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HARTER OBERFLÄCHEN- UND UMWELTTECHNIK GmbH


In-line Barrel Drying State-of-the-Art Today


Time was when bulk material had to be transferred, often in a roundabout way, from a barrel to a centrifuge to be spun dry.


Today, with sufficient amounts of dry air routed appropriately, small hardware can be dried in barrels in a gentle way involving no or only minimal interval movement of the items being dried.


Duplex barrel drying with barrels in vertical or horizontal array has long since been realized, too.


The resulting drying quality is high.


Drying system manufacturer HARTER of Stiefenhofen, Germany, has learned that the drying operation constitutes a bottleneck in the overall process of many plating companies. The plating process has to be interrupted and bulk material manually transferred to centrifuges. The drying results are not always satisfactory with the material often left incompletely dry. Also, centrifuge drying deteriorates surfaces and sometimes compromises corrosion protection. There is a simple reason why barrel drying produced unsatisfactory results in the past: It was common practice to just blow hot air onto the barrels. There was no sufficient air flow, no forced air routeing, and environmental conditions were not maintained as required. This is no longer state-of-the-art. Today, many examples show that comfortable in-line bulk material drying is possible.


Two Components to Success


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The German company HARTER manufactured its first barrel dryer almost 15 years ago. HARTER purpose devised a heat pump based condensation drying system which, through physical action, quickly absorbs humidity on the surfaces of items to be dried, thus drying these items. This alone does not suffice to accomplish the extremely difficult task of drying inside the barrel. The second critical factor is appropriate air routeing using the so-called half-shell technique. Dry air must be passed exactly to the place where humidity is to be absorbed, that is through the custom perforation into the barrel and out again. Air, by its very nature, follows the path of least resistance. To force it to follow the appropriate path is one of the two requisites for success. A perfect combination of these two components, only, ensures successful static in-barrel drying.


Static Centrifugal Drying


Barrel drying development started as early as in 1996. A Swiss company manufacturing fasteners of various sizes and geometries had launched a pioneering project. Bolts and screws were galvanized in the existing barrel line and then transferred to so-called centrifugal baskets for drying. The items were centrifuged in eight stations simultaneously at that time. After this operation, the fasteners were completely dry but corrosion protection was inadequate.


116 SURFACE WORLD september 2013 - show issue


Also, some of the fastener surfaces were scratched. The goal was to eliminate rejections and deterioration. Today, there are four stations where fasteners are dried without being moved. Targeted routeing of extremely dry air has replaced centrifugal movement. The drying stations could not be installed in-line due to space restrictions. This is why the operator chose to retain its procedure – unloading from the barrel and loading into the basket – while investing into new baskets and drying stations.


A Solution for Each Individual Barrel


Much has happened ever since – both the technology has been advanced, and the number of barrel dryers installed has risen to well above one hundred. The first barrel dryer proper was installed with Duscher Galvanotechnik of St. Florian am Inn, Austria, in 1999. And there have been duplex barrel applications, for example with plating company IMO Oberflächentechnik of Königsbach, Germany. Their barrel dryers had not worked satisfactorily. Following successful trial tests of small hardware for use in the electronics industry HARTER installed condensation dryers in all IMO fully automatic bulk material processing lines – duplex barrel type with barrels in horizontal array. Today, their material is statically dried within the specified cycle time. The drying trough and the built-in half-shell provision is always customized to comply with the customer’s existing barrel technology. Also, the drying trough has an automatic cover system to prevent air from escaping to the production area and to minimize energy loss.


IMO Oberflächentechnik electronic components


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