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Detection of blockages during production of ceramic filters

Drache Umwelttechnik GmbH

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It is hot. Very hot. It must be tough being a delicate ceramic filter travelling slowly through a roller kiln at 2372°F/1300°C. The roller kiln, operated by Drache Umwelttechnik GmbH, is just one of many elements of stress that these intricate products will be subjected to further down the line. The end-product will be used to filter contaminants from molten aluminium and iron used in casting—a difficult job for such lightweight parts.

The ceramic filters must meet very stringent quality requirements before they can be put to use. Yet, even filter manufacturers are not exempt from blockages—one occurs in the Drache roller kiln on an average of once each year. When a filter strays from its normal path through the kiln, it will cause a blockage, and everything stops working. The filter blockage also stops the heat from escaping the kiln, which is when the more serious problems occur. The resulting temperatures destroy the heat insulation of the kiln, causing a week's worth of production downtime along with the replacement of the kiln’s insulation—both costly consequences.

Keeping an eye on the fire

The problem was reason enough for the medium-sized, family-operated company from Dietz in Rhineland-Palatinate, Germany, to take a closer look at this quality control issue. The solution included the installation of a new camera monitoring system in cooperation with Hesselmann & Köhler Prozessautomation. Based in Limburg an der Lahn, Germany, Hesselmann & Köhler Prozessautomation specializes in planning, manufacturing, and setting up systems in the fields of electrical, automation, and process engineering. Four Cognex In-Sight 8000 cameras systems form the centerpiece of an effective early warning network, which detects the first signs of a kiln blockage.

Normally, the ceramic filters should move straight ahead toward the roller kiln exit. However, if the filters move to the side or toward the top of the kiln, problems start to occur. After a thorough analysis, the four In-Sight 8000 cameras were put into position to monitor the interior of the kiln between the entry and exit points. When the filters move offline, they shield the light produced by the gas burner. This is the first sign of filter misalignment, which may result in a blockage.  In such cases, the Cognex vision systems, equipped with an infrared filter, can detect the drop in brightness levels and automatically trigger an acoustic warning signal via a BUS connection. This alarms the workers, who can see that a blockage is starting to form and quickly rectify the problem before it gets out of control.

Automatic checking

The company has also implemented additional preventive measures to detect blockages at the earliest stage possible. An industrial PC is connected to the cameras displaying the four images of the kiln, as provided by the In-Sight cameras. The operator can now observe what is happening inside the roller kiln at all times. To ensure maximum quality control, an acoustic signal also sounds every 30 minutes, prompting the operator to look at the screen. Once the operator has acknowledged the check, the alarm stops, and the check is logged. This process provides Drache Umwelttechnik with a comprehensive system ensuring maximum reliability. The combination of an independent BUS check and a networked industrial PC provides continuous monitoring of the firing processes inside the roller kiln, thereby preventing the intricate ceramic filters from causing harm to the line.

Proud developers

Thomas Köhler, CEO, and Christian Schmitt, application developer, of Hesselmann & Köhler Prozessautomation developed and implemented a blockage detection system which has provided Drache Umwelttechnik with a decisive improvement in production reliability. By minimizing the costs incurred by production downtime, the system makes a sustainable contribution in strengthening the market position of this ceramic filter specialist. For Christian Schmitt, this is the second Cognex system that he has installed at Drache. Approximately one year ago, he successfully developed a checking system that monitors the process whereby filters are rotated when being sprayed with ceramic mass. He is particularly proud that he has been able to implement a new quality assurance project due to the success of the first system, and thanks to the reliability of the In-Sight 5100, he is already in the starting blocks for the next vision project at Drache Umwelttechnik.

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