PIPER
SENECA
II
SERVICE
MANUAL
b.
Use
compressed air or lintless cloth
to
dry the parts, unless sufficient time
is
available for them
to
air dry.
c.
Wipe
electrical components with a clean, dry cloth. If foreign material
is
difficult
to
remove,
moisten the cloth in carbon tetrachloride or electrical contact cleaner and clean
all
exterior surfaces
thoroughly.
13-56. CLEANING
AND
INSPECTING THE COMBUSTION TUBE ASSEMBLY (30,000 BTU). (Refer
to
Figure 13-18.)
a.
Slight scaling and discoloration
of
the combustion tube assembly (7) is a normal condition for
units
that
have been in service up
to
1000 airplane hours. The slight scaling condition will appear
to
be
mottled and a small accumulation
of
blue-gray powder may be present on the surface in certain areas. This
condition does
not
require replacement
of
the combustion tube assembly, unless severe overheating has
produced soft spots in the metal.
NOTE
This assembly should be inspected prior
to
cleaning in order to
prevent the removal of visible evidences
of
damage.
b. Look inside the exhaust outlet to determine if the combustion tube appears to
be
heavily scaled
or
mottled. Deformation
is
more difficult
to
detect visually
but
can usually be observed by looking straight
through the combustion tube assembly and sighting along the outer surface of the inner combustion tube.
An assembly that has been obviously deformed should be replaced. Slight deformation will
not
affect
heater operation unless it
is
extensive and localized enough to reduce the flow
of
ventilating air through the
heater more than 10 percent.
c.
The combustion tube assembly may be cleaned by either
of
two methods:
1.
One method
is
to
soak the combustion tube assembly overnight in an Oakite
M-S
Stripper
solution made by mixing one pound
of
Oakite salts with each gallon
of
water used. The solution should be
maintained at a temperature
of
between
190°F
and 210°F. After soaking overnight, rinse the combustion
tube assembly thoroughly in water
to
remove all traces
of
the Oakite solution. In order to reach all areas
of
the combustion tube assembly,
it
is advisable
to
let
it
stand in the rinsing water for
as
long
as
1/2 hour,
while occasionally agitating
it
to
circulate the water. All openings should
be
left open during this operation.
Be
sure
to
dry the combustion tube assembly thoroughly after cleaning.
2.
A second method
of
cleaning is what
is
commonly known
as
hand "tumbling." Insert shot
or
other metallic particles through the exhaust outlet opening; then close all openings and shake the
combustion tube assembly vigorously while rotating
it
and changing from end-to-end frequently.
Be
sure
to
pour
out
all
of
the particles and loosened material; then with
all
openings uncovered, direct a stream
of
compressed air into the combustion tube assembly from first one opening, then the other. Make sure
all
loose material is removed.
13-57. INSPECTION
OF
REMAINING COMPONENTS (30,000 BTU). (Refer
to
Figure 13-18.)
a.
Discard all rubber parts such
as
grommets, gaskets, etc. These items should always
be
replaced at
overhaul. Also discard the rope gasket (31
).
b. Inspect
all
wires and wiring harnesses for damage to insulation, damaged terminals, chafed or
cracked insulation and broken plastic bands. Individual wires can be replaced by making up new wires from
No. 16
AWG
stock and cut
to
correct length.
It
is advisable to use an acceptable crimping tool for installing
terminals, rather than solder for all heater wiring connections.
If
wiring harness damage
is
visible, the entire
harness assembly should be replaced.
If
only one or more wires are damaged, cut the cable ties, make
up
new wires, install them in the harnesses and restore all cable ties and clamps.
If
heater controls were
operating properly at the time
of
removal, reinstall them.
Reissued:
10/11/79
HEATING
AND
VENTILATING
SYSTEM
2K13
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