MIL-HDBK-1038
o)
Circuit breakers are required for hoist circuits; fuses for control
circuits.
p)
A horn is required to provide an audible warning whenever any travel
drive is energized.
q)
An epoxy paint is recommended for the hoist and trolley structural
assemblies.
6.5
Ordnance/Explosives Handling. Cranes handling palletized or unpackaged
ammunition, missiles, torpedoes, and other types of ordnance are required to
incorporate the following design features:
a)
OET cranes are required to be CMAA #70, Class D, or higher.
Underrunning cranes CMAA #74, Class D or higher; with patented track bridge
girders per ANSI MH 27.1.
b)
Standard commercial hoist/trolley units are required to be ANSI/ASME
HST-4M, Duty Class H-4.
c)
For custom designed (built-up) hoists, shaft fatigue design factor
is required to be 1.5 or greater.
d)
Hoists on OET, underrunning, cantilever, gantry, and semi-gantry
cranes are required to have two braking means; either in the form of two electro-
mechanical holding brakes (each rated at 100 percent of the rated load hoisting
torque), or one electro-mechanical holding brake (rated at 150 percent of the
rated motor torque) and a mechanical load brake or, in case of a hoist with a
wound rotor motor, an eddy-current brake. The eddy-current brake is considered an
acceptable braking means only if resistors (not saturable reactors) are utilized
in the rotor circuit of the hoist motor. Disc brakes are acceptable, but they
should be of the DC self-adjusting type.
e)
Portal, floating, container, and other cranes with the operator's
cabs on the same structure as the hoist may include a foot operated hydraulic
hoist brake in addition to the two electro-mechanical brakes for speed modulation.
Alternatively, instead of an independent hydraulic brake, one of the elctro-
mechanical brakes may be equipped with an integral hydraulic system for over-
riding the electrical release and applying the brake.
f)
All drive components of custom designed (built-up) hoists-those that
transmit the driving torque, braking torque, and their supports/housings are
required to be steel. Exceptions are permitted for gear reducer housing and brake
wheels and discs, which may be ductile cast iron; and electric motor housings,
which may be ductile cast iron or cast aluminum. These ductile cast iron and cast
aluminum components must have a minimum elongation of 5 percent in 2.0 inches.
g)
Standard commercial hoist and hoist/trolley units, when used because
of site-specific constraints, must be selected to comply with the requirements of
item (f), above, to the maximum practical extent. (It is considered practical to
replace certain components and assemblies, such as wire ropes and load blocks,
with their higher grade or custom designed counterparts.)
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