12-09-2013, 02:44 PM
HYDRAULIC CRANE
HYDRAULIC CRANE.pptx (Size: 209.09 KB / Downloads: 239)
It is a device which is used for lifting heavy load ( upto 25MN). It is widely used in docks for loading and unloading ships, warehouses , foundary workshops and heavy industries.
CONSTRUCTION
It consists of a crane and a hydraulic jigger.
The crane has a central mast from which a tie and a jib are fixed.
The hydraulic jigger consists of a cylinder and a ram at the and of which pulleys are attached.
The pulleys enable to increase the velocity ratio between the wire rope and the ram.
The load can be lifted and moved around the crane area depending upon the length of the jib.
The load is suspended by a wire rope which passes over a pulley at the end of the jib and over the tie-rod to the hydraulic jigger.
WORKING
When the load is to be lifted by the crane ,liquid under Pressure is admitted to the cylinder of the jigger; the liquid forces the sliding ram to move vertically up.
The distance between the two pulley blocks increases, the wire or rope is pulled and the load is lifted up.
As the liquid leaves the cylinder, the distance between the two sets of pulleys decreases which results in releasing more length of wire rope and the load gets lowered.
The lifting speed of modern hydraulic crane may be about 75m per minute.