Abstract:
Inspection apparatus adapted to be propelled through a pipeline. Means are provided to establish a circumferentially directed flux field in wall of pipe, and longitudinally extending flexible fins or flaps of elastomeric material curve outwardly from apparatus to resiliently hold flux leakage detection means against wall of pipe. Means responsive to axial movement of apparatus imparts helical movement of apparatus. Apparatus is readily adapted to inspect pipelines of different sizes.

Description:
This application is a continuation of application Ser. No. 299,009 filed Oct. 19, 1972, entitled Rotating Pipeline Inspection Apparatus by R. D. Barton, now abandoned, which application is a continuation of application Ser. No. 56,491, filed July 20, 1970 by R. D. Barton, entitled Rotating Pipeline Inspection Apparatus, now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     Buried pipelines that transport fluid products such as natural gas, crude oil, and other petroleum products are subject to damage due to physical forces applied to them, and due to chemical and electrolytic action. To assure that a pipeline is safe for continued operation it is periodically inspected for flaws by nondestructive testing apparatus which is carried through the interior of the pipeline by means of a pig. The pig is propelled through the pipeline by the fluid being transported therethrough. 
     One of the more serious flaws that potentially may make the pipeline unsafe for continued operation is a longitudinally extending anomaly in the wall of the pipe. Apparatus for detecting longitudinally extending flaws in a buried pipeline are disclosed in U.S. Pat. Nos. 3,238,448 by Wood et al., and 3,483,466 by Crouch et al. 
     Although the devices disclosed in those patents are useful, the device shown in U.S. Pat. No. 3,238,448 requires that a power source carried on the apparatus rotate a portion of the apparatus that carried the flaw detection means. Also, slip rings are required to couple detected flaw signals and electrical power to and from other portions of the apparatus. These requirements add complexity to the design and maintenance of the apparatus. Satisfactory operation of slip rings in a pipeline environment is particularly troublesome. In order to minimize the complexities mentioned above, the device of U.S. Pat. No. 3,483,466 was constructed in such a manner that longitudinally extending anomalies could be detected without the need for mechanically rotating a portion of the apparatus. This simplified the device and eliminated the need for the additional power source and slip rings associated with the rotating portion. However, because optimum sensitivity of detection of longitudinally extending anomalies is achieved when the flux leakage detector passes transversely across the longitudinally extending anomaly, the device of U.S. Pat. No. 3,483,466 does not provide optimum sensitivity of detection. 
     Additionally, in the prior devices discussed above, the search shoes which house the flaw detecting elements, such as search coils, are supported by mechanisms which involve moving and sliding parts and springs. The mechanisms are subject to corrosion and considerable wear, damage, and even loss when they encounter mashes, weld &#34;icicles&#34;, valves, and traps, for example. 
     BRIEF SUMMARY OF INVENTION 
     The improved pipeline inspection apparatus of the invention includes means for establishing a circumferentially directed magnetic flux field in the wall of the pipe and flaw detecting means adapting to scan or wipe the interior surface of the pipe. The flaw detecting means are carried on longitudinally extending appendages of a flexible material which resiliently maintains the flaw detecting means in intimate contact with the pipe wall. Means for supporting the apparatus within the pipeline imparts a rotary motion to the entire inspection apparatus as it is propelled through the pipeline, thus causing the flaw detection means to follow a helical path through the pipeline and to pass transversely across any longitudinally extending anomaly in the pipe wall. 
     The inspection apparatus is constructed in such a way that it may be readily adapted for use in different pipelines respectively made of different diameter pipes. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIGS. 1 and 2 are orthogonal longitudinal views, partially in section, of the inspection apparatus of this invention; 
     FIG. 3 is a transverse sectional view taken at sections 3--3 of FIG. 2; 
     FIGS. 4 and 5 are sectional views similar to FIG. 3 showing the construction of the basic inspection apparatus adapted for use in successively larger pipes. FIG. 5 also illustrates an alternative construction of the magnetizing and flaw detection portion of the inspection apparatus. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to FIGS. 1 and 2, the inspection apparatus is illustrated as it would appear within a section of pipeline 10. The apparatus is comprised of three principal sections; a propelling section 11, a rotating section 12, and an inspection section 13. Propelling section 11 is comprised of one or more elastomeric cup or packer 16 which engages the entire circumference of the inside wall of the pipe and acts as a sliding seal or packer which is forced toward the left by the pressure of the fluid which is being transported through the pipeline in the direction from right to left. 
     A universal joint 17 and a swivel joint 18 connect cup 16 to the rotating section 12. Rotating section 12 includes an elastomeric wheel support member 20 which may be cup-shaped as illustrated. Three or more supporting wheels 22 are rotatably mounted on respective support brackets 23 which are secured in spaced relationship about the periphery of wheel support member 20. Support brackets 23 are resilient to permit wheels 22 to ride over dents and protrusions in the pipeline, yet they are stiff enough so that in cooperation with wheels 22 they tend to have a centering action to help maintain the apparatus substantially centered within the pipeline 10. 
     As best seen in FIG. 1, each wheel 22 is mounted within a cut-out portion 25 in its respective support bracket 23. Furthermore, all of the wheels 22 are canted or inclined in the same direction relative to the longitudinal axis of pipe 10 so that the section 12 is caused to rotate as it is drawn through pipe 10 by the propelling section 11. Because of swivel joint 18, rotating section 12 rotates independently of propelling section 11 whose forward motion is substantially without rotation. 
     Another universal joint 27 and a connector plate 28 connect rotating section 12 to inspection section 13 so that rotating section 12 imparts its rotary motion to inspection section 13. Universal joints 17 and 27 allow the various sections of the apparatus to bend with respect to each other to permit the apparatus to negotiate bends in the pipeline without becoming lodged therein. 
     FIGS. 1-3 illustrate the inspection apparatus as it is adapted to inspect the smallest diameter pipeline contemplated to be inspected by one basic piece of apparatus of this invention. The inspection section is comprised of a longitudinally extending magnetic core member 30 having a solenoid 31 wound thereabout to form an electromagnet which provides a unidirectional magnetic field H directed vertically, as viewed in FIG. 3. Longitudinally extending flange members 33 secured, as by welding, at the four corners of core member 30 form a bobbin-like construction upon which solenoid 31 is wound. 
     Positioned on the top and bottom surfaces of core member 30, and between a respective pair of flange members 33, are respective wire brush pole pieces 35 and 36 which are formed of magnetic flux conductive bristles. The wire brushes are mounted by any conventional means, not illustrated, to respective sole plates 38 and 39 of magnetic material. Thus, good magnetic flux conductive paths are established from core 30 to wire brushes 35 and 36. Wire brush pole pieces 35 and 36 extend longitudinally substantially the entire length of inspection section 13 and extend radially to make intimate contact with the inner surface of pipe 10 at diametrically opposed regions. The magnetic path just described establishes a circumferentially direct magnetic flux field in each half of the wall of pipe 10. Longitudinally extending cracks and flaws in the wall of pipeline 10 will interrupt the circumferentially directed flux field and will create leakage flux which may be detected by suitable means. 
     In FIG. 3 the right edge of magnetic sole plate 38 and the left edge of sole plate 39 are held in contact with core 30 by means of longitudinally extending retainer bars 42 and 43 which are held in place by bolts threaded into core member 30. 
     The opposite edges of sole plates 38 and 39 are held in contact with core 30 by the edge portions of respective longitudinally extending appendages such as fins or flaps 46 and 47, described below, and by longitudinally extending retainer bars 51 and 52 which are held in place by bolts threaded into core member 30. 
     Fins 46 and 47 are each made of a unitary sheet of elastomeric material such as rubber or a plastic such as polyurethane which is resilient and yet durable enough to withstand considerable wear and physical shock force. The characteristics of the elastomeric material, and the width and thickness of the sheets are chosen so that when bent as illustrated in FIG. 3, they hold the respective longitudinally extending transducer housing members 55 and 56 in firm, but yieldable, contact with the inner surface of pipe 10. As best seen in FIGS. 1 and 2, fins 46 and 47 may be perforated along their lengths to facilitate their bending. Fins 46 and 47 are bent in the appropriate direction so that transducer housings 55 and 56 are at the trailing or free edges of the fins as inspection section 13 rotates within pipe 10. As illustrated in FIG. 3, the inspection apparatus would rotate in a clockwise direction relative to pipe 10. 
     Disposed within and along the lengths of transducer housing members 55 and 56 are respective pluralities of flaw detection means such as magnetic flux leakage sensing coils 57 whose construction and operation are understood by those skilled in the art of magnetic nondestructive testing. Transducer housing members 55 and 56 are made of a wear resistant, nonmagnetic material such as stainless steel. The size, shape, and arrangement of flux leakage sensing coils in transducer housing members 55 and 56 are proportioned so that substantially complete flaw inspection may be achieved along the lengths of the transducer housing members. Additionally, the inclination of wheels 22, and thus the pitch of the helical path followed by inspection section 13, is proportioned relative to the lengths of transducer housing members 55 and 56 so that complete inspection coverage of the pipe wall is achieved as the inspection apparatus passes helically through the pipeline. The helical motion causes the flaw detection coils to pass transversely across a longitudinally extending anomaly in the wall of pipe 10. 
     The leading edges of transducer housing members 55 and 56 are bowed inwardly to permit the housing members to ride up and over protrusions on the inside surface of the pipe. It may be desirable to form the transducer housing members 55 and 56 in a plurality of adjacent segmented parts to that adjacent parts may bend and/or twist relative to each other. This type of construction will minimize any tendency of an entire housing member to lift off of the surface of the pipe when a protrusion is encountered. The yieldable nature of fin members 46 and 47 throughout their entire lengths will aid in avoiding the complete lift off of the transducer housing members from the pipe wall surface when using segmented housing members. 
     Inspection section 13 is connected at its right end by universal joint 59 to additional apparatus such as flaw signal circuitry and recorders for processing the flaw signals and battery packs for energizing the inspection equipment. The additional equipment is contained in a housing 60, FIGS. 1 and 2, which rotates along with the inspection section 13 as the apparatus moves through the pipeline. Housing 60 is provided with canted or inclined supporting wheels similar to the wheels 22 of FIGS. 1 and 2. It may be seen that slip rings are not required to couple the electromagnet, if used, and the flaw detection coils in inspection section 13 to the batteries and electronic and recording equipment carried in housing 60 since both parts of the apparatus rotate together. 
     As previously mentioned, the inspection apparatus of this invention may be readily adapted to inspect different pipelines made of different diameter pipes. FIG. 3, for example, illustrates the apparatus adapted to inspect a pipeline having one diameter, and FIGS. 4 and 5 illustrate the apparatus adapted to inspect pipelines of successively larger diameters. 
     In FIG. 4, core member 30, solenoid 31, wire brush pole pieces 35 and 36, the appendages such as fin members 46 and 47, and transducer housing members 55 and 56 are the same as illustrated in FIG. 3. In order for the pole pieces 35 and 36 to make good flux-conductive contact with the wall of the larger diameter pipe 10&#39;, longitudinally extending magnetically conductive spacer bars 70 and 71 are placed between core member 30 and the sole plates 38 and 39 of the wire brush pole pieces 35 and 36. Additional longitudinally extending spacer bars 73 and 74 are placed under respective retainer bars 42 and 43 to secure the right and left edges, respectively, of sole plates 38 and 39. 
     The locations of fin members 46 and 47 also are moved radially outwardly by means of spacer bars 75 and 76. Retainer bars 78 and 79 receive bolts to secure fins 46 and 47 to spacer bars 75 and 76, and to secure those spacer bars to core member 30. It may be seen by comparing FIGS. 3 and 4 that fin member 46, for example, has been moved upwardly from core member 30 and outwardly from pole piece 35 so that transducer housing member 55 still makes firm contact with the wall of the larger diameter pipe 10&#39;. 
     For inspection apparatus constructed as illustrated in FIG. 4, appropriate changes also must be made to the rotating section 12, FIGS. 1 and 2, to assure that wheels 22 maintain engagement with the inside surface of the larger diameter pipe 10&#39;. For example, larger diameter wheels may be used, differently shaped supporting brackets 23 may be used, or a different size cup member 20 may be used. Larger diameter cup 16 also would be used in propelling section 11. 
     The functioning of the apparatus illustrated in FIG. 4 to perform an inspection operation is substantially the same as that of FIG. 3, previously described. 
     FIG. 5 illustrates a slightly modified embodiment of the invention which is adapted to inspect a pipeline 10&#34; having a diameter larger than the one illustrated in FIG. 4. In this embodiment, core member 30&#39; is a permanent magnet rather than the core of an electromagnet. Furthermore, wire brush pole pieces 35 and 36 are spaced from permanent magnet core 30&#39; by respectively unitary, longitudinally extending spacer members 80 and 81 which are made of a magnetically conductive material. 
     The elastomeric appendages for supporting transducer housing members 55 and 56 also are somewhat different in FIG. 5. The fin or flap members 46&#39; and 47&#39; are much wider so that they extend beyond the transducer housing members and bend inwardly and are secured to the sides of magnetic core 30&#39;. This type of construction of the flaps 46&#39; and 47&#39; assures that transducer housing members 55 and 56 are maintained in firm but resilient contact with the wall of pipe 10&#34;. 
     The flaps 46&#39; and 47&#39; are secured to longitudinally extending flanges 85 and 86 of spacer member 80 and 81 by means of retainer bars 90 and 91 and bolts, as illustrated. In order that the same flaps 46&#39;, 47&#39; and transducer housing members 55 and 56 may be used irrespective of the pipeline diameter, a number of threaded holes may be bored at different vertical positions on the sides of core 30&#39; so that the bolts 94 and 95 may secure the ends of flaps 46&#39; and 47&#39; at different locations on the sides of core 30&#39;. This will permit the flaps to take on different curvatures so that transducer housing members 55 and 56 will contact the walls of different diameter pipes. Alternatively, suitable spacer bars or other adapter means may be employed to change the curvatures of flap members 46&#39; and 47&#39;. 
     It is to be understood that any or all of the modifications illustrated in FIG. 3 may be incorporated in the apparatus illustrated in FIGS. 1-4, and vice versa. 
     The embodiments of the invention illustrated in FIGS. 1-5 employ but two pole pieces to couple magnetic flux into the pipeline wall. In the construction of apparatus to inspect a range of very large diameter pipelines, it may be desirable that the basic apparatus be provided with four or more magnetic poles distributed circumferentially around the core, with adjacent poles being of opposite magnetic polarities. With this type of arrangement the lengths of the magnetic circuits may be reduced as compared to the lengths of the circuits if only two pole pieces were used. This alternative arrangement of pole pieces will facilitate the achievement of the desired state of magnetization in the pipe wall. 
     The inspection apparatus described above provides a number of advantages, both in construction and in use. The fins or flaps 46, 47, and 46&#39;, 47&#39; are simple and relatively inexpensive to construct from unitary sheets of elastomeric material. Furthermore, the elastomeric material can withstand considerable shock and abrasion without serious damage and is not subject to corrosion as are metal structures. The flexible nature of the fins permits the transducer housing members to pass over irregularities within the pipeline without damage. 
     The adaptability of the apparatus to inspect different size pipelines is extremely attractive since one work crew with one basic piece of apparatus may inspect different lines. Other known inspection apparatus of this general type is not readily adaptable and separate apparatus of different size would have to be provided.