Metrology Method For Oil Tank Capacity Based On 3D Laser Scanning Technique

The vertical metal tank is the main measuring instrument between the international petrochemical products trade settlement. Whether the measurement is accurate or not is directly related to the economic interests of the trading parties and the measurement reputation of the country. However, there are so many problems that widespread in the vertical tank capacity measurement, such as the measurement time is long, the work intensity is large, the examination cost is high, and the measurement results accuracy is low, and so on. In view of the above, the paper introduces the 3D laser scanning technique into the capacity measurement, giving its specific application in the vertical metal tank capacity measurement. Modifying the measuring error caused by the tank body tilt、tank bottom capacity and circle radius, at the same time, these methods are compared. The main research contents are as follow:First of all, study the preprocessing method of the 3D point cloud data, combined with the 3D laser scanning technology principles and characteristics of the scanned data, importing the scanned data to the supported point cloud preprocessing software Cyclone, which can exclude the gross error data, and then using the reverse engineering software Geomagic Studio processes the data exported from Cyclone, which is convenient for a further process.Secondly, study the algorithm of the volume measurement based on the 3D laser scanning technology. Capacity calculation model of the vertical tank based on the point cloud analysis is elaborated, study the process of preprocessing and methods of the vertical tank cross section point cloud data; Three methods are used to fit the tank surface point cloud data and get the radius, including the least square method, iterative method, the equivalent area method. Finally tank bottom capacity measurement method and tilt calculation method based on the point cloud analysis are elaborated.Thirdly, the actual measurements are carried out. Taking a vertical tank as test object, using 3D laser scanner to scan the inner surface of the tank, then calculating the data; At the same time, using the enclosed ruler method to measure the every single circle plate, which verifies the feasibility of the 3D laser scanning method. Calculating the capacity of the tank bottom and tilt through point cloud data, which demonstrates the superiority of the 3D laser scanning measurement.Finally, analysis and evaluate the measurement uncertainty of 3D laser scanning method applied in vertical tank capacity measurement combining with the measuring experiment. Analyze the source of the affecting factors and give the evaluation method of the various uncertainty components, then calculate the relative expanded uncertainty of the measurement result and give the measurement uncertainty report. The research demonstrates that: the application of 3D laser scanning technique in the field of capacity measurement is not only an expansion of itself but also a supplement of the original capacity examination method. It can reduce the cost of measurement while improving the measurement accuracy, having obvious advantages.