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| MIL-S-19676A(OS)
3.3.4 Flammable materials. Materials which may be ignited or exploded by an electrical spark shall not be
used. Flammable materials impregnating the potting compounds may be used if they are enclosed in fire resistant
containers
3.3.5 Toxic materials. Materials which may produce harmful toxic effects under conditions that occur in naval
vessels, including fire shall not be used.
3.3.6 Die castings. Die castings shall not be used without specific approval of the Naval Sea Systems Command
for each part or piece.
3.3.7 Magnesium. Magnesium shall not be used without specific approval of the Naval Sea Systems Command
for each part or piece. This does not preclude use of alloys containing a low percentage of magnesium.
3.3.8 Aluminum alloys. Insofar as possible, aluminum alloys shall be used wherever weight saving can be
effected without sacrificing other essential qualities. Aluminum alloys shall conform to MIL-F-18870.
3.3.9 Iron and steel. The use of iron and steel, except where required for electro-magnetic or low-frequency
shielding purposes, shall be held to a minimum commensurate with strength requirements. Cast iron shall not
be used without specific approval of the Naval Sea Systems Command for each individual application. Steel alloys
of the corrosion-resistant type shall be used where strength and corrosion resistance are required in the same part.
3.3.10 Insulating materials. All insulating materials shall have high arc resistance and Iow moisture absorption.
Ceramic, glass, teflon, nylon base plastic or other materials approved for the purpose shall be used where the
impressed electrical potential exceeds 500 volts rms ac or equivalent dc.
3.3.11 Hook-up-wire. The hook-up-wire for the internal wiring shall be in accordance with the requirements
of MIL-W-16678 (NAVY). Extruded insulation in accordance with this specification shall be used.
3.4 Construction.
3.4.1 Welding. In the event welded fabrications are employed in the equipment, the welds shall be of ample
size with thorough penetration and good fusion, and shall be substantially free of injurious or unsightly surface
defects. All welds shall be capable of withstanding strength tests to destruction in which case failure shall not occur
within the weld itself. There shall be no deleterious effects of the welding process in adjacent material. All welds
shall be cleaned of scale oxidation products and excess flux by sandblasting, wirebrushing, or other suitable means.
Acid, if used for cleaning, shall be neutralized and removed. Tack or spot welds, if employed, shall be provided
in sufficient number to ensure adequate strength; a minimum of two such welds shall be used to hold a part.
3.4.2 Soldering. Only Class H solder in accordance with QQ-S-571 shall be used for electrical connections.
All connections shall be mechanically secure before soldering. Only the minimum of solder necessary for a good
electrical connection shall be used, and care shall be exercised to ensure that adjacent parts or wiring are not
damaged in the process. Corrosive flux shall not be used and the flux residue shall be removed when soldering
is completed.
3.4.3 Electrolytic action. The faying surfaces of dissimilar metals shall be suitably treated to inhibit electrolytic
action in presence of atmospheric sodium chloride in those cases where such action would normally occur.
3.4.4 Moisture pockets. Recesses in which condensed moisture can collect shall be avoided or properly drained.
3.4.5 Protective coatings and treatment.
3.45.1 General. All parts manufactured from materials not resistant to corrosion shall be provided with a protective
coating of finish, except as noted hereinafter. The coatings need not be applied to:
a. Mechanisms that are bathed in oil or coated with grease such as bearings, gears, and cams.
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