Abstract:
An external tester defines a sealed chamber around a pipe joint, such chamber then being filled with fluid under very high pressure. After introduction of fluid into the test chamber is terminated, a determination is made as to whether or not the pressure is reducing, any such reduction indicating that a leak is present in the pipe joint. To define a test chamber which is perfectly sealed so that fluid will not escape otherwise than through a leak in the pipe joint there are provided longitudinal sealing elements and arcuate sealing elements interrelated with each other and with an insert of the longitudinal elements. The inserts stiffen and mount the longitudinal elements, provide indexing of the casing sections, and prevent extrusion of the seal rubber, all in such a manner that no cracks remain through which the fluid may escape.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to the field of apparatus for creating sealed test chambers externally around pipe sections and similar devices, the seals being such that many thousands of pounds of pressure per square inch may be contained in the chambers. 
     2. Description of the Prior Art 
     There exist substantial numbers of prior art patents for apparatus wherein longitudinal and circumferential seals are provided in order to permit a sealed chamber to be defined around a section of pipe. Patents of this type include, for example, U.S. Pat. Nos. 2,255,921 and 3,744,822. However, the constructions set forth in these and other patents are believed to be incapable of containing and sealing fluid pressures anywhere as near as high as those which may be contained and sealed with the present apparatus and seals. It is to be understood that the higher the test pressure the more rapidly and readily a leak may be detected. 
     It is extremely important that the apparatus be adapted to open and close rapidly to laterally receive a pipe section when the apparatus is in open condition and to seal pressure of such extreme magnitude that even minute leaks will be readily apparent in a short test period. 
     Insofar as applicants are aware, the only prior art external tester apparatus which has achieved major commercial success in the oil well industry is that described in U.S. Pat. No. 3,371,521 and improvements thereon which are specified in a Notice of Prior Art found in the present application file. Such apparatus, however, is deficient in important respects, one of which is that it requires a unitarily molded complex packer. The packer is such that the fluid in the test chamber only contacts rubber. Such packers are not only complex and expensive to mold but also bulky to ship and store. Furthermore, when one portion of the packer wears out the entire packer must be discarded, it being impracticable or impossible to replace any one portion of the packer. A further disadvantage relative to such packers is that they are sometimes difficult to load into the casings in the field, this being because the as molded packer circumference at its exterior is larger than the circumference of the closed casing at its interior. 
     In a U.S. Pat. No. 3,975,945 to Hauk and Carstenson, and in our earlier U.S. Pat. No. 4,099,405 there are disclosed leak testers involving seals made of several elements, including pairs of arcuate segments at either end and a pair of strip seals. Such sealing arrangements have a number of advantages, including ready mass production, shipping and storage, ease of mounting in the casing in the field, separate replaceability when worn, and manufacture in small, common molds. It has been found, however, that strip seals of the above-mentioned U.S. Pat. Nos. 3,975,945 and 4,099,405 are not satisfactory for leak testing under certain very high pressures. In particular the use of an indexing bar such as the bar 88 of FIG. 20 of U.S. Pat. No. 3,975,945, which must fit into an indexing slot in the other casing section, inherently requires a certain amount of tolerance in the sliding fit of the bar into the slot. Without some amount of tolerance the bar cannot enter and be removed from the slot as the casing sections close and open. These tolerances provide a space sufficient to permit extrusion of seal strip rubber from the interior of the pressurized chamber under certain very high testing pressures. Further, it is found that the mounting of the strip seals to the casing is difficult since problems are encountered in the field in aligning apertures of strip seal sections and casing for insertion of securing bolts. Problems also have been encountered in sealing of the interconnection between the strip seals and the arcuate seal segments in the arrangements of these patents. 
     Accordingly, it is an object of the present invention to provide a leak tester having a number of individual and separately replaceable sealing elements and which avoids or eliminates problems referred to above. 
     SUMMARY OF THE INVENTON 
     The present apparatus and method comprise at least two end seals at each end of the test chamber and at least two strip seals extending between the sets of end seals. In accordance with one aspect of the invention, each strip seal extends along and into an outwardly facing recess of the end seals and the end and strip seals are bolted to each other and to the casing by a single bolt extending therethrough. At this point of attachment on the end seal there is provided a relatively thick insert to decrease the amount of rubber and, therefore, to decrease compressibility at this area. 
     Another significant aspect of the invention comprises the use of an insert bar that provides a multiplicity of functions, which functions are provided by several different elements in prior devices. Such functions include (a) reinforcement of the strip seal rubber body, (b) attachment of the strip seal to the casing, (c) indexing of the casing sections during closing, and (d) prevention of extrusion of the rubber body through the longitudinal joint between closed casing sections. This multiplicity of functions is provided by positioning a non-deformable bar insert so as to have an outer surface planar with the outer surface of the rubber body and fixing outwardly projecting connecting elements to the insert for projection into and securement to the casing. The positioning is such that the insert is held against one casing section on one side of the longitudinal casing joint and bridges such joint in close, tight contact with the side of the other casing section when the sections are closed. The rubber body is received within a longitudinal recess formed in the casing sections at the longitudinal joint. Thus the insert enhances the compression ratio (that is, the percentage of compression) of the rubber body which occurs when the casing sections are closed. In this arrangement, the rubber body is not only compressed between the two sides of the recess that receives the strip seal but it is compressed between one side of the recess and one edge of the strip seal insert itself. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an isometric view showing the present leak testing apparatus in closed condition; 
     FIG. 2 is a top plan view, partly in section, illustrating the apparatus in fully closed condition, an illustration of a lock pin cylinder being omitted; 
     FIG. 3 is a view corresponding to FIG. 2, but showing the parts in open position; 
     FIG. 4 is a fragmentary vertical sectional view of the apparatus; 
     FIGS. 5 and 6 are sectional views taken on lines 5--5 and 6--6 of FIG. 4; 
     FIG. 7 is an isometric view, partly exploded, of the various sealing elements of the present invention; 
     FIG. 8 is an exploded isometric view showing in phantom lines the rubber bodies of some of the seal elements and showing in solid lines the inserts contained in such elements; 
     FIG. 9 is a fragmentary section showing the strip seal and casing segments in closed condition; and 
     FIG. 10 is a view like that of FIG. 9 showing the casing segments in nearly closed, but partly open, position. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The apparatus comprises two semi-cylindrical casing sections 10 and 11, the upper and lower ends of which are necked down, as indicated at 12 in FIG. 4. The casing is greatly and uniformly strengthened and reinforced by a symmetrical cage formed of opposed ribs which are respectively welded to casing sections 10 and 11, the cage also being formed of opposed bars which extend between pins through the ribs. The entire apparatus, other than the various sealing strips to be described below, including their mode of connection to the casing sections, is substantially the same as that described in U.S. Pat. Nos. 3,975,945 and 4,099,405 and may in fact be substantially similar to that described in U.S. Pat. No. 3,371,521, except, for the various modifications of the casing sections required to cooperate with the several sealing elements as will be described more particularly hereinafter. Therefore, a full and more detailed description of the casing sections and their operation is found in the prior patents and the disclosures of these patents are incorporated by this reference as though fully set forth herein. 
     Briefly, ribs 15 are welded to casing section 10 and ribs 16 are welded to casing section 11. Four pins 17-20 are provided of which pins 17-19 are permanently fixed in position, and fourth pin 20 is a retractable lock pin which is cylinder operated as will be described below. 
     The opposed pins 17, 18 at the rear of the cage, the rear being a portion diametrically opposite the region which opens to receive a section of pipe to be tested, are connected by hinge bars 24. The pins 19 and 20 at the front of the cage are connected by lock bars 25 which are pivotal as stated below. Hinge bars 24 and lock bars 25 are sufficiently thick to fill in the spaces between adjacent ones of ribs 15 and 16, the result being that all of the pins 17-20 are in total shear and not subjected to bending stresses. 
     The described cage and related apparatus are connected to a suitable valve housing indicated at 26 in FIG. 1 and are suitably suspended by means (not shown) at the well head of an oil well. The upper and lower walls of the valve housing 26 extend forwardly and are bolted respectively above the uppermost ones of ribs 16 and below the lowermost one of such ribs. 
     In order that the casing formed by elements 10 and 11 and associated parts may define a sealed chamber (the &#34;test chamber&#34;) around a section of pipe, seal means are provided within the casing as described below. Referring, for example, to FIG. 4, the apparatus is particularly adapted to define an annular test chamber 27 wherein the pipe section is formed by two pipe elements 28, 29, which are connected by a threaded collar 30. Such pipe may be drill pipe, casing pipe and the like. As described below, the seal means is primarily rubber and includes portions which are compressed in response to closing of the casing. Thus closing of the casing requires a certain amount of force in order to overcome resistance provided by the rubber and to create a certain amount of augmented sealing compression. 
     Mechanisms for opening and closing the casing and locking the same are illustrated in FIGS. 2 and 3, which show the casing and closing mechanism in closed and open position, respectively. As previously mentioned, this mechanism is shown and described in greater detail in U.S. Pat. Nos. 3,975,945 and 4,099,405. 
     The casing is closed by apparatus, including hooks 40, one of which is mounted near the top of the casing and one of which is mounted near the bottom thereof. Each hook is pivotally connected by a short pin 41 to a lever 42, one end of which is pivoted to pin 19 for lock bars 25. The other end of each lever 42 remote from pin 19 is pivoted to a pin 43 and thus to an actuating cylinder 44. Each cylinder 44 is in turn pivotally connected to a pin 45 which is fixed between the upper and lower walls of valve housing 26. The hooks pivot about the pins 41 which are supported by levers 42. 
     Hooks 40 and the associated levers 42 form compound lever systems which, when cylinders 44 are shortened, cause the hooks to move to fully close the casing and its associated cage, thus creating a preliminary sealing compression in the seal means. The hook members hook around index and closing pins 46 which are provided in grooved blocks 47 on the uppermost and lowermost ribs 15. 
     The particular details of operation and type of closing system employed are not a significant part of this invention as long as the closing is forcibly accomplished and sufficient to provide adequate preliminary compression on the seals and to maintain the casing segments in close juxtaposition (in closed position) in the presence of the extremely high pressures introduced to the interior thereof during the test period. Thus the lever systems may employ locking hooks of the type shown in U.S. Pat. No. 3,371,521, or in the prior U.S. Pat. Nos. 3,975,945 and 4,099,405. The hooks may move over center or may be arranged so as not to move over center. 
     When the hooks 40 are in position such that they do not bear against their pins 46, they may be pivoted to a wide open position of FIG. 3 due to the operation of a cylinder 48, pivoted to a bracket 49, which is welded to a tube 50, the latter in turn being welded to the underside of top lever 42. 
     The other end of cylinder 48 is connected to a crank 52 on a sleeve which is rotatably mounted on pin 43. Welded to the upper and lower ends of the sleeve are additional cranks 55 which pivotally connect through links 54 to central outer regions of the hooks 40. 
     In order to cause pivotal movement of the lock bars 25 to the wide open position of FIG. 3, thus greatly facilitating lateral introduction of the pipe 28, 30 into the test chamber 27, an additional cylinder 56 is pivotally connected to a bracket 57 which in turn is bolted to one of the ribs 16. The other end of this cylinder 56 is connected to a crank 59 which is mounted on one of the lock bars 25. This one lock bar 25 is in turn connected to all of the other lock bars by means of a vertical connector bar 60. Bar 60 is rigidly held in place so that there is a rigid association between all the lock bars 25 whereby they will close to precise positions. 
     After the apparatus has been unlocked and unhooked, the casing may be opened to the position shown in FIG. 3 by operation of cylinders 62, only one of which is shown. One end of each cylinder 62 is pivoted at 63 to a pin which extends between the upper and lower walls of housing 26. The other end of each cylinder is pivoted at 64 to a bracket 65 bolted to one of the ribs 15. 
     In the general operation of the tool thus far described the pipe elements 28, 30 are introduced laterally into the apparatus when the casing and cage are in the wide open position of FIG. 3, following which cylinders 62 are actuated to close the casing and cage. Cylinder 56 is operated to pivot the lock bars 25 to the closed position, cylinder 48 is operated to effect pivotal movement of hooks 40, and cylinders 44 are operated to cause the hooks to shift pins 46, to thereby effect pressure closing of the casing despite the presence of protruding rubber in the seal means. 
     The lock pin 20 is then shifted downwardly by means of its connection to a piston 70 which is mounted slidably in a vertical cylinder housing 71 having a flange 72 at the lower end thereof. The flange 72 is suitably connected by means (not shown) to a corresponding plate 73 which is mounted to the uppermost rib 15. The position of mounting is such that the pin 20 registers with the uppermost bore in ribs 15. 
     As in the case of the various cylinders 44, 48, 56, and 62 described above, cylinder housing 71 is associated with suitable hydraulic lines or pneumatic lines (not shown) and with valves (not shown) which are incorporated in housing 26. Each of these cylinders is double acting so that the operation of the associated valve means may shift the various pistons in both directions. 
     Reinforcing ribs 15 are provided with a number of aligned bores 74 and lock bars 25 are provided with a corresponding and cooperating series of bores 75. Upon a closing of the casing by operation of the various cylinders, the bores 74 and 75 are all mutually aligned by means of stop and shim devices more specifically described in the prior patents, and thus the lock pin 20 may be driven through all of these aligned bores to hold the casing sections in closed position. 
     During testing operations with the casing closed around a pipe joint, a suitable liquid such as water, for example, is introduced into the test chamber 27 by means of a conduit 76 connected by means of a fitting 77 to an aperture extending through the casing side wall. Existence of a leak in the pipe joint is indicated by a reduction of pressure within the test chamber, as displayed by a gage 78 mounted to housing 26. 
     There are formed in the respective casing sections 10 and 11, extending for substantially the full length thereof, namely between the necked down regions 12, longitudinal recesses which are preferably diametrically opposite each other. These longitudinal recesses are adapted to receive longitudinal sealing elements or sealing strips. 
     Each recess is formed of two nearly equal and symmetrical rebated portions formed in facing closure surfaces 80, 81 of casing sections 10 and 11, respectively, when the two sections are in closed position (FIGS. 9 and 10). Each rebated portion of the facing surface of the casing section includes a side wall 82, 83 and a bottom wall portion 84, 85, which bottom wall portions are co-planar when the casing sections are closed. The recess side walls 82, 83 extend substantially radially whereas the co-planar bottom wall portions 84, 85 extend in a tangential direction. The recess formed by the two rebated portions is substantially symmetrical about the longitudinal casing joint. 
     To seal the longitudinal joint between the facing surfaces 80, 81 of the casing sections and to provide for indexing of the two sections during closure, the longitudinally extending recess at each of the longitudinal casing section joints is provided with a seal strip or longitudinal sealing element 90, 91, respectively. The indexing function of the sealing element assures alignment of the two casing sections as they are closed to properly position these sections relative to one another along a radial plane of the casing. 
     Each seal strip comprises a unitary elongated molded rubber body 92, 93 having a substantially rectangular cross section (FIG. 10). Some of the corners of the rubber body may be rounded such as the corner 95 which is rounded to fit a similar rounded corner 96 formed at the junction of the recess walls 83, 85 of casing section 11. The opposite corner 97 of the rubber body may be more sharply angulated to conform to the more sharply angulated corner formed by the junction of walls 82, 84 of casing section 10. At each end of the rubber body 92 there is formed a laterally outwardly facing recess or notch 94 to enhance its engagement with the arcuate sealing segments to be described below. 
     Molded to and within the rubber body 92, 93 of each of the seal strips is non-deformable insert bar 99, 100 which performs a number of functions. Since the two seal strips 90, 91 are identical to each other, only one need be described. As previously mentioned, the insert 99 (a) reinforces the rubber body, (b) enables the rubber body to be securely mounted to its casing section, (c) provides an indexing function, and (d) prevents extrusion of the rubber body. The insert preferably comprises a rigid flat elongated metal strip running substantially the full length of the rubber body and having a rectangular cross section of which an outer free edge is beveled as indicated at 101 (FIG. 9). Insert bar 99 has an outer surface 102 that is co-planar with an outer surface 103 of the rubber body 92. Thus the insert bar itself forms part of the outermost surface of the seal strip. To enhance the attachment of the insert to the rubber body, which is molded about and to the insert, the latter has fixed thereto a number of holding brackets such as those indicated at 104, 105 (FIG. 8). Although the brackets may take many different configurations, it is preferred at present to employ brackets that, as illustrated, are of substantially channel shape, having side legs welded to the inner surface of the bar 99 and having a channel web spaced from the bar and apertured so as to enhance flow of rubber into the area between the bar and the holding bracket during the molding operation. 
     In order to mount the entire seal strip to the casing, the strip insert is formed with a plurality of longitudinally spaced apertures into which are inserted and securely affixed, as by welding for example, a number of threaded studs such as those indicated at 107, 108. The studs extend outwardly from the seal strip, from the outer surface of the insert bar 99, through correspondingly positioned apertures formed in the casing wall, and are secured thereto by nuts 109, 110. 
     Fixed to the inner surface of each end portion of the insert bar 99 is a right angle bracket 113, 114 that defines a gap clip having an inwardly projecting flange extending along the end of the rubber body to aid in preventing extrusion thereof. Each seal strip is further provided with an aperture, such as aperture 115, extending completely therethrough closely adjacent each end for further connection to the casing and to the circular seal segment as will be described below. 
     Each end of the test chamber 27 is sealed by a pair of arcuate sealing segments 120, 121, 122, 123. Just as the two sealing strips are identical to each other, each of the pairs of circular sealing segments at the opposite ends of the test chamber are identical to each other. Not only are the pairs of sealing segments identical to each other, but each segment of each pair is identical. Thus only one substantially semi-circular sealing segment type need be made and stocked and will suffice to replace any one segment, regardless of which end or side of the casing it is for. Since each segment is identical to each other segment, only one need be described. Each segment comprises a circular body extending for slightly more than a full half circle, and having a generally rectangular cross section. The molded rubber body is stiffened by a generally arcuate metal insert 128 having upwardly and downwardly projecting teeth, such as teeth 129, 130, to enhance securement of the insert to the rubber body 126, the latter being significantly reinforced by the insert. One of the end faces of the semi-annular rubber body 26 is formed with a projection in the form of a pair of outwardly converging inclined surfaces 131, 132 and the other end face is formed with a corresponding pair of inwardly converging surfaces 133, 134, the two end surfaces thus forming respective projections and grooves that mate with the corresponding grooves and projections of the other segment of a pair (see FIGS. 5, 6, 7, and 8). 
     Each arcuate insert 128 extends from a point adjacent one end, such as end 133, 134 of body 126, to a point spaced from the other end of such body. At such other end of the rubber body preferably (but not necessarily) the end at which the outwardly converging surfaces 131 and 132 are formed, the radially outward surface of the rubber body is formed with an inwardly extending and outwardly facing recess 136. Just within the bottom wall of such recess, completely molded within the rubber body, is a second metal insert 137 having a somewhat flattened cylindrical configuration and having a thickness that is a major portion, preferably a little more than one-half, of the total thickness of the annular segment. Insert 137 is formed with an outwardly projecting boss 138 that extends to the outermost surface of the rubber body 126. The boss is drilled and tapped to receive a connecting bolt 140 adapted to extend through a hole in the casing section 10 and through a hole 115 near the end of the seal strip. 
     Prior to closing of the casing sections, each segment extends for substantially more than 180 degrees in order to insure that there will be a significant amount of initial sealing compression between the interengaging end surfaces of the segments when the casing is closed. 
     The notch 94 at opposite ends of the seal strips permit such upper ends to be a snug fit within the rectangular section of the recess 136 of the segment. 
     In assembly of the sealing elements to the casing sections, strip seal elements 90, 91 are first positioned adjacent the recessed, rebated portions of the associated casing sections 10 and 11, respectively. The threaded studs 107, 108, etc., are positioned at the apertures of the casing sections, extended therethrough and bolts 109, 110, etc., are secured to thereby fixedly attach the entire sealing strip firmly and securely to its respective casing section. It will be noted that such a method of attachment is considerably easier than a method which does not employ the fastening studs already fixed to the insert. In prior methods where separate bolts are provided, it is first necessary to position the sealing strip so as to insure alignment of all of the sealing strip apertures with similar apertures of the casing section and then insert the bolts through such aligned apertures. In the present arrangement no such apertures need be aligned. It will be noted that the outer surface of reinforcing strip 99 is in close abutment with the bottom wall portion 102 of this part of the longitudinal recess of the casing sections. Thus one sealing strip is secured to one casing section and the other strip is secured to the other casing section. The sealing strips each project laterally of the casing section and face. 
     The width of the rubber body 92 is greater than the width of the recess between side walls 82 and 83 when the two casing sections are in the closed position of FIG. 9. Thus, during closing of the casing sections, the apparatus will approach a position, such as illustrated in FIG. 10, wherein the opposing casing section surfaces 80, 81 are spaced from each other and yet the wall 83 now nearly contacts the side wall of the rubber body 92 which is relatively more remote from the insert 99. Further motion of the two casing sections from the position of FIG. 10 toward the position of FIG. 9 will compress the rubber body. The arrangement and position of the insert 99 provides a greatly enhanced compression ratio during such compression. In other words, the ratio of the width of rubber in compressed condition (as shown in FIG. 9) to the width of rubber in non-compressed condition (as shown in FIG. 10) is considerably increased by reason of the fact that a lesser amount of uncompressed rubber is provided because of the particular positioning of the insert 99. Actually the rubber is compressed during this final closing motion between the side wall 83 of the rebated portion of casing section 11 and the end of insert 99 that faces this side wall. 
     After the seal strips 90, 91 are fixed to the casing sections with their upper and lower ends abutting the shoulders between necked down casing portion 12, the several arcuate seal segments may then be attached. Each seal segment is attached by pressing its groove 136 over the notched end 94 of the seal strip, aligning the aperture 115 in the end of the seal strip with the aperture in the insert 137 of the arcuate segment, and pressing the outer surface of the boss 138 of insert 137 directly against the inner surface of the rubber body 92. This provides an improved sealing connection between the seal strip and the arcuate segment to which it is attached. Bolt 140 is then inserted through the aperture in the casing section 10, through the aperture 115 in the end of the seal strip and is threaded into the tapped aperture of insert 137 to firmly and securely attach the arcuate segment and upper end of the seal strip to the casing and to achieve initial compression of the circumferential and longitudinal seals and the casing. 
     All four arcuate seal segments are similarly attached. 
     FIGS. 9 and 10 illustrate several of the functions of the insert 99. As the casing sections close from the position of FIG. 10 to the position of FIG. 9, bevel 101 of the non-deformable insert 99 will initially engage the inner edge of surface 81 of casing section 11 to snugly engage or to slightly press the latter radially outwardly. The casing sections 10 and 11 are so mounted that the bottom wall portion 85 of section 11 is at least co-planar with or positioned slightly inwardly of the plane of bottom wall portion 84 of section 10 to enhance the indexing action of the insert bar 99. Thus the beveled surface 101 of bar 99 will insure relative radial alignment of casing sections 10 and 11 as the two move toward their final closed position. Further, in this final closed position, the outer surface of the insert bar 99 is snugly positioned against both of the bottom wall portions 84 and 85 of the recess. It bridges the longitudinal joint of the casing and extends for a substantial distance on either side of the joint. The outer surface of the non-deformable insert 99 is positioned directly against the wall portions 84 and 85 and is further pressed against these wall portions by the test pressure introduced to the interior of the test chamber. The higher the pressure within the test chamber, the more tightly is the insert bar 99 pressed against the bottom wall of the casing section recess and the better it will operate to prevent extrusion of the rubber body of the seal strip. 
     It will be noted that the rectangular cross section groove 136 of the circular segment extends for the full length (axially of the cylindrical casing) of each segment and that the end portion of the seal strip, including both the rubber body and its insert, also extend for the full length of the segment to which it is attached. This arrangement affords increased area of sealing contact between the seal strip and the attached segments and enhances sealing of the joints therebetween. 
     Wedge means are provided to prevent longitudinal upward or downward extrusion of rubber in the arcuate seal segments. Such wedge means comprise at each end of the tool a backup ring formed in two halves or segments 145 corresponding to the two casing sections 10 and 11 and fixedly secured to the casing sections, the backup ring seating in the necked down section 12. 
     Movably mounted beneath the ring segments 145, which have inner inclined surfaces converging in a direction away from the center of the test chamber, are wedge segments 146, which are loosely held in position to the casing by screws (not shown). Wedge segments 146 have inclined surfaces which engage and cooperate with the inner inclined surfaces of the ring segments 145. The relationships are such that longitudinally outward movement of the wedge segments 146 resulting from testing pressures tends to cause inwardly directed movement of the wedge segments 146 into extremely close abutment with the adjacent regions of the pipe, thus increasing the longitudinal extrusion prevention function. 
     An improved, more efficient and greatly simplified set of sealing elements has been described for a leak testing apparatus, the elements including a unitary assembly in which a number of functions are performed by an insert of improved configuration and location and in which cooperation between arcuate end sealing segments and longitudinal sealing strips is greatly enhanced to provide a more effective mounting and sealing engagement of the sealing elements at the end of the test chamber. 
     The foregoing detailed description is to be clearly understood as given by way of illustration and example only, the spirit and scope of this invention being limited solely by the appended claims.