SUPPLEMENTARY REQUIREMENTS AND DESIGN CONSIDERATIONS
Supplementary Requirements. Cranes operating in non-routine environments
or unique, dedicated service must include additional features and characteristics
beyond those described in the preceding sections of this handbook. In many cases
the prescribed crane classifications correspond to more severe commercial service
than the actual operational environment of these cranes, but these classifications
are warranted by the cranes' inherent higher level of reliability and robustness
desired for critical applications.
Special Purpose Service. Cranes in "special purpose service" (SPS)
support various lifting operations associated with the servicing of nuclear
reactors and related components aboard vessels and in shore facilities. With the
exception of the container cranes, all the main crane types described in Section 2
of this handbook are used in SPS lifting operations. The following design
features are mandatory for all SPS cranes; any deviations must be approved by NCC:
OET cranes are required to be CMAA #70, Class D or higher. (Those
with rated capacities of 10 tons or less, must also comply with the requirements
of NAVSEA 0989-030-7000, Lifting Standard.)
Underrunning cranes are required to be CMAA #74, Class D; with
patented track bridge girders per ANSI MH27.1. (Those with rated capacities of 10
tons or less, must also comply with the requirements of NAVSEA 0989-030-7000,
Lifting Standard.) Crane runways for underrunning end trucks must also be
patented track per ANSI MH 27.1.
Standard commercial hoist/trolley units are required to be ANSI/ASME
HST-4M, Duty Class H-4 or H-5.
Overrunning end trucks are required to be welded plate
box-sections (with diaphragms) between the wheel pockets. Web plates are required
to incorporate welded blocks with machined seats (semi-circular notches) for wheel
axle bearings. (Flanged cartridge bearing housings are not permitted.)
Trolley frames are required to incorporate wheel bearing seats, as
Trolley structural members, in close proximity to the wire rope drum
flanges and designed specifically for the anticipated loads in case of wire rope
drum failure, are required to provide support for the wire rope drum in case of
shaft failure. For hoist arrangements with a drum gear, the wire rope drum
supports must also maintain drum gear tooth engagement with the drive pinion in
case of shaft failure.
Boom main chords are required to be rolled (open) structural
sections, so that the condition of all their surfaces may be monitored. Tubular
(closed) structural sections are permitted only for the lacing members.
Wire rope design factor is required to be 6.0 or greater.
For custom designed (built-up) cranes, shaft fatigue design factor
is required to be 2.0 or greater.