Bubble-point test: Testing of filter elements using image processing

J. Lipowsky, M. Bretschneider, F. Neubauer*, U. Palzer, IAB – Institut für Angewandte Bauforschung Weimar gGmbH, Germany

Filtration is an important basic operation in mechanical process engineering that is used in many processing and environmental applications. Large numbers of filter elements are used in all types of modern plants and equipment, including drinking water treatment, dust separation and fuel purification to ensure clean combustion. This is why it is becoming increasingly important to reliably monitor production quality.

The bubble-point test according to ISO 2942:2004 is a tried-and-tested method to assess the quality of mass-produced hydraulic filters. The filter element is tested by immersing it in isopropanol and applying compressed air. The pressure at which the first continuous chain of bubbles emerges from the filter medium is known as the bubble-point pressure (see Fig. 1). Since this breakthrough always occurs at the weakest point of the filter, this test assesses the entire filter fabric, including all seams and welds.

The difficulty associated with this process lies in monitoring filter breakthrough. On the one hand, it is impossible to predict the exact position where the breakthrough will occur; on the other hand, due to the standard prescribing the emergence of a bubble chain, the detection of individual bubbles is not sufficient to identify a breakthrough. To comply with this complex setting, previously implemented test rigs had to rely on the visual detection of bubble breakthrough by a test engineer. This type of monitoring is difficult to reproduce and prohibitively stressful for the operator. A cooperation project between IAB Weimar gGmbH and B&H Sondermaschinen und Vorrichtungsbau (currently Mühlbradt GmbH) aims to resolve the above issues by...

Session: F2 - Filter Media - Quality Control and Pore Size Analysis
Day: 12 October 2016
Time: 16:45 - 18:00 h

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