TPT January 2020

AR T I C L E

Sikora AG

Digital X-ray measuring technology in the production of hoses and tubes by Dr Hilmar Bolte, research and development head of analysis, Sikora AG, Germany

operation point has been reached. There is no warming up phase or a dependence on the product temperature, no coupling media is needed, nor any requirements regarding their quality. A correction or recalibration of the measuring values during production is also not required – either manually, or by including secondary values such as a gravimetric measurement. This is a significant advantage in comparison to other measuring methods. The stability of the measuring value and, therefore, the repeatability are significantly better compared to other methods and do not degenerate over the lifetime because there are no moveable parts in use. There are no moving sensors, which have to be adapted to the product and, thus, changeover times do not occur. In general, these characteristics suggest the application of X-ray measuring technology for online control of the extrusion of hoses and tubes. Not only the resolution of single layers is possible, but also the presence of electric conductive additives in the materials (for example soot or metallic layers) or of ply do not represent an exclusion criterion. Functional principle The X-ray measuring devices from Sikora work with X-ray transmission, meaning that the X-ray source and the X-ray camera are facing each other from the opposite sides of the product (figure 1).

X-ray is knownas an imaging technology inmedical diagnostics. In general, two-dimensional images are generated that allow the doctor to look into the body of the patient. They are displayed in greyscale, resulting from the different absorptions of the X-rays when travelling through the body of the patient. For X-rays, materials have a different transparency. Due to these differences in transparency, it is possible to see where the material begins and where it ends. Tissue, for example, is more non-transparent for X-rays than the bones embedded therein. The same applies when using X-ray in measuring technology. It allows for a non-destructive look into and through a product. Furthermore, it can be differentiated between miscellaneous materials that vary in their absorption or attenuation of X-rays. The absorption of a material is defined by its composition, its density and hardness of the used X-rays. Advantages of X-ray technology In particular, when comparing X-ray technology to optical methods, it provides several advantages. Due to its low density, gases that arise during the production process, such as smoke or steam, do not interfere with the measurement. The temperature of the object to be measured is also irrelevant for the attenuation and, thus, for the measuring result. For X-ray measuring technology, the measuring result is stable and constant after the start-up of the device and the Often reservations against X-ray in general exist, partially influenced by referring to radioactive radiation. Contrary to this, X-rays can be turned off when not in use. Furthermore, products which are measured by X-ray are not contaminated by radiation, meaning they do not radiate further. Even when in operation, the devices are safe from radiation and working in close vicinity does not bear any risk, even long-term. This ensures a safe and smooth handling of this technology. Since 1993, Sikora AG has been providing digital X-ray measuring technology for non-contact online measurement of diameters and wall thicknesses in cable production. In 2003, the product portfolio was broadened to the hose and tube industry. Meanwhile, more than 2,000 Sikora X-ray measuring devices are in operation worldwide. From time to time, however, the potential of the principle is underestimated.

Figure 1: Design and functional principle of measurement with X-ray technology

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JANUARY 2020