Standard parts. Military standard parts shall be
used whenever they are suitable for the purpose, and shall be identified
by their military part number. All parts of the same part number shall
be interchangeable as applied within the system. Commercial utility
parts such as screws, bolts, nuts, and cotter pins may be used provided
they possess suitable properties and are replaceable by the standard
parts (MS and AN) without alteration and provided the corresponding
standard part numbers are referenced in the parts list and on the manufacturer's
drawings. In the event there is no suitable corresponding standard part
in effect on date of invitation for bids, commercial parts may be used
provided they conform to all requirements of this specification.
Straight screw threads. Screw threads shall conform
to the requirements of MIL-S-8879 except for electrical connections,
fluid fittings and ground and cut threads incorporated in proprietary
parts which do not have equivalent standards. All exceptions shall
conform to MXL-S-7742.
Tapered pipe threads. Tapered pipe threads shall be
in accordance with MIL-P-7105 and may be used only for permanently
plugging drilled or cored openings.
Threaded inserts. All threaded connections in
nonferrous materials shall have steel inserts which are suitably protected
from electrolytic corrosion.
Safetying Provisions shall be made to prevent all
screws and screw parts from accidental loosening. Such parts shall be
safety wired or fitted with safety stop nuts, where applicable. All
other connections liable to be loosened by vibration shall be safetied
in a similar manner. If safetying is by wiring, it shall be in accordance
with MS33540. The use of lock nuts which incorporate nonmetallic
inserts as a locking feature shall be avoided.
Packings. All packings shall be in accordance with
the requirements of MS33666 or MS33668.
Filter. If filters are required, they shall be
self-cleaning and shall be sized to protect the valve from the contamination
required in 4.5.9. Any filter used shall be readily removable for
replacement without disassembly of the valve.
Snapring retainer. The use of snapring retainers is
prohibited unless failure of the retainer will not affect operation
adversely or allow retainer fragments to enter the air passages.