Mumbai University > Electronics and telecommunication > Sem 7 > Applied Hydraulics

Marks: 08

Years: DEC 2014

Hydraulic crane is a device,used for raising or transferring heavy loads. It is widely used in workshop, warehouses and dock sidings.

A hydraulic crane consists of a mast,tie,jib,guide pulley and a jigger. The jib and tie are attached to the mast. The jib can be raised or lowered in order to decrease or increase the radius of action of the crane. The mast along with the jib can revolve about a vertical axis and thus the load attached to the rope can be transferred to any place within the area of the crane's action. The jigger, which consists of a movable ram sliding in a fixed cylinder, is used for lifting or lowering the heavy loads. One end of the ram is in contact with water and the other end is connected to set of movable pulley block. Another pulley block, called the fixed pulley block is attached to the fixed cylinder. The pulley block, attached to the ram,moves up and down while the pulley block, attached to the fixed cylinder is not having any movement.

A wire rope, one end of which is fixed to a movable pulley(which is attached to the sliding ram) is taken round all the pulleys of the two sets of the pulleys and finally passed over the guide pulley, attached to the jib as shown in fig. The other end of the rope is provided with a hook, for suspending the load.

For lifting the load by the crane, the water under high pressure is admitted into the cylinder of the jigger. This water forces the sliding ram to move vertically up. Due to the movement of the ram in the vertically up direction, the movable pulley block attached to the ram also moves upwards. This increases the distance between two pulley block and hence the wire passing over the guide pulley is pulled by the jigger. This raises the load attached to the hook.