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13-52 Standards and Practices

Operator Safety Considerations

RF energy must be contained properly by shielding and transmission lines. All input and output
RF connections, cables, flanges, and gaskets must be RF leakproof. The following guidelines
should be followed at all times:

•

Never operate a power tube without a properly matched RF energy absorbing load attached.

•

Never look into or expose any part of the body to an antenna or open RF generating tube, cir-
cuit, or RF transmission system that is energized.

•

Monitor the RF system for radiation leakage at regular intervals and after servicing.

13.3.6 X-Ray Radiation Hazard

The voltages typically used in microwave tubes are capable of producing dangerous X rays. As
voltages increase beyond 15 kV, metal-body tubes are capable of producing progressively more
dangerous radiation. Adequate X-ray shielding must be provided on all sides of such tubes, par-
ticularly at the cathode and collector ends, as well as at the modulator and pulse transformer
tanks (as appropriate). High-voltage tubes never should be operated without adequate X-ray
shielding in place. The X-ray radiation of the device should be checked at regular intervals and
after servicing.

13.3.7 Implosion Hazard

Because of the high internal vacuum in power grid and microwave tubes, the glass or ceramic
output window or envelope can shatter inward (implode) if struck with sufficient force or
exposed to sufficient mechanical shock. Flying debris could result in bodily injury, including
cuts and puncture wounds. If the device is made of beryllium oxide ceramic, implosion may pro-
duce highly toxic dust or fumes.

In the event of such an implosion, assume that toxic BeO ceramic is involved unless con-

firmed otherwise.

13.3.8 Hot Coolant and Surfaces

Extreme heat occurs in the electron collector of a microwave tube and the anode of a power grid
tube during operation. Coolant channels used for water or vapor cooling also can reach high tem-
peratures (boiling—100°C—and above), and the coolant is typically under pressure (as high as
100 psi). Some devices are cooled by boiling the coolant to form steam.

Contact with hot portions of the tube or its cooling system can scald or burn. Carefully check

that all fittings and connections are secure, and monitor back pressure for changes in cooling
system performance. If back pressure is increased above normal operating values, shut the sys-
tem down and clear the restriction.

For a device whose anode or collector is air-cooled, the external surface normally operates at

a temperature of 200 to 300°C. Other parts of the tube also may reach high temperatures, partic-

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Safety Issues

Safety Issues 13-53

ularly the cathode insulator and the cathode/heater surfaces. All hot surfaces remain hot for an
extended time after the tube is shut off. To prevent serious burns, take care to avoid bodily con-
tact with these surfaces during operation and for a reasonable cool-down period afterward.

13.3.9 Polychlorinated Biphenyls

PCBs belong to a family of organic compounds known as chlorinated hydrocarbons. Virtually
all PCBs in existence today have been synthetically manufactured. PCBs have a heavy oil-like
consistency, high boiling point, a high degree of chemical stability, low flammability, and low
electrical conductivity. These characteristics resulted in the widespread use of PCBs in high-volt-
age capacitors and transformers. Commercial products containing PCBs were widely distributed
between 1957 and 1977 under several trade names including:

•

Aroclor

•

Pyroclor

•

Sanotherm

•

Pyranol

•

Askarel

Askarel is also a generic name used for nonflammable dielectric fluids containing PCBs. Table
13.3.5 lists some common trade names used for Askarel. These trade names typically will be
listed on the nameplate of a PCB transformer or capacitor.

PCBs are harmful because once they are released into the environment, they tend not to break

apart into other substances. Instead, PCBs persist, taking several decades to slowly decompose.
By remaining in the environment, they can be taken up and stored in the fatty tissues of all organ-
isms, from which they are slowly released into the bloodstream. Therefore, because of the stor-
age in fat, the concentration of PCBs in body tissues can increase with time, even though PCB
exposure levels may be quite low. This process is called bioaccumulation. Furthermore, as PCBs
accumulate in the tissues of simple organisms, and as they are consumed by progressively higher
organisms, the concentration increases. This process is called biomagnification. These two fac-
tors are especially significant because PCBs are harmful even at low levels. Specifically, PCBs
have been shown to cause chronic (long-term) toxic effects in some species of animals and
aquatic life. Well-documented tests on laboratory animals show that various levels of PCBs can
cause reproductive effects, gastric disorders, skin lesions, and cancerous tumors.

PCBs may enter the body through the lungs, the gastrointestinal tract, and the skin. After

absorption, PCBs are circulated in the blood throughout the body and stored in fatty tissues and a
variety of organs, including the liver, kidneys, lungs, adrenal glands, brain, heart, and skin.

The health risk from PCBs lies not only in the PCB itself, but also in the chemicals that

develop when PCBs are heated. Laboratory studies have confirmed that PCB by-products,
including  polychlorinated dibenzofurans (PCDFs) and polychlorinated dibenzo-p-dioxins
(PCDDs), are formed when PCBs or chlorobenzenes are heated to temperatures ranging from
approximately 900 to 1300°F. Unfortunately, these products are more toxic than PCBs them-
selves.

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13-54 Standards and Practices

13.3.9a

Governmental Action

The U.S. Congress took action to control PCBs in October 1975 by passing the Toxic Substances
Control Act (TSCA). A section of this law specifically directed the EPA to regulate PCBs. Three
years later the Environmental Protection Agency (EPA) issued regulations to implement the con-
gressional ban on the manufacture, processing, distribution, and disposal of PCBs. Since that
time, several revisions and updates have been issued by the EPA. One of these revisions, issued
in 1982, specifically addressed the type of equipment used in industrial plants and transmitting
stations. Failure to properly follow the rules regarding the use and disposal of PCBs has resulted
in high fines and even jail sentences.

Although PCBs are no longer being produced for electrical products in the United States,

there are thousands of PCB transformers and millions of small PCB capacitors still in use or in
storage. The threat of widespread contamination from PCB fire-related incidents is one reason
behind the EPA’s efforts to reduce the number of PCB products in the environment. The users of
high-power equipment are affected by the regulations primarily because of the widespread use of
PCB transformers and capacitors. These components usually are located in older (pre-1979) sys-
tems, so this is the first place to look for them. However, some facilities also maintain their own
primary power transformers. Unless these transformers are of recent vintage, it is quite likely
that they too contain a PCB dielectric. Table 13.3.6 lists the primary classifications of PCB
devices.

13.3.9b

PCB Components

The two most common PCB components are transformers and capacitors. A PCB transformer is
one containing at least 500 ppm (parts per million) PCBs in the dielectric fluid. An Askarel
transformer generally has 600,000 ppm or more. A PCB transformer may be converted to a PCB-
contaminated device (50 to 500 ppm) or a non-PCB device (less than 50 ppm) by having it
drained, refilled, and tested. The testing must not take place until the transformer has been in ser-
vice for a minimum of 90 days. Note that this is not something a maintenance technician can do.
It is the exclusive domain of specialized remanufacturing companies.

PCB transformers must be inspected quarterly for leaks. If an impervious dike is built around

the transformer sufficient to contain all of the liquid material, the inspections can be conducted
yearly. Similarly, if the transformer is tested and found to contain less than 60,000 ppm, a yearly
inspection is sufficient. Failed PCB transformers cannot be repaired; they must be properly dis-
posed of.

If a leak develops, it must be contained and daily inspections begun. A cleanup must be initi-

ated as soon as possible, but no later than 48 hours after the leak is discovered. Adequate records

Table 13.3.5 Commonly Used Trade Names for PCB Insulating Material

Apirolio

Abestol

Askarel

Aroclor B

Chlorexto

Chlophen

Chlorinol

Clorphon

Diaclor

DK

Dykanol

EEC-18

Elemex

Eucarel

Fenclor

Hyvol

Inclor

Inerteen

Kanechlor

No-Flamol

Phenodlor

Pydraul

Pyralene

Pyranol

Pyroclor

Sal-T-Kuhl

Santothern FR

Santovac

Solvol

Thermin

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Safety Issues 13-55

must be kept of all inspections, leaks, and actions taken for 3 years after disposal of the compo-
nent. Combustible materials must be kept a minimum of 5 m from a PCB transformer and its
enclosure.

As of October 1, 1990, the use of PCB transformers (500 ppm or greater) was prohibited in or

near commercial buildings when the secondary voltages are 480 V ac or higher.

The EPA regulations also require that the operator notify others of the possible dangers. All

PCB transformers (including PCB transformers in storage for reuse) must be registered with the
local fire department. The following information must be supplied:

•

The location of the PCB transformer(s).

•

Address(es) of the building(s) and, for outdoor PCB transformers, the location.

•

Principal constituent of the dielectric fluid in the transformer(s).

Table 13.3.6 Definition of PCB Terms as Identified by the EPA

Term

Definition

Examples

PCB

Any chemical substance that is limited to the 
biphenyl molecule that has been chlorinated to 
varying degrees, or any combination of sub-
stances that contain such substances.

PCB dielectric fluids, PCB heat-transfer fluids, 
PCB hydraulic fluids, 2,2’,4-trichlorobiphenyl

PCB article

Any manufactured article, other than a PCB 
container, that contains PCBs and whose sur-
face has been in direct contact with PCBs.

Capacitors, transformers, electric motors, 
pumps, pipes

PCB container

A device used to contain PCBs or PCB articles, 
and whose surface has been in direct contact 
with PCBs.

Packages, cans, bottles, bags, barrels, drums, 
tanks

PCB article con-
tainer

A device used to contain PCB articles or equip-
ment, and whose surface has not been in direct 
contact with PCBs.

Packages, cans, bottles, bags, barrels, drums, 
tanks

PCB equipment

Any manufactured item, other than a PCB con-
tainer or PCB article container, that contains a 
PCB article or other PCB equipment.

Microwave systems, fluorescent light ballasts, 
electronic equipment

PCB item

Any PCB article, PCB article container, PCB 
container, or PCB equipment that deliberately 
or unintentionally contains, or has as a part of 
it, any PCBs.

PCB transformer

Any transformer that contains PCBs in concen-
trations of 500 ppm or greater.

PCB contaminated Any electric equipment that contains more than 

50, but less than 500 ppm of PCBs. (Oil-filled 
electric equipment other than circuit breakers, 
reclosers, and cable whose PCB concentration 
is unknown must be assumed to be PCB-con-
taminated electric equipment.)

Transformers, capacitors, contaminated circuit 
breakers, reclosers, voltage regulators, 
switches, cable, electromagnets

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13-56 Standards and Practices

•

Name and telephone number of the contact person in the event of a fire involving the equip-
ment.

Any PCB transformers used in a commercial building must be registered with the building

owner. All building owners within 30 m of such PCB transformers also must be notified. In the
event of a fire-related incident involving the release of PCBs, the Coast Guard National Spill
Response Center (800-424-8802) must be notified immediately. Appropriate measures also must
be taken to contain and control any possible PCB release into water.

Capacitors are divided into two size classes, large and small. A PCB small capacitor contains

less than 1.36 kg (3 lbs) of dielectric fluid. A capacitor having less than 100 in

3

 also is consid-

ered to contain less than 3 lb of dielectric fluid. A PCB large capacitor has a volume of more than
200 in

3

 and is considered to contain more than 3 lb of dielectric fluid. Any capacitor having a

volume between 100 and 200 in

3

 is considered to contain 3 lb of dielectric, provided the total

weight is less than 9 lb. A PCB large high-voltage capacitor contains 3 lb or more of dielectric
fluid and operates at voltages of 2 kV or greater. A large low-voltage capacitor also contains 3 lb
or more of dielectric fluid but operates below 2 kV.

The use and servicing of PCB small capacitors is not restricted by the EPA unless there is a

leak. In that event, the leak must be repaired or the capacitor disposed of. Disposal may be han-
dled by an approved incineration facility, or the component may be placed in a specified con-
tainer and buried in an approved chemical waste landfill. Items such as capacitors that are
leaking oil greater than 500 ppm PCBs should be taken to an EPA-approved PCB disposal facil-
ity.

13.3.9c

PCB Liability Management

Properly managing the PCB risk is not particularly difficult; the keys are understanding the regu-
lations and following them carefully. Any program should include the following steps:

•

Locate and identify all PCB devices. Check all stored or spare devices.

•

Properly label PCB transformers and capacitors according to EPA requirements.

•

Perform the required inspections and maintain an accurate log of PCB items, their location,
inspection results, and actions taken. These records must be maintained for 3 years after dis-
posal of the PCB component.

•

Complete the annual report of PCBs and PCB items by July 1 of each year. This report must
be retained for 5 years.

•

Arrange for necessary disposal through a company licensed to handle PCBs. If there are any
doubts about the company’s license, contact the EPA.

•

Report the location of all PCB transformers to the local fire department and to the owners of
any nearby buildings.

The importance of following the EPA regulations cannot be overstated.

13.3.10 References

1. National Electrical Code, NFPA #70.

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