US 4,734,766 A · Method and system for locating and inspecting seam weld in metal seam-welded pipe

Abstract

A seam locating system includes a laser beam scanning means for scanning a laser beam through a plurality of circumferentially aligned scanning points. The system includes means for forming a pattern image of reflected laser beam at each scanning points and means for forming a single-frame video image of the pattern image for each scanning point. A video signal processing circuit selects one or more scanning lines suitable for locating irregularities in the angle of reflection of the laser beam, for locating the scanning line in each frame with the maximum width over which the luminosity of the video signal is higher than a given threshold, for deriving a threshold value to be compared with the maximum width of each frame and for deriving the center position of the seam based on the comparison of the maximum width of each frame and the threshold value and the address of each frame, which address is indicative of the circumferential position of the corresponding scanning point. The seam locating system set forth above is not influenced by scale or the like which reflect the laser beam irregularly but with high luminosity by suitably selecting the scanning lines in each frame of video data. The seam locating system may further include means for feedback controlling the laser beam scanning means relative to the derived center position of the welded seam. Furthermore, the seam locating system according to the invention is applicable to seam-welded pipe annealing for automatically positioning the anneal device over the seam or for flaw detection in the welded seam.

Claims32

Dependent claims

A system for locating a seam on an elongated seam-welded pipe, comprising:

first means for scanning a laser beam across the surface of said seam-welded pipe through a plurality of scanning points aligned circumferentially of the pipe;
second means for receiving the laser beam reflected from each of said scanning points on said pipe surface;
third means for recording said received laser beam in the form of a video image, one frame for each scanning point, said video image containing luminosity data for a predetermined number of pixels in each of a predetermined number of scan lines in each frame;
fourth means for locating the width of a bright area in each frame, which bright area is made up of pixels of luminosity exceeding a predetermined value;
fifth means for comparing said width of said bright area in each frame with a threshold value and producing a binary signal of value "1" when said width of said bright area is greater than said threshold value and of value "0" otherwise;
sixth means for deriving a moving average of the values of the binary signals for a given number of successive frames, determining the frames over which said averaged value was maximized and for recording the address numbers of the first and the last frames where said maximum average values were obtained;
and
seventh means for deriving the location of the center of the welded seam by finding the address of the frame intermediate said first and last frames.

5 more elements

A method for locating a seam on an elongated seam-welded pipe, comprising the steps of:

scanning a laser beam across the surface of said seam-welded pipe through a plurality of scanning points aligned circumferentially of the pipe;
receiving the laser beam reflected from each of said scanning points on said pipe surface;
recording said received laser beam in the form of a video image, one frame for each scanning point, said video image containing luminosity data for a predetermined number of pixels in each of a predetermined number of scan lines in each frame;
locating the width of a bright area in each frame, which bright area is made up of pixels of luminosity exceeding a predetermined value;
comparing said width of said bright area in each frame with a threshold value and producing a binary signal of value "1" when said width of said bright area is greater than said threshold value and of value "0" otherwise;
deriving a moving average of the values of the binary signals for a given number of successive frames, determining the frames over which said average value was maximized and recording the address numbers of the first and the last frames where said maximum average values were obtained;
and
deriving the location of the center of said welded seam by finding the address of the frame intermediate said first and last frames.

5 more elements

A system for locating flaws in a seam of an elongated seam-welded pipe, comprising:

a flaw detector for inspecting the pipe in order to detect flaws in the welded seam of said pipe;
and
a servo-system for said flaw detector for centering said flaw detector over the seam position, which servo system comprises:
first means for scanning a laser beam across the surface of said seam-welded pipe through a plurality of scanning points aligned circumferentially of the pipe;
second means for receiving the laser beam reflected from each of said scanning points on said pipe surface;
third means for recording said received laser beam in the form of a video image, one frame for each scanning point, said video image containing luminosity data for a predetermined number of pixels in each of a predetermined number of scan lines in each frame;
fourth means for locating the width of a bright area in each frame, which bright area is made up of pixels of luminosity exceeding a predetermined value;
fifth means for comparing said width of said bright area in each frame with a threshold value and producing a binary signal of value "1" when said width of said bright area is greater than said threshold value and of value "0" otherwise;
sixth means for deriving a moving average of the values of the binary signals for a given number of successive frames, determining the frame over which said averaged value was maximized and for recording the address numbers of the first and the last frames where said maximum average values were obtained;
and
seventh means for deriving the location of the center of the welded seam by finding the address of the frame intermediate said first and last frames.

8 more elements

A method for locating flaws in a seam in an elongated seam-welded pipe, comprising the steps of:

scanning a laser beam across the surface of said seam-welded pipe through a plurality of scanning points aligned circumferentially of the pipe;
receiving the laser beam reflected from each of said scanning points on said pipe surface;
recording said received laser beam in the form of a video image, one frame for each scanning point, said video image containing luminosity data for a predetermined number of pixels in each of a predetermined number of scan lines in each frame;
locating the width of a bright area in each frame, which bright area is made up of pixels of luminosity exceeding a predetermined value;
comparing said width of said bright area in each frame with a threshold value and producing a binary signal of value "1" when said width of said bright area is greater than said threshold value and of value "0" otherwise;
deriving a moving average of the values of the binary signals for a given number of successive frames, determining the frames over which said averaged value was maximized and for recording the address numbers of the first and the last frames where said maximum average values were obtained;
deriving the location of the center of the welded seam by finding the address of the frame intermediate said first and last frames and
positioning a flaw detector based on the derived position of the center of the seam so as to center said flaw detector over said seam.

5 more elements

Dependencies are inferred from the claim text.

Method and system for locating and inspecting seam weld in metal seam-welded pipe

Life of this patent

Method and system for locating and inspecting seam weld in metal seam-welded pipe

Life of this patent

Abstract

Claims32