IDENTIFICATION OF FLUID LINES (Refer to figure 204)
Fluid lines in aircraft are often identified by markers made up of color codes, words, and geometric
symbols. These markers identify each line’s function, content, and primary hazard, as well as direction of fluid
flow.
In most instances, fluid lines are marked with l-inch tape or decals. Paint is used on lines in engine
compartments, where there is the possibility of tapes, decals or tags being drawn into engine induction system.
In addition to above-mentioned markings, certain lines may be further identified as to specific function
within a system; for example, DRAIN, VENT, PRESSURE or RETURN.
Lines conveying fuel may be marked FLAM; lines containing toxic materials are marked TOXIC in place
of FLAM. Lines containing physically dangerous materials, such as oxygen, nitrogen, or freon, are marked
PHDAN.
Aircraft and engine manufacturers are responsible for original installation of identification markers, but
aviation mechanics are responsible for replacement when it becomes necessary.
G e n e r a l l y, tapes and decals are placed on both ends of a line and at least once in each compartment
through which the line runs. In addition, identification markers are placed immediately adjacent to each valve,
regulator, filter or other accessory within a line. Where paint or tags are used, location requirements are the
same as for tapes and decals.
FLARELESS TUBE ASSEMBLIES (Refer to figure 20-5)
Although the use of flareless tube fittings eliminates tube flaring, another operation, known as presetting,
is necessary before installation of a flareless tube. Presetting is performed as follows:
l. Cut tube to correct length, with ends perfectly square. Deburr inside and outside of tube. Slip nut, then
sleeve, over tube (step l).
2. Lubricate threads of fitting and nut. See figure 20-5 for proper lubricant to use. Place fitting in vise
(step 4). Hold tubing firmly and squarely on seat in fitting. (Tube must bottom firmly in the fitting.)
Tighten nut until cutting edge of sleeve grips tube. This point is determined by slowly turning tube
back and forth while tightening nut. When tube no longer turns, nut is ready for final tightening.
3. Final tightening depends upon the tubing. For aluminum alloy tubing up to and including l / 2 inch
outside diameter, tighten nut one to one and one-sixth turns. For steel and aluminum alloy tubing over
l/2 inch outside diameter, tighten one and one-sixth to one and one-half turns.
After presetting sleeve, disconnect tubing from fitting and check following points:
l. The tube must extend 3/32 to l/8 inch beyond the sleeve pilot or blowoff may occur.
2. The sleeve pilot must contact tube or have a minimum clearance of 0.005 inch for aluminum alloy
tubing or 0.015 inch for steel tubing.
3. A slight collapse of tube at sleeve cut is permissible. No movement of sleeve pilot, except rotation is
acceptable.
20 - 10 - 00
Page - 20 - 04
Reissued: August 1, 1986
1E7
PIPER AIRCRAFT
PA-28-236
MAINTENANCE MANUAL
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