Measuring and testing – Vibration – By mechanical waves
Reexamination Certificate
2002-08-30
2004-08-10
Williams, Hezron (Department: 2856)
Measuring and testing
Vibration
By mechanical waves
Reexamination Certificate
active
06772637
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATION
Not applicable.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not applicable.
BACKGROUND OF THE INVENTION
Known in the present state of the art is a method for in-tube flaw detection (RU2018817—Aug. 30, 1994; RU2042946—Aug. 27, 1995; RU2108569—Apr. 10, 1998; U.S. Pat. No. 4,162,635—Jul. 31, 1979) by passing inside the pipeline the so-called “pig” or an inspection probe which carries reference transducers responsive to diagnostic parameters of pipelines, means for data measuring and processing, and for storing the measured data, by making periodical reference to said reference transducers which emit probing ultrasonic pulses and receiving respective reflected ultrasonic pulses.
Known in the art is another method for in-tube flaw detection (WO 96/13720—May 9, 1996 (relevant patent documents: U.S. Pat. No. 5,587,534, CA2179902, EP0741866, AU4234596, JP3058352);
EP0304053—Mar. 15, 1995 (relevant patent documents: U.S. Pat. No. 4,964,059, CA1292306, NO304398, JP1050903);
EP0271670—Dec. 13, 1994 (relevant patent documents: U.S. Pat. No. 4,909,091, CA1303722, DE3638936, NO302322, JP63221240);
EP0616692—Sep. 28, 1994 (relevant patent documents: WO93/12420, U.S. Pat. No. 5,635,645, CA2125565, DE4141123, JP2695702);
EP0561867—Oct. 26, 1994 (relevant patent documents: WO92/10746, U.S. Pat. No. 5,497,661, CA2098480, DE4040190)) based on a thickness metering technique. The method consists in passing the inspection pig provided with ultrasonic transducers, and means for measuring, processing, and storing the measured data, by periodically referring to said ultrasonic transducers that emit ultrasonic probing pulses, and by receiving respective reflected ultrasonic pulses, and by measuring the transit time of said pulses.
It is the repetition period of the ultrasonic probing pulse and the travel speed of the inspection pig (flaw detector) inside the pipeline that are responsible for longitudinal resolving power of the flaw detector. With a predetermined scanning period (i.e., the repetition period of probing pulses) the scanning increment depends on the travel speed of the inspection pig, i.e., the higher the pig travel speed the larger the scanning increment, and vice versa. The inspection pig travel speed in an oil pipeline or oil-product pipeline may amount to 2 m/s (an unsteady-state value up to 6 m/s), that in a gas pipeline, up to 10 m/s (provided that acoustic communication is established between the ultrasonic transducers and the pipeline wall using, e.g., a liquid plug). When the inspection pig is being passed through the pipeline, its travel speed changes, and in order that longitudinal resolving power be not in excess of a maximum permissible one, the repetition period of probing pulses is selected proceeding from a maximum travel speed of the inspection pig which is practicable when inspecting a particular pipeline.
As a result of changes in the inspection pig travel speed during its passing through the pipeline, an excessive scanning occurs on the travel portions where the inspection pig travel speed is decreased (with the preset rate of referring to the reference transducers), said excessive scanning resulting in an increased amount of measured data per unit length of pipeline and, accordingly, in unreasonable use of the data storage element.
Furthermore, dynamic scanning is performed, according to the method discussed above, whereby the scanning conditions depend on the inspection pig travel speed, as well as on the nature of changes in the travel speed of the flaw detector.
Known in the present state of the art is one more method for in-tube ultrasonic flaw detection of thin-walled pipes of heat-exchangers (U.S. Pat. No. 5,062,300—Nov. 5, 1991 (relevant patent documents: CA1301299, EP0318387, DE3864497, FR2623626, JP2002923)) by passing inside a pipeline a tube-mounted inspection pig having ultrasonic transducers and measurement means, said method consisting in periodically referring to ultrasonic transducers emitting ultrasonic probing pulses and receiving the respective reflected ultrasonic pulses, and processing the measured data. This method is characterized in that the period of referring to ultrasonic transducers, i.e., starting said transducers) is assumed as a function of the inspection pig travel speed inside the pipeline and set by rotating the probe head.
However, said method suffers from the disadvantage that instantaneous slip of the probe head (or odometer wheel) which is typical in inspection of oil-pipelines, results in skipping some pipeline portions due to zero probing signals when the probe head (or odometer wheel) is at standstill. Additionally, the method discussed above cannot be used for inspecting long-distance pipelines due to the fact that the probing device used for carrying out the method, lacks self-containing feature.
The prototype to the proposed method is a method for in-tube flaw detection (EP0684446—Nov. 29, 1995 (relevant patent documents: U.S. Pat. No. 5,460,046, JP7318336) by passing inside the pipeline the inspection pig which carries reference transducers responsive to the pipeline diagnostic parameters, means for measuring, processing, and storing the measured data, by making periodical reference to said reference transducers, processing and storing the data measured by said transducers.
The cardinal disadvantage inherent in said method resides in that an excessive scanning occurs on the travel portions where the inspection pig travel speed is decreased (with the preset rate of referring to the transducers), said excessive scanning resulting in an increased amount of measured data per unit length of pipeline and, accordingly, in unreasonable use of the data storage element.
The herein-proposed method for in-tube flaw detection is carried into effect by passing inside the pipeline the inspection pig which carries reference transducers responsive to the pipeline diagnostic parameters, means for measuring, processing, and storing the measured data, by making periodical reference to said reference transducers, processing and storing the data measured by said transducers.
The herein-proposed method differs from the prototype in that in the course of passing the inspection pig with a period not less than the period of referring to reference transducers, inspection pig travel speed is determined, and the period of referring to reference transducers is assumed as a function of at least two values of inspection pig travel speed found in the course of passing said inspection pig.
The main technical result attainable by realizing the proposed invention consists in that the fact of referring to reference transducers at a period of time depending on the speed of the inspection pig travel through the pipeline enables one to estimate the data storage capacity depending on the pipeline distance to be inspected, thereby avoiding overflow of data storage devices in the case of a decelerated motion of the inspection pig or its transitory jamming in the pipeline. Moreover, a change in the duration of the period of referring to ultrasonic transducers depending on at least two values of inspection pig travel speed determined in the course of passing said inspection pig allow of obviating an unjustified change in the duration of said period in the case of a short-time change in the inspection pig travel speed.
It is in the course of passing of the inspection pig at the abovementioned period of time (that is, the period of determining the inspection pig travel speed) that an average travel speed of the inspection pig is determined for a certain lapse of time not in excess of the period of determining the aforesaid average travel speed of the inspection pig.
Calculation of an average travel speed of the inspection pig for short lapses of time (on the order of 1 to 10 s) allows of avoiding an adverse effect of transient changes in the line speed on estimation of a required period of referring to the reference transducers.
The duration of the period of referring to the reference transducers is considered to
Bazarov Alexandr J.
Desyatchikov Alexandr P.
Karasev Nikolai A.
Kirichenko Sergei P.
Slepov Andrei M.
Miller Rose M.
NGKS International Corp.
Quarles & Brady LLP
Williams Hezron
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