Measuring and testing – Specimen stress or strain – or testing by stress or strain... – By loading of specimen
Reexamination Certificate
2000-05-22
2001-10-09
Noori, Max (Department: 2855)
Measuring and testing
Specimen stress or strain, or testing by stress or strain...
By loading of specimen
C073S579000, C073S600000
Reexamination Certificate
active
06298732
ABSTRACT:
BACKGROUND OF THE INVENTION
a) Field of the Invention
The present invention relates to a system, apparatus and method for testing elongate objects, such as pipe, and is directed toward the problem of detecting corrosion, defects or other anomalies to the pipe under conditions where access and/or visual inspection of the pipe is either not possible or impractical.
b) Background Art
In petroleum processing and petrochemical plants and other industrial environments, it is common to have numerous pipes extending between various locations in the plant, with these pipes carrying fluid or gas (e.g.petroleum products), often under high heat and pressure. These pipes are commonly made of steel, and can have an inside diameter ranging anywhere from two to sixty inches, or even outside of this range. The exterior of these pipes are often insulated, with the insulating layers being as great as approximately ⅛ to 5 inches in thickness, or outside of this range.
For a number of reason, (safety, environmental considerations, avoiding costly shut-downs, etc.), the integrity of these pipes must be maintained. Defects in the pipe can occur for a number of reasons. One is that moisture can collect between the insulating layer and the pipe, thus causing corrosion (i.e.rust). Visual inspection of the steel pipe that is encapsulated in insulation is not possible unless the layers of insulation are removed, and then replaced. However, this is expensive and time consuming, and as a practical matter it would be economically unfeasible to accomplish the inspections with reasonable frequency.
It is the object of the present invention to provide a means of inspecting pipes under the circumstances given above in a manner that corrosion, other defects and/or anomalies can be detected with a relatively high degree of reliability, and in a manner that the various difficulties of inspection, such as those mentioned above, can be diminished and/or alleviated.
SUMMARY OF THE INVENTION
The method of the present invention enables corrosion on an elecromagnetical permeable elongate member, such has a pipe, to be detected quite effectively. More specifically, this method enables much of the irrelevant information (reflections, electromagnetic noise) to be eliminated from the wave form, and then the wave forms processed in a particular manner to enable clearer identification of variations in the wave form that would indicate corrosion.
In the method of the present invention, a nearside and far side electric or electromagnetic pulses (waves) are transmitted from, respectively, nearside and farside spaced transmitting locations on the elongate member. The pulses (waves) travel toward one another to intersect at intersecting locations on the elongate member.
The farside pulses are received as wave forms at a receiving location after intersection with related nearside pulses. The transmission of the nearside and farside pulses are synchronized so that the intersections of the near side and far side pulses (waves) occur at spaced intersecting locations on the elongate member.
The wave forms of at least two of the far side pulses (waves) which are spaced from one another are combined to form a composite wave form. A variation of variations are ascertained from the composite wave form as a means of detecting corrosion.
In the preferred form, one of the wave forms of the two wave forms that are to be combined is inverted and then added to the other of the waveforms being combined to create a difference waveform, and variations in the difference wave form are ascertained as a means of detecting corrosion.
Also, in the preferred form, the nearside pulses which pass through points of intersection that are adjacent to one another are considered to be sequential nearside pulses, with the order of sequence being the same as the order in which the points of intersection are spaced along the elongate member. The combining of the nearside waveforms is accomplished in a pattern such that first and second adjacent wave forms are combined to make a first composite waveform, the second waveform and an adjacent third waveform are combined to make a second composite waveform, the third waveform is combined with an adjacent fourth waveform to make a third composite waveform, with the pattern repeating itself with subsequent pairs of waveforms from adjacent farside pulses. Adjacent composite wave forms are compared with another as a means of detecting corrosion.
A reference wave form is established by creating composite wave forms resulting from pulses that intersect at non-corroded areas of the elongate member, and identifying composite waveforms that differ from the reference composite waveform by a phase shift and/or dispersion and/or amplitude and and/or wave distortion.
Corrosion that is present between two adjacent points of intersection on the elongate member is detected by comparing a composite wave form resulting from combining the difference waveform overlapping the point of intersection with difference wave forms on opposite sides of the overlapping composite waveform.
Also, corrosion that is present at a point of intersection of two wave forms can be detected by deriving two difference waveforms by combining the waveform at the point of corrosion with adjacent waveforms to form two difference wave forms which are then compared.
Also, two additional difference wave forms that are on opposite sides of, and adjacent to, the two difference waveforms which are analyzed to detect the corrosion are compared with the two difference waveforms which are combined at the point of intersection as a means of detecting corrosion.
Other features of the present invention would become apparent from the following detailed description.
REFERENCES:
patent: 4181882 (1980-01-01), Isaacs et al.
patent: 4393711 (1983-07-01), Lapides
patent: 4970476 (1990-11-01), Kitagawa
patent: 5456113 (1995-10-01), Kwun et al.
patent: 5497661 (1996-03-01), Stripf et al.
patent: 5526691 (1996-06-01), Latimer et al.
patent: 6065348 (2000-05-01), Burnett
Hughes Robert B.
Hughes & Schacht, PLLC
Noori Max
LandOfFree
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