CASE STUDY: A Quality Profile
Five of the kilns are older direct-fire kilns that are approximately 160 ft long. The sixth is a Swindell Dressler Silver Cloud, which, according to Al Case, senior ceramic engineer at Mansfield, was the largest kiln in North American when it was installed in 1995. A wide hearth kiln, the Silver Cloud is about 15 ft wide by 280 ft long. Always committed to producing high-quality products, Mansfield uses a Datapaq Kiln Tracker system as part of its quality control process.
Staying on TrackMansfield purchased its first Kiln Tracker system in 1991. A data logger encased in a thermal barrier, the system is placed beneath the kiln car prior to firing. As the car progresses along the kiln, thermocouples placed throughout the car relay temperature data to the data logger, resulting in a time/temperature profile for each of the thermocouples. Mansfield Plumbing uses this data to help keep track of each kiln's performance. "We run the Datapaq system about four times a year through each kiln," says Case. "Additionally, if we're having problems with a kiln, we run the system through and compare that data to what we've got historically for that kiln."
The data provided by the Kiln Tracker is used in conjunction with other quality control practices, including crown thermocouple readings, check keys and water absorption tests, to provide a clear picture of how each kiln is firing. All of this information is especially useful in troubleshooting situations. "If we start seeing defective product and it looks like a kiln-related issue, we can pull all of these technologies together," Case explains. "With the Kiln Tracker, I can get a plot of what's happening in the kiln. That information can be corroborated by the check keys (or buller rings or pyrometric cones, depending on what technology you prefer to use), as well as the crown thermocouples readings, to see if the kiln profile has changed or not."
Software UpgradeWhile Mansfield was pleased with the Kiln Tracker's capabilities as a QC/QA tool, the system's DOS-based software eventually became outdated. The system was run from one stand-alone computer, and it wasn't able to save the data to Mansfield's server. "We were reaching a point where there were only about four DOS-based computers in the whole company," says Case. "Servicing them was problematic, and if a computer crashed, our IT people were terrified that they would not be able to retrieve the information."
In 2005, Case decided to evaluate Datapaq's Insight Windows(r)-based software. After looking at the trial software and seeing the available tools, he made the decision to upgrade. "Now we have a system that IT can service fairly easily," he says. "They can walk over with a new hard drive, pop it in and away we go. Another advantage is that I don't have to walk out to the dedicated computer in the control room to look at the data. Once the information is downloaded onto the server, I can pull it up in my office and we can review anything we want."
According to Case, the new software is also much more user friendly than the previous system. Wizards are available to help guide users through each major software function, and a help button also appears on most screens. For each thermocouple, the software can provide information such as quartz inversion (QI) slopes and a QI index; a heat work index; maximum, minimum and mean temperatures; and the heating and cooling rates throughout the firing (see Figure 1).
Putting the Pieces TogetherAccording to Case, the Kiln Tracker system helps Mansfield benchmark each kiln's optimal performance. "When things are running really well, it's great to have a record of the conditions inside the kiln," he says. "When a quality issue comes up, we can then go back and compare the firing conditions. If we can confirm that the conditions are the same, at least inside the kiln, we can rule out the kiln as a potential cause of the problem."
Using the system as part of its quality control effort also helps Mansfield avoid making unnecessary changes to the kiln. "When we do have quality issues, a lot of times there are many possible causes," Case says. "Without analyzing the firings, we could make a lot of adjustments to the kiln before realizing that it's not the source of the problem. We really need as many tools as we can get to track down the source of the problem, and the Kiln Tracker system fits well in our troubleshooting puzzle."
For more information about the Kiln Tracker system, contact Datapaq at 187 Ballardvale St., Wilmington, MA 01887; (978) 988-9000; fax (978) 988-0666; e-mail email@example.com ; or visit http://www.datapaq.com .
SIDEBAR: Old School vs. New Technology"Trailing thermocouples." Whisper this phrase in the ear of many a ceramic plant employee, and they may just head for the hills. In this early method of kiln monitoring, a data recorder was placed outside the kiln entrance, and thermocouples were attached near the ware on a kiln car. As the kiln car progressed through the firing, the wires were unwound the entire length of the kiln. Someone often needed to be available to keep the wires from being crushed by the wheels of the kiln cars, and the wires were dragged back through the kiln once the firing was finished. The raw temperature data would then be manually entered into an Excel (or Lotus) spreadsheet. Not only cumbersome and expensive, this method provided very little useful information.
In contrast, today's Kiln Tracker systems feature advanced software functionality along with telemetry, which enables the data to be collected and viewed as the car moves through the kiln. (See "Tracking Profitability," CI BCR January 2005, pp. 126-130 or online at www.ceramicindustry.com, for one brick manufacturer's experiences with the system.)
According to Michael White, president of Datapaq, some companies have purchased two Kiln Tracker telemetry systems and use them in tandem to correct firing problems as they occur. The second system trails the first by as much as 24 hours, and corrections can be made as the data from the lead system is analyzed. The manufacturer can then gauge the effect of the changes by reviewing the data collected from the second system.
"The manufacturer doesn't have to wait until the system is out to collect and analyze the data, then adjust the kiln and run the system again. Depending on the firing cycle, it could take a week or more to see the effect of the firing corrections that way. Using two systems allows companies to see the result in as little as a day," says White.