America's best induction meltshops.
Part of the mission of modern casting over the years has been to introduce the industry to itself - to highlight unique foundries making strides in technology or sales/marketing or in human resources. Yet it isn't often that in these pages you'll read an operation boldly described as "the best." Until now, that is.
For this article, we isolated a specific category of foundry operation - iron job shops using induction melting - and asked leading induction equipment suppliers to nominate plants that have implemented cutting edge technology, creative engineering and a lot of common sense to make their meltshops as efficient as possible.
But how do you judge what's best? Any given foundry might conceivably do at least one thing better than any of its competitors. Clearly, there must be a set of criteria. In the article on page 28, the AFS Coreless Induction Committee (8-C) discussed the ideal meltshop given current technology. based on this and other input from experts, a framework for judging a state-of-the-art meltshop was developed. The following criteria were given to furnace equipment suppliers, and their nominations were selected accordingly.
* Capacity - The ability to provide as much metal as is needed, and to step up production, if necessary.
* Flexibility - If more than one alloy is poured, how quickly is the transition made? Batch melting, the complete emptying of the furnace on tapping, aids furnace flexibility of this type.
Flexibility also includes the "frequency and extent of upgrades to keep a furnace on a par with current technology," said consultant Ronald Stark, South Harwich, Massachusetts. "Many induction furnaces in use today, particularly of the channel type, were manufactured between 1968-1978, and their electrical equipment is antiquated by today's standards. That doesn't mean they need to be replaced, just that considerable improvement can be made in both reliability and performance by upgrading the control sections of the furnace."
* Layout - The physical flow of metal through the shop, the holding and handling equipment, the proximity of melting to pouring, etc. A well-thought-out meltshop saves time and labor by eliminating extra steps, provides a clean, uncluttered work environment and simplifies the tracking of heats.
* Electric Power Usage - It has been estimated that energy use represents the major portion of a foundry's controllable costs. Induction melting undeniably uses quite a bit of electric energy, and often foundries are required to work out creative billing arrangements with local utilities. According to John Svoboda, Process Metallurgy International, Inc., Arlington Heights, Illinois, "Various rates such as off-peak, time-of-use, real-time pricing, interruptible and metal-melting rates have been developed by different utilities specifically to meet the needs of foundry customers. These should be used to realize the lowest cost."
The equipment itself can help control and optimize energy usage, Svoboda said. "The popular systems using two batch operated furnaces and a single power supply easily achieves a maximum power utilization of 80% or more," he explained, "and the addition of induction-heated pouring furnaces raises that efficiency to nearly 100%."
* Control Technology - Modern induction equipment no longer includes massive control cabinets taking up space on the foundry floor. And, as the footprints have shrunk, the capabilities have expanded. Modern meltshops can now control more than the kW going into the furnace. PLC can provide automatic temperature measurement and automated melt chemistry checks. Historical data can be retained and it is now possible to track furnace operation over time, aiding in both the quality assurance and maintenance functions. Stark said that various forms of monitoring devices can help predict and prevent refractory failure to extend on-line life and improve the value obtained from the refractory.
* Safety/Pollution Control - Svoboda noted that the high power-density, medium-frequency coreless induction furnaces - widely considered today's benchmark melting units - are equipped with closed-loop cooling systems that eliminate the discharge of water into municipal sewers. They also "normally include ring-type close-capture dust collection systems to meet current environmental requirements," he said.
To a degree, the amount of automation reflects the on-the-job safety of meltshop employees. Equipment for refractory lining replacement, automated charging/alloying, and other enhancements can avoid common ergonomic problems.
With these considerations in mind, the following foundries were nominated as America's best induction meltshops.
Waupaca Foundry Inc. Plant 4, Marinette, Wisconsin
Metal Cast: Ductile Iron
Markets Served: Automotive, Heavy Truck, Agricultural
Melt Tonnage: 27,000-31,000 tons/month
Meltshop Employees: 20 per shift, 3 shifts
About 11 years ago, Waupaca's 150-employee Plant 4, which had always exclusively poured gray iron, began producing 50% of its castings in ductile iron. By late 1990, Plant 4 was 100% ductile iron, with a meltshop that included five melting furnaces and two pressure pour furnaces. Since then, the meltshop has changed dramatically.
A tour of the meltshop begins in the huge indoor scrap yard. Two 5-ton overhead cranes select and weigh the steel, pig iron and remelt for each pearlitic or ferritic charge before placing it onto a vibratory conveyor. The conveyor transports the 4-ton charge to one of three preheat stations. At each station there are two indexing charge buckets. The full charge bucket moves under a 23 million BTU, gas-fired, open flame preheater, and the charge is fired from the top and exhausted out the bottom of the bucket. After a cycle of 8.5 min, the bucket's contents are at about 1000F (537C).
Preheating began last July, and is proving beneficial in two aspects. "Preheating has completely eliminated the explosions we'd get occasionally from magnet-charging cold scrap," said Brickey, "and we found we get a 10% increase in melt rate."
One of two cranes (16-ton or 7-ton) places the preheated charge bucket on the appropriate furnace. Of the nine vertical channel melters rated 3000-4500 kW, six were built by Inductotherm, two by Duca Manufacturing, and one by Waupaca. All of them, however, are distinctive to Waupaca. To increase the melt rate and eliminate runout and inductor plugging problems caused by melting ductile base iron, Waupaca and Duca Manufacturing made major design changes to the power cabinets and inductors. All the transformers were replaced with 7500 kVA units in order to achieve 4500 kW. The furnace refractory system was also overhauled to accommodate silicon carbide-bearing brick from Chicago/Wellsville Firebrick Cos.
The results of these improvements are dramatic. "Ten years ago," Brickey said, "3000 tons of throughput of melted iron was the average inductor life on a furnace. We now get 60,000 tons of life - and that's melting at maximum power 24 hr per day." The furnaces can run up to 18 mos without a feline (nine times the industry average, according to Duca Manufacturing President William Duca) and almost no refractory maintenance.
Producing about 55 ton/hr, the furnaces tap, at 2650F (1554C). When a 4500 kW furnace is at tap temperature, it must be cut back to holding power because the metal temperature will increase 10F per minute at full power. Every 9 min one of the furnaces taps into a 4-ton tundish treatment ladle, handled by three overhead hot metal carriers, which are electric-powered with a diesel backup system.
The hot metal handlers then transport the iron to one of six-pressure pour furnaces. These units were designed and built by Waupaca, and feature Duca power supplies with 450 kW throatless inductors. They feed six Disamatic molding lines. The durability of the pressure pours is also remarkable. Inductor life averages about 3 years. (Again, Duca said this life span is 9-12 times the industry average.)
The nerve center of the operation is the control room. From here, one operator commands all 9 melting furnaces and all 6 pressure-pours. All relevant furnace statistics and information are displayed graphically and, based on this data, the operator directs operations.
As stated above, melting takes place 24 hr per day, and it consumes about 400 kW per ton of melted iron. Waupaca pays the same amount per kW during the day as it does at night. This is because of an agreement with the utility whereby the foundry agreed to have its power reduced when emergency shortages occur - a situation that has arisen only a few times in ten years.
Now employing 600 people, Plant 4 is still looking at expansion with a project to begin this year. When that project is complete, Brickey predicts the shop's top capacity will be 2000 tons per day, but will melt 1500-1600 tons daily. "We've been pushing inductor technology these past 10 years to see what's on the other side," he said. "We're still pushing today."
Benton Foundry, Inc., Benton Pennsylvania
Metal Cast: Gray and Ductile Iron
Markets Served: Agricultural, Construction, General Industrial
Melt Tonnage: 2500 ton/month
Meltshop Employees: 4 per 10-hr shift (plus 5-6 pourers), 2 shifts
In 1989, 275-employee Benton Foundry was a gray iron shop using a late 1940s vintage cupola to supply its green sand molding lines. "We'd experienced two years of double digit growth" said President Fritz Hall, "and it was conceivable that in the near future, the molding lines would be waiting for iron." Also, the growing ductile iron market beckoned and environmental regulations were tightening. The dust collectors for the cupola dated back to the 1920s, and the wet scrubber was a costly, high-maintenance system. The cupola itself had to be dropped and relined daily.
In 1991, the cupola was still there, but two 4-ton induction furnaces were now in operation nearby, producing ductile iron. "The money was going to be spent regardless, and induction would allow us to work into ductile iron," Hall said. "The plan was to eventually replace the cupola entirely, but we had to walk before we ran. Our people had no experience with induction melting, and this was a way to make a very smooth transition."
By July 1996, the cupola had finally been tom out to make room for two more induction furnaces and their accompanying equipment. To accommodate them, Benton began constructing a 20,000 sq ft addition to the plant. This would be the new meltshop, but it would be months before it was operational, and the foundry had lost a lot of capacity. The two original induction units began pumping out more than 100 tons of iron every day in two 10-hr shifts. "We had a 95% on-time delivery record," Hall said, "and we wanted to keep it." So Benton pulled its salesmen off the road and refused to quote any new work for the whole transition period. "It was no time to be hoggish. I wanted to come out of this with the same customers I started with," Hall laughed.
The completed induction meltshop began operation January 1, 1997. The $7 million spent since 1989 has resulted in a cutting-edge melting facility with quality-intensive operations.
Benton's scrap and pig iron suppliers must go through a rigorous approval process, and their products are required to meet stringent written specifications. All purchased metallics arrive presorted and are delivered right into roofed storage bins. Charge is picked from these bins by a 10-ton overhead bridge crane with magnet and load cells. There is also an auxiliary crane as a backup.
At this point (for the purpose of explanation only), the meltshop splits into two distinct operations, with one metal stream flowing through the 1991 Project equipment, and the other through its 1997 counterpart.
1991 Installation - The charge is run through a 2000 lb, 27-cu ft, gas-fired Inductotherm-Vanetta preheater, exiting into a bucket that is transported via a 7.5-ton monorail crane to the melt deck. Here, the charge is deposited into a vibratory swivel feeder, which charges it into either of the two 4-ton Inductotherm furnaces. The furnaces are powered by a 2500 kW powerpack, and each accepts a 5000-lb charge.
1997 Installation - The scrap goes through a 3500 lb, 60-cu ft Inductotherm-Vanetta preheater and then into a charge bucket. The bucket is transported via a 15-ton crane to the melt deck, where the charge is loaded into a rail-mounted transverse indexing vibratory feeder. The feeder deposits up to 10,000 lb of metal into either of the two 10-ton Inductotherm coreless furnaces. The furnaces are run off a 7000 kW Dualtrack power supply.
All four furnaces share one melt deck and sit in a row in the meltshop. For refractory relines, each has lining pushout capabilities, and they share a 3-ton overhead monorail crane for setting forms, starter blocks, etc. The two 1997 furnaces have back slaggers. Chemistries, temperatures and weight are displayed above each furnace. The furnaces are heel-melted on load cells via a VIP Meltminder. Iron is tapped into 1500-lb ladle cars that double as tundish (ductile) or transfer (gray) ladles. The metal is then distributed into 500- and 700-lb pouring ladles.
The foundry's melting energy costs approach 500 kW per ton. To provide the electricity for an operation of this size, Pennsylvania Power & Light ran 15 miles of 69 KVA line to Benton's newly constructed substation. The foundry is also on a pilot program with 24 other large energy users in the utility's grid, and thus pays a price significantly cheaper than standard large power user rates.
The foundry now produces nearly 150 tons of iron per day (30% of which is ductile), with total capacity of 300 tons per day. "Iron availability is no longer an issue," Hall said, "and it won't be for the next few years." He also said the cost structure of the melt area has been stabilized, and quality is more consistent. Since all the furnaces have closed-loop cooling systems, there is no discharge water, and the close-capture dust collectors have significantly reduced air emissions. Furthermore, because only four workers are required per shift, the induction operation has eliminated problems and labor inefficiencies, and maintenance costs have dropped as well.
J.B. Foote Foundry Co., Inc., Fredericktown, Ohio
Metal Cast: Gray and Ductile Iron
Markets Served: Pump, Valve and Energy
Melt Tonnage: 3000 ton/month
Meltshop Employees: 7 (including pourers)
When Tom Updike bought J.B. Foote in 1987, the foundry's most recent modernization had been in the 1940s. This month, the company completes a $4.98 million expansion that included building an entirely new foundry onto the existing plant. The revamp included nearly all the foundry's operations, including the melting department.
Originally, the J.B. Foote was using an ancient Whiting cupola to melt gray iron. But Updike wanted to expand into ductile iron, and the cupola's melt zone wasn't deep enough to process the base iron. That fact, as well as the cost of operation and environmental considerations, led the company to install two 4000 lb medium frequency Ajax induction furnaces.
It was clear, however, that those furnaces wouldn't be able to support J.B. Foote's operations indefinitely. "Our expansion increased our molding capabilities to a great degree," Updike said, "and we needed more melting capacity." With the foundry expansion, melting remained in the old foundry building. Metal charge, however, has a new space all to itself.
Called the scrap building, all metal charge is stored in a facility built during the expansion. Interestingly, the company opted to spend money on raw materials rather than equipment when it comes to what it feeds its furnace. J.B. Foote buys only certified, predried steel punchings, supplemented with internal foundry returns and virgin pig iron for gray iron and low-sulfur pig iron for ductile iron melting. The punchings are guaranteed free of moisture and oil. "We buy it dry and clean, and we keep it dry and clean," Updike said. "So we get very good results without using a preheater."
Scrap is picked out by an overhead crane with a magnet and carried to an oscillating weighing unit, where the proper charge makeup is formulated. The completed charge is then vibrated off of the weighing unit into a 1500-lb charge bucket sitting in a "charge pit." Because the melt area is in the old part of the foundry, and thus has limited overhead space, some creative engineering was required to design an efficient charging system. The solution was provided in a joint project by Ajax Magnethermic and Ely Crane. The charge bucket is lifted via a hoist and moved along a laser-guided overhead track until it is over the furnace. The charge bucket has a clamshell bottom operated by a pendant control that allows the charge to be "sprinkled" into the furnace. Because the foundry heel melts, the sprinkling helps reduce molten metal splash, and protects the lining from serious injury.
The foundry's two new furnaces are 3-ton Ajax coreless induction units operated off an 1120 kW dual power source. On the first heat of the day, the furnaces are able to go from ambient temperature to tap in 80 min, and the melt cycle is only 60 min for subsequent heats. "We've found that if we leave a very small heel in the furnace after tap - maybe 4 or 5 in. of metal - we speed melt times considerably," said Updike.
J.B. Foote is just completing installation of another 3-ton Ajax furnace with a 1500 kW powerpack. This will allow a combination of either furnaces 1-2 or 2-3 to be run at any one time, with the other furnace in reserve. Lining life is extended quite a bit by alternating furnaces each day.
Metal is taken away from the furnaces in 1000-2000 lb ladles mounted on ladle cars. Ductile iron (now about 30% of the foundry's production) is made using the sandwich method. The ladles are slagged before the iron is transferred to pouring ladles. "We're not large enough to use a holding furnace," Updike said. "We want to get the metal to the pouring lines as quickly as possible."
An Eta 105,000 CFM pollution and dust control system with individual hoods for each furnace and tap area has been installed in the meltshop as part of the expansion. "Nothing gets into the atmosphere until it's been processed through that," Updike said. The furnaces are on an Evapco closed loop cooling system that includes one auxiliary pump and one that will inject city water into the system in the event of an emergency. There are pits in front of each furnace so the iron can be dumped, if necessary.
The foundry boasts an excellent relationship with its local utility. To help power the expansion, a substation was built in Fredericktown, and J.B. Foote has been able to pay off-peak rates for the on-peak melting - the melt shop operates one shift per day, from 6 a.m-2 p.m.
Romac Industries Foundry Div., Sultan, Washington
Metal Cast: Ductile Iron
Markets Served: Water Works Industry (couplings, rings, flanges, etc.)
Melt Tonnage: 625/month
Meltshop Employees: 15
Now in its 29th year, the foundry division of Romac Industries is in the process of completing a massive foundry modernization and expansion project. In the course of the project, the meltshop, which makes strictly 65-45-12 ductile iron for Romac's olivine sand molds, has expanded in total space from 3000 to 9500 sq ft. According to General Manager Bart Walker, the shop previously held a 1-ton/hr coreless induction furnace running four days a week in two 10-hr shifts. "It served us well," he said, "but we needed more metal." Demand was ramping up, and modernization was necessary to keep pace.
Although the modernization is continuing, the $2 million meltshop (designed by Venetta Engineering and Romac project engineer Bill Brown) was completed in January 1997. All charge material is stored indoors and is serviced by a 7.5-ton bridge crane. The crane brings the metal to either of two 12,000-lb VibraPro vibratory hoppers on the trim deck. The hoppers are on load cells to provide a digital readout of weight as the charge is built. When the charge is complete, the PLC-controlled hoppers advance on rails to the furnaces, where the charge is deposited.
The new furnaces are two 6-ton ABB IFM4 coreless induction units run on a 4000 kW Twin Power shared-power supply. This arrangement allows Romac to batch melt, since the power can be shared between the furnaces in any desired amount. Thus, meltshop employees can charge one empty furnace while holding and tapping from the other.
Walker said that batch melting has two main advantages for Romac. "First, we get increased electrical conversion efficiency," he said, explaining that for a coreless induction furnace, the greatest electrical efficiency is achieved when the unit is melting, not when it is holding. "Second, we no longer need to preheat our charge because we're adding it to a dry furnace." By the time the metal begins to liquify in the furnace, any moisture in the scrap has been evaporated.
"The power-sharing ability of our furnaces now allows us to pour continually," Walker said. "Previously, we had to wait for the single furnace to come up to temperature. This is like the difference between hopping and walking." In addition, the furnaces themselves are more energy-efficient than the old melter, and Walker said that kWh consumption per lb of metal melted has improved about 15%. They are also flexible: "Our local power company called and requested that we change the ramp-up time for full furnace power from 2 sec to 20 sec, and all that was required was a simple program change to the furnace PLCs," Walker said.
Hot metal is tapped from the furnaces into 1500-lb tundish ladles for treatment and moved on a monorail loop. The metal is then transferred to pouring ladles and post inoculant is added manually (although this step will soon be automated). The pouring ladles then go either to the new Disamatic Mark V-B vertical flaskless molding line or to the cope and drag/Beardley & Piper Matchblowmatic flaskless mold pouring area. At the Disa line, a unique pouring arrangement has been adopted using two ladles pouring at intervals along the line, helping to maximize efficiency. However, the final step in the melthop modernization will be the September addition of an ABB Press Pour automatic pouring furnace with a Selcom laser control system.
Melting operations are controlled from an office above the melt deck housing an ABB melt processor, which provides graphic and digital data on charge weight, furnace temperature and power levels. The furnace power supply is located in a vault beneath the melt deck. Romac has also invested more than $100,000 in its metal and sand labs for quality control.
Though only operating at 40% of its total 17,500 ton/year melting capacity, Romac's productivity has improved so much that the foundry now runs only one shift, and is considering expanding into more jobbing markets with its free shift. Walker also noted a paradigm shift at the foundry. "Previously, the metal had to come to the molds; if the molds weren't ready, the metal would wait," he said. "Now, the molds have to come to the metal, and the metal must be ready." And it is. 'The furnaces are so reliable that we get to concentrate on the more elusive aspects of making good castings."
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|Title Annotation:||iron foundries|
|Author:||Philbin, Matthew L.|
|Date:||Jul 1, 1997|
|Previous Article:||Dreaming up the ideal meltshop.|
|Next Article:||Waupaca Foundry Inc. Plant 4, Marinette, Wisconsin.|