Ch 7 A

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25 Νοε 2013 (πριν από 3 χρόνια και 8 μήνες)

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Rigging

Unit 5 A

Hoists & cranes

Industrial hoists & cranes


Overhead hoists


under
-
slung cranes


top
-
running cranes


jib cranes

Overhead manual chain hoists


Hand chain turns a
pocket wheel


1/2 to 60 ton capacity


suspended trolley

Overhead powered hoists


Electric or pneumatic powered


chain hoist or wire rope


reeving (wire rope)
-
passing a rope over the
sheaves , gains mechanical advantage


single reeved
-
1 rope, block moves horizontally
as the hook



double reeved=1 rope, both ends attached to
drum, load stays centered as hook

, can use
smaller rope, drum & sheaves

Overhead hoists 2


Parts
-

the number of rope lengths between
the drum & the hook


More parts = more mechanical advantage


operation
-
generally a push button control
pendant with


and an emergency stop
button


multi
-
speed control,


brake system


limit switch

Jib cranes or hoists


Can be wall mount or pedestal mount


fixed, partial rotation or full rotation


top braced, under
-
braced or cantilever


rotation type have bearings

Safety 1


Only 1 operator per hoist


only 1 boss per hoist
EXCEPT

for
STOP
!!


Do not side pull a load, this is very dangerous
-
do vertical lifts only

Overload limit devices


Keep hook from going too far up


prevent damage to unit when exceeding lift
capacity


are not a guarantee of safety

Bridge Cranes


A Bridge Crane system consists of three major
components.


the Bridge Crane, which traverses across the
runway


the hoist & trolley, which traverses across the
bridge and lifts up and down


the runway, which is tied to the building
structure.


Website


http://www.dearborncrane.com/pdf/bridge_c
ranes/Crane%20Description.pdf


Under
-
slung cranes


Hoist is suspended from 1 or more bridge
beams fitted with end trucks


smaller lift capacity than top
-
running cranes


used where ceiling space is limited

Top running cranes


Cranes are mounted on top of support beams,
run on rails


gantry cranes


semi
-
gantry cranes or half gantry cranes


operation
-
cab operated, pendant control,
radio control


the crane operator is
not

the rigger!!!!

Top Running or Under Running?


Top Running vs. Under Running is primarily
determined by two factors:


Capacity
-

Although under running can be up
to 25 ton capacity, the practical limit is more
like 15 tons and the economic sweet spot is 1
to 7.5 ton range.



Support Structure
-

Under running can be
suspended directly from the overhead steel
(for lighter cranes). Top running cranes will
require a bracket off the building support steel
(up to 10 tons capacity) or independent
columns for heavier capacities.



Top Running or Under Running?


The top running configuration is best used in
cases where the end user has issues with
headroom. The most space efficient
configuration is the double girder, top running
crane system. When headroom is not an issue
a top or under running configuration can be
used with either the double or single girder
bridge crane.


Top Running or Under Running?

Inspection


Inspect & service
periodically


trained personnel


as required by OSHA


hooks, cable, drum,
sheaves, contacts,
gear boxes, limit
switches, controls,
brakes, lube

Hand signals


Communication
between rigger &
crane operator


very important


only 1 rigger per job
except for STOP