Method of in-tube ultrasonic inspection where threshold value and amplification factor is varied discretely as a function of time

A method of in-tube ultrasonic inspection of pipelines carried out by passing inside the pipeline a scanning pig, emitting ultrasonic probing pulses towards the pipe wall and receiving the reflected ultrasonic pulses. The claimed method is characterized in that the received pulses are amplified using a different amplification factor, which is increased depending on the time elapsed from the moment of emitting the probing pulse. The threshold values of the pulse amplitudes are also varied depending on time. Digital values of the pulse amplitudes and the time elapsed from the moment of emitting the probing pulse and corresponding to each value of the amplitude are obtained. The empirically obtained dependencies of the amplification factor and threshold on time for each ultrasonic sensor are recorded in a RAM memory. During the processing of the received pulses the previously recorded dependencies for each ultrasonic sensor are readout from the RAM and the respective values of the amplification factor and threshold are established simultaneously with a period, during which the pulses are received with the help of this sensor. The method allows one to compensate by means of hardware the effect of ultrasound attenuation in the material on the amplitudes of the reflected pulses and, in this manner, to increase the accuracy of determining the geometrical parameters of the flaws, a probability of their detection and efficiency of estimation of their danger.