November/December 1998
Take a peek at how Griffin Pipe Products Co. transforms shredded scrap into ductile iron pipe and pipe fittings at its Lynchburg, Va., foundry.
By Eileen Zagone
Eileen Zagone is an associate editor for Scrap.
Imagine the substructure of your neighborhood: Under your house, your groomed lawn, and your street is an intricate network of pipes and cables that convey all manner of modern conveniences to your home—from cable television to gas for your stove to the clean, potable water that flows from your tap.
Most of us seldom think about those subterranean conduits quietly carrying clean water to our homes and businesses. But lucky for all of us, the folks at Griffin Pipe Products Co. (Lynchburg, Va.) think about little other than potable water pipe because making such pipe is the specialty of its three ductile iron foundries in Lynchburg, Florence, N.J., and Council Bluffs, Iowa. Griffin’s pipe is also used for waste water and sewer applications in your neighborhood.
Of course, making pipe suitable for conveying potable water is no easy feat. It takes quality raw material—that is, scrap—as well as high-tech metallurgical and foundry casting procedures. This journey through Griffin’s Lynchburg facility shows just what goes into making the pipes you never see but can’t live without.
Turning Cars Into Pipes
Would you believe that Griffin makes its pipes out of cars? Shredded cars, that is.
And shredded scrap isn’t just a portion of Griffin’s raw material mix, as it is at most steel minimills. The foundry is 100-percent scrap-fed and the lion’s share of its material is frag. Why? Because shredded scrap has the best metallurgical chemistry for making its final product, says Chip Moody, plant purchasing agent.
So, saying that the foundry is scrap-intensive is an understatement. In terms of total raw material tonnage purchased and dollars spent, scrap is “hands-down my largest single purchase,” Moody says. The foundry uses no pig iron or scrap complements in its mix, though it does purchase some foundry-grade scrap iron—mostly sheared—to augment its shredded feedstock. Most of the scrap the foundry consumes comes directly from scrap processors within a 300-mile radius of the plant, primarily shipped by rail to accommodate the large tonnages it buys—about 14,000 to 15,000 tons of scrap a month at the Lynchburg plant alone, Moody notes.
Once railcars full of scrap arrive at the plant, they’re unloaded and the material is fed by an overhead crane into a bucket that dumps scrap directly into the foundry’s top-fed cupola. To make the right metal mixture, the scrap is layered with foundry coke and limestone and melted to approximately 2,500oF or higher.
Molten iron flows out the bottom of the cupola into a holding ladle. In this container, the bubbly potion is checked and adjusted for proper chemistry and then poured into smaller ladles to ease pouring in the casting process.
These ladles then head for one of the foundry’s two separate casting areas. The first—for casting pipe—is adjacent to the melting area and consists of three casting machines. The second casting area, located in an adjacent building, is where pipe fittings such as flanges, elbows, and T- and Y-shaped forms are cast.
Whether the molten metal heads for the pipe or fittings area, it isn’t ready for pouring at this point. It’s only molten iron, not ductile iron. To become ductile, it has to go through a metallurgical metamorphosis in which pure magnesium is added to the mix. To make the critical magnesium addition, each ladle is moved off to the side of the melting area where a bar of magnesium hangs suspended, waiting to become one with the iron. This bar is lowered into the molten metal, and the subsequent reaction between the magnesium and the iron is nothing less than sensational. The elements combine in a flare of white light as bright as lightning and a shower of sparks that rivals the best fireworks. To contain this dramatic reaction, a metal hood is lowered over the ladle. And in about 15 seconds—almost as quickly as it began—the reaction is completed and the fireworks die down.
After this magnesium-addition process, the molten iron officially becomes ductile iron. Ductility affords a number of advantages to the finished pipe, Moody says. First, from a metallurgical standpoint, the magnesium causes the iron’s graphite to precipitate as microscopic spheres rather than the flaky structure of gray iron. Ductile iron’s nodular graphite shape, in turn, does not interrupt the continuity of the iron matrix, resulting in an iron that has mechanical properties similar to mild steel, including high tensile strength and toughness, while still possessing the corrosion-resistant properties of cast iron, Moody explains.
Second, because the metal is ductile, the finished pipe can withstand high internal pressures inherent in conveying water, while gray iron water pipe has to be thicker than ductile to withstand similar pressure. Ductile iron pipe also reportedly offers better resistance to impact and shock than gray iron pipe.
Perhaps most significant, because of its strength, much less ductile iron is needed to make a pipe than would be needed to make one of similar strength out of gray iron. As Moody puts it, “With ductile iron, you have more strength, thinner walls, and more flexibility without the brittleness of gray iron. It’s basically less metal doing a better job.”
Red Hot and Rolling
But back to the pipe-making process.
After the metal becomes ductile, an overhead crane moves the transfer ladle to replenish each of the three machine ladles that feed the pipe-making equipment. As the transfer ladle approaches, the lid of each machine’s ladle opens to receive a fresh supply of molten metal.
These ladles then release a thin stream of ductile iron into a narrow trough to be centrifugally cast into pipe. In this process, the metal is spun around a water-cooled rotating mold in the desired pipe shape. Using this method, it only takes between 30 seconds and one minute to make each pipe, depending on its size. The red-hot pipe—now about 1,200oF—emerges from the casting equipment and rolls to the side, where it may be rotated to prevent sagging.
The Lynchburg plant produces pipe that’s 18 feet long in diameters ranging from 3 to 16 inches. Each of the centrifugal casting machines can produce pipe of different diameters. Griffin’s employees simply change the mold to create the desired pipe size. In general, it’s more challenging to make small-diameter pipe, Moody notes. But thanks to its equipment and employee expertise, the Lynchburg plant is able to efficiently produce small-diameter pipe of high quality.
In just a few minutes, each of the centrifugal casting machines has produced several freshly cast pipes that rest in varying shades of glowing orange to the side and back of the casting equipment. From here, an overhead crane picks up the pipes and moves them to the continuous annealing furnace, in which the pipes are heat- treated at up to 1,750ºF then cooled to 1,350ºF. The annealing process enhances the pipe’s ductility and makes it less brittle, ensuring that the product possesses the proper characteristics to perform in its final application, Moody says.
Once the annealing process is over, the pipe is ready for the finishing line where it undergoes rigorous inspection and has its physical properties tested. Each pipe is also water-pressure-tested to 500 psi—higher pressure than it will have to endure in normal use as potable water pipe, Moody notes.
Then, pipe that’s destined to convey potable water gets a cement lining and a coat of black asphalt base paint inside and out. For the final touch, each pipe is stamped with Griffin’s moniker, and then the shiny black pipes are inspected and stacked outside for a varying curing period.
Cast of Characters: Fittings
Of course, ductile iron pipe isn’t all Griffin produces. It also casts a dizzying array of fittings that enable the pipes to do their job. The Lynchburg plant is the only one of Griffin’s three facilities that produces fittings because it has had the manufacturing capability for a long time.
The making of fittings begins when molten iron is transported in a ladle from the cupola building to the fittings foundry building next door. Once there, the metal is poured into a larger furnace and brought up to the proper temperature for casting. Before casting can begin, the iron must be made ductile through the addition of magnesium to the mix, same as in the pipe-casting process. After the magnesium-induced fireworks subside and the molten iron is ductile, it’s poured by overhead crane into prepared molds.
Making these molds is an involved process. Each fitting has its own metal pattern that’s used to make a precise mold of the fitting. The foundry uses a sand-casting method wherein sand is mixed with binders and then packed around a pattern in a flask, a box-shaped container that holds one casting or more. Once packed into the flask, the sand and binders firm up and replicate the shape of the pattern, which is removed prior to casting. Then ductile iron is poured into the sand mold. As a natural insulator, sand helps the molten metal stay liquid enough to flow into every nook and cranny of the mold. A network of channels—called a gating system—ensure that the metal reaches all parts of the mold.
After metal has been poured into the mold, it’s allowed to cool—at least 45 minutes for small parts and several hours or more for large pieces. When properly cooled, the cast fitting is removed and the sand is reclaimed for reuse. From here, the fittings move to a finishing area where rough edges are smoothed and tests ensure that the fittings meet tight specifications. Then, like the pipes, they are cement-lined, get a coat of shiny black paint, and are moved outside to be stored on pallets until called into action.
On a Quality Quest
The finished pipes and fittings are then ready for their subterranean service in our communities and cities.
Griffin’s customers are contractors, municipalities, and sometimes distributors all over the country and—to a fluctuating degree—the export market. The warm-weather months are the firm’s busiest shipping period because that’s when the construction industry is at its peak. In response, Griffin spreads out its production throughout the year to make sure it has enough pipes and fittings on hand to meet this increased seasonal demand.
A significant percentage of the Lynchburg plant’s products are used in the southeastern United States, thanks to the region’s burgeoning building industry and proximity to the Lynchburg operation. Even so, the scarcity of ductile pipe foundries (see “Griffin’s Path to Pipe” at right) means that Griffin’s products are in demand in a wide geographic swath.
Surviving in the foundry industry in general, and the ductile pipe niche in particular, has required a steadfast devotion to producing quality products. As Moody asserts, “We think we make a better engineered product,” adding that Griffin’s equipment and its employee training are “above average. Quality is number one here.”
Of course, to make pipes and fittings that meet tight industry specifications as well as high customer expectations, Griffin has to start with high-quality raw material. Therefore, its scrap supply and its relationships with scrap processors are nothing less than crucial. “We want to put the best scrap we can into the product,” Moody says, noting that consistent scrap helps make consistent pipes and fittings.
To help ensure the quality of the scrap it buys, Griffin emphasizes close relationships and communication with its scrap suppliers, including visits to processors’ facilities and feedback on scrap shipments. Generally, processors have been very responsive to communication with Griffin, Moody says, noting that the foundry buys scrap in such high volumes that processors are interested in pleasing their consumer. Some even call regularly to ask how their material is running in the firm’s process.
That kind of relationship is good for Griffin and good for its scrap suppliers. It’s also good for you, or anyone who has the company’s ductile pipes and fittings hard at work underground.
So, the next time you turn on a faucet, remember that elaborate system of ductile iron pipes moving potable water under your lawn and neighborhood streets like blood through the vascular system—and thank the people at Griffin. •