Measuring and testing – Vibration – By mechanical waves
Patent
1992-09-30
1996-03-12
Williams, Hezron E.
Measuring and testing
Vibration
By mechanical waves
73616, G01N 2904
Patent
active
054976618
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a method for measuring the delay of ultrasound in the pulse reflection method wherein at least one excitation pulse that is as close as possible to the shape of a shock wave is emitted by a testing head and traverses a pretravel path until it reaches an object to be examined which has a front wall and a rear wall, with at least one reflected pulse being generated at its front wall as well as at its rear wall, and wherein the reflected pulses are detected by at least one ultrasound detector and are amplified by analog signal matching.
To determine the remaining wall thickness of pipelines, a delay measuring method using ultrasound operating according to the pulse reflection principle is employed in a corrosion testing scraper.
The ultrasound pulse generated at the testing head by the transmitted pulse passes through the oil, is partially reflected at the interior wall of the pipe and returns to the testing head. The remaining sonic energy penetrates into the pipe wall, is reflected to a major portion at the exterior wall of the pipe and also returns to the testing head. Depending on the attenuation of the sound, there will be multiple reflections within the pipe wall.
The determination of the delay times is effected by means of clocked counters which are started and stopped by the echo pulse sequences when predetermined thresholds are exceeded. The pretravel path results from the time delay between the transmitted pulse and the echo from the front wall; the wall thickness results from the time delay between the front wall echo and the first rear wall echo. The subsequent rear wall echoes remain unconsidered.
If the surfaces are rough, the echo pattern is an image of the surface structure covered by the sensor. Instead of a single echo pulse (as from a smooth surface), the sensor receives a pulse sequence. The echo pattern is broadened. The broadening over time is a function of the speed of sound in the medium; it is thus different at the rear wall than at the front wall of the pipe. Due to these laws, it may happen in connection with rough walls that, as a function of the wall thickness, the echo patterns from the front wall and from the rear wall blend together.
DE 3,638,936.A1 corresponding to U.S. Pat. No. 4,909,091 discloses a method of the above-mentioned type in which a rough surface either provides a false measurement of the time delay or no time delay at all for a determination of the wall thickness.
Additionally, DE 3,822,699 discloses a method in which an unequivocal time delay measurement is possible with the aid of a measurement blocking period and a triggering threshold that changes over time for the rear wall echo. However, this method fails on rough surfaces if the first front wall reflex is lower than the second or if the widening of the pulse sequence over time is longer than the time duration of the changing triggering threshold (for example, if the wall thickness increases in a pipe segment).
It is the object of the invention to improve a method of the above-mentioned type so that delay measurements for a determination of thicknesses and abnormalities can be performed reliably even on rough surfaces and also if reflected pulses are missing or the pulse reflections are falsified.
SUMMARY OF THE INVENTION
The above object is accomplished according to the present invention by a delay time measuring method for ultrasound employing the pulse reflection method, wherein at least one excitation pulse that is as close as possible to the shape of a shock wave is emitted by a testing head and traverses a pretravel path until it reaches an object to be examined which has a front wall and a rear wall, with at least one reflected pulse being generated at each of its front wall and its rear wall, and wherein the reflected pulses or echoes are detected by at least one ultrasound detector and are amplified by means of analog signal matching; with the method being characterized in that
(a) a time window is set for recording the reflected pulses following the excitation pulse, wi
REFERENCES:
patent: 3583211 (1971-06-01), Brech et al.
patent: 4210904 (1980-07-01), Renzel
patent: 4470304 (1984-09-01), Nusbickel
patent: 4513621 (1985-04-01), Renzel
patent: 4517152 (1985-05-01), Pieper
patent: 4665751 (1987-05-01), Huschelrat
patent: 4909091 (1990-03-01), Ellmann et al.
patent: 4953405 (1990-09-01), Hara et al.
Hillger, "Eln Neues Verfahren Zur Spitzenwertmessung Von Ultraschall-Pruflmpulsen", messen prufen automatisieren, Dec. 1987, vol. 12, pp. 718-722.
Ottes, et al., "Korroslon fruhzeitig erkennen", Elektronik, Dec., 1988, vol. 26, pp. 66-70.
Young, R. S. et al, "Digitally Controlled Ultrasonics For Testing Steel onLine", Non-Destructive Testing (Jun. 1976) pp. 131-135.
Herth Armin
Kuhner Thomas
Stripf Helmut
Kernforschungszentrum Karlsruhe GmbH
Oda Christine K.
Pipetronix GmbH
Williams Hezron E.
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