PROTECTIVE TUBE FOR CRYOGENIC APPLICATIONS

Abstract

A protective tube for an apparatus for determining and/or monitoring a process variable of a medium in a containment includes a tubular element for receiving a measuring insert of the apparatus, wherein the tubular element is securable to the containment such that the tubular element extends inwardly into an internal volume of the containment, wherein the tubular element includes an inlet opening and an outlet opening arranged on mutually oppositely lying sides of the tubular element. The present disclosure relates, furthermore, to an arrangement for determining and/or monitoring a process variable of a medium in a containment, the arrangement including an apparatus for determining and/or monitoring the process variable with a measuring insert and a protective tube according to the present disclosure.

Claims

1-13. (canceled)

14. A protective tube for an apparatus for determining and/or monitoring at least one process variable of a medium in a containment, the protective tube comprising: a tubular element configured to receive a measuring insert of the apparatus, wherein the tubular element is securable to the containment such that the tubular element extends, at least partially, inwardly into an internal volume of the containment, wherein the tubular element includes an inlet opening and an outlet opening, wherein the inlet opening and the outlet opening are arranged on mutually oppositely lying sides of the tubular element.

15. The protective tube of claim 14, wherein the inlet opening and/or the outlet opening are arranged and/or configured such that the measuring insert is flowed around by the medium in the tubular element introduced state of the measuring insert.

16. The protective tube of claim 14, wherein the inlet opening and/or the outlet opening are arranged and/or embodied in such a manner that in the containment secured state of the tubular element and in the tubular element introduced state of the measuring insert, a predeterminable stagnation pressure prevails in the region of the inlet opening.

17. The protective tube of claim 14, wherein the inlet opening and/or the outlet opening is/are arranged in the region of a lateral surface of the tubular element.

18. The protective tube of claim 14, wherein the outlet opening is arranged in a first region of the tubular element, wherein in the containment secured state of the tubular element the first region faces the medium.

19. The protective tube of claim 14, wherein the inlet opening is arranged in a second region of the tubular element, wherein in the containment secured state of the tubular element the second region is toward the wall of the containment.

20. The protective tube of claim 14, wherein the tubular element is closed in the region of an end face, which in the containment secured state of the tubular element faces the medium.

21. The protective tube of claim 14, wherein the outlet opening is arranged in the region of the end face, which in the containment secured state of the tubular element faces the medium.

22. The protective tube of claim 14, wherein the end face of the tubular element is chamfered, and the protective tube is securable to the containment such that the chamfering in the containment secured state of the protective tube faces downstream.

23. The protective tube of claim 1, further comprising a securement insert configured to secure a thermometer in a port of a measuring tube and comprising: a holding element configured to secure the thermometer to the securement insert; and a stop, which is embodied to prevent a rotary movement of the thermometer relative to the measuring tube, wherein the securement insert is configured and/or arranged such that the securement insert is movable in parallel with a longitudinal axis of the port.

24. An arrangement for determining and/or monitoring a process variable of a medium in a containment, the arrangement comprising: an apparatus configured to determine and/or monitor the process variable with a measuring insert, which serves for determining and/or monitoring the process variable; and the protective tube according to claim 14.

25. The arrangement of claim, wherein the protective tube and/or the apparatus is/are embodied such that the protective tube and/or the apparatus is/are securable in a receiving nozzle or port of the containment.

26. The arrangement of claim 24, wherein the protective tube is introducible in the containment such that an installed angle between a longitudinal axis of the protective tube and an imaginary, horizontal line lies in the range between 0° and −90°.

Description

[0032] The invention will now be explained in greater detail based on the appended drawing, the figures of which show as follows:

[0033] FIG. 1 a thermometer with protective tube according to the state of the art,

[0034] FIG. 2 a first embodiment of an arrangement of the invention having a protective tube with closed end,

[0035] FIG. 3 a second embodiment of an arrangement of the invention having a protective tube with open end,

[0036] FIG. 4 a third embodiment of an arrangement of the invention having a protective tube with open end and chamfering,

[0037] FIG. 5 a fourth embodiment of an arrangement of the invention having a protective tube with open end and chamfering, and

[0038] FIG. 6 a schematic graph of temperature profile for a protective tube of the invention.

[0039] In the figures, equal elements are provided with equal reference characters. Without intending to limit the general applicability of the idea underlying the invention, the following description concerns measuring arrangements for determining and/or monitoring temperature. Likewise, the following description concerns, by way of example, the case of a containment in the form of a pipeline. Of course, a protective tube of the invention, can, however, also be applied for other types of containments.

[0040] FIG. 1 shows an arrangement 1 for determining and/or monitoring temperature T of a medium M located in a pipeline 2 and flowing through the pipeline 2 with a flow velocity v. Arrangement 1 includes an apparatus 3 for determining and/or monitoring temperature T and provided in the form of a thermometer having a measuring insert 4, in which a temperature sensor (not shown) is arranged. Measuring insert 4 is arranged in a protective tube 5, which is introduced into the pipeline 2 by means of a port 6 provided on the pipeline 2.

[0041] In order to achieve an as high as possible accuracy of measurement, for example, for applications in the low, or cryogenic, temperature field, corresponding arrangements are typically shielded from the environment with insulation. In spite of this, undesired heat conduction can occur in the case of such arrangements, from the environment to the measuring insert. In such case, the securement means, as a rule, composed of metal, for securing the thermometer 3 to the pipeline 2 plays a deciding role. Correspondingly, the measured value ascertained for the temperature is usually too high.

[0042] In the case of applications at cryogenic temperatures, additionally, due to partial vaporization of the medium due to the large temperature differences between temperature of the measuring insert and that of the medium, gas bubbles can form. The gas bubbles move upward and collect in the internal volume of the port. The port is then less or no longer flowed around by liquid medium, in which case it becomes the source of an additional undesired heat input in the case of temperature determination by means of the measuring insert.

[0043] Such problems can be eliminated by means of a protective tube 5 of the invention. A first embodiment of an arrangement 1 with a protective tube 5 of the invention is displayed in FIG. 2.

[0044] The protective tube 5 includes a tubular element 7 with an inlet opening 8 and an outlet opening 9, which are arranged on mutually oppositely lying sides of the tubular element 7. Inlet opening 8 faces upstream relative to the flow v of the medium M in this example of an embodiment, while the outlet opening 9 faces downstream. Tubular element 7 is closed on its end e and the two openings 8,9 are arranged in the region of the lateral surface Is of the tubular element 7. In such case, the inlet opening 8 is in a region near a wall of the pipeline 2, while the outlet opening 9 is in a region near the end face e. In the region of the inlet opening 8, a stagnation pressure p occurs, from which a pressure difference results within the protective tube 5. A forced convection takes place and, associated therewith, a flow through an internal volume of the protective tube 5 and the measuring insert 4. In this way, heat brought from the outside into the process is effectively removed. This, in turn, leads to a significantly increased accuracy of measurement.

[0045] By the optional installation from below, thus, with an angle of essentially 90° between an imaginary horizontal line and a longitudinal axis of the port 6, or protective tube 4, possibly occurring gas bubbles can rise and exit from the protective tube 5 through the outlet opening 9. The occurring vaporization processes have greater heat transfer coefficients than the forced convection of the medium. The removing of the gas bubbles effects, thus, a highly effective cooling of the measuring insert. Ideally, disadvantageous effects of heat introduced from the environment can essentially be completely prevented, because pressure and temperature are directly linked with one another via the vapor pressure curve. This measure cares accordingly for a further increasing of the accuracy of measurement in the case of temperature determination.

[0046] Another example of an embodiment of an arrangement 1 of the invention is presented in FIG. 3. In contrast with the embodiment of FIG. 2, in the case of FIG. 3, the tubular element 7, thus, the protective tube 5, is open in the region of the end face e and the measuring insert 4 extends, by way of example, out of the protective tube 5. Measuring insert 4 is, thus, made longer than the protective tube 5. The outlet opening 9 is located, thus, in the region of the end face e. Moreover, the protective tube has 5, in such case, two inlet openings 8a, 8b. The second inlet opening 8b is located in the state mounted in the pipeline 2 in the region of an internal volume of the port 6. This further lessens negative effects of gas bubbles.

[0047] Because the measuring insert 4 extends out of the protective tube 5, the measuring insert 4 is, especially in the region, in which the temperature sensor is located, directly flowed around by the flowing medium M. Also by these measures, the accuracy of measurement of an arrangement of the invention is increased.

[0048] For preventing vortex induced vibrations, the arrangement 1 further includes a securement insert 10. This includes at least one opening (not shown), in order that the medium M can flow through the internal volume of the protective tube 5 and leave the protective tube 5 through the outlet opening 9.

[0049] In the case of the embodiment of FIG. 4, the end face e is additionally chamfered, wherein the chamfering faces downstream. Also, an installation at an angle other than the 90° of the preceding figures is possible. Such an embodiment is shown by way of example in FIG. 5. Additionally, instead of an arrangement in the form of a T, also an arrangement in the form of an elbow can be implemented. Let it, finally, also be noted that other embodiments also can have more than one outlet opening 9.

[0050] FIG. 6 shows, finally, a schematic view of a temperature profile T as a function of position x in the direction of the longitudinal axis in the case of a vertical installation of the apparatus 3 with the protective tube 5, such as shown in FIG. 4. FIG. 4 shows a vertical line, which allows an associating of the regions a,b,c of the temperature profile with corresponding regions of the arrangement 1. Region a is the region of the port 6, thus, the region of the process connection. Region b is the region within the protective tube 5 and region c is the region facing the medium M, especially that region, where the measuring insert 4 extends out from the protective tube 5.

[0051] While in the region a of the temperature profile, heat conduction is dominant within the process connection, there is a cooling by convection and vaporization in the region b. In region c, the temperature profile is almost independent of the exact position x and the temperature T measured by means of the thermometer 3 corresponds essentially to the temperature of the medium M

Reference Characters

[0052] 1 arrangement [0053] 2 pipeline [0054] 3 apparatus for determining and/or monitoring a process variable [0055] 4 measuring insert [0056] 5 protective tube [0057] 6 port [0058] 7 tubular element [0059] 8 inlet opening [0060] 9 outlet opening [0061] 10 securement insert [0062] M medium [0063] T temperature [0064] v flow velocity [0065] x position along a vertical axis of the arrangement [0066] a,b,c different regions of the arrangement