Volume 33, Number 11, November 1998

 

Two-Two-Two Lines in One

Twin Tandem Lines Operate Through Thick and Thin

by Chuck Kaplanek

Webster’s New World Dictionary Definitions

"FLAT" (flat) . . . 1. Having a smooth and level surface; having little or no surface depression.

"FLATTER" (fla’ter) (adj) . . . As being more than flat and almost perfectly on one plane as greater than the above "flat."

"FLATTERY" (flat’er’e) . . . Your customer’s verbal response to tempered and heat-strengthened architectural glass that is both flat and smooth as a lake; glass that is both aesthetically pleasing to view and proper in thermal performance and break pattern; flat tempered laminated glass that does not bow or warp and allows for a clean, blemish- and air-free product; a tempered lite of Low-E glass with little or no mottling and/or tempered "low iron" glass that is smooth, clear and almost invisible . . . etc.

Actually, that last definition is mine and not Webster’s. But let me start at the beginning of this story and not at the end. Our company has been a temperer of large architectural glass since the mid-1980s. We jumped right into the business by commissioning a huge (for the ’80s) 96- by 178-inch capacity Tamglass batch tempering furnace.

Back then, heat strengthening was less complicated because the whole process of making tempered glass was new and basic—almost a bit primitive. In those days, tempered glass was mandated by a few government regulations concerning doors and adjacent lites and several other specialty use categories.

It was the era when the operational control and knowledge of the product outcome was severely lacking, and usually resulted in a hit-or-miss situation. It seemed that the art of tempering was a "cloudy and spiritual phenomenon" that was generous to your tempering department if the glass arrived at the quench in one piece. If it broke during the process, it broke into more than two or three pieces.

Tempered safety glass was a wonderful and profitable growth product to market. Glass size requirements were expanding and demand exceeded supply. Having glass that would pass the impact test was more important than its flatness or the lack of surface defects.

Our tempering line processed glass from 1/8- to 3/4-inch thick. Most of the output was for glazing use and included a simple swiped edge. These "core" tempering products were produced en mass for years on a two- or three-shift basis. There was little discussion or concern about warpage, bow or surface compression or distortion, stress marks, mottling, parallax view or lami nesting, etc. But the wheels of change were turning and almost overnight, the way things were . . . were no longer.

"The Heartbreak Dumpster"

In 1996 we decided to broaden our commitment to special architectural products and started to produce laminated products to complement our insulating and tempering production (see USGlass, June 1995 to March 1996). At that time, we planned the laminating line to augment the tempering line. Little did we realize that the tempering quality control would greatly influence the outcome for success or failure of laminated products.

Finally, in 1997 our plant was producing large, heat-strengthened laminates. We were producing them, but not necessarily successfully. We noticed that our failure rate for "air entrapment" within the laminate was much higher than we had anticipated.

It is a sad sight to see a dumpster full of rejected heat-strengthened laminates. The entire cost of the labor, raw glass, edgework, heat treatment and lamination was already in the product when it came out of the autoclave—only to fail and be dumped.

The window of opportunity for successful and air-free lamination is often very narrow. On laminates as large as 19,380 in2 (492,250 mm2), the interlayer can be less than one-mm thick. If the "after clave" warp, bow or air gap within the heat-treated glass is greater than the interlayer (one mm), you must add it to the "heartbreak dumpster."

With all this "after the fact" knowledge in our hands, we decided to scrap any other capital improvement programs in favor of improving our heat-treating programs in a big way. Once in this new frame of mind, we decided to improve far more than just our tempered-laminated production products.

Some of the problems we were running into with our second-generation tempering line (four to nine years old) were:

Investing in the Future of Heat Strengthening

We all agreed that we needed a new program for our heat treating of glass. That’s when I knew it was the time to invest in yet another "capital improvement" program. The executive board approved and my job was to get the checkbook ready.

I decided on twin tandem "double barrel" lines for a good reason. We realized that our demands upon a big oven for both jumbo and thick glass, coupled with the need for thin glass and especially for thin heat-treated laminates, was asking too much from one line. The temperature changeover and air pressure differences between the two categories of products complicated our demands. I felt that with twin tandem lines, each line would produce its own special products and do it right with an elimination of the extremes between batches.

The lines we bought are both manufactured by Tamglass Engineering of Finland, which supplied our previous line. The decision was rather easy since I have a lot of faith in the company’s technology improvements during the last ten years. In addition, Tamglass was willing to make some engineering improvements on these new lines that I recommended based on a decade of our operating experience. I felt that we knew as much about their equipment on an operating basis as they did. They agreed and we put together two lines, each with some pretty sharp features.

With their help, we broke the record for installation time for two tempering lines. All told, it took us about five weeks to remove one and install two.

The big line has a 96- by 200-inch glass size capacity, and handles the entire architectural line of products. With its pyrometer and thermodynamic control, we can really control our glass in the process, making it flat and highly functional for specific needs.

The small line is a 56- by 104-inch capacity line, and excels with thin products. It has more blower boost capacity. We need two blowers for cooling the 1,300 degree F glass with this line and it is a "screamer." Believe it or not, we put the blowers on a steel superstructure and enclosed them on the roof of our building directly above the line. We call it the "penthouse." It’s nice and quiet near this line . . . and at the senior citizen home next door, the residents don’t hear a thing!

Sweet Success

It’s now been about three months of running the tandem lines and I know that the concept was successful. Not only are we producing more glass, but what we produce is of the quality needed to support the high-end specialty laminated products our customers need. I am especially pleased with the results of our heat-strengthened laminates in the very large sizes. This opens a new potential for ever-larger and better laminates with superior qualities in both aesthetics and performance. Further, we are handling the special products with unique interlayers and special coated glass far better than before because we can control our temperatures and air pressures as required.

Tamglass engineers invested significant time and effort to meet our unique needs. A project like this will be successful when such a supplier produces special equipment to a customer like us who knows what it wants.

Chuck Kaplanek is the president of Floral Glass, Hauppauge, NY.


USG

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