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9. CHARGING & PREHEATING SYSTEMS
The use of drying and preheating systems and remote charging systems can significantly reduce accidents related to furnace charging operations. However, it does not eliminate the need for personal protective equipment. Many serious foundry accidents occur during furnace charging when foundry workers come in close proximity to the molten bath. Splashes caused by dropping large pieces of scrap and water/molten metal explosions caused by wet or damp scrap can be reduced through the use of drying and preheating systems and remotely-controlled charging systems. These systems, however, cannot remove trapped liquids, such as oil in cans. Such materials must be shredded and dried before they are used. ________________________________________________ Drying & Preheating Systems Drying & preheating systems pass scrap through an oil or gas fueled flame tunnel, heating the scrap and minimizing the moisture that could cause a water/molten metal explosion. These systems also burn off oil, producing a cleaner charge and reducing the energy required in the furnace to melt the scrap. Scrap dryers must be used with any heel melting furnace and any application when scrap is introduced into a pool of molten metal.
Gas or oil fired charge dryers and preheating systems dry surface moisture on the charge before it enters the furnace. ________________________________________________ Charging Systems
Charging systems include belt and vibratory conveyors, charge buckets and chutes. They significantly enhance safety by permitting furnaces to be charged remotely, keeping the foundry worker at a distance or behind protective barriers. Care should be taken so that the charge continues to feed into the molten pool properly. If it hangs up due to interlocking or bridging, superheating below can erode the refractory, causing molten metal to penetrate to the coil. This results in loss of the lining and represents a very dangerous condition. Should the molten metal burn through the coil, the water in the coil can cause an explosion, causing possibly fatal injuries. All charging systems involve moving equipment that can cause injury or death. This equipment may include charge cars that pivot and/or travel across the melt deck, magnets and charge buckets carried by overhead ranes and operating belt conveyors. You must be alert to the path moving equipment follows and stay out of that path during operation. Being struck by moving equipment can cause injury or death.
When a pivoting conveyor or other automated system is used to charge a furnace, the operator can stay safely back or behind a protective barrier. ________________________________________________ Moving Equipment Presents Trapping Hazard In foundries, as in many manufacturing operations, moving equipment poses a trapping hazard to the unwary. “Trapping” is the term for the situation where part or all of a worker’s body becomes caught between moving equipment and another object or structure. Trapping also includes situations where a worker’s limbs or clothing get caught in or on moving equipment. Trapping can result in injury or death. The loss of a limb or limbs is a common injury in trapping accidents. Trapping hazards on the melt deck may include moving charge buckets carried by overhead cranes, traversing or pivoting charge conveyors, belt conveyors, moving ladles and tilting furnaces.
Induction furnaces tilt forward to pour and then return to the upright position for charging and melting. While in motion, they can pose special hazards for foundry workers. One preventable accident occurs if a foundry worker’s foot becomes trapped between a descending furnace back platform and the working deck. A foundry worker must know the path a furnace or other piece of mobile equipment will travel when it is set into motion and remain behind designated safety barriers until the machine completes its duty cycle and returns to its normal resting position. Trapping also is a hazard during maintenance operations, when workers must be within a piece of equipment’s motion path. That’s why special steps must be taken to disable the equipment electrically (lock out power) and secure it mechanically before maintenance work begins. In a foundry, this is particularly true of furnaces.
If work is to be performed on a tilted furnace, the furnace must be secured in the tilted position with a mechanical support. Reliance on hydraulics alone could lead to the furnace dropping without warning, causing injury or death to anyone trapped underneath. Charge conveyors and buckets can traverse across the melt deck and index forward to the furnaces. Workers must be alert and remain clear of all moving equipment.
A charge bucket carried by an overhead crane drops its charge materials into a charge car. ________________________________________________ IMPORTANT: |
