Plastics Technology

MAY 2012

Plastics Technology - Dedicated to improving Plastics Processing.

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All About MoistureMaster ™ Advertisement Q. My dryer has dew point control. What's different about MoistureMaster™? A. Dew point is basically the measurement of the humidity in the air. It has absolutely nothing to do with the amount of moisture that is actually in the pellet. Historically dryer manufacturers have gener- ated extremely dry air (-40° F dew point) at high temperature and users have been told to circulate this ultra-dry, hot air in a hopper full of pellets for a period of time from 2 to 6 hours depending on the resin. The problem with that approach is that the starting point of the resin is usually not the same. For example, was it stored in a silo? What's the humidity outside? What's the temperature of the resin? So as a result, many people over-compensate because they simply don't know if the pellet is dry until it's too late. The results include wasted energy, over-dried resins and in some cases rejected parts. Q. If I have hot air and good dew point, isn't that good enough? A. Hot dry air is a big part of the drying puzzle, but the problem is you really don't know what moisture is left in the pellet unless you use an offline moisture analyzer–and by that time it's too late. It's just like putting a beef roast in the oven at 375° F for 2 hours and assuming it would be done. In most cases, you'd always check it out with a meat thermometer to check the internal temperature of the beef. But it's impossible to check the pellet temperature this way, so the safe bet has always been to over-cook the resin because under-cooking can immediately cause process issues. Q. How does MoistureMaster™ work? A. MoistureMaster™ sensing technology is based on capacitance. This technology has been used very successfully for nearly 50 years in the grain, pharma and food industries to measure moisture content. MoistureMaster™ uses AC current, but it is quite different from the familiar 60Hz household current. The frequency that MoistureMaster™ uses is upwards of 1,000,000 Hz giving us a significantly higher number of samples. Knowing the dielectric constant of a given resin and/or additive gives us a way to then map those readings against the known capacitance constant of water. From there, using sophisticated built-in PLC controls, we can use the data to calculate the actual moisture content of the pellets as they are flowing through the Moisture- Master™ sensor (which is currently available in a 3" diameter chamber for up to 3000 lb./hr). Q Hasn't this been tried before? A. As mentioned above, measuring moisture this way has been used in the food and pharma industries for years, but in those industries the allowed moisture content level was much higher than those in the plastics industry. The progression of computerized controls, for fast comparative calculations, has made this same concept now possible for the plastics in- dustry. The flows of data and comparative technolo- gies with earlier attempts just didn't have the same computing power…no different from many, many technological advances in our daily lives. In fact, it has taken eight years of beta-testing in Europe and research projects through a major university in Switzerland, with government backing, to bring the MoistureMaster™ sensor to where it is today. Q. So the MoistureMaster™ was developed and tested in Europe? A. Yes, the MoistureMaster™ sensor has been devel- oped and tested in Switzerland by BryAir Prokon as the BryScan 100 unit–and has been independently verified by a major university in Switzerland, with government research backing. Novatec now integrates this sensing technology into a separate PLC touch screen controller developed with Siemens which provides a full range of Ethernet, wireless and other outputs so you can get your process back in control. BryAir Prokon has a test lab in Switzerland as does Novatec in Baltimore, Maryland (minutes from BWI Airport).

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