TPT November 2014

Technology News

X-ray technology ensures quality during production of composite pipes

and application. Pipes which conform to a certain specification are especially required for easy processing, for instance for the connection of the pipes by fittings. The quality control, moreover, saves on plastic material and ensures cost reduction at the same time. Common available technologies for quality control for composite pipe extrusion lines are ultrasonics, the diameter differential measuring principle or gravimetrics. These technologies are suitable for classic control of product parameters, but are limited due to their function and dependence on environmental influences. Ultrasound techniques require a coupling medium (water or gel) for recording of measuring values. Furthermore, the speed of sound is dependent on the material and temperature, so a change of the product or production variables could distort the measuring values. In order to measure the wall thickness as precisely as possible, different variables have to be taken into account, such as the water and material temperature, line speed and water quality. The diameter differential measuring principle is based on the comparison of measuring values, which are measured before and after the extruder, and is for that reason only applicable for the outer layer. Although, this approach gives information about the wall thickness, the concentricity cannot be determined with this technique. Thus, it is impossible for the manufacturer to optimise production in regards to quality and material reduction. During quality control by means of gravimetrics, the amount of material that is fed into an extruder is controlled. This technique again only takes the wall thickness into consideration, and not the eccentricity of the pipe. The precise measurement of all product parameters without any dependency on environmental and material influences can be ensured by using X-ray technology. Since the early 1990s Sikora has been offering X-ray technologies for the continuous quality control of stranded

produced in more and more countries. In 2013 for instance, the number of aluminium multi-layer pipes produced in Asia grew to 55 per cent – in comparison to 48 per cent in 2010. In addition to this growth, the end-users’ demand for quality for the manufactured products is also increasing. Manufacturers of multi- layer composite pipes are striving to further increase product quality in order to stay competitive in the market. At the same time, production costs have to decrease. Measuring techniques with X-ray technology make both possible. Multi-layer composite pipes are used, for instance, in building services for drinking water, heating and cooling installations, under the floor and in walls. Common diameters that can be reached are from 14mm, over 16mm up to 63mm. Speciality pipes can have diameters up to 110mm. These are being used for water supply applications. A multi-layer composite pipe is made of up to five layers: a PE inner pipe, an adhesive layer, an aluminium tape (butt welded or lap welded), another adhesive layer and a PE outer pipe. By means of online quality control during production, pipe specifications can be precisely fulfilled. Wall thicknesses can be 2 to 10mm, depending on the manufacturer

2,189 MILLION metres of multi-layer composite pipes were manufactured worldwide by over 150 manufacturers in 2013. Combined, these pipes would circle the earth 53 times, or have a length of almost three times the distance from the earth to the moon and back. Ten years ago, the worldwide production volume was about 690 million metres. According to a study of KWD Global Pipe 2013 (Pipe & Multi Layer Pipe Market – Today and Trends. Dipl Ing Jutta Hix. KWD Global Pipe, 2013), the trend for the coming years is pointing up. At the same time, quality requirements for products are increasing. Before the establishment of multi- layer composite pipes at the beginning of the 1980s, lead pipes were used for installation in the building services sector. Due to the toxicity resulting from the potential chemical compounds from lead, the production of lead pipes was decreasing. Since 1970, these pipes have not been used for drinking water and have been replaced by copper pipes. The use of copper pipes is also declining. The advantages of multi-layer composite pipes are obvious: they are non- corrosive, more flexible and more cost effective. Today, multi-layer composite pipes are being used worldwide and

X-ray technology for quality control in composite pipe production

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N ovember 2014