BCR: Temperature Profiling: A Global View

Datapaq's Dave Plester shares his insights on what's next in temperature profiling technology.

Dave Plester
Most experts agree that one of the best ways to measure a plant's performance is by benchmarking with other plants in the industry, both domestic and worldwide. However, this is easier said than done-after all, with the continued high demand for brick and structural clay products, who has time to take a global plant tour?

One valuable resource for this information is industry suppliers. Companies that provide products and machinery to brick plants often have representatives who travel around the world and can provide insights on "best practices" seen in other facilities. While careful not to release any proprietary or sensitive information, these individuals are usually happy to share information on general trends and innovations that can help brick manufacturers become more productive and competitive.

Dave Plester, Datapaq's product manager for high-temperature profiling systems for furnaces and kilns in the brick, ceramic and other heat treatment industries, is one example. Over the course of his career, Plester has traveled throughout the world developing and commissioning temperature profiling systems. He agreed to share some of his insights with the readers of Brick & Clay Record.

How long have you been working in the kiln industry?

It's been over 16 years. After living overseas for 14 years working in the cable-making industry, I decided to return home to the UK where I joined Drayton Kilns. Shortly after that, Datapaq offered me the position of product manager.

You travel throughout the world testing new developments and commissioning profiling systems in the ceramic, brick and related heat treatment industries. Where have you been?

A lot of places! All over Continental Europe, Canada, the U.S., Brazil, Mexico, Argentina, Chile and most of the countries in the Far East.

Is there one operation that stands out in your mind for being particularly innovative?

In Japan I saw a roof tile process where the tunnel kiln ended at, or just after, the firing zone. There was no cooling zone, but a moveable periodic kiln was "joined" to the end of the tunnel kiln. After the kiln car had entered the "periodic" kiln, it moved sideways, and a new periodic kiln took its place to take the next car. Inside each periodic kiln, the batch of roof tiles on the kiln car went through a reduction and cooling cycle that left the tiles with a silver sheen.

As far as I could make out, this setup allowed them to get different finishes on specific batches of roof tile without altering the settings in the tunnel kiln part of the process. This also allowed them to reduce the number of rejects that would have been produced in a normal tunnel kiln setup, as the kiln settings were changed to get the different finishes.

Are the processing problems you run into similar, or are there geographic differences?

The problems I see are remarkably similar and generally involve a heating imbalance around the kiln car, cooling cracks (dunting) or overshooting in the first part of the carbon burnout zone. Some companies are innovative and use features available in their profiling software-for example, studying how the heat work index relates to the results of physical quality control tests made on the brick after firing, and how this can be used to improve the process.

Figure 1. A temperature profile of a kiln in northern England. The peak temperature beneath the kiln car was 700°F, and the process time was more than 60 hours.
What is the most challenging problem you've run into?

There are two that stand out. The first was a kiln in northern England that had a particularly high under-car temperature. The early Datapaq profiling systems used a phase change heat sink and were huge. The first time we carried out a trial in this plant in 1990, we ruined a heat sink and data logger because the temperature under the kiln car peaked at more than 490°F (250°C) over a 75-hour period-too much for those early barriers. This bugged me, and several years later when we developed the new evaporative thermal barriers, I put this kiln near the top of my beta test site list. This time, the under-car temperatures were higher! The process time was over 60 hours and the peak temperature beneath the kiln car hit 700°F (370°C), but the new system was still working at the end, even though the high-temp plastic plugs on the customer's thermocouples had disappeared.

The second most challenging problem was getting a radio frequency (RF) signal out of a roof tile hydro casing kiln. These kilns use water to effectively seal around the kiln cars, and the whole kiln is completely encased in steel. From an RF point of view, it is essentially two "Faraday cages," one inside the other. It's tough enough trying to get a signal out of a metal clad kiln, but RF does not pass through water or a double layer of steel and refractory. We finally cracked the problem by designing a high-temperature transmit antenna that would operate above the car deck.

How does temperature profiling help brick manufacturers? Why should they profile?

It's very simple. A kiln is the heart of any brick or tile company's business. It's a major investment, and without it there is no business. With this in mind, it makes sense to completely understand the kiln and what happens to the product as it travels through the kiln. If you monitor the profile, especially when the product and output of the kiln are good, then you have a benchmark if things drift out of spec. You will know how the set temperatures relate to the actual ware temperature throughout the kiln, and you can make adjustments with confidence because you'll know what effect those adjustments will have.

I understand you recently commissioned a double traveling telemetry system. What advantage does this system offer?

If you make a change to the kiln settings when you are seeing the profile in real time, it's important to remember that some time is required before the true effect of that change can be seen. By this time, the kiln car with the real-time tracker system may have moved on down the kiln. With a double traveling telemetry system, a second kiln car travels four or five cars behind and picks up the new conditions, so you will be able to see these in real time, too. This means that if a batch of bricks known to have firing problems is running, it is possible to adjust settings and monitor the change before the batch has completed its run.

How has the industry changed since you started?

The biggest change has been consolidation. Sixteen or so years ago, there were a lot of independent brick and sanitaryware plants around. Now many have been swallowed up by the big multinationals.

Technology has also changed significantly. When I started selling Kiln Tracker systems at Drayton Kilns, there were no laptop computers. I lugged a desktop computer around in the back of my car and fed it with 51/4-in. floppy discs (truly floppy). Add to this a kiln barrier that weighed 90 lbs, and I got a good workout in the early days. Now I can put together a presentation on a small laptop with video clips, or give a software demo over the Internet.

What do you see in the future, not only for profiling, but also for the industry in general?

For profiling, there's already a move toward using the RF output from a Kiln Tracker system for other uses, perhaps some type of archiving or control, and we are busy writing software that will output the temperature data in a readable file format at every sampling interval. Also, it won't be long before we will be able to see real time tracking at home via the Internet. Sometimes I wonder if we will ever leave work behind.

For the industry, I see increased growth due to the housing demand-which means more brick, roof tile, sanitaryware, etc. Already in the UK there is a housing shortage that has driven prices crazy, and huge increases in the number of dwellings are planned. The U.S. housing market is also expected to remain robust.

What do you find most interesting about your job?

Variety. My job is split between the ceramic industry and the heat treatment industry, and it covers all aspects of the product, from dreaming up new designs to training the salespeople. In 16 years, I have never awakened on Monday morning depressed. And many of the people I've met have become friends as well as customers.

What is the most rewarding aspect?

Getting an idea for a new product, then following it through to a best seller. Like the TB6000 thermal barrier range, which was conceived over pre-Christmas dinner drinks at the Datapaq UK party and launched six months later. The low points generally are lying beneath a hot kiln car in the middle of an Italian or Mexican summer while rust is falling into your eyes, even though you are wearing safety glasses.

What are the biggest advances in temperature profiling you have seen, and how have these affected the industry?

The biggest advances in profiling have been in the software. When we started out with Tracker software for Windows(tm) 1.0, it took so long to "spool" a full report that it was necessary to schedule the print before lunch so that the "plotter" could get through it by the time you got back. Now Insight software lets you zoom in on real-time data and instantly see temperature changes in fine detail, and analysis features like Quartz Inversion Index take into account the cooling stability across the QI point, not just the cooling rate. With new developments in RF transmission, the software will undergo further development that will make it even more user friendly.

How has this affected the industry? People in the brick and tile industry are more technologically aware now, and with their technological base shrinking (due to consolidation), a lot of organizations profile their kilns and e-mail the profiles back to the central technology department where detailed analysis can be made without constant traveling.

For more information about temperature profiling, contact Datapaq, Inc., 187 Ballardvale St., Wilmington, MA 01887; (978) 988-9000; fax (978) 988-0666; email kiln@datapaq.com; or visit www.datapaq.com.

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