RESEARCH ON TEST AND EVALUATION OF HIGH DEPTH-TO-WIDTH RATIO LONGITUDINAL DEFECTS OF BOILER TUBE INNER WALL

摘要

To solve crack problems at the tube elbow induced by high depth-to-width ratio longitudinal defects on the inner wall of boiler tube, a number of testing experiments and testing methods have been applied to analysis on the sensitivity and correspondence of such defects, and it has been found that the flattening test has an outstanding advantage to detect such defects. However, according to relevant standards, the judgment is controversy. It can be noted from the research that if a steel tube with a ratio of wall thickness to outer diameter larger than 0.1 is turned prior to the flattening test, to reduce such ratio to be less than or equal to 0.1, the shortcomings in detection and evaluation of such defects specified in the current relevant standards of many countries can be effectively overcome. The method has been proposed and adopted preliminarily in the relevant Chinese standard.