| 摘要 |
PROBLEM TO BE SOLVED: To provide a thin-film removal assessment method for assessing the degree of removal of thin-films such as scales, etc., using a nondestructive method. SOLUTION: An ultrasonic pulse is caused to enter a pipe from its external surface. A zero, etc., time difference dt0 which is the time difference between rising time ta, when a reflected wave reflected from its internal surface side exceeds a reference value such as zero, etc., for the first time and falling time tc when this reflected wave reaches the reference value next, is found. According to the difference between the time difference dt0 and a reference zero, etc., a time difference (A) which corresponds to a zero, etc., time difference dt0 found, beforehand using a pipe or substance which is an equivalent object equal to this pipe and which does not have any thin film, the degree of removal of thin films is assessed. It does not matter if a first reflected wave is used in a pipe which has a thin film whose thickness is of the extent enabling distinguishing a first reflected wave reflected from the internal surface of the pipe from a second reflected waves reflected from the thin film, when the reference difference (A) is found.
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