GB1584733A - Magnetic inspection method and apparatus for inner surface of pipe - Google Patents

Description

(54) MAGNETIC INSPECTION METHOD AND APPARATUS FOR INNER SURFACE OF PIPE (71) We, SUMITOMO KINZOKU KOGYO KABUSHIKI KAISHA of 15-banchi, Kitahama 5-chome, Higashi-ku, Osaka-shi, Osaka-fu, Japan, a Japanese company, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to a magnetic flaw detector which is useful for detecting flaws present on or in the inner surface of a steel pipe having a small diameter and a considerable length.

The inventors have developed a magnetic inspection apparatus for detecting flaws present on the outer surface of solid steel bodies, or flaws present on the outer or inner surface of a steel pipe.

The principle of these apparatuses is that a strong magnetic field is produced on a surface to be inspected, by an exciting magnet, and the magnetism-sensitive ele ment is placed in the magnetic field thus produced for detecting a magnetic flux leaking from. the position of a flaw present on the surface of a material to be inspected.

According to the invention there is pro vided a magnetic flaw detector for the inner surface of a pipe, comprising: a support rod mounted on a wheeled carriage which is movable along a rail, said support rod having a hollow space at least in the fore end portion thereof to be inserted into said pipe and a window fonned in said fore end portion for facing the inner wall surface of said pipe; a detector assembly having a base plate accommodated within said hollow space at the fore end of said support rod and movable radially of said support rod, a plurality of detecting members mounted on said base plate in alignment in the longitudinal direction of said support rod, each of said detecting members having a magneto-sensitive element facing through said window toward the inner surface of said pipe, and a plurality of guide rollers mounted on said base plate which can be brought into rolling contact with the inner surface of said pipe when said detecting members are abutted against the inner surface of said pipe;; a guide mechanism having a support frame attached to the fore end of said support rod and swingable in a direction opposite to the facing direction of said magneto-sensitive elements, and a guide roller adapted to be brought into rolling contact with the inner surface of said pipe to support said support rod when said support frame is swung; a magnetizing assembly having a magnetizing head mounted on a wheeled carriage movable with the first-mentioned wheeled carriage along said rail and movable toward and away from the outer surface of said pipe, DC exciting magnets mounted on said magnetizing head, said magnets opposing said magneto-sensitive elements across the wall of said pipe, and follower rollers adapted to be brought into rolling contact with the outer surface of said pipe to support said exciting magnets in the vicinity of the outer surface of said pipe; and means for rotating said pipe about the axis thereof.

An example of the invention will now be described with reference to the accom panying drawings in which: Fig. 1 is a side view of one embodiment of a magnetic inspection apparatus for detecting flaws present on or in the inner surface of a pipe according to the present invention; Fig. 2 is a side view showing an exciting mechanism portion and a tip portion of the supporting rod; Fig. 3 is an enlarged front view showing an exciting mechanism portion; Fig. 4 is an enlarged cross-sectional view showing a detecting mechanism portion provided within a supporting rod, and a guide mechanism portion provided on the tip portion of thy supporting rod;; Fig. 5 is a cross sectional view, whose right hand half illustrates the right hand cross section taken along the line VR-VR of Fig. 4, and whose left hand half iflu- strates the left hand cross section taken along the line VL-VL of Fig. 4.

An exciting mechanism portion I travels along the outer surface of a pipe, while a detecting mechanism portion 7 is built in a tip portion of a supporting rod inserted in the pipe. In addition, the exciting mechanism portion 1 and detecting mechanism portion 7 are operably coupled through the medium of a connecting rod 6 in synchronism with each other. The exciting mechanism portion 1 is supported from a wheeled overhead carriage means 4 adapted to travel along a rail 3 secured to a beam of frame 2. In addition, the wheeled carriage means 4 is coupled through the medium of a connecting rod 6 to a wheeled overhead carriage means 5 adapted to travel along the rail 3 and positioned rearwardly of the wheeled carriage means 4.A supporting portion 10 is removably suspended from the wheeled carriage means 5 and formed with a supporting rod 9 having a detecting mechanism portion 7 and guide mechanism portion 8 in a tube portion near the tip thereof.

Positioned on a floor immediately under the rail 3 is a support 13 having a roller 12 on its top, with the supporting rod 9 being supported on the roller 12 in a manner to travel therealong.

A steel pipe 14 to be inspected is supported on rollers 16 which are rotatably driven and supported on the top portions of supports 15 provided on the floor immediately under the rail 3. Thus the detecting mechanism portion 7 and guide mechanism portion 8, along with the supporting rod 9, are inserted into a steel pipe which is being rotated on the rollers 16, while the exciting mechanism portion 1 travels along the outer surface of the pipe, so that the inner surface of the pipe may be closely detected for flaws foTlowing a spiral pattern.

Meanwhile, the wheeled carriage means 4,5 are coupled to a chain or cable which is driven by a motor or the like and adapted to travel along the rails 3.

The excitina mechanism portion 1 includes: an exciting head 19 pivoted to the tip portion of a suspension shaft 18 which may be vertically movable by means of a cylinder 17 mounted on the wheeled carriage means 4: and follower rollers 22A, 22B mounted on a base plate 21 which may be moved vertically by means of a cylinder 20 which in turn is mounted on the exciting head 19. The exciting head 19 includes a pair of exciting magnets 24 extending through exciting coil 23, respectively, following a V-shaped pattern by being positioned in symmetric relation to an inspecting position of a steel pipe 14.

In addition, the exciting magnets 24 have their rear end portions threaded into a threaded shaft 26 adapted to be turned by means of a handle 25, so that the magnet 24 may slide for positional adjustment in the axial direction due to the rotation of the handle 25.

The follower rollers 22A, 2213 may be turned about their supporting shafts so as to accommodate themselves to spiral feeding of the pipe 14 at any pitch, while one of the rollers 22A, 22B is supported in the vertical direction, and the other is supported in the horizontal direction.

Positioned in surrounding relation to the suspension shaft 18 is a spring 27 for providing a damping action to the steel pipe 14, when the rollers 22A, 22B contact the steel pipe 14. Alternatively, if the cylinder 17 is so designed as to provide an air cushion, then the spring 27 may be eliminated.

The exciting coil 23 is D.C. excited, providing a desired magnetic permeability for the pipe 14, so that a flaw present at a depth of 5% of the wall thickness of a pipe may be detected.

The detecting mechanism portion 7 includes an assembly of a base plate or mount 28 housed within the supporting tube 9; two or more attaching members 30 mounted on the mount 28 in parallel relation along the axis of the supporting tube 9, while detecting portions 29 incorporating magnetism-sensitive elements therein are attached to the tips of the attaching members 30, respectively; and guide rollers 31A, 31B attached to the mount 28 in the forward and rearward positions thereof are pivotally moved about two perpendicular supporting shafts. A window 32 is provided in such a portion of the supporting tube 9, which faces the detecting portion 29.

The undersurface of the mount 28 is supported through the medium of springs 33A, 33B on the inner surface of the supporting tube 9 and mov.able in the vertical direction, with a pin 34 being inserted into elongated hole 36 defined in a bracket 35 formed on the inner surface of the supporting tube in ;projecting relation therefrom. In addition, inclined surfaces 37A, 37B are provided on the undersurface of the mount 28. Disposed under the inclined surfaces 37A, 37B of the mount 28 are rollers 40A, 40B which are supported by link arm 39 axially movable by means of a cylinder 38. Accordingly, the rollers 40A, 40B roll on the inclined surfaces 37A 37B in response to the extending operation of the cylinder 38, thereby lifting the mount 28 so as to cause the detecting portion 29 to protrude from the window 32 to extend towards the inner surface of the steel pipe 14.

A guide mechanism portion 8 includes; a supporting frame 43 provided on the tip portion of the supporting tube and having a part-spherical or frusto-conical guide head 41 at its tip and guide rollers 42A, 42B adapted to turn about the supporting shafts in its middle portion; a bracket 45 projecting from the tip of the supporting tube 9 rearwardly of the supporting frame 43 and having a guide roller 44 which may be turned about its supporting shaft, at its tip; a bellcrank 48 having its intermediate portion pivoted to the bracket 45, and one end pivoted to a tip portion of a rod 46 in a.

cylinder, which is positioned within the supporting tube 9; a link arm 50 having one end pivoted to the bracket 47 and the other end pivoted to the bracket 49 at the tip of the supporing tube 9, respectively, the aforesaid link arm 50 being positioned in parallel with the other end portion of thc bellcrank 48.

The bracket 45 is formed with a guide 51 which projects forwardly of the guide roller 44.

In operation, the guide mechanism portion 8 is inserted into the steel pipe 14, and the cylinder is actuated to extend its rod 46, to thereby rotate the bell crank 48, thus moving the supporting frame 43 towards the inner surface of the steel pipe 14, as shown by a chain line in Fig. 4 with the aid of the link arm 50. This causes the guide rollers 42A, 42B to bear against the inner surface, of thq pipe 14, as well as the guide roller 44 to bear against the surface of the steel pipe 14 on the opposite side thereof, so that the tip portion of the supporting tube 9 may be supported and the window 32 in the supporting tube 9 is brought close to the inner surface of the steel pipe 14.

Under this condition, when the cylinder 38 is actuated in a manner described earlier, then the mount 28 may be moved towards the inner surface of the steel pipe 14, thereby bringing the respective detecting portions 29 to the inner surface of the pipe 14.

Meanwhile, the exciting head 19 outside the steel pipe 14 is lowered to the outer surface of the steel pipe 14 by means of the cylinder 17, while the follower rollers 22A, 22B are lowered by means of the cylinder 20 to contact the surface of the steel pipe 14, thereby bringing the both poles of the exciting magnets 24 close to the outer surface of the steel pipe 14.

In this manner, the detecting portion 29 and exciting magnets 24 may be brought closer relative to each other through the medium of the steel pipe 14. In this condition, when the steel pipe 14 is rotated and the exciting mechanism portion 1 and the detecting mechanism portion 7 travel in synchronism with each other, then the in spection may be conducted for the inner surface of the steel pipe 14.

As is apparent from the foregoing description of the magnetic inspection apparatus, the detecting mechanism portion incorporating the magnetism-sensitive element therein is separated from an exciting mechanism portion having exciting magnets; the detecting mechanism portion of a small mass is inserted along the inner surface of the; pipe, while the exciting mechanism portion of a large mass travels along the outer surface of the pipe in synchronism with the former along the length of the pipe which is being rotated.As a result, magnetic inspection is also applicable to pipes having relatively small diameters, and in addition, the exciting magnets and magnetismsensitive elements are positioned close to each other, with the pipe being interposed therebetween, so that satisfactory magnetic permeability results, thereby permitting the positive detection of a flaw at extremely small depth.

In addition, the detecting mechanism portion is secured to the tip portion of the supporting tube attached to a wheeled overhead carriage means which may travel along the rail, so that the detecting mechanism portion may be positively inserted into a pipe having a relatively small diameter Still furthermore, a guide mechanism portion adapted to guide the tip portion of the supporting rod relative to the inner surface of the pipe is provided in the tip portion of the supporting rod, so that the supporting tube may be inserted into the pipe in a stable manner. Yet furthermore, the exciting mechanism portion may travel along the rail, along with the wheeled carriage means, in opposed relation to the detecting mechanism portion, so that the exciting mechanism portion may positively travel in synchronism with the detecting mechanism portion.

WHAT WE CLAIM IS: 1. A magnetic flaw detector for the inner surface. of a pipe, comprising: a support tod mounted on a wheeled carriage which is movable along a rail, said support rod having a hollow space at least in the force end portion thereof to be inserted into said pipe and a window formed in said fore end portion for facing the inner wall surface of !said pipe; ; a detector assembly having a base plate accomodated within said hollow space at the fore end of said support rod and movable radially of said support rod, a plurality of detecting members mounted on said base plate in alignment in the longitudinal direction of said support rod, each of said de tecting members having a magneto sensitive element facing through said window toward the inner surface of said pipe, and a plurality of guide rollers mounted on said base plate which can be brought into rolling contact with the inner surface of said pipe when said detecting members are abutted against the inner surface of said pipe;

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (2)

**WARNING** start of CLMS field may overlap end of DESC **. adapted to turn about the supporting shafts in its middle portion; a bracket 45 projecting from the tip of the supporting tube 9 rearwardly of the supporting frame 43 and having a guide roller 44 which may be turned about its supporting shaft, at its tip; a bellcrank 48 having its intermediate portion pivoted to the bracket 45, and one end pivoted to a tip portion of a rod 46 in a. cylinder, which is positioned within the supporting tube 9; a link arm 50 having one end pivoted to the bracket 47 and the other end pivoted to the bracket 49 at the tip of the supporing tube 9, respectively, the aforesaid link arm 50 being positioned in parallel with the other end portion of thc bellcrank 48. The bracket 45 is formed with a guide 51 which projects forwardly of the guide roller 44. In operation, the guide mechanism portion 8 is inserted into the steel pipe 14, and the cylinder is actuated to extend its rod 46, to thereby rotate the bell crank 48, thus moving the supporting frame 43 towards the inner surface of the steel pipe 14, as shown by a chain line in Fig. 4 with the aid of the link arm 50. This causes the guide rollers 42A, 42B to bear against the inner surface, of thq pipe 14, as well as the guide roller 44 to bear against the surface of the steel pipe 14 on the opposite side thereof, so that the tip portion of the supporting tube 9 may be supported and the window 32 in the supporting tube 9 is brought close to the inner surface of the steel pipe 14. Under this condition, when the cylinder 38 is actuated in a manner described earlier, then the mount 28 may be moved towards the inner surface of the steel pipe 14, thereby bringing the respective detecting portions 29 to the inner surface of the pipe 14. Meanwhile, the exciting head 19 outside the steel pipe 14 is lowered to the outer surface of the steel pipe 14 by means of the cylinder 17, while the follower rollers 22A, 22B are lowered by means of the cylinder 20 to contact the surface of the steel pipe 14, thereby bringing the both poles of the exciting magnets 24 close to the outer surface of the steel pipe 14. In this manner, the detecting portion 29 and exciting magnets 24 may be brought closer relative to each other through the medium of the steel pipe 14. In this condition, when the steel pipe 14 is rotated and the exciting mechanism portion 1 and the detecting mechanism portion 7 travel in synchronism with each other, then the in spection may be conducted for the inner surface of the steel pipe 14. As is apparent from the foregoing description of the magnetic inspection apparatus, the detecting mechanism portion incorporating the magnetism-sensitive element therein is separated from an exciting mechanism portion having exciting magnets; the detecting mechanism portion of a small mass is inserted along the inner surface of the; pipe, while the exciting mechanism portion of a large mass travels along the outer surface of the pipe in synchronism with the former along the length of the pipe which is being rotated.As a result, magnetic inspection is also applicable to pipes having relatively small diameters, and in addition, the exciting magnets and magnetismsensitive elements are positioned close to each other, with the pipe being interposed therebetween, so that satisfactory magnetic permeability results, thereby permitting the positive detection of a flaw at extremely small depth. In addition, the detecting mechanism portion is secured to the tip portion of the supporting tube attached to a wheeled overhead carriage means which may travel along the rail, so that the detecting mechanism portion may be positively inserted into a pipe having a relatively small diameter Still furthermore, a guide mechanism portion adapted to guide the tip portion of the supporting rod relative to the inner surface of the pipe is provided in the tip portion of the supporting rod, so that the supporting tube may be inserted into the pipe in a stable manner. Yet furthermore, the exciting mechanism portion may travel along the rail, along with the wheeled carriage means, in opposed relation to the detecting mechanism portion, so that the exciting mechanism portion may positively travel in synchronism with the detecting mechanism portion. WHAT WE CLAIM IS:

1. A magnetic flaw detector for the inner surface. of a pipe, comprising: a support tod mounted on a wheeled carriage which is movable along a rail, said support rod having a hollow space at least in the force end portion thereof to be inserted into said pipe and a window formed in said fore end portion for facing the inner wall surface of !said pipe;; a detector assembly having a base plate accomodated within said hollow space at the fore end of said support rod and movable radially of said support rod, a plurality of detecting members mounted on said base plate in alignment in the longitudinal direction of said support rod, each of said de tecting members having a magneto sensitive element facing through said window toward the inner surface of said pipe, and a plurality of guide rollers mounted on said base plate which can be brought into rolling contact with the inner surface of said pipe when said detecting members are abutted against the inner surface of said pipe;

a guide mechanism having a support frame attached to the fore end of said support rod and swingable in a direction opposite to the facing direction of said magnetosensitive elements, and a guide roller adapted to be brought into rolling contact with the inner surface of said pipe to support said support rod when said support frame is swung; a magnetizing assembly having a magnetizing head mounted on a wheeled carriage movable with the first-mentioned wheeled carriage along said rail and movable toward and away from the outer surface of said pipe, DC exciting magnets mounted on said magnetizing head, said magnets opposing said magneto-sensitive elements across the wall of said pipe, and follower rollers adapted to be brought into rolling contact with the outer surface of said pipe to support said exciting magnets in the vicinity of the outer surface of said pipe; and means for rotating said pipe about the axis thereof.

2. A magnetic flaw detector substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.