METHOD FOR PRODUCING A CORROSION-RESISTANT ASSEMBLY OF A FIELD DEVICE

Abstract

The invention relates to a method for producing a corrosion resistant assembly of a field device for determining or monitoring a physical or chemical process variable of a medium in an automated plant and to a corresponding assembly, wherein the assembly is composed of at least a first component and a second component, wherein the components are connected with one another in a connection region, wherein the first component is composed at least in the connection region of a corrodible material and wherein the second component is composed at least in the connection region of corrosion resistant material or of a corrodible material.

Claims

1-13. (canceled)

14. A method for manufacturing a corrosion resistant assembly of a field device for determining or monitoring a physical or chemical process variable of a medium in an automated plant, wherein the assembly comprises at least a first component and a second component, wherein the first component includes, at least in a first connection region, a corrodible material, and wherein the second component includes, at least in a second connection region, a corrosion resistant material or a corrodible material, the method comprising: applying a first coating of a corrosion resistant material on at least a portion of the first component in the first connection region, directly or via a first functional intermediate layer, using a generative manufacturing method such that the first coating has a first thickness profile; when the second component includes, at least in the second connection region, a corrodible material, applying a second coating of a corrosion resistant material on at least a portion of the second component in the second connection region, directly or via a second functional intermediate layer, using a generative manufacturing method such that the second coating has a second thickness profile; when the second component includes, at least in the second connection region, a corrosion resistant material, connecting the first component and second component to each other in the first and second connection regions, respectively, via a welding method, wherein, due to the first thickness profile, a weld is formed essentially between the first coating of the first component and the second component; or when the second component includes, at least in the second connection region, a corrodible material, connecting the first component and second component to each other in the first and second connection regions, respectively, via a welding method, wherein, due to the first thickness profile and second thickness profile, a weld is formed essentially between the first coating of the first component and the second coating of the second component.

15. The method of claim 14, wherein a three-dimensional printing method is used to apply the first coating with the first thickness profile and/or the first functional intermediate layer, and wherein, when the second component includes a corrodible material at least in the second connection region, the three-dimensional printing method is used to apply the second coating with the second thickness profile and/or the second functional intermediate layer.

16. The method of claim 15, wherein the three-dimensional printing method is a selective laser sintering method.

17. The method of claim 14, wherein the first coating, the first functional intermediate layer, the second coating and/or the second functional intermediate layer are applied with an essentially homogeneous thickness, and wherein the first thickness profile and/or the second thickness profile are formed via a grinding or turning process, and/or wherein thickness profiles of the first and second functional intermediate are formed via a grinding or turning process.

18. The method of claim 14, wherein the welding method is a laser welding method.

19. The subassembly of claim 14, wherein the corrosion resistant material of the first coating and/or second coating is gold, platinum, tantalum, zirconium, nickel, Hastelloy or a chemically resistant copper alloy.

20. A subassembly of a field device configured for determining or monitoring a physical or chemical process variable of a medium in an automated plant, the assembly comprising: the first component having the first connection region; and the second component having the second connection region, wherein the first component and the second component are welded together in the first and second connection regions, respectively, wherein at least one of the first and second components is composed of a corrodible material at least in the first or second connection regions, respectively, and wherein the assembly is manufactured by the method of claim 14.

21. The subassembly of claim 20, wherein the subassembly is a diaphragm seal of a sensor element adapted for determining and/or monitoring pressure of the medium, wherein the first component of the diaphragm seal is a flange of a corrodible material and is configured to be attached to a process flange, wherein the second component of the diaphragm seal is a measuring membrane of a corrosion resistant material, and wherein the flange and the measuring membrane are connected to each other such that a chamber is formed in the sensor element, the chamber filled with a pressure transfer liquid and sealed from the medium.

22. The subassembly of claim 21, wherein the first coating on the flange and the second coating on the measuring membrane are produced from the same corrosion resistant material, wherein the corrosion resistant material is tantalum, Monel or nickel alloy.

23. The subassembly of claim 21, wherein the flange is stainless steel.

24. The subassembly of claim 20, wherein the first thickness profile in the first connection region and the second thickness profile in the second connection region is between 0.1 and 5 mm.

25. The subassembly of claim 20, wherein the first thickness profile in the first connection region and the second thickness profile in the second connection region is between 0.1 and 0.5 mm.

26. The subassembly of claim 20, wherein the measuring membrane has a thickness in a range from 0.025 to 0.2 mm.

27. The subassembly of claim 20, wherein the subassembly is a vibronic sensor configured to determine a fill level, density and/or viscosity of the medium, wherein the first component of the vibronic sensor is a flange of a corrodible material and is configured to be attached to a process flange, wherein the second component of the vibronic sensor is a sensor element of a corrosion resistant material, wherein the sensor element includes a pot-shaped housing that is sealed with a membrane on an end region facing the medium, wherein membrane includes at least one oscillatory tine.

28. The subassembly of claim 27, wherein the sensor element is manufactured of stainless steel and wherein the first coating on the flange is a coating of stainless steel.

29. The subassembly of claim 20, wherein the corrosion resistant material of the first coating and/or second coating is gold, platinum, tantalum, zirconium, nickel, Hastelloy or a chemically resistant copper alloy.

Description

[0032] The invention will now be explained in greater detail based on the appended drawing. The figures of the drawing are all sectional views and show as follows:

[0033] FIG. 1 a solution known from the state of the art for a vibronic sensor element, in the case of which the protective cover layer for the component to be protected against corrosion was applied via a plating method,

[0034] FIG. 2 a solution for a diaphragm seal known from the state of the art, in the case of which the protective cover layer for the component to be protected against corrosion was applied via a galvanic coating method,

[0035] FIG. 3 a solution for a diaphragm seal known from the state of the art, in the case of which the protective cover layer for the component to be protected against corrosion was applied via a hard soldering, or brazing, method,

[0036] FIG. 4 a schematic view, which illustrates the local sintering/melting of metal particles of the invention in the case of a selective laser sintering method (SLS),

[0037] FIG. 5 a schematic view of an assembly of a diaphragm seal, which was produced according to the method of the invention, and

[0038] FIG. 6 a schematic view of an assembly of a vibronic sensor, which was produced according to the method of the invention.

[0039] Illustrated in FIGS. 1-3 are sections of assemblies, which are protected against corrosion via coating methods known from the state of the art.

[0040] FIG. 1 shows a solution known from the state of the art for protecting a vibronic sensor element 10 against corrosion by a medium 51 or by a corrosive atmosphere in a container, in which the medium 51 is arranged. For reasons of cost, the flange 25 is composed of a corrodible material, e.g., stainless steel. Flange 25 is coated via a plating method on the process side in the region of the area 21 to be sealed with a layer of corrosion resistant material, e.g., Hastelloy. The bores 18 in the flange 25 serve for securing the vibronic sensor element 10 on a process flange (not shown).

[0041] The other components of the sensor element 10, especially the sensor pot 11, or the pot-shaped housing 11, and the oscillatable unit 12 composed of the membrane 13 on the process facing end region of the sensor pot 11 and the oscillatory fork 13 with two tines 14thus, all components, which come in contact with the medium or the atmosphere in the containerare manufactured of corrosion resistant material. Such material is often Hastelloy. Furthermore, a welded connection 17 between the corrosion resistant material of the plated layer 16 on the flange 25 and the corrosion resistant material of the sensor pot 12 can be provided. Of course, the plated layer 16 does not necessarily have to be welded with the flange 25. Because of the plated layer 16, which best serves as a suitable sealing surface, the flange 25 same as, in given cases, the connection region 17 between the flange 25 and the sensor pot 11 are protected against corrosion.

[0042] FIG. 2 shows a solution known from the state of the art for corrosion endangered components 24 of a diaphragm seal, in the case of which the solder layer 22 is applied on the sealing surface 21 of a flange 25. Flange 25 and membrane 27 are manufactured of the same material. The solder layer 22 is located also between the sensor bed 26 and the membrane 27. Sensor bed 26 and membrane 27 form a chamber 28 for accommodating a pressure transfer medium 29. The disadvantages of this solution have been described above.

[0043] FIG. 3 shows a solution known from the state of the art, in the case of which the components 34 of a diaphragm seal 37 to be protected against corrosion are protected by means of a corrosion resistant membrane 32. The corrosion resistant membrane 32 is connected via solder 36 and a hard soldering or brazing method and is spread on the area 31 to be sealed. Sensor bed 38 and corrosion resistant membrane 32 form a chamber 37 for accommodating pressure transfer medium 39. Also this solution has disadvantages, which have already been described above.

[0044] FIG. 4 shows a schematic view, which especially illustrates the local sintering/melting of metal particles 60 applied in the case of the method of the invention by means of a laser beam 61. According to the invention, the construction of corrosion resistant coating 45 occurs preferably by means of a selective laser sinter method (SLS). SLS is a generative, layer build-up method, with which the corrosion resistant coating 45 of the invention of a metal or an alloy in any layer thickness, or with any thickness profile, is applied on a portion 44 of a component 41; 42 to be protected against corrosion. An advantage of the layer build-up method of the invention is especially that, by the successive, however, local, melting of the metal particles 60, mechanical stresses, which occur during the following cooling process in the corrosion resistant coating 45, are lower than in the case of the solder or welding methods, which act on a greater area and which are used in the state of the art for applying a coating 45 on a component 41, 42.

[0045] In the visualized case, a functional intermediate layer 46 is located between the component 41; 42 and the coating 45. The functional intermediate layer 46 acts, for example, as a bonding aid and enables a lasting connection between the material of the component 41, 42 and the material of the coating 45. Via a suitable choice of the material of the functional intermediate layer 46, also, e.g., a suitable buffering between different coefficients of expansion of the material of the component 41; 42 and the coating 45 can be achieved.

[0046] In FIG. 4, the granularly shaded regions show unsintered metal particles 60, while the continuously represented regions show the individual layers of the corrosion resistant protective cover layer 45 produced in the layer build up method. The arrow shows the current direction of movement of the laser beam 61.

[0047] FIG. 5 shows a schematic view of the corrosion resistant assembly 40 of a diaphragm seal 47 produced according to the method of the invention. Especially, the assembly 40 is a so-called flange assembly. The flange 52 of the flange assembly 40 isfor reasons of costproduced from a corrodible material. Flange 52 is coated, e.g., via a 3D printing method, especially via an SLS method, in the portion 44 (which can also be referred to as the area 21; 31 to be sealed) with corrosion resistant material. The coating 45 has a predetermined thickness and/or a predetermined thickness profile. Alternatively, it is also possible to apply the coating 45 with a predetermined thickness via a 3D printing method and then to bring it via mechanical material removal methods (grinding, machining, etc.) to the desired thickness and/or the desired thickness profile. Likewise, the surface of the coating 45 can be provided e.g. with a desired roughness by subsequent mechanical processing.

[0048] Applied on the coating 45 is the measuring membrane 48 of corrosion resistant material. The two components 41, 42; 45, 48 are preferably welded together in the connection region 43. Especially a laser welding method is applied for this. Located between the measuring membrane 48 and the sensor bed 26 is a chamber 49. Such is, same as the connecting line 63, filled with pressure transfer liquid 50. The bores 33 in the flange 52 serve for securing the flange assembly 40 on a process flange (not shown).

[0049] The following example serves for purposes of illustration. Of course, instead of the corrosion resistant material, tantalum, also other corrosion resistant materials can be used. The same holds for the material of the corrodible component(s). Likewise the numerical values are examples.

[0050] The coating 45 applied in the 3D printing method on the flange 52 can be as thick as desired, e.g., 0.1-5.0 mm. For many applications, however, a tantalum layer of 0.1-0.5 mm is sufficient completely to avoid corrosion of the component 41; 42 to be protected. The membrane 48 is, e.g., a tantalum foil, which is welded on the coating 45 in the connection region 43, e.g., by laser welding. Tantalum foils can have, for example, a thickness of 0.025 to 0.200 mm. Preferably, the thickness of the tantalum foil is, e.g., 0.10 mm when the coating 45 has a thickness of, e.g., 0.20 mm.

[0051] FIG. 6 is a schematic view of the assembly 40; 53 of a vibronic sensor for determining the fill level, the density and/or the viscosity of a medium 51, wherein the assembly 40; 53 has been produced according to the method of the invention. The two components 41, 42 of the vibronic sensor 53 to be connected, e.g., to be welded together, are a flange 56 of a corrodible material and a sensor element 59 of corrosion resistant material. Sensor element 59 comprises a pot-shaped housing 55, which is sealed on its end region facing the medium 51, thus, on the process side, with a membrane 57. Formed on the membrane 57 is, in given cases, at least one oscillatory tine 58, although vibronic sensors in the form of so-called membrane oscillators are also known.

[0052] Flange 56 is provided with corrosion resistant coating 45 in the region, which candirectly or indirectlycome in contact with a medium 51. The thickness of the coating 45 applied via a 3D printing method is, in such case, so selected and/or structured that in a following joining process, e.g., a welding, of the two components 55, 56 only the corrosion resistant material, or the corrosion resistant materials, are melted and connected with one another. A mixing in of corrodible material into the joined connection region 43 of the two components 41, 42; 55, 56 of the assembly 40 is, thus, safely excluded.

[0053] In summary, advantages of the solution of the invention include the following: [0054] Since the laser welding produces little heat, e.g., an foil-like measuring membrane 48 of a pressure sensor is neither deformed nor distorted after the joining process, especially a welding process. Without problemeasily and safelyalso a forming of the measuring membrane 48, e.g., with a stamp, can be performed. [0055] The coating 45 of a component, e.g., a flange 52, with corrosion resistant material, e.g., tantalum, by means of a 3D printing method enables the construction of any layer thickness. It is possible in the case of a diaphragm seal 47 to weld a relatively thin foil (measuring membrane 48) of corrosion resistant metal, e.g., tantalum, directly on the corrosion resistant coating 45 of the component 52, without that the welding melts the underlying material of the component 52, which is not corrosion resistant, and which would then get mixed in the connection region 43 (weld region) into the corrosion resistant material of the coating 45. In the case of a vibronic sensor 53, the connection between the coating 45 applied on the flange 56 and the end region of the sensor pot 55 occurs far from the medium 51, wherein both the coating 45 as well as also the sensor pot 55 are usually produced of corrosion resistant material. If the latter is not the case, then also here a coating 45 of a suitable thickness, with a suitable thickness profile, can be applied by 3D printing method. [0056] The 3D printing method, especially the SLS method, is a very favorable production method, which is significantly simpler to implement than soldering or CVD coating.

LIST OF REFERENCE CHARACTERS

[0057] 10 components of the sensor element of a vibronic sensor [0058] 11 sensor pot, or tubular housing [0059] 12 oscillatable unit [0060] 13 membrane [0061] 14 tuning fork [0062] 15 tines [0063] 16 plated layer [0064] 17 welded connection [0065] 18 bore [0066] 21 area to be sealed [0067] 22 corrosion resistant coating [0068] 23 bore [0069] 24 components of the sensor element of a diaphragm seal [0070] 25 flange [0071] 26 sensor bed [0072] 27 membrane [0073] 28 chamber [0074] 29 pressure transfer medium [0075] 31 area to be sealed [0076] 32 corrosion resistant membrane [0077] 33 bore [0078] 34 components of the sensor element of a diaphragm seal [0079] 35 flange [0080] 36 solder [0081] 37 chamber [0082] 38 sensor bed [0083] 39 pressure transfer medium [0084] 40 corrosion resistant assembly [0085] 41 first component [0086] 42 second component [0087] 43 connection region [0088] 44 portion [0089] 45 coating [0090] 46 functional intermediate layer [0091] 47 diaphragm seal [0092] 48 measuring membrane [0093] 49 chamber [0094] 50 pressure transfer liquid [0095] 51 medium [0096] 52 flange [0097] 53 assembly of the vibronic sensor [0098] 54 sensor element diaphragm seal [0099] 55 pot-shaped housing/sensor pot [0100] 56 flange [0101] 57 membrane [0102] 58 oscillatory tine [0103] 59 sensor element of the vibronic sensor [0104] 60 metal particles [0105] 61 laser beam [0106] 62 sintered metal particles [0107] 63 connecting duct