GH Cranes, headquartered in Spain, makes cranes for furnace charging and ladle handling, and casting and tundish cranes. Mostafa Salehi, the company’s area sales manager, explains the requirements of the manufacturing process.
We follow the EN 13135 standard, which in general means that safety is the key. It demands redundancy in all critical systems.
So we design our hoist drive with redundancy as fundamental. The main hoist mechanism consists of a double closed kinematic chain with two drums, two motors and two planetary gearboxes. The planetary gearboxes are manufactured in our factory. There is double independent drive in cross travel motion, and fourfold independent drive longitudinal ly.
Each motor is furnished with two electrohydraulic service disc brakes. There is double braking. The rope reeving system prevents the load from falling even in the case of failure of one of the ropes.
A special coupling with a torque detector is installed between the two drums in order to close the kinematic chain. This guarantees that in the case of a failure of a shaft, coupling, gearbox or motor the load will not fall and it will be possible to continue working and transport it to its proper destination.
Electrical robustness and redundancy are equally important. We have standby frequency inverters in all the motion generators, and a standby air conditioning unit in the electrical panel room. For protection against heat all the electrical components are installed inside the main girder, the whole inner surface of which is thermally isolated with layers of rock wool.
Temperatures in foundries are extreme, and operator comfort is also fundamental to safety. Protection against thermal radiation is essential. For proper protection to the cabin the windows are double glazed. There is an emergency exit separate from the normal one and, based on special risk analysis for each individual case, thermal shields may be ftted above or in front of the cabin.
Minimum safety margins on rope strengths are 8 or 9; the single fail proof design means that if one rope fails the ladle remains on the crane. Hooks also are to a single fail proof design. The “J” hooks are adaptable for diferent loads—scrap bucket, ladle, and so on—and again if one hook fails the ladle remains on the crane.
Specifictions for these cranes are for 24-hour continuous operation, but of course they need maintenance. During maintenance times another crane of equal capacity and safety features moves the molten metal.