and the fluids that can be used. On some hose, a lay strip provides
an easy method to determine if an installed hose is twisted.
To identify field-fabricated rubber hose assemblies, a metal band is
placed around the hose to identify the federal or national stock
number of the assembly and to give the operating pressure and
pressure test date.
Marking on Teflon Hose. Bulk teflon hose is identified by brass
bands spaced at 3-foot intervals marked with the specification number
and manufacturers code number.
Factory-fabricated teflon hose assemblies are identified by
permanently
attached
metal
bands
marked
with
the
military
specification, operating pressure in PSI, assembly part number, date
of proof test, and the hose manufacturers code number.
Locally manufactured teflon hose assemblies are identified by an
aluminum band.
The markings on the band can be impression-stamped,
etched, or engraved to include the federal or national stock number
of the hose assembly, part number, manufacturers part number or depot
code, operating pressure, and date of pressure test.
HOSE SIZE
The size of a hose is expressed as a dash number. This refers to the
inside diameter (ID) of the hose and is expressed in sixteenths of an
inch; for example, -2 is 2/16, -3 is 3/16, -4 is 4/16.
Whenever hose is used in conjunction with tubing, both the hose and
the tube must be equal in size. For example, if the tube size is 1/4
inch OD, a -4 (4/16) hose must be used with it.
CAUSES FOR HOSE REPLACEMENT
Replacement of rubber hose assemblies must be accomplished at
inspection
intervals
prescribed
in
the
applicable
aircraft
maintenance manual. Teflon hose does not deteriorate as a result of
age; therefore, periodic replacement is not required. However, both
rubber and teflon hose assemblies are subject to damage during
operation that can be cause for replacement of the line.
In any case, the replacement of the hose assembly must duplicate the
original hose in length, OD, ID, and contour, unless the line must be
rerouted for reasons specified in the paragraph which discusses
routing of lines near the beginning of this lessons.
53
AL0907
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