Fluid measuring device measuring fluid level in a container at high temperatures and/or high pressures and/or in a chemically aggressive environment using microwaves

• US 6,553,830 B2
• Filed: 11/21/2001
• Issued: 04/29/2003
• Est. Priority Date: 03/18/1998
• Status: Expired due to Term

• Current Assignee: Vega Grieshaber Kb
• Original Assignee: Vega Grieshaber Kb
• Inventors: Rapp, Gunter, Dietmeier, Jurgen, Fahrenbach, Josef, Motzar, Jurgen
• Primary Examiner(s): Larkin, Daniel S.
• Assistant Examiner(s): WILSON, KATINA M
• Application Number:
  US09/990,942
• Publication Number:
  US 20020053238A1
• Time in Patent Office: 524 Days
• Field of Search: 732/90.V, 732/95, 732/99, 733/01, 324/637, 324/92, 324/95
• US Class Current: 73/290.00V
• CPC Class Codes: G01F 23/284 Electromagnetic waves

Abstract

The invention concerns a microwave level measuring device for measuring of material levels in containers, suitable for operation at extreme container conditions, comprising high temperatures, high pressures, and/or chemically aggressive substances.

Claims

1. A measuring device for measuring the level of a material contained within a container through a measurement opening in a wall thereof, comprising:

a housing including an electronics unit providing for the generation and sending of microwave signals and for receiving and measuring characteristics of received microwave signals;

a sending/receiving unit for sending and receiving microwave signals, the sending/receiving unit including a waveguide, a waveguide filling media at least partially contained in the waveguide and an antenna, wherein the waveguide filling media is sealingly positioned in the waveguide for securing the waveguide filling media and the waveguide to a mounting flange thereby forming a pressure proof seal and for assuring that the container pressure impinges upon and is absorbed by the waveguide filling media;

an electrical transmission line connecting the electronics unit and the sending/receiving unit for communicating microwave signals between the electronics unit and the sending/receiving unit; and

a mounting unit having a mounting flange attachable to the wall of the container and surrounding the measurement opening, the mounting unit supporting the sending/receiving unit in communication with the interior of the container for sending and receiving microwave signals through the measurement opening to and from the surface of the material contained within the container.

2. The level measuring device of claim 1 wherein the sending/receiving unit includes sealing materials arranged for axially and/or radially sealing between the waveguide and the waveguide filling media.

3. The level measuring device of claim 2, wherein the sealing materials are selected from one of pressure proof welding connections, metal seals, or graphite seals.

4. The level measuring device of claim 1, wherein the sending/receiving unit includes a two-part sleeve, wherein the waveguide filling media is welded, soldered, or melted into the sleeve, wherein one part of the sleeve includes a material with a heat expansion coefficient commensurate to that of the waveguide, and the sleeve is sealingly connected to the waveguide for a pressure proof seal.

5. The level measuring device of claim 1, wherein the sending/receiving unit includes a taper element at least partially enclosed within the antenna.

6. The level measuring device of claim 5, wherein the waveguide includes a tapered mounting portion, and the taper element is press-molded to the tapered mounting portion.

7. The level measuring device of claim 6, wherein the taper element is press-molded to the taper mounting portion at room temperature.

8. The level measuring device of claim 6, wherein a portion of the taper element that is secured by press molding is surrounded by at least one additional element, the at least one additional element having a lower heat expansion coefficient than the material of the waveguide.

9. The level measuring device of claim 6, wherein the sending/receiving unit includes at least one additional element in the press-molded location between waveguide filling media and waveguide, the at least one additional element includes a material that has a lower heat expansion coefficient than the material of the waveguide, the at least one additional element secures the press-molding of the waveguide filling media.

10. The level measuring device of claim 5, wherein the wavelength includes a tapered mounting portion, and the taper element is thermally or non-thermally press-molded to the tapered mounting portion.

11. The level measuring device of claim 1, wherein the waveguide includes a projection, and the waveguide filling media includes an enlargement, which supports itself on the projection.

12. The level measuring device of claim 11, wherein the enlargement corresponds in axial length to half the wavelength of a conducted microwave signal.

13. The level measuring device of claim 1, wherein the electrical transmission line couples into the waveguide filling media from a side.

14. The level measuring device of claim 1, wherein the mounting unit also supports the housing containing the electronics unit at a mounting location both spatially and thermally isolated from both the sending/receiving unit and the material within the container.

15. The level measuring device of claim 1, wherein a thermal barrier is interposed between the housing and the material in the container, and the transmission line extends through the thermal barrier such that the waveguide filling media does not extend through the thermal barrier.

16. The level measuring device of claim 1, wherein a spacer tube is mounted between the housing containing the electronics unit and the sending/receiving unit;

and

a thermal barrier is mounted in the spacer tube, the thermal barrier comprising at least one separation wall made from material of low thermal conductivity which divides the spacer tube into two consecutive sections between the electronics unit and the mounting unit.

17. The level measuring device of claim 16, wherein the thermal barrier includes tetrafluoroethylene.

18. The level measuring device of claim 16, wherein at least a portion of the electrical transmission line is an air insulated coaxial cable connected between the electronics unit and the waveguide filling media of the sending/receiving unit, the coaxial cable directly coupled into the waveguide filing media.

19. The level measuring device of claim 18, wherein the coaxial cable is placed between the separation wall and the sending/receiving unit.

20. The level measuring device of claim 16, the spacer tube is an air filled waveguide.

21. The level measuring device of claim 20, wherein the waveguide includes at least one microwave permeable separation wall made from material of low heat conductivity which divides the waveguide between the electronics unit and the mounting unite into two consecutive sections.

22. The level measuring device of claim 16, wherein the spacer tube functions as a waveguide for transmission of microwave signals from the proximal end adjacent to the electronics unit to the distal end adjacent to the waveguide sleeve.

23. The level measuring device of claim 1, wherein at least part of the waveguide filling media comprises heatproof material permeable by microwaves.

24. The level measuring device of claim 23, wherein the material comprises glass.

25. The level measuring device of claim 1, wherein the antenna is a horn antenna.

26. The level measuring device of claim 1, wherein the antenna is a thin polyrod antenna coupled to the waveguide filling medium.

27. A measuring device for measuring the level of a material contained within a container through a measurement opening in a wall thereof, comprising:

a housing containing an electronics unit providing for the sending of microwave signals and for receiving characteristics of received microwave signals;

a mounting flange attachable to the wall of the container surrounding the measurement opening, the mounting flange having an aperture therethrough which is aligned in registration with the measurement hole when the flange is attached to the container wall;

a sending/receiving unit for sending and receiving microwave signals, the sending/receiving unit including a waveguide jacket, a waveguide filling media and taper element at least partially contained in the waveguide jacket, and a horn antenna attached at a throat end thereof to a lower face of the mounting flange in registration with the aperture in the mounting flange, the body of the horn antenna depending from the flange and projecting into the container through the measurement hole therein,

the waveguide jacket having an internal bore opening therethrough along an axis thereof and having an external shape at one end thereof for axial insertion into the aperture of the mounting flange, the one end of the waveguide jacket and the one end of the horn antenna forming a pressure tight seal with the lower face of the mounting flange;

the waveguide filling medium and taper element mounted in the internal bore opening of the waveguide jacket with a portion of the exterior walls of the waveguide filling medium being sealingly welded, soldered, or melted into the internal bore opening of the waveguide jacket thereby forming a pressure proof seal and for assuring that the container pressure impinges upon and is absorbed by the waveguide filling medium and the waveguide filling medium having the taper element depending therefrom and projecting below the mounting flange into throat of the horn antenna,

an electrical transmission line connecting the electronics unit and the sending/receiving unit for communicating microwave signals between the electronics unit and the sending/receiving unit; and

a spacer tube attached to the mounting flange; and

a thermal barrier in the spacer tube, the thermal barrier including at least one low thermal conductivity wall that divides the spacer tube into consecutive sections.

28. The measuring device of claim 27, wherein the waveguide jacket is provided with a high pressure fluid tight seal to the mounting flange comprising:

a pressure ring sealingly surrounding the body of the waveguide filling media and taper element and forming a pressure tight seal between the waveguide jacket and the body of the waveguide filling media and the taper element;

a metal seal forming an annulus around the waveguide filling media/taper element, the metal seal being engaged by the pressure ring which is above and adjacent it; and

a pressure screw surrounds the waveguide filling media/taper element and applies pressure to the pressure ring and the metal seal.

29. The measuring device of claim 28, wherein the high pressure seal also includes:

an annular disk surrounding the waveguide filling media/taper above and engaging a top surface of the pressure ring, the annular disk constructed and arranged for arresting twisting of the pressure ring against the metal seal as pressure screw is advanced.

30. The measuring device of claim 27, wherein the waveguide filling media is soldered into a circumferential solder sleeve which engages the inner wall of waveguide jacket.

31. The measuring device of claim 30, wherein a circumferentially disposed band of solder is applied to the waveguide filling media prior to assembly to facilitate forming the high pressure seal.

32. The measuring device of claim 27, wherein the waveguide jacket has at least one portion thereof which is press-fit into a close bond with the waveguide filling media and taper element.

33. The measuring device of claim 27, wherein a ring of low thermal expansion material is slid over at least a portion of the waveguide sleeve to form a press fit for securing the sleeve to the waveguide filling media and taper element.

34. The measuring device of claim 27, wherein the waveguide filling media and taper element have an increased cross section area adjacent the distal end thereof and wherein an inner waveguide sleeve of low thermal expansion material having an internal bore opening therethrough along an axis thereof engages the waveguide filling media inserted in the internal bore thereof.

35. The measuring device of claim 34, wherein a pressure ridge is provided between the inner waveguide sleeve and the waveguide sleeve to provide a tighter pressure seal.

36. The measuring device of claim 27, wherein the waveguide filling media and taper element have an increased cross sectional area adjacent the distal end thereof which forms a pressure ridge for increasing the effectiveness of the seal between the waveguide filler media and the waveguide sleeve.

37. The measuring device of claim 36, wherein the ratio of the area of the waveguide filling media to the ratio of the increased area portion is a multiple of lambda/2 of the nominal signals used in the measurement device.

38. A mounting assembly for a sending/receiving unit of a microwave instrument for the measurement of the level of a material in a substantially closed container having a measurement opening in a wall thereof, comprising

a mounting flange attachable to the wall of the container surrounding the measurement opening, the mounting flange having an aperture therethrough which is aligned in registration with the measurement opening when the flange is attached to the container wall;

a microwave horn attached at a throat end thereof to a lower face of the mounting flange in registration with the aperture in the mounting flange, the body of the horn depending from the flange and projecting into the container through the measurement opening therein;

a waveguide jacket having an internal bore opening therethrough along an axis thereof, at least a portion of the internal bore opening having an insulating window inserted therein, the waveguide jacket having an external shape at one end thereof constructed and arranged for axial insertion into the aperture of the mounting flange, the one end of the waveguide jacket and the one end of the microwave horn forming a pressure tight seal with the lower face of the mounting flange;

a taper element mounted in the internal bore opening of the waveguide jacket with a sealing ring circumferentially surrounding at least a portion of the body of the taper element for sealingly engaging the internal bore opening of the waveguide jacket;

a spacer tube attached to an upper face of the mounting flange; and

a thermal barrier in the spacer tube, the thermal barrier including at least one low thermal conductivity wall that divides the spacer tube into consecutive sections.

39. The assembly of claim 38, wherein the waveguide jacket includes a waveguide filling media and an exciter pin inserted therein for connection to a coaxial cable from an electronics unite, the exciter pin constructed and arranged for converting signals on the cable to microwave signals inside the waveguide filling media.

40. The assembly of claim 38, wherein the taper element is comprised of a polyrod antenna.

41. A measuring device for measuring the level of a material contained within a container through a measurement opening in a wall thereof, comprising:

a housing including an electronics unit generating and receiving microwave signals and measuring characteristics of microwave signals;

a sending/receiving unit sending and receiving microwave signals to and from the material, the sending/receiving unit including a waveguide, a waveguide filling media at least partially contained in the waveguide and an antenna, wherein the waveguide filling media forms a pressure proof seal with the waveguide to assure that container pressure impinges upon and is absorbed by the waveguide filling media;

a mounting unit attachable to the wall of the container and supporting the sending/receiving unit in communication with the interior of the container for sending and receiving microwave signals through the measurement opening to and from the surface of the material;

a spacer tube mounted between the housing and the mounting unit;

a thermal barrier mounted in the spacer tube, the thermal barrier including at least one separation wall made from material of low thermal conductivity which divides the spacer tube into two consecutive sections between the electronics unit and the mounting unit for spatially and thermally isolating the electronics unit from the material; and

a transmission line connecting the electronics unit and the sending/receiving unit for communicating microwave signals between the electronics unit and the sending/receiving unit, wherein the connection of the transmission line and the sending/receiving unit is located in the section communicating with the mounting unit.

42. The measuring device of claim 41, wherein the waveguide filling media is welded to the mounting flange.

43. The measuring device of claim 41, wherein the sending/receiving unit includes sealing materials for axially and/or radially sealing between the waveguide and the waveguide filling media or the waveguide and the mounting flange.

44. The measuring device of claim 41, wherein the sealing materials are selected from one of pressure proof welding connections, metal seals, or graphite seals.

45. The measuring device of claim 41, wherein the sending/receiving unit includes a two-part sleeve, wherein the waveguide filling media is welded, soldered, or melted into the sleeve, wherein one part of the sleeve includes a material with a heat expansion coefficient commensurate to that of the waveguide, and the sleeve is sealingly connected to the waveguide for a pressure proof seal.

46. The measuring device of claim 41, wherein the antenna is a horn antenna.

47. The measuring device of claim 46, wherein the sending/receiving unit includes a taper element at least partially enclosed within the horn antenna, and wherein the taper element is press-molded to a taper mounting portion of the waveguide.

48. The measuring device of claim 47, wherein the taper element is press-molded to the taper mounting portion using thermal or non-thermal press-molding.

49. The measuring device of claim 47, wherein the taper element is press-molded to the taper mounting portion at room temperature.

50. The measuring device of claim 47, wherein a portion of the taper element that is secured by press molding is surrounded by one at least one additional element, the at least one additional element having a lower heat expansion coefficient than the material of the waveguide.

51. The measuring device of claim 47, wherein the sending/receiving unit includes at least one additional element in the press-molded location between waveguide filling media and waveguide, whose material has a lower heat expansion coefficient than the material of the waveguide, the at least one additional element secures the press-molding of the waveguide filling media.

52. The measuring device of claim 47, wherein the waveguide filling media includes an enlargement, which supports itself on a projection of the waveguide.

53. The measuring device of claim 52, wherein the enlargement corresponds in axial length to half the wavelength of a conducted microwave signal.

54. The measuring device of claim 53, wherein a ratio of the area of the waveguide filling media to the ratio of the increased area portion is a multiple of lambda/2 of the nominal signals used in the measurement device.

55. The measuring device of claim 41, wherein the electrical transmission line couples into the waveguide filling medium from a side.

56. The measuring device of claim 41, wherein the waveguide filling media includes a taper element having an increased cross sectional area adjacent the distal end thereof which forms a pressure ridge for increasing the effectiveness of the seal between the waveguide filling media and the waveguide.

57. A sending/receiving unit for sending and receiving a measurement signal into a pressurized container, comprising:

a waveguide jacket having an aperture therethrough;

a waveguide filling media at least partially contained in the aperture of the waveguide jacket, the waveguide filling media being adapted to connect to the waveguide jacket by at least one of soldering, welding, and melting so as to seal the aperture such that pressure from the container impinges on and is absorbed by the waveguide filling media; and

an antenna connected to the waveguide jacket and adapted to direct microwave signals to and from a measurement hole in the container.

58. The sending/receiving unit of claim 57, wherein the microwave horn is adapted to project into the container through the measurement hole therein.

59. The sending/receiving unit of claim 58, wherein the waveguide jacket includes a mounting unit adapted to mechanically lock and pressure seal to the container.

60. The sending/receiving unit of claim 57, wherein the waveguide filling media extends into the antenna.

61. A sending/receiving unit for sending and receiving a measurement signal into a pressurized container, comprising:

a waveguide jacket having an aperture therethrough;

a waveguide filling media at least partially contained in the aperture of the waveguide jacket;

means for sealing the aperture to assure that container pressure impinges upon end is absorbed by the waveguide filling media; and

a microwave horn connected to the waveguide jacket and adapted to direct microwave signals to and from a measurement hole in the container.