MAGNETIC-INDUCTIVE FLOW METER

Abstract

A magnetic-inductive flow meter for determining a flow velocity-dependent measurement variable induced in a flowable medium is provided, said flow meter comprising: a measuring tube for conducting the flowable medium in a flow direction, the measuring tube comprising a carrier body, the measuring tube comprising an inlet region in which the carrier body has a first recess located on an inner side of the carrier body, the first recess extending continuously in the flow direction, the measuring tube comprising a support body for stabilizing a liner, the support body being located between the carrier body and the liner, the support body extending into the first recess and thus being interlockingly connected to the carrier body; a device located on the measuring tube for generating a magnetic field that penetrates the measuring tube; and —two measuring electrodes for tapping a measuring voltage induced in the flowable medium.

Claims

1-15. (canceled)

16. A magnetic-inductive flow meter for determining a flow velocity-dependent measurement variable induced in a flowable medium, comprising: a measuring tube for conducting a flowable medium in a flow direction, wherein the measuring tube comprises a carrier body, wherein the measuring tube comprises an inlet region in which the carrier body has a first recess located on an inner side of the carrier body, wherein the first recess extends continuously in the flow direction, wherein the measuring tube comprises a support body for stabilizing a liner, wherein the support body is arranged between the carrier body and the liner, wherein the support body extends into the first recess and thus is interlockingly connected to the carrier body; a device arranged on the measuring tube for generating a magnetic field that penetrates the measuring tube; and two measuring electrodes for tapping a measuring voltage induced in the flowable medium.

17. The magnetic-inductive flow meter according to claim 16, wherein the first recess is at least partially helical.

18. The magnetic-inductive flow meter according to claim 16, wherein the carrier body in the inlet region at least in part has a wall thickness of less than 7 millimeters.

19. The magnetic-inductive flow meter according to claim 16, wherein the carrier body has an outlet region which comprises a second recess, wherein the second recess is at least partially spiral-shaped.

20. The magnetic-inductive flow meter according to claim 19, wherein the first recess has a first thread direction, wherein the second recess has a second thread direction, wherein the first thread direction is the same as the second thread direction.

21. The magnetic-inductive flow meter according to claim 19, wherein the first recess has a first thread direction, wherein the second recess has a second thread direction, wherein the first thread direction is not the same as the second thread direction.

22. The magnetic-inductive flow meter according to claim 17, wherein the carrier body has a wall thickness, wherein the carrier body in the inlet region has a subregion in which the wall thickness of the carrier body decreases continuously opposite to the flow direction, wherein the first recess extends into the subregion.

23. The magnetic-inductive flow meter according to claim 16, wherein the support body is open-pored.

24. The magnetic-inductive flow meter according to claim 16, wherein the support body is formed from sintered material, in particular from sintered pellets, which are connected to one another by a sintering method and form pores.

25. The magnetic-inductive flow meter according to claim 16, wherein the first recess and/or the second recess has a radial depth of 0.5 millimeters to 2 millimeters.

26. The magnetic-inductive flow meter according to claim 19, wherein the first recess extends exclusively in a first recess region, wherein the second recess extends exclusively in a second recess region, wherein the first recess region and the second recess region, taken together, can be described by a characteristic length in the longitudinal direction, wherein the characteristic length is at least 12% of a total length of the carrier body.

27. The magnetic-inductive flow meter according to claim 17, wherein the spiral-shaped first recess and/or the second recess has a pitch angle α, wherein the pitch angle α is between 0.14° and 4°.

28. The magnetic-inductive flow meter according to claim 17, wherein the support body comprises a support body material, wherein the first recess is filled by the support body material.

29. The magnetic-inductive flow meter according to claim 16, wherein the magnetic-inductive flow meter has a measuring portion in which the carrier body has an opening, and the support body has a receptacle in the form of a recess, for arranging the device for generating the magnetic field on the measuring tube, wherein the device for generating the magnetic field is arranged in the opening and the receptacle.

30. The magnetic-inductive flow meter according to claim 16, wherein the receptacle adjoins flush with the opening, wherein a longitudinal axis of the receptacle runs coaxially with the longitudinal axis of the opening.

Description

[0070] The invention is explained in greater detail with reference to the following Figures. The following are shown:

[0071] FIG. 1: a side view of a partially sectioned embodiment of a magnetic-inductive flow meter according to the invention;

[0072] FIG. 2: an enlargement of the outlet region of FIG. 1;

[0073] FIG. 3: a further enlargement of the outlet region of an embodiment of the magnetic-inductive flow meter according to the invention;

[0074] FIG. 4: a longitudinal section of another embodiment of the magnetic-inductive flow meter according to the invention.

[0075] FIG. 1 shows a side view of a partially sectioned embodiment of a magnetic-inductive flow meter according to the invention. The structure and measuring principle of a magnetic-induction flowmeter are known in principle. A medium having an electrical conductivity is conducted through a measuring tube 1. A device for generating a magnetic field is attached in the measurement segment 16 in such a way that the magnetic field lines are oriented substantially perpendicular to a longitudinal direction defined by the measuring tube axis. The device comprises at least two components. A saddle coil or a coil is preferably suitable as the first component. The second component has a magnetically conductive, in particular soft magnetic material, and comprises a coil core arrangement made of at least one coil core around which a coil wire of the coil is wound, at least one pole shoe arrangement with at least one pole shoe, and/or a field return arrangement consisting of at least two field returns. The pole shoe is inserted into an opening 17 in the carrier body 2. Given an applied magnetic field, a flow-dependent potential distribution arises in the measuring tube 1, which distribution is tapped with two measuring electrodes attached oppositely to the inner wall of the measuring tube 1. As a rule, these are arranged diametrically and form an electrode axis, or are intersected by a transverse axis which runs perpendicular to the magnetic field lines and the longitudinal axis of the measuring tube 1. Using the measured measurement voltage U, the flow rate v and, with additional consideration of the tube cross-sectional area, the volumetric flow rate V of the medium can be determined. In order to prevent the measuring voltage applied to the first and second measuring electrodes 3 from being conducted away via the tube, the inner wall is lined with an insulating material, for example a plastic liner (not depicted in FIG. 1 but depicted in FIG. 4). To fasten the liner, a support body 6 is arranged between carrier body 2 and liner. According to the depicted embodiment, the support body 6 has a material which comprises sintering pellets. The support body 6 is produced by means of a sintering method. For this purpose, a sintering core is inserted into the interior of the carrier body 2, and the cavity formed from the sintering core and the inner lateral surface of the carrier body 2 is filled with sintering pellets. The forming of the support body 6 takes place under increased pressure and/or temperature. After the formation of the support body 6, a flowable liner is applied to the support body 6. The flowable liner runs into the pores of the support body 6, whereby the fastening of the liner to the support body 6 and thus also to the carrier body 2 is realized.

[0076] The magnetic field built up by the device for generating a magnetic field is generated by a direct current of alternating polarity clocked by means of an operating circuit. This ensures a stable zero point, and makes the measurement insensitive to influences due to electrochemical disturbances. A measuring circuit is configured to read out the induced measurement voltage applied to the first and second measuring electrodes, and an evaluation circuit is designed to determine the flow rate v and/or the volumetric flow {dot over (V)} of the medium depending on the measured measuring voltage.

[0077] Commercially available magnetic-inductive flowmeters have two further electrodes in addition to the measurement electrodes. On one hand, a fill level monitoring electrode, which is optimally attached at the highest point in the measuring tube 1, serves to detect partial filling of the measuring tube 1 and is configured to forward this information to the user and/or to take into account the fill level in determining the volumetric flow {dot over (V)}. Furthermore, a reference electrode, which is usually attached diametrically with respect to the fill-level monitoring electrode, or at the lowest point of the measuring tube cross-section, serves to ensure sufficient grounding of the medium. Magnetic-inductive flow meters are known which have an additional temperature sensor which extends into the interior of the measuring tube 1.

[0078] A first recess 4 is incorporated on the inner side 5 in the inlet region 3 of the carrier body 2. The first recess 4 is helical. Furthermore, the outlet region 11 of the carrier body 2 has a second recess 12, which is helical. In the inlet region 3, a subregion 13 is present in which the wall thickness of the carrier body 2 decreases continuously opposite to the flow direction. The first recess 4 extends into the subregion 13. For reasons of symmetry, the outlet region also has a subregion in which the wall thickness of the carrier body 2 decreases continuously in the flow direction and into which the second recess 12 extends.

[0079] According to the depicted embodiment, the material thickness of the support body 6 varies in the flow direction. In the measuring segment of the measuring tube 1, the inner lateral surface of the support body 6 has a cylindrical basic shape. The cross-sectional area of the support body increases steadily in the direction of the inlet and the outlet. The inner lateral surface is designed as a cone in the segment.

[0080] FIG. 2 shows an enlargement of the outlet region 11 of the embodiment depicted in FIG. 1. For reasons of symmetry, the configuration of the outlet region 11 corresponds to the configuration of the inlet region. The outlet region 11 or the second recess region 15 has a subregion 13 in which the wall thickness of the carrier tube 2 decreases in the flow direction. This serves to facilitate the filling of the sintering pellets into the cavity formed by the sintering core and carrier body. The inner lateral surface of the support body has a cylindrical basic shape in the subregion 13. As can moreover be seen, the second recess 12 has a radial depth that varies in the direction of flow.

[0081] FIG. 3 shows a further enlargement of the outlet region 11 of the embodiment from FIG. 1. The first recess and the second recess 12 respectively have a pitch angle α.

[0082] FIG. 4 shows a longitudinal section of another embodiment of the magnetic-inductive flow meter according to the invention. According to the depicted embodiment, the support body 6 has an inner lateral surface whose basic shape is cylindrical. The electrically insulating liner 7 extends on the inner lateral surface. According to the inventive embodiment, the liner 7 is formed from a plastic which is applied in liquid form to the support body and is subsequently cured. By applying the liner 7 in a liquid state, the liner can extend into the pores of the support body produced by the sintering method and thus also catch.

[0083] Two diametrically arranged measuring electrodes 9, 10 are configured to tap a measuring voltage induced in a flowing medium. For this purpose, the measuring electrodes 9, 10 are connected to a measuring circuit (not depicted). The measuring electrodes 9, 10 are arranged in the measuring portion of the measuring tube 1, just like the device for generating a magnetic field 8. This is arranged in an interlocking manner in a receptacle 18 which is formed in the support body 6 and extends through an opening 17 provided in the carrier body 2. The receptacle 18 and opening 17 respectively have a longitudinal axis 21, 22. In the depicted embodiment, the two longitudinal axes 21, 22 are situated atop one another. The receptacle 18 has an edge 23 which adjoins flush with the inner lateral surface of the opening 17.

[0084] The carrier body 2 has a total length 20. The carrier body has a first recess region 14 and a second recess region 15. The first recess region 14 has a first length, and the second recess region 15 has a second length 24. Taken together, the first length and the second length 24 form a characteristic length. The characteristic length corresponds to at least 12% of the total length 20.

[0085] Unlike in the previously depicted embodiment, the inner lateral surface of the carrier body 2 in the first recess region 14 and in the second recess region 15 is formed cylindrically.

LIST OF REFERENCE SIGNS

[0086] 1 Measurement tube [0087] 2 Carrier body [0088] 3 Inlet region [0089] 4 First recess [0090] 5 Inner side [0091] 6 Support body [0092] 7 Liner [0093] 8 Device for generating a magnetic field [0094] 9 Measurement electrode [0095] 10 Measurement electrode [0096] 11 Outlet region [0097] 12 Second recess [0098] 13 Subregion [0099] 14 First recess region [0100] 15 Second recess region [0101] 16 Measuring segment [0102] 17 Opening [0103] 18 Receptacle [0104] 20 Total length [0105] 21 Longitudinal axis of the receptacle [0106] 22 Longitudinal axis of the opening [0107] 23 Edge [0108] 24 Second length [0109] α Pitch angle