Catfish feed manufacturer nets production boost with wear-resistant extruder cladding

At the Macon, MS, production facility of Land O’ Lakes Purina Feed, LLC, their primary product is catfish feed. “We are a full-service manufacturing facility and produce catfish feed along with general purpose feeds, such as cattle, hog, and dairy feed, but our primary business is catfish feed,” explains Mark Robertson, Maintenance Manager. “The biggest area for catfish farming is the southeastern portion of Arkansas, west and east central Mississippi, and west central Alabama.”

“These markets are very localized,” Robertson points out. “Usually catfish farms won’t be more than 50 to 75 miles from a feed mill because it gets expensive to transport the feed. We also bag a lot of catfish feed that goes into feed stores throughout the South and Southeast for the guy with a small pond that wants to raise some catfish, but for commercial farms, it’s typically bulk shipped in a ten-bin feed trailer.”

“We primarily manufacture two types of catfish feed,” Robertson explains. “One is 28-percent protein, the other 32-percent protein. We also make a fingerling feed. The fingerling feed is sold to producers that raise young catfish until they get to be typically six to eight inches long before they ship them to the ponds. Often, when they first put these fingerlings into a pond, they continue to use the fingerling feed until the fish get a little size on them. All three types of feed are extruded.”

Most of the protein in catfish feed manufactured by Land O’Lakes Purina Feed comes from soybean meal. Other major ingredients used in the feed are wheat midds and corn. Robertson says, “Catfish feed is very abrasive to our processing equipment, especially the extruders and conveying equipment.”

When the water gets warm, the fish get growing

The market for catfish feed is seasonal and runs from about April to October. It all depends on when the weather gets warm and when it stops raining. “Rain and cold weather slow down catfish feeding,” Robertson says. “If we start out in April without a lot of rain, and it warms up fast, we can get real busy in a hurry. Other years we’re into June before we get busy. But once that water gets warm, the fish start feeding and the race is on. We can run as much as 12 or 13 thousand tons of feed in a month.”

The Land O’Lakes Purina Feed mill at Macon, MS has two (Extru-Tech E 925/Wenger X235), extruder lines in the catfish feed production operation. “We’ve been progressively trying to increase production,” Robertson reports. “We started by increasing extruder speed. Originally, the extruders had 300-rpm output that were increased to 400-rpm. We’ve continually tried to do things that would increase throughput.”

Searching for ways to maximize production

“When manufacturing catfish feed, we always know how fast we’re running because we monitor the speed of our feeder screws feeding the extruders,” Robertson explains. “Actually we now have a panel view that tells us how many tons per hour is going through the machines. Over the years, we’ve learned that all of the work that’s done in the extruder is done at the end of the extruder (when the screws and liners are not worn). The final screw is the one that does the majority of the work (pushing)”

“Over a period of time—two, three months, however long it is—that final screw begins to wear and the feed starts slipping back,” Robertson continues. “When this happens, the screws toward the back start having to do the pushing. The further that push moves back in the extruder, the more energy is required to do the same amount of work. So, we have to slow the feed rate down to avoid overloading the motor.”

Wear ultimately affects quality

So, what happens when they have to reduce the feed rate? “As the push moves farther back, we begin to have fluctuation in the amps. When our amps get up high, the extruder is pushing feed out at a higher pressure. When it gets low, the pressure drops. It tends to fluctuate back and forth between high and low. First we’ve got feed expanding more than it’s supposed to. Then we get feed that’s smaller than it is supposed to be, so we end up with inconsistent sized feed that is both floating and sinking with increased fines.”

“Over the course of a typical year,” Robertson says, “We would replace liners and screws annually, before the beginning of catfish feeding season, usually in January. After the extruder has run about 1,600 hours and produced about 20,000 tons of feed, production rates would drop significantly. At that time we replaced just the final screws. Usually we’d get another 1,200 hours of service and produce about 15,000 tons of feed before production began to drop again.”

“At this point,” Robertson explains, “production levels were down about 20 percent. Depending on tonnage requirements at that time (being toward the end of catfish season), we would decide whether to replace any more screws and liners or wait until rebuild.”

Cladding was the solution

“When Lorrie Muzzone from Conforma Clad, a Kennametal Company based in New Albany, IN, started talking to us about the wear resistance of cladded screws, it seemed like a natural thing to try,” Robertson says. “Of course, we were skeptical because everybody says, ‘We’ve got the best and the greatest thing in the world.’ However, even though we had never done business with Conforma Clad before then, it seemed worth taking a chance, and it’s worked out very well.”

“The main thing the cladded screws have done for us,” Robertson explains, “is to keep our production and feed consistent. We don’t have that slip toward the back, because we’re not wearing out the screws and liners over the course of the year. We maintain the same production level throughout the year so we have a consistent high quality feed throughout the entire year.”

“We have saved some money by using the clad screws,” Robertson reports, “but the savings is secondary. We can lose several thousand dollars a day just in lost production costs. In addition, operating costs are basically the same if an extruder is running 250 tons per day or 200 tons per day. So when we start losing production, we’re not only losing feed that we could be selling, but it’s also costing us more per ton to run the feed that we are producing.”

When parts wear and have to be replaced, Land O’Lakes Purina Feed, Macon is buying new screws and liners for the extruders directly from Conforma Clad, who buys new castings and applies the cladding to meet OEM specifications.

Feed prices are locked in

“Typically we book 60 percent of our feed orders early in the year, before catfish season,” Robertson points out. “This means that the customer already has locked in the price of their feed. Our production capability and the possible need to bring in feed from other plants will not affect the customer’s cost, but it does affect our margins.We used to bring in quite a bit of additional feed prior to installing the clad screws and liners. Since we’ve switched to the cladded components, we rarely bring in more than an additional truckload here and there.”

“We used to run about 11 tons per hour before we increased the speed of the extruder,” Robertson says. “Now we’re up to 12.5, maybe 13 tons per hour. Sometimes we even get up around 14 tons per hour. Speeding the extruders up was just the first step. The main benefit in the cladded screws is that during production everything stays the same. Since we’ve gone to the cladded screws and liners, the extruders run the same everyday. The extruders run the same feed day in and day out throughout the catfish season. Most days, once we are up and running, we make very few adjustments to the equipment during the day.”

“The cost of a cladded screw or liner is about twice the cost of an uncladded OEM part,” Robertson admits, “but the increase in service life and higher production rates over a longer period of time more than offset the additional cost--several times over. The payback is really yet to be determined but basically if that final screw is doing what it’s supposed to do and it’s not worn, the screws behind it aren’t wearing. It’s the same thing with the liners.”

“Every time production drops off, we’re losing money,” Robertson stresses. “To me, the main benefit of cladded screws and liners is that we don’t have a loss in production. The machine does the same thing every day. The feed looks the same every day. The quality remains the same and everything is consistent.” “During a typical week, we’ll start up on Monday morning,” Robertson says. “After we’ve loaded three or four trucks, we’ll run non-stop until sometime late Saturday night or Sunday morning when we fill up again. Then, we’ll start it all over again the next week.”

“In years past,” he continues, “we never would be full and we’d start out in the hole. Usually by Wednesday or Thursday we’d have to have trucks come in and bring us feed, sometimes eight or ten trucks a day to meet the demand because we couldn’t manufacture enough. Now, we’ve increased production enough to where we don’t have to bring in extra feed. I think we may have brought in about four loads last year.”

“Overall,” Robertson says, “considering our lower maintenance, reduced downtime, increased production, and better quality feed, I would say that changing to the Conforma Clad screws and liners has resulted in an economic gain somewhere in the range of $75,000 to $100,000 per year--and that would be a conservative figure.”

Steps in the Conforma Clad Process

Step 1 – Powder Mixing

The Conforma Clad process begins by mixing powdered tungsten carbide and other metals with organic binders according to specific cladding formulas.

Step 2 – Cloth Formation

The materials are rolled to a predetermined thickness and density, forming a flexible cloth that maintains a uniform weight and readily conforms to complex geometries.

Step 3 – Cloth Application

The cloth is then cut to shape and applied to metal components with a low temperature adhesive.

Step 4 – Furnace Brazing

The clad component is placed in a furnace and heated above the melting point of the hardfacing alloy. The molten alloy wicks down into the layer of tungsten carbide particles, metallurgically bonding the hard particles to the component and forming the Conforma Clad cladding. When brazing is complete, the components are finished to customer specifications.

Cladding Specifications

Based upon more than 20 years of research, Conforma Clad has developed three standard tungsten carbide cladding formulas: WC200; WC210; and WC219. Each formula provides superior wear protection within a wide range of operating and wear conditions, which may include abrasion, erosion, corrosion, and impact--individually or in combination. Custom formulations also can be developed to fit specific customer requirements.

Standard cladding thickness can range from 0.020 to 0.125 inches. Most cladding is applied by hand. In cases where there is not sufficient hand access, mechanical aids may be employed. Inside diameters as small as 0.250 inches and 6 inches long have been clad with the aid of an application rod. Chamfers and radii as small as 0.125 inches can be clad.