Measuring and testing – Vibration – By mechanical waves
Reexamination Certificate
2002-05-13
2003-11-25
Williams, Hezron (Department: 2856)
Measuring and testing
Vibration
By mechanical waves
C073S602000
Reexamination Certificate
active
06651503
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention generally relates to a method of ultrasonic flaw detection of long-distance pipelines such as, for example, trunk oil pipelines, oil-products pipelines, and gas pipelines. More specifically, acoustic communication between one or more ultrasonic transducers and the pipe walls (for example, by means of a fluid plug) is provided by passing inside the pipeline a so-called “pig,” or an inspection probe, which is put into the pipeline and is conveyed by the fluid flow in the pipeline. Typical inspection pigs have built-in transducers, measuring instruments, devices for conversion and recording of the measured data, and a device that acquires digital data during the pig travel and processes the obtained data to detect flaws in the pipe walls and to determine the parameters of the detected flaws, as well as their position in the pipeline.
Known in the art is a method of in-tube ultrasonic flaw detection (U.S. Pat. No. 4,162,635) carried into effect by passing inside a pipeline a inspection pig having ultrasonic transducers, means for measurement, processing and storage of the measurement data. The traveling pig emits ultrasonic probing pulses towards the walls and receives the respective reflected ultrasonic pulses.
Also known in the art is a method of in-tube ultrasonic flaw detection (U.S. Pat. Nos. 5,587,534, 4,964,059, 5,497,661, 5,062,300) using a thickness metering technique. In accordance with this technique, an inspection pig that accommodates ultrasonic transducers and means for measurement, processing and storage of the measured data is passed inside the pipeline. During the pig travel the pulse transit time is measured by emitting ultrasonic probing pulses and by receiving the ultrasonic pulses reflected from the internal and external walls of the pipeline.
In accordance with these known techniques, making measurements with accuracy sufficient for inspection, identification of flaws, and determination of their parameters requires use of high-capacity memory devices. However, the pig traveling inside a pipeline has a limited volume for arrangement of data storage devices.
Several data transfers accompany the use of standard devices for compressing the data stored in files, irrespective of the physical nature of these data. At a low amount of transfers the compression is ineffective. The use of archiving algorithms such as Zip, Arj, Rar, and other efficient compression routines is accompanied by plenty of transfers of the compressed data. In so doing the amount of transfers and, respectively, the archiving time depends on the type and character of the data and is not restricted from above. For this reason, the time of data processing can exceed the reserved time and lead to errors in subsequent processing of the data and, respectively, to loss of some data.
Also known in the art is a method of in-tube ultrasonic flaw detection (U.S. Pat. No. 5,460,046 using the thickness metering method. In accordance with this technique, a pig (flaw detector) is passed inside the pipeline, said pig carrying ultrasonic transducers and devices for measuring, processing and storing the measured data. The measured data are generated by emitting ultrasonic probing pulses during the pig travel, receiving the respective ultrasonic pulses reflected from the internal and external walls of the pipeline, and by measuring the pulse transit time.
This method is characterized in that the values corresponding to the pipeline wall thickness within permissible limits are neglected, and what is recorded are only the values corresponding to the wall thickness below a permissible value.
During the in-tube ultrasonic flaw detection of pipelines, which have pipes whose thickness is beyond the permissible limits for the pipeline being tested, the measured data of the part of the pipeline corresponding to such pipes are recorded in a full scope even if they have no flaws.
Known in the art is another method of in-tube ultrasonic flaw detection (U.S. Pat. No. 4,909,091) by passing an inspection pig inside a pipeline, said pig carrying ultrasonic transducers, devices for measuring, processing and storing the measured data by emitting ultrasonic probing pulses during the pig travel and receiving the respective ultrasonic pulses reflected from the internal and external walls of the pipeline, and measuring the pulse transit time.
This method is characterized in that the measured successive values, which are rejected within a predetermined range of values, are recorded as a function of a number of successive values.
When testing the pipelines having pipes of different types and with a different thickness of the wall (with a difference in the wall thickness exceeding the error of thickness measurement and, respectively, the preset range width) the data measured in the part of the pipeline corresponding to the rated wall thickness for the pipes of a given section are not within the predetermined range and are not compressed.
The most similar with claimed method is a known in the art (U.S. Pat. No. 5,635,645) method of in-tube ultrasonic flaw detection of pipelines by passing inside the pipeline an inspection pig (flaw detector) carrying ultrasonic transducers, means for measurements, processing and storing the measured data, by emitting ultrasonic probing pulses and receiving the reflected pulses corresponding to said probing pulses, by obtaining data on the time intervals corresponding to the transit time of said pulses, and by conversion and storage of the measured data in the process of passing inside the pipeline.
During the data conversion in this method a sequence of the obtained values of the pulse transit time is formed, the number of obtained values of said sequence within a certain range being calculated and recorded in a storage device.
This method is characterized in that the range of values is set by a nominal value and a window symmetric relative to the nominal value. The nominal value is determined for each sequence of the obtained values by averaging the sequence values.
The main disadvantage of the known method is that in the presence of elongated lamination of metal in the wall of the pipe being tested or other flaws, the average value, as a rule, is beyond the range corresponding to rated pipeline wall thickness and beyond the range corresponding to the metal lamination. As a result, neither the values corresponding to the rated wall thickness nor the values corresponding to the laminations are in the range near the average value and, therefore, are not compressed.
The claimed invention is a method of in-tube ultrasonic flaw detection of pipelines is effected by passing inside a pipeline an inspection pig carrying ultrasonic transducers, devices of measuring, processing and recording the measured data (devices for measurements, processing and measured data storage), by emitting ultrasonic probing pulses during the pig travel and receiving the reflected pulses corresponding to said probing pulses, by obtaining data on the time intervals corresponding to the transit time of said pulses, by converting and recording (conversion and storage of) the measured data; during said data conversion a sequence of the obtained values of the transit time of the ultrasonic pulses is formed, the number of obtained values of said sequence within a certain (definite) range being calculated and recorded in a storage device.
The present invention differs from the prior art in a number of material respects. For example, in the process of data conversion, an area of values of a certain width is found, which has the maximum number of obtained values of said sequence, said range of values is found, in which at least one value relates to the found area of values. The number of obtained values of said sequence within said range is recorded in the storage device together with a code uniquely corresponding to said area of values and/or said range of values.
One of advantages that is obtained as a result of effecting the claimed invention is, for example, a decrease of size of the stor
Bazarov Alexandr Jurievich
Desyatchikov Alexandr Petrovich
Karasev Nikolai Alekseevich
Kirichenko Sergei Pavlovich
Slepov Andrei Mikhailovich
NGKS International Corp.
Saint-Surin Jacques
Welsh & Katz Ltd.
Williams Hezron
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