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A new kiln car design* has been introduced that can overcome these problems. The car is made from an interlocking brick system designed specifically for kiln cars. It eliminates the need for mortar and is custom-designed to maximize low mass, structural integrity and stability, as well as thermal shock resistance.
While the product has been commercially available in the U.S. for the past four years, it has primarily been used in the whitewares and advanced ceramics industries. However, as energy efficiency and stability gain greater priority for plants looking to improve their bottom line, these kiln cars also hold a great deal of potential for the brick industry.
Why Interlocking Brick?Unlike standard brick-and-mortar kiln cars, the interlocking design in the new system relieves the mechanical and thermal stresses caused by thermal cycling. While the interlock is substantial enough to provide mechanical stability, it is also flexible enough to prevent the heat-related damage often found in mortar-built systems.
Additionally, the number of interlock points on the kiln car allows a great deal of flexibility in the car’s design. While the interlocking brick shapes are manufactured in only five overall sizes (16 x 12 in., 12 x 12 in., 12 x 10 in., 12 x 9 in. and 12 x 6 in.) and three thicknesses (2-1⁄2 in., 3-1⁄2 in. and 4-1⁄2 in.), custom shapes can be modified from these standard products to fit each kiln car for each application. In essence, rather than simply purchasing off-the-shelf refractories and trying to make them work for a given application, a brick manufacturer can order a custom-built kiln car. Once a manufacturer decides to use the interlocking brick kiln cars, it provides the kiln car supplier with information about its products and operating conditions. Based on that information, the supplier then designs a customized interlocking brick kiln car system for that manufacturer.
The interlocking system also makes installation easier. Once the right design has been developed, the supplier provides the manufacturer with a set of prints that show both the overall design and the design of each course. Each shape in each course is numbered with both the course and shape number. For example, a print for the second course might show corner shapes as 2/3 (course 2, shape 3), side shapes as 2/1 and middle shapes as 2/4, etc. Shapes that are the same would have the same number. When the kiln car refractories arrive at the plant, each car is palletized separately, so that one complete kiln car setup is on each pallet, and each shape is stenciled with the number that corresponds to the prints. The kiln car can then quickly and easily be assembled simply by looking at the prints. This saves a great deal of installation time compared to conventional kiln cars. Additionally, little to no experience is required to build the cars, compared to conventional brick-and-mortar cars that often require highly trained employees to lay the refractories.
Because of the kiln cars’ increased stability and high thermal shock resistance, less maintenance is required over the life of the car. Additionally, the kiln cars typically last over two times longer than conventional kiln cars. And because the new design is lower in mass and weight than conventional kiln cars, they can provide significant energy savings, especially when replacing dense, solid mass kiln cars.
Putting the Cars to the TestA sanitaryware manufacturer casting its own refractories for its cars in-house was experiencing a great deal of inconsistencies in car design, as well as major spalling and cracking problems. Additionally, 20 man-hours were required to build each car. The company began using the interlocking brick kiln car system and saw dramatic changes almost instantly. Each car required only two hours (four man-hours) to build, and the lower mass resulted in energy savings. Additionally, the extended lifetimes and increased durability of the cars enabled the company to reduce its number of spare cars from 22 to six, saving space within the plant.
Champion Aerospace Inc., a manufacturer of aviation sparkplugs and other related products, also experienced positive results with the interlocking brick kiln cars. In the late 1990s, the company was building its own cars in-house out of standard high-temperature brick. It was a very difficult, labor-intensive process, usually with less-than-perfect results. A typical kiln car lasted only 10 months to one year, and the company was often short on available kiln cars. The brick-and-mortar cars were also subject to thermal shock problems, as well as kiln wrecks due to instability.
In early 1997, the company decided to test the new interlocking brick kiln cars. Chuck Cannon, supervisor of ceramic body manufacturing, was impressed. “The speed and ease with which we could put these cars together were really the deciding factors,” he said. “The cars offered the opportunity to save on labor, and they’re really a much more stable, symmetrical car when they’re finished—they look perfect every single time.”
By early 1998, the company had replaced all of its old kiln cars with the new interlocking brick cars. Cannon estimated that each car lasts an average of at least two years, and much less maintenance is required compared to the old cars. “When the top courses start to expand over time, they don’t pull on everything else and crack the brick underneath them like mortar-based cars. The brick that want to move do, and the ones underneath stay put. So rather than having to replace all four courses, I might only have to replace the top two,” Cannon said.
Additionally, when such repairs are required, each car requires only two hours to rebuild, rather than the 10 hours required with the previous cars. With the reduction in maintenance and rebuild time, the company estimates that it is saving approximately $1000 per car with the interlocking brick cars.
“Since we began using the new kiln cars, we’ve probably saved a total of about $80,000-100,000 in kiln car costs,” Cannon said.
The company has also saved energy in switching to the lower-mass refractories.
Transferring the Benefits to Brick ManufacturingThe interlocking brick kiln cars have yet to be used in a brick plant. However, the new cars offer a wealth of potential production improvements in virtually any tunnel kiln environment. An increasing number of brick manufacturers are beginning to switch to automatic hacking and dehacking systems and are looking for a stable kiln car that can handle the requirements of these systems. And while energy costs may lower for now, they’ll undoubtedly increase again in the future. The low mass, stable, thermal-shock-resistant design of the interlocking brick kiln cars can help brick plants achieve their goals and improve their profitability.
For More InformationFor more information about the interlocking brick kiln cars, contact Gary Lowder at Vesuvius USA, 16 Northfield Rd., Signal Mountain, TN 37377; (423) 886-7890; fax (423) 886-7071; or e-mail Gary.Lowder@cp.vesuvius.com.
*Drilok™, supplied by Vesuvius USA.