There’s also the battle against the mill’s own newness. In an industry that values history and experience, the game plan of an upstart mill has to be different. This means finding creative and innovative solutions that buck tradition and enhance production.
Such is the case of SeverCorr, Columbus, Miss., a brand-new steel coil manufacturer set on 300 acres in northwest Mississippi, and its decision to streamline its material handling needs by using only one charge crane and one ladle crane per production bay, as opposed to the more common setup of two for each. In doing this, the cranes had to be built not only to the Class F standards of the Crane Manufacturers Association of America (CMAA) but also with upgraded specs, redundancies and additional spare parts so they could withstand intense, nonstop operating schedules. Enhancing the P&H-brand cranes, manufactured by Morris Material Handling Inc., Oak Creek, Wis., a supplier of overhead cranes and maintenance service for steel mills, was a tradition-bucking move SeverCorr welcomed.
"Morris Material Handling suggested that we use upgraded equipment to improve efficiency and the lifespan of the equipment," says Stuart Driskell, crane maintenance supervisor at SeverCorr. "The original plan of SeverCorr would’ve included four cranes with lower capacities. By increasing the specs of the cranes, we could greatly reduce the risk of expensive downtime."
Much to move
It’s obvious just by looking at the size of its facility (which is still under construction) that SeverCorr means business. With a 1.5-million-ton capacity that includes a state-of-the-art melt shop, thin slab caster, six-stand hot mill, cold mill and a hot-dip galvanizing/galvannealing line, and a steel mix that includes commercial, drawing, deep drawing, extra deep drawing, interstitial, structural, high strength low alloy and carbon steels, SeverCorr is already aiming high. This means efficiency and cost savings are at a premium, and the company’s design team, in conjunction with Morris Material Handling, found a way to cut material handling costs by eliminating unnecessary cranes.
"Although each of the AIST-spec cranes [SeverCorr] installed cost about 20 percent more than a less-robust CMAA crane, they only purchased two in their initial build phase, rather than their original intention to purchase four--saving a considerable sum," said Ray Greene, account manager for Morris Material Handling, in a press release.
SeverCorr melts a variety of scrap, meaning a charge crane is needed to transport the scrap materials to the electric arc furnace. The ladle crane is then needed to carry the molten steel through the ladle metallurgy furnace, which refines the metal’s chemistry and temperature. The ladle crane then takes the batch to a turret that sends it to the caster process.
The P&H cranes, built and installed in 2006, have a 450-ton load capacity but rarely handle more than 300 tons at a time. By not running at full capacity--although the company still averages 4,000 tons in daily output--the crane parts are designed and manufactured to last longer and require less maintenance.
SeverCorr runs two 12-hour shifts every day of the week, with the only downtime for the cranes being a weekly four-hour preventative maintenance check. To ensure these single cranes don’t break down prematurely, Morris Material Handling equipped them with alternating current (AC) variable frequency controls as opposed to the more common direct current controls typically used on similarly sized cranes. This marked the first time 450-ton AC adjustable-frequency melt shop cranes had been built in the United States.
Usually, AC controls are featured on smaller cranes because they’re able to operate on a single inverter. But as technology advances and more inverters and motors are able to be implemented, AC-controlled cranes are able to accommodate larger loads.
Cranes with AC controls also run without brushes, slip rings and comutators, reducing maintenance and eliminating the need for those spare parts. Brake pads also get a break, as an AC crane uses its inverter to stop the load, whereas in DC cranes, the brakes do the stopping. When you have cranes running at 29 feet per minute with trolley speeds of 150 feet per minute, as SeverCorr’s P&H cranes do, this adds up to an enormous relief on the brakes.
Morris Material Handling also went one step further and manufactured its cranes with three hoist motors instead of the standard two, which is perhaps the most notable of their integrated redundancies. If one motor breaks down, the other two will take over, operating at a reduced speed and ensuring production continues and that there aren’t any precarious scenarios in which a ladle brimming with molten steel is stalled and dangling above the production floor.
The idea of duplicate motors instead of duplicate cranes also extends to Morris Material Handling’s implementation of dual motors in the cranes’ auxiliary hoist drive, as well as adding an extra motor to its trolley unit.
Up, up and away
Developing these souped-up cranes was a collaborative process, one in which SeverCorr depended on open communication with Morris Material Handling.
"Morris Material Handling was great to work with," says Driskell. "During every part of the [building] process, their people were accommodating and helpful. They recognized our needs and responded accurately to them."
Additionally, well-trained operators and service technicians are key components of a reliable operation and, for this, SeverCorr uses the Morris Material Handling Institute for training.
Driskell says that if ever an issue comes up with the cranes, a representative from Morris Material Handling has quickly responded. In fact, having had such a positive experience with both the cranes and their manufacturer, SeverCorr is planning an expansion, set for completion in August 2009, that will entail purchasing two more cranes to produce twice as many steel coils.
"The addition of the new cranes will help SeverCorr to double productivity," says Driskell. "SeverCorr will be able to move 8,000 tons of steel roll coils per day, which will equate to 3 million tons per year."
Although SeverCorr is in its infancy as a company, its penchant for finding unique solutions to its growing production needs and enhancing its capabilities suggests it won’t be stalled and left to dangle anytime soon. MM