CA1129960A - Coreless flaw detection head - Google Patents
Coreless flaw detection headInfo
- Publication number
- CA1129960A CA1129960A CA317,095A CA317095A CA1129960A CA 1129960 A CA1129960 A CA 1129960A CA 317095 A CA317095 A CA 317095A CA 1129960 A CA1129960 A CA 1129960A
- Authority
- CA
- Canada
- Prior art keywords
- main body
- coreless
- flaw detection
- detection head
- cover member
- 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
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- Investigating Or Analyzing Materials By The Use Of Magnetic Means (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE:
A coreless flaw detection head adapted to detect a flaw or flaws which may be present on the inner surface of a non-magnetic metal pipe and variation in the wall thickness of the pipe which comprises a cylindrical main body having first annular grooves adjacent to one end and a second annular groove adjacent to the other end, differential system detection coils received in said first annular grooves, an absolute value system detection coil, a sheath surrounding a substantial portion of the length of said main body, a substantially hollow cylindrical cover member on said other end of the main body and protection rings on said one end of the main body and on the end of said cover member opposite to said main body.
A coreless flaw detection head adapted to detect a flaw or flaws which may be present on the inner surface of a non-magnetic metal pipe and variation in the wall thickness of the pipe which comprises a cylindrical main body having first annular grooves adjacent to one end and a second annular groove adjacent to the other end, differential system detection coils received in said first annular grooves, an absolute value system detection coil, a sheath surrounding a substantial portion of the length of said main body, a substantially hollow cylindrical cover member on said other end of the main body and protection rings on said one end of the main body and on the end of said cover member opposite to said main body.
Description
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This invention relates to a coreless flaw detection head for detecting a flaw or flaws which may be present on the inner surface of a non-magnetic metal pipe of small diameter and more particularly, to a coreless flaw detection head for detecting a flaw or flaws which may be present on the inner surface of a non-magnetic metal pipe of small diameter such as 20 - 25 mm, for example, by the impedance metal flaw detection method whereby two different types of flaw wave forms are simultaneously indicated and recorded for comparison.
The prior art coreless flaw detection heads of the type referred to above are generally designed to perform detection by the differential system and the absolute value system.
The former type detection system is designed to numerically detect a flaw of flaws on the inner surface of a non-magnetic metal pipe and indicate the sum of the detection results. However, the differential type detection system has the disadvantage that the system is applicable to detect only flaws positioned adjacent to each other and flaws having shallow depths and large areas which may be present on the inner surface of a metal pipe, but not to the d tection of variation in the wall thickness of the pipe. ~urthermore, this type of detection system requires a difficult discrimination procedure in detecting flaws on the pipe such as those due to ammonia attack or inlet attack. The latter or absolute value type flaw detection system has excellent electromagnetic wave permeability and exhibits satisfactory detection character-istic in detecting variation in the wall thickness of a pipe to be detected, but can not finely detect a flaw or flaws which may be present on the inner surface of the pipe.
Any of the prior art flaw detection heads for non-magnetic metal pipes is designed to perform the two different .
~ 9~z~6~
, flaw detection procedures by switchin~ the electrical circuit of a probe coil and therefore, requires to per~orm the detection operation two times~ Thus, the.prior art ~law detection head referred to above has the disadva~.ta~es that the flaw detection takes rather much time and labor and the detection results obtained by t~e dif~erential and abso~ute value detection systems frequently do not coin.cide ~ith each other.
There~ore, the purpose of the present invention is to provide a coreless flaw detection head which incorporates the differential and absolute value detection systems therein in : ~ -such a manner that two dif~erent detection xesults by the two -different detection systems are simultaneously~ indicated and recorded by two different types of wave ~orms representin~ a flaw or flaws present on the inner surface o~ a non.-magnetic - metal pipe and variation in the wa~l thickness o the pipe,~:
respectively, for comparison.
More specifically, and in accordance with the broad concept of the invention, there is provided and claimed herein a coreless flaw detection head for detecting flaws on the inner surface of a non-magnetic metal pipe and variations in the wall thickness of said pipe, comprising an electrically insulating solid cylindrical main body having opposite ends; first -longitudinally spaced annular grooves adjacent to one of said opposite ends and a second annular groove adjacent to the other of said opposite end~ differential system detection coils received in said first annular grooves; an absolute value system detection coil received in said second annular groove; an at least partially hollow electrically insulatin~ cover removably connected to the other of said opposite ends of said main body;
a cord extending axially through said cover member and having electric cores, and means in said body electrically connecting ,,~,~, .
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-said cores to said differential and. absolute.~aLue system detection coilsi and an outer sheath surxoundin.g a substantial.
portion of the length of said main body to protect s~id detection coils against wear and dama~e~
By the use of the flaw detection head of the i~vention t the detection results obtained by both the dif~erenti.a~ a~d absolute value detection systems may simu~ta,neously be indicated and recorded on recording means in verticall~ aligned positiops for comparison ~hereby the provision of a rather large number of parts or components and troublesome operation such as that to be performed by a shift switch as required in the prior art coxe~
less flaw detection heads can be eliminated. Fuxthex~ore, the hard sheath which surrounds a substantial portion of.the ~e~,gth of ~he cylindrical main body protects the detection coils against possible wear and damage to ensure a l,o~g sexvlce li~e o,f, the detection coils. In addition, stainLess.steel ~ings ~a~ be -' screwed on the oppos-ite ends of the main body to protect the main : body against possible wear and damage to en,sure a lo~g se~ice life of the main body.
~20- The above and other objects and atte~dant advantages of the present invention will be more readlly apparent to those skilled in the art from a reading of the following detailed : : description.in conjunction~with. the accompanylng drawings which . show one preferre~ embodiment o~ the invention for illustration .-.
purpose only, but not for limiting the scope of the same in any :~ way., ,~ Fig. 1 is a side elevational view of the preferred '-embodiment of the coreless pipe flaw detection, head of the : present in~ention;
Fig. 2 is a longitudinally sectional ~ie~ of said pipe flaw detection head as shown in Fi~. l;
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~2~ 0 , . , Fig. 3 is a partially exploded perspective yiew Of said pipe flaw detection head as shown in Fiq. 1 With the sheath thereof removed thereformi ' . \ '. ~ ,:
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Fig. 4 is a perfectly exploded perspective view of said pipe flaw detection head as shown in Fig. l;
Fig. 5 is a cross-sectional view taken along sub-stantially the line A - A of Fig. 2, Fig. 6 is a cross-sectional view taken along sub-stantially the line s - B of Fig. 2, Fig. 7 is a longitudinally sectional view on a reduced scale of said pipe flaw detection head as shown in Fig. 1 showing the head as being electrically connected to a standard for the so-called absolute value detection, and Figs. ~3A and 8B are charts showing the results of detection by said pipe flaw detection head.
The present invention will be now described referring to the accompanying drawings and more particularly, to Figs. 1 through 7 in which one preferred embodiment of the pipe flaw detection head constructed in accordance with the present invention is shown. The pipe flaw detection head is generally shown with reference numeral 1 and generally comprises a solid~cylindrical main body 2 formed of a suitable electrically insulative material such as synthetic resin, a substantially ~ hollow cylindrical cover member 3 in threaded engagement with :
the main body and formed of the same material as the latter and a sheath 4 surrounding a substantial portion of the length of the main body 2 and formed of a synthetic resin having a -:
hardness higher than that of the material of the main body and~cover member. The main body 2 is reduced in diameter at the opposite ends 9, 9a wh1ch are externally threaded and the cover member 3~has a stepped bore 10 including a larger dlameter ~ : :
bore portion which is internally threaded for threaded engage-ment with one or the inner~reduced diameter end 9 of the main body 2 and a smaller diameter bore portion. The outer end of the cover member 3 is reduced in diameter and externally 96~
threaded for the purpose to be described hereinafter.
The main body 2 is provided adjacent to the reduced diameter leading end 9a with two longitudinally spaced annular recesses 5, 5 in which differential system detection coils 6, 6 are received for detecting pipe flaws of shallow depths and large areas. The main body 2 is also provided adjacent to the reduced diameter rear end 9 with an annular recess 7 in which an absolute value system detection coil 8 is received for detecting variation in the wall thickness of a non-magnetic metal pipe to be detected for its flaw or flaws and variation in the pipe wall thickness.
A plurality of cord anchoring pins 13 (five anchoring pins in the illustrated embodiment) project from the rear end face of the main body inner end 9 and each of the five cores or lead wires 12 of a five-core electrical cord 11 extending through the stepped bore 10 in the cover member is soldered at one end to the corresponding anchoring pin 13. Three of the five lead wires 12 are electrically connected to the differential system detection coils 6, 6 and the remaining two lead wires are electrically connected to the absolute value system detection coil 8. One leading wire in each of the two groups of lead wires 12 associated with the differential system detectlon coils 6, 6 and absolute value system detection coils 8, 8, respectively, serves as the earth line. In Fig. 7, the earth lines are shown with reference n~meral 24 and the remain-ing lead wires are shown with reference numeral 28, respectively.
The~cover member 3 is provided with a plurality of through t~hreaded bores 14 extending radially to communicate with the smaller diameter bore portion ln the cover memker 3 (four threaded bores are provided in an equally circumferentially spaced relationship in the illustrated embodiment) and set screws lS are screwed in the respectively corresponding threaded ~ ~z~9~;0 bores 1~ to hold the five-core electrical cord 11 in position.
As more clearly shown in Fig. 4j an internally threaded first or leading ring 16 is in threaded engagement with the threaded leading end 9a of the main body 2 and a similarly threaded second or rear ring 18 is in threaded engagement with the reduced diameter threaded outer end 21 of the cover member 3. The first and second rings 16 and 18 are formed of a wear-resistance material such as stainless steel.
Referring again to Fig. 7, a standard 25 for the absolute value detection system is electrically connected to the absolute value detection coil 8 through the lead wire 28 and earth line 24 associated with the coil and a calibration coil 27 is wound about the reduced diameter portion of the standard 25. A control pipe 26 is disposed about the standard 25 surrounding the reference of calibration coil 27. The control pipe 26 is identical with a metal pipe (not shown) which is to be dete ted for its flaws and variation in the wall thickness, but free of defec-ts such as flaws and/or variation in the wall thickness. Any variation in the wall thickness of the metal pipe to be detected for its flaws and variation in the thickness is detected by comparising electro-magnetic waves provided by the reerence or calibration coil 27 with electromagnetic waves provided by the lead wire 28 associated with the absolute value detection system coil 8.
The operation of the flaw detection head of the present invention will be now described. The flaw detection head is inserted into a non-magnetic pipe the inner surface of which is to be detected for flaws and variation in -the wall thickness at one end of the pipe and moved along the pipe inner sùrface-to the other end of the pipe. When the detection head has reached the other end of the pipe, the measuring and recording device (not shown) electrically connected to the 96(~1 detection head through the five-core cord 11 and the bridye circuit (not shown) is actuated to energize the differential and absolute value detection coil systems and the detection head is then moved back along the pipe inner surface towards the first-mentioned end of the pipe. When A.C. electromagnetic waves generated by the differential detection system coils 6, 6 and/or electromagnetic waves generated by the absolute value detection system coil 8 encounter or detect flaws on the inner surface and/or variation in the wall thickness of the pipe, the electromagnetic waves provide impedances which vary depending upon the shape and size of the flaws and/or the amount of variation in the wall thickness and which are indicated and recorded on the recording device which is connect-ed to the cord 11 through the bridge circuit to thereby provide positive detection results representing the defects on the pipe such as flaws and/or variation in the wall thickness.
Figs. 8A and 8B a~e charts on which the wave forms representing the detection results obtained by the differential and absolute value detection systems are plotted. Fig. 8A
shows the wave forms of the absolute value detection system deflecting in one direction with respect to the reference line and Fig. 8s shows the wave forms of the differential detection system deflecting in the opposite directions with respect to the reference line.
As mentioned hereinabove, according to the coreless detection head of the present invention, both the differential detection system in which wave forms deflecting in the opposite directions with respect to the reference line are provided and the absolute valua detection system in which wave forms deflect-ing in one direction with respect to the reference line areprovided are incorporated in one coreless detection head to thereby make it possible to simultaneously detect a flaw or ~2~5~61~
flaws on the inner surface of a non-magnetic metal pipe and variation in the wall thickness of the pipe by passing the detection head through the pipe to be detected once. Therefore, the present invention provides practical and excellent effects that details of adjacent small size flaws, flaws of shallow depths and large areas on the inner surface of the pipe to be detected and defects within the material of the pipe as well as variation in the wall thickness of the pipe can be positively and simultaneously detected and recorded.
And since the coreless detection coils are employed in the detection head, the detection head is highly responsive to a reaction form a pipe to be detected for flaws on the inner surface thereof and/or variation in the wall thickness of the pipe and in despite of the fact that both the differen-tial and absolute value detection systems are incorporated in the slngle detection head, there will be no mutual interference between the actions of the two systems.
And since the outer surface of the cylindrical main body is provided adjacent to one end with two longitudinally spaced annular grooves and differential detection system coils are received in the annular grooves for de-tecting small size flaws and flaws having shallow depths and large areas, the detection head is quite responsive to the presence of defects on the inner surface of a pipe to be detected to thereby detect even small flaws of pitching shape. Electromagnetic waves generated from one of the absolute value system coils are caused to permeate into the material of a non-magnetic metal pipe to be detected to thereby precisely detect variation in the wall thickness of the pipe.
Furthermore, since the hard synthetic resin sheath is placed on the cylindrical main body to cover the detection coils wound about the main body, the sheath can positively z~
hold the coils under stabilized conditions to thereby sub-stantially improve the sensitivity of the detection head in response to any defect on the inner surface of a non-magnetic metal pipe. As compared with the prior art detection head having detection coils wound about the main body of the head are not covered by any cover member such as a sheath and easily subjected to wear and damage as the detection head is passed through the interior of a non-magnetic metal pipe to be detected for flaws on the inner surface thereof and variation in the wall thickness thereof, the detection head of the invention having the detection coils wound about the main body are protected by the sheath against possible wear and damage and free of being subjected to wear and damage as the detection head is passed through the interior of such pipe whereby the detection head can enjoy a long service life.
Furthermore, since the stainless steel rings are placed on the opposite ends thereof, the detection head can be positively protected against possible wear and damage at the ends to thereby ensure a long service life to the detection head. .
While only one embodiment of the invention has been shovn and described in detail, it will be understood that the same is for illustration purpose only and not to be taken as a definition of the invention, reference being had for this purpose to the appended claims.
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This invention relates to a coreless flaw detection head for detecting a flaw or flaws which may be present on the inner surface of a non-magnetic metal pipe of small diameter and more particularly, to a coreless flaw detection head for detecting a flaw or flaws which may be present on the inner surface of a non-magnetic metal pipe of small diameter such as 20 - 25 mm, for example, by the impedance metal flaw detection method whereby two different types of flaw wave forms are simultaneously indicated and recorded for comparison.
The prior art coreless flaw detection heads of the type referred to above are generally designed to perform detection by the differential system and the absolute value system.
The former type detection system is designed to numerically detect a flaw of flaws on the inner surface of a non-magnetic metal pipe and indicate the sum of the detection results. However, the differential type detection system has the disadvantage that the system is applicable to detect only flaws positioned adjacent to each other and flaws having shallow depths and large areas which may be present on the inner surface of a metal pipe, but not to the d tection of variation in the wall thickness of the pipe. ~urthermore, this type of detection system requires a difficult discrimination procedure in detecting flaws on the pipe such as those due to ammonia attack or inlet attack. The latter or absolute value type flaw detection system has excellent electromagnetic wave permeability and exhibits satisfactory detection character-istic in detecting variation in the wall thickness of a pipe to be detected, but can not finely detect a flaw or flaws which may be present on the inner surface of the pipe.
Any of the prior art flaw detection heads for non-magnetic metal pipes is designed to perform the two different .
~ 9~z~6~
, flaw detection procedures by switchin~ the electrical circuit of a probe coil and therefore, requires to per~orm the detection operation two times~ Thus, the.prior art ~law detection head referred to above has the disadva~.ta~es that the flaw detection takes rather much time and labor and the detection results obtained by t~e dif~erential and abso~ute value detection systems frequently do not coin.cide ~ith each other.
There~ore, the purpose of the present invention is to provide a coreless flaw detection head which incorporates the differential and absolute value detection systems therein in : ~ -such a manner that two dif~erent detection xesults by the two -different detection systems are simultaneously~ indicated and recorded by two different types of wave ~orms representin~ a flaw or flaws present on the inner surface o~ a non.-magnetic - metal pipe and variation in the wa~l thickness o the pipe,~:
respectively, for comparison.
More specifically, and in accordance with the broad concept of the invention, there is provided and claimed herein a coreless flaw detection head for detecting flaws on the inner surface of a non-magnetic metal pipe and variations in the wall thickness of said pipe, comprising an electrically insulating solid cylindrical main body having opposite ends; first -longitudinally spaced annular grooves adjacent to one of said opposite ends and a second annular groove adjacent to the other of said opposite end~ differential system detection coils received in said first annular grooves; an absolute value system detection coil received in said second annular groove; an at least partially hollow electrically insulatin~ cover removably connected to the other of said opposite ends of said main body;
a cord extending axially through said cover member and having electric cores, and means in said body electrically connecting ,,~,~, .
, - ~ 996~
-said cores to said differential and. absolute.~aLue system detection coilsi and an outer sheath surxoundin.g a substantial.
portion of the length of said main body to protect s~id detection coils against wear and dama~e~
By the use of the flaw detection head of the i~vention t the detection results obtained by both the dif~erenti.a~ a~d absolute value detection systems may simu~ta,neously be indicated and recorded on recording means in verticall~ aligned positiops for comparison ~hereby the provision of a rather large number of parts or components and troublesome operation such as that to be performed by a shift switch as required in the prior art coxe~
less flaw detection heads can be eliminated. Fuxthex~ore, the hard sheath which surrounds a substantial portion of.the ~e~,gth of ~he cylindrical main body protects the detection coils against possible wear and damage to ensure a l,o~g sexvlce li~e o,f, the detection coils. In addition, stainLess.steel ~ings ~a~ be -' screwed on the oppos-ite ends of the main body to protect the main : body against possible wear and damage to en,sure a lo~g se~ice life of the main body.
~20- The above and other objects and atte~dant advantages of the present invention will be more readlly apparent to those skilled in the art from a reading of the following detailed : : description.in conjunction~with. the accompanylng drawings which . show one preferre~ embodiment o~ the invention for illustration .-.
purpose only, but not for limiting the scope of the same in any :~ way., ,~ Fig. 1 is a side elevational view of the preferred '-embodiment of the coreless pipe flaw detection, head of the : present in~ention;
Fig. 2 is a longitudinally sectional ~ie~ of said pipe flaw detection head as shown in Fi~. l;
~ .
~2~ 0 , . , Fig. 3 is a partially exploded perspective yiew Of said pipe flaw detection head as shown in Fiq. 1 With the sheath thereof removed thereformi ' . \ '. ~ ,:
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3a -.~ .
... . . . .
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Fig. 4 is a perfectly exploded perspective view of said pipe flaw detection head as shown in Fig. l;
Fig. 5 is a cross-sectional view taken along sub-stantially the line A - A of Fig. 2, Fig. 6 is a cross-sectional view taken along sub-stantially the line s - B of Fig. 2, Fig. 7 is a longitudinally sectional view on a reduced scale of said pipe flaw detection head as shown in Fig. 1 showing the head as being electrically connected to a standard for the so-called absolute value detection, and Figs. ~3A and 8B are charts showing the results of detection by said pipe flaw detection head.
The present invention will be now described referring to the accompanying drawings and more particularly, to Figs. 1 through 7 in which one preferred embodiment of the pipe flaw detection head constructed in accordance with the present invention is shown. The pipe flaw detection head is generally shown with reference numeral 1 and generally comprises a solid~cylindrical main body 2 formed of a suitable electrically insulative material such as synthetic resin, a substantially ~ hollow cylindrical cover member 3 in threaded engagement with :
the main body and formed of the same material as the latter and a sheath 4 surrounding a substantial portion of the length of the main body 2 and formed of a synthetic resin having a -:
hardness higher than that of the material of the main body and~cover member. The main body 2 is reduced in diameter at the opposite ends 9, 9a wh1ch are externally threaded and the cover member 3~has a stepped bore 10 including a larger dlameter ~ : :
bore portion which is internally threaded for threaded engage-ment with one or the inner~reduced diameter end 9 of the main body 2 and a smaller diameter bore portion. The outer end of the cover member 3 is reduced in diameter and externally 96~
threaded for the purpose to be described hereinafter.
The main body 2 is provided adjacent to the reduced diameter leading end 9a with two longitudinally spaced annular recesses 5, 5 in which differential system detection coils 6, 6 are received for detecting pipe flaws of shallow depths and large areas. The main body 2 is also provided adjacent to the reduced diameter rear end 9 with an annular recess 7 in which an absolute value system detection coil 8 is received for detecting variation in the wall thickness of a non-magnetic metal pipe to be detected for its flaw or flaws and variation in the pipe wall thickness.
A plurality of cord anchoring pins 13 (five anchoring pins in the illustrated embodiment) project from the rear end face of the main body inner end 9 and each of the five cores or lead wires 12 of a five-core electrical cord 11 extending through the stepped bore 10 in the cover member is soldered at one end to the corresponding anchoring pin 13. Three of the five lead wires 12 are electrically connected to the differential system detection coils 6, 6 and the remaining two lead wires are electrically connected to the absolute value system detection coil 8. One leading wire in each of the two groups of lead wires 12 associated with the differential system detectlon coils 6, 6 and absolute value system detection coils 8, 8, respectively, serves as the earth line. In Fig. 7, the earth lines are shown with reference n~meral 24 and the remain-ing lead wires are shown with reference numeral 28, respectively.
The~cover member 3 is provided with a plurality of through t~hreaded bores 14 extending radially to communicate with the smaller diameter bore portion ln the cover memker 3 (four threaded bores are provided in an equally circumferentially spaced relationship in the illustrated embodiment) and set screws lS are screwed in the respectively corresponding threaded ~ ~z~9~;0 bores 1~ to hold the five-core electrical cord 11 in position.
As more clearly shown in Fig. 4j an internally threaded first or leading ring 16 is in threaded engagement with the threaded leading end 9a of the main body 2 and a similarly threaded second or rear ring 18 is in threaded engagement with the reduced diameter threaded outer end 21 of the cover member 3. The first and second rings 16 and 18 are formed of a wear-resistance material such as stainless steel.
Referring again to Fig. 7, a standard 25 for the absolute value detection system is electrically connected to the absolute value detection coil 8 through the lead wire 28 and earth line 24 associated with the coil and a calibration coil 27 is wound about the reduced diameter portion of the standard 25. A control pipe 26 is disposed about the standard 25 surrounding the reference of calibration coil 27. The control pipe 26 is identical with a metal pipe (not shown) which is to be dete ted for its flaws and variation in the wall thickness, but free of defec-ts such as flaws and/or variation in the wall thickness. Any variation in the wall thickness of the metal pipe to be detected for its flaws and variation in the thickness is detected by comparising electro-magnetic waves provided by the reerence or calibration coil 27 with electromagnetic waves provided by the lead wire 28 associated with the absolute value detection system coil 8.
The operation of the flaw detection head of the present invention will be now described. The flaw detection head is inserted into a non-magnetic pipe the inner surface of which is to be detected for flaws and variation in -the wall thickness at one end of the pipe and moved along the pipe inner sùrface-to the other end of the pipe. When the detection head has reached the other end of the pipe, the measuring and recording device (not shown) electrically connected to the 96(~1 detection head through the five-core cord 11 and the bridye circuit (not shown) is actuated to energize the differential and absolute value detection coil systems and the detection head is then moved back along the pipe inner surface towards the first-mentioned end of the pipe. When A.C. electromagnetic waves generated by the differential detection system coils 6, 6 and/or electromagnetic waves generated by the absolute value detection system coil 8 encounter or detect flaws on the inner surface and/or variation in the wall thickness of the pipe, the electromagnetic waves provide impedances which vary depending upon the shape and size of the flaws and/or the amount of variation in the wall thickness and which are indicated and recorded on the recording device which is connect-ed to the cord 11 through the bridge circuit to thereby provide positive detection results representing the defects on the pipe such as flaws and/or variation in the wall thickness.
Figs. 8A and 8B a~e charts on which the wave forms representing the detection results obtained by the differential and absolute value detection systems are plotted. Fig. 8A
shows the wave forms of the absolute value detection system deflecting in one direction with respect to the reference line and Fig. 8s shows the wave forms of the differential detection system deflecting in the opposite directions with respect to the reference line.
As mentioned hereinabove, according to the coreless detection head of the present invention, both the differential detection system in which wave forms deflecting in the opposite directions with respect to the reference line are provided and the absolute valua detection system in which wave forms deflect-ing in one direction with respect to the reference line areprovided are incorporated in one coreless detection head to thereby make it possible to simultaneously detect a flaw or ~2~5~61~
flaws on the inner surface of a non-magnetic metal pipe and variation in the wall thickness of the pipe by passing the detection head through the pipe to be detected once. Therefore, the present invention provides practical and excellent effects that details of adjacent small size flaws, flaws of shallow depths and large areas on the inner surface of the pipe to be detected and defects within the material of the pipe as well as variation in the wall thickness of the pipe can be positively and simultaneously detected and recorded.
And since the coreless detection coils are employed in the detection head, the detection head is highly responsive to a reaction form a pipe to be detected for flaws on the inner surface thereof and/or variation in the wall thickness of the pipe and in despite of the fact that both the differen-tial and absolute value detection systems are incorporated in the slngle detection head, there will be no mutual interference between the actions of the two systems.
And since the outer surface of the cylindrical main body is provided adjacent to one end with two longitudinally spaced annular grooves and differential detection system coils are received in the annular grooves for de-tecting small size flaws and flaws having shallow depths and large areas, the detection head is quite responsive to the presence of defects on the inner surface of a pipe to be detected to thereby detect even small flaws of pitching shape. Electromagnetic waves generated from one of the absolute value system coils are caused to permeate into the material of a non-magnetic metal pipe to be detected to thereby precisely detect variation in the wall thickness of the pipe.
Furthermore, since the hard synthetic resin sheath is placed on the cylindrical main body to cover the detection coils wound about the main body, the sheath can positively z~
hold the coils under stabilized conditions to thereby sub-stantially improve the sensitivity of the detection head in response to any defect on the inner surface of a non-magnetic metal pipe. As compared with the prior art detection head having detection coils wound about the main body of the head are not covered by any cover member such as a sheath and easily subjected to wear and damage as the detection head is passed through the interior of a non-magnetic metal pipe to be detected for flaws on the inner surface thereof and variation in the wall thickness thereof, the detection head of the invention having the detection coils wound about the main body are protected by the sheath against possible wear and damage and free of being subjected to wear and damage as the detection head is passed through the interior of such pipe whereby the detection head can enjoy a long service life.
Furthermore, since the stainless steel rings are placed on the opposite ends thereof, the detection head can be positively protected against possible wear and damage at the ends to thereby ensure a long service life to the detection head. .
While only one embodiment of the invention has been shovn and described in detail, it will be understood that the same is for illustration purpose only and not to be taken as a definition of the invention, reference being had for this purpose to the appended claims.
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Claims (8)
1. A coreless flaw detection head for detecting flaws on the inner surface of a non-magnetic metal pipe and variations in the wall thickness of said pipe, comprising an electrically insulating solid cylindrical main body having opposite ends; first longitudinally spaced annular grooves adjacent to one of said opposite ends and a second annular groove adjacent to the other of said opposite end; differential system detection coils received in said first annular grooves;
an absolute value system detection coil received in said second annular groove; an at least partially hollow electrically insulating cover removably connected to the other of said opposite ends of said main body; a cord extending axially through said cover member and having electric cores, and means in said body electrically connecting said cores to said dif-ferential and absolute value system detection coils; and an outer sheath surrounding a substantial portion of the length of said main body to protect said detection coils against wear and damage.
an absolute value system detection coil received in said second annular groove; an at least partially hollow electrically insulating cover removably connected to the other of said opposite ends of said main body; a cord extending axially through said cover member and having electric cores, and means in said body electrically connecting said cores to said dif-ferential and absolute value system detection coils; and an outer sheath surrounding a substantial portion of the length of said main body to protect said detection coils against wear and damage.
2. The coreless flaw detection head as set forth in claim 1, in which said main body and cover member are formed of the same synthetic resin and said outer sheath is formed of a synthetic resin having a hardness higher than that of the synthetic resin of the main body and cover member.
3. The coreless flaw detection head as set forth in claim 1, in which the said other end of the main body is of reduced diameter and is externally threaded and the inside of said hollow cover member is threaded at one end for threaded engagement with said externally threaded other end of the main body.
4. The coreless flaw detection, head as set forth in claim 3, in which said one end of said main, body and the outer end of said cover are reduced in diameter and outwardly threaded and a first and a second protection ring are screwed on said reduced diameter ends.
5. The coreless flaw detection head as set forth in claim 1, in which said cord has five cores of which three are electrically connected to said differential system detection coils and the remaining two are electrically-connected to said absolute value system detection coil through said core con-necting means in said body.
6. The coreless flaw detection head as set forth in claim 5, in which one of said cores associated with said dif-ferential system detection coils is an earth line and one of said cores associated with said absolute value system detection coils is an earth line.
7. The coreless flaw detection head as set forth in claim 1, in which a plurality of radially extending threaded bores are formed in said cover member to communicate with the interior of the cover member and a corresponding number of set screws are screwed in said radially extending threaded bores to hold said electric cord in position.
8. The coreless flaw detection head as set forth in claim 4, in which said first and second protection rings are formed of stainless steel.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA317,095A CA1129960A (en) | 1978-11-29 | 1978-11-29 | Coreless flaw detection head |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA317,095A CA1129960A (en) | 1978-11-29 | 1978-11-29 | Coreless flaw detection head |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1129960A true CA1129960A (en) | 1982-08-17 |
Family
ID=4113037
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA317,095A Expired CA1129960A (en) | 1978-11-29 | 1978-11-29 | Coreless flaw detection head |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1129960A (en) |
-
1978
- 1978-11-29 CA CA317,095A patent/CA1129960A/en not_active Expired
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| Date | Code | Title | Description |
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| MKEX | Expiry |