TPT November 2014

Technology News

using the X-ray measuring system X-Ray 6000. A 7" TFT monitor, including touchscreen operation, is directly integrated in the X-Ray 6000 gauge head, where all measuring values are displayed graphically and numerically. In combination with the processor system Ecocontrol 6000, 1000 or 600, the automatic control of the line speed or extruder rpm is also possible with this system. The technology of the X-Ray 6000 Pro is based on an imaging method. Two X-ray tubes, aligned at right angles to each other, illuminate the pipe transverse to its axis. A line sensor is positioned opposite each of the X-ray tubes and is equipped with a scintillator that transforms received X-rays into light. This creates an image of the pipe within milliseconds. In this way, accurate values are recorded continuously online during the running production process. The analysis is carried out directly from the X-ray image and provides accurate measuring values. A coupling medium is not required, as it is for ultrasound techniques. In addition, the technology is not dependent on the temperature of the measuring head. The fundamental principle of the X-ray measuring technique is the different attenuation of materials based on the periodic table of the elements. The attenuation (µ) of the X-rays is proportional to the atomic number to the power of 3 (µ~Z3). The ethylene monomer (PE) is made out of two carbon and four hydrogen atoms. This corresponds to a very small attenuation. The metal aluminium has 13 protons in its nucleus and, as a result, has a stronger attenuation than PE. The recording of materials with different attenuations leads to a visible contrast of each layer and provides measurements of the pipe dimensions with greater than micrometre precision. For the production of composite pipes, a three-axis measurement can be an important tool for quality control. The measurement in three planes allows for a six-point wall thickness measurement and, in combination with a high measuring rate, the detection of defects such as blisters between the aluminium and the inside of the pipe, as they could arise from a missing adhesive agent. Blisters reduce the product quality and eventually lead to scrapping of the pipe. Composite pipes are typically produced at 30m/min. At this speed, which is 0.5m/sec, the Triax X-ray device measures the pipe at up to 100Hz every

wire products during production. For quality assurance of composite pipes, manufacturers are using X-ray technology, such as the X-Ray 6000 Pro. Depending on the requirements, the device is installed directly after the extruder (hot measurement) or at the end of the line (final quality control). The four-point online measurement provides values for the wall thickness, eccentricity, inner and outer diameter and ovality immediately. These are calculated and visualised in real time with the Ecocontrol 6000 processor system. The system measures up to three different material layers. For composite pipe these are the outer diameter and wall thickness of the PE inner pipe, the aluminium layer and the PE outer pipe. With the Ecocontrol 6000 these measuring values, as well as the eccentricity, are displayed numerically and graphically as pipe cross sections at eight points, and allow the operator to centre the extrusion tool. The use of the X-ray measuring system is especially effective in combination with automatic line speed or extruder rpm control. By controlling the minimal value, only the required amount of plastic material is used, thus reducing costs. With the use of the X-ray measuring system, typically a reduction of 80µm of a 2mm wall can be achieved. This means 4 per cent of the material can be saved. This represents a cost reduction of about €100,000/per year (extruder output: 600kg/h, operating time: 6,000h/per annual, material costs: €1.5/kg). In extrusion lines in which the measurement of only one material layer is required, manufacturers are

The measuring values of the X-ray system are displayed at the processor system

5mm. The smallest blisters and defects in the pipe are reliably detected. A time- intensive and cost-consuming ball test, where a ball is shot through the pipe in order to detect possible irregularities, is unnecessary. Besides the wall thickness, the outer and inner diameter as well as the eccentricity of up to three wall thicknesses, the system measures the ovality of the pipe. The analysis and controlling of the measuring values is done in the same way as with the X-Ray 6000 Pro. The available X-ray technologies cover product diameters of 0.7mm to 650mm. The X-ray measuring system X-Ray 6000 Pro is used in the production of large composite pipes of 63mm to 110mm. The X-Ray 6000, for the measuring of one material layer, is suitable for composite pipes of 14mm to 63mm. The Triax X-ray is used for products of 6mm to 65mm. With the worldwide increasing production of multi-layer composite pipes, the quality requirements for the products are also increasing. Online quality control of composite pipes by means of X-ray technology is becoming more and more important. With the use of the X-Ray 6000 Pro directly after the extruder, the product parameters of all three material layers are controlled.

The different attenuation of the materials leads to a visible contrast in the X-ray image

Sikora AG – Germany Email: sales@sikora.net Website: www.sikora.net

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N ovember 2014