Through Thick and Thin, Gauging Controls Perform for You

Published: March 01, 2002, By Claudia Hine, Senior Editor

Whether you're in the market for high-end thickness and gauging controls or you want a value-based system, developments have been made at both ends of the spectrum.

Gamma and beta systems are the bread and butter of the industry, reports Dennis Ehntholt, president of Advanz Measurement and Controls Systems, Dayton, OH. “In high speed processes and for lightweight materials, the beta gauge is the most preferred at this time,” he says. “Gamma is better for slower processes or heavier weight materials, but there are applications where gamma, because it's single-sided, can be easier to install than the beta gauge, which has a sending and receiving unit, so it's on both sides of the web.”

Hector Marchand, VP of marketing at NDC Infrared Engineering, Irwindale, CA, adds, “From the standpoint of trouble-free, predictable performance, the most frequently used sensors in the business are the radiation-based gauges, either beta or gamma. They just work. But now with all the regulations and environmental legislation, manufacturers are working to reduce the source activity level to get the most out of the devices while using them at the lowest energy possible to maximize safety.”

Marchand says an X-ray based sensor has been introduced that offers very high performance, but “as soon as you unplug the power, there is nothing in the device that's radioactive. You can open it completely. Nobody can be exposed to anything. As long as it's unplugged, it doesn't generate an ounce of radiation.”

For converters that need to make direct instead of subtractive measurements, full spectrum infrared (FSIR) gauges offer top of the line performance, says Bob Deitrick, director of sales for North America at Eurotherm Gauging Systems, Billerica, MA. “An infrared sensor gives you the best repeatability for lighter coat weights. There's been a strong swing away from promethium, an isotope used in beta gauges, in the measurement of very thin film or for products with a very thin weight. Top-end converters are going to full spectrum infrared. It doesn't have the cost of ownership that promethium does, and it's good for many, many years. FSIR is capable of multi-component measurement, and the promethium just measures mass.”

“Infrared can be used to make selective measurements,” adds Marchand. “For example, in a coextrusion, if a customer is making a packaging film and it has both EVOH and PE in it, an infrared sensor can tell you how much PE and how much EVOH.”

“Information is king,” says Ehntholt, as the majority of suppliers move toward nonproprietary, PC-based platforms. “It's improved all of our abilities to provide the customer with a lot more graphical and digital information from the standpoint of reporting,” he says. “Today's systems provide so much information about a converter's process. They reduce the need for operators to input data manually; they can provide customized reports for internal use or to supply to customers; and they have the ability to monitor and trend, not only the primary measurement, but an unlimited number of variables in the process.”

Deitrick says, “Make sure that if you don't need all the performance, you're only paying for what you need, and the more performance that's required, then be willing to pay a little bit more.” Payback times have been shortened considerably, he says.

“On a coating or converting line,” adds Marchand, “there are very few lines today that can't justify the cost, because if you make any scrap, you can't recycle the material. Now you've got not only the material you added, but the base substrate that you've lost.

“In the not-too-distant future,” predicts Marchand, “you're going to see where a production supervisor is going to have a palm computer on his belt, and he can pull it out and take a look at the profile of any of the coating lines in his plant. That's the kind of Dick Tracy stuff that's not too far away.”

Restrictions of time and space limit the number of companies, products, and trends that we can discuss in these reports. For additional information, see PFFC's features and departments each month, and consult the June Buyers Guide.