DE102017207254A1 - Abdichtkupplung between at least two mutually storable pipes of an electrolysis plant and use - Google Patents

Abstract

The invention relates to pipe couplings set up for use in electrolysis plants. In particular, the invention relates to a Abdichtkupplung (10) between at least two mutually storable pipes (11, 13) of an electrolysis plant, wherein the Abdichtkupplung formed on abutting lateral surfaces (11.3, 13.1), wherein the tubes (11, 13) relative to each other in axial Direction into one another sealingly on a sealing surface (11.31) with independent of an axial relative movement or relative position of the tubes size constant surface area are releasable. This allows in addition to high reliability and simplification of the assembly process. Furthermore, the invention relates to the use of a tube-in-tube arrangement as a heat-expansion-tolerant pipe coupling in an electrolysis plant.

Description

The invention relates to sealing devices on or between two tubes to be stored with a certain axial play relative to each other. Furthermore, the invention relates to the use of a tube-in-tube arrangement for providing such a sealing device. In particular, the invention relates to a sealing coupling according to the preamble of claim 1.

Sealing tube-in-tube connections are required in particular in electrolysis systems. There are electrolysis systems for the production of chlorine, hydrogen or caustic soda. The respective substances are thereby obtained within cells of the electrolysis plants, and must be promoted for further use out of the cells. Usually, collecting ducts made of metal are used, which produce a connection to the respective cell via standpipes made of plastics.

Due to the tight space and cost pressure, the connection between the collecting ducts and the standpipe must, on the one hand, enable fast and reliable assembly and, on the other hand, a tight connection over the entire service life of the cell. In particular, the following factors can be a hindrance to a good seal: different expansions in the collecting channel and standpipe, in particular at temperatures of up to almost 100 ° C; greater manufacturing tolerances in plastic compared to metal. In this case, the aim is in particular for a universal connection with different geometries of the stanchions.

In order to meet as many of these requirements as possible, e.g. a conical nozzle provided on the collecting channel, on which the standpipe can be pushed. Due to an axial preload, a good tightness can be achieved with a simple assembly. However, it has been shown that this type of coupling brings disadvantages, in particular with temperature fluctuations. At elevated temperatures, the plastic standpipe expands more than the metallic components of the cell, increasing the axial preload. In some cases, it can not be avoided that bending of the standpipe occurs from a critical preload. This entails the risk of undesirable contact between the standpipe and the electrode, with the result that the electrode is undersupplied with electrolyte and / or the pressure on the membrane of the system is too high. However, associated malfunction and shortened life should be avoided.

The object of the invention is to provide a device, which with pipes to be stored with some axial play relative to each other to each other, a seal with good reliability can be ensured. In particular, it is an object to provide a coupling which can ensure reliable sealing even with regard to thermally induced relative movements or with different materials of the coupling elements, in particular with high operational reliability over a long service life.

This object is achieved by a Abdichtkupplung between at least two mutually storable / mounted pipes of an electrolysis, in particular between at least one connected to a cell of the electrolysis plant standpipe and at least one manifold, wherein the Abdichtkupplung is formed on at least one pair of tubes of the tubes against abutting lateral surfaces , wherein the tubes of the (respective) pair of tubes relative to each other in the axial direction sealingly abutted against each other on a sealing surface with independent of an axial relative movement or relative position of the tubes size constant surface area / are releasable. This provides a comparatively exactly predefinable surface pressure or sealing effect. It can be ensured that the conditions and thus the surface pressure do not change any more or not perceptibly locally at the sealing surface during relative movements. A quasi-static sealing condition can be ensured.

The axial floating allows relative displacement, e.g. with temperature fluctuations due to different thermal expansion coefficients. This makes it possible to minimize the stresses in the respective tube. In this case, the sealing effect can be ensured in particular by elastic expansion of the outer tube (standpipe) and the associated surface pressure.

In particular, it can be ensured that stresses in the respective tube, especially in the standpipe, remain the same during relative movements, so that buckling of the tube (FIG. z .B. 1.2 m in length) can be prevented. The (biasing) forces in the respective tube can be ensured independently of a respective relative axial position or at least kept approximately constant.

The sealing surface can remain consistently large even with a relative movement. The sealing surface can remain arranged at a relative movement exactly at the same axial position. Both effects have an advantageous effect on the reliability and the design of the seal.

For example, it is entirely possible to dispense with a conicity on the tubes. This also minimizes the risk of wedging or kinking at particularly high stresses. Disproportionately increasing (biasing) forces can be avoided. Rather, a compound / coupling can be realized with independent of the operating conditions constant axial preload on the pipes. The size (the surface area) of the sealing surface can remain constant, and thus also the surface pressure and the acting contact forces. The sealing effect can be predefined in a relatively exact manner, regardless of positional tolerances or elongations. Longitudinal expansions can be compensated for without significant increase in axial stresses in the respective tube.

In particular, a reliable, reliable coupling between collecting channel a (collecting channel) and a standpipe (discharge pipe) in the NaCl and water electrolysis can be realized, regardless of thermal strains, stand pipe tolerances or geometric shapes.

As tubes, e.g. Pipes or nozzles are used for conveying fluids. Particularly suitable materials are polymers, especially PTFE, and metallic formed tubes or sheets. At least one of the tubes may be formed as a standpipe in a cell of an electrolysis system. The standpipe is expediently made of plastic or the polymer PTFE. The standpipe has e.g. a length in the range of 1 to 1.5m.

As a standpipe, e.g. a PTFE tube with a diameter in the range of 30mm and a length in the range of 1 to 1.5m be provided. This also results in a certain elasticity or flexibility. Depending on how flexible the material of the tube is, the tube can also be referred to as a tube. In a cylindrical, round tube, the Abdichtkupplung can be realized in a particularly simple manner. However, deviating geometries can also be realized.

At least one of the tubes may be formed as a manifold in a cell of an electrolysis system. The manifold is suitably made of a metallic material or sheet metal.

The one pipe, in particular standpipe, may be fastened to a flange in the lower part of a cell of an electrolysis plant. In this arrangement of Abdichtkupplung results from thermal expansion during operation of the cell (about 90 ° C), a relative movement between standpipe (in particular made of plastics) and cell (especially metal).

The sealing effect or the surface pressure of the fit can be ensured according to the invention by different measures, in particular by different tube wall thicknesses, by different moduli of elasticity, by different deformation properties, by anisotropic deformation properties (in particular with respect to tensile and compressive forces).

It has been found that the lowest possible surface pressures are advantageous for the goal of avoiding bending or kinking of pipes. Nevertheless, adequate sealing effect should be able to be ensured with good reliability. The sealing coupling can therefore be optimized with regard to the lowest possible surface pressure, in particular in such a way that a lower threshold value for the sealing effect specifies a minimum surface pressure.

It can be ensured that during a relative movement only an elastic deformation of the (respective) tube takes place. The tubes of the respective tube pairing are dimensioned such that during relative movements a deformation takes place exclusively in the elastic region. This can ensure a long service life and high reliability. The extent to which the respective fit has to be designed can be determined on the basis of material tables and stress-strain diagrams, depending on the selected material pairings.

Alternatively, the inner tube (in particular collecting tube) can be forced partly also a plastic deformation, especially during initial assembly. This can ensure particularly high reliability with certain material pairings. It can be ensured by selecting the appropriate tolerance or adequate oversize that the outer tube (in particular standpipe) is deformed in any case only in the elastic range.

According to one embodiment, the lateral surface of the inner tube of the (respective) pair of tubes at least one predefined axial position to a radially outward thickening with sealing function, which defines the sealing surface at least partially at the predefined axial position, wherein the radial thickening independent of an axial relative movement or relative position Pipes size constants, constant surface area of the sealing surface defined. This also provides a very robust, simple construction.

The radial thickening, in particular radial expansion can be, for example, in the range of 1 to 3% of the diameter of the tube. It has been shown that such a comparatively small thickening already provides very good operational reliability, and can be realized with a large number of material pairings. If manufacturing tolerances can not be maintained particularly accurately, it makes sense to choose the radial thickening rather slightly larger, that is to say in the range of 2 to 3% or even greater. It can not be ruled out that radial thickening of up to 5% is particularly expedient for certain applications.

The radial thickening may optionally be provided by material of the inner tube or by a material deviating therefrom or by an element attached thereto. It is advantageous if tube and radial thickening are integral. This provides good robustness, an exactly predetermined elongation behavior, as well as effective sealing.

According to one embodiment, the constant, constant-size sealing surface is circumferential, in particular completely circumferential. On the outer tube, a geometrically corresponding sealing surface portion may be provided. This fully ensures the same sealing effect, and bending moments on the pipes can be avoided.

According to one embodiment, the constant, constant-size sealing surface is rotationally symmetrical. As a result, the forces acting can be distributed rotationally symmetrical.

According to one embodiment, the constant, constant-size sealing surface is linear or has in the axial direction a width less than 20% of the diameter of the inner tube, in particular a fully constant width. In this way, an effective seal can be made, in particular with comparatively large radial surface pressure forces (large radial pressure with comparatively small axial forces) and with only comparatively small axial frictional resistance. It can be realized as small a seal as possible to a line contact seal. In this case, depending on the selected material pairing, the sealing surface can be designed or dimensioned such that a radial surface pressure at the radial thickening remains largely constant independently of the relative axial position.

Depending on the application, a compromise between thickness and width of the radial thickening can be chosen. A greater thickness causes higher contact pressures, but requires greater axial forces for the length compensation. A greater width can improve the sealing effect without increasing the contact forces (surface pressure), but also requires greater axial forces in many material combinations, and also requires more installation space. An optimal compromise can therefore be found individually for each application.

According to one embodiment, the radial thickening on the lateral surface is symmetrical with respect to a cross-sectional plane orthogonal to the longitudinal axis of the inner tube. As a result, a seal with symmetrical force distribution can be provided in a particularly effective manner.

According to one embodiment, the radial thickening on the lateral surface is formed by a wall of the tube, in particular by a plastic deformation. As a result, high reliability and good strength can be realized. In addition, the number of components of the Abdichtkupplung is reduced, in particular to the minimum possible number of two components, namely the two tubes. Separate sealing materials are not required.

According to one embodiment, the radial thickening is formed by a widening of the tube. This also provides high reliability and good strength.

According to one embodiment, the radial thickening is arranged at a distance of at least 1 mm or 2% of the diameter of the inner tube from a free end of the inner tube. This avoids edge effects, especially unwanted deviations from a desired arrangement, and can ensure good strength and tight tolerances.

According to one embodiment, the radial thickening is arranged at a distance of at most 2 mm or 20% of the diameter of the inner tube from a free end of the inner tube. This not least provides a good compromise between space requirements and accuracy of the arrangement or with respect to smallest possible manufacturing tolerances of the radial thickening.

According to one embodiment, the radial thickening in the radial direction is greater than 2% of the diameter of the outer tube. As a result, a sufficiently high surface pressure can be ensured even with a comparatively soft, elastic, flexible outer tube. For example, the radial thickening in the axial direction is less than 30% of the diameter of the inner tube. This also provides advantages in terms of space requirements.

In particular, the radial thickening has a flank axially in front of and behind the sealing surface continuous contour, in particular symmetrically in front of and behind the sealing surface tapered flanks.

In one embodiment, the radial thickening in the radial direction is less than 15% of the diameter of the outer tube. This also allows integration of the radial thickening in the pipe wall, with various materials.

According to one embodiment, the radial thickening in the axial direction is overlapped by the outer tube, in particular by at least 15 or 20% of the diameter of the outer tube. This not least allows a decoupling of stress conditions at a free end of the outer tube. Furthermore, a certain angular tolerance can also be ensured. In this way, a certain positional tolerance in the axial direction can be ensured.

According to one embodiment, a free end of the outer tube is arranged / arranged freely spaced from the lateral surface of the inner tube. This can promote relative movements and help to minimize tension, especially tension due to angled, not 100% exactly axial displacement.

According to one embodiment, the tubes of the tube pair are dimensioned such that the Abdichtkupplung is formed by a frictional axially tolerant tube-in-tube arrangement for sealing caused by elastic deformation frictional connection between the sealing surface and a corresponding sealing surface portion of the outer tube. This results in the aforementioned advantages.

It would be desirable to have the lowest possible axial forces, as this minimizes the risk of buckling of the pipe. The axial relative movement causes or causes an elastic deformation of the tube, for which purpose a certain minimum axial force must be exceeded, depending on the material and the size ratios of the tubes. It is expected that for many applications the lowest possible coefficient of friction is advantageous, so that the axial force to be applied is defined essentially by the forces to be applied for elastic deformation. PTFE material has an advantageous low coefficient of friction. The coefficients of friction for sliding friction and static friction can advantageously both be as low as possible, in particular in order to ensure a relative movement as independent as possible of static friction can.

The sealing coupling may be designed such that axial forces occurring during relative movement are smaller than buckling forces which cause kinking of the respective tube, in particular with an individually configurable safety factor, e.g. in the range of 1.5, 2 or 2.5, or significantly larger.

According to one embodiment, a tube of the tube pair, in particular the inner tube, or at least the free end of metal, and the other tube of the tube pair or at least the free end is made of plastic, in particular PTFE. In this embodiment, the Abdichtkupplung can be used for example in an electrolysis system.

According to one embodiment, the sealing coupling is arranged for axial relative movements in the range of 5 to 15 mm or 20 to 40% of the diameter of the inner tube, in particular 10 mm or 30% of the diameter of the inner tube. This results in the aforementioned advantages.

The aforementioned object is achieved by a Abdichtkupplung between at least two mutually mounted pipes of an electrolysis plant, in particular by a Abdichtkupplung described above, made by coupling two pipes at the free ends of abutting lateral surfaces and by displacing the tubes relative to each other by means of the coupling , wherein the floating bearing and sealing at least one predefined axial position of the inner tube to a sealing surface, in particular to a radial thickening outwards, such that regardless of an axial relative movement or relative position of the tubes, the sealing surface dimensioned constant size or remains unchanged unchanged, so that sealing mutual abutment of the lateral surfaces is ensured at least approximately constant axial preload force even with relative axial displacement of the tubes to each other. This provides the aforementioned advantages.

According to one embodiment, the Abdichtkupplung is set up or designed as a self-locking, axially detached heat-expansion-tolerant coupling, in particular with a coefficient of thermal expansion of the outer tube greater than a coefficient of thermal expansion of the inner tube. This arrangement has the advantage that the radial thickening can have an at least approximately constant geometry even with temperature differences, and the outer tube can shift axially, in particular more easily with increasing temperature stresses. The coupling is self-locking. Even with particularly high temperature fluctuations, the relative movement is made possible, advantageously in the degree with less resistance, in which also decreases the strength or buckling force or kink resistance of the outer tube.

The aforementioned object is achieved according to the invention by using a tube-in-tube arrangement for forming a sealing coupling, in particular a previously described Abdichtkupplung, between at least one tube made of metal and at least one tube made of plastic in an electrolysis system, in particular an internally overlapping manifold made of metal and an outer overlapping standpipe made of plastic, wherein the inner tube by means of at least one formed at a predefined axial position on the inner tube sealing surface, in particular on a radial thickening outward, with constant independent of an axial relative motion, constant-size surface area on a geometrically corresponding sealing surface portion of the overlapping outer tube in axial elasticity caused by elastic deformation of the outer tube axial adhesion, in particular is sealed heat expansion tolerant. This provides the aforementioned advantages. The thermal expansion tolerance of the coupling can be ensured, for example, in a range of room temperature to over 100 ° C, in particular to about 150 ° C.

The invention also relates to an electrolysis system with a previously described Abdichtkupplung, in particular in arrangement or training between at least one standpipe and at least one manifold.

• 1A, 1B jeweils in geschnittener Seitenansicht eine vorbekannte, konische Rohr-in-Rohr-Anordnung gemäß dem Stand der Technik;
• 2A, 2B jeweils in geschnittener Seitenansicht eine Abdichtkupplung gemäß einem Ausführungsbeispiel mit einer nicht-konischen Rohr-in-Rohr-Anordnung;
• 3 einen Vergleich der Belastungen bei einer vorbekannten Rohr-in-Rohr-Anordnung gemäß dem Stand der Technik und bei einer Abdichtkupplung gemäß einem Ausführungsbeispiel, in Abhängigkeit von einem Ausmaß einer axialen Relativbewegung; und
• 4A, 4B in einer Seitenansicht und in einer Schnittansicht gemäß der strichpunktierten Schnittlinie einen Teil einer Elektrolyseanlage mit einer Zelle mit einer darin verbauten Abdichtkupplung gemäß einem Ausführungsbeispiel.

Further features and advantages of the invention will become apparent from the following description of at least one embodiment with reference to figures, and from the figures themselves. Reference numerals which are not explicitly described with respect to a single figure, reference is made to the other figures. In each case show in a schematic representation

• 1A . 1B each in a sectional side view of a prior art, conical tube-in-tube arrangement according to the prior art;
• 2A . 2 B each in a sectional side view of a sealing coupling according to an embodiment with a non-conical tube-in-tube arrangement;
• 3 a comparison of the loads in a prior art pipe-in-pipe arrangement according to the prior art and in a Abdichtkupplung according to an embodiment, in dependence on a degree of axial relative movement; and
• 4A . 4B in a side view and in a sectional view along the dash-dotted line section of a part of an electrolysis plant with a cell with a sealing coupling installed therein according to an embodiment.

The 1A . 1B show a tube-in-tube arrangement 5 with an inner tube 11 and an outer tube 13 , which are in an overlapping area 5.1 overlap each other. In this case, a seal is made on a respective conical lateral surface of the tubes, on each of which an (inner) sealing surface with the axial extent z11 and an (outer) sealing surface with the axial extent z13 is formed. In this case, the axial extensions z11 . z13 at least approximately the same size / width / long. Out 1B shows that the axial extensions z11 . z13 increase in axial relative movement (indicated by the thick arrows in the z direction) at least approximately to the extent in which the overlap region 5.1 increased. In other words, as the overlap increases, the sealing surface becomes larger, in particular, proportional. Due to the taper, the tensions in the pipes rise sharply, possibly also disproportionately. Unfavorable or detrimental here may also be that at the interface down at the free end of the inner tube, the tightness is getting worse, the greater the overlap. The sealing point is displaced away from the actual interface between the inner and outer tube. This can have technically disadvantageous effects, especially if the outer tube loses elasticity over time. It has also been found that in arrangements in which the tubes tilt relative to one another or align themselves at least in a small angular range relative to one another, a seal can not be ensured with good reliability. This also high bending stresses can be generated, which reduces the reliability.

The 2A . 2 B show a sealing coupling 10 with an inner (first) tube 11 , in particular a collecting tube in a cell of an electrolysis plant, and an outer (second) tube 13 , in particular standpipe, which tubes together a tube-in-tube arrangement 15 with an overlap region 15.1 form.

The sealing coupling 10 has a radial thickening 11.7 on which on a pipe wall 11.2 of the inner tube 11 is trained. In this case, the radial thickening 11.7 both on an inner circumferential surface 11.1 as well as on an outer lateral surface 11.3 formed by the pipe wall 11.2 was widened to the radial thickening 11.7 to build. The effective sealing surface 11:31 is through the outer surface 11.3 provided. A free end 11.5 is freely radially spaced from the outer tube 13 arranged.

The on the outer tube 13 effective sealing surface or the corresponding sealing surface portion 13:11 becomes through its inner lateral surface 13.1 provided. The outer lateral surface 13.3 at best assumes an indirect function in connection with the sealing, such as ensuring a desired surface pressure or a contact pressure from radially outside to the radial thickening 11.7 , A free end 13.5 is freely radially spaced from the inner tube 11 arranged. This allows for a certain orientation tolerance.

Both pipes 11 . 13 extend strictly axially (coaxially) along a central longitudinal axis M , however, provides the Abdichtkupplung 10 to a certain positional tolerance for a slightly angular position. This can provide the advantage in particular with regard to thermal expansions and thermally induced relative movements that the sealing coupling 10 autonomously adjusted without the tubes tilting, at minimum tension (self-adjustment). The sealing coupling 10 therefore also allows a long life and high reliability.

The radial thickening 11.7 points in the radial direction r a radial extent r7 on, which can be selected individually depending on the application and material pairings. The radial extent r7 remains largely constant during operation. Also one / the axial position z71 The radial thickening remains largely constant during operation. Anyway, the axial position z71 independent of an axial relative movement of the outer tube 13 relative to the inner tube. The same can for one / the axial extent Z72 the radial thickening apply: also the axial extent Z72 can remain constant, with the effect that the conditions at the sealing interface do not change, but independence from an axial relative movement of the outer tube 13 can be ensured relative to the inner tube. This also has an advantageous effect on the reliability and durability or stress of the pipes. With the sign u the circumferential direction is indicated. In the case of the sealing coupling shown here 10 can be a seal in the circumferential direction u be ensured completely circulating.

The 3 illustrates schematically some advantages of Abdichtkupplung 10 , In an axial relative movement .DELTA.z of the tubes relative to each other, a characteristic value s be kept substantially constant for material stress / stress in the respective tube, whereas in a conical tube-in-tube arrangement 5 according to the prior art, a proportional or even disproportionate voltage rise must be accepted with high risk that at least one of Pipes is stressed too much and, for example, kinks. In any case, these different voltages have a very adverse effect on the tightness. It is difficult to have such a wide range of voltages

The extent of an axial relative movement is indicated here by means of the symbol Δz and plotted on the abscissa.

The 4A . 4B show schematically an electrolysis system 1 with one or more cells 3 in which in each case at least one Abdichtkupplung 10 can be provided. In this application of Abdichtkupplung 10 can the outer standpipe 13 be formed in particular of plastic, and the inner manifold 11 a comparatively short pipe socket, in particular be made of metal. Thermally-based changes in position then take place, according to experience, especially in the standpipe 13 ,

For the functioning of the electrolysis system 1 the following can be said: The cell 3 consists of two halves, one of which is in 4B only one half is shown. The two halves are placed on top of each other and screwed together sealingly. An outlet or an outlet from the cell is below ( 4B ) or lower left ( 4A ). In the outlet is the so-called standpipe 13 used and at its upper end with the metallic manifold or nozzle 11 connected or verkuppelt. In operation, the cell is running 3 full of liquid, up to the top. The stub 11 then takes over the function of an overflow, in the manner of a pipe discharging from the cell or electrolysis plant, and the liquid can pass through the standpipe 13 get into the outlet. Thus, it is important that at this coupling between nozzles 11 and standpipe 13 Tightness can be ensured, even with relatively large changes in position or voltage fluctuations.

LIST OF REFERENCE NUMBERS

1

electrolysis plant

3

cell

5

Tube-in-tube assembly

5.1

overlap area

10

Abdichtkupplung

11

inner (first) pipe, in particular collecting pipe

11.1

inner jacket surface

11.2

pipe wall

11.3

outer jacket surface

11:31

sealing surface

11.5

free end

11.7

radial enlargement

13

outer (second) tube, in particular standpipe

13.1

inner jacket surface

13:11

Sealing surface or sealing surface section

13.3

outer jacket surface

13.5

free end

15

Tube-in-tube assembly

15.1

overlap area

M

central longitudinal axis

r7

Radial extension of the radial thickening

s

Characteristic value for material stress / stress

z71

Axial position of the radial thickening

Z72

axial extension of the radial thickening

z11

axial extension of the (inner) sealing surface

z13

axial extension of the (outer) sealing surface

r

radial direction

u

circumferentially

z

axial direction

Claims (15)

Sealing coupling (10) between at least two mutually storable / stored pipes (11, 13) of an electrolysis plant, in particular between at least one connected to a cell of the electrolysis plant standpipe and at least one outgoing from the cell or electrolysis plant manifold, the Abdichtkupplung on at least one pair of tubes Tubes on mutually abutting lateral surfaces (11.3, 13.1) is formed, characterized in that the tubes (11, 13) of the pair of tubes relative to each other in the axial direction sealingly against each other on a sealing surface (11.31) with size independent of an axial relative movement or relative position of the tubes Area are stored / loslagerbar. Sealing coupling after Claim 1 , wherein the lateral surface (11.3) of the inner tube of the tube pair at least one predefined axial position (z71) has a radial thickening (11.7) to the outside with sealing function, which at least partially defines the sealing surface (11.31) at the predefined axial position, the radial thickening being independent defined by an axial relative movement or relative position of the tubes size constant surface area of the sealing surface. Sealing coupling according to one of the preceding claims, wherein the size-constant sealing surface (11.31) is circumferential; and / or wherein the size-constant sealing surface (11.31) is rotationally symmetrical. Sealing coupling according to one of the preceding claims, wherein the size constant sealing surface (11.31) is linear or in the axial direction has a width (z11) less than 20% of the diameter of the inner tube (11), in particular a fully constant width; and / or wherein a radial thickening (11.7) on the lateral surface is symmetrical with respect to a cross-sectional plane orthogonal to the longitudinal axis (M) of the inner tube (11). Sealing coupling according to one of the preceding claims, wherein a / the radial thickening (11.7) on the lateral surface by a wall (11.2) of the tube is formed; and / or wherein the radial thickening is formed by a widening of the tube. A sealing coupling according to any one of the preceding claims, wherein a radial thickening (11.7) is disposed on the shell surface at a distance of at least 1mm or 2% of the diameter of the inner tube from a free end of the inner tube; and / or wherein the radial thickening (11.7) is arranged at a distance of at most 2 mm or 20% of the diameter of the inner tube from a free end of the inner tube. Sealing coupling according to one of the preceding claims, wherein a / the radial thickening (11.7) on the lateral surface in the radial direction (r7) is greater than 2% of the diameter of the outer tube (13); and / or wherein the radial thickening in the radial direction is less than 15% of the diameter of the outer tube. Sealing coupling according to one of the preceding claims, wherein a / the radial thickening (11.7) is overlapped on the lateral surface in the axial direction of the outer tube (13), in particular by at least 15 or 20% of the diameter of the outer tube. A sealing coupling according to any one of the preceding claims, wherein a free end (13.5) of the outer tube (13) is arranged / disposable freely spaced from the lateral surface of the inner tube (11). Sealing coupling according to one of the preceding claims, wherein the tubes (11, 13) of the pair of tubes are dimensioned such that the Abdichtkupplung by a frictional axial tolerant tube-in-tube arrangement (15) is arranged for sealing caused by elastic deformation frictional connection between the sealing surface (11.31) and a corresponding sealing surface portion (13.11) of the outer tube , Sealing coupling according to one of the preceding claims, wherein a tube of the tube pair, in particular the inner tube (11), or at least its free end (11.5) consists of metal and wherein the other tube of the tube pair or at least its free end (13.5) consists of plastic , in particular PTFE. Sealing coupling according to one of the preceding claims, wherein the Abdichtkupplung is adapted for axial relative movements in the range of 5 to 15mm or 20 to 40% of the diameter of the inner tube (11), in particular 10mm or 30% of the diameter of the inner tube. Sealing coupling between at least two mutually mounted tubes (11, 13) of an electrolysis plant, in particular a sealing coupling (10) according to one of the preceding claims, produced by coupling two tubes at their free ends (11.5, 13.5) to abutting lateral surfaces (11.3, 13.1) and by releasing the tubes relative to each other by means of the coupling, wherein the floating bearing and sealing on at least one predefined axial position (z71) of the inner tube to a sealing surface (11.31) takes place such that regardless of an axial relative movement or relative position of the tubes, the sealing surface sized constant or remains arranged. Sealing coupling according to one of the preceding claims, set up or designed as a self-locking, axially released heat-expansion-tolerant coupling, in particular with a coefficient of thermal expansion of the outer tube (13) greater than a coefficient of thermal expansion of the inner tube (11). Use of a tube-in-tube arrangement (15) for forming a sealing coupling, in particular a sealing coupling (10) according to one of the preceding claims, between at least one tube (11) of metal and at least one tube (13) of plastic in one Electrolysis system, in particular an internally overlapping collecting tube made of metal and an externally overlapping standpipe made of plastic, wherein the inner tube (11) by means of at least one at a predefined axial position (z71) on the inner tube formed sealing surface (11.31) with size independent of an axial relative motion size constant area at a geometrically corresponding sealing surface portion (13.11) of the overlapping outer tube (13) is sealed axialtolerant at effected by elastic deformation of the outer tube adhesion.

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