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TM 5-685/NAVFAC MO-912
nance program that is built around equipment, sys-
not biodegradable, some restrictions to their use
tem records, and visual inspections. The program is
apply. Silicone insulating liquid can be used as sub-
described in the manufacturer's literature fur-
stitute for PCBs when authorized by the Base engi-
nished with the components. If a problem develops,
neer. Special handling is required if PCBs are used
the user should perform general troubleshooting
in any equipment. Refer to 40 CFR 761 for PCB
procedures. The program includes appropriate
details. PCBs are powerful solvents. Handling and
analysis of the records.
disposal information and special gloves are re-
(1) Record keeping. Equipment and system log
quired. Check condition, alignment, and adjustment
sheets are important and necessary functions of
of contacts. Verify that contacts surfaces bear with
record keeping. The log sheets must be specifically
firm, even pressure. Use a fine file to dress rough
developed to suit individual applications (i.e., auxil-
contacts; replace pitted or burned contacts. Wipe
iary use).
clean all parts normally immersed in liquid, remove
(2) Troubleshooting. Perform troubleshoot-
traces of carbon that remain after the liquid has
ing procedures when abnormal operation of the
drained. Inspect insulating parts for cracks, or
system or equipment is observed. Maintenance per-
other damage requiring replacement. Test the di-
sonnel must then refer to records for interpretation
electric strength of the liquid, using a 0.1 inch gap
and comparison of performance data (i.e., log
with 1.1 inch diameter disk terminals. If strength is
sheets). Comparisons of operation should be made
less than 22 kV, remove and filter or replace with
under equal or closely similar conditions of load and
new liquid having a dielectric strength of at least 26
ambient temperature. The general scheme for
kV. Filter the liquid whenever inspection shows ex-
troubleshooting is outlined in the following para-
cessive carbon, even if its dielectric strength is sat-
isfactory, because the carbon will deposit on insulat-
(a) Use recognized industrial practices as the
ing surfaces decreasing the insulation strength.
general guide for servicing and refer to manufactur-
Liquid samples should be taken in a large-mouthed
er's literature.
glass bottle that has been cleaned and dried with
(b) The user should refer to manufacturer's
benzene. Use a cork stopper with this bottle. Draw
literature for specific information on individual cir-
test samples from the bottom of the tank after the
cuit breakers.
liquid has settled. The samples should be from the
(c) General service information for circuit
tank proper and not from the valve or drain pipe.
breakers includes the following safety require-
Periodically remove the liquid from the tank and
ments. Do not work on an energized breaker. Do not
wipe the inside of the tank, the tank linings, and
work on any part of a breaker with the test couplers
barriers to remove carbon. Inspect breaker and op-
engaged. Test couplers connect the breaker to the
erating mechanisms for loose hardware and missing
control circuit during testing. Maintenance closing
or broken cotter pins, retaining rings, etc. Check
devices for switchgear are not suitable for closing in
adjustments and readjust when necessary (refer to
on a live system. Speed in closing is as important as
the manufacturer's instruction book). Clean operat-
speed in opening. A wrench or other maintenance
ing mechanism and lubricate as for air-magnetic
tool is not fast enough. Before working on the
type breakers (refer to the manufacturer's instruc-
switchgear enclosure, remove all draw-out devices
tion book). Before replacing the tank, operate
such as circuit breakers and instrument transform-
breaker slowly with maintenance closing device to
ers. Do not lay tools down on the equipment while
verify there is no friction or binding to prevent or
working on it. It is too easy to forget a tool when
slow down its operation; then, check the electrical
closing an enclosure.
operation. Avoid operating the breaker any more
(d) Switchgear needs exercise. If the circuit
than is necessary when testing it without liquid in
breaker remains idle, either open or closed, for six
the tank. It is designed to operate in liquid and
months or more, it should be opened and closed
mechanical damage can result from excessive op-
several times during the period, preferably under
eration without it. When replacing the tank, fill to
load. If the breaker is operated by a relay or a
the correct level with liquid, be sure the gaskets are
switch, it too should be operated at this time.
undamaged and the tank nuts and flange nuts on
(e) Service circuit breakers using insulating
gauges and valves are tightened properly to prevent
liquid require special handling. Elevate the breaker
on an inspection rack and untank it to expose the
(f) Service air-blast type circuit breakers.
contacts. The insulating liquid usually used in cir-
Circuit breakers should be serviced (tested, exer-
cuit breakers is mineral oil. Equipment using liq-
cised, and calibrated) at intervals not to exceed two
uids containing polychlorinated biphenyls (PCBs)
years (refer to AR 420-43). Withdraw the breaker
may still be in use. Since PCBs are carcinogenic and
from its housing for maintenance. Circuit breakers

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