Jib crane consists of an inclined member supported by
a rope or any other type of structural member attached to a vertical
mast or frame. Load is usually suspended from the outer end of this
inclined mast. The outreach of the jib may be fixed or variable. The
cranes as a whole may be either fixed or moveable. Various
sub-classification of these cranes are possible.
Lifting
capacity of such cranes may vary from 1/2 ton to 200 ton and outreach
from a few meter to 50 meter. Such cranes find various applications in
port area, construction site, and other outdoor works.
For handling general cargo, lifting capacities are usually 1 1/2 ton to 5 ton with maximum outreach of 30 meter. Jib
Cranes provided with grabbing facilities have usually a capacity
ranging from 3 to 20 tons operating 50 to 100 cycles per hour. Lifting
heights may be 30 meters or more.
Jib crane used
in ship yards for lifting heavy machinery and equipment, weighing 100 to
300 tons, are usually mounted on pontoons. Frequently these cranes are
provided with two main hoisting winches which can be employed singly or
together to lift a load. For handling light loads these cranes may have
auxiliary arrangement.
Types Of Jib Crane:
Depending on the use, jib cranes are classified into a number of varieties, primarily on the basis of their mountings.
These are:
- Hand Operated Scotch Derrick Type
- Wall Mounted Jib crane
- Portal / Semi-portal cranes of different varieties-Wharf cranes
- Mobile jib cranes consisting of truck mounted and crawler mounted cranes
Scotch Derrick Type / Wall Cranes:
Wall
cranes are used in ware houses for handling light weight and when there
is little or no wharf between them and the water front. Slewing or
rotational motion of the crane is possible within restricted angle and
the motion is slow. Hoisting and lifting speeds are comparable to those
of wharf cranes. In some modified version these cranes can have
travelling speed along the wall.
Wharf Cranes:
These
are used in shipyard and port for handling unit and bulk load. These
are usually self propelled balanced level luffing type with full circle
slewing motion facility. Wharf cranes may be of different types,
depending on the type of structure on which it is mounted. The choice
of structure for mounting depends on site condition.
The principal types of wharf cranes are:
- High pedestal
- Full Portal
- Semi-portal
Portal Cranes:
Portal
crane is a fixed or revolving type jib crane mounted on a portal frame
fixed in location or arranged to travel along a fixed track of rails at
the same level. The portal frame consists essentially of horizontal
girders connected at both ends to vertical or inclined member’s having
equal lengths.
Semi portal Crane:
Semi
portal crane is a fixed or revolving type jib crane mounted on a semi
portal frame fixed in location or arranged to travel along a fixed track
or rails at different levels. The semi portal frame essentially
consists of horizontal girders connected at both ends to vertical or
inclined members which constitute a shorter side and a longer side. The
shorter members may consist only of the trolley running along the
elevated rail.
Mobile crane:
Mobile
Crane ( Power Driven ) includes all type of travelling jib cranes, such
as truck mounted, crawler mounted, locomotive crane on rails.
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