In 1999, 134 years after the Civil War ended, two of the original 13 periodic beehive kilns were still being used to fire Robinson Ransbottom’s pottery. While this may have been a testament to the kilns’ durability, Bill Brake, vice president of manufacturing, knew that running the old kilns was costing the plant a significant amount of money in terms of labor, wasted product and wasted fuel.
“The kilns were totally manual-fired—the kiln burners had to be right there, watching the cones fall over, throughout the entire process,” said Brake. Every hour, 13 valves had to be turned to gradually increase the temperature of the kilns until the maximum temperature was obtained. And it wasn’t an easy job. “When new kiln burners started the job, it would take two or three burners working with an experienced kiln burner to accurately fire the kiln,” he added.
“Additionally, there was no firing uniformity at all—the kilns were so massive that we might get our cone 7 on the outside, but on the inside we’d be lucky to get a cone 4. With the quality demanded by today’s market, this meant that a lot of product was unsellable. And on top of all that, the kilns were gas hogs. They really needed to be replaced.”
“We knew Harrop really well and already had a good working relationship with the company. Every time we had a little problem with our tunnel kilns, they were just a phone call or a two hour drive away,” said Brake. “Plus, Harrop had installed a similar kiln several years ago at a nearby location, so we had one in our backyard. We went and looked at their kiln several times, and we liked what we saw.”
The new kiln would fire at a consistent 2270?F (cone 7) and would be based on a Harrop pulsed air and gas combustion system. The combustion system features Hauck gas nozzle mix, high-velocity burners and is capable of delivering approximately 9000 BTUs of air and gas per hour, with 16 burners firing below and above the load. This design prevents flame impingement from occurring on the ware.
Once the system was tuned to the specified firing curve, the temperature and program controls would be repeatable without further adjustments. Six zones of independent combustion control, each operating with a dedicated temperature controller, would help ensure firing uniformity.
While it would be significantly smaller than the old kilns—holding only 1000 cu ft of product compared to the total 10,000 cu ft capacity in the beehive kilns (5000 cu ft each)—it would have a total firing cycle of between 16 and 24 hours, compared to the eight-day cycle required with the beehive kilns, enabling a much faster turnaround of product. And it would also save a significant amount of fuel based on technological and operating efficiencies.
“This is an old factory and we have a lot of old equipment. This new shuttle kiln was really state-of-the-art for us,” said Brake.
“The old kilns were composed primarily of brick and mortar, and when we started knocking the brick down, the amount of dust that went into the air was terrible,” said Brake. “We were still in production at the time, and the old kilns were right near our tunnel kilns. The dirt created quite a mess the first day.”
The company quickly realized that it needed to saturate the old kilns before completing the demolition. “We ended up putting our night watchman out there to hose the old kiln down for about a week before we went back in to finish breaking it down,” said Brake. “After that, there was nothing to it. We have a little Caterpillar loader, and we used that to haul the thousands and thousands of old brick out the door and into a dump truck that we had out back.”
Once the old kiln had been removed, Harrop began constructing the new kiln. In September 2000, the new shuttle kiln was put into production, and the improvements were noticeable almost immediately. “We started out using the new kiln to fire only our birdbaths and jars, but since then, I think the kiln has fired just about every product we make,” said Brake. “We’re saving about 42% on the amount of fuel we’re using, and our labor has been reduced about 12.5%. We’re also getting increased yields due to the uniformity in firing, but the exact percentage has been difficult to track because we’ve been using the kiln for so many different types of products.”
In addition to increasing fuel and production efficiencies, the kiln has enabled Robinson Ransbottom to improve product quality and thereby increase the amount of product it’s able to sell. “We’ve been really pleased with this kiln,” said Brake. “Depending on the economy, we’d like to be able to buy another Harrop shuttle kiln in the future to enable us to grow even further.”
For more information about Harrop, contact the company at 3470 E. Fifth Ave., Columbus, OH 43219-1797; (614) 231-3621; fax (614) 235-3699; e-mail firstname.lastname@example.org; or visit www.harropusa.com.