MEASURING SYSTEMS IN
MEASURING SYSTEMS IN TUBE MILLS MEASURING SYSTEMS IN TUBE MILLS Tube Production and Metrology Measuring Principle and Physical Influencing Factors Production of seamless tubes is dating back to an invention of the Mannesmann Brothersin 1885. In order to ensure economical and future-oriented production of seamless tubes, it is necessary to know the properties of product after every single one of the typically three forming stages. The ever stricter demands being placed on the finished product „tube“ regarding uniformity and compliance with tighter tolerance limits with simultaneous savings in energy and raw materials necessitate a high degree of process reliability, which can only be achieved with precise, operationally reliable and durable measuring equipment. To verify the quality of the product, also to the users of the tubes, all product parameters measured are archived, monitored and analyzed. In this way it is possible to make information available on every single tube produced, both directly during the production process and months after delivery too. General measuring principle Tube wall thickness measuring systems work by the irradiation principle – a radiation source (transmitter) is arranged opposite to an ionization chamber (receiver). A measuring object (tube) located between the transmitter and receiver absorbs a part of the radiation. The residual radiation detected by the ionization chamber generates an electric current, which is processed, digitalized and then sent to a central signal processing system for calculation of the tube wall thickness. Double-wall measurement complete tube circumference and typical rolling shapes of different tube inside contours can be determined. OBJECTIVES Continuous acquisition and storage of all measured values, production parameters and system events Feedback of the measured values to the pilot control and / or tracking of the control devices of the rolling units Targeted error diagnosis to support the operator High availability of the measuring system PROFITABILITY Deliberate utilization of the lower wall thickness limits with simultaneous equalizing of the tube wall profile along the complete length of the tube according to the classifications and special customer requirements Reduction in downtimes after dimensional changes as manual sampling and manual roll adjustment are not necessary Increase in material yield with simultaneous savings in feedstock and energy Measuring principle Mass Measurement Signal processing electronics In the 1, 2 or 4-Channel version the complete mass of the tube in the respective measuring plane is measured – the wall thickness indicated corresponds to the mean of the tube cross section. This measuring geometry is therefore typically used for small tube dimensions, where the tube wall contour was already determined before the finished tube dimensions were reached or is of little interest. Double-wall measurement In the multichannel version (5, 9 or 13-Channel) of the system the tube wall is irradiated respectively at two points, i.e. twice. The beams are arranged uniformly around the center of the measuring system, as a result of which the wall thickness is determined around the Influencing factors The measurement of wall thickness, i.e. the measuring effect at the moment of measurement, depends on the following three main influencing factors: Measuring piece position Measuring piece temperature Measuring piece alloy These influencing factors are taken into account either through separate measurement or using customer data specifications. The measuring piece position is measured with the help of CCD line scan cameras. The position information and tube dimensions are then used to calculate the correcting parameters for wall thickness. The measuring piece temperature is measured with a colorimetric or ratio pyrometer depending on the production temperature. The correcting parameter for the wall thickness can then be calculated based on From top to bottom: Exit Stretch Reducing Mill – 1-Channel system dilatometer curves stored in the system. Internal view sources/detectors – 13-Channel system If grades of steel whose alloys differ from the standard Entry Reheating Furnace - 9-Channel system alloys are rolled, the correction values are also calculated here based on data specifications. 4 5 Receiver (Ionization chamber) Tube Transmittter (Source) Massmeasurement eccentric tube Measuring piece position measurement CCD- line scan camera Backlight
