Performance of membrane pressure transducers in granular materials of various particle sizes

• Published in: Powder technology Vol. 190; no. 3; pp. 410 - 414
• Main Authors: Rusinek, R., Molenda, M., Horabik, J.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 25.03.2009; Elsevier
• Subjects: Applied sciences; Biological and medical sciences; Chemical engineering; Exact sciences and technology; Food engineering; Food industries; Fundamental and applied biological sciences. Psychology; General aspects; Granular materials; Membrane transducer; Miscellaneous; Pressure measurement; Solid-solid systems; Stress state transducer; Membrane transducer; Pressure measurement; Granular materials; Stress state transducer; Particle size; Storage; Granular material; Food industry; Water content; Calibration; Processing equipment
• ISSN: 0032-5910; 1873-328X
• DOI: 10.1016/j.powtec.2008.08.024

There have been numerous attempts to measure the pressure that granular materials exert on storage and processing equipment, but no completely satisfactory method has yet been developed. The present work examines two membrane transducers immersed in a bedding of granular food materials. Pressure generated by the particles deformed a 27-mm diameter duralumin membrane equipped with a strain gauge. Ten types of granular materials, with equivalent particle diameters ranging from 0.1 (coarse flour) to 7 mm (peas), were tested. The procedures and equipment were set up to calibrate the transducer under air pressure and through a layer of granular materials with several levels of moisture content. Our results showed that to assure a standard error of calibration constants of < 1%, the diameter of the transducer membrane should be ≥ 12 times the particle dimension. Transducer readouts depended on the position of the membrane relative to the flat surface in which the transducer was installed. When the membrane was located 0.45mm above the surface, the measured signal was 8–11% higher, while for a position 0.3 mm below the surface, the signal was 3–8% lower, than when the membrane was fitted directly onto the surface. Experiments performed with seeds demonstrated that their higher moisture content increased the measured signal. The transducer should therefore be calibrated in a bedding of material with a moisture content similar to that in which it will be used. The present work examines two membrane transducers immersed in a bedding of granular food materials. Ten types of granular materials, with equivalent particle diameters ranging from 0.1 to 7 mm, were tested. Our results showed that to assure a standard error of calibration constants of < 1%, the diameter of the transducer membrane should be ≥ 12 times the particle dimension. ▪