ASSEMBLY OF A FIELD DEVICE FOR DETERMINING OR MONITORING A PHYSICAL OR CHEMICAL PROCESS VARIABLE

Description

[0001] The invention relates to a field device assembly for determining or monitoring a physical or chemical process parameter of a medium in automation technology, as well as the use of copper, a silver alloy or a copper alloy excluding a nickel-copper alloy as a measuring or separating membrane for a pressure transmitter or sensor assembly.

[0002] In automation systems, particularly process automation systems, field devices are frequently used to detect and / or control process variables. Sensors, such as those integrated into level gauges, flow meters, pressure and temperature gauges, pH / ORP meters, conductivity meters, etc., are used to detect process variables, measuring the relevant process parameters such as level, flow rate, pressure, temperature, pH value, and conductivity. Actuators, such as valves or pumps, are used to control process variables, changing the flow rate of a liquid in a pipe section or the fill level in a container. In principle, all devices used close to the process that provide or process process-relevant information are considered field devices.In the context of the invention, field devices are also understood to include remote I / Os, radio adapters, or generally devices arranged at the field level. A large number of such field devices are manufactured and distributed by Endress+Hauser.

[0003] To detect the pressure of a process medium, so-called pressure transmitters are often used, which have a housing body to which a separating membrane is attached in a pressure-tight manner, forming a hydraulic chamber complex filled with a pressure transmission fluid between the housing body and the separating membrane, whereby a hydraulic path extends through the housing body to transmit the pressure of a process medium at the separating membrane.

[0004] The pressure transmission fluid, usually an oil, enclosed within the hydraulic chamber system, causes the pressure applied to the side of the separating membrane facing the process medium to be transmitted to a pressure sensor element for pressure measurement. To ensure optimal operation of the pressure transmitter over a long service life of several years to several decades, it is crucial that the volume within the pressure transmitter does not change significantly, as this would otherwise distort the pressure being transmitted and thus the pressure measurement.

[0005] Insofar as such adulteration is caused by hydrogen forming internally or diffusing in from the outside, e.g. in the form of hydrogen molecules and / or hydrogen atoms, it is known that precautions are taken to reduce such adulteration.

[0006] For example, DE 10 2013 110 968 A1

[0007] Hydrogen absorption material is provided, which is placed in the enclosed pressure transfer fluid so that hydrogen atoms are absorbed.

[0008] It is also known that, in order to limit diffusion, the membrane is additionally coated. This coating typically consists of electroplated gold or gold-rhodium layers. For efficient diffusion reduction, electroplated layer thicknesses of up to 40 µm (micrometers) are necessary. However, disadvantages of this approach include the relatively high costs due to the relatively thick gold layer, a potential negative change in the mechanical properties of the original separating membrane due to the thickness of the gold layer, and bimetallic effects during temperature changes.

[0009] The invention is based on the objective of providing a remedy for this problem.

[0010] Furthermore, US3422324A discloses a pressure sensor with a diaphragm made of a copper or silver alloy.

[0011] The problem is solved according to the invention by the assembly according to claim 1.

[0012] The inventive assembly of a field device for determining or monitoring a physical or chemical process parameter of a medium in automation technology comprises at least a first component and a second component which are joined together in a connection area, and wherein at least the second component, at least in a partial area which is in contact with the medium in the installed state of the field device, consists entirely of a material selected from the group consisting of copper, a silver alloy or a copper alloy excluding a nickel-copper alloy.

[0013] According to the invention, an assembly is proposed in which the second component, which can be, for example, a measuring or separating membrane, consists exclusively of a material selected from the group consisting of copper, a silver alloy, or a copper alloy excluding a nickel-copper alloy. This means that the second component is designed as a solid component made of one of the aforementioned materials, for example, a solid measuring or separating membrane made of one of these materials. Due to the design of the second component as a solid component made of one of the aforementioned materials, the component exhibits high resistance to hydrogen penetration.

[0014] An advantageous embodiment of the assembly according to the invention provides that the copper alloy comprises a copper beryllium, a copper tin, or a copper zinc alloy and / or the silver alloy comprises a silver copper, a silver nickel, a silver manganese, or a silver copper nickel alloy.

[0015] Another advantageous embodiment of the assembly according to the invention provides that the two components are joined together by soldering or gluing.

[0016] According to the invention, the assembly comprises a third component consisting of another material from the group consisting of copper, a silver alloy or a copper alloy excluding a nickel-copper alloy.

[0017] According to the invention, it is provided that the second component, which in a partial area consists of a material selected from the group consisting of copper, silver alloy, or copper alloy, excluding a nickel-copper alloy, and the third component each represent a single blank which are joined to form a common blank by rolling.

[0018] A further advantageous embodiment of the assembly according to the invention provides that the assembly is a pressure transmitter or sensor body for determining and / or monitoring a pressure of the medium, wherein the second component is a measuring or separating membrane that is in contact with the medium and wherein the first component is a pressure transmitter body or sensor body made of a metallic material, wherein the measuring or separating membrane and the metallic pressure transmitter body are joined together.

[0019] Another advantageous embodiment of the assembly according to the invention provides that the second and third components together form the measuring or separating membrane, which is in contact with the medium.

[0020] The invention further relates to the use of copper, a silver alloy or a copper alloy excluding a nickel-copper alloy as a measuring or separating membrane for a pressure transmitter or a sensor assembly.

[0021] The invention is explained in more detail with reference to the following drawings. They show: Fig. 1 : a first embodiment of the assembly according to the invention, which does not fall within the scope of the claims, Fig. 2 : a second embodiment of the assembly according to the invention, and Fig. 3 : a third embodiment of the assembly according to the invention, which does not fall within the scope of protection of the claims.

[0022] Figure 1Figure 1 shows a first embodiment of the inventive assembly of a field device, which is not within the scope of the claims, for determining or monitoring a physical or chemical process parameter of a medium. A longitudinal section through an inventive assembly in the form of a pressure transmitter is shown. However, it could also be a sensor assembly. The pressure transmitter comprises a pressure transmitter body, preferably metallic, as the first component 10, and a separating membrane as the second component 20 of the inventive assembly. The separating membrane 20 is pressure-tightly joined to an end face of the pressure transmitter body or sensor body along an edge region 22 via a circumferential joining or connection area 40, so that a pressure chamber 11 is formed between the end face of the pressure transmitter body and the separating membrane.On the side of chamber 11 facing away from the separating membrane 20, a membrane bed can also be formed in the pressure transmitter body 10, against which the separating membrane 20 can come into contact in the event of an overload. The pressure chamber 11 can in turn be filled with a transmission fluid, so that, in the assembled state, the pressure of a process medium, which is in contact with the side of the separating membrane 20 facing away from the pressure transmitter body 10, is transmitted by the transmission fluid. The transmission of the pressure can, for example, be effected by a hydraulic path 13 integrated into the pressure transmitter body 10 to a sensor element of the field device arranged remotely from the pressure transmitter. The remotely arranged sensor element, in turn, determines a pressure value as a function of the pressure transmitted by the hydraulic path 13 filled with the transmission fluid. Fig. 1The hydraulic path is shown as an example. This is only necessary in the case of the pressure transmitter and not in the case of the sensor assembly, which is described below.

[0023] Alternatively, as just described, the assembly can also be a sensor assembly 10, 20, consisting of a sensor body 10 as the first component and a measuring membrane 20 as the second component. The sensor body 10 can be designed such that, in the assembled state, i.e., after the measuring membrane 20 has been joined to the sensor body 10 around its perimeter 22, a chamber 11 is formed. In contrast to the previously described example of the pressure transmitter, the chamber 11 in the sensor assembly 10, 20 is not filled with a pressure transmission fluid. Furthermore, unlike the previously described pressure transmitter, the sensor assembly can be directly connected to the process via the measuring membrane 20 (flush mounting). A pressure value can then be determined via the pressure-dependent deflection of the measuring membrane 20 by the medium.In this case, the measuring membrane 20 also serves as a separating membrane, separating the field device to be connected from the medium.

[0024] According to the invention, the diaphragm (separating diaphragm in the case of the pressure transmitter and measuring diaphragm in the case of the sensor assembly) is made exclusively of copper, a silver alloy, or a copper alloy, excluding a nickel-copper alloy (e.g., Monel). The diaphragm is thus designed or manufactured as a solid diaphragm made of at least one of the aforementioned materials. The following copper alloys have proven to be particularly advantageous: a copper-beryllium alloy, a copper-tin alloy, or a copper-zinc alloy. With regard to the silver alloy, a silver-copper alloy, a silver-nickel alloy, a silver-manganese alloy, or a silver-copper-nickel alloy have proven to be particularly advantageous.

[0025] The base body (pressure transmitter body in the case of the pressure transmitter and sensor body in the case of the sensor assembly) 10 can also be formed or manufactured from various corrosion-resistant materials, depending on the application. For example, the base body 10 can be made of a high-alloy quality steel, such as a chromium-nickel steel, in particular 316L. Alternatively, the base body can also be made of a nickel-based alloy, such as AlloyC, or a multiphase alloy, such as Duplex or the like.

[0026] To join the membrane 20 to the base body 10, a diffusion soldering, a brazing, or an adhesive bonding process can be used, for example. Figure 2Figure 1 shows a second embodiment of the assembly according to the invention. The assembly's structure is the same as previously described; the only difference is that the assembly includes a third component 30. According to this embodiment, the second and third components 20 and 30 are each formed as individual discs, which are joined by rolling to form a common disc. The common disc thus forms the measuring or separating membrane. The two individual discs are each made of one of the aforementioned materials.

[0027] Figure 3 shows another embodiment ,which is not within the scope of the claims, the assembly according to the invention, which in turn is designed identically to the first embodiment. The only difference is that the assembly has a third component 21, which is applied to the second component 20 in the form of a coating. This coating is made of a different material than those mentioned above. In principle, the third component 30, in the form of the coating, does not have to be applied to the entire surface of the second component 20, but can also be present only in an area that is in contact with the medium when the field device is installed. Reference symbol list

[0028] 10 First component of the assembly, in particular pressure transmitter or sensor body 11 Pressure chamber 13 Hydraulic path 20 Second component of the assembly, in particular measuring or separating membrane 21 Coating 22 Edge area 30 Third component of the assembly 40 Connection area

Claims

1. A field device assembly for determining or monitoring a physical or chemical process variable of a medium in automation technology, wherein the assembly comprises at least a first component (10) and a second component (20), which are joined together in a connecting area (40), and wherein at least the second component (20) is completely made of a material chosen from the group of copper, a silver alloy or a copper alloy, with the exception of cupronickel, at least in a partial area which is in contact with the medium when the field device is installed, characterized in that the assembly comprises a third component (30), which is made of a different material from the group of copper, the silver alloy or the copper alloy, with the exception of cupronickel, and wherein the second component (20), which is made in a partial area of a material chosen from the group of copper, the silver alloy or the copper alloy, with the exception of cupronickel, and the third component (30) are each a separate round blank which are joined together to make a joint round blank by means of rolling.

2. The assembly as claimed in the preceding claim, wherein the copper alloy comprises beryllium copper, tin bronze or brass, and / or the silver alloy comprises a silver copper, silver nickel, silver manganese or silver copper nickel alloy.

3. The assembly as claimed in one of the preceding claims, wherein the two components (10, 20) are joined together by means of soldering or adhesion.

4. The assembly as claimed in one of the preceding claims, wherein the assembly is a diaphragm seal or a sensor assembly for determining and / or monitoring a pressure of the medium, wherein the second component (20) is a measuring or separating membrane which is in contact with the medium, and wherein the first component (10) is a diaphragm seal body or sensor body which is made of a metallic material, wherein the measuring or separating membrane (20) and the metal diaphragm seal body or sensor body (10) are joined together.