by spring pressure and set by hydraulic pressure. Electrical portion of
the braking system shall be designed such that the shoes will be
spring-applied and electrically-released.] Braking system shall be
automatically set when controls are released or power is interrupted.
Provisions shall be made to facilitate easy brake adjustment. Brakes shall
have a torque rating of at least 50 percent of trolley drive motor rated
torque.
2.3.7.4
[Bridge] [Gantry] Brakes
[[Bridge] [Gantry] braking system shall be provided with a spring-applied
and electrically-released single shoe, disc, or conical brake for each
bridge drive motor.] [[Bridge] [Gantry] braking system shall be provided
with electrically-operated and hydraulically-operated shoe, disc, or
conical brakes. Hydraulic portion of braking system shall be designed so
that the shoes will be disengaged with spring pressure and set with
hydraulic pressure. Electrical portion of braking system shall be designed
so that the shoes will be spring-applied and electrically-released.]
Braking system shall be automatically set when controls are released or
power is interrupted. Provisions shall be made to facilitate easy brake
adjustment. Brakes shall have a torque rating of at least 50 percent of
bridge drive motor rated torque.
2.3.8
Wheels
**************************************************************************
NOTE: Include the second sentence for CMAA 70 class
D and E, cranes; otherwise delete. Include the
requirement for trolley wheels only for multiple
girder cranes.
**************************************************************************
Wheels shall be manufactured of rolled or forged steel. Wheel treads and
flanges shall be rim toughened to between 320 and 370 Brinell hardness
number. [Bridge] [Bridge and trolley] wheels shall be double-flanged.
Trolley wheels shall have straight treads. Bridge wheels shall have
straight treads. Wheels shall be equipped with self-aligning double-row
spherical roller-bearings of capacity as recommended by bearing
manufacturer for design load of trolley or bridge.
2.3.9
Bearings
**************************************************************************
NOTE: Equalizer sheaves compensate for unequal
length, stretch of the hoisting, and swinging of the
load block.
**************************************************************************
Bearings shall be antifriction type, except bearings which are subject only
to small rocker motion. Equalizer sheaves shall be equipped with sintered
oil-impregnated type bushings in accordance with ASTM B 438/B 438M, ASTM B
439, or ASTM B 612.
2.3.10
Anti-Drip Provisions
**************************************************************************
NOTE: Delete this paragraph if lubricant leaks are
acceptable on the operating floor.
SECTION 14630A
Page 25
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