Abstract:
In order to facilitate introduction of an inspection pig through an introductory conduit having a smaller diameter and into a pipeline of large diameter and transporting a fluid, in particular gas or oil, the invention proposes a device for inspection of pipes having sensors disposed about an outer periphery thereof having radially expandable inspection units ( 6, 7 ), wherein, in particular, a front and a rear inspection unit ( 6, 7 ) having sensors ( 15; 15 ′) displaced with respect to each other in a peripheral sense can be moved axially towards each other.

Description:
This application claims Paris Convention Priority of German Patent application number 197 46 511.0 filed Oct. 22 1997, the complete disclosure of which is hereby incorporated by reference. 
     BACKGROUND OF THE INVENTION 
     The invention concerns a device for the inspection of pipes having sensors disposed about an outer periphery. 
     In order to inspect pipelines, in particular those under water or pipelines traveling below the earth, conventional so-called inspection pigs are utilized having inspection devices with inspection elements or sensors disposed about an outer girth by means of which the condition of the walls of the pipes can be inspected. The sensors can be effected in differing manners; piezoelectric sensors, Electro-acoustic sensors electromagnetic sensors such as Hall sensors, stray field sensors and eddy current sensors are all known in the art. Differing wall conditions, e.g. due to corrosion etc. provide differing signals to be further processed in an electronics unit. 
     Particularly for the case of conduits traveling under water, it is extremely expensive to provide an input location and extremely difficult to introduce an inspection pig into such a conduit. For example, difficult and expensive input lock mechanisms having expensive valves must be provided for. For introduction, a diver must submerge to substantial depths to introduce such a pig into a pipeline so that the pig can travel through and inspect same. On the other hand, this type of pipeline can have a relatively large diameter, on the order of the magnitude of e.g. 40 inches (corresponding to 1 m), and therefore cannot be passed from the ground to the upper surface of the water, since its weight is prohibitive. 
     It is the underlying purpose of the invention to create a device for the inspection of pipelines which avoids the above mentioned disadvantages and facilitates, in particular, a simple introduction into the pipeline. 
     SUMMARY OF THE INVENTION 
     This purpose is solved in accordance with the invention using a device for the inspection of pipes having sensors disposed about an outer girth thereof which is characterized by radially expandable inspection units. 
     The solution in accordance with the invention allows a pig to be passed through an introductory pipe having a smaller diameter, e.g. a diameter of 16 or 28 inches (corresponding to approximately 40 and 70 cm, respectively) and introduced to the main conduit having the above mentioned diameter, whereas the pig has a smaller diameter than the introductory conduit and can expand to the larger diameter of the main conduit passing the medium while nevertheless permitting a reliable inspection of the pipe conduit by means of the sensors disposed around its outer girth (in the respective expanded position). 
     A most preferred embodiment provides for a front and a back inspection unit having sensors disposed about their girths in a displaced fashion and which can be axially moveable relative to each other. The expansion of sensors located on arms of such a pig causes an increase in their angular separation within an inspection unit. On the other hand, one must inspect the pipe conduit about its entire periphery. This is fundamentally possible in that sensors, when appropriately axially displaced, are disposed in such a fashion as to cover the entire periphery of the pipe. Since however the signals from the individual sensors have to be correlated and in particular since, when passing though curves in the pipe conduit, the relative angular positions of the sensors, possibly provided on two differing inspection units, does not remain defined, it is therefore advantageous to completely cover the entire girth of the pipe conduit with sensors at one axial position. This is accomplished in the above mentioned preferred embodiment in that the inspection units are capable of displacement towards each other in such a fashion that the mutually angular-displaced sensors of the two inspection units occupy the same axial position. This guarantees that the entire girth of the pipe is covered by sensors and appropriately inspected at a common axial position when the device for inspection of pipe conduits is expanded. 
     In order to avoid difficult and expensive active displacement mechanisms for the inspection units which would require their own drive and power supply (the providing of sufficient electrical power to a pig is difficult since this must be supplied in the form of batteries or rechargeable batteries over substantial lengths and over long periods of time), the invention provides, in a most preferred improvement, that the rear inspection unit be moveable towards the front inspection unit under the action of the flow pressure of the fluid flowing in the pipeline, wherein, in particular, the back inspection unit can be moved towards the front inspection unit by means of a pull unit. The pull unit thereby has a collar which seats under the action of fluid pressure on the inner wall of the pipe conduit and is also pushed in a forward direction under the pressure of the flowing fluid such that it moves together with the rear inspection unit in the direction of motion of the inspection pig and in the direction of motion of the device for inspection of the pipeline conduits in a manner more rapid than the front inspection unit (relative to an external stationary point) to thereby more towards the front inspection unit. Since the extensive additional elements of an inspection pig such as electronic units, power supply units etc. are connected to the rear inspection unit and the pull unit, the front inspection unit moves relative to this residual portion of the inspection pig. 
     Further preferred embodiments of the invention provide that the inspection units are fixed relative to each other in certain angular positions, wherein, in particular, the sensors of the inspection units are disposed in angular displaced positions in such a manner that a sensor of the front inspection unit has an angular position midway between two neighboring sensors of the rear inspection unit with sensors of an inspection unit being aligned with each other. 
     A preferred embodiment provides that the inspection units can radially expand under the action of a spring force. In this manner, one guarantees that the sensors of the inspection units are pushed closely against the inner wall of the pipe conduit, wherein a predetermined defined separation can be effected by guide rollers mounted to a sensor support along with the sensors to guarantee that the sensors are located at a small defined radial separation from the inner wall of the pipe conduit while not coming in contact therewith, to prevent wear. A further improved embodiment can provide that the sensors be disposed on parallelogram rods. In this manner a stable configuration of the expandable inspection unit system is created, wherein one guarantees that, independent of the expansion position, the sensors always remain constantly parallel to the axis. 
     An additional preferred configuration is characterized by a releasable blocking mechanism to axially fix one of the inspection units, in particular the front inspection unit, to a guide element (guide rod), wherein, in particular, a release mechanism for releasing the blocking mechanism is provided when the corresponding inspection unit has reached its expansion position. This guarantees that, in the introductory position of the inspection unit, the front inspection unit is blocked on a guide rod at an axial separation with respect to the rear inspection unit and can not move relative thereto to prevent damage. One simultaneously guarantees that, when a predetermined radially expansion position is reached, the blocking mechanism is released so that the above mentioned relative motion between the two inspection units can transpire and the inspection units can move towards each other in an axial direction so that their sensors can occupy the desired common axial position (with angular displacements). 
     Further advantages and features of the invention can be extracted from the claims and the following description in which embodiments of the device in accordance with the invention are described more closely with reference to the drawing. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 shows a complete inspection pig located within a pipe conduit having a large diameter during inspection operation having expandable inspection units in accordance with the invention which can move into each other; 
     FIG. 2 shows the inspection pig of FIG. 1 in a compact introductory state within an introductory pipe having a narrower diameter; 
     FIG. 3 shows the inspection device in accordance with the invention in the expanded state before the two inspection units have moved axially into each other; 
     FIG. 4 shows a side view of the front inspection unit; 
     FIG. 5 shows a cut through the front inspection unit corresponding to V—V of FIG. 4; 
     FIG. 6 shows a side view of the rear inspection unit; 
     FIG. 7 shows a cut through the rear inspection unit corresponding to VII—VII of FIG. 6; 
     FIG. 8 shows a spring unit for radial erection of the inspection unit; 
     FIG. 9 shows a blocking and releasing mechanism to release one of the inspection units for axial displacement; 
     FIG. 10 shows a part of the blocking and releasing mechanism in the blocking position; 
     FIG. 11 shows the part of the blocking and releasing mechanism of FIG. 10 in the releasing position; 
     FIG. 12 shows the progression of the expansion of the device in accordance with the invention during transition from a narrow introductory pipe into a wider pipeline being inspected. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 shows an inspection pig for the inspection of pipe conduits  10  having an inspection device in accordance with the invention. In the embodiment shown, the pig  1  comprises a pull unit  2 , a guide unit  3 , the inspection unit  4  in accordance with the invention having, in the representation of FIG. 1, a front inspection unit  6  and a rear inspection unit  7  which can move into each other. An inspection pig  1  of this type normally has an additional electronic unit  8  and a power supply  9  having batteries or storage batteries. The individual units are guided in the pipe conduit  10  by means of wheels  11  disposed on arms  11   a  pushed in an outward direction by springs. Such an inspection pig moves within a pipeline in response to the flow pressure of the medium transported in the pipeline, and in the embodiment shown, by means of collars  12 ,  13 . The collar  12  is designed for a pipe conduit having a narrow diameter, in the example shown, in the range between 26 and 28 inches, whereas the collars  13  are inactive in such a narrow pipeline. However, when the inspection pig  1  in accordance with the invention passes into a wider conduit, e.g. one having a diameter on the order of 40-42 inches, these can expanded to take over the drive function for the inspection pig  1 . Inspection units  6  have sensors  15 ,  15 ′ about their outer periphery which, in the embodiment shown, can be magnetic sensors, e.g. for inspection of the pipeline by means of stray magnetic field techniques, or other types of sensors. 
     The modules  2 ,  3 ,  4  seat on guide rods  16  through  19  which are connected to each other by means of linkages  21  through  23 . The electronic unit  8  is connected to the inspection unit  4  via an additional linkage  24  and the power supply unit  9  is connected to the electronic unit  8  via a linkage  26 . 
     In this manner, the inspection pig  1  can also be guided through pipe conduits having narrow radii of curvature. An inspection pig must not be precisely equipped with the inspection device in accordance with the invention as disclosed in this embodiment. For example, the electronic and power supply modules can be integrated within each other or be combined with other units. 
     Whereas FIG. 1 shows the inspection pig having an inspection device in accordance with the invention in an expanded operating state of the inspection device  4  in which the two inspection units  6 ,  7  are expanded and axially displaced within each other, FIG. 2 shows the same inspection pig  1  in an introductory state with which the two inspection units  6 ,  7  are axially apart, disposed at a separation with respect to each other, and radially compressed, as is also the collar  13  of the pull unit  2 . 
     FIG. 3 shows the inspection device  4  in accordance with the invention in an expanded state with which the two inspection units  6 ,  7  are expanded such that their radii are adjusted to the pipe conduit of larger diameter which is to be inspected. The two inspection units  6 ,  7  are however not yet axially displaced within each other, rather still have an axial separation corresponding to the compressed introductory state through a narrow pipe conduit as shown in FIG.  2 . They are thereby disposed on both sides of the linkage  23  on rods  18 ,  19 , wherein the inspection unit  7  is axially fixed to the rod  19  via bolts  27  and the inspection unit  6  is guided in an axially displaceable fashion along the rod  18  past the linkage  23  and up to the rod  19 . It is, however, guided or fixed in the angular direction relative to the rod  18 ,  19  and thereby aligned with respect to inspection unit  7 . Towards this end, the rods  18 ,  19  (see, in particular, FIGS. 4 and 5) have axis-parallel guiding grooves  28  into which guide rollers  29  of the main body  31  of the inspection unit  6  engage to fix same at certain angular positions along the rods  18 ,  19 . Bolts  27  likewise engage, as can be seen in FIG. 7, into guide grooves  28  of the rod  19  so that the inspection unit  7  is fixed both axially and in an angular manner. A comparison between FIGS. 5 and 7 shows that the sensors  15  of the front inspection unit  6  and sensors  15 ′ of the rear inspection unit  7  are radially displaced with respect to each other in such a manner that the sensors  15  of the inspection unit  6  can engage into the intermediate angular spaces between two peripherally adjacent sensors  15 ′ of the inspection unit  7  when e.g. the bolts  27  and the rollers  29  (FIGS. 5 and 7) engage in precisely the same guide groove (designated in the figures with the reference symbol  28 ). 
     Each inspection unit  6 ,  7  has a central main body  31 ,  31 ′ with which it can be guided and fixed in the above mentioned fashion along and to rods  18 ,  19 . 
     The sensors  15  and  15 ′ respectively are supported on the main bodies  31 ,  31 ′ via parallelogram rods  32 ,  32 ′. The parallelograms  32 ,  32 ′ consist essentially of the main body  31 ,  31 ′ front and rear connecting arms  33 ,  34  and  33 ′, 34 ′ respectively and the forward sensor support  36  and backward sensor support  36 ′ which are thereby guided parallel to the main body  31 ,  31 ′. 
     Each sensor support  36 ,  36 ′ supports pole shoes  14 ,  14   a ,  14 ′,  14   a ′ respectively at its outer side which are aligned one behind the other and parallel to the axis. These can e.g. be in the form of brushes which rub against the inner wall of the pipe conduit to thereby introduce a magnetic field into the pipe which can be detected by the sensors  15  and  15 ′ respectively. The sensors themselves are borne in an elastic and resilient fashion on elastic supports  15   a ,  15   a ′ (for example made from polyurethane) having a longitudinal section which is parallelogram in shape. A ceramic member  15   b  and  15   b ′ respectively (FIGS. 4 and 6) is provided on the outer side to protect against wear. 
     The members  31 ,  33 ,  34 ,  36  of the parallelogram rods  32  and the members  31 ′,  33 ′,  34 ′,  36 ′ of the parallelogram rods  32 ′ are linked to each other by means of linkages  37  through  39 ,  41  and  37 ′ through  39 ′,  41 ′ such that the sensor supports  36 ,  36 ′ are guided parallel to the corresponding main body  31 ,  31 ′ independent of their radial position. 
     The sensor supports  36 ,  36 ′ having the sensors  15  and  15 ′ respectively are pressed via spring units  42 ,  42 ′ into their radial extended position. The spring units  42 ,  42 ′ comprise a disk spring  51  or helical springs. 
     The spring unit  42  is shown in an enlarged manner in FIG.  8 . An end  53  of a piston rod  43 ,  43 ′ is linked to the respective spring unit  42 ,  42 ′ at a location  52  between the linkages  39  and  41  or  39 ′ and  41 ′ respectively of the connecting arms  34  and  34 ′ respectively. The spring  51  is tensioned between two abutments  54 ,  56 . The abutment  54  is disposed on an end of the piston rod  43  opposite end  53  thereof. The abutment  56  is formed by a plate through which the piston rod  43  penetrates and which is fixed to a roller support  57  for the roller  11  connected to the sensor support  36 . The spring unit  42 ′ is correspondingly configured. The spring action of the spring unit  42 ,  42 ′ attempts to shorten the free region of the piston rod  43  between the end  53  and the abutment  56  and thereby to radially erect or to expand the parallelogram rods  32  (or  32 ′) so that the inspection unit can radially expand during transition from a pipe of low diameter into a pipe of larger diameter. 
     The inspection unit  6  has a blocking and releasing mechanism  44  for axially blocking and releasing the motion along the rods  18 ,  19  (FIG.  9 ). The blocking and releasing mechanism has an arm  47  hinged to a connecting arm  33  and an arm  47  connected to the main body  31  which are linked for relative motion towards another by a slot in arm  46  and a pin  48   a  in arm  47  engaging therein. The arm  47  is linked in a pivotable fashion at  61 . In the compressed state of the inspection unit, the arm  47 , at an end facing away from the arm  46 , passes through the body  31  and engages into an opening  63  in the rod  18  to thereby block the inspection unit  6  with respect to displacement along the rods  18 ,  19  (FIG.  10 ). A leaf spring  66  bears on a outwardly directed shoulder  64  and thereby presses the arm  47  into its radially inward position. If the inspection unit  6 , when passing from a pipe of small diameter into a pipe of larger diameter, then expands under the action of spring unit  42  so that the parallelogram rods  32  radially erect, the arm  46  is carried by the arm  33  but, due to the slot  48 , can nevertheless move relative to the arm  47  which, in turn, is initially held stationary by means of the leaf spring  66  and blocks, by means of its shoulder  62  engaging into the opening  63  of the rod  18 , the inspection unit  6  on the rod  18  even during its radial expansion. When a predetermined radial diameter is reached, the arm  46  carries the arm  47 , in opposition to the action of the leaf spring  66 , along with it and pivots same so that its shoulder  62  leaves engagement with the opening  63  of the rod  18  (FIGS. 9,  11 ) to thereby release axial motion of the inspection unit  6  such that it can, via the pig motion, move along the rod  18 ,  19  towards the inspection unit  7 . 
     As soon as the parallelogram rods  32  have radially erected, a blockage is thereby released which, in the compressed introductory state of the inspection unit  6  blocks same axially on the guide rods  18 . After release, the inspection unit  6  can travel via its rollers  29  along the guide rods  18  and past the linkage  23  along the guide rods  19  towards the inspection unit  7 . 
     The expansion of the inspection unit  4  in accordance with the invention and the axial moving together of the inspection units  6  and  7  transpires in the following manner (FIG.  12 ). 
     The inspection pig, having the inspection device in accordance with the invention, is initially guided through a pipe conduit  10 ′ having a reduced diameter of e.g. approximately 28 inches while disposed in its radially compressed position shown in FIG.  2 . It is pushed through the pipe conduit  10 ′ by means of its collar  12  since same enters tightly into the pipe conduit  10 ′ so that the upstream pressing fluid can press the inspection pig  1 , substantially via the collar  12 , through the pipe conduit  10 ′. 
     As soon as the collar  12  and the front collar  13  have gained entrance into the transitional region  10 ″ between the narrower pipe conduit  10 ′ and the additional pipe  10 , the most forward erecting collar  13  can initially expand since it presses firmly against the wall of the transitional region  10 ″ and of the pipe  10  to thereby drive the inspection pig  1  (phase  2 ). In phase  3 , the rear erecting collar  13  also expands. The pig is pulled further out of the narrow pipe  10 ′ past the transitional region  10 ″ into the additional pipe  10  (phases  4 ,  5 ). As soon as the front inspection unit  6  passes through the transitional region  10 ″ it expands thereby under the action of its spring units  42 . As soon as the inspection unit  6  has assumed its fully expanded position, the blocking and releasing mechanism  44  releases the inspection unit  6  in a manner described with respect to FIG. 9 so that the inspection unit  6  can move along the rods  18 ,  19  and past linkage  23  (phases  6 ,  7 ). The relative motion of the inspection units  6 ,  7  towards each other is due to the fact that, subsequent to release, the inspection unit  6  is held on the inner wall of the pipe conduit  10  by friction, whereas the inspection unit  7  which is fixed to the rod  19  is pulled further in the direction of motion of the inspection pig (arrow A) by means of the collar  13  and via the rods  16 , 17 ,  18  to thereby move towards the inspection unit  6 . The entire inspection pig, with the exception of inspection unit  6 , and in particular along with inspection unit  7 , thereby carries out a larger relative motion relative to a stationary observer in the direction of arrow A than the inspection unit  6  (which moves relative to the overall remaining inspection pig and in particular with respect to and towards the inspection unit  7 ). In the embodiment shown, the guide unit  3  is connected to the inspection unit  6  to thereby carry out together therewith the relative motion with respect to the remaining pig  1 , as can be likewise extracted from the phases  6  through  8 . When the inspection unit  7  completely enters into the additional pipe conduit  10 , the inspection units  6 ,  7  have moved axially within another in such a fashion that the front sensors  15  and the rear sensors  15 ′ of the two inspection unit  6 ,  7  both occupy a common axial position while being, however, displaced with respect to angle in the manner described above. In this manner, a sensor  15  engages into each free angular space between two sensors  15 ′ and vice versa. 
     The pig is then located (phase  8 ) in its inspection position and can carry out an inspection of the walls of the pipe of the additional conduit  10  to locate defects.