CA1111129A - Finding and tracking the welding seam of pipes to be inspected by ultrasonic test equipment - Google Patents
Finding and tracking the welding seam of pipes to be inspected by ultrasonic test equipmentInfo
- Publication number
- CA1111129A CA1111129A CA286,918A CA286918A CA1111129A CA 1111129 A CA1111129 A CA 1111129A CA 286918 A CA286918 A CA 286918A CA 1111129 A CA1111129 A CA 1111129A
- Authority
- CA
- Canada
- Prior art keywords
- seam
- pipe
- housing
- path
- pickups
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 238000012360 testing method Methods 0.000 title abstract description 25
- 238000003466 welding Methods 0.000 title abstract description 16
- 238000000034 method Methods 0.000 claims description 10
- 238000009659 non-destructive testing Methods 0.000 claims description 6
- 239000011324 bead Substances 0.000 description 5
- 238000001514 detection method Methods 0.000 description 3
- 238000006073 displacement reaction Methods 0.000 description 3
- 230000001939 inductive effect Effects 0.000 description 2
- 230000003287 optical effect Effects 0.000 description 2
- 230000003190 augmentative effect Effects 0.000 description 1
- 238000012937 correction Methods 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 238000007689 inspection Methods 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 238000005096 rolling process Methods 0.000 description 1
- 238000010998 test method Methods 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23Q—DETAILS, COMPONENTS, OR ACCESSORIES FOR MACHINE TOOLS, e.g. ARRANGEMENTS FOR COPYING OR CONTROLLING; MACHINE TOOLS IN GENERAL CHARACTERISED BY THE CONSTRUCTION OF PARTICULAR DETAILS OR COMPONENTS; COMBINATIONS OR ASSOCIATIONS OF METAL-WORKING MACHINES, NOT DIRECTED TO A PARTICULAR RESULT
- B23Q35/00—Control systems or devices for copying directly from a pattern or a master model; Devices for use in copying manually
- B23Q35/04—Control systems or devices for copying directly from a pattern or a master model; Devices for use in copying manually using a feeler or the like travelling along the outline of the pattern, model or drawing; Feelers, patterns, or models therefor
- B23Q35/08—Means for transforming movement of the feeler or the like into feed movement of tool or work
- B23Q35/12—Means for transforming movement of the feeler or the like into feed movement of tool or work involving electrical means
- B23Q35/127—Means for transforming movement of the feeler or the like into feed movement of tool or work involving electrical means using non-mechanical sensing
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
- G01N29/22—Details, e.g. general constructional or apparatus details
- G01N29/225—Supports, positioning or alignment in moving situation
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
- G01N29/22—Details, e.g. general constructional or apparatus details
- G01N29/24—Probes
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
- G01N29/22—Details, e.g. general constructional or apparatus details
- G01N29/26—Arrangements for orientation or scanning by relative movement of the head and the sensor
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2291/00—Indexing codes associated with group G01N29/00
- G01N2291/02—Indexing codes associated with the analysed material
- G01N2291/028—Material parameters
- G01N2291/02854—Length, thickness
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2291/00—Indexing codes associated with group G01N29/00
- G01N2291/04—Wave modes and trajectories
- G01N2291/044—Internal reflections (echoes), e.g. on walls or defects
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2291/00—Indexing codes associated with group G01N29/00
- G01N2291/26—Scanned objects
- G01N2291/267—Welds
- G01N2291/2675—Seam, butt welding
Landscapes
- General Health & Medical Sciences (AREA)
- General Physics & Mathematics (AREA)
- Life Sciences & Earth Sciences (AREA)
- Chemical & Material Sciences (AREA)
- Analytical Chemistry (AREA)
- Biochemistry (AREA)
- Health & Medical Sciences (AREA)
- Immunology (AREA)
- Physics & Mathematics (AREA)
- Pathology (AREA)
- Engineering & Computer Science (AREA)
- Automation & Control Theory (AREA)
- Mechanical Engineering (AREA)
- Investigating Or Analyzing Materials By The Use Of Ultrasonic Waves (AREA)
- Length Measuring Devices By Optical Means (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A welding seam is located by a transducer during rotation of the pipe which rotation is stopped when the seam has been found in a position for multi transducer seam tracking to maintain the orientation thereof as the pipe passes through an ultrasonic test stand. The various transducers are maintained in particular spaced-apart position to the pipe's surface.
A welding seam is located by a transducer during rotation of the pipe which rotation is stopped when the seam has been found in a position for multi transducer seam tracking to maintain the orientation thereof as the pipe passes through an ultrasonic test stand. The various transducers are maintained in particular spaced-apart position to the pipe's surface.
Description
.l.Z9 The present invention relates to automated detection, finding, locating and tracking of the welding seam in pipes which welding seam is to be nondestructively tested by means of ultrasonics.
Generally speaking, it is necessary to properly position a test object in a test stand in order to conduct the desired test. If the test object is a pipe or tube having a welding seam to be subjected to inspection as to flaws, that welding seam must be located at first because the test equ~pment, e.g. an ultrasonic testing apparatus, must be particularly oriented and positioned with respect to that seam, while, on the other hand, the pipe must be expected to have random orientation when arriving at the test stand. In the past, a test stand operator was usually required to find the welding seam, either directly visually, or through optical or television equipment or through proximity switches, and to initiate the proper alignment operation.
Aside from the initial locating of the welding seam, it is also necessary to track it as the pipe passes through the test stand. For a variety of reasons, such as slack in the transport equipment etc., it cannot be expected that the seam retains the initial orientation, even though, the conveyor attempts to pass straight through the stand. The tracking has been conducted by means of mechanical devices such as guide rollers or through optical scanning, or inductively. Mechanical or related scanning is too inaccurate. The inductive methods as suggested are like-wise too inaccurate due to the permissible variations in seam width and the projection of the seam above the tube~s cylindrical surface, particularly in cases of very flat seams. Also, the sheet stock edges at the weld may have a tolerable radial offset which interfers with automated tracking.
; , "
It is an object of the present invention to provide a new method and equ~pment for properly orienting a welding seam for passage through an ultrasonic test stand.
```` ~LllllZ9 In accordance with one aspect of the present invention, there is provided an apparatus for finding and following a weld seam on a pipe in the non-destructive testing of the seam, which apparatus comprises a housing supporting a first path pickup for detecting a said seam and second path pickups for following said seam and an electrical circuit interlocking the pickups whereby the first pickup monitors the location of the seam and the second pickups control the relative orientation of a said seam with respect to the housing as a said pipe is moved axially relative to the housing.
According to another aspect of the invention there is provided a method of finding and following a weld seam on a pipe in the non-destructive testing of the weld seam, which method comprises rotating the pipe relative to a housing to locate the seam with respect thereto by means of a first pickup mounted in the housing; halting rotation of the pipe; moving the ~ pipe axially relative to the housing; and controlling the angular position ; of the pipe with respect to the housing during such axial movement by means of at least two second path pickups also mounted in the housing, the first and second path pickups being operatively interconnected to align the seam with a non-destructive testing device therefor.
It is believed that the invention will be better understood from the following description taken in connection with the accompanying drawings in which:
Figure 1 is a perspective view of equipment for practicing the preferred embodiment of the present invention;
Figure la is a schematic view of a system; and Figure 2 is a schematic block diagram of a system for practicing the invention.
Proceeding now to the detailed description of the drawings, ! ~ Figure 1 shows a rather flat case 1 which is pivotally mounted in a stand la permitting height adjustment for raising or lowering the case 1. The case as mounted and adjusted, as well as the stand la, to have a particular ,; ~ :
~ ~ ~ - 2 -,~ X : .' ,,~ : : , disposition to (a), a pipe 20 advance device (roller track 21 - Figure la) for moving longitudinally seam welded pipes in a part;cular direction which extends, in the perspective drawing from up, right towards the lower left;
(b) an ultrasonic test stand 22 which extends downstream from the case 1 as far as pipe movement is concerned; and (c) a motor driven roller 23 which together with others lifts the pipe off track 21, and rotates the pipe on its axis. These devices (a), (b), and (c) are shown only schematically; they are conventional, and any suitable device meeting the stated conditions or goals or equivalents thereof can be used. The stand la with case 1 may be part of a table upon which is mounted the or part of the ultrasonic test equipment. Also, raising and lowering of the equipment is possible to bring it into contact or other operative engagement with the pipe. The dotted line in Figure la denotes the combination of the seam locating and tracking device as per Figure 1 and of ultrasonic test equipment 22. The equipment including a seam finding and locating device is pivotable about an axis extending parallel to the axis of the pipe.
The casing 1 has a receiving space in which is inserted an insert 9. The upper surface of that insert faces a pipe to be moved and includes a first, centrally disposed transducer 2, e.g. of the inductive proximity type. The transducer 2 is provided primarily for locating the welding seam of the pipe. Ahead of transducer Z are disposed two, preferably similar ; type transducers 5 which are situated alongside and symmetrically to a horizontal center line that runs through transducer 2, and runs parallel to the pipe's axis as it is being moved over the case 1. Thetransducers 5 are the primary detector and input devices for followup and tracking con-trol of a seam once it has been found.
A pair of further transducers 6, still of the same or of a similar ' ' ` ~ ' '' ,. '' ~ ~ 3 ~
~b. :
. : .. : - - . ~
~, , . ~ , . .. . , .. . . : -type are disposed symmetrically to the above-mentioned center line, but at a greater distance therefrom. All these transducers are mounted in the insert 9 in particular relation to each other, and the~-insert has then been placed into case 1. The insert 9 can be replaced if necessary.
Altogether four ball-rolls 10 are journalled in case 1, permitting rolling movement along a pipe as the latter is axially moved in engagement with these rolls, and permitting rotary movement of the pipe. As the pipe engages these balls, its surface has a particular distance from each of the transducers 2, 5 and 6. As indicated by the arrow in Figure 1, the stand la can be raised, particularly for purposes of bringing the balls 10 into engagement with the surface of a pipe. Such a position of engagement establishes a particular distance of the transducers 2, 5 6 from that surface. This position of engagement is attained for locating the welding seam and is maintained throughout the tracking.
Turning now to Figure 2, the figure shows schematically again the five transducers 2, 5 and 6. The seam finding transducer 2 is connected to a preamplifier 3 whose output controls a switching stage 4. In addition, the circuit 3, 4 is connected to a processing stage 8. As a seam is in .
symmetric proximity to transducer 2, the output thereof has a particular extremity. As the extremity is reached, the transducer 2 is aligned with the seam. The switching stage 4 now stops the turning and rotating of the pipe via rollers 23. As symbolically indicated, this switching stage 4 turns the rest of the circuit on after the seam has been found and the rotating device for the pipe has been stopped. Additional switching opera-tions are performed as will be described later.
The transducers 5 connect to two preamplifiers 7 which produce individual outputs. T~ese outputs, however, are subtractively combined in the switching stage 8 to produce a first position signal that is indicative of the position of a seam relative to the two transducers 5. This signal ~l~llZ9 .
will have a particular value, for example, zero for a balanced position, which is, in fact, an off center position for each of the transducers of ~ -the pair. Since, however, the gain of the amplifiers 7 and the transducer characteristics may differ, a central position of the welding seam above the midpoint between the two transducers 5 may produce a nonzero signal.
Due to the differential mode employed here, this resulting signal is independent to a considerable degree from variations in the seam width as well as to variations in the radial projection of the weld bead.
A command signal is derived from a stage 12 which is subtractively combined with the combined outputs of amplifiers 7 so that an error signal is produced. That error signal is zero for the balanced position. Should for any reason the welding seam deviate from the balanced position, then -the output of the two amplifiers 7 changes in opposite directions, and the combined signal deviates from the adjusted reference signal, resulting in a nonzero error signal.
That error signal is used to control an electrical/hydraulic servo system 11, whose basic function is to keep the several transducers of the ultrasonic test equipment in alignment with the welding seam. This can be done, basically, in two ways. Either, the pipe rotating device causes the pipe to turn a little in one or the other direction depending upon the sign of the error signal, or the ultrasonic test equipment is pivoted, in effect, on an axis that coincides with the pipe's axis so that the test equipment, in fact, tracks the seam. Considering the latter case, if the stand la and case 1 is pivoted together with the test equipment, one will operate in a closed loop configuration. The same is true if the pipe is rotated. If the stand la is not turned with the test equipment, the control is an open loop one. It should be noted that pivoting of the common table requires -pivoting about the table axis and lateral displacement of the ~ 5 ~
.~
~.
, "`" ~11~12~1 carriage to arrive at a pivot motion about the pipe's axis. In either case, ball rollers 10, as per Figure 1, fulfill an important function in that they maintain specific distance orientation and positioning of the tracking equipment relative to the pipe's surface. Thestandla should, therefore, be continuously upwardly biased.
It can readily be seen that the range of seam position deviation, which can be ascertained, is limited. When the seam has practically left the range of one transducer 5, and its center has passed over the center of the other transducer, the error signal begins to decline though the error has increased further. Now, one of the transducers 6 takes over as the seam enters its detection range (or, to be more precise, causes the -transducer to more significantly respond to the scan. The transducers 6 are farther from the pipe's surface and are, therefore, less sensitive but respond to a larger angular range of seam positions).
The two transducers 6 are connected to amplifiers 7, each pro-,. . . .
ducing a more significant output ~higher gain) to be individually super-imposed upon the error signal as generated in stage 8. The gain is chosen so that the now declining (positively or negatively) combined signal from ` amplifiers 7 is augmented so that the resulting signal (as combined with the command signal from stage 12) is, in fact, indicative of the fact that the error is now quite large.
As indicated schematically, the various gain parameters should be adjustable as per a stage 13, and an instrument being connected to the error signal line that interconnects stages 8 and 12, indicates the error signal.
~, The output of the error signal amplifier stage in unit 8 should be connected to a turn-off device with threshold response, responding when , .
~ the pipe's seam has wandered off so that its center is about centered above 1,~
. .
1:~
,:
i~ - 6 --~l~llZ9 one or the other of the two detectors 6. Further rotational displacement will no longer yield a correct result, the apparatus should be turned off and further pipe advance should be halted, because some further correction is needed.
The case 1 includes also a pressure line system for pressurized air, and suitably oriented nozzles are directed towards the transducers to ~eep them clean on a continuing basis.
In operation, the system works as follows for practicing the method as per the present invention. A pipe is longitudinally advanced so that its front end just clears transducer 2. Next, the pipe rotating device 23 is raised to lift the pipe off the longitudinal conveyor 21. Thereafter (or in conjunction therewith), the casing 1 is raised so that balls 10 engage the - pipe and transducer 2 with associated circuit is turned on; also, the pipe ~ -rotating device 23 is turned on. When the transducer 2 responds, switching circuit 4 turns the pipe rotating device 23 off, and the pipe is lowered back onto the conveyor, but the casing 1 remains in engagement with the pipe.
The pipe is now longitudinally advanced towards the ultrasonic equipment in the test stand, a~d the seam follower control is turned on. It sh'ould be noted that all these functions are controlled by the switching device 4, whereby pipe lowering, advance turn on, and seam follower control turn on may be sequenced to avoid incorrect responses. Notably, however, the stand la is biased upwardly so that the balls 10 retain the transducers 2, 5, 6 in the particular distance relation to the pipe's surface.
The seam finding and locating step has placed the seam into such an alignment so that transducers 5 scan along the seam edges. The disposi-tion of the transducers 6 is chosen so that the seam remains entirely or substantially entirely outside of their detection area. If, for any reason, -the pipe tends to turn, the two transducers 5 will change outputs in phase : .
opposition resulting in a first error signal tending to operate the adjustment - -. ' llZ9 ment device 11 so that the test equipment tracks the seam. If we operate in closed loop, the error signal will be reduced to ~ero by the corrective action.
Further rotational displacement of the pipe will cause the pipe's seam to recede entirely from one of the transducers 5, while the other one tends to produce an output which,i n terms of the error signal, tends to indicate a smaller error. This, of course, could be incorrect and now one of the transducers 6 comes into play whose output is superimposed upon the error signal as produced by the two transducers 5 so that in total a large error is indicated. At a certain error maximum, the device may be stopped as further tracking is not possible, and some other corrective action has to - be taken. It will be seen that any irregularities in the welding seam region are being ascertained in the stated manner, such as plate edge offset or other irregularities in the joint, having a bearing on the geometry of the J~ welding zone. On the other hand, variations in bead width are not ascer-tained, as they have no bearing on the desired and required geometry of the -test equipment and its orientation to the seam. It was found that the tracking accuracy is about ~1 mm which amply suffices for the purpose of the test system.
~ 20 Variations in bead thickness have also no bearing on the general ;~ orientation of the seam, but may influence the ultrasonic test procedure otherwise. It should be noted that using the output of transducer 2, one ~ obtains a running indication of relative bead thickness (variations larger i ~ than about 1 mm), as the head of the bead will vary in distance from ~;
transducer 2. This may constitute valuable information for the test evalua-tion.
I ~ .
After the rear end of the pipe clears any of the transducers, e~g~. transducer 2, the output thereof being a well pronounced stress signal, can be used as turn-off signal for the tracking control. The circuit 8 :
~ .
coule be implemented digitally in that the value amplified transducer signals are digitized and processed, i.e. added, and subtracted digitally.
:
g _
Generally speaking, it is necessary to properly position a test object in a test stand in order to conduct the desired test. If the test object is a pipe or tube having a welding seam to be subjected to inspection as to flaws, that welding seam must be located at first because the test equ~pment, e.g. an ultrasonic testing apparatus, must be particularly oriented and positioned with respect to that seam, while, on the other hand, the pipe must be expected to have random orientation when arriving at the test stand. In the past, a test stand operator was usually required to find the welding seam, either directly visually, or through optical or television equipment or through proximity switches, and to initiate the proper alignment operation.
Aside from the initial locating of the welding seam, it is also necessary to track it as the pipe passes through the test stand. For a variety of reasons, such as slack in the transport equipment etc., it cannot be expected that the seam retains the initial orientation, even though, the conveyor attempts to pass straight through the stand. The tracking has been conducted by means of mechanical devices such as guide rollers or through optical scanning, or inductively. Mechanical or related scanning is too inaccurate. The inductive methods as suggested are like-wise too inaccurate due to the permissible variations in seam width and the projection of the seam above the tube~s cylindrical surface, particularly in cases of very flat seams. Also, the sheet stock edges at the weld may have a tolerable radial offset which interfers with automated tracking.
; , "
It is an object of the present invention to provide a new method and equ~pment for properly orienting a welding seam for passage through an ultrasonic test stand.
```` ~LllllZ9 In accordance with one aspect of the present invention, there is provided an apparatus for finding and following a weld seam on a pipe in the non-destructive testing of the seam, which apparatus comprises a housing supporting a first path pickup for detecting a said seam and second path pickups for following said seam and an electrical circuit interlocking the pickups whereby the first pickup monitors the location of the seam and the second pickups control the relative orientation of a said seam with respect to the housing as a said pipe is moved axially relative to the housing.
According to another aspect of the invention there is provided a method of finding and following a weld seam on a pipe in the non-destructive testing of the weld seam, which method comprises rotating the pipe relative to a housing to locate the seam with respect thereto by means of a first pickup mounted in the housing; halting rotation of the pipe; moving the ~ pipe axially relative to the housing; and controlling the angular position ; of the pipe with respect to the housing during such axial movement by means of at least two second path pickups also mounted in the housing, the first and second path pickups being operatively interconnected to align the seam with a non-destructive testing device therefor.
It is believed that the invention will be better understood from the following description taken in connection with the accompanying drawings in which:
Figure 1 is a perspective view of equipment for practicing the preferred embodiment of the present invention;
Figure la is a schematic view of a system; and Figure 2 is a schematic block diagram of a system for practicing the invention.
Proceeding now to the detailed description of the drawings, ! ~ Figure 1 shows a rather flat case 1 which is pivotally mounted in a stand la permitting height adjustment for raising or lowering the case 1. The case as mounted and adjusted, as well as the stand la, to have a particular ,; ~ :
~ ~ ~ - 2 -,~ X : .' ,,~ : : , disposition to (a), a pipe 20 advance device (roller track 21 - Figure la) for moving longitudinally seam welded pipes in a part;cular direction which extends, in the perspective drawing from up, right towards the lower left;
(b) an ultrasonic test stand 22 which extends downstream from the case 1 as far as pipe movement is concerned; and (c) a motor driven roller 23 which together with others lifts the pipe off track 21, and rotates the pipe on its axis. These devices (a), (b), and (c) are shown only schematically; they are conventional, and any suitable device meeting the stated conditions or goals or equivalents thereof can be used. The stand la with case 1 may be part of a table upon which is mounted the or part of the ultrasonic test equipment. Also, raising and lowering of the equipment is possible to bring it into contact or other operative engagement with the pipe. The dotted line in Figure la denotes the combination of the seam locating and tracking device as per Figure 1 and of ultrasonic test equipment 22. The equipment including a seam finding and locating device is pivotable about an axis extending parallel to the axis of the pipe.
The casing 1 has a receiving space in which is inserted an insert 9. The upper surface of that insert faces a pipe to be moved and includes a first, centrally disposed transducer 2, e.g. of the inductive proximity type. The transducer 2 is provided primarily for locating the welding seam of the pipe. Ahead of transducer Z are disposed two, preferably similar ; type transducers 5 which are situated alongside and symmetrically to a horizontal center line that runs through transducer 2, and runs parallel to the pipe's axis as it is being moved over the case 1. Thetransducers 5 are the primary detector and input devices for followup and tracking con-trol of a seam once it has been found.
A pair of further transducers 6, still of the same or of a similar ' ' ` ~ ' '' ,. '' ~ ~ 3 ~
~b. :
. : .. : - - . ~
~, , . ~ , . .. . , .. . . : -type are disposed symmetrically to the above-mentioned center line, but at a greater distance therefrom. All these transducers are mounted in the insert 9 in particular relation to each other, and the~-insert has then been placed into case 1. The insert 9 can be replaced if necessary.
Altogether four ball-rolls 10 are journalled in case 1, permitting rolling movement along a pipe as the latter is axially moved in engagement with these rolls, and permitting rotary movement of the pipe. As the pipe engages these balls, its surface has a particular distance from each of the transducers 2, 5 and 6. As indicated by the arrow in Figure 1, the stand la can be raised, particularly for purposes of bringing the balls 10 into engagement with the surface of a pipe. Such a position of engagement establishes a particular distance of the transducers 2, 5 6 from that surface. This position of engagement is attained for locating the welding seam and is maintained throughout the tracking.
Turning now to Figure 2, the figure shows schematically again the five transducers 2, 5 and 6. The seam finding transducer 2 is connected to a preamplifier 3 whose output controls a switching stage 4. In addition, the circuit 3, 4 is connected to a processing stage 8. As a seam is in .
symmetric proximity to transducer 2, the output thereof has a particular extremity. As the extremity is reached, the transducer 2 is aligned with the seam. The switching stage 4 now stops the turning and rotating of the pipe via rollers 23. As symbolically indicated, this switching stage 4 turns the rest of the circuit on after the seam has been found and the rotating device for the pipe has been stopped. Additional switching opera-tions are performed as will be described later.
The transducers 5 connect to two preamplifiers 7 which produce individual outputs. T~ese outputs, however, are subtractively combined in the switching stage 8 to produce a first position signal that is indicative of the position of a seam relative to the two transducers 5. This signal ~l~llZ9 .
will have a particular value, for example, zero for a balanced position, which is, in fact, an off center position for each of the transducers of ~ -the pair. Since, however, the gain of the amplifiers 7 and the transducer characteristics may differ, a central position of the welding seam above the midpoint between the two transducers 5 may produce a nonzero signal.
Due to the differential mode employed here, this resulting signal is independent to a considerable degree from variations in the seam width as well as to variations in the radial projection of the weld bead.
A command signal is derived from a stage 12 which is subtractively combined with the combined outputs of amplifiers 7 so that an error signal is produced. That error signal is zero for the balanced position. Should for any reason the welding seam deviate from the balanced position, then -the output of the two amplifiers 7 changes in opposite directions, and the combined signal deviates from the adjusted reference signal, resulting in a nonzero error signal.
That error signal is used to control an electrical/hydraulic servo system 11, whose basic function is to keep the several transducers of the ultrasonic test equipment in alignment with the welding seam. This can be done, basically, in two ways. Either, the pipe rotating device causes the pipe to turn a little in one or the other direction depending upon the sign of the error signal, or the ultrasonic test equipment is pivoted, in effect, on an axis that coincides with the pipe's axis so that the test equipment, in fact, tracks the seam. Considering the latter case, if the stand la and case 1 is pivoted together with the test equipment, one will operate in a closed loop configuration. The same is true if the pipe is rotated. If the stand la is not turned with the test equipment, the control is an open loop one. It should be noted that pivoting of the common table requires -pivoting about the table axis and lateral displacement of the ~ 5 ~
.~
~.
, "`" ~11~12~1 carriage to arrive at a pivot motion about the pipe's axis. In either case, ball rollers 10, as per Figure 1, fulfill an important function in that they maintain specific distance orientation and positioning of the tracking equipment relative to the pipe's surface. Thestandla should, therefore, be continuously upwardly biased.
It can readily be seen that the range of seam position deviation, which can be ascertained, is limited. When the seam has practically left the range of one transducer 5, and its center has passed over the center of the other transducer, the error signal begins to decline though the error has increased further. Now, one of the transducers 6 takes over as the seam enters its detection range (or, to be more precise, causes the -transducer to more significantly respond to the scan. The transducers 6 are farther from the pipe's surface and are, therefore, less sensitive but respond to a larger angular range of seam positions).
The two transducers 6 are connected to amplifiers 7, each pro-,. . . .
ducing a more significant output ~higher gain) to be individually super-imposed upon the error signal as generated in stage 8. The gain is chosen so that the now declining (positively or negatively) combined signal from ` amplifiers 7 is augmented so that the resulting signal (as combined with the command signal from stage 12) is, in fact, indicative of the fact that the error is now quite large.
As indicated schematically, the various gain parameters should be adjustable as per a stage 13, and an instrument being connected to the error signal line that interconnects stages 8 and 12, indicates the error signal.
~, The output of the error signal amplifier stage in unit 8 should be connected to a turn-off device with threshold response, responding when , .
~ the pipe's seam has wandered off so that its center is about centered above 1,~
. .
1:~
,:
i~ - 6 --~l~llZ9 one or the other of the two detectors 6. Further rotational displacement will no longer yield a correct result, the apparatus should be turned off and further pipe advance should be halted, because some further correction is needed.
The case 1 includes also a pressure line system for pressurized air, and suitably oriented nozzles are directed towards the transducers to ~eep them clean on a continuing basis.
In operation, the system works as follows for practicing the method as per the present invention. A pipe is longitudinally advanced so that its front end just clears transducer 2. Next, the pipe rotating device 23 is raised to lift the pipe off the longitudinal conveyor 21. Thereafter (or in conjunction therewith), the casing 1 is raised so that balls 10 engage the - pipe and transducer 2 with associated circuit is turned on; also, the pipe ~ -rotating device 23 is turned on. When the transducer 2 responds, switching circuit 4 turns the pipe rotating device 23 off, and the pipe is lowered back onto the conveyor, but the casing 1 remains in engagement with the pipe.
The pipe is now longitudinally advanced towards the ultrasonic equipment in the test stand, a~d the seam follower control is turned on. It sh'ould be noted that all these functions are controlled by the switching device 4, whereby pipe lowering, advance turn on, and seam follower control turn on may be sequenced to avoid incorrect responses. Notably, however, the stand la is biased upwardly so that the balls 10 retain the transducers 2, 5, 6 in the particular distance relation to the pipe's surface.
The seam finding and locating step has placed the seam into such an alignment so that transducers 5 scan along the seam edges. The disposi-tion of the transducers 6 is chosen so that the seam remains entirely or substantially entirely outside of their detection area. If, for any reason, -the pipe tends to turn, the two transducers 5 will change outputs in phase : .
opposition resulting in a first error signal tending to operate the adjustment - -. ' llZ9 ment device 11 so that the test equipment tracks the seam. If we operate in closed loop, the error signal will be reduced to ~ero by the corrective action.
Further rotational displacement of the pipe will cause the pipe's seam to recede entirely from one of the transducers 5, while the other one tends to produce an output which,i n terms of the error signal, tends to indicate a smaller error. This, of course, could be incorrect and now one of the transducers 6 comes into play whose output is superimposed upon the error signal as produced by the two transducers 5 so that in total a large error is indicated. At a certain error maximum, the device may be stopped as further tracking is not possible, and some other corrective action has to - be taken. It will be seen that any irregularities in the welding seam region are being ascertained in the stated manner, such as plate edge offset or other irregularities in the joint, having a bearing on the geometry of the J~ welding zone. On the other hand, variations in bead width are not ascer-tained, as they have no bearing on the desired and required geometry of the -test equipment and its orientation to the seam. It was found that the tracking accuracy is about ~1 mm which amply suffices for the purpose of the test system.
~ 20 Variations in bead thickness have also no bearing on the general ;~ orientation of the seam, but may influence the ultrasonic test procedure otherwise. It should be noted that using the output of transducer 2, one ~ obtains a running indication of relative bead thickness (variations larger i ~ than about 1 mm), as the head of the bead will vary in distance from ~;
transducer 2. This may constitute valuable information for the test evalua-tion.
I ~ .
After the rear end of the pipe clears any of the transducers, e~g~. transducer 2, the output thereof being a well pronounced stress signal, can be used as turn-off signal for the tracking control. The circuit 8 :
~ .
coule be implemented digitally in that the value amplified transducer signals are digitized and processed, i.e. added, and subtracted digitally.
:
g _
Claims (9)
PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. Apparatus for finding and following a weld seam on a pipe in the non-destructive testing of the seam, which apparatus comprises a housing supporting a first path pickup for detecting a said seam and second path pickups for following said seam and an electrical circuit interlocking the pickups whereby the first pickup monitors the location of the seam and the second pickups control the relative orientation of a said seam with respect to the housing as a said pipe is moved axially relative to the housing.
2. Apparatus according to Claim 1 wherein each path pickup operates inductively to determine its spacing from the weld seam.
3. Apparatus according to Claim 1 wherein each path pickup is an ana-log path pickup and is connected to an associated pre-amplifier.
4. Apparatus according to Claim 1 or 2 or 3 wherein the path pickups are supported in a common insert removably mounted in the housing.
5. Apparatus according to Claim 1 or 2 or 3 including a plurality of roller bearing elements mounted in the housing for engaging the external surface of a said pipe for maintaining said surface spaced from the path pickups.
6. Apparatus according to Claim 1 or 2 or 3 including means for con-tinuously directing a stream of compressed air past the path pickups to clean same.
7. A method of finding and following a weld seam on a pipe in the non-destructive testing of the weld seam, which method comprises rotating the pipe relative to a housing to locate the seam with respect thereto by means of a first pickup mounted in the housing; halting rotation of the pipe;
moving the pipe axially relative to the housing; and controlling the angular position of the pipe with respect to the housing during such axial movement by means of at least two second path pickups also mounted in the housing, the first and second path pickups being operatively interconnected to align the seam with a non-destructive testing device therefor.
moving the pipe axially relative to the housing; and controlling the angular position of the pipe with respect to the housing during such axial movement by means of at least two second path pickups also mounted in the housing, the first and second path pickups being operatively interconnected to align the seam with a non-destructive testing device therefor.
8. A process according to Claim 7 wherein each pickup operates induc-tively to determine its spacing from the weld seams.
9. A process according to Claim 7 or Claim 8 wherein the pickups are continuously cleaned by a stream of compressed air while the method is carried out.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19762642481 DE2642481C3 (en) | 1976-09-17 | 1976-09-17 | Method and device for aligning a US test facility |
| DEP2642481.7-52 | 1976-09-17 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1111129A true CA1111129A (en) | 1981-10-20 |
Family
ID=5988471
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA286,918A Expired CA1111129A (en) | 1976-09-17 | 1977-09-16 | Finding and tracking the welding seam of pipes to be inspected by ultrasonic test equipment |
Country Status (6)
| Country | Link |
|---|---|
| JP (1) | JPS5338393A (en) |
| CA (1) | CA1111129A (en) |
| DE (1) | DE2642481C3 (en) |
| FR (1) | FR2365155A1 (en) |
| GB (1) | GB1581959A (en) |
| IT (1) | IT1084749B (en) |
Families Citing this family (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS56168214A (en) * | 1980-05-29 | 1981-12-24 | Idec Izumi Corp | Process step-forward type sequence controller |
| JPS56168217A (en) * | 1980-12-19 | 1981-12-24 | Idec Izumi Corp | Process step-forward type sequence controller |
| JPS56168219A (en) * | 1980-12-19 | 1981-12-24 | Idec Izumi Corp | Process step-forward type sequence controller |
| JPS56168220A (en) * | 1980-12-19 | 1981-12-24 | Idec Izumi Corp | Process step-forward type sequence controller |
| JPS56168216A (en) * | 1980-12-19 | 1981-12-24 | Idec Izumi Corp | Process step-forward type sequence controller |
| JPS56168215A (en) * | 1980-12-19 | 1981-12-24 | Idec Izumi Corp | Process step-forward type sequence controller |
| JPS56168218A (en) * | 1980-12-19 | 1981-12-24 | Idec Izumi Corp | Process step-forward type sequence controller |
| JPS57111704A (en) * | 1980-12-29 | 1982-07-12 | Idec Izumi Corp | Process count-up type sequence controller |
| DE102013106475A1 (en) * | 2013-06-20 | 2014-12-24 | Intelligendt Systems & Services Gmbh | Testing device for non-destructive testing of a component of a rolling bearing, rolling bearing and wind turbine |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR1390463A (en) * | 1963-02-12 | 1965-02-26 | J U H Krautkramer Ges Fuer Ele | Ultrasonic weld line inspection process |
| JPS4311750Y1 (en) * | 1964-04-14 | 1968-05-21 | ||
| US3346807A (en) * | 1964-04-24 | 1967-10-10 | American Mach & Foundry | Reciprocating apparatus with means to maintain the reciprocation centered over an anomaly |
| LU61704A1 (en) * | 1970-09-17 | 1972-06-27 | ||
| DE2239735A1 (en) * | 1972-08-12 | 1974-02-21 | Krautkraemer Gmbh | SYSTEM FOR DETECTION AND ULTRASONIC TESTING OF WELD SEAMS |
| JPS5742208B2 (en) * | 1974-08-27 | 1982-09-07 |
-
1976
- 1976-09-17 DE DE19762642481 patent/DE2642481C3/en not_active Expired
-
1977
- 1977-09-08 GB GB3758777A patent/GB1581959A/en not_active Expired
- 1977-09-15 FR FR7727863A patent/FR2365155A1/en active Granted
- 1977-09-16 CA CA286,918A patent/CA1111129A/en not_active Expired
- 1977-09-16 JP JP11150277A patent/JPS5338393A/en active Pending
- 1977-09-16 IT IT2762377A patent/IT1084749B/en active
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5338393A (en) | 1978-04-08 |
| DE2642481B2 (en) | 1979-09-13 |
| FR2365155A1 (en) | 1978-04-14 |
| DE2642481C3 (en) | 1984-04-05 |
| GB1581959A (en) | 1980-12-31 |
| IT1084749B (en) | 1985-05-28 |
| FR2365155B1 (en) | 1984-01-06 |
| DE2642481A1 (en) | 1978-03-23 |
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