MIL-DTL-24646B
3.3.4 Prohibited materials. Prohibited materials shall be as specified in MIL-E-917 with the following additions:
a.
Asbestos.
b.
Cadmium.
c.
Mercury (see 3.3.4.1).
3.3.4.1 Mercury. In addition to the mercury requirement as specified in MIL-E-917, no parts shall have come in
direct contact with metallic mercury, mercury compounds, or mercury bearing instruments or devices, employing only
a single boundary of containment, during manufacture or inspection. (A single boundary of containment is one which
is not backed up by a second seal or barrier to prevent escape and consequent mercury contamination in the event of
rupture of the primary seal or barrier.)
3.3.5 Recycled, recovered, or environmentally preferable materials. Recycled, recovered, or environmentally
preferable 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 Parts.
3.4.1 Fuse clips. Fuse clips shall be as specified (see 3.1). Fuse clip retainers shall not be used with fuse clips for
fuses rated 0-60 amperes (A). The clip shall be secured to the branch bus to allow easy removal without requiring
disassembly of other parts and will withstand a pull-force as specified in 4.6.1.
3.4.2 Fuse base. The fuse base shall be of glass melamine, as specified in type GME of MIL-I-24768/1, or shall
be a material selected from the laminates as specified in MIL-E-917, provided they meet the electrical and
mechanical requirements (see 3.1). The laminate shall be furnished in natural color except polyester laminates may
be furnished in tan or red. Current carrying parts (less switches) shall be mounted on the fuse base. Unless
otherwise specified (see 3.1), the fuse base shall be mounted in the approximate center of the enclosure.
3.4.3 Bus bars and connections. Bus bars and connections shall be brass, as specified in ASTM B16/B16M,
ASTM B36/36M, and ASTM B584.
3.4.3.1 Main bus bars. Main bus bars shall be of the sizes as specified (see 3.1). Holes in the bus bars may be
punched or drilled and the contact area shall be smooth. Where punching is used, the operation shall not appreciably
indent the surface of the bus bar in the vicinity of the hole.
3.4.3.2 Branch bus bars. Unless otherwise specified, branch bus bars shall be of the sizes as specified in Drawing
9000-S6202-73055 and shall be selected for the application specified (see 3.1).
3.4.3.3 Main and branch terminals. Unless otherwise specified (see 3.1), main and branch terminals shall be as
specified in Drawings 9000-S6202-73055 and 9000-S6202-73246 and shall be selected for the applicable wire size
specified (see 3.1). Terminals shall be silver brazed to the bus bars.
3.4.3.4 Studs and stud type main cable terminals. Unless otherwise specified (see 3.1), studs and stud type main
cable terminals shall be as specified in Drawing 9000-S6202-73055 and shall be through bolted at the main bus bar.
The nuts shall be torqued to 6.5 ± .5 foot-pounds and tack welded by gas tungsten arc welding as specified in
commercial procedures using CU-SN-C wire with 0.035 inch diameter. Only two tack welds shall be applied, one
opposite the other at the junction of the nut flats and the main bus. One tack weld shall be applied to all nuts before
the second tack weld is applied. All nuts shall be of brass. Self locking brass nuts may be used in lieu of nuts
requiring tack welding at the option of the contractor. The stud or main cable terminal may be ground smooth at the
nut to meet electrical clearance requirements. Stud connections to the branch buses shall be as specified in Drawing
9000-S6202-73055. Stud connections shall be silver brazed to the branch and feeder bus bars.
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