Abstract:
A device ( 1 ) for passing through pipes in the form of a pig ( 1 ) moving through the pipe and guided on the inner wall thereof has at least one pig body ( 16 ) and support elements ( 8   a ) on the outer periphery thereof for guidance within the pipe as well as drive elements ( 10   a   , 10   b ) in the form of collars for transport in the pipe. The device is distinguished by improved entrance into the pipe conduit in that at least one of the collars ( 10   a   , 10   b ) can be radially expanded.

Description:
This application claims Paris Convention Priority of German patent application number 197 46 510.2 filed Oct. 22, 1997 the complete disclosure of which is hereby incorporated by reference. 
     BACKGROUND OF THE INVENTION 
     The invention concerns a device for passing through pipes in the form of a pig moved through the pipe and guided along the inner walls thereof with at least one pig body and with support elements disposed on its outer periphery for guiding in the pipe as well as drive elements in the form of collars for advancement within the pipe. 
     Pigs are used in pipelines, in particular for oil and gas transport, to locate defects in the pipe, for cleaning the pipe, and the like. They are thereby normally advanced through the pipe by the medium being transported e.g. oil. Intelligent pigs carry out the most differing of measurements, such as pipe wall measurements to e.g. detect local corrosion, wall thickness weaknesses caused by mechanical damage, pitting etc. Depending on the job at hand, differing types of sensor units are utilized, such as leakage sensors, Hall effect sensors, electro-optical sensors, ultrasound sensors or the like. 
     In order to be able to advance the pig within the pipe using the medium transported therein, the pig has a pig body comprising collars which seat tightly on the inner side of the pipe and are subjected to the flow pressure of the medium being transported. 
     In order to be able to check pipes which are under water or below the earth&#39;s surface, each pig must be introduced into the pipes through an entrance location. In particular for the case of underwater conduits, this is extremely expensive, since complicated and expensive lock mechanisms having expensive valves must be provided therefor. To effect entrance, it is then necessary for a diver to dive to substantial depths in order to be able to introduce the pig into the pipe being examined. Since the pipes for the medium being transported, e.g. oil, are laid at up to 300 m of depth in water and since they have a substantial diameter of e.g. 42 inches, such an entrance lock mechanism having a diameter of this size cannot be passed from the bottom up to the surface of the water, since the weight of such a entrance pipe would be prohibitive. 
     For this reason, it is the underlying purpose of the invention to create a device of the above mentioned kind which facilitates a simple entrance into a pipe conduit while avoiding the above mentioned disadvantages. 
     SUMMARY OF THE INVENTION 
     This purpose is achieved in accordance with the invention with a device for inspection of pipes of the above mentioned kind in that at least one of the collars is configured in a radially expandable fashion. The radial expansion preferentially is effected by pivoting. 
     The solution in accordance with the invention allows the pigs to be introduced through entrance pipes having small diameters e.g. a diameter of 28 inches (corresponding to approximately 60 cm) and into a main conduit of 40 inches (corresponding to 1 m). The collars effecting the advancement have a smaller diameter in the entrance pipe which first expands into one of larger diameter upon entrance into the main pipe. In this manner, advancement of the inspecting pig can be reliably effected both in the entrance pipe as well as in the main pipe. 
     A preferred embodiment provides that the expandable collar has an expanded diameter which is larger than that of collars whose radius is constant. Whereas the former expandable collars serve for transport of the pig in the main conduit or pipe of 42 inches, the collars having a non-changing radius provide for transport in the entrance pipe having a diameter of 28 inches. 
     At least one of the collars having fixed radius is preferentially disposed as a nose on the front side of the pig facing the direction of motion. These so-called “nose collars” serve for reliable drive of the pig in the entrance pipe and for removing the pig from the entrance pipe. 
     In a further improvement, the radially expandable collars are self-expanding. No auxiliary measures are thereby needed to erect the collars upon transition from the entrance pipe into the main pipe so that they assume their expanded position in the transitional region automatically and reliably. In order to achieve this, the radially expandable collars preferentially comprise a spider which can angle-off about the periphery thereof at least once opposite to the drive direction of the pig and having a plurality of radially extended braces as well as at least one sealing disc disposed on the braces and made from flexible material. The spider is preferentially made from polyurethane. The spider guarantees the folding-up of the collar in the entrance pipe of smaller diameter so that the collar is inactive during this time, while simultaneously effecting erection of the collar when passing from the entrance pipe into the main pipe. The spider furthermore keeps the collar stiff during passage of the pig through the pipe being inspected. The sealing disc reliably seals those regions of the spider which are left open by the radially extending braces so that the medium reliably interacts with the collar to drive the pig. 
     A further improvement prevents the expandable collar from flipping over during expansion in that the expandable collar is held in its expanded position by anchor elements which can seat on the pig body prior to expansion and are fixed thereto. These elements are preferentially flexible members such as chains. The anchor elements can also however be telescoping elements or could be rods in linked connection with another. A combination of these types of anchor elements is also possible. 
     In order that the expandable collars are pressed against the pipe to be inspected when they are loaded by the flow pressure, the collars preferentially have a substantially plate-like shape when expanded. The collar serving as the nose element is preferentially ring shell shaped. 
     In a further preferred embodiment, radially expandable support and guide rollers are provided (relative to the drive direction of the pig) behind each expandable collar. These support and guide rollers, in a further improvement, are fixed on arms which can be outwardly displaced to seat at the inner wall of the pipe under the action of a spring force. This type of support and guide rollers or roller sets formed by such support and guide rollers, guide the pig body along the inner wall of the pipe. The roller sets align the moving pig within the pipe and reduce wear on the outer periphery of the collar. Since these roller sets are also expandable in the radial direction, they can likewise seat on the pig body during introduction through the entrance pipe or can be slightly separated from the pig body to also provide for alignment of the pig in the entrance pipe during the entrance process. 
     A further preferred embodiment provides that the pig comprises two pull units linked to each other and having support and guide rollers of which only the (as seen in the drive direction) first pull unit has an expandable collar. The first unit thereby serves as the actual pull unit to guarantee the drive function during inspection in the main pipe. The second pull unit secures the drive during transition from the narrower entrance pipe into the larger main pipe. In order to guarantee sufficient stability for the individual pull units, each pull unit is thereby provided with at least two sets of support and guide rollers. In addition, at least one collar having a non-changing radius is provided for on each pull unit which is substantially disc-shaped. These collars guarantee drive in both pull units and thereby the transport of the entire pig. If the first pull unit is already located in the main pipe during the transition from the entrance pipe into the main pipe, wherein its collar is radially erected, the drive function is assured during this time by the second pull unit and the collar disposed thereon, still located in the entrance pipe. When the second pull unit enters into the main pipe, the collars as well as the support and guide rollers of the first pull unit have already been erected to guarantee continued motion in the main pipe. The flat configuration for the additional collar takes into consideration the limited space on the pull unit and in the entrance pipe. 
     After the pig has reached the main pipe, pig drive is effected by the first pull unit and the expandable collars disposed thereon along with the support and guide rollers and the second pull unit is no longer needed for stabilizing the first pull unit and for drive purposes. In accordance with an improvement, the second pull unit acting as a guide unit is therefore axially displaceable relative to the first unit. It can thereby move towards the pig inspection units and stabilize the pig. 
     Further advantages and features of the invention can be derived from the claims and the following description in which an embodiment is described in greater detail with reference to the drawing. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 shows a complete inspection pig in the expanded state as assumed in a pipe of large diameter; 
     FIG. 2 shows the inspection pig of FIG. 1 in an entrance pipe having a narrower diameter and in a compressed introduction state; 
     FIG. 3 shows a side view of the first pull unit of a pig; 
     FIG. 4 shows a side view of a second pull unit of the inspection pig; 
     FIG. 5 a  shows a plan view of a reinforcement section of an expandable collar forming a spider; 
     FIG. 5 b  shows a side view of the reinforcement section of FIG. 5 a;    
     FIG. 6 a  shows a plan view of a sealing ring connected to the reinforcement section of FIGS. 5 a  and  5   b ; and 
     FIG. 6 b  shows a side view of the sealing ring of FIG. 6 a.   
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The pig  1  shown in FIG. 1 has, in the embodiment shown, six individual modules of which the first module  2  is a pull unit, the second module  3  is a pull and guide unit  3 , the third and fourth modules  4  and  5  are inspection units and the fifth and sixth modules  6  and  7  are an electronic unit  6  and a power supply unit  7 . The electronic unit  6  generally has the processing and memory devices and the power supply unit  7  generally has batteries or rechargeable batteries to supply the electronic unit  6 , the sensors etc. 
     The individual modules  2  through  7  are each guided in the pipe via support and guide rollers  8   a-f  which are pushed outwardly under spring force against the inner wall of the pipe. Motion of the pig  1  in the pipe is effected by the flow pressure of the medium passing through the pipe, e.g. oil, acting on the collars  9 ,  10   a ,  10   b ,  11 ,  12  disposed on the pull units  2 ,  3 . In the embodiment shown, the collars  9 ,  11  and  12  are adapted for use in a pipe having a narrow diameter in the region between  26  and  28  inches. The collars  10   a ,  10   b  are inactive in such a narrow pipe but, during transition of the inspection pig  1  into a second pipe having e.g. a diameter on the order of 40-42 inches, pivot (rather than spread-out) to radially expand and assume the drive function for the pig  1 . The narrow pipe in the embodiment shown is the entrance pipe  13  for introducing the pig  1  into the main pipe which is being inspected. 
     The two inspection units  4 ,  5  have pole pieces  14 ,  14   a  on their outer periphery in the form of brushes. A sensor  15  is disposed between each pair of successive pole shoes of an inspection unit. The sensors  15  can e.g. be magnetic sensors for checking the main pipe for defects, cracks or the like. The sensors  15  are also radially expanded up to the periphery of the pipe as can be seen by comparison to FIGS. 1 and 2. 
     The modules  2 ,  3 ,  4 ,  5  form pig bodies, seat on guide rods  16 ,  17 ,  18 ,  19  and are connected to each other via linkages  20 ,  21 ,  22 . An additional linkage  23  is provided between the inspection unit  5  and the electronic unit  6 , and the electronic unit  6  is connected by means of a linkage  24  to the power supply unit  7 . 
     The linkages  20 - 24  in accordance with the invention allow the pig  1  to also be guided through pipes having small radius of curvature. The described configuration of the inspection pig  1  is only exemplary to illustrate the invention and other arrangements for the modules  4 - 7  can be provided for. For example, they can be integrated with each other or can be combined with other units. 
     Whereas FIG. 1 shows the inspection pig  1  in the expanded state, the inspection pig in FIG. 2 is shown in its compressed state during introduction through the entrance pipe  13 . Both the pull units as well as the inspection units are thereby radially compressed and also the support and guide rollers  8   e ,  8   f  of the modules  6 ,  7  also seat radially on their respective pig bodies  25 ,  26 . During this entrance state represented in FIG. 2, the radially expandable collars  10   a ,  10   b  in accordance with the invention as well as the sensors  15  of the inspection units  4 ,  5  are radially compressed. The collars  10   a ,  10   b  and the sensors  15  radially expand only after entry into the main pipe. 
     FIG. 3 shows the front pull unit  2  in the expanded state and thereby the operational state of the pig  1 . In other words, the two collars  10   a ,  10   b  serving for drive are expanded by pivoting and their radius is thereby adjusted to the larger diameter of the main pipe to be inspected. 
     The radially expandable collars  10   a ,  10   b  are substantially plate-shaped in their expanded position and comprise a spider  24  constituting a frame as well as a sealing disc  26  disposed on the spider  25 . The collar can preferentially be made from a single piece. The spider  25  comprises a ring  28 , having a circular opening  27 , on which braces  29  extend in a radially outward direction, distributed evenly about the outer periphery thereof. These braces  29  can thereby be angle-off relative to the ring  28  or can pivot under the action of a radial force. The sealing disc  26  likewise has a circular opening  30  which is aligned with the circular opening  27  of the spider  25  as well as a ring  31  having a circular opening  30  which is aligned with the ring  28  of the spider  25 . This ring  31  is surrounded by a second ring  32  introduced as a sealing skin onto the braces  29  to elastically seal the spaces between the braces  29 . The thickness of this ring  32  thereby changes about its girth. In the region between the braces  29 , the thickness is somewhat less that in the region of the braces  29  to effect a larger degree of flexibility. 
     As a comparison to FIGS. 1 and 2 shows, the expandable collars  10   a ,  10   b  are initially folded back during the entrance procedure in opposition to the entrance direction indicated by arrow A via their braces  29  and then erect themselves to assume a radially expanded position effected by a pivoting motion from the back towards the front into the plate-shaped expansion position of the collars  10   a ,  10   b . In other words, the radial expansion in accordance with the invention is not effected through a pure radial displacement by spreading-out of elements of the collar in an outward direction, rather by a pivoting motion of the braces  29  and of the sealing disc elements attached thereto. In order that the braces  29  and the sealing discs  26  attached thereto do not flip over during erection in the drive direction (indicated by symbol B) and maintain the convex-concave shape of the collars  10   a ,  10   b , the collars  10   a ,  10   b  are fixed to the pig body  16  at their plate-shaped inner side, that is to say the side  34  facing away from the drive direction B, via anchor elements  33   a ,  33   b , in this case, in the form of chains. Towards this end, eyelets  35   a ,  35   b  are mounted in the region of the struts  29  to the plate-shaped inner side  34  of the collars  10   a ,  10   b . The collars  10   a ,  10   b  are provided with anchor plates  36   a ,  36   b  in the vicinity of the struts  29  on their inner  34  as well as their outer sides to secure attachment of the eyelets  35   a ,  35   b . The anchor chains  33   a ,  33   b  are then suitably anchored at their ends  37   a ,  37   b  facing away from the collars  10   a ,  10   b.    
     The support and guide rollers  8   a  disposed (relative to the drive direction B) behind the collars  10   a ,  10   b  are likewise fixed for pivoting to the pig body  16  via arms  38   a . The roller sets comprising the support and guide rollers  8   a  as well as the arms  38   a  can likewise seat, in opposition to the direction of entrance A in FIG. 2, on the pig body  16  and subsequently radially erect through pivoting from the back towards the front. The pivot angle is thereby smaller than 90°. 
     For folding-up as well as pivoting out, the arm  38   a  is fixed to a pivot element or lever  39   a  at its end opposite the mounted support and guide rollers  8   a , the pivot element having an end  46   a  fixed for pivoting to a frame  41   a  attached to the pig body  16 . Its other end  42   a  is borne for pivoting at an end of a spring element  43   a . This spring element  43   a  moves in the direction of arrow B for folding in the support and guide rollers  8   a  to thereby displace pivot element  39   a  at its end  42   a  facing the spring element  43   a . The arm  38   a  is correspondingly pivoted toward the pig body  16 . An opposite motion is effected for radial erection. 
     The same erection mechanism and configuration is used in the roller set of the second pull unit  3  having the support and guide rollers  8   b . The same components are thereby indicated with the same reference symbols. 
     As shown in FIGS. 3 and 4, the collar  11 ,  12  configured as a sealing disc is disposed in front of the second collar  10   b  and the second roller set in each case. 
     The collar  9 , provided as a drive element during the entrance phase and having a ring disc shape, is disposed at the (relative to the travel direction B) front end  44 . It has an appropriate pull element  45  on its front side for removal at the extraction location.