The governing industry standard for the design of runways (including
suspension systems) and crane bridges utilizing patented track, is ANSI MH 27.1,
Specification for Underhung Cranes and Monorail Systems, published by Monorail
Manufacturers Association, Inc. This specification defines crane service classes
from "standby" to "severe duty cycle" service. (NCC policy is to specify Class C
"moderate" service as a minimum.)
Electric hoists and hoist/trolley units for all modes of
installation/suspension on underrunning cranes are governed by ANSI/ASME
HST-4M, Performance Standard for Overhead Electric Wire Rope Hoists, published by
the American Society of Mechanical Engineers.
ANSI/ASME B30.11, Monorails and Underhung Cranes, published by the
American Society of Mechanical Engineers. This standard focuses primarily on the
safety aspects of the design and operation of underrunning cranes.
ANSI/ASME B30.16, Overhead Hoists (Underhung), published by the American
Society of Mechanical Engineers. This standard focuses primarily on the safety
aspects of the design and operation of electric-powered wire rope and chain
hoists, hand chain operated (manual) chain hoists, and air-powered wire rope and
ANSI/ASME B30.17, Overhead and Gantry Cranes (Top Running Bridge, Single
Girder, Underhung Hoist, published by the American Society of Mechanical
Engineers. This standard focuses primarily on the safety aspects of the design
and operation of underrunning cranes utilizing all types of box section and single
web structural girders (including specially reinforced).
Cantilever Cranes. This category of cranes encompasses a large
assortment of designs, and it is not practical to describe all their variations.
They are grouped as stationary (jib) and traveling (wall), and only the most
prevalent designs within these groups are described in this handbook.
General Description. These cranes utilize various designs of
cantilevered booms with cross sections similar to the bridge girders of OET or
underrunning cranes. The cranes may either be stationary jib type (with a
pivoting boom mounted on a pillar or wall bracket) or traveling type (with the
boom mounted rigidly on a vertical frame) running on rails built into the wall
structures. Because of the moment imposed on the boom, the rated capacity of
these cranes is usually limited to 5 tons.
Stationary. Jib cranes have a restricted area of hook coverage but are
easy to install in any location that requires light hoisting service. Pillar type
jib cranes are free-standing, with a pivoting boom that is either fully
cantilevered or tie rod supported. The anchoring of the base of the pillar must
be designed for the entire moment imposed on the pillar. Jib cranes that are
mounted on wall brackets have the boom foot rigidly connected to a vertical mast
and the boom tip supported by a diagonal tie rod secured to the top of the mast.
The ends of the mast pivot on two in-line bearings built into the surrounding
building structure. Alternatively, the mast may be omitted and the boom foot and
upper end of the tie rod attached directly to in-line bearings supported by the
wall column. Figure 3 shows four varieties of stationary jib cranes.