MIL-DTL-23928G
3.4.3.4.1 Bus bar forming. Flat bends shall have an inside radius of not less than the thickness of the bus bar, and
the ends of the bus bars shall be neatly finished. Edgewise bends of copper bars up to 2 inches in width shall be
made on an inside radius of 1 inch (25.4 mm).
3.4.3.4.2 Plating. Bus bars shall be silver plated in areas of current carrying contact with lugs, terminals, bus ties
and screw bolts. The plating shall be in accordance with ASTM B700, with the exception that the silver plate shall be
not less than .0002 inch (.005 mm) thick. The contact surfaces of all bus bars shall be silvered up to 1 inch (25.4
mm) past the joint area. At the discretion of the contractor, the entire bus may be silver surfaced or an area around
each hole may b silvered provided the silver area around the hole is not less than a .125 inch (3.18 mm) wide band.
Threaded surfaces, used as electrical contact surfaces, shall have silver thicknesses of not less than .0002 inch
(.005 mm).
3.4.3.4.3 Mechanical connections. Holes in the bus bars for bolting may be either punched or drilled, and the
contact area shall be smoothed. Where punching is used, the operation shall not appreciably indent the surface of
the bus bar in the vicinity of the hole. Slotted holes are not permitted. Contact nuts and contact spacer nuts for
copper stud contacts shall be of rolled brass and shall be sized to provide the necessary area for contact surface.
Contact nuts and contact spacer nuts for silvered contacts shall be silver-surfaced as specified for threaded surfaces
(see 3.4.3.4.2). Before bolting, a thick film of high viscosity paste in accordance with MIL-PRF-16173 shall be applied
at the joint area. Holes in bus bars for standard bolts shall have the following dimensions and the contact pressure
shall be in accordance with the torques specified:
Bolt size (inch)
Hole size (inch)
Torque (foot-pounds)
Minimum
Maximum
.375
.4375
14
16
.500
.5625
30
33
.625
.6875
50
55
For connections made to circuit breaker studs, the following torque requirements (lubricated) shall be used:
Copper stud size
Torque (foot-pounds)
Minimum
Maximum
3/8-16 UNC
7
8
1/2-13 UNC
15
17
3/4-16 UNF
25
28
3.4.3.4.3.1 Bolts and nuts used in bus bar joints. Bolts and nuts used in bus bar joints shall be of the coarse
thread series made of a 300 series corrosion-resistant steel (CRES) conforming to SAE AMS-QQ-S-763, silicon
bronze conforming to ASTM B98/B98M, ASTM B411/B411M, or ASTM B371, or zinc plated steel conforming to
MIL-DTL-1222 (a minimum of grade 2 or grade 5 depending on stress on the bolts and nuts). Flat washers of
material similar to the nuts and bolts shall be used under all bolt heads and nuts adjacent to the conductors.
Securing bolts shall be fitted with nuts conforming to figure 2. For typical bus bar mountings, see figure 2. Locking
devices listed in 3.3.9.1 a, b, and c shall be used in bus bar joints. Bus bars may be joined by welding; however,
welding shall be restricted to assemblies where disassembly will not be required for maintenance or repair of
underlying assemblies. All welders and weld procedures for copper bus bars shall be qualified in accordance with
NAVSEA S9074-AQ-GIB-010/248.
3.4.3.4.4 Bus separation. Busing in panels employing a combination of circuit breakers with different voltages
shall be separated by metal barriers.
11
For Parts Inquires submit RFQ to Parts Hangar, Inc.
© Copyright 2015 Integrated Publishing, Inc.
A Service Disabled Veteran Owned Small Business