Field device with tunable damping arrangement and configuration method

Abstract

Field devices with tunable damping arrangements and methods of configuration are disclosed. A field device (9) for sensing at least one process parameter, the field device (9) comprising: a sensing arrangement (13) configured to provide a sensing signal indicative of the at least one process parameter; a housing (15) at least partially surrounding the sensing arrangement (13); and a vibration damping arrangement (17) comprising an elastomeric member (19) and an anti-vibration weight (21) coupled to the housing (15) via the elastomeric member (19), the anti-vibration weight (21) comprising: a first portion (23) attached to the elastomeric member (19); and a second portion (25) movable relative to the first portion (23) to enable tuning of the vibration damping arrangement (17).

Description

TECHNICAL FIELD

[0001] The present invention relates to a field device for sensing at least one process parameter and to a method of configuring a field device. BACKGROUND

[0002] A field device for sensing at least one process parameter can be subjected to vibrations when in use. Vibrations can be transferred to the field device from a holding structure to which the field device can be attached. Vibrations can be amplified significantly due to resonance.

[0003] It would be desirable to provide an improved field device, in particular a field device with improved vibration damping. SUMMARY

[0004] In view of the above, it is an object of the present invention to provide an improved field device, in particular a field device with improved vibration damping.

[0005] According to a first aspect of the present invention, there is provided a field device for sensing at least one process parameter, the field device comprising: a sensing arrangement configured to provide a sensing signal indicative of the at least one process parameter; a housing at least partially enclosing the sensing arrangement; and a vibration damping arrangement comprising an elastomeric member and an anti-vibration weight coupled to the housing via the elastomeric member, the anti-vibration weight comprising: a first portion attached to the elastomeric member; and a second portion movable relative to the first portion to enable tuning of the vibration damping arrangement.

[0006] The present inventors have found that, depending on the configuration of the field device, the amplification factor during vibration testing of the field device can be as high as 100. To reduce the amplification factor, a vibration damping arrangement can be attached to the housing of the field device.

[0007] The present inventors have realized that improved vibration damping of a field device can be achieved by providing a vibration damping arrangement with tunable damping properties, and that the tunable damping properties can be achieved by providing an anti-vibration weight coupled to the housing of the field device via an elastomeric member as a first portion attached to the elastomeric member and a second portion movable relative to the first portion. Moving the second portion relative to the first portion will change the vibration damping properties of the vibration damping arrangement, and can provide a reduced maximum amplitude of vibration of the field device during vibration testing. The vibration damping arrangement may, for example, surround the housing of the field device, which can provide effective vibration damping in several relevant directions.

[0008] The first portion and the second portion of the anti-vibration weight may, for example, be made of metal, such as stainless steel. Such a material selection can provide a combination of sufficient mass and durability for achieving effective vibration damping.

[0009] The elastomer member can be fixedly attached to the first part of the counterweight, e.g. by bonding. For example, the elastomer member can be made of rubber, e.g. natural rubber, and can be bonded to the first part of the counterweight by vulcanization. Another possibility can be to make the elastomer member of thermoplastic elastomer (TPE).

[0010] According to an example, the vibration damping arrangement can be coupled to the outside of the housing, with the elastomer member arranged between the housing of the field device and the counterweight. This can provide a relatively easy access to the vibration damping arrangement, facilitating tuning of the vibration damping properties of the vibration damping arrangement.

[0011] According to an example, the vibration damping arrangement can comprise an interface member attached to the housing and the elastomer member, a counterweight coupled to the housing via the interface member. The interface member can e.g. be made of metal, e.g. stainless steel. The interface member can be arranged closest to the housing, e.g. in direct contact with the housing, such that vibrations of the interface member are essentially the same as vibrations of the housing of the field device. The elastomer member can be fixedly attached to the interface member, e.g. by bonding. For example, the elastomer member can be made of rubber, e.g. natural rubber, and can be bonded to the interface member by vulcanization. This can provide for a reasonable and efficient production of the field device, as the vibration damping arrangement can be manufactured separately and then coupled with the remaining parts of the field device by a simple coupling process. Examples of suitable coupling processes can be press fit, gluing, welding, snapping, clamping or screwing etc. Furthermore, providing the interface member can allow for increased modularity, as different field device configurations can share the same vibration damping arrangement configuration, or the same interface member can be combined with different elastomer member configurations and / or different counterweight configurations to adapt to different field device configurations.

[0012] According to an example, the vibration damping arrangement can be detachable from the housing of the field device. For example, if the vibration damping arrangement comprises an interface member, the interface member of the vibration damping arrangement can be detachable from the housing of the field device. This can provide for a simplified fine-tuning of the damping spectrum of the vibration damping arrangement. For example, the vibration damping arrangement can be temporarily attached to a fixture having a controllable vibration frequency. A number of frequency sweeps can be performed with the second part of the counter-vibration weight in different positions relative to the first part of the counter-vibration weight, and the most effective position of the second part relative to the first part can be selected. The vibration damping arrangement can then be attached to the housing of the field device. This can provide for an improved damping of vibrations of the field device. Furthermore, for example, if changing process conditions will cause the field device to be subjected to a vibration spectrum having different characteristics, the vibration damping arrangement according to the present example can be temporarily detached from the housing of the field device, and a new fine-tuning can be performed as described above. Alternatively or in combination, the vibration damping arrangement can be replaced with another vibration damping arrangement having different vibration damping characteristics.

[0013] According to an example, the vibration damping arrangement can comprise a locking member operable to lock the first part of the counter-vibration weight and the second part of the counter-vibration weight together to prevent movement of the second part relative to the first part. This can prevent unwanted changes in the vibration damping characteristics of the vibration damping arrangement when a fine-tuning has been performed. For example, the locking member can comprise a set screw.

[0014] According to an example, the field device can extend longitudinally between a first end and a second end defined by the sensing arrangement, and the vibration damping arrangement can be arranged closer to the second end than to the first end. The field device can be generally elliptical, with the sensing arrangement configured to interact with the process at the first end of the field device. For many configurations of such field devices, it has been found that effective vibration damping can be achieved by arranging the vibration damping arrangement closer to the second end of the field device than to the first end of the field device.

[0015] According to an example of such a field device, the second part of the counter-vibration weight can be movable to present different distances between the second part of the counter-vibration weight and the second end of the field device. The distances can be longitudinal distances. The second part of the counter-vibration weight can be linearly movable, or movable by rotating along a helical path. For example, the first and second parts can be threaded.

[0016] According to an example, the field device can comprise an attachment arrangement configured to attach the field device to the holding structure at an attachment interface location; and the vibration damping arrangement can be arranged along the field device closer to the second end than to the attachment interface location. Such positioning of the vibration damping arrangement can provide more effective vibration damping. For even more effective vibration damping, the vibration damping arrangement can be positioned closer to the second end, e.g. spaced apart from the second end less than a quarter of the total distance between the second end of the field device and the attachment interface location. The attachment interface location can be understood as a location along the longitudinal extension of the field device at which the field device mechanically interfaces with the holding structure such that the part of the field device extending from the attachment interface location to the second end can elastically deform relative to the holding structure, which can result in the above-mentioned frequency-dependent amplification of vibrations of the holding structure. The holding structure can be any structure configured to hold the field device in a manner in which the sensing arrangement can interact with the process. For example, the holding structure can be a part of a pipe or tank, or a holder on a dam or river, etc.

[0017] According to an example, the second end can be spaced apart from the attachment interface location by at least 80 mm.

[0018] According to an example, the second end can be spaced apart from the attachment interface location by at least 160 mm.

[0019] In some applications, e.g. in the case of high-temperature processes, a relatively large distance between the attachment interface location and the second end of the field device can be required to enable positioning of heat-sensitive equipment, e.g. measurement electronics, sufficiently far away from the high-temperature process. This can require even more effective vibration damping, which can be provided by arranging the vibration damping arrangement relatively close to the second end of the field device and / or adapting the vibration damping arrangement to the configuration of the field device.

[0020] According to an example, the vibration damping arrangement can be substantially cylindrical. This can be advantageous to provide uniform vibration damping in all directions perpendicular to the cylindrical axis of the vibration damping arrangement. Such a configuration of the vibration damping arrangement can be particularly suitable for field devices having a substantially cylindrical housing.

[0021] According to an example, the field device can be configured for attachment to a tank in a manner in which the sensing arrangement is at least partly inside the tank and the vibration damping arrangement is outside the tank.

[0022] According to a second aspect of the application, there is provided a method of configuring a field device having a housing, the method comprising: providing a field device; providing a vibration damping arrangement, the vibration damping arrangement comprising: an interface member configured to be attached to the housing of the field device; an elastomeric member attached to the interface member; a first portion of an anti-vibration weight attached to the elastomeric member such that the first portion of the anti-vibration weight is coupled to the interface member via the elastomeric member; and a second portion of the anti-vibration weight movably attached to the first portion of the anti-vibration weight; frequency tuning the vibration damping arrangement; and securing the vibration damping arrangement to the field device by attaching the interface member of the vibration damping arrangement to the housing of the field device. The frequency tuning can be performed by moving the second portion of the anti-vibration weight relative to the first portion of the anti-vibration weight.

[0023] According to an example, tuning the vibration damping arrangement can comprise: temporarily attaching the interface member of the vibration damping arrangement to a fixture having a controllable vibration frequency; sweeping the vibration frequency of the fixture; and moving the second portion of the anti-vibration weight. BRIEF DESCRIPTION OF DRAWINGS

[0024] These and other aspects of the present application will now be described in more detail, with reference to the appended drawings showing example embodiments of the application, wherein:

[0025] Figure 1 An example application to a field device according to an embodiment of the application is schematically illustrated;

[0026] Figure 2 is a schematic illustration of a field device according to an example;

[0027] Figures 3A-3B A field device having different settings of vibration damping arrangements according to examples is schematically illustrated;

[0028] Figure 4 is an example of a vibration damping arrangement;

[0029] Figure 5 is a flowchart of a method according to an example;

[0030] Figure 6 Tuning of a vibration damping arrangement is schematically illustrated; and

[0031] Figure 7 is a graph showing an example of the effect of a vibration damping arrangement. DETAILED DESCRIPTION

[0032] Figure 1 An example application to a field device according to an embodiment of the application is schematically illustrated. Reference is made to Figure 1The process tank 1 has an inlet 3, an outlet 5, an agitator 7, and a field device 9 in the form of a vibrating fork. In Figure 1 the example arrangement in, the field device 9 is arranged and configured to function as a limit switch, indicating when the level of the product 11 in the tank 1 rises to and exceeds the level of the field device 9. It should be understood that the tank 1 can be provided with at least one additional field device in the form of a vibrating fork, and such field device can be configured to determine a change in one or more other properties of the product 11 in the tank 1. Examples of such properties can include, for example, the density and / or viscosity and / or composition of the product 11, which can be a mixture of materials. Since methods for determining changes in such various properties based on changes in the vibration characteristics of the vibrating fork tines are known per se to the person of ordinary skill in the relevant art, a detailed description of such methods is omitted. The tank 1 can be provided with additional or other field devices not shown in, such as one or more level meters, and / or one or more flow sensors, and / or one or more pressure sensors, and / or one or more temperature sensors, etc. Figure 1

[0033] The process (e.g. the process exemplified in Figure 1 ) can comprise various sources of vibrations. Such sources of vibrations can include, for example, one or more pumps, the flow of fluid through the inlet 3 and / or the outlet 5, the agitator 7, and other internal or external sources of vibrations. Vibrations from the sources of vibrations can propagate to the holding structure 10 to which the field device 9 is attached. In the example process of Figure 1 , the holding structure 10 is provided as a threaded hole in the wall of the tank 1. However, it should be noted that many other holding structures are possible, depending on the application. Thus, vibrations from the sources of vibrations are transmitted to the field device 9 via the holding structure 10. Due to the longitudinal extension of the field device 9 and the mechanical properties of the field device 9, the vibrations of the field device 9 can be amplified at least at and around the resonance frequency of the field device 9. In order to avoid damage to the field device 9 and / or to comply with requirements, it would be desirable to reduce the amplification of the vibrations of the field device 9. This can be achieved by the field device according to the examples of the present invention.

[0034] Figure 2 is a schematic illustration of a field device 9 according to an example, the field device comprising a sensing arrangement 13, a housing 15, and a vibration damping arrangement 17. The sensing arrangement 13 can comprise at least one sensing actuator (exemplified by tines 14a-b in Figure 2 ) and a sensing controller for controlling the operation of the sensing actuator. The sensing controller is exemplified by Figure 2 ​The measuring electronics 16 are represented in the diagram. The sensing arrangement 13 is configured to provide a sensing signal indicating at least one process parameter, which in this particular example may be the presence or absence of a product around the teeth 14a to 14b of the sensing arrangement 13. The housing 15 at least partially surrounds the sensing arrangement 13. Figure 2 In the example configuration, housing 15 surrounds measuring electronics 16. Vibration damping arrangement 17 includes an elastomer member 19 and an anti-vibration counterweight 21 coupled to the exterior of housing 15 via the elastomer member 19. Anti-vibration counterweight 21 includes a first portion 23 attached to the elastomer member 19 and a second portion 25 movable relative to the first portion 23. Vibration damping arrangement 17 can be tuned to suppress vibrations of field device 9 at different frequencies by moving the second portion 25 along the longitudinal axis 24 of field device 9. Coarse adjustment can be performed by replacing the second portion 25 with a lighter or heavier second portion, or additional second portions can be added. Fine adjustment can be performed by moving the second portion 25 (or multiple second portions) relative to the first portion 23 along the longitudinal axis 24 of field device 9.

[0035] As in Figure 2 As schematically shown, the field device 9 extends longitudinally (along the longitudinal axis 24) between a first end 27 and a second end 29 defined by the sensing arrangement 13. For effective vibration damping, the vibration damping arrangement 17 can be arranged closer to the second end 29 than it is from the first end 27. Furthermore, the second portion 25 of the anti-vibration counterweight 21 is movable to present a different distance between the second portion 25 of the anti-vibration counterweight 21 and the second end 29 of the field device 9.

[0036] according to Figure 2 The example field device 9 includes an attachment arrangement 33, which is arranged in the form of a threaded connection and is configured to attach the field device 9 to a retaining structure (e.g., Figure 1 The corresponding threaded connection 10 is in the wall of tank 1. The attachment arrangement 31 is configured to attach the field device at attachment interface location 33, which defines the interface between the structure and the field device 9 in the longitudinal direction (along the longitudinal axis 24). At attachment interface location 33, the maximum amplification factor of the vibration amplitude is 1. As the distance from attachment interface location 33 increases, the maximum amplification factor of the amplitude increases toward the second end 29 of the field device 9. Therefore, the vibration damping arrangement can advantageously be arranged closer to the second end 29 than from attachment interface location 33.

[0037] Figures 3A-3B The field equipment 9 is schematically shown with different vibration damping arrangements 17 according to the example. Figure 3A The field equipment 9 in the reference is basically the same as the one mentioned above. Figure 2The field device 9 described corresponds. The distance between the second end 29 of the field device 9 and the attachment interface location 33 of the field device can be, for example, at least 80 mm, such as about 100 mm. This configuration of the field device 9 results in vibrations having a particular spectrum characterized by a first resonance frequency and a first maximum amplification factor.

[0038] Figure 3B The field device 9 in Figure 3A The main difference between the field devices in Figure 3B The field device 9 in has been provided with an extension 35 for separating the measurement electronics 16 from the high-temperature process. Due to the extension 35, Figure 3B The distance between the second end 29 of the field device 9 and the attachment interface location 33 in can be, for example, at least 160 mm. This configuration of the field device 9 results in vibrations having a particular spectrum characterized by a second resonance frequency and a second maximum amplification factor, which can be different from the spectrum of the field device in Figure 3A

[0039] Due to the difference in distance between the second end 29 of the field devices in Figure 3A and Figure 3B These field devices can therefore require differently tuned vibration damping arrangements 17 due to the difference in distance between the second end 29 of the field devices and the attachment interface location 33 in Figure 3A and Figure 3B This is schematically indicated in by the different positions of the second portion 25 of the counter-vibration weight 21 relative to the first portion 23 of the counter-vibration weight 21 in

[0040] Figure 4 is a part cutaway perspective view of an example of a vibration damping arrangement 17. In this example configuration, the vibration damping arrangement 17 comprises an interface member 37 configured to be attached to the housing 15 of a field device 9, such as the field device 9 described above with reference to Figure 2 and Figures 3A-3B As schematically shown in Figure 4 the interface member 37 is attached to an elastomer member 19, which in turn is attached to the first portion 23 of the counter-vibration weight 21. As schematically indicated in Figure 4 the vibration damping arrangement 17 according to this example configuration additionally comprises a locking member 39 operable to lock the first portion 23 and the second portion 25 of the counter-vibration weight 21 together. In Figure 4 ​In particular embodiments, the locking member 39 is exemplified as a set screw. The interface member 37 can be attached to the housing 15 using various attachment methods known to those of ordinary skill in the art. Examples include the following: attaching the interface member 37 using one or more fasteners; clamping the interface member 37 to the housing 15; attaching the interface member 37 by interference fit or using an adhesive; etc. It can be advantageous to select an attachment method that enables the interface member 37 to be detached from the housing 15.

[0041] Figure 5 is a flowchart of a method according to an example, the method comprising first providing S51 a field device 9 having a housing 15, and providing S52 a vibration damping arrangement 17, the vibration damping arrangement comprising: an interface member 37 configured to be attached to the housing 15 of the field device 9; an elastomeric member 19 attached to the interface member 37; a first portion 23 of an anti-vibration weight 21 attached to the elastomeric member 19 such that the first portion 23 of the anti-vibration weight 21 is coupled to the interface member 37 via the elastomeric member 19; and a second portion 25 of the anti-vibration weight 21 movably attached to the first portion 23 of the anti-vibration weight 21.

[0042] After the field device 9 and the vibration damping arrangement 17 have been provided, the method proceeds to frequency tuning S53 the vibration damping arrangement 17.

[0043] In Figure 6 An exemplary way of frequency tuning the vibration damping arrangement 17 is schematically illustrated in. Referring to Figure 6 , the vibration damping arrangement 17 can be attached to a fixture 41, which can have similar dimensions as the field device 9. The fixture can be attached to a controllable exciter 43 controlled by an evaluation unit 45. In order to enable evaluation of the vibration spectrum of the fixture 41, the fixture can be provided with a vibration detector 47. The evaluation unit 45 can receive information about the vibrations of the fixture from the vibration detector 47.

[0044] The evaluation unit 45 can control the exciter 43 to scan the vibration frequencies of the fixture 41. The vibration spectrum can be recorded, and the vibration damping arrangement 17 can be frequency tuned by moving the second portion 25 of the anti-vibration weight 21 relative to the first portion 23 of the anti-vibration weight 21. It can also be included in the frequency tuning S53 to replace the second portion 25 and / or add additional second portions 25 before fine-tuning by moving the second portion(s) 25 relative to the first portion 23.

[0045] After the vibration damping arrangement 17 has been tuned, the vibration damping arrangement 17 can be fixed S54 to the field device 9 by attaching the interface member 37 of the vibration damping arrangement 17 to the field device 9.

[0046] Reference will now be made to Figure 7 An example effect of the vibration damping arrangement 17 will be described. Figure 7 is a double-log plot of the amplification factor AF as a function of the vibration frequency f. Figure 7 The solid curve 49 in Fig. 4 shows an example of the amplification factor AF as a function of the frequency f for an example field device 9 without a vibration damping arrangement 17. This curve 49 can for example be obtained using the settings shown in Fig. 3. As can be seen in Fig. 4, the undamped field device 9 exhibits a maximum amplification factor of about 100 at the resonance frequency f r of the field device 9. Figure 6 The dashed curve 51 in Fig. 5 shows an example of the amplification factor AF as a function of the frequency f for an example field device 9 with a tuned vibration damping arrangement 17. This curve 51 can also for example be obtained using the settings shown in Fig. 3. As can be seen in Fig. 5, the damped field device 9 exhibits a maximum amplification factor of less than 10. Figure 7

[0047] Figure 7 The dashed curve 51 in Fig. 5 shows an example of the amplification factor AF as a function of the frequency f for an example field device 9 with a tuned vibration damping arrangement 17. This curve 51 can also for example be obtained using the settings shown in Fig. 3. As can be seen in Fig. 5, the damped field device 9 exhibits a maximum amplification factor of less than 10. Figure 6 Figure 7

[0048] The person skilled in the art realizes that the present invention is in no way limited to the preferred embodiments described above. On the contrary, many modifications and variations are possible within the scope of the appended claims.​​​

Claims

1. A field device (9) for sensing at least one process parameter, the field device (9) comprising: a sensing arrangement (13) configured to provide a sensing signal indicative of the at least one process parameter; a housing (15) at least partially enclosing the sensing arrangement (13); and a vibration damping arrangement (17) comprising an elastomeric member (19) and an anti-vibration weight (21) coupled to the housing (15) via the elastomeric member (19), the anti-vibration weight (21) comprising: a first portion (23) attached to the elastomeric member (19); and a second portion (25) movable relative to the first portion (23) to enable tuning of the vibration damping arrangement (17).

2. The field device (9) of claim 1, the vibration damping arrangement (17) being coupled to an exterior of the housing (15).

3. The field device (9) of claim 1 or 2, the vibration damping arrangement (17) comprising an interface member (37) attached to the housing (15) and the elastomeric member (19), the anti-vibration weight (21) being coupled to the housing (15) via the interface member (37).

4. The field device (9) of claim 3, the vibration damping arrangement (17) being detachable from the housing (15).

5. The field device (9) of claim 1 or 2, the vibration damping arrangement (17) comprising a locking member (39) operable to lock the first portion (23) of the anti-vibration weight (21) and the second portion (25) of the anti-vibration weight (21) together.

6. The field device (9) of claim 5, the locking member (39) comprising a set screw.

7. The field device (9) of claim 1 or 2, the field device (9) extending between a first end (27) and a second end (29) defined by the sensing arrangement (13); and the vibration damping arrangement (17) being arranged closer to the second end (29) than to the first end (27).

8. The field device (9) of claim 7, the second portion (25) of the anti-vibration weight (21) being movable to present different distances between the second portion (25) of the anti-vibration weight (21) and the second end (29) of the field device (9).

9. The field device (9) of claim 7, the field device (9) comprising an attachment arrangement (31) configured to attach the field device (9) to a holding structure (10) at an attachment interface location (33); and the vibration damping arrangement (17) being arranged closer to the second end (29) than to the attachment interface location (33).

10. The field device (9) of claim 9, the second end (29) being spaced apart from the attachment interface location (33) by at least 80 mm. ​ 11. The field device (9) according to claim 10, the second end (29) being spaced apart from the attachment interface location (33) by at least 160 mm.

12. The field device (9) according to claim 1 or 2, the vibration damping arrangement (17) being substantially cylindrical.

13. The field device (9) according to claim 1 or 2, the field device (9) being configured for attachment to a tank (1) with the sensing arrangement (13) at least partially inside the tank (1) and the vibration damping arrangement (17) outside the tank (1).

14. A method of configuring a field device (9) having a housing (15), comprising: providing (S51) the field device (9); providing (S52) a vibration damping arrangement (17), the vibration damping arrangement comprising: an interface member (37) configured to be attached to a housing (15) of the field device (9); an elastomer member (19) attached to the interface member (37); a first portion (23) of an anti-vibration weight (21) attached to the elastomer member (19) such that the first portion (23) of the anti-vibration weight (21) is coupled to the interface member (37) via the elastomer member (19); and a second portion (25) of the anti-vibration weight (21) movably attached to the first portion (23) of the anti-vibration weight (21); tuning (S53) the vibration damping arrangement (17); and fixing (S54) the vibration damping arrangement (17) to the field device (9) by attaching the interface member (37) of the vibration damping arrangement (17) to the housing (15) of the field device (9).

15. The method of claim 14, wherein, tuning (S53) the vibration damping arrangement (17) comprises: temporarily attaching the interface member (37) of the vibration damping arrangement (17) to a fixture (41) having a controllable vibration frequency; scanning the vibration frequency of the fixture (41); and moving the second portion (25) of the anti-vibration weight (21).

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