FR2519325A1 - Carriage for gluing lining to liquefied gas tank - travels on rails fixed by studs to wall anchors and places lining strips on insulating layer - Google Patents

Abstract

The self-propelled carriage (5) places an impervious lining inside a tank for liquified gas, being designed to place parallel strips on a layer of thermo-insulating material (2). It runs on rails (6a,6b) fixed by studs (18) screwing into ferrules welded to the tank wall, being equipped with a reel of lining material together with a dispenser, comb adhesive applicator and a roller. The comb applies adhesive to the contact face of a strip as it comes off the reel and the roller presses the strip onto the insulating layer. The axes of the dispenser, the comb and the roller are all normal to the rails, the leading end of the strip being secured by a traverse which clamps onto the rails. The traverse uses handle actuated spring loaded converging bars to grip the strip.

Description

 Methods and devices for mechanically laying strips of a waterproof coating of a thermal insulation layer of a liquefied gas tank.

 The present invention relates to methods and devices for mechanically placing strips or strips forming a tight covering on a thermal insulation layer of a tank intended to contain: liquefied gases.

 The technical sector of the invention is that of the construction of ship's tanks and terrestrial tanks intended to contain liquefied gases at a temperature above a threshold, which is of the order of −110 C.

We know the technique of construction of metallic tanks or vats intended to contain liquefied iz, called Gas
Membrane System, according to which a thermal insulation layer, which is composed of polyurethane foam or any other equivalent cellular material, is placed against the internal wall of the tank, which is injected in place between the wall and a counter-mold which is fixed on rows of studs which are welded to the inner wall of the tank.

 This technique requires the installation, on the thermal insulation layer, of a waterproof coating intended to prevent the liquid or the gas from being able to penetrate into the cells of the foam.

 This coating constitutes a primary skin or barrier, composed of strips or joint cover strips, of a composite material, known as a "triplex", which is a material composed of a thin sheet of aluminum taken between two fiberglass fabrics, so that the polyurethane foam and the coating form a flexible and waterproof insulating layer, which supports mechanical deformations and expansions, without deteriorating or losing the seal.

 An object of the present invention is to provide a device comprising a self-propelled machine, which moves on rails fixed to the studs which have served to fix the injection molds against the molds of polyurethane and which makes it possible to mechanically install the and successive strips of composite material which overlap to form a continuous sealing skin which is glued against the polyurethane foam.

 Mechanical installation of the strips of composite material poses problems. The composite material must be laid flat, without wrinkling.

 The composite material must be well bonded over its entire surface and remain bonded in place as soon as it has been applied against the visible surface of the insulating layer. Finally, the successive strips must overlap perfectly to form a tight skin.

 The self-propelled laying machine must be able to work in all possible positions, that is to say horizontally, in the ceiling, vertically or in an inclined position.

 The subject of the invention is a method for mechanically laying them, forming part of a waterproof covering, on a layer of thermal insulation made of polyurethane foam, or any equivalent cellular material, which has been placed against the internal face. from the wall of a liquefied gas tank, between said wall and a counter-mold which was fixed to rows of studs which are welded to said wall and which have remained in place in said thermal insulation layer.

The method according to the invention comprises the following steps:
- We screw on the studs pins which pass through the insulating layer;
- Is fixed on each row of sockets a pair of rails located on either side of said row;
- And a covering strip is placed mechanically between two pairs of rails by moving on these rails a machine which carries a strip wound on a reel which is mounted on a reel carried by said machine, which aorta machine, moreover, a comb for gluing the internal face of said strip and a pressure roller which presses against the external face of said strip, which machine comprises a self-propelled carriage provided with rollers which bear on the external rails of said pairs of rails.

 After having placed a first and a second parallel and successive strip which are separated by a vacuum, we remove the pair of rails located in this vacuum and the pins which supported them, we plug the holes left by the pins by means of isolanta plugs and we mechanically poses a joint cover strip between the said ones by moving a self-propelled carriage on two pairs of rails which frame the position of a third strip, which is located immediately after the second le, which self-propelled carriage supports an offset arm which carries a reel carrying a cover strip wound on a reel and which also carries a sizing comb against which the internal face of said strip bears and a pressure roller which bears against the external face of said strip.

 A device according to the invention, for mechanically placing the parallel strips or strips forming a tight covering on a thermal insulation layer of the walls of a tank or of a tank intended to contain liquefied gases, comprises parallel rails which are fixed on pins screwed on studs welded to the walls of the tank and a machine comprising a self-propelled carriage which moves on two rails and which carries a reel of a reel on which one of the said or one of the said strips is wound, a comb gluing of the internal face of said strip or of said strip and at least one roller which bears against the external face of said strip or of said strip and which applies this against the visible face of the thermal insulation layer and the axes of the reel, the glue comb and said rollers are perpendicular to said rails.

 Advantageously, a device according to the invention further comprises a device intended to position and maintain the free end of a strip or a strip, which device comprises a rigid crosspiece which is provided with means which allow to fix it between two pairs of rails perpendicular to this, two rollers parallel to said crossmember, means to separate the rollers from each other in order to engage the free end of a strip or of a strip between the two rollers and means for holding the two rollers applied against each other by pinching said free end.

 The invention results in the mechanized laying of the and of cover strips which constitute a continuous coating forming a primary sealing barrier applied to the visible face of a thermal insulation layer of the walls of a tank or of '' a vessel tank intended to contain liquefied gases whose temperature is higher than approximately - 1100.

 The self-propelled machines according to the invention automatically carry out the operations of unwinding the coils on which the cover strip or strips making up the covering are wound, gluing the internal face of these strip or strips, laying and bonding the them against the visible face of the thermal insulation layer which has been previously injected in place between the wall of the tank and a counter-mold.

 An important advantage of the machines according to the invention is that they move on rails which are fixed on pins screwed onto the threaded studs which have been used for fixing the injection counter molds in place of the thermal insulation layer, which studs remained welded to the wall and embedded in the thermal insulation layer.

 The rails on which the self-propelled machine is deployed are quickly fixed to the studs by means of removable pins which are threaded into the housings left in the insulation layer by the pins for fixing the counter molds and which are screwed onto the studs. After fitting them, remove the rails, unscrew the pins, plug the holes with thermal insulating plugs and there are no longer any parts protruding from the apparent surface of the thermal insulation layer on which can install joint covers to complete the covering. The installation of the joint covers is carried out mechanically like that of the ones placed between the studs, by means of a self-propelled carriage which carries an offset arm.

 The following description refers to the appended drawings which represent, without any limiting character, an embodiment of a device and a machine according to the invention.

 Figure 1 is a half cross section of a liquefied gas transport vessel.

 Figures 2 and 3 are a front and top view of a machine according to the invention.

 Figure 4 is a cross section on a larger scale of a machine according to the invention.

 Figures 5, 6 and 7 are front, top and side views of the rails and rollers carried by the self-propelled carriage.

 Figure 8 is a section of the rail fixing device.

 Figure 9 is an axial section of the sizing comb.

 Figures 10 and II are a front and side view of a self-propelled carriage for the installation of joint covers.

 Figures 12 and 13 are a front and side view of a device for fixing the free end of a strip.

 Figure 14 is a section on XIV-XIV of Figure 13.

 Figure 1 is a very schematic cross section of a liquefied gas transport vessel which allows to expose in a very general way, the problem to be solved and the means used.

 Figure 1 shows a cross section of a tank that occupies the entire width of a ship. This tank is intended to contain liquefied gases maintained at low temperature, for example at a temperature higher than approximately - 550C for a ship or approximately - 1100C for a terrestrial tank.

 The internal walls 1 of the tank comprise a thermal insulation which is composed of an insulation layer 2, on which a primary sealing barrier 3 must be placed forming a continuous and waterproof skin.

 The problem to be solved is that of the mechanical installation of the sealing coating 3. The insulation layer 2 is generally a cellular material of the rigid foam type which resists compression due to hydrostatic thrust.

 According to a process known as the Gas Membrane System, layer 2 is a rigid polyurethane foam which is injected in place between the internal wall of the tank and a counter-mold which is temporarily fixed to this wall by pins screwed onto studs 4, which are welded to the internal wall of the tank. Once the polyurethane foam has been formed and hardened, the counter mold and the pins are removed, the studs 4 remain in place and, to each stud corresponds a circular channel which was occupied by a pin for fixing the counter mold.

 The covering 3 is composed of the and of joint cover strips in a composite material, of the "triplex" type. This material is flexible and the strips are supplied wound on reels.

 A device according to the invention comprises a machine 5 which is mounted on a self-propelled carriage and which carries a reel on which a coil of the composite material is placed. Figure 1 shows the shape of the cross section of a tank and the different positions in which the machine 5 must work, namely in a horizontal position on the floor or under the ceiling, in a vertical position on the side walls and in an inclined position for coating the inclined surfaces of junction between the vertical walls and the floor or the ceiling.

 The self-propelled carriage of machine 5 moves on raceways formed by rails 6 parallel to the longitudinal axis of the ship.

 The cellular material composing the insulating layer 2 does not have sufficient mechanical strength to support the weight of the self-propelled cart and the rails 6 are fixed on pins 18 which pass through the layer 2 and which are screwed onto the studs 4.

 The studs 4 are arranged in rows parallel to the longitudinal axis of the tank and each row carries a pair of parallel and close rails> located on either side of the row of studs for the reasons which will be explained later.

 There is shown in Figure 1 a device 7 which is used to position and maintain the free end of a strip, that is to say the end of the strip by which the machine begins laying the strip.

 The coverings 3 are glued against the internal face of the insulating layer 2 and the adhesion of the adhesive is sufficient to hold a strip in place as soon as it is applied against the surface of the layer 2. However, starting from the laying a le, the edges of the strip must be parallel to the rails, they must be at the same distance from the rail as the ends of the spool placed on the reel of the machine and the strip must be held in place to withstand the unwinding pull of the spool at the start of the unwinding.

 The device 7 is described in detail with reference to Figures 12, 13 and 14.

Figures 2 and 3 are overall views respectively from the front and from above of a machine 5 according to the invention working on a vertical wall. Figure 4 is a cutaway according to
IV-IV of Figure 3 on a larger scale.

 FIGS. 2 and 4 show two pairs of superimposed rails, each pair comprising two close rails 6a, 6b fixed on a support 18.

 The machine 5 comprises a self-propelled carriage composed of a fixed frame 8 which is carried by rollers which roll along the external rails, that is to say against the upper rail 6a of the upper pair and against the lower rail 6b of the lower pair.

 Figures 5, 6 and 7 show, on a larger scale, the rails and the rollers of the carriage in respective front, top and side views.

 The chassis 8 is suspended from two rollers 9a, 9b, idle on their axis, which roll on top of the upper rail 6a, in the case where the machine works in a vertical or inclined position.

 The chassis 8 comprises two pairs of grooved rollers 10a, 10b and Ila, 11b, each pair being mounted on the same transverse axle. These rollers cooperate with the two outer rails of each pair, that is to say the two rails furthest from each other.

These rollers roll against the external flanks of the rails, that is to say against the flanks of the rails which are opposite to the visible face of the insulation layer 2 on which the coating is to be bonded.

 The rollers 10a, 10b are mounted on a driving axle 12 which is driven by a motore1sacteur group 13, equipped with a variable speed motor or a speed variator which makes it possible to vary the speed of movement of the carriage between 0 and 3.5 m / min, the normal laying speed being around 1.5 m / min. The two rollers Ila and 11b are mounted on an axle 16 which can be idle or else rotated by means of a chain transmission or any other equivalent transmission device driven by the gearmotor group 13.

The self-propelled carriage further comprises two pairs of cylindrical counter rollers 14a, 14b and 15a, 15b, which are pressed against the internal flank of the two external rails
The rollers 14b and 15b, which bear against the lower rail 6b, are mounted ~ on an articulated arm 17 provided with a self-locking articulation> of the grasshopper type with lever, which allows them to be released down to put by placing the machine on the rails, as shown in: dotted lines in FIG. 7.

 This set of motorized rollers, counter-rollers and suspension rollers allows the same machine to work in all the positions shown in FIG. 1.

 The presence of counter-rollers 14a, 14b, 15a, 15b which roll on the internal flanks of the rails requires that these flanks be entirely free. This is the reason why pairs of rails 6a, 6b are used which are mounted symmetrically on either side of a row of support 18 fixed on the studs 4 and offset laterally with respect to these supports, so that the rollers can roll on the internal sides of the rails without the risk of abutting against the rail supports.

 FIG. 4 is a cross-section, on a larger scale, passing through the off-hook line IV-IV of FIG. 3, that is to say passing through the axle 12, through the axis of the counter-rollers 14a and 14b and by the axis of a jack 61.

 It can be seen in this FIG. 4 that the chassis 8 of the machine has a gantry-shaped cross section, which carries a fixed upper counter-roller 14a and a lower counter-roller 14b mounted on a pivoting support 1 # 7, of a known type, comprising articulated links 17a, 17b and a handle 17c which make it possible to block the counter-roller 14b in the position pressed against the lower rail 6b and to release it towards the outside when the machine is engaged on the rails.

 The assembly formed by the geared motor group 13, the drive axle 12 and the drive rollers 10a, 10b, is mounted on a movable frame 58 which is carried by ball bushings 59 sliding on guide rods 60 which are fixed to the frame 8 and which are perpendicular to the surface to be coated.

 The guide rods 60 are four in number connected two by two to the rods of two cylinders 61 which are fixed to the chassis 8 and which make it possible to move the movable frame 58 to move the axle 12 and the drive rollers 10a, 10b for removal and installation of the machine on the rails.

 The machine comprises a second movable chassis 58 carrying the axle 16, which second chassis comprises an identical movement mechanism. The cylinders 61 make it possible to press the drive rollers and the counter rollers against the rails, whatever the position of the machine.

One of the two rollers on each driving axle is mounted # sliding: on the axle to make up for the differences in the center of the rails
A freewheel drive 62 is interposed between the output of the geared motor group 13 and the shaft 12. This freewheel allows the machine to be brought back by hand and at high speed to the end of the rails after the laying of a strip.

 your Figure 8 is a section on a larger scale through one of the studs 4 welded to the metal wall 1 of a tank or a tank. We see in this figure one of the supports 18 which consists of a pin which is engaged through the layer of polyurethane foam 2. The pin 18 comprises, at the inner end, a socket which is screwed onto the threaded stud 4. It comprises an external threaded end 18a, on which a plate 19 is engaged, two edges of which are welded to two tubes 6a, 6b which form a pair of rails.

 The plate 19 has an ovalized hole 20 which is elongated in the direction perpendicular to the rails, so that it allows adjustment of the rod. threaded with respect to the plate to take account of a possible misalignment of the g. : jons 4. Two nuts 21, which are screwed onto the threaded rod on either side of the plate 19, make it possible to adjust the distance between the rails and the external face of the layer 2 and the position of the plate 19 by relative to the threaded rod 18a.

 It is clearly seen in Figure 8 that, thanks to the fact that pairs of rails 6a> 6b are offset relative to the supports 18, these do not interfere with the rollers 14a and 11a rolling on the inner and outer sides of the external rail 6a of each pair.

 Returning to FIGS. 2 and 3, it can be seen that the self-propelled carriage 8 carries a reel 22 whose axis is situated in a plane parallel to that of the rails and perpendicular to them, on which a coil 23 with a hollow axis is placed. on which is wound a strip 24 of composite material forming the covering 3. There is shown in Figures 2 and 3 a strip 24 during installation. The machine 5 may include one or more rollers or counter-rollers 25 for guiding the web. The reel 22 has a braking device that can be adjusted in order to keep the web 24 taut. It comprises a sizing device 26 of the internal face of the web intended to deposit thereon beads of glue.

 The machine 5 carries one or more pressure rollers 27 made of flexible foam, the axes of which are parallel to that of the reel 23. These rollers press against the external face of the strip 24 and apply the latter against the visible face of the insulating layer 2 by crushing the beads of glue so that it extends evenly over the entire surface of the strip.

 The machine 5 finally carries an electrical box 28 containing the circuits and the electrical devices supplying the geared motor group 13.

 The machine 5 can carry, in addition, a device for transversely cutting the.

 The development tests of a machine according to the invention have shown that the gluing problem was difficult to solve.

 The adhesive used has two components: a polymerizable resin> for example an epoxy resin, to which a hardener is mixed before applying it.

 FIG. 9 represents a general diagram of the sizing device used. The resin and the hardener are prepared in two feeding groups independent of the machine where they are compressed under very high pressure of the order of several hundred bars. Each of the two booster groups is connected by a high pressure hose 29, 29a, to a mixing chamber 30. The length of the hoses 29 and 29a corresponds to the stroke of the self-propelled machine 5. The hoses are heated by electrical resistors .

 The chamber 30 communicates with a diffuser 31. The chamber 30 and the diffuser 31 are carried by the machine 5.

 The sizing device is a cylindrical comb 26 which extends transversely over the entire width of the machine. The comb 26 is removable so that it can be cleaned. it is closed at both ends. it comprises, along a generator which comes into contact with the internal face of the web 24, a row of perforations 33 extending over a length equal to the width of the islands. For example, the strips are 740 mm in width and the cylinder 26 comprises a row of 148 holes of 2 mm in diameter spaced 5 mm from axis to axis.

The diameter of the holes can vary between 1.5 and 2.5 mm. The spacing between holes can vary between 4 mm and 6 mm.

 A bead of glue which is applied against the internal face of the strip is extruded under pressure through each hole.

 After several tests, it has been demonstrated that in order to obtain a homogeneous distribution over the entire surface of the strip of glue which is very viscous, it was necessary to use a comb 26 comprising numerous closely spaced perforations and that it was also necessary to bring the glue of the comb 26 at several points distributed over the length of the tube.

 Good results have been obtained by using a comb 26 comprising five glue inlet orifices which are connected by five.

high pressure hoses 32 to a five outlet diffuser 31,
The comb 26 advantageously consists of a cylindrical bar pierced with longitudinal channels which communicate with the injection orifices 33 and with the hoses 32. The generatrix of the comb carrying the perforations 33 advantageously has a slight flat.

 Once the 24 have been placed between the rows of studs 4, it is necessary to place strips 34 forming joint covers between the two.

 Figures 10 and 11 are a front view and a sectional view along XX of a machine 5 which comprises, on the same self-propelled carriage, a device for placing the 24 and on a remote arm 35 a device for placing the covers - seals 34.

FIG. 10 represents a step in which the les are raised and where the les 24a, 24b are laid successively and where a strip 24c is being laid by the machine 5,
The self-propelled carriage of the machine 5 rolls on the two external rails 6a and 6b located on either side of the strip 24c during installation.

 Before starting the installation of the 24c, we removed the two rails located between the 24a and 24b and the pins supporting these rails and we plugged with a thermal insulating plug the holes left by the pins. The caps are made of polyurethane foam as the insulation layer.

 The arm 35 is mounted on the self-propelled carriage of the machine 5 and it extends downwards or: the rib over a length slightly greater than the width of a strip. Like the machine 5r, the carriage 35 carries a reel 36 on which is placed a reel on which the strip of cover strip 34 is wound, a perforated comb 37 for gluing the internal face of the strip 34 and a pressure roller 38 which applies the strip 34 to the external face of the insulation layer 2 by covering the edges of the two 24a and 24b.

 As a variant, the offset arm 35 carrying the reel 36, the sizing comb 37 and the pressure roller 38 can be mounted on a self-propelled carriage which rolls on the rails 6a and 6b placed on either side of the web 24c, but which is independent of the carriage carrying the laying devices for the strip 24c because it may be easier to separate the two operations for laying the strip 24c and the joint cover 34.

 Figures 12 and 13 show a front view and an elevational view of a device 7 for positioning and holding in place the end of a strip before starting to lay it.

 We see in Figure 12 the two pairs of rails 6a, 6b framing the area on which a strip must be laid.

 The device 7 comprises a rigid crosspiece 40 which extends perpendicular to the direction of the rails, between the two pairs of rails. The crosspiece 40 is for example a profile having a U-shaped cross section or any other equivalent profile.

 At one end of the crosspiece 40, for example at the upper end, are fixed a profile 41 and a plate 42 perpendicular to the crosspiece 40 which extend on either side thereof and which carry two support pieces 43a, 43b, located on either side of the crosspiece 40. The support pieces 43a, 43b have a lower face inclined at 450 which bears on the internal side of the rail 6a, while the internal face of the plate 42 bears against the external flank of the rail 6a as seen in FIG. 12.

 The upper end of the crosspiece 40 carries a third support point 44 which occupies a longitudinal position intermediate between the support points 43a and 43b and which bears against the rail 6b of the pair of upper rail.

 The fulcrum 44 is mounted on a known self-locking device 45, of the toggle joint type, comprising a handle and a system of connecting rods> represented by their articulations, which make it possible to pivot the fulcrum of the position shown in solid lines where it is locked against the rail 6b in the position shown in dotted lines.

 The lower end of the crosspiece 40 carries a fixing device composed of a plate 46 which is mounted on a threaded rod 47 on which a nut 48 is screwed provided with a handle 48a which allows the plate 46 to be pivoted a quarter turn to engage it behind the lower rails oa, 6b and to lock it in this position.

 The assembly formed by the plate 46 and by the three triangle support points 43a, 43b and 44 makes it possible to fix the crosspiece 40 to the rails in a position exactly perpendicular thereto.

 The crosspiece 40 carries two rollers 49a, 49b whose axis is parallel to the crosspiece 40. The roller 49a is fixed. The roller 49b is movable in the plane perpendicular to the external face of the layer 2. The roller 49b is held in abutment against the roller 49a by two springs 50a, 50b bearing on the crosspiece 40.

A handle 51 is fixed to the roller 49b and this handle makes it possible to separate the roller 49b from the roller 49a to engage the free end of an it between the two rollers. When the tensile force is released on the handle 51, the web is kept pinched between the two rollers by the thrust of the two springs 50a and 50b. The handle 51 passes freely through two holes 52a, 52b drilled in the crosspiece 40. These two holes are extended laterally by an ovalized slot 53a, 53b and the handle 51 has two shoulders 54a, 54b.

 When an operator has pulled the handle 51 back to spread the roller 49b, he can slightly rotate the handle and the roller 49b around the axis of the latter, so that the ends 55a, 55b of the handle which have a smaller diameter, engage in the slots 53a, 53b and the shoulders 54a, 54b bear on the edges of these slots as shown in dotted lines in Figure 14 which is a cross section along XlV-XlV in Figure 13.

 The handle 51 is then held in this position by the pushing of the springs 50a, 50b, which let the operator have their hands free to engage the end between the rollers 49a, 49b and then release the handle.

 The rollers 49a, 49b are carried by two plates 56a, 56b fixed to the crosspiece 40. The two ends of the roller 49a are fixed to the two plates while the two ends of the roller 49b slide in two ovalized holes 57. The length of the rollers 49a , 49b is very slightly greater than the width of a strip which is normalized.

 The positioning of the rollers relative to the crosspiece 40 is such that the edges of the web going from the end which is pinched between the two rollers to the reel 23 which is mounted on the reel of the machine, are in parallel planes to the rails and perpendicular to the axis of the spool, so that the them do not risk making folds.

 Of course, a device of the same type can be used to position and maintain the ends of the joint covers 34.

 In this case, the length of the rollers 49a, 49b corresponds to the width of the joint covers, the crosspiece 40 is offset laterally and the rollers 49a, 49b are fixed to the extension which is offset relative to the rails.

 The pressure rollers 27 and 38 are pressed against the internal face of the web by jacks which are supplied with compressed air, the pressure of which can be varied to adjust the pressure of the rollers against the strips.

Claims (11)

 1. Device for mechanically placing the parallel strips or bands forming a tight covering on a thermal insulation layer (2) of a tank or a tank intended to contain liquefied gases, characterized in that it comprises parallel rails (6) which are fixed on pins (18) screwed onto studs (4) welded to the walls of the tank and a machine (5) comprising a self-propelled carriage which moves on two rails and which carries a reel (22) a coil (23), on which one of said one or more bands is wound a comb (26) for gluing the internal face of said one or more bands and at least one roller (27) which bears against the external face of said strip and which applies this against the visible face of said thermal insulation layer (2) and the axes of said reel (27), of the glue comb (26) and of said rollers (27) are perpendicular to said rails (6).  2. Device according to claim 1, Çaractérisé in that it further comprises a device (7) intended to position and maintain the free end of a strip or a strip, which device comprises a rigid crosspiece (40) which is provided with means which allow it to be fixed between two pairs of rails (6a, 6b) perpendicular thereto, two rollers (49a, 49b) parallel to said cross member, means for spreading said rollers one on the other to engage the free end of a strip or a strip between the two rollers and means for holding the two rollers applied against each other by pinching said free end.  3. Device according to any one of claims 1 and 2, characterized in that said rails comprise pairs of rails, each pair being formed of two rails (6a, 6b), parallel and close together, which quisont supported by pins comprising sleeves (18) which are screwed onto a row of threaded studs (4), welded to said wall (1) and, when said machine (5) lays a strip located between two pairs of adjacent rails, the rollers of the self-propelled carriage roll on the outer rails of each pair.  4. Device according to claim 3, characterized in that said self-propelled carriage comprises a pair of rollers (9a, 9b) which roll on top of the upper rail (6a) when the machine works in a vertical or inclined position, motor rollers ( 10a, 10b, lita, 11b) which roll on the external sides of the external rails and counter-rollers (14a, 14b, 15a, 15b) which roll on the internal sides of the external rails.  5. Device according to claim 4, characterized in that the two counter-rollers (14a, 15a), which roll against the sides of an external rail are fixed and two counter-rollers which roll against the sides of the other rail external are mounted on pivoting supports (1J) provided with a self-locking articulation which allows to release these last two counter-rollers to engage the carriage on the rails.  6. Device according to any one of claims 4 and 5, characterized in that the machine chassis comprises a fixed chassis (8), in the form of a portiquewportant said counter-rollers (l4a, 14b, 15a, 15b) at l inside of which are two movable chassis (58) which are each mounted on ball bushings (59) which slide on guide rods (60) which are carried by said fixed chassis and which are perpendicular to the surface to be coated, which sockets are moved by jacks (61) and one of said movable chassis (58) carries said motor-reduction unit (13), and a drive axle (12) on which are mounted two drive rollers (] Oa, 10b) , while the other movable frame carries the other axle (16) on which are mounted two other rollers (1a, 11b).  7. Device according to any one of claims 1 to 6, characterized in that said sizing comb is a cylinder which has a row of fine perforations along a generatrix against which the web in the course of laying rests and which has several glue inlets which are distributed over the length of the cylinder and which are connected by hoses (32) to a diffuser (31) which receives the glue coming from a mixing chamber (30) carried by the machine in which takes place the mixture between a polymerizable resin and a hardener.  8. Device according to any one of claims 1 to 7, characterized in that it further comprises a device intended to lay narrower strips (34 forming joint covers between a first strip and a second strip ( 24a, 24b) already installed, which device comprises an arm (35) which carries a reel reel (36), a sizing comb (37) and at least one pressure roller (38) with parallel axes, which arm (35 ) is supported by a self-propelled carriage (5); which rolls on two rails framing the position of a third strip (24c) which is located immediately after the two les (24a, 24b) which must be joined by said joint cover.  9. Device according to claim 2, characterized in that said device (7) intended to keep the free end of a strip or a joint cover comprises a rigid crosspiece (40) which is fixed perpendicularly between two pairs of rails ( 6a, 6b) by means of a plate (46) mounted on a threaded rod (47), which is fixed to one end of said crosspiece by a nut (48), said plate bearing behind a pair of rails and by means three support points (43a, 43b, 44) arranged in a triangle at the other end of said crosspiece which bear on the second pair of rails and one of the two rollers (49b) is movable and is mounted on a handle (51) which passes through two orifices (52a, 52b) which are drilled in said handle and which are extended by two ovalized slots (53a, 53b) and said device comprises two springs (50a, 50b) located between said movable roller (49b ) and said crosspiece (48).  10. Method for mechanically laying strips forming part of a waterproof covering, on a layer (2) of thermal insulation made of polyurethane foam or any other equivalent cellular material which has been injected in place against the internal face of the wall (1) a reservoir or a tank intended to contain liquefied gases, between said wall (1) and a counter-mold fixed to rows of studs (4) welded to said wall, characterized in that  - Screws on said studs pins (18), which pass through the insulating layer;  - Is fixed on each row of sockets a pair of rails (6a, 6b) located on either side of said row; ;  - And mechanically laying a strip (24) of coating between two pairs of rails by moving on these rails a machine which carries a strip (24) wound on a reel (23) which is mounted on a reel (22) carried by said machine (5), which machine further carries a sizing comb (25) of the internal face of said web and a pressure roller (27) which presses against the external face of said eye, which machine comprises a self-propelled carriage provided rollers (9a, 9b, 10a, 10b, 1ta, Ilb, 14a, 14b, 15a, 15b) which bear on the external rails (6a, 6b) of said pairs of rails.  11. The method of claim 10 for placing, moreover, narrower strips (34) forming joint covers between two of said strips (24a, 24b), characterized in that. that we first put a first and a second successive parallel strips (24a, 24b) which are separated by a vacuum, we remove the pair of rails located in this vacuum and the pins (18) supporting these, we plugs the holes left by said pins with the help of insulating plugs and the said joint strip is mechanically placed by moving a self-propelled carriage on two pairs of rails framing the position of a third strip (24c) which is located immediately after the second strip , which self-propelled carriage (5) supports an offset arm (35) which carries a reel (36) on which is placed a reel carrying said wound tape and which further carries a sizing comb (37), against which # # is supported on the internal face of said strip and a pressure roller (38) which is pressed against the external face of said strip (34).