Device and method for installing a tubular joint sleeve for a pipe comprising an inner lining

Abstract

A device (20) for installing a tubular junction sleeve inside a pipe (1), having a mandrel (20a) of longitudinal axis (XX) supporting on its surface at least a first peripheral chamber (21) having a wall (21a) that is radially expandable by inflation. The first wall including at least one electrical connector (21b) suitable for being connected to one end of said heater wire. The connector being connected to an umbilical (24) including at least a compressed air feed duct for inflating the first chamber and an electrical power supply duct connected to the electrical connector. The device being characterized in that the mandrel supports on its outer surface a second peripheral chamber (22) having a wall (22a) that is radially expandable by inflation, and also a weld inspection device (23) arranged in the longitudinal direction of the mandrel.

Claims

1. A device suitable for installing a tubular junction sleeve inside an end of a first pipe element made of steel and internally lined with a thermoplastic material, and suitable for butt-joining the end of the first pipe element fitted with said tubular junction sleeve and an end of a second pipe element having internal lining of thermoplastic material, said ends of the two pipe elements abutting for welding together, said tubular junction sleeve having at each end a terminal tubular wall portion, at least one of said terminal tubular wall portions having a Joule-effect heater wire arranged at the outer surface of said terminal tubular wall portion suitable for creating by heating a zone of contact made leaktight by melting between the materials constituting at least a part of said terminal tubular wall portion and a terminal portion of said internal lining where they are in contact with each other, said device comprising: a mandrel extending in a longitudinal direction supporting on the outer surface of said mandrel at least a first inflatable chamber having a first peripheral wall that is radially expandable by inflation, said first peripheral wall having at least one first electrical connector suitable for being connected to one end of said Joule-effect heater wire, and said mandrel also having an umbilical comprising at least one compressed air feed duct for inflating said first inflatable chamber and an electrical power supply duct connected to said first electrical connector, wherein said mandrel also supports on said outer surface of said mandrel a second inflatable chamber having a second peripheral wall that is radially expandable by inflation and spaced apart from said first inflatable chamber in said longitudinal direction, and said mandrel also supports a weld inspection device, said umbilical passing inside said mandrel and including ducts for electrically powering said weld inspection device.

2. The device according to claim 1, wherein said weld inspection device is arranged in the longitudinal direction of the mandrel upstream or downstream relative to said first and second inflatable chambers.

3. The device according to claim 1, wherein said weld inspection device comprises: at least one ultrasound probe; and at least one water injection nozzle fed with water by a duct passing in said umbilical.

4. The device according to claim 3, wherein at least one of said ultrasound probe or said water injection nozzle suitable for being turned facing the terminal tubular wall portions about a turning axis arranged on a longitudinal axis of the mandrel.

5. The device according to claim 1, wherein said mandrel also supports a reversible shutter for shutting a passage between the mandrel and an inside wall of the tubular junction sleeve or of the internal lining of the pipe elements, said shutter being arranged in said longitudinal direction of the mandrel so that said weld inspection device is arranged between said reversible shutter and at least one said first or second inflatable chamber.

6. The device according to claim 5, wherein said reversible shutter is constituted by a third inflatable chamber having a peripheral wall that is radially expandable by inflation.

7. The device according to claim 1, wherein said expandable second peripheral wall of said second inflatable chamber includes at least one second electrical connector suitable for being connected to an end of said Joule-effect heater wire.

8. The device according to claim 1, wherein said first and second inflatable chambers extend over respective lengths L1 and L2 and are spaced apart by a distance d in the longitudinal direction of the mandrel such that when said first inflatable chamber is radially expanded to press against one of the terminal tubular wall portions, the second inflatable chamber is in a facing position and can press against a portion of a tubular inside wall of said tubular junction sleeve.

9. The device according to claim 1, wherein each of said inflatable chambers is formed by a flexible or semi-rigid tubular envelope of circular cross-section arranged around said mandrel which is cylindrical, wherein circular edges of each said tubular envelope join an outer wall of said mandrel in such a manner that under the effect of said inflatable chambers being inflated said tubular envelope takes on a convex bulging shape forming a radially expanded wall of said inflatable chambers.

10. A method of installing a tubular junction sleeve at one end of a first pipe element having an internal lining made of thermoplastic material, the method comprising: using the device of claim 1 in order to fasten said tubular junction sleeve to a terminal portion of said internal lining, by using a Joule-effect heater wire arranged at an outer surface of a first terminal portion of the tubular junction sleeve, to create a leaktight contact zone by melting together materials constituting at least parts of said first terminal portion of the tubular junction sleeve and of said terminal portion of said internal lining.

11. The method according to claim 10, further comprising the following steps: i.1) positioning said device inside said tubular junction sleeve in such a manner that at least said first inflatable chamber is in position facing said first terminal portion of the tubular junction sleeve with said first electrical connector facing an end of said Joule-effect heater wire, said second inflatable chamber facing an inside wall of a running portion of the tubular junction sleeve, and inflating at least said second inflatable chamber so as to secure the device with said tubular junction sleeve by pressing the expandable second peripheral wall of said second chamber against said inside wall of said tubular junction sleeve, resulting thereby in an assembly of the tubular junction sleeve and said device; i.2) moving the resulting assembly of the tubular junction sleeve and said device in the longitudinal direction and inserting said assembly inside a sleeve-free open end of said first pipe element until said first terminal portion of the tubular junction sleeve is in contact with said terminal portion of the internal lining of said sleeve-free open end of said first pipe element; i.3) inflating said first inflatable chamber to press it against the inside wall of said first terminal portion of the tubular junction sleeve so that said first electrical connector is connected to the end of a said Joule-effect heater wire; i.4) electrically powering said Joule-effect heater wire while simultaneously exerting pressure from said first terminal portion of the tubular junction sleeve against said terminal portion of the internal lining that are in contact with each other by inflating said first inflatable chamber in order to implement a weld zone by electro-fusion of the materials constituting at least parts of said first terminal portion of the tubular junction sleeve and of said terminal portion of said internal lining that are in contact with each other; i.5) deflating said first and second inflatable chambers and moving said device in such a manner that said weld inspection device is placed facing said first terminal portion of the tubular junction sleeve corresponding to said zone of welding by electro-fusion; i.6) inflating again the first and second inflatable chambers so that they press against the inside wall of the tubular junction sleeve and become secured thereto, and actuating said weld inspection device to inspect said weld; and i.7) deflating said first and second chambers in order to remove said device.

12. A method of making a pipe by using the device according to claim 1, by assembling first and second pipe elements, each including an internal lining, with a tubular junction sleeve inserted and fastened to one end of said first pipe element with a part projecting therefrom, the projecting part of said tubular junction sleeve defining a male end of said first pipe element suitable for being assembled with a sleeve-free end defining a female end of said second pipe element, said tubular junction sleeve having at each of its ends a terminal tubular wall portion, an outer surface of at least one of said terminal tubular wall portions having a Joule-effect heater wire suitable for creating, by heating, a contact zone made leaktight by melting together materials constituting at least parts of said terminal tubular wall portion and of a terminal portion of said internal lining that are in contact with each other, the method comprising the following steps: a) inserting said device inside said first pipe element so that said first inflatable chamber is arranged with said first electrical connector facing an end of said Joule-effect heater wire, and fastening said device inside said tubular junction sleeve by inflating said second inflatable chamber against an inside wall of said tubular junction sleeve; b) before or after step a) forcibly inserting the projecting part of said male end of said first pipe element into the female end of the second pipe element until said terminal tubular wall portion of said male end comes into contact with said terminal portion of the internal lining of said female end of said second pipe element to be assembled therewith; c) butt-welding the ends of the two pipe elements together; d) inflating said first inflatable chamber and connecting said first electrical connector to the end of the Joule-effect heater wire and electrically powering said Joule-effect heater wire, while simultaneously exerting pressure from said terminal tubular wall portion against said terminal portion of the internal lining in order to make a weld zone by electro-fusion in at least a fraction of the interface between surfaces of said terminal tubular wall portion and said terminal portion of the internal lining that are in contact with each other in order to make a contact zone that is made leaktight by melting; and e) deflating said first and second inflatable chambers.

13. The method according to claim 12, further comprising the following steps: step a) further comprises: a.1) using a pipe-laying tower of a laying ship to lower said first pipe element fitted with said tubular junction sleeve into proximity of the end of the second pipe element that is partially immersed at the bottom of the pipe-laying tower; and a.2) lowering said device into said first pipe element with said first and second inflatable chambers at least partially deflated; and following the deflating of said first and second inflatable chambers in step e), moving said mandrel so that said weld inspection device is placed facing said terminal tubular wall portion which is electro-welded; inflating the first and second inflatable chambers so that they press against the inside wall of the tubular junction sleeve and are secured thereto; and actuating said weld inspection device in order to inspect said weld.

14. The method according to claim 13, wherein weld inspection further comprises: actuating a reversible shutter to form a leaktight compartment defined between said first inflatable chamber by closing a passage inside the pipe, said leaktight compartment containing said weld inspection device; filling said leaktight compartment with water before actuating said weld inspection device to inspect said weld; and weld inspection, actuating said reversible shutter to open the leaktight compartment.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Other characteristics and advantages of the present invention appear in the light of the following detailed description with reference to the following figures, in which:

(2) FIG. 1A is a side view in section of a pipe of the invention assembled with the help of a tubular junction sleeve between two lined pipe elements or unit pipe lengths of the invention;

(3) FIG. 1B is a side view of an installer ship fitted with a so-called J-lay tower;

(4) FIGS. 1 to 9 show various steps of installing and welding the sleeve 3 at one end of a pipe element using a device of the present invention, which is shown diagrammatically;

(5) FIGS. 10 to 21 show various steps of assembling together two pipe elements with the sleeve 3 being installed and welded at one end of a first pipe element at the level of the sleeve-free end of a second pipe element and using a device of the present invention, which device is shown diagrammatically; and

(6) FIGS. 22 and 23 show a device 20 for installing a sleeve that comprises two chambers suitable for performing electro-fusion.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

(7) FIG. 1A shows a pipe 1 of the invention comprising at least two pipe elements 1.sub.1 and 1.sub.2 with internal lining 2 of polyethylene or polypropylene, the elements being assembled together end to end, and the ends of the two pipe elements being joined together by a weld 5. Each pipe element has an internal lining of thermoplastic material 2 of axis XX that coincides substantially with the axis of the pipe elements 1.sub.1, 1.sub.2, the linings presenting at each end respective conical terminal portions 2a of half-angle at the apex that are of thickness that is smaller than the thickness of the running portion 2b of said lining, thereby defining an internal surface of revolution of inside diameter that is greater than the inside diameter of the running portion 2b of said lining and terminating at a certain distance L from each end of said pipe element. The outer surface of each of said terminal portions 2a of smaller thickness of the inner liner is optionally locked by adhesive bonding 2c of the end of the liner at or near said terminal portion of smaller thickness 2a of the liner against the corresponding inner surface of the steel wall of the pipe, using an adhesive that is preferably of the polyurethane or the two-component epoxy type.

(8) A tubular junction sleeve 3 of thermoplastic material, preferably identical to the thermoplastic material of the internal lining 2, and of axis XX coinciding substantially with the axis of the pipe elements 1.sub.1, 1.sub.2 of the same outside diameter that is slightly smaller than the inside diameter of the pipe is inserted inside each of the abutting ends of the two pipe elements so as to extend over said terminal portions of the two linings 2a, 2b, by means of a device 20 of the invention as described below with reference to FIGS. 1 to 9.

(9) More precisely, in FIG. 1A, the internal lining 2 presents at each end of a pipe element a terminal portion 2a of thickness that is smaller than the thickness of the running portion 2b of said lining so as to define a concave shape with a frustoconical inner surface with a half-angle at the apex , of inside diameter that is greater than the inside diameter of the running portion 2c of said lining, and said sleeve 3 presents, at each of its longitudinal ends, a terminal portion 3a of thickness that is smaller than the thickness of the adjacent running portion 3b of said sleeve, said terminal portion 3a of the sleeve defining a convex shape suitable for extending over the smaller-thickness terminal portion of said lining 2a with which it is in contact, said terminal portion 3a of the sleeve defining a frustoconical outer surface 3-2 of outside diameter that is smaller than the outside diameter of the adjacent running portion 3b of the sleeve, and having the same angle at the apex as said frustoconical inner surface of said concave terminal portion of said lining. The conically-shaped terminal portions of the sleeve define a cylindrical inner surface 3-1 having substantially the same inside diameter as said running portion 2b of the lining and as said running portion 3b of the sleeve.

(10) In FIG. 1A, the sleeve presents a central portion 3c, i.e. about halfway along the sleeve in its axial longitudinal direction XX, with an outside diameter that is smaller than the outside diameters of the running portions 3b adjacent to said central portion 3c so as to leave an annular space 7, and an annular thermal protection part 8 is placed therein for protecting the sleeve while welding together the ends of the pipe elements, said running portions 3b of the sleeve presenting an outside diameter that is substantially identical to the inside diameter of the uncovered ends of said lining of the assembled-together pipe elements.

(11) The tubular wall of said sleeve presents thickness that is substantially constant in its central portion 3c and its adjacent running portions 3b, which thickness is substantially equal to the thickness of the running portion 2b of said internal lining 2, and said central portion 3c of the sleeve is suitable for deforming so as to adopt an inside diameter that is substantially identical to the inside diameter of the remainder of the sleeve under the effect of internal pressure from a fluid flowing inside the pipe in operation, which pressure is at least 1 MPa, and the thermal protection part 8 is itself also deformable under the same conditions of internal pressure inside the pipe so as to adopt a small thickness, preferably a thickness of less than 5 mm and more preferably less than 2 mm, said thermal protection piece more preferably being constituted by ceramic fibers in a form similar to cotton wool.

(12) It can be understood that: because of its substantially constant thickness, the central portion of the sleeve presents a constriction in outside diameter and in inside diameter during laying with the pipe being empty and at atmospheric pressure or when it is subjected to pressures corresponding to pressure values of less than 1 MPa (10 bars); and as soon as the inside pressure exceeds 1 MPa (10 bars), the thicknesses, in particular of about 5 mm to 20 mm, and the stiffness of the plastics material, such as polyethylene or polypropylene, enable the inside and outside diameters of the central portion to be increased by deformation, e.g. when a fluid, in particular water under pressure, flows inside the pipe and the sleeve, as occurs in water injection pipes for oil wells at a pressure greater than 5 MPa, and in particular lying in the range 25 MPa to 70 MPa.

(13) Because the pressure P.sub.0 outside the lining is much less than the internal pressure Pmax, this pressure has the effect of firmly pressing the constricted central portion 3c of the tubular junction sleeve 3 against the wall of the steel pipe, the ceramic fiber shield 8 being likewise flattened and then presenting a residual thickness of no more than 1 mm to 2 mm.

(14) The sleeve 3 presents a central portion 3c of constricted outside diameter that becomes pressed against the inside of the pipe as soon as the internal pressure exceeds 1 MPa to 1.5 MPa (10 bars to 15 bars) because of the flexibility of the thermoplastic material. To improve the deformability of this central portion 3c and of the adjacent transition zones, the thickness of these zones is advantageously smaller than the thickness of the running portion 3b of the sleeve by a proportion lying in the range 5% to 50%. Likewise, the central zone 3c and the transition zones, which are shown for clarity in the drawings of having sharply angled connections, are preferably connection fillets of large radius of curvature so as to avoid incipient cracks appearing in these zones.

(15) FIG. 1A shows a heater wire 4 forming a spiral, preferably a double spiral made up of two wire portions arranged side by side, forming two substantially equidistant spirals that are joined at a common end constituted by a hairpin-bend like those described in WO 2012/017171. Each spiral travels along said outer surface 3-2 of each said terminal portion of the sleeve. The two free ends of the wire have respective electrical power supply terminals connected side by side at a common electrical connector 4a on the inner surface 3-1 of the sleeve.

(16) FIGS. 1 to 9 show the various steps of installing a tubular junction sleeve 3 at one end of a pipe element 1.sub.1 using a device 20 for installing the sleeve. These operations may be performed on land or on the deck of the ship in a horizontal position

(17) A device 20 of the invention for installing a sleeve 3 as shown in FIGS. 1 to 9 is provided with a mandrel 20a of cylindrical shape extending in an axial longitudinal direction XX and having a longitudinal cylindrical central orifice within which there is placed an umbilical 20b that also serves as a cord for handling the device 20.

(18) In FIGS. 1 to 21, the device 20 has a first inflatable chamber 21 fitted with electrical connectors 21a arranged in the longitudinal direction XX at a distance d from a second inflatable chamber 22. The first chamber 21 is interposed in the longitudinal direction between firstly the second chamber 22 and secondly the weld inspection device 23 that is also supported by the mandrel 20a. The mandrel 20a also supports a third inflatable chamber forming an extendible wall 24 arranged in the direction XX so that the weld inspection means 23 are interposed between the first inflatable chamber 21 and the third inflatable chamber 24.

(19) The first and second chambers are spaced apart by a distance d such that when the second chamber 22 faces the constricted central portion 3c of the sleeve, the first chamber 21 faces one end of the sleeve at its terminal portion 3a of smaller thickness. The weld inspection device 23 is then situated outside the sleeve. The weld inspection device 23 is arranged in the longitudinal direction such that when the second chamber 22 is placed facing the opposite end of the sleeve, as shown in FIG. 6, the weld inspection device 23 faces the first end of the sleeve and is thus suitable for inspecting the electro-fusion weld of this first end 3a of the sleeve with a sleeve end of a pipe element in which the sleeve 3 has been inserted and welded, as described below.

(20) Thus, the ends furthest in the longitudinal direction from said second chamber 22 and said weld inspection device 23 are at substantially the same distance as the length L of the sleeve, the three elements 21, 22, 23 being suitable for being included inside said sleeve.

(21) In FIG. 1, a device 20 of the present invention for installing the sleeve is shown inserted in such a manner that when it is fully inflated, the second inflatable chamber 22 presses against the wall of the constricted central portion 3c of the sleeve. The device 20 and the sleeve 3 are thus secured together and can be moved in horizontal translation towards the sleeve-free open end of a pipe element 1.sub.1 until coming into abutment against the end 2a of the lining 2 of the pipe element 1.sub.1, as shown in FIG. 3. At this moment, as shown in FIG. 4, the electrical connectors 21a of the first inflatable chamber 21 face corresponding electrical connectors 4a of the heater wire at one end of the sleeve, as shown in FIGS. 3 and 4. At this stage, the first inflatable chamber 21 can be inflated so as to press against the terminal portion 3a of the sleeve in abutment against the end 2a of the lining, and electricity is injected into the heater wire 4, thereby melting the entire zone 3a of the outer surface 3-2 of the sleeve that is covered by the heater wire, thus enabling the plane of contact between the tubular junction sleeve 3 at its end 3a to be welded by electro-fusion with the end 2a of the lining 2. The first chamber 21 is expanded with pressure serving to guarantee excellent compactness in the plane of melting and also to guarantee the absence of bubbles of air that would be harmful for good leaktightness at the melting surface.

(22) Thereafter, in order to perform the step of inspecting the quality of the weld, the first and second chambers 21 and 22 are deflated and they are moved in translation in the opposite direction until they reach the position shown in FIG. 6, where the weld inspection means 23 are facing the electrically-welded-together ends of the sleeve and of the internal lining of the pipe element 1.sub.1.

(23) Said first and second inflatable chambers 21 and 22 in the deflated position remain relatively close to the walls of the sleeve such that it is easy for the device 20 to be guided in longitudinal translation inside the sleeve. Advantageously, this guidance may be performed manually or by a carriage or by other means for guiding movement in longitudinal translation.

(24) FIGS. 7 and 8 show the steps of inspecting the weld. In a first step, the device 20 is connected once more to the sleeve 3 by inflating the first inflatable chamber 21 and the second chamber 22 facing the constricted central portion 3c and the opposite terminal portion 3a of the sleeve 3. Thereafter, water is injected via the nozzles 23a against the electrically-welded end of the sleeve in the compartment 27 defined by the first chamber 21 and by the fully inflated third chamber 24 containing the means for emitting ultrasound and the weld inspection means 23. Thereafter, ultrasound waves are emitted with the ultrasound sensors 23b for verifying the quality of the weld performed by electro-fusion. Water is injected simultaneously with emitting ultrasound locally in order to provide good transmission for the ultrasound wave. Once the weld has been inspected, it is possible to move the device 20 away in translation after previously deflating all of its inflatable chambers. A pipe element 1.sub.1 is thus made ready for laying, having a tubular junction sleeve 3 at one of its ends forming a male portion ready for being received in the female portion without a tubular junction sleeve of a second pipe element.

(25) FIGS. 10 to 21 show how two unit lengths of lined pipe are assembled together during on-site installation performed on board a laying ship 10 that is fitted with a J-lay tower 10a, as shown in FIG. 1B. A new lined pipe element 1.sub.2 fitted with a tubular sleeve 3 at one of its ends is transferred in conventional manner from the horizontal position to the oblique position corresponding to the angle of inclination of the tower so as subsequently to be positioned on the axis of the terminal pipe element 1.sub.1 at the end of the string being laid. Said pipe element 1.sub.2 that is to be assembled is then moved axially towards the suspended terminal pipe element 1.sub.1. A portion of the sleeve 3 forming a male end of one of the pipe elements penetrates into the female end of the pipe element without a sleeve of the other pipe element that is to be assembled, until the terminal portion 3a of the sleeve comes into contact with the terminal portion 2a of the lining inside the pipe element. Since both pipe elements 3a are close to being vertical, a manipulator arm enables the terminal portion 3a of the sleeve to be inserted completely against the terminal portion of the lining so as to reach the configuration of FIG. 13, in which the two pipe elements 1.sub.1 and 1.sub.2 are held apart by a few millimeters, e.g. by means of said same manipulator arm (not shown), so as to make it possible in conventional manner to perform the welding 5 by means of an orbital welding robot 5a known to the person skilled in the art. The figures show the chamfered steel pipe walls that are a few millimeters apart during welding, and the screen 8 constituted by a mat of ceramic foam limiting the transfer of heat and protecting the thermoplastic sleeve throughout the duration of the welding process. On the right-hand side, the finished weld 5 is shown.

(26) In an embodiment shown in FIGS. 10 to 21, a new terminal pipe element 12 is fitted with a tubular junction sleeve 3 at its bottom end, thereby forming a male end that is lowered towards the female top end of a sleeve-free first pipe element 11 forming the top terminal pipe element of a pipe that is being laid and that is held securely in suspension under a tower.

(27) In a first step, the umbilical 20b is used to lower the device 20 for installing a sleeve so that the first inflatable chamber 21 is positioned facing the terminal portion 3a of the bottom end of the sleeve 3, with the connectors 21a facing the connectors 4a of the heater wire of the terminal portion 3a. In this way, the second inflatable chamber 22 faces the central portion 3c of the sleeve 3, as shown in FIG. 11. At this stage, the second chamber 22 is inflated so as to secure the device 20 and the sleeve 3 together, the device 20 now being lowered together with the pipe element 1.sub.2 until the male end of the sleeve projecting from the end of the pipe element 1.sub.2 is engaged inside the non-lined female portion of the pipe element 1.sub.1, such that the terminal portions 3a of the sleeve 3 come into abutment against the terminal portion 2a of the lining 2 of the pipe element 1.sub.1, as shown in FIG. 13.

(28) At this stage, in order to perform electro-fusion, the first inflatable chamber 21 is inflated with the connectors 21a being connected with the connectors 4a of the heater wire on the inside wall of the sleeve, and electricity is injected into the heater wire so as to perform electro-fusion between the terminal portion 3a of the sleeve 4 and the terminal portion 2a of the lining 2, the electricity being conveyed in a duct inside the umbilical 20b.

(29) Thereafter, in order to inspect the weld, the two chambers 21 and 22 are deflated and the device 20 is raised in longitudinal translation XX so that, the weld inspection means 23 face the previously electro-welded ends 2a-3a, as shown in FIG. 16. At this stage, it is now the first inflatable chamber 21 that faces the central portion 3c of smaller diameter of the sleeve 3, while the second inflatable chamber 22 faces the top terminal portion 3a of the sleeve that has already been electro-welded before lowering the element 1.sub.2 (on the deck of the ship). At this stage, the device 20 is secured once again with the sleeve 3 by inflating both chambers 21 and 22 against the inside wall of the sleeve 3. Thereafter, the third inflatable chamber 24 is expanded so as to make a leaktight wall at the bottom end of the mandrel 20a to define a leaktight compartment 27 between the wall 24 and the first inflatable chamber in the expanded position 21. Before inspecting the weld, water is injected into the compartment 27 via the nozzles 23a. The water is conveyed inside the umbilical 20b. As shown in FIG. 19, the electro-fusion zone is inspected by emitting soundwaves via probes 23b placed against the plastic. Thereafter, the various inflatable walls 21, 22, and 24 can be deflated and the device 20 can be raised for performing a subsequent assembly of a new pipe element.

(30) FIGS. 22 and 23 show an embodiment in which the two chambers 21 and 22 are fitted with electrical connectors 21a and 22a that are placed in such a manner as to enable them to be positioned simultaneously facing electrical connectors 4a at the two ends of a single sleeve 3, the two chambers 21 and 22 together being of a length greater than the length of the sleeve 3 so that the two chambers can coincide with and press against both ends of the sleeve simultaneously.

(31) Alternatively, it is possible to lower a new pipe element 1.sub.2 already fitted with a tubular junction sleeve 3 at its bottom top end, but having its sleeve-free bottom end thus forming a female end of said new pipe element which is lowered towards the male top end of a first pipe element 1.sub.1 fitted with a tubular junction sleeve 3 at its top end, this first pipe element 1.sub.1 forming the top terminal pipe element of a pipe that is being laid and that is suspended securely under a tower.