factor capacitors. Although the non-PCB capacitors
v
are larger than the equivalent PCS units because of the lower dielectric con-
stants of the substitute materials, the phthalate esters weigh less per gallon
than do PCBs, so the total weight used is probably the same or less for the
substitutes than for PCBs. Even if the consumption of phthalates as capacitor
dielectric liquids were to total 20 million pounds per year, this would be a
small fraction of the total production of this type of chemical and would still
be less than 20% of the amount used as a plasticizer in wire and cable insula-
tion. Since the capacitor liquids are totally sealed in metal cans, there is
no chance for leaching or volatilization to occur while the units remain intact.
Therefore, the amount of phthalates introduced into the environment frcm capaci-
tors would be expected to be a small fraction of the amount lost to the environ-
ment from other electrical uses, and a negligible fraction of the total amount
dispersed ftTw piafifrif -ipoy applications.
5.5.3.2 Isopropylbiphenyl
Isopropylbiphenyl is presently being used by Westinghouse as a
dielectric liquid in high voltage power factor capacitors. The solid dielectric
used in these 'capacitors is reportedly a composite of kraft paper and polypro-
pylene film. The liquid sold by Sun Petroleum Products Go. for use as a capaci-
tor dielectric has the trade name Suresol 250 and contains 95% mono- and 5%
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isopropylbiphenyl. A mixture of 75% mono- ard 25% di- and tri- isopropyl-
biphenyl is sold as Suresol 245 and is extensively used as the dye carrier in
carbonless copy paper, an application in which it replaced the previously used
PCBs in 1972.
Isopropylbiphenyl has a fairly low dielectric constant (2.5 at 25°C)
but has other attractive electrical properties including high dielectric
strength/ high resistivity, and low dissipation factor. The high voltage power
factor capacitors that use this liquid as the dielectric presumably are designed
to operate at higher voltage stress levels than are similar capacitors using
other liquids to take advantage of the high dielectric strength and thereby
achieve high capacitance without increasing the plate area and the size of the
unit.
The conmercial mixture used in capacitors has a low degree of acute
(39)
toxicity (14 day rat IDcr= 8.5 gAg body weight) and significant cumulative
(39)
properties. Isopropylbiphenyl is mildly to moderately irritating to the
skin. The material has been found not to be mutagenic as determined by the
Ames test. The material can be disposed of by. incineration and is rapidly
biodegraded by soil and water microorganisms.
5.5.3.3 Butylated Monochloro Diphenyl Ether
Dow Chemical Company markets a capacitor dielectric liquid which
consists of a mixture of monochlorcbiphenyl ethers of varying degrees of
butylation. The material consists mainly of mono-/ di-/ and tri-sec-
butyl derivatives. This material is used by McGraw Edison in film/foil high
voltage power factor (shunt) capacitors that are used by electrical utilities
in power distribution systems.. McGraw Edison refers to the material by the
(41)
trade name Edisol.N
(39) Volfldchenko, V.A.; E.R. Sadokha; and V.D. Yaremenko. 1973. "Toxicity of
Isopropyldiphenyl," Farmakol. Tcksikol, No. 8, Kiev, pp 183-4. (in Russian)
(40) Dew Dielectric Fluid"- C4, (Form 176-1347-78) Midland, MI: Dow Chemical
U.S.A., 1978.
(41) Lapp, John, (McGraw Edison Company), A New Dielectric Fluid for Power
Capacitors/ Bulletin No. 76045, Cannonsburg, Pa.: McGraw Edison Co.,
Octcber IS 76.
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Although polypropylene film has a lower dielectric constant than
kraft paper/ it also has a higher dielectric strength and lower loss factor than
paper and is available in thinner films. The liquid dielectric used in all-
film capacitors should have a dielectric constant close to that of tiie film,
and be able to wet the film without dissolving in it or causing excessive
swelling of the film. The liquid used by McGraw Edison has the proper physical
and electrical properties for successful performance in all-film high voltage
A.C. capacitors: dielectric constant = 3.2 at 80°C vs about 2.0 for polypropylene
film; solubility of polypropylene in liquid less than 60 ppm; contact angle of
fluid on polypropylene = 15° corpared to trichlorobiphenyl at 48°.
Dow Chemical Company has reported considerable health and environmental
on this material including:
Toxicity:
Manual -
Acute oral 10 g/kg rat
Dermal No effect rabbits, guinea pigs
Inhalation No effect rats (saturated air at 50°C)
Subchronic No effect 5 mg/kg/day, rats
Fish -
Subchronic Does not induce hepatic MPO enzymes in
trout(42)
Chronic Toxicity:
Mutagenic No effect nxLcrobial—Ames Test
Teratogenicity No effect rats and rabbits
BiodegradatLon:
45 times PCS rate
Bi.'Ogjg»7» TT17 a/tricin; . •
298 ± 70 ratio trout muscle to water
Excretion rate:
50% in 24 hours from trout
50% in 11 hours from monkeys and rats
(42) Addison, R.F., and F.C.P. Law. "Induction of Hepatic MFO Enzymes in
Trout Fed PCS, Seme Proposed PCS Replacements, and Belated Compounds,"
Abstracts of 18th Annual Meeting, Society of Toxicology, New Orleans,
March 11-15, 1379. Paper No. 365.
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The Dow Chemical dielectric fluid is chemically a mixture of aromatic
halo ethers. This class of chemical is listed as a toxic pollutant under
section 307 (a) of the Clean Water Act. Dow Chemical has petitioned EPA to
have this class of chemical removed from the list. EPA has recently published
(43)
a review of the available data as part of its response to this petition.
This material has a lower dielectric constant than the phthalate esters and
is more expensive than the phtfaalates. The use of this material is limited so
far to the large high voltage capacitors that use all film solid dielectrics.
It has not been used as a direct substitute for PCBs in conventional paper/foil
small capacitors.
5.5.3.4 1,1-Phenyl Xylylethane
Nippon Oil Co. has been inarbfacturing 1,1-phenyl xylylethane (PXE) in
Japan since 1972 as a substitute for PCBs in carbonless copy paper and in
(44)
capacitors. Production of PXE has been several thousand metric tons per year.
The material reportedly has a short biological half-life, is not very
accumulative, and is easily biodegradible. Use of PXE in Japan since 1972
(44)
has not resulted in any measurable levels of PXE in the environment. PXE
is sold in Japan under the trade names "Nisseki Hissol SAS" (solvent grade) and
"Nisseki Condenser Oil S" (capacitor grade) .
In December, 1978, General Electric announced the availability in the
U.S. of a new line of all- film/foil power factor capacitors which use PXE as
(46)
the major constituent of the dielectric liquid. The G.E. trademark for
(43) Environmental Protection Agency. "List of Toxic Pollutants: Petition
to Remove Aromatic Halcethers," Federal Register Vol. 44, No. 60
pp. 18279-83, March 27, 1979.
(44) " Sumino, K. 1977. "Mass Fragmentgraphic Determination of Diisopropyl
Napthalene and Phenyl Xylylethane, and the Environmental Contamination
from Them," Archives of Environmental Contamination and Toxicology:.
Vol. 6, pp. 365-369.
(45) Hasegawa, H; M. Sato; and H. Tsuruta. 1973. "Special Eeport on the
Effects of Human Health and Chronic Toxicity of PCB and Other Pollutants,
to Prevent the Pollution fron Them: Study on the Toxicity of Alternatives
for PCS," Science and Technology Agency of Japan, p. 139 (as cited in
Sumino 1977TI
(46) General Electric. 1978. Film/Foil Power Capacitors (GEA-10600 9/78
(10M)) Capacitor Products Department, General Electric, Hudson Falls,
N.Y.
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this dielectric liquid is Dielektrol HI. G.E. has apparently achieved complete
impregnation by the liquid through a process of treating the polypropylene
film to form a matted surface (trademarked Hazy film) and by embossing the
aluminum foil to provide channels for liquid movement. G.E. claims that this
new film/foil capacitor reduces electrical operating losses from 0.5 watts per
KVSR for the previously used paper/film/foiiyPCB design to less than 0.3 watts
per Ktf&R. In addition to reducing distribution losses and the resulting
demand on generating capacity, this reduction in operating losses means that
the capacitors will generate less heat and will operate at a lower temperatures,
thereby increasing their service life. G.E. also claims that this design of
capacitor will form a lower resistance short circuit when it fails than will a
paper/film/foil design capacitor. As a result, the circuit breaker will act
faster with the new design, reducing'the time for buildup of pressure within
the case and reducing the probability of case rupture.
5.5.3.5 Other Capacitor Dielectric Liquids:
Most of the recently reported research on the development of sub-
stitutes for PCBs has involved chemicals that could be added to isopropylbiphenyl
to increase its dielectric constant. Two types of chemicals described in
patents issued to Monsanto are ketones and diary 1 sulfones. One patent describes
the use of a liquid dielectric material consisting of 52.8% diroethylbenzo-
phenone, 46.9% isopropylbiphenyl^ and 0.3% 3,4-epoxycyclxihexylmethyl, 3,4-
epcoycyclxshexanecarbcKylate. Aluminum foil/paper capacitors impregnated with
this mixture reportedly had slightly higher lass factors and capacitance
ratings than similar control capacitors Impregnated with PCBs. The PCS capac-
(47)
itors failed after 188 hours at 1000 volts and 100°?, but the other did not.v '
U.S. patent describes a mixture of 10-30% tolyl xylyl sulfone, 70-90% isopro-
pylbiphenyl/ and 0.1-0.3% of the same stabilizer. The sulfones generally
(47) Munch, Ralph H. (Monsanto Co.) Dielectric Impregnating Agents for Capa-
. citors,- Ger. Offen, 2,452,213, May 7, 1975.
(48) Munch, Ralph H. (Monsanto Co.) Dielectric Composition for Impregnating
Electric Capacitors, U.S. Patent 3,948,788, April 6, 1976.
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are noted for high dielectric constants and fairly high loss factors; phenyl
xylvl sulf one has a dielectric constant of 29.0 at 25°C, and a loss factor
(49)
of 6.3%. Monsanto reportedly furnished sulf one based dielectric liquid
to several capacitor manufacturers under the trade name MCS-1238, and the
material performed well on test. However, Monsanto later decided against
commercial development of these materials because they could not be cost
competitive with phthalate ester based dielectric liquids.
Another chemical that is presently being marketed in the U.S. as a
possible capacitor dielectric liquid is benzyl neocaprate, which is produced
by Prodelec (France) under the trade name ENC. This material is essentially
a C,. acid that has been reacted with benzyl alcohol and has i±ie following
structure: •
This material reportedly has a dielectric constant of 3.2.
Other materials that have previously received serious consideration
as possible liquid dielectrics are chlorinated diphenylethers and 1,3,3 tri-
methyldichlor 1 phenyl indane. The physical and electrical properties of these
materials are summarized in Table 5.5.3.5-1.
(49) Clark, Frank M. Insulating Materials for Design and Engineering Practice,
New York: John Wiley & Sons, 2362, p. 395.
(50) Wood, David, "Chlorinated Biphenyl Dielectrics - Their Utility and
Potential Substitutes" in Conference Proceedings, National Conference
on Polychlorinated Biphenyls. EPA-560/6-/5-004, Marcn 13 Yb,
pp. 317-322.
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Table 5.5.3.5-1
Properties of Potenti^l Capacitor Dielectric Liquids.*
Electrical Properties
Dielectric Constant
Dielectric Strength
Dissipation Factor
Resistivity ohmr-on
Physical Properties
Specific Gravity
Viscosity
Pourpoint
Flashpoint
Firepoint
Corrosivity
Chlorinated
diphenyl ethers
inonochloro pentachloro
4.5 30°C 5.0 30°C
3.8 100°C 4.3 100°C
35 KV
35 K7
1.5 x 10": (30°C) 1 x 1012(30°C)
1,3/3 tri methyl
dichlor 1 phenyl inclane
6.0(0°C)
5.0 (120°C)
35-45 K7
<.001 (10 to 60°C)
<.01 (-10 to 120°C)
5 x 1013(40'°C)
1.18
36 (38°C)
-55°C
146°C
Neutral
1.53
390 (38°C)
0°C
None
Neutral
1.14
62SSU (93°C)
8°C
•;
1858C
250°C
Neutral
*Source: Clark/ Frank M. / Insulating Materials for Design and Engineering
Practice/ New York: John Wiley & Sons, 1962. pp. 205-208.
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PCBs were banned in Japan in 1972, and since then the Japanese manu-
facturers have used a number of different liquids in addition to EXE including
1,1-di (nxmochlorophenyl) ethane , alkyl naphthalene (trade name KMC) / silicone
oil (trade name KSK, manufactured by Kureha) , and an aromatic
material (trade name KES, iranufactured by Kureha) . None of these materials
have been used in the U.S. as a substitute for PCBs.
Capacitors designed for use at higher frequencies (i.e./ 1000 hz
and above) have traditionally used liquids other than PCBs. Both mineral oil
and castor oil are sometimes used in special applications. However/ the most
commonly used material is chlorinated naphthalene/ which is used in automobile
ignition capacitors.
Chlorinated naphthalenes are similar to PCBs in that they are avail-
able as mixtures with different degrees of chlorination and are noted for their
chemical stability and toxicity. The major use of chlorinated naphthalenes in
the U.S. is as an impregnant in automotive capacitors/ which use a mixture of
trichloro and tetrachloro naphthalenes. "This material is a solid at room tempera-
ture and has a melting point of 93 to U5°C/ depending on the particular mixture
that is used. The dielectric constant of the capacitor grade material is 4.1.
Chlorinated naphthalenes have not been used in the U.S. as a substitute for PCBs
in A.C. capacitors because of their high power factor at low frequencies (0.37
at 60 hz/ 100°C) / and because they are solids that can develop cracks while
in use, resulting in increased corona discharges.
It is unlikely that chlorinated naphthalenes will be used in A.C.
capacitors. The toxicity of this material is well documented, and the
monochloro naphthalene which could perhaps be used as the basis of a liquid
dielectric is presently listed by the EPA as a priority pollutant.
(51) Kover, Frank D., (Environmental Protection Agency), Environmental Hazard
Assessment Report; Chlorinated Naphthalenes, Springfield/ Va.: National
• "Technical Information Service (PB-248-834), December, 1975.
(52) Kcppers Co./ Inc. Halcwax Chlorinated Naphthalene Oils and Waxllke Solids,
(CM-203-770)/ Pittsburgh/ Pa.;
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6.0 CCNCHJSICNS
PCBs gained widespread use fron 1930 until 1978 because of their
chemical stability, attractive electrical properties, and availability in a
range of melting points and viscosities. It was the same properties of
chemical stability and low water solubility that resulted in their environ-
mental persistence and bioaccumulation.
The materials used as substitutes for PCBs are less stable chemically,
which results in increased fire risk but which also ensures that they are
less persistent in the environment. Because the use of PCBs sensitized the
users to problems of acute and chronic tcxicity,'the materials that have
been selected as substitutes for PCBs have notably low toxicity and well
defined environmental fates. The switch from PCBs to substitute materials
has required a certain degree of redesign of equipment in order to maintain
adequate fire safety while using more flammable liquids. However, the elec-
trical equipment manufacturers have developed non-PCB equipment that performs
adequately in almost every application where PCBs were previously used. The
banning of PCBs as a base for transformer askarel coolant liquids led to the
development of specifications for high fire point transformer liquids and the
increased use of various liquids meeting these specifications, including
natural and synthetic hydrocarbons and silicons oils. These same liquids are
suitable for use in electromagnets. In those applications where absolute
fire protection is required, dry air-cooled transformers and magnets are
now available, and engineering changes are,usually available that will allow
the safe use of less expensive oil-cooled units.
The development of adequate fire safety in small capacitors using
phthalate esters instead of PCBs required the development of circuit breaker
devices within the units that could sense either pressure or temperature
increases. The capacitor im'rwPf*ftf~iTTt?cs ai 1 managed to develop non—PCB
replacements for the major items in their product lines, and no major market
shifts have occurred. Of course it is still too early to state that the
transition away from PCBs was achieved without any problems, and indeed some
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problems in product life and performance might be expected to appear as
non-FCB capacitors remain in service for longer times. The previous change
in capacitor dielectric liquid occurred in 1972 when the industry switched
fron Aroclor 1242 (42% chlorine) to Aroclor 1016 (40% chlorine), and it was
several years before all of the performance problems were solved.
The switch from PCBs to substitute liquids has not been accomplished
without a great deal of effort by the manufacturers who have been faced with
a legislated cutoff date for PCBs. Money has been invested and risks taken
on product changes that were made on engineering judgement and that could not
wait for the results of long-term field testing. It is to the credit of the
electrical equipment manufacturers "that they have made this change with
apparent success.
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Addison, R.F. , and F.C.P. Law. "Induction of Hepatic MFO Enzymes in Trout
Fed PCS, Some Proposed PCS Replacements/ and Related Coipounds," Abstracts
of 18th Annual Meeting, Society of Toxicology, New Orleans, March 11-15,
1979, Paper No. 365.
Autian, John, "Toxicity and Health Threats of Phthalate Esters: Review of the
Literature" Environmental Health Perspectives, June 1973, pp. 3-26.
Brown, V.K.H. , "Acute ToscLcity and Skin Irritant Properties of 1,2,4-Trichloro-
benzene," Ann. Ocup. Hyg. 12:209, 1969.
Burrow, R.F. and T. Orbeck (Dow Corning) , Performance of Silicone Fluids as
Insulating Liquids for High-Voltage Transformers, Doble Engineering Client
Conference, Boston, Mass., April 22-24, 1974.
Calandra, J.C. et. al. , "Health and :Environmental Aspects of Polydimethyl-
siloxane Fluids," Polymer Preprints, 17(1), 12, April 1976.
Clark, Frank M. , ingiiaH'n.g Material g for Design and Engineering Practice,
New York: John Wiley & Sons, 1962.
•
Deaken, R.F.J. , and P.D. Smith, (Polygon Industries, Ltd), "Epoxy Insulation -
A New Generation of Dry-Type Transformers," Paper presented at the 64th
Annual Meeting of the Canadian Pulp and Paper Association, Montreal, Quebec,
January 31, 1978.
Dougherty, John J. , "R&D Status Report, Electrical Systems Division," EPRI
Journal, November 1977, p. 45.
Dow Corning Corporation (Midland, Mich.) , RetrofiTIIng with Dow Corning 561®
Silicone Transformer Liquid, October 19, 1976.
Dow Corning Corporation, Removal of PCS from Dow Corning® Transformer Liquid
by Charcoal Filtration, undated.
Dow Dielectric Fluid - C4, (Form 176-1347-78) Midland, MI: Dow Chemical U.S.A. ,
Edison Electric Institute, Report on Power Transformer Troubles , Publication
No. 71-20-1971.
Englehardt, .G.; P.R. Wallnofer, and 0. Hutzinger. 1975. "The Microbial
Metabolism of . D£~nr£utyl - Phthalate and Related JDialkyl Phthalates,"
of Environmental •Contamination and Toxicology, Vol. 13, pp. 342-347.
-96-
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Environmental Protection Agency, "Proposed Toxic Pollutant Effluent Standards
for Polychlorinated Biphenyls (PCBs), Final Decision," Federal Register, Vol. 42,
pp. 6531-6555 (February 2, 1977).
Environmental Protection Agency. Criteria and Standards Division. Draft Water
Quality Criteria Document for Phtnalate Esters. March 2, 1978.
Environmental Protection Agency. 1975. Preliminary Assessment of Suspected
Carcinogens in Drinking Water. EPA/560/4-75-003.
Environmental Protection Agency. "List of Toxic Pollutants: Petition to Remove
Aromatic Ha leathers," Federal Register, Vol. 44, No. 60, pp. 18279-83,
(March 27, 1979).
Fomenko, V.N., "Determination of the Maximum Permissible Concentrations of
Tetrachlorcbenzene in Water Basins," Hyg. Sanit. 30:8, 1965.
Foss, Stephen D., John B. Higgins, Donald L. Johnston, James M. McQuade,
(General Electric Company), BetrofiTling of Railroad Transformers, Report
No. DOT-JrSC-1293, July, 1978.
Frank, Jerry (Sorgel Electric Corp.) "Watch Out for Energy Losses in Trans-
formers," Electrical Construction and Maintenance, Aug. 1975, pp. 53,4.
General Electric. 1978. Film/Foil Power Capacitors (GEA-10600 9/78 (10M))
Capacitor Products Department, General Electric, Hudson Falls, N.Y.
Hasegawa, H; M. Sato; and H. Tsuruta. 1973. "Special Report on the Effects
on Human Health and Chronic ToxLcity of PCS and Other Pollutants, to Prevent
the Pollution from Them: Study on the ToxicLty of Alternatives for PCB,"
Science and Technology Agency of Japan, p. 139 (as cited in Sumino 1977).
Howard, P.H., P.R. Durkin and A. Hanchett, (Syracuse University Research Corp.),
Environmental Hazard Assessment of Liquid Siloxanes (Silicones), Washington
D.C.: Office of Toxic Substances, U.S.' Environmental Protection Agency
(Report No. EPA-560/2-75-004), September, 1975.
Hurley, J.S. and A. Torkelson, (General Electric Co.), "Silicons Dielectric
Fluids for Liquid Filled Transformers," TFPR paper C-74-264-8, Jan. 27, 1974.
Inchalik, E.J. (Exxon Chemical Co.) "ENJ-2065-An Electrical Insulating Fluid"
in Conference Proceedings, National Conference on Polychlorinated Biphenyls
(EPA-560/6-75-004), March 1976^pp. 334-337.
Jondorf, W.L., et. al., "Studies in Detoxification — The Metabolism, of Halo-
gencbenzenes. 1:3:3:4-, 1:2:3:5- and 1:2:4;5-Tetrachlorobenzenes." Biochem.
Jour. 69:181, 1958
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Hoppers Co., Inc. EfaTnwac Chlorinated Naphthalene Oils and Waxlika Solids,
(CM-203-770), Pittsburgh, Pa.: undated.
Kbver, Frank D., (Environnental Protection Agency), Environmental Ha?.ard
Assessment Report; Chlorinated Naphthalenes, Springfield, Va.: National
Technical Information Service (PB-248-834), December, 1975.
Lapp, John, (McGraw Edison Company), A New Dielectric Fluid for Power Capaci-
tors, Bulletin No. 76045, Carmonsburg, Pa.: McGraw Edison Co., October 1976.
Lazar, Irwin (The Eeyward-Robinson Co.), "Making the Choice Among Dry, Liquid,
and Gas Transformers," Specifying Engineer, June, 1977, pp. 92-96.
Mehrle, P.M. and F.L. Mayer. 1976. Di-2-ethylhexyl Phthalafce: Residue
Dynamics and Biologic?! Effects in Rainbow Trout and Fathead Minnows.
Columbia, Missouri: Fish and Pesticide Research Laboratory.
Milkov, L.E., et. al., "The Status of Health of Workers Subjected to the
Effects of Phthalate PlastLcizers in the Production of Artificial Leather and
Film (with PVC base)" [translated title] Gig. Tr. Prof. Zabol. 13, 14 (1969)
as Cited in: Peakall, David 5. "Phtiialate Esters: Occurrence arid" Biological
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iHBET
"EEST560/6-77-008"
Title and Subtitle Assessment of the Use of Selected Replacement
Fluids for PCBs in Electrical Equipment
5 Reflect Dace
March 1, 1979
7. Authors)
Itobert A. Westin
3. Performing Organizatir ''eat.
No. 474-5D
Performing Organization Name and Address
Versar Inc.
6621 Electronic Drive
Springfield, Virginia 22151
10. Pro ject/Tas it/Work Unit No.
11. Contract/Grant No.
68-01-3259
2. Sponsoring Organization Name and Address
Office of Toxic Substances
U.S. Environmental Protection Agency
Washington, O.C.
13. Type of Report it Period
Covered
Final Task Report
14.
15, Supplementary Notes
EPA Project Officer: Mr. Thomas E. Kopp
16. Abstracts
This report summarizes the required "physical and electrical properties of liquids
used as dielectric and cooling fluids in transformers, electromagnets, electric
motors, and capacitors. Prior to 1977, PCBs were widely used in all of these
applications and provided excellent fire safety. The use of PCBs was banned by
the Toxic Substances Control Act. The new materials that were developed as sub-
stitutes for PCBs in these applications are discussed in light of the required
properties and the performance trade-offs that resulted from their use.
17. Key Words and Document Analysis. . I7a. Descriptors
Polychlorinated Biphenyls
PCBs
Capacitors
Transformers
Silicones
Phthalates
Aromatic Compounds
Indenes
Hydrocarbons
I7b. Identifiers/Open-Ended Terms
Qilorohydrocarbons
Chlorinated Aromatic hydrocarbons
I7e. COSATX Field/Group
13. Arailabiiicy Statement
Release Unlimited
19- Security Class (This
Report)
'
20. security Class (This
Page
TJNCI.ASSIFTSP
21. No. ot
106
22. Price
FOHM NT1&M IMKV. IO-73J
EJDORSE3 BY ANSI AND UNESCO.
THIS FORM MAY BE REPRODUCED
U3CQMM.OC
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