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 Erstellt: 21.09.23, 03:03 Betreff: Julian Champkin explores the world of process cranes
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The metal-foundry industry combines hazardous environments of extreme heat, choking dust, hot metal and naked flame. Melt shops require heavy and dangerous loads to be transported; their cranes must be able to lift and carry buckets of liquid metal safely and reliably. The special conditions of a foundry demand special requirements of the cranes and hoists.
“These are workhorses,” says Rich Warriner, director of business development at Virginia Cranes. “Safety is paramount; and foundries operate 24 hours a day, seven days a week, so downtime is not wanted and ease of maintenance is a necessity.”
Turkish crane-makers BVS Cranes echoes and amplifies the point: “Generally in the metal foundry industry the melting shops operates continuously for three shifts 24 hours a day,” says Mehmet Erol, deputy general manager at BVS Cranes. “The environment is full of dust and the ambient temperature is up to 70–80°C. Therefore, cranes that are to work in metal foundries are specialised equipment with extremely critical pre-requisites. The process and melting shops of a foundry are some of the hardest places for the working of cranes.”
Heatproofing, redundancy, safety of operatives—generally nowadays increased by using remote control—and reliability and ease of maintenance are some of the more obvious requirements. Precision in handling is another. Technological advances in smart technology data recording and the like have enabled and improved many of these in recent years—and this in turn has led to productivity gains, and to sales.
“The metal foundry market has considerable growth potential because new technologies allow customers to save money and run their businesses in a more sustainable manner,” says Steve Gagnuss, senior vice president for industrial cranes at Konecranes APAC. “Konecranes’ metal process cranes are designed with smart features which reduce structural stress, increase efficiency and prolong equipment life. We see lots of potential, in the Asia- Pacific region in particular.”
The cranes involved go by the names of ladle cranes, charging cranes, teeming cranes and tundish cranes, according to their particular location and function in the foundry; but they have similarities and characteristics in common. They are usually overhead travelling cranes that are fitted with special attachments to lift the giant ladles that contain liquid metal. They often perform more than one function and are used as backup for each other. Auxiliary hoists can be attached for scrap charging and maintenance functions, such as cleaning the empty ladles or lifting the furnace shell.
Gagnuss explains the processes involved: “The ingredients for steel come from two main sources: original raw materials—iron ore and coking coal—and scrap. These are treated separately in the foundry. Iron ore and coking coal are combined in a furnace in a direct reduction process to produce metallic iron. The melted iron is mixed with scrap to create molten steel.
“The scrap, transported from a scrapyard, is loaded into the furnace by an overhead charging crane. The main hoisting machinery lifts the bucket to the furnace for melting. An auxiliary hoist on the crane opens and closes the bucket during loading.”
BVS Cranes says: “Charging cranes are used for feeding scrap to the arc furnace. Ladle handlers are used for transferring molten metal, at a temperature of 1500- 1600°C, then returning the empty pots for re-charging.
“So these two type of cranes are the most critical equipment in melting shops. Any crane failure would mean that steel manufacturing would have to stop at the facility. This means that the charging cranes and ladle handlers have to be manufactured to the highest standards, and the highest class of safety factors has to be incorporated. Security and safety are always in the foreground.”
The worst nightmare, of course, would be a ladle full of molten metal dropped from a height. An unmovable ladle of molten metal jammed overhead is also to be avoided. “If it cools to the point of solidifying, you have lost the metal and your ladle as well,” says Warriner. For these reasons multiple layers of redundancies are built into foundry process cranes.
“The national code in the US demands two sets of holding brakes, wire rope strength of an 8:1 safety factor, and that is pretty much all it demands,” says Warriner. “But best practice is more rigorous and application specific.”
Elsewhere regulations are more prescriptive. “They vary between regions and countries,” says Gagnuss, “but the overarching theme that guides them is safety. Typical regulations in the crane industry outline safe use, inspection and maintenance requirements, and design working periods.
“In Australia, for example, over the last five years the standards have been updated to include the requirement to ascertain the remaining design working period (DWP) according to processes and calculations summarised in a new section (9) of AS2550.1. DWP is then used to determine when a major inspection and subsequent general overhaul is due. Similar standards apply throughout Asia.
“The biggest problem here is radiant heat rather than ambient heat,” he explains. “So you need heatshields around the hook and the bottom block, and underneath the controls. Almost all these cranes are radiocontrolled. There are not too many cab
Julian Champkin explores the world of process cranes
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