Non-metals. Non-metallic materials used, including
plastics, fabrics, and protective finishes shall be flame-resistant,
shall not support combustion, shall be moisture resistant, and shall not
be adversely affected by weather, temperature, and ambient conditions.
Fungus resistance. Materials that are nutrients for
fungi shall not be used where it is practical to avoid them, Where
used, all nutrient materials and associated fungicidal treatments used
shall be specified on the valve manufacturing drawings.
Elastomers. Elastomeric components shall be fabricated
from materials covered by applicable specifications and shall have
maximum practicable ozone and aging resistance and hydrolytic stability
consistent with performance requirements. All elastomeric materials
used shall be subject to the specific approval of the qualifying activity
based upon the demonstrated suitability of the materials for the expected
operating and storage environments. Age controls for synthetic rubber
parts shall be in accordance with MIL-STD-1523.
Metals. All metals shall be compatible with the
intended temperature, functional, service and storage conditions to
which the valve will be exposed. Metals which are not protected from
corrosion by lubricating oil shall be of the corrosion-resisting type,
or shall be suitably treated to resist corrosion in accordance with
Steels (except corrosion-resistant).
Aircraft quality, vacuum-melted steel shall be
used for parts which are heat treated to an ultimate tensile strength
220,000 psi and above. Such applications shall be subject to specific
approval by the qualifying activity.
The ultimate tensile strength range in production
parts shall not exceed the following limits: