CENTRAL CRANE MAINTENANCE

          This division takes care of the cranes used in the rolling mill only. The cranes employed in the rolling mills are Electric Overhead Travel cranes of commonly known as EOT cranes. The other type of crane in use is the Vertical Ingot Charger or VIC. Central Crain Maintenance takes care of the mechanical maintenance and the structural part whereas the motors are maintained by the electrical maintenance division. The crane in operation varies in the capacity from 3 T to 75 T. And total number of cranes in operation in the whole of rolling mills are 52 cranes. The cranes in operation are both single hoist and double hoist. In case of single hoist there is only one hoist and in case of double hoist two hooks are there, which are operated simultaneously and the capacity of the crane is given by the sum of the capacity of each of the hoists which are equal. There are a few cranes with a main and auxiliary hoist, and they can be operated separately, and their capacity differs. The terms used in the reference of the cranes are:

·        LT or long travel – this motion takes place along the bay

·        CT or cross travel – this motion takes place across the bay.

The third kind of drive is the hoist drive.

          The assembly of the crane consists of a girder under which wheels are fixed, the trolley or the cabin. And the hoist consisting of the pulley, hooks & the ropes. The ropes used are the metal wire ropes, stranded together and wound across a fiber core. But in case of a VIC, mast like structure is used. It can be rotated through 360⁰ in both clock wise and anti clock wise direction. It has got two jaws at the end of the mast, which is used to grip the ingot and then place it in the ingot feed car. The drive is given by a motor and very simple mechanism is employed. Most of the gears used are worm wheel type. The maintenance work involves weekly greasing, recharging of gear oil and replacement of the worm out parts and also conditional repair.

          The safe working load is the parameter used to determine safety. Factor of safety is kept very high for the hooks and pulley ropes.