Method of in-tube ultrasonic flaw detection

The claimed method of in-tube ultrasonic flaw detection of pipelines is effected, in accordance with one embodiment, by placing inside a pipeline an inspection pig or flaw detector having ultrasonic transducers, devices for measurements, processing and storage of the measured data. During the pig travel, the transducers emit probing ultrasonic pulses and receive the reflected pulses corresponding to said probing pulse thus deriving data on the time intervals corresponding to the transit time of said pulses, the measured data being converted and stored. In the process of the data conversion a sequence of values of the transit time of the ultrasonic pulses is formed, an area of values of a certain width is derived, in which the maximum number of the obtained values of said sequence is located, the range of values uniquely corresponding to the found area of values, in which at least one value relates to the derived area of values, the number of obtained values of the sequence laying in said range of values is recorded in said storage device together with a code uniquely corresponding to said area of values and/or said range of values. The obtained values beyond the limits of said range of values are directly recorded in the digital data storage device. The implementation of the claimed method allows one to, for example, increase the efficiency of compression of the ultrasonic data, especially when detecting the flaws in the linear part of trunk pipelines including pipe with different nominal thickness of the walls, and in the presence of flaws such as and similar flaws in the pipeline.