Design and Testing of Thermal Protection Packaging
Published: February 26th, 2002
Data documenting the actual conditions the package will encounter is essential to design. "If you have two or three distribution centers in the United States, where are the hottest and the coldest places that you're going to send to in the summer and the winter? Those are the kinds of thing to consider when you do package testing. Are we overengineering the package testing because you're telling us that something's going to be hotter than it is? In that case, you're going to end up with more insulation, more refrigerant, and more expense than is necessary. On the other side, maybe you're not telling us you're going to see enough extremes, so we're undertesting it and it won't withstand the rigors of the heat or the freezing conditions that can occur," Tuscarora's Pringle points out. "Our lab clients understand that an accurate profile of thermal exposure is critical."
| Tuscarora's ISC Group maintains environmental chambers that can simulate summer and winter extremes. |
"If the pharmaceutical industry had everything in the same vial, same cap, and same secondary package chipboard box, it would make life simpler, but since everything is quite different, it's hard to make claims to protect things within ranges unless they're tested," explains Tom Pringle, managing director of the ISC Group of Tuscarora Inc., a subsidiary of SCA (Phoenix, AZ). More and more pharmaceutical companies are therefore working with package testing laboratories certified by the International Safe Transit Association (ISTA) to design custom solutions to their packaging challenges.
Dwight Musgrave, president of Thermal Vision (Grandville, OH) and vice president of engineering for the Product Design Center (Westerville, OH), explains some of the ways that thermal protection packaging is tested. "We basically start from the inside and design outward. So we start from the payload and determine what it is, what its heat capacity is, and of course, what the design criteria are. From that, we can determine the approximate heat flow that we can allow to get to the interior of the box and then size the cooling system—phase change, dry ice, or other. Next is a finite element analysis, in which we consider the entire load—payload, coolant, insulation—and break it up into very small elements. We rate each material as to its material properties, such as conductivity and heat capacity. Then we do a transient thermal analysis. Next we perform a validation of the prediction to validate the approach that we've taken. In some cases we do a reverse heat flow test as well."
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Several companies provide devices and services for obtaining such trip monitoring data, says Dennis Young, ISTA's technical director. ISTA's certified member laboratories provide a wide variety of services, including measuring the hazards of distribution and then simulating them under controlled conditions in the laboratory.
Lawrence Gordon, president of FDC Packaging Inc. (Medfield, MA), says his company's testing laboratory has participated in about 350 designs in the past two years alone. In addition to its ISTA-certified labs, FDC sells the Hobo Data Loggers and Monitor In-Transit Temperature Recorders for gathering detailed field temperature data. Sensitech Inc. (Beverly, MA) offers devices for monitoring temperature, humidity, and other conditions during transport and storage but also offers a Web-based data collection network and data management services for complete analysis of trip conditions.
Even after packaging has been designed and freight handling has been arranged, many manufacturers of medical devices, pharmaceuticals, or biologics choose to include temperature monitoring devices on shipments to document that specified temperature conditions have been maintained. Devices offered by FDC are Introtech's ColdMark and WarmMark indicators and 3M's Freeze Watch and MonitorMark indicators.
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