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 MIL-HDBK-1038
station case is required to be heavy duty dust-and-oil-tight. The exterior of the
pendent pushbutton station may be made of non-conductive material. Two-speed
pushbuttons are required to need a distinctive difference in pressure for low and
high speed positions. Pushbuttons are required to be so constructed that they
cannot be caught in the control case. Pushbutton stations are required to have
their elements legibly marked and arranged vertically in order from top to bottom:
POWER ON, POWER OFF, HOIST-UP, HOIST-DOWN, BRIDGE-NORTH/EAST, BRIDGE-SOUTH/WEST,
TROLLEY-EAST/NORTH, TROLLEY-WEST/SOUTH. Energization of the main line contactor
is required to be controlled by the POWER OFF-POWER ON pushbutton. Additionally,
there is required to be a white pilot light to indicate that power is available on
the load side of the crane disconnect and a blue pilot light to indicate that the
main contactor is energized. These lights are required to be located above
the POWER ON and POWER OFF pushbuttons. On AC powered cranes, the white pilot
light is required to utilize a separate, fused transformer for its energization.
A switch which controls the floodlights is required to be mounted on the pendent
pushbutton station in a location convenient for operation. Operating pushbuttons
and pilot lights are required to meet the heavy duty requirements of NEMA
Standards Publication No. ICS 2-216.
The pendent pushbutton station may be suspended from a festooned system
similar to that for a bridge-to-trolley electrification system.
5.5.5.14 Cab Control Stations. Cab master switches, pushbuttons and lighted
indicators may be console or armchair mounted. The operator's chair is required
to be adjustable forward and backward and to rotate as necessary to provide access
and operator visibility of the load. Master switch operating handles are to be
non-spring returned to OFF, and to have an OFF position detent. They often have an
OPERATOR ATTENTIVENESS MONITORING (dead-man) switch. At least one dead-man switch
must be continually hand activated in order to operate all crane motions. All
master switch operating handles must be in the OFF position before any initial
crane function can begin. Additionally, there is required to be a white pilot
light to indicate that power is available on the load side of the crane disconnect
and a blue pilot light to indicate that the main contactor is energized, a
floodlight toggle switch, and a horn pushbutton. On AC powered cranes, the white
pilot light is required to utilize a separate, fused transformer for its
energization. Furthermore, on portal and floating cranes which are variably-rated
at capacities less than their straight-line rating beyond a certain main hoist
hook radius, it is required that there be a flashing yellow pilot light in the cab
to indicate that the hook is beyond the maximum radius for its straight-line
rating. There is required to be a black POWER ON pushbutton and a red mushroom
head POWER OFF pushbutton. Energization of the main line contactor is required to
be controlled by the POWER OFF-POWER ON pushbutton. The POWER ON pushbutton is
required to be guarded to prevent accidental actuation. Operating pushbuttons and
pilot lights are required to meet the heavy duty requirements of NEMA Standards
Publication No. ICS 2-216.
5.5.5.15 Transformers. Transformers are selected to achieve the intended voltage
change. Knowledge of the turns ratio between primary and secondary windings is
required to be used to make this determination.
All AC control circuits are required to be fed from a single phase, air
cooled, double wound transformer with a grounded metal screen between the primary
and secondary windings of the transformer.
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