Field device for process automation

Abstract

The invention relates to a field device for process automation (1), comprising: - at least one electronics and / or sensor component (20, 30); and - a housing (10) for accommodating the at least one electronics and / or sensor component (20, 30), the housing (10) having a housing body (11), which has a housing wall (12), and a housing chamber (13), which is delimited by the housing wall (12). The at least one electronics and / or sensor component (20, 30) is at least partly provided in the housing chamber (13), and a potting opening (16) is present in the housing wall (12), said potting opening being designed to allow a cannula (71) of a potting filling device (70) to be inserted into the housing chamber (13) in order to introduce a potting compound (40). At least some of the electronics and / or sensor components (20, 30), in particular solely the sensor components (30), are potted by means of the potting compound (40), the potting opening (16) can be gas-tightly closed, and a tightness test of the housing chamber (13) can be carried out via the potting opening (16). A connecting element (17), in particular a ground connection (23) which is connected or can be connected to an electric reference potential, can be paired with the potting opening (16).

Description

[0001] Field device for process automation

[0002] The invention relates to a field device for process automation with a housing.

[0003] Fully welded housings are leak-tested after the welding process. To perform a defined leak test, an opening in the housing is required.

[0004] Furthermore, fully welded housings must have an opening for filling with a potting compound (e.g. a silicone gel) designed to prevent the electronics of the field device from coming into contact with moisture.

[0005] The housing opening of the measuring instrument must be sealed upon delivery and comply with hygienic design guidelines, as exposed sealing elements are unacceptable for food applications due to potential contamination. Conventional sealing elements are often visibly positioned on the outside. A primary distinction is made between elastic molded seals made of plastic and metallic seals. Elastic molded seals require at least two components for sealing. Metallic seals, on the other hand, are a single piece but often feature a ferritic core to maintain sealing force. Elastic molded seals age and must be replaced after a certain period to maintain their sealing effectiveness. Metallic seals, however, are prone to corrosion due to the material used, which is particularly unsuitable for hygienic applications.Furthermore, sealing elements often require separate placement on the housing surface due to accessibility issues.

[0006] Furthermore, a common requirement for field devices in process automation is the ability to connect the often metallic housing to a reference potential (e.g., earth potential).

[0007] The invention is based on the objective of providing a field device that meets the aforementioned requirements and is suitable for hygiene applications.

[0008] The problem is solved by the field device according to claim 1.

[0009] The field device for process automation according to the invention, comprising:

[0010] - at least one electronic and / or sensor component;

[0011] - a housing, in particular fully welded, for accommodating the at least one electronic and / or sensor component, wherein the housing comprises a housing body, in particular metallic, with a housing wall, wherein the housing comprises a housing chamber which is bounded by the housing wall, wherein the at least one electronic and / or sensor component is arranged at least partially in the housing chamber, wherein a potting opening is provided in the housing wall which is configured to allow the insertion of a cannula of a potting filling device for introducing a potting compound into the housing chamber, wherein at least parts of the electronic and / or sensor components, in particular exclusively the sensor components, are potted with the potting compound, wherein the potting opening is gas-tight sealable, and wherein a leak test of the housing chamber can be carried out via the potting opening.wherein a connecting element, in particular a ground connection (23), can be assigned to the potting opening, which itself can be connected to or is connected to an electrical reference potential.

[0012] Advantageous embodiments of the invention are the subject of the dependent claims.

[0013] One embodiment provides that a feedthrough with a through-hole, in particular cylindrically shaped, is arranged in the casting opening, wherein the connecting element can be arranged in the through-hole in a form-fit and / or force-fit manner or is already arranged.

[0014] One embodiment provides that the connecting element seals the through-opening, particularly in conjunction with a sealing element.

[0015] One embodiment provides that the potting opening, in particular the through-hole, is closed with a sealing plug, in particular a (pull) expander.

[0016] One embodiment provides that the feedthrough has a step which reduces the cross-sectional area of ​​the through-opening in the direction of the housing chamber, with the sealing plug, in particular the pull expander, resting against the step.

[0017] One design provides that the sealing plug is made of stainless steel.

[0018] One design provides that the sealing plug is positioned and concealed by the connecting element in such a way that it does not come into contact with splashing water.

[0019] One embodiment provides that a sealing element is arranged at least partially between the connecting element and the feedthrough. Another embodiment provides that the field device is a flow meter for measuring a flow velocity-dependent parameter of a medium, wherein the flow meter comprises a measuring tube for guiding the medium, and wherein the at least one electronic component comprises a measuring, operating, and / or evaluation circuit.

[0020] One embodiment provides that the at least one sensor component comprises a magnetic system which is arranged on an outer lateral surface of the measuring tube, wherein the at least one sensor component comprises at least two measuring electrodes which are each arranged in measuring electrode openings of the measuring tube.

[0021] The invention is explained in more detail with reference to the following figures. They show:

[0022] Fig. 1 : a perspective view of at least a partially cutaway design of a field device for process automation;

[0023] Fig. 2: a section of a cross-section of an embodiment of the field device;

[0024] Fig. 3: a section of a cross-section of a further embodiment of the field device;

[0025] Fig. 4: a representation of a filling process using a potting filling device; and

[0026] Fig. 5: a representation of a leak test.

[0027] Fig. 1 shows a perspective view of a partially cutaway embodiment of a field device 1 for process automation, comprising at least one electronic and / or sensor component 20, 30. The field device for acquiring and / or influencing process variables can be a level gauge, flow meter, pressure and temperature gauge, pH / ORP meter, and / or conductivity meter. Accordingly, the field device can be configured to acquire process variables such as level, flow rate, pressure, temperature, pH value, and / or conductivity. Actuators, such as valves or pumps, are used to influence process variables by 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 and that provide or process process-relevant information are referred to as field devices.In the context of the invention, field devices are understood to include remote I / Os, radio adapters, and, more generally, electronic measuring components arranged at the field level. Flow meters are, in particular, Coriolis, ultrasonic, vortex, thermal, and / or magnetic-inductive flow meters. Level meters are, in particular, radar-based level meters, microwave level meters, ultrasonic level meters, time-domain reflectometric level meters, radiometric level meters, capacitive level meters, inductive level meters, and / or temperature-sensitive level meters. Pressure meters are, in particular, absolute, relative, or differential pressure devices. Temperature meters are, in particular, devices with thermocouples and / or temperature-dependent resistors.Level gauges include, in particular, vibronic level gauges, ultrasonic level gauges, and / or capacitive level gauges. Analytical instruments include, in particular, pH sensors, conductivity sensors, oxygen and active oxygen sensors, (spectro)photometric sensors, and / or ion-selective electrodes.

[0028] The electronic component 20 can be a single component (e.g., a circuit board with electronic elements and connections) of a measuring electronics system for determining a process variable, or a display electronics system for outputting or displaying a determined process value of the process variable.

[0029] Sensor component 30 can be a functional subunit of the sensor that is necessary to determine the process values ​​of the process variable. Depending on the measuring principle, sensor component 30 can be measuring electrodes, a magnetic system, a vortex paddle, sensor coils, excitation coils, pressure transducers, etc.

[0030] Furthermore, the field device 1 includes a housing 10 for accommodating at least one electronic and / or sensor component 20, 30. The housing 10 is designed to accommodate the electronic and / or sensor component 20, 30 and to protect it from external influences.

[0031] The housing 10 comprises a housing body 11 with a housing wall 12. The housing body 11 can be made of a metal, in particular steel or aluminum, a plastic, or a hybrid of plastic and glass fiber. The housing wall 12 at least partially conceals the electronic and / or sensor components 20, 30.

[0032] Furthermore, the housing 10 has a housing chamber 13, which is formed by the housing wall.

[0033] 12 is limited. The housing chamber 13 itself can further comprise sub-chambers, which may be separated by further walls of the housing body 11. Thus, the housing chamber

[0034] The housing chamber 13 comprises a sub-chamber for the electronic component 20 and another sub-chamber for the sensor component 30. Alternatively, the electronic and / or sensor components 20, 30 are arranged at least partially in a common housing chamber 13. According to the invention, a closable potting opening 16 is located in the housing wall 12, which is configured to allow the insertion of a cannula (71) of a potting filling device 70 for introducing a potting compound 40 (see Fig. 4) into the housing chamber (13). The potting compound is configured to fix individual movable components of the field device arranged in the housing chamber 13 in a fixed position. The potting compound can be a silicone gel (WACKER SilGel®). According to the invention, at least a part of the electronic and / or sensor components 20, 30 is potted with the potting compound 40.

[0035] Advantageously, only the sensor components 30 can be encapsulated with the potting compound 40.

[0036] The potting opening 16 can be sealed gas-tight or is already gas-tight. This ensures that no moisture can enter the housing chamber 13 from the outside.

[0037] According to the invention, a leak test of the housing chamber 13 can be performed via the potting opening 16, or, alternatively, the leak tightness of the housing chamber 13 is tested via the potting opening 16 before the field device 1 is set up for the end customer. The leak test comprises a differential pressure measurement using a gas, e.g., air or nitrogen. An overpressure of, e.g., 250 mbar is generated in the housing chamber 13 for a test period, e.g., a time interval of 3 minutes. The leak rate is then measured via the pressure drop during the test period. A suitable leak test can be performed using the F670 differential pressure gauge from ATEQ Germany.

[0038] A connecting element 17, in particular a ground connection 23, can be arranged in the potting opening 16. This connecting element can itself be connected to, or is connected to, an electrical reference potential. The connecting element seals the potting opening 16 gas-tight. The connecting element 17 can comprise a screw or a pin that can be screwed or inserted into the potting opening or a specially provided feedthrough.

[0039] A feedthrough 18 with a through-opening 19, in particular a cylindrical one, can be arranged in the casting opening 16. The connecting element 17 can be arranged in the through-opening 19 in a form-fit and / or force-fit manner. The connecting element 17 is arranged and designed in the through-opening 19 in such a way that it seals the through-opening 19.

[0040] Furthermore, the potting opening 16, in particular the through-opening 19, can be closed with a sealing plug 60, in particular a (tension) expander 61. The sealing plug 60, in particular the (tension) expander 61, is selected and arranged in the through-opening 19 such that it remains stationary at a pressure of 60 bar and retains its sealing properties. The sealing plug 60 can be made of stainless steel. Alternatively, the sealing plug 60 can be positioned and covered by the connecting element 17 in such a way that it does not come into contact with splashing water. In this case, the sealing plug 60 does not have to be made of stainless steel, but can, for example, also be made of carbon steel (unalloyed steel).

[0041] The illustrated embodiment is a flow meter 2 for measuring a flow velocity-dependent quantity of a medium. The flow velocity-dependent quantity can be a volumetric flow rate, a mass flow rate, or a flow velocity. Furthermore, the flow velocity-dependent quantity can also be a quantity dependent on the aforementioned quantities. The flow meter 2 includes a measuring tube 3 for guiding the medium. For operating the flow meter and determining the flow velocity-dependent quantity, the electronic component 20 includes a measuring, operating, and / or evaluation circuit 21.

[0042] In this specific embodiment, the flow meter is a magnetic-inductive flow meter in which the at least one sensor component 30 comprises a magnetic system 31, i.e., a magnetic field-generating device with at least one coil or at least one permanent magnet, which is fixedly arranged on an outer surface of the measuring tube 3. Furthermore, the at least one sensor component 30 comprises at least two measuring electrodes 32, 33, each arranged in measuring electrode openings of the measuring tube 3.

[0043] Fig. 2 shows a section of a cross-section of the configuration of the field device of Fig. 1. A potting opening 16 is located in the housing wall 12, through which the housing chamber 13 is potted with a potting compound. A feedthrough 18 with a through-opening 19, preferably cylindrical, is located in the potting opening 16. The feedthrough 18 is designed as a metallic sleeve that is bonded to the feedthrough 18. The connecting element 17 can be, or is, arranged in the through-opening 19 in a form-fit and / or force-fit manner. The connecting element 17 can be screwed in and arranged in the through-opening in such a way that it seals the through-opening 19.

[0044] The potting opening 16, in particular the through-opening 19, is further closed with a sealing plug 60, in particular a (tensile) expander 61, preferably of metallic origin. The sealing plug 60 can be made of stainless steel, i.e., of a material that does not rust. However, this requirement is not necessary if the sealing plug 60 is positioned and covered by the connecting element 17 in such a way that it does not come into contact with splashing water. For this to be the case, the connecting element 17 must close the through-opening 19 in such a way that no splashing water reaches the sealing plug 60.

[0045] Fig. 3 shows a section of a cross-section of another embodiment of the field device. This embodiment differs from that of Fig. 2 in that a sealing element 50, in particular an elastic one, e.g. an O-ring, is arranged at least partially between the connecting element 17 and the feedthrough 18. The additional sealing element 50 ensures that no splash water reaches the sealing plug 60.

[0046] Fig. 4 shows a representation of a filling process using a potting filling device 70. The potting filling device 70 comprises a cannula 71, which is inserted through the potting opening, in particular into the through-opening 19 of the feedthrough 18.

[0047] Furthermore, the illustrated feedthrough 18 has a shoulder 90 that reduces the cross-sectional area of ​​the through-opening 19 in the direction of the housing chamber 13 or in the longitudinal direction of the through-opening 19. The sealing plug 60, in particular the (pull) expander 61, rests against the shoulder 90. The shoulder 90 limits the insertion depth of the sealing plug 60 and thus prevents the sealing plug 60 from falling into the housing chamber 13 when inserted.

[0048] Fig. 5 shows a representation of a leak test on the bushing 18 of Fig. 4. A leak test device 100 is attached to the bushing 18 and a test pressure of 250 mbar is applied to the bushing 18. This test pressure is monitored over the duration of a test period. If the generated test pressure remains unchanged, the field device passes the leak test.

Claims

PATENT CLAIMS 1. Field device for process automation (1), comprising: - at least one electronic and / or sensor component (20, 30); - a housing (10) for accommodating the at least one electronic and / or sensor component (20, 30), wherein the housing (10) comprises a housing body (11) with a housing wall (12), wherein the housing (10) comprises a housing chamber (13) which is bounded by the housing wall (12), wherein the at least one electronic and / or sensor component (20, 30) is arranged at least partially in the housing chamber (13), wherein a potting opening (16) is provided in the housing wall (12) which is configured to allow the insertion of a cannula (71) of a potting filling device (70) for introducing a potting compound (40) into the housing chamber (13), wherein at least parts of the electronic and / or sensor components (20, 30), in particular exclusively the sensor components (30), are potted with the potting compound (40), wherein the potting opening (16) is gas-tight sealable,wherein a leak test of the housing chamber (13) can be carried out via the potting opening (16), wherein a connecting element (17), in particular a ground connection^), can be assigned to the potting opening (16), which itself can be connected to or is connected to an electrical reference potential.

2. Field device according to claim 1, wherein a feedthrough (18) with a, in particular cylindrically shaped, through-opening (19) is arranged in the potting opening (16), wherein the connecting element (17) can be arranged or is arranged in the through-opening (19) in a form-fit and / or force-fit manner.

3. Field device according to claim 2, wherein the connecting element (17) seals the through-opening (19), in particular in conjunction with a sealing element (50).

4. Field device according to one of the preceding claims, wherein the potting opening (16), in particular the through-hole (19), is closed with a sealing plug (60), in particular a (pull) expander (61).

5. Field device according to one of the preceding claims, wherein the passage (18) has a shoulder (90) which reduces a cross-sectional area of ​​the passage opening (19) in the direction of the housing chamber (13), wherein the sealing plug (60), in particular the tension expander (61), rests against the shoulder (90).

6. Field device according to claim 4 or 5, wherein the sealing plug (60) is made of stainless steel.

7. Field device according to claim 4 or 5, wherein the sealing plug (60) is positioned and covered by the connecting element (17) in such a way that it does not come into contact with splashing water.

8. Field device according to one of the preceding claims, wherein a sealing element (50) is arranged at least sectionally between connecting element (17) and feedthrough (18).

9. Field device according to one of the preceding claims, wherein the field device is a flow meter (2) for measuring a flow velocity-dependent measured quantity of a medium, wherein the flow meter (2) comprises a measuring tube (3) for guiding the medium, wherein the at least one electronic component (20) comprises a measuring, operating and / or evaluation circuit (21).

10. Field device according to claim 9, wherein the at least one sensor component (30) comprises a magnetic system (31) which is arranged on an outer lateral surface of the measuring tube (3), wherein the at least one sensor component (30) comprises at least two measuring electrodes (32, 33) which are each arranged in measuring electrode openings of the measuring tube (3).

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