Method for making a heat exchanger and heat exchanger

Abstract

Method (100) for making a heat exchanger (10) comprising: - a plurality of internal tubes (1), - a cloak (3), - a first tube plate (21) crossed by the internal tubes (1), - a second tube plate (22) crossed by the internal tubes (1), said method (100) comprising the following phases in order: - a preparation phase (110) of the internal tubes (1) and the tube plates (21), (22) and in particular an internal plate (21) and an external plate (22); - a welding phase (140) of the tubes on the external plate (21); and characterised by the fact that it also comprises a sealing phase (150), subsequent to the welding phase (140), and that during the sealing phase the following subphases are foreseen in order: - application of a catalyst (151) which wets all surfaces of the second tube plate (22) and the internal tubes (1); - application of a sealant (152) which wets all surfaces of the second tube plate (22) and the internal tubes (1); catalyzing the sealant (154).

Description

[0001] METHOD FOR MAKING A HEAT EXCHANGER AND HEAT EXCHANGER

[0002] The present invention relates to a tubular heat exchanger and a related manufacturing method.

[0003] Field of invention

[0004] The invention falls within the technical field of heat exchangers, in particular within the technical field of systems and processes for the production of tubular heat exchangers.

[0005] Known technique

[0006] Currently, several types of heat exchangers with similar geometries and construction forms are used and present on the market.

[0007] One of the types of exchangers most used in various production, domestic and industrial fields concerns tubular heat exchangers.

[0008] Another feature that distinguishes different types of exchangers is the presence of one or more tube plates. In particular, there are single tube plate (MRW) or double tube plate (MRP) exchangers.

[0009] Such heat exchangers are made using a brazing process where small tubes are welded / brazed together with the addition of additional material.

[0010] Brazing is a process that is necessary for joining small pipes because, unlike when joining medium or large pipes, it is not possible to weld the pipes together.

[0011] More specifically, brazing is an assembly operation that is obtained by melting a filler metal (for example, silver or tin-based alloys) without incurring the melting of the base metal. In this operation, it is necessary that the melting point of the filler metal is at a lower temperature than that of the base metal.

[0012] There are two main types of brazing: soft brazing and hard brazing. Hard brazing assembly requires melting temperatures ranging from 600 to 1 ,000°C, while soft brazing requires the melting of the filler metal at temperatures lower than 450°C.

[0013] On the other hand, even known welding processes are not capable of automatically welding small elements or pipes.

[0014] In fact, welding to join small pipes is currently not particularly effective, and is often problematic, as the high temperatures resulting from this procedure cause the pieces to melt, with the obvious consequences of this. Furthermore, a further problem is given by the fact that the welders, in particular the orbital welders, need to be centered inside the tube, and their size does not allow a solid attachment for welding.

[0015] Joining pipes through brazing also has some disadvantages, including:

[0016] - the fact that the materials used are not homogeneous among themselves;

[0017] - the possibility that material added by brazing may be removed during use of the heat exchangers; and

[0018] - the possibility that the material added by brazing will contaminate the fluid inside the heat exchanger tubes.

[0019] The problem of contamination of the fluid present inside the exchanger is a very sensitive issue in the sector and is increasingly relevant in all those applications in which process fluids and not contaminated fluids must flow in the exchanger, such as for example in the pharmaceutical and agri-food sectors.

[0020] The most recent regulations, in fact, define it as necessary to guarantee the conformity of the exchanger for contact with water and food substances, avoiding that the exchanger itself or some of its components can contaminate the water or the fluids that flow inside it.

[0021] For this reason, the risks of contamination related to brazing processes can no longer be tolerated and acceptable in sectors regulated by such regulations where it is necessary to produce exchangers, even with very small tubes, which avoid contamination and are not made by brazing.

[0022] It is therefore necessary to create an alternative process that allows the production of heat exchangers with small-sized pipes that simultaneously guarantee adequate hydraulic sealing and no risk of contamination.

[0023] The state of the art is also represented by what is shown in documents CN 114 871 532, US 3 471 178, EP 0 140 069, WO 2006 / 090626, CN 113 102 870.

[0024] Purpose of the invention

[0025] The aim of the present invention is therefore to provide a tubular heat exchanger and a related production method to obtain it capable of solving the above-mentioned drawbacks and critical issues .

[0026] Another purpose of the present invention is to provide a tubular heat exchanger and a related production method to obtain it that allows the joining of small-sized tubes having an external diameter and tube wall thickness of a few millimetres. A further object of the present invention is to provide a tubular heat exchanger and a related production method to obtain it made with heterogeneous materials that do not allow the migration of metals into the substances that flow inside it.

[0027] Another purpose of the present invention is to create a tubular heat exchanger and a related production method to obtain it that is able to guarantee a correct seal and high reliability of use.

[0028] A further object of the present invention is to provide a tubular heat exchanger and a related manufacturing method to obtain it which avoids contamination of the substances inside it.

[0029] Another purpose of the present invention is to create a tubular heat exchanger and a related production method to obtain it that complies with the most recent legal regulations.

[0030] A further object of the present invention is to provide single tube plate and double tube plate tubular heat exchangers and their relative production method, which allow to obtain an object completely made of stainless steel.

[0031] Finally, a final object of the present invention is to provide a tubular heat exchanger that is economical and easy to produce in place of the advantages achieved and its related production method.

[0032] These and other purposes are achieved by a tubular heat exchanger and related manufacturing method to obtain it according to the independent claims attached.

[0033] Further detailed technical characteristics are reported in the attached dependent claims.

[0034] Subject of the invention

[0035] The invention also relates to a method for manufacturing a heat exchanger. The method comprises at least the following steps in order:

[0036] - a preparation phase of the internal tubes and tube plates;

[0037] - a phase of regulation and control of the welding parameters;

[0038] - a welding preparation phase;

[0039] - a welding phase using a ceramic torch equipped with a needle.

[0040] Also according to the invention, the welding preparation phase includes a positioning sub-phase which involves setting the position of the internal tubes with the ends inserted into the through holes flush with the external surface of the first tube plate. The position can also be set back or protruding by a distance within the range of ±0.3mm.

[0041] Still according to the invention, the preparation phase involves setting at least one of the following dimensions: the thickness A of the tube plate from 4mm to 20mm; the diameter B of the through holes of the tube plate 21 is 0.1 mm (tolerance ±0.05); through holes in the tube plate with a chamfer of approximately 45° for a depth equal to the thickness of the wall of the internal tube to be fixed; internal tubes with diameter 1 -12mm; thickness of internal tubes in the range 0.4-1 mm.

[0042] Also according to the invention, the control and regulation phase includes at least one of the following sub-phases: overlap, with timed evanescence, based on the diameter of the internal tubes; setting of the final current, for example to 3A (tolerance ±50%); regulation of the shielding gas e.g. at 91 / min (tolerance ±50%); welding speed regulation e.g. 40mm / min (tolerance ±50%); control of welding parameters.

[0043] The invention also includes a method for the construction of an exchanger with a second tube plate crossed by the internal tubes and positioned internally with respect to the first tube plate, in which the sealing phase preferably comprises the following sub-phases in order: application of a catalyst that wets all surfaces of the second tube plate and the internal tubes; application of a sealant that wets all surfaces of the second tube plate and internal tubes; catalyzing of the sealant at controlled temperature and humidity; maintenance of environmental conditions.

[0044] Also according to the invention, after the sub-phase of applying a sealant, and before the sub-phase of catalyzing the sealant, the method provides for the following sub-phase: application of an external depression if necessary to ensure greater penetration of the sealant between the internal pipes and the holes of the second tube plate.

[0045] The invention also relates to a heat exchanger made according to the method described.

[0046] Also according to the invention, the heat exchanger may comprise a layer of catalytic sealant on the contact surfaces between the second plate and the internal tubes.

[0047] Brief description of the figures

[0048] The present invention will now be described, by way of example but not limitation, according to some of its preferred embodiments, and with the aid of the attached figures, in which:

[0049] - Figure 1 A is a front view of a double tube plate type tubular exchanger

[0050] - Figure 1 B is a side view of the tubular exchanger of Figure 1 A;

[0051] - Figure 1 C is an isometric view of the tubular exchanger of Figure 1 A;

[0052] - Figure 1 D is a longitudinal section of an end portion of the tubular exchanger of Figure 1A;

[0053] - Figure 2A is a front view of a single tube plate tubular exchanger.

[0054] - Figure 2B is a side view of the tubular exchanger of Figure 1 A;

[0055] - Figure 2C is an isometric view of the tubular exchanger of Figure 1 A;

[0056] - Figure 2D is a longitudinal section of an end portion of the tubular exchanger of Figure 1A;

[0057] - Figure 3A shows a detail of the TIG welding process according to the invention;

[0058] - Figure 3B shows a further detail of the TIG welding process according to the invention;

[0059] - Figure 4A shows a detail of the PAW welding process according to the invention;

[0060] - Figure 4B shows a further detail of the PAW welding process according to the invention;

[0061] - Figure 5 shows a detail of the sealant application process according to the invention;

[0062] - Figures 6A and 6B illustrate the steps of the manufacturing method of a heat exchanger according to the invention. Detailed description

[0063] With reference to the figures mentioned, a preferred embodiment of a tubular heat exchanger and the related manufacturing method for obtaining it according to the invention are shown.

[0064] Referring to the figures above, the production method of a heat exchanger which is the object of the invention is indicated by the numerical reference 100 and allows the production of a tubular type heat exchanger 10.

[0065] A tubular heat exchanger 10 is composed of a plurality of internal tubes 1 parallel to each other and arranged along the direction of main extension of the heat exchanger 10 itself.

[0066] These internal tubes 1 are joined together and to one or more tube plates 21 , 22 and arranged inside a casing 3.

[0067] In particular, the jacket 3 envelops the internal tubes 1 in the central portion of the heat exchanger 10, while the tube plates are crossed by the internal tubes 1 at their ends and at the ends of the heat exchanger 10.

[0068] Advantageously, the mantle 3 has the final shape of a cylindrical tube.

[0069] The 100 method allows the construction of both single tube plate (MRW) and double tube plate (MRP) tubular exchangers.

[0070] In Figures 1 A-1 D a double tube plate (MRP) tubular type heat exchanger 10 is visible.

[0071] Referring to figure 1 D, the tubular exchanger comprises an external tube plate 21 and an internal tube plate 22.

[0072] In Figures 2A-2D a single tube plate (MRW) tubular type heat exchanger 10 is visible.

[0073] With reference to figure 2D, the tubular exchanger comprises a single tube plate 23.

[0074] The method 100 according to the invention comprises the following steps:

[0075] - a preparation phase 110 of the elements and materials;

[0076] - a phase of regulation and control of the parameters 120;

[0077] - a welding preparation phase 130;

[0078] - a welding phase 140.

[0079] In the case of the construction of a double tube plate exchanger 10, method 100 also includes a sealing phase 150 following the welding phase 140. In particular, in the preparation phase 110 it is necessary to clean, degrease and prepare the internal tubes 1 and the tube plates 21 , 22 before assembling the heat exchanger 10.

[0080] In more detail, preparation phase 110 includes the following sub-phases:

[0081] - a cleaning sub-phase 111 of the tube plates 21 , 22, configured to render the surface of the tube plates 21 , 22 ready for subsequent welding and / or sealing operations, the cleaning sub-phase may for example comprise polishing, cleaning and degreasing operations 111 of the tube plates 21 , 22;

[0082] - a spot welding sub-phase 112 in which the spot welding and positioning of the tube plates 21 , 22 takes place;

[0083] - a sub-phase of insertion 113 of the internal tubes 1 , previously cleaned and degreased, into the jacket 3;

[0084] - a sub-phase of capping 114 of the ends of the exchanger 10 to prevent the escape of the gases used to protect the welding area.

[0085] The operations of the cleaning sub-phase 111 can be carried out in different ways, for example by means of an ultrasonic cleaning process, by immersion or by manual action with solvents suitable for the products used in the welding and sealing processes.

[0086] In the preparation phase 110 and its sub-phases 111 , 112, 113, 114 it is advantageous to ensure the correct positioning of the internal tubes 1 with respect to the tube plates 21 , 22 in order to guarantee the correct welding of the heat exchanger 10.

[0087] In the control and regulation phase 120, the welding system parameters are regulated and checked.

[0088] Advantageously, the following sub-phases are carried out in the control and regulation phase 120:

[0089] - a sub-phase for regulating the starting current 121 based on the temperature of the tube plates 21 , 22;

[0090] - a sub-phase of overlapping of the weld 122, with timed fading, based on the diameter of the internal tubes 1 ;

[0091] - a sub-phase for setting the final current 123 for example at 3A (tolerance ±50%); - a sub-phase of regulation of the shielding gas 124 for example at 91 / min (tolerance ±50%);

[0092] - a sub-phase for regulating the welding speed 125 for example at 40mm / min (tolerance ±50%);

[0093] - a sub-phase of control of the welding parameters 126.

[0094] By way of example, the following parameters can be used in the starting current regulation sub-phase 121 , setting the starting current based on the temperature of the tube plates 21 , 22:

[0095] - starting current at 34A (tolerance ±5%) for a plate temperature of 16- 25°C;

[0096] - starting current at 32A (tolerance ±5%) for a plate temperature of 30- 50°C;

[0097] - starting current at 31 A (tolerance ±5%) for a plate temperature of 50- 70°C;

[0098] - starting current at 30A (tolerance ±5%) for a plate temperature of 80- 100°C;

[0099] - starting current at 29A (tolerance ±5%) for a plate temperature of 100- 120°C;

[0100] - current of 28A (tolerance ±5%) for a plate temperature of 120-170°C. In a preferred embodiment of the present invention, the current varies from a starting current of 30A (tolerance + 5 / -20%) to a final current of 3A with a ramp down at the end of processing.

[0101] The welding preparation phase 130 preferably includes the following subphases :

[0102] - a sub-phase of positioning 131 of the mass as close as possible to the welding area;

[0103] - a sub-phase of positioning in vice 132;

[0104] - a sub-phase of venting the welding shielding gas 133;

[0105] The welding phase 140 is carried out, after the welding preparation phase 130, to weld and join the internal tubes 1 to the tube plate 21 , in the case of a singletube plate exchanger 10, and to weld and join the internal tubes 1 to the external tube plate 21 , in the case of a double-tube plate exchanger 10. The welding phase 140 is carried out on a multi-axis, numerically controlled welding system including a welding machine 40 specifically designed for the construction of the 10 exchangers.

[0106] The welding machine 40 includes a 41 TIG torch (Tungsten Inert Gas) or PAW (Plasma Arc Welding) from which a welding needle 42, for example made of tungsten, emerges or re-enters, which carries out the welding.

[0107] Figures 3A and 3B show a detail of a TIG welding process in which the needle 42 protrudes from the torch 41 .

[0108] Instead, in figures 4A and 4B a detail of a PAW welding process is visible in which the needle 42 is recessed with respect to the torch 41 .

[0109] In more detail, the rotation speed of the welding torch 41 influences the heat input of the welding machine 40 since, at a higher speed of the welding torch 41 , the quantity of energy transmitted increases and consequently also the heat.

[0110] For this reason it is necessary to properly combine the parameters in order to have a weld that has an adequate heat input.

[0111] The CNC system also includes a cylinder, not visible, for containing the gas used during welding. This cylinder is connected to the welding machine 40.

[0112] To ensure correct welding, it is necessary, in the material preparation 110 and positioning 131 phases, to maintain at least one of the following parameters, respectively of size and positioning:

[0113] - the thickness A of the tube plate 21 from 4mm to 20mm;

[0114] - the diameter B of the through holes of the tube plate 21 is 0.1 mm (tolerance +0, +0.05);

[0115] - through holes in the tube plate with a chamfer of approximately 45° for a depth equal to the thickness of the wall of the internal tube 1 to be fixed; this advantageously allows for a deeper welding bead to be obtained and consequently achieve the mechanical resistance required by the standards;

[0116] - internal tubes diameter 1 -12mm;

[0117] - thickness of internal tubes 1 in the range 0.4-1 mm;

[0118] - external beveling of the ends of the internal tubes.

[0119] Advantageously, always in the material preparation 110 and positioning 131 phases, it is also possible to maintain one or more of the following optional parameters: - internal tubes 1 with ends externally chamfered by 45° (tolerance ±30%) so as not to allow the molten material to overflow towards the inside of the internal tubes 1 ;

[0120] - internal tubes 1 flush with the tube plate 21 or set back or protruding by a distance D of 0.05mm (tolerance ±0.5) so as to reduce the quantity of material to be dissolved, and therefore prevent excess material from ending up inside the internal tubes 1 , blocking them;

[0121] - protrusion or recess of the needle 42 from the ceramic torch 41 by a distance E of 2.5-3.5mm (tolerance ±1 ).

[0122] Advantageously, to avoid welding errors, it is advisable to change the welding needle 42 approximately every two hundred welds and change the gas cylinder before it is completely exhausted, so as to avoid having to interrupt the welding process.

[0123] Furthermore, the welding needle 32 should be kept at a distance F from the tube plate between 0.8mm and 1.3mm (tolerance of +0.3 / -0.2) paying particular attention to the calibration and zeroing of the CNC system.

[0124] Advantageously, the possibility of regulating the distance of the welding needle 32 allows you to regulate its heat input as the closer it gets to the area to be welded, the more it heats that area.

[0125] In a particular embodiment of the invention, the welding sequence is managed by a specially developed software program.

[0126] In the case of the construction of a double plate exchanger 10, all the previous phases are implemented in addition to the sealing phase 150 which is carried out after welding the external tube plate.

[0127] In fact, in this case, the pipes are inserted into the two plates, then the external plate 22 is first welded and then the internal plate 21 is sealed in the correct position through the use of a sealant 5, as exemplarily illustrated in figure 5.

[0128] In particular, therefore, the sealant 5 may comprise two portions, a proper sealant portion, and an activating portion, also called catalyst, thus substantially defining a catalytic sealant. The activating portion and the sealing portion may be conveniently configured to not allow sealing when used alone. Preferably, the activating portion may be characterised to work even in the absence of oxygen, or in any case in the absence of air - i.e. it may be an anaerobic catalyst. In particular, such sealant 5 can be an anaerobic sealant, OF acrylic of urethane methacrylate nature having characteristics of low viscosity and high mechanical resistance. Advantageously, the catalytic sealant can be of the type commonly used for sealing coaxial elements, such as parts of engine cylinders. In particular , it can therefore be configured to present a high thermal resistance, which allows its use on metals during welding operations.

[0129] Advantageously, these types of catalytic sealants 5 provide good high temperature performance and tolerance to oils and surface contamination.

[0130] Alternatively, the catalytic sealant may also be an acrylic resin containing polymers, preferably based on methacrylate or acrylate, and more preferably based on methyl methacrylate, or butyl methacrylate or an epoxy resin, preferably based on bisphenol A and resorcinol.

[0131] Advantageously, resins containing methacrylate or acrylate-based polymers are known for their ability to bond to various materials, including metal, plastic, and glass. These resins also offer good resistance to chemicals and high temperatures.

[0132] Epoxy resins have excellent mechanical and chemical resistance, while acrylic resins offer good adhesion and flexibility. By combining the two types of resin, sealants with improved properties can be obtained.

[0133] Acrylic resins and epoxy resins are two distinct types of polymers and do not mix directly. However, in some preferred sealant formulations, they can be used in combination to take advantage of the benefits of both types.

[0134] Even more advantageously, to make the sealant 5 work better, before applying it, it is possible to carry out a cleaning pre-treatment and possibly also an activation on the surfaces on which it is to be applied.

[0135] As an example, cleaning can be done with a solvent cleaner with isoparaffin, dioxymethane and ethanol mixture while activation can be done with an activator (catalyst) for anaerobic adhesives and sealants with copper salts and aliphatic amine to accelerate the polymerization of catalytic sealants 5.

[0136] The sealing stage 150, exclusive to the 10 double plate heat exchangers (MRP) includes:

[0137] - a sub-phase of application of the activator 151 which wets all surfaces of the second tube plate 21 and the internal tubes 1 ;

[0138] - a sub-phase of applying the sealant 152 which wets all surfaces of the second tube plate 21 and the internal tubes 1 ; - a possible sub-phase of application of an external depression 153 to ensure greater penetration of the sealant between the internal pipes 1 and the tube plate hole;

[0139] - a sub-phase of catalyzing the sealant 154 at controlled temperature and humidity;

[0140] - a maintenance sub-phase 155 of the environmental conditions for the duration foreseen by the sealant manufacturer's specifications.

[0141] The application and drying times and methods of the catalyst and sealant in sub-phases 151 and 152 are defined by the respective manufacturers' instructions.

[0142] Advantageously, to test the exchanger 10 it is possible to carry out a further hydraulic testing phase 160 at the end of the previous phases.

[0143] To correctly carry out the 100 method, it is necessary to pay maximum attention to the mechanical processes, respect the processing tolerances of all the elements and guarantee the orthogonality of the machined planes.

[0144] The double tube plate versions of the exchangers ensure that no mixing occurs between the product and the service fluid in the event of breakage of the welded tube-plate union.

[0145] Advantageously, welding of the tube to the tube sheets can be done with PLW (LASER), PAW (PLASMA) or TIG processes.

[0146] Following numerous welding tests with the above processes and with the execution of welding macros, it was decided to adopt the TIS and PAW processes, without excluding the use of other processes in the future and / or in different embodiments.

[0147] To identify the best possible conjugation and combination of parameters, numerous welding tests were carried out using as a starting point internal tubes 1 with a thickness of 0.5 mm and a diameter of 3 mm and a tube plate with a thickness of 5 mm.

[0148] These tests were carried out in particular to identify the best welding speed, i.e. the rotation speed of the welding torch, the best welding current, the best voltage, the best bevel angle or the best combination of the above parameters in order to achieve the best heat input.

[0149] Initially, the first welding tests with the starting measurements reported above achieved results of 53mm / min and 43mm / min relating to the welding speed, which were later considered not sufficiently adequate. In a further welding test, always referring to the starting point measurements, the following results were achieved: welding speed of 40mm / min and starting welding current of 30A.

[0150] Following further welding tests, it was decided to remain within the following ranges: welding speed between 10-30mm / min , welding voltage between 8-9V and starting welding current between 25-35Afor a heat input between 0.24-1 .134kJ / mm. These ranges allow for obtaining certification and satisfying standards and design requirements.

[0151] In a preferred embodiment, the following combination of parameters was identified: external tube chamfer of 45°, welding speed of 12mm / min , welding voltage of 8.5V and starting welding current of 32A for a heat input of 0.816kJ / mm.

[0152] This combination of parameters, in reference to the starting point described above, has achieved excellent results and led to obtaining the ISO 15614-8 certification.

[0153] Advantageously, the method of manufacturing a tubular heat exchanger according to the present invention allows joining tubes of very small dimensions and thicknesses such as with an external diameter less than 2mm and a wall thickness less than 0.3mm.

[0154] Advantageously, all the above results can also be considered in light of their tolerances.

[0155] Even more advantageously, the production range achieved with this method can include the production of single tube plate (MRW) and also double tube plate (MRP) tubular exchangers.

[0156] A further advantage is given by the fact that the process of the invention allows to obtain heat exchangers of very small dimensions and in any case completely in stainless steel, with a consequent notable reduction in the risk of contamination of the liquids.

[0157] From the description given, the characteristics of the production system for industrial exchangers , the object of the invention, are clear, as are the advantages.

[0158] Finally, it is clear that numerous other variations can be made to the device and method in question, without departing from the principles of novelty inherent in the inventive idea, just as it is clear that, in the practical implementation of the invention, the materials, shapes and dimensions of the illustrated details may be any according to the needs and the same may be replaced with other equivalent ones.

[0159] Where the features and techniques mentioned in any claim are followed by reference signs, such reference signs have been included for the sole purpose of increasing the intelligibility of the claims and, accordingly, such reference signs have no limiting effect on the interpretation of each element identified by way of example by such reference signs.

Claims

CLAIMS1 . Method (100) for making a heat exchanger (10) comprising:- a plurality of internal tubes (1 ),- a cloak (3),- a first tube plate (21 ) crossed by the internal tubes (1 ),- a second tube plate (22) crossed by the internal tubes (1 ), said method (100) comprising the following phases in order:- a preparation phase (110) of the internal tubes (1 ) and the tube plates (21 , 22) and in particular an internal plate (21 ) and an external plate (22);- a welding phase (140) of the pipes on the external plate (21 ); and characterised by the fact that it also comprises a sealing phase (150), subsequent to the welding phase (140), and that during the sealing phase the following sub-phases are foreseen in order:- application of a catalyst (151 ) which wets all surfaces of the second tube plate (22) and the internal tubes (1 );- application of a sealant (152) that wets all surfaces of the second tube plate (22) and the internal tubes (1 );- sealant catalysis (154).

2. Method (100) for the production of a heat exchanger (10) as in claim 1 , characterised by the fact that it includes a preparation phase of the internal pipes (110), prior to the welding phase, in which the preparation phase of the internal pipes (110) involves setting at least one of the following dimensions: the thickness (A) of the tube plate (21 ) from 4mm to 20mm; the diameter (B) of the through holes of the tube plate (21 ) of 0.1 mm (tolerance ±0.05); through holes in the tube plate with a chamfer of approximately 45° for a depth equal to the thickness of the wall of the internal tube (1 ) to be fixed; internal tubes (1 ) with diameter 1 -12mm; thickness of internal tubes (1 ) in the range 0.4-1 mm.

3. Method (100) for the production of a heat exchanger (10) as claimed in one or more of claims 1 , 2 characterised by the fact that it includes a control and regulation phase (120) of the welding parameters, and the control and regulation phase (120) includes at least one of the following phases: overlap of the weld (122), with timed fading, based on the diameter of the internal tubes (1 ); setting of the final current (123), for example to 3A (tolerance ±50%); gas regulation (124) for example at 9 I / min (tolerance ±50%); welding speed regulation (125) for example at 40mm / min (tolerance ±50%); control of welding parameters (126).

4. Method (100) according to one or more of the preceding claims characterised by providing, after the sub-phase of applying a sealant (152), and before the sub-phase of catalysing the sealant (154), a sub-phase of applying an external depression (153).

5. Method (100) according to one or more of the preceding claims characterised in that the internal tubes (1 ) protrude by a distance (E) between 0.05 and 0.55 mm.

6. Method (100) according to one or more of the preceding claims characterised in that the welding phase is carried out using a ceramic torch (41 ) equipped with a needle (42) which protrudes or retracts by a distance between 2.5 and 3.5 mm.

7. Method (100) according to one or more of the preceding claims characterised in that the control and regulation phase (120) includes a sub-phase for regulating the starting current (121 ), in which the starting current is regulated based on the temperature of the plate (21 ):- starting current at 34A (tolerance ±5%) for a plate temperature of 16-25°C;- starting current at 32A (tolerance ±5%) for a plate temperature of 30-50°C;- starting current at 31 A (tolerance ±5%) for a plate temperature of 50-70°C;- starting current at 30A (tolerance ±5%) for a plate temperature of 80-100°C;- starting current at 29A (tolerance ±5%) for a plate temperature of 100-120°C;current of 28A (tolerance ±5%) for a plate temperature of 120-170°C.

8. Method (100) according to one or more of the preceding claims characterised in that the internal tubes (1 ) have ends externally bevelled by 45° (tolerance ±30%).

9. Method (100) according to one or more of the preceding claims characterised in that the internal tubes (1 ) during the welding phase are positioned flush with the tube plate 21 or set back or protruding by a distance D of 0.05mm (tolerance ±0.5).

10. Method (100) according to one or more of the preceding claims characterised in that the catalyst is: based on acrylate or methacrylate, and / or based on epoxy resin.

11. Method (100) according to one or more of the preceding claims characterised in that the catalyst is of the anaerobic type.

12. Method (100) according to one or more of the preceding claims characterised in that the internal tubes (1 ): they are not sealed on the internal plate (21 ) and / or they are not welded on the external plate (22)13. Method (100) according to one or more of the preceding claims characterised in that:- the thickness A of the tube plate (21 , 22) from 4 mm to 20 mm;- the diameter B of the through holes of the tube plate (21 ,22) is 0.1 mm (tolerance +0, +0.05);- the through holes of the tube plate have a chamfer of approximately 45° for a depth equal to the thickness of the wall of the internal tube 1 to be fixed- the internal tubes (1 ) have a diameter of 1 -12mm;- the thickness of the internal tubes 1 is in the range 0.4-1 mm;- the internal tubes (1 ) have external chamfering at the ends.1 4. Heat exchanger (10) made according to the method (100) as in one or more of the previous claims.

15. Heat exchanger (10) made according to the method (100) according to one or more of claims 1 -13, characterized in that it comprises a layer of catalytic sealant (5) on the contact surfaces between the second plate (22) and the internal tubes (1 ).

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