MIL-DTL-14055G
3. REQUIREMENTS
3.1 Qualification. Cylinder cups furnished under this specification shall be products that are authorized
by the qualifying activity for listing on the applicable Qualified Products List (QPL) before contract award
3.2 Used, rebuilt or remanufactured components. No used, rebuilt or remanufactured components,
pieces, or parts, shall be used on the cylinder cups.
3.3 Materials. The materials used in the cylinder cups shall be a compound using a copolymer product
of butadiene and styrene (SBR) or ethylene propylene rubber (EPDM) as the basic material. The quality
of the ingredients used in an approved compound shall be so controlled as to insure uniformity of
performance of the cylinder cups.
3.3.1 Reference critical interface, materials, and processes. The materials and processes identified in
this specification are intended to assure mechanical compatibility, eliminate problems of contamination of
critical hydraulic fluids and hydraulic brake systems. Manufacturers of wheel cylinder cups, master
cylinder primary cups, and master cylinder secondary cups supplied to this specification may use
alternate industry recognized standards for materials and processes, provided prior approval is granted
by the qualifying activity. The use of such alternatives shall not result in inferior short term or long-term
performance or reliability.
3.3.2 Recycled, recovered environmentally preferable, or biobased materials. Recycled, recovered,
environmentally preferable, or biobased materials should be used to the maximum extent possible,
provided that the material meets or exceeds the operational and maintenance requirements, and
promotes economically advantageous life cycle costs.
3.4 Physical Properties.
3.4.1 Durometer hardness (Shore A).
3.4.1.1 Durometer hardness for qualification. When tested as specified in 4.7.2 for qualification, the
durometer hardness of the cups shall be within the limits of 55 to 75 points.
3.4.1.2 Durometer hardness for conformance. When tested as specified in 4.7.2 for conformance, the
durometer hardness of the cups shall be equal to the qualified value ± 5 points, providing it is within the
limits of 55 to 75 points. The qualified value is the durometer hardness value obtained on a particular
size and compound of cup at the time of qualification testing. The same value is thereby established for
the other sizes of cups of that same compound for which qualification has been established.
3.4.2 Accelerated aging. After cylinder cups have been subjected to the accelerated aging test specified
in 4.7.3, the change in durometer hardness (see 3.4.1) shall be within the limits of -5 to +5 points.
3.4.3 Low temperature.
3.4.3.1 Bendability. When subjected to the bend test specified in 4.7.4.1, the cup shall not crack and
shall return to its approximate original shape within 1 minute.
3.4.3.2 Fluid leakage. When cups are tested as specified in 4.7.4.2, there shall be no leakage of fluid
during the test.
3.4.4 Resistance to fluids at elevated temperature. After cylinder cups have been tested as specified in
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