DE102019118414B4 - Measuring system for radiometric measurement of the density of a medium, mounting device for the radiometric measuring system and method for positioning radiometric radiation sources by means of the mounting device - Google Patents

Abstract

Mounting device (1) for at least two radioactive radiation sources (2) of a measuring system which is used for the radiometric measurement of the density of a medium (4) located in a container (3), comprising: - a fixing device (11) by means of which the mounting device (1) can be fastened to an upper end region (51) of a vertically aligned immersion tube (5) of the measuring system, - a base body (12) with◯ at least one passage (13) whose axis runs approximately parallel to the axis of the immersion tube (5), the passage (13) being designed in such a way as to accommodate the at least two radioactive radiation sources (2) in a row one below the other in relation to the axis, and - a positioning device (14, 16) by means of which the at least two radioactive radiation sources (2) can be positioned both◯ in a row one below the other in the at least one passage (13) and◯ at a respectively defined vertical position within the immersion tube (5). are.

Description

The invention relates to a measuring system and a mounting device for at least two radioactive radiation sources of the measuring system, wherein the measuring system serves for radiometric measurement of the density of a medium in a container. The invention further relates to a method for positioning the radioactive radiation sources by means of the mounting device.

In process automation technology, field devices are often used to record or influence process variables. Appropriate sensors are used in the respective field devices to record the process variables. This allows the individual process variables, such as the fill level, flow, pressure, temperature, pH value, redox potential, density or conductivity, to be recorded. A wide variety of such field device types are manufactured and sold by Endress + Hauser.

In the case of density measurement, field devices are often used whose measuring principle is based on radiometry. This measuring principle has proven particularly effective for media with a high density that are not exclusively liquid or gaseous, but also contain solid phases, such as oil sludge or highly viscous media in general.

In general, the measuring principle of radiometry uses radioactive radiation (preferably gamma radiation from a caesium or cobalt source) that is emitted by a radioactive radiation source and passed through the container with the medium to be measured. After passing through the container, the transmitted radiation intensity is recorded by a radiation detector. The transmitted portion of the emitted radiation intensity is determined by evaluating the corresponding detector signal. This is used to determine the density of the medium.

The intensity of the transmitted radioactive radiation cannot be detected directly after it has passed through the container. To do this, the radioactive radiation must first be converted into electromagnetic radiation in the optical spectral range by a suitable material before the radiation can be detected by a photomultiplier within the radiation detector. Materials that have this property are called scintillating materials. Polystyrene, among others, has this scintillating property. Only radiation in the optical spectral range can be detected by the photomultiplier (whose required operating voltage is several hundred volts to over a kilovolt). The measuring principle of radiometric density measurement is generally state of the art and is described, for example, in the publication WO 2016/124459 A1 described.

Particularly in the case of liquid media with embedded solid phases, such as oil sludge, the measuring principle of radiometry is not only used for point density measurements, but vertical density profiles of the medium are also created along the vertical course in the container. This makes it possible, for example, to identify individual phases of the medium in relation to the height of the container. This takes advantage of the fact that a specific density value range can be assigned to a corresponding, known phase such as oil sand. To create the density profile, not only one radioactive radiation source and one radiation detector arranged horizontally opposite one another are used, but a large number of radioactive radiation sources and corresponding radiation detectors, each arranged vertically at different heights on the container.

In some containers in oil refineries, such as so-called "hydro-cracking reactors", the radioactive radiation sources and the associated detectors are not arranged on the opposite container wall. Instead, the radioactive radiation sources are embedded in a dip tube inside the container so that their distance from the corresponding radiation detectors arranged on the container wall is kept as small as possible. This increases the sensitivity of the density measurement.

To attach or position the radioactive radiation sources in the immersion tube, in practice the radioactive radiation sources are first housed in a mounting device, which in turn can be attached to the upper end of the immersion tube. The mounting device is designed in such a way that the radioactive radiation sources can be lowered into the immersion tube after the mounting device has been attached in order to be positioned at the intended height in the immersion tube. During the subsequent measurement operation of the radiometric measuring system, the mounting device remains attached to the immersion tube, depending on the design, in order to be able to exchange or reposition the radioactive radiation sources if necessary.

Dip tubes used for density measurement in the hydro-cracking process step have a comparatively small nominal diameter of DN 50 as standard, whereby the wall thickness can be reduced due to potentially high process pressures. cke in the container is dimensioned at more than 0.4 mm. This results in a very small dip tube inner diameter of approx. 38 mm. In dip tubes with a small inner diameter, it is particularly difficult to attach or position the radioactive radiation sources one below the other, as the radioactive radiation sources cannot be guided past each other parallel in the dip tube.

The invention is therefore based on the object of providing a mounting device for a measuring system for radiometric density measurement, by means of which the radioactive radiation sources can also be positioned in immersion tubes with a small inner diameter.

• - eine Fixierung, mittels der die Halterungs-Vorrichtung an einem oberen Endbereich eines vertikal ausgerichteten Tauchrohres des Mess-Systems befestigbar ist,
• - einen Grundkörper mit
  • ◯ zumindest einer durch den Grundkörper durchgehenden Durchführung, deren Achse in etwa parallel zur Achse des Tauchrohres verläuft, wobei die Durchführung derart ausgelegt ist, um in Bezug zur Achse die zumindest zwei, insbesondere drei radioaktive Strahlungsquellen untereinander in Reihe aufzunehmen,
  und
• - einer Positionierungs-Einrichtung, mittels der die zumindest zwei radioaktiven Strahlungsquellen sowohl
  • ◯ reihig untereinander in der zumindest einen Durchführung, als auch
  • ◯ an einer jeweils definierten vertikalen Position innerhalb des Tauchrohres positionierbar sind.

The invention solves this problem by means of a mounting device for at least two radioactive radiation sources of a measuring system that is used for radiometric measurement of the density of a medium in a container. According to the invention, the mounting device comprises at least:

• - a fixation by means of which the mounting device can be attached to an upper end region of a vertically aligned immersion tube of the measuring system,
• - a base body with
  • ◯ at least one passage through the base body, the axis of which runs approximately parallel to the axis of the immersion tube, the passage being designed in such a way as to accommodate the at least two, in particular three radioactive radiation sources in series with one another in relation to the axis,
  and
• - a positioning device by means of which the at least two radioactive radiation sources can be
  • ◯ in rows one below the other in at least one passage, as well as
  • ◯ can be positioned at a defined vertical position within the immersion tube.

The advantage of the mounting device according to the invention is that two or more radioactive radiation sources can be accommodated in rows one below the other per feedthrough. As a result, the number of radioactive radiation sources in the immersion tube is not directly limited by its inner diameter or by the outer diameter of the radioactive radiation sources (or the holder in which the radiation sources are encapsulated). The potentially higher number of radioactive radiation sources in turn allows a larger vertical measuring range to be covered in the container, or the vertical resolution of the density measurement can be increased. In order to further increase the number of radioactive radiation sources, it is also possible within the scope of the invention to design the mounting device with not just one, but several feedthroughs, in each of which at least two radioactive radiation sources can be arranged. For example, the mounting device can comprise six feedthroughs, which are arranged in a ring next to one another in relation to the axis of the feedthroughs, analogous to the structure of a revolver magazine.

So that the mounting device protrudes as little as possible beyond the upper end area of the immersion tube when installed, it can preferably be designed so that the base body, at least in the area in which the radioactive radiation sources are accommodated in rows one below the other, has an outer diameter that corresponds at most to the inner diameter of the immersion tube. This means that this area of the mounting device can be accommodated in the upper end area inside the immersion tube. Correspondingly, the fixing of the mounting device in this case should be designed so that the said area is arranged inside the upper end area of the immersion tube when the mounting device is fixed. If the measuring system is intended for use in immersion tubes with a nominal width of DN 50, it is necessary to dimension the outer diameter of the base body in the area of the radioactive radiation sources to a maximum of 38 mm when accommodated inside.

Among other things, for density measurement in hydrocracking reactors, the immersion tube can comprise a flange connection at the upper end area. It is therefore expedient in such applications to design the fixation of the holding device according to the invention accordingly as a flange for this flange connection.

In order to prevent the radioactive radiation sources from jamming when they are lowered from the holder device into the immersion tube, it is advantageous within the scope of the invention if the radioactive radiation sources are each encapsulated in a receptacle whose external cross-sectional shape corresponds approximately to the internal cross-sectional shape of the feedthrough. A round cross-sectional shape is generally preferable.

The positioning device of the holding device, by means of which the radioactive radiation sources can be lowered or picked up, can be realized, for example, by the respective radiation source or its Each receptacle is attached to a rope. The rope is fixed to the upper end of the immersion tube in such a way that the radioactive radiation source is either in the lead-through of the holding device or in the intended vertical position in the immersion tube. To releasably fix the rope to the holding device, the positioning unit can, for example, comprise a corresponding clamp at the upper opening of the respective lead-through in the case of a rope. To ensure that the radioactive radiation source does not tilt when it is taken out of the immersion tube and back into the lead-through of the holding device, any receptacle for the radioactive radiation source in the area of the rope attachment can, for example, be designed with a conical shape that tapers towards the rope.

Since the mounting device according to the invention remains attached to the immersion tube during the measuring operation of the density measuring system, it is advantageous if at least the base body is made of a weather-resistant material such as steel, in particular stainless steel.

• - Ein Tauchrohr,
  • ◯ das ausgehend von einer Oberseite des Behälters in etwa vertikal im Behälter-Inneren anbringbar ist, und
  • ◯ an dem die Halterungs-Vorrichtung über die Fixierung anbringbar ist,
• - zumindest zwei radioaktive Strahlungsquellen, die entweder
  • ◯ reihig untereinander in der zumindest einen Durchführung der Halterungs-Vorrichtung, oder
  • ◯ an einer jeweils definierten vertikalen Position innerhalb des Tauchrohres positionierbar sind,
• - eine den radioaktiven Strahlungsquellen korrespondierende Anzahl an Strahlungs-Detektoren, die
  • ◯ jeweils auf der vertikalen Höhe der entsprechenden, radioaktiven Strahlungsquelle an der Wand des Behälters angeordnet sind, und
  • ◯ die ausgelegt sind, eine eingehende Strahlungs-Intensität der entsprechenden, radioaktiven Strahlungsquelle zu detektieren, und
• - eine Auswertungs-Einheit, die ausgelegt ist, anhand der von den Strahlungs-Detektoren detektierten Strahlungs-Intensitäten die Dichte und/oder das vertikale Dichte-Profil über den vertikalen Bereich der Detektor-Positionen des Mediums zu bestimmen.

A measuring system for radiometric measurement of the density or density profile over the vertical course of the container of a medium located in a container, which is based on the holding device according to the invention, comprises, in addition to the holding device, the following components:

• - A dip tube,
  • ◯ which can be mounted approximately vertically inside the container starting from the top of the container, and
  • ◯ to which the mounting device can be attached via the fixation,
• - at least two radioactive sources, which are either
  • ◯ in rows one below the other in at least one passage of the holding device, or
  • ◯ can be positioned at a defined vertical position within the immersion tube,
• - a number of radiation detectors corresponding to the radioactive radiation sources, which
  • ◯ are arranged at the vertical height of the corresponding radioactive radiation source on the wall of the container, and
  • ◯ which are designed to detect an incoming radiation intensity of the corresponding radioactive radiation source, and
• - an evaluation unit designed to determine the density and/or the vertical density profile over the vertical range of the detector positions of the medium based on the radiation intensities detected by the radiation detectors.

It goes without saying that this measuring system can not only determine the density or a density profile, but also, depending on the design, properties such as the fill level or the limit level, which can be derived from the measured density or the radiation intensity.

• - Anbringen der Halterungs-Vorrichtung am oberen Endbereich des Tauchrohres, wobei die zumindest zwei radioaktiven Strahlungsquellen reihig untereinander in der zumindest einen Durchführung angeordnet sind,
• - Ablassen der unteren, radioaktiven Strahlungsquelle an die jeweils definierte vertikale Position innerhalb des Tauchrohres mittels der Positionierungs-Einrichtung, und
• - Ablassen der oberen, radioaktiven Strahlungsquelle an die jeweils definierte vertikale Position innerhalb des Tauchrohres mittels der Positionierungs-Einrichtung.

By means of the following method steps, the at least two radioactive radiation sources according to the invention can be positioned at the respectively defined vertical position within the immersion tube of this measuring system:

• - Attaching the mounting device to the upper end region of the immersion tube, wherein the at least two radioactive radiation sources are arranged in rows one below the other in the at least one passage,
• - Lowering the lower radioactive radiation source to the defined vertical position within the immersion tube by means of the positioning device, and
• - Lowering the upper radioactive radiation source to the defined vertical position within the immersion tube using the positioning device.

With regard to this method, it is advantageous if the intended position of the lower radioactive radiation source is also located in the immersion tube below the immersion tube position of the upper radiation source. As a result, the upper radioactive radiation source in the feedthrough does not have to be guided past the lower radioactive radiation source in the immersion tube. This principle of positioning can of course also be applied to design variants of mounting devices according to the invention in whose feedthrough(s) more than two radioactive radiation sources are accommodated.

• 1: eine typische Anordnung eines radiometrischen Mess-Systems an einem Behälter,
• 2: eine erfindungsgemäße Halterungs-Vorrichtung für das Mess-System, und
• 3: eine Draufsicht auf die Halterungs-Vorrichtung.

The invention is explained in more detail using the following figures. It shows:

• 1 : a typical arrangement of a radiometric measuring system on a container,
• 2 : an inventive mounting device for the measuring system, and
• 3 : a top view of the mounting device.

In 1 A container 3 is shown in which, for example, as a process step, a reaction in the As part of the oil refinery process, the container 3 can accordingly contain a crude oil or an intermediate product as the filling medium 4, which is not exclusively in liquid or gaseous form, but can also contain various solid phases, such as oil sludge, or impurities such as sand.

In order to be able to locate the different phases of the medium 4 in relation to the height of the container 3, a radiometric measuring system is installed on the container 3, by means of which a density profile of the medium 4 can be determined along the vertical course in the container 3. For this purpose, the measuring system in the embodiment shown comprises twelve radioactive radiation sources 2, which are arranged in an immersion tube 5 inside the container 3. The radiation sources 2 are generally arranged at defined, different heights in the immersion tube 5, so that the desired vertical measuring range of the density profile measurement is covered.

Corresponding to each radioactive radiation source 2, a radiation detector 6 is arranged at approximately the same installation height on the wall of the container 3. The individual radiation detectors 6 thereby measure the radiation intensity of the radioactive radiation that is transmitted through the medium 4 by the associated radioactive radiation source 2. The radiation intensity of the transmitted radiation depends on the density or the respective phase of the medium 4. An evaluation unit of the measuring system can thus use the measured intensity of the transmitted radiation to determine the respective density of the medium 4 that prevails at the height of the corresponding radioactive radiation source 2. In conjunction with the known installation heights of the radioactive radiation sources 2/the radiation detectors 6 (or the known distances from one another), the density profile can be created over the vertical measuring range in the container 3.

Since the value ranges in which the densities of the individual phases lie are usually known from calibration measurements, the evaluation unit of the measuring system can also use the measured densities to determine the individual phases of the medium 4 at the respective installation heights, provided that the value ranges are stored in the evaluation unit.

In order to install or position the radioactive radiation sources 2 in the immersion tube 5, the radioactive radiation sources 2 are in practice first accommodated in a mounting device 1 before the mounting device 1 is attached to the upper end area 51 of the already installed immersion tube 5. The transport of the mounting device to the immersion tube 5 takes place in a special radiation protection container (not in 1 shown).

After fastening the mounting device 1 to the upper end region 51, the radioactive radiation sources 2 are lowered from the mounting device 1 into the immersion tube 5 in order to be able to be positioned at the intended height in the immersion tube 5. During the subsequent measuring operation of the radiometric measuring system, the mounting device 1 remains fastened to the immersion tube 5 in order to exchange or reposition the radioactive radiation sources 2 if necessary.

In the 1 In the measuring system shown, positioning of the six radioactive radiation sources 2 without a special mounting device 1 is difficult, provided that the immersion tube 5 has a small inner diameter that is not larger than approximately four times the outer radius of the radioactive radiation sources 2 or their holder 15 (cf. 2 and 3 ). In this case, the radioactive radiation sources 2 cannot be lowered parallel to each other. In general, the positioning becomes more difficult the more radioactive radiation sources 2 are to be arranged in the immersion tube. In 2 and 3 Therefore, a holding device 1 according to the invention is shown, with which up to twelve radioactive radiation sources 2 can be positioned in the immersion tube 5, even if the immersion tube 5 has a small inner diameter of, for example, less than 38 mm.

The mounting device 1 according to the invention is based on a base body 12, which is made of stainless steel, for example, and which in the embodiment in 2 or. 3 six through-holes 13 extending through the base body 12. As can be seen from 2 As can be seen, the feedthroughs 13 have a straight axis, so that in the feedthroughs 13 two radioactive radiation sources 2 can be arranged in rows one below the other according to the invention. The six feedthroughs, as shown in 3 , are arranged next to one another in a circle, analogous to a revolver magazine. Within the scope of the invention, however, the arrangement of the passages 13 relative to one another is generally not strictly prescribed.

In the 2 and 3 The embodiment of the mounting device 1 according to the invention shown comprises a flange as a fixation 11 on the immersion tube 5 for fastening to the flange connection in the upper end region 51, so that the axes of the bushings 13 are aligned approximately parallel to the immersion tube 5. In 2 is also a possible Variant for the implementation of the positioning device is illustrated: The holder 15 of each radioactive radiation source 2 is attached to a steel cable 14. The cables 14 are to be fixed to the upper end area of the immersion tube 5 in such a way that the two radioactive radiation sources 2 per passage 13 are located in a row one below the other in the holder device 1 before being lowered into the immersion tube 5. In 3 In this regard, it is also shown that in relation to the axis of the feedthroughs 2, a recess 16 can be made at the edge of each of them, in which the cable 14 for the corresponding lower radioactive radiation source 2 is guided. For the detachable fixation of the cables 14 to the mounting device 1, the positioning unit at the upper opening of the respective feedthrough 13 can, for example, comprise a correspondingly designed clamp (not shown in 2 and 3 ).

In order to position the radioactive radiation sources 2 at the desired vertical position within the immersion tube 5 after attaching the mounting device 1 to the immersion tube 5, the respective clamp can be loosened and the length of the respective rope 14 can be adjusted according to the desired vertical position.

The radioactive radiation sources 2 are in the design variant in 2 and 3 encapsulated by receptacles 15, the outer cross-section of which is circular in shape, analogous to the inner cross-section of the bushings 13. This ensures that the radioactive radiation sources 2 are adequately guided without jamming when they are lowered from the holding device 1 and when they are picked up again. In order to avoid jamming, especially when they are picked up again, the receptacles 15 in the area of the rope attachment also have a conical shape that tapers towards the rope 14.

List of reference symbols

1

bracket

2

Radioactive radiation sources

3

container

4

medium

5

Dip tube

6

Radiation detector

11

Fixation

12

Base body

13

execution

14

Rope

15

Recording

16

Rope guide

51

Flange connection

Claims (12)

Mounting device (1) for at least two radioactive radiation sources (2) of a measuring system which is used for the radiometric measurement of the density of a medium (4) located in a container (3), comprising: - a fixing device (11) by means of which the mounting device (1) can be fastened to an upper end region (51) of a vertically aligned immersion tube (5) of the measuring system, - a base body (12) with ◯ at least one passage (13) whose axis runs approximately parallel to the axis of the immersion tube (5), the passage (13) being designed in such a way as to accommodate the at least two radioactive radiation sources (2) in a row with one another in relation to the axis, and - a positioning device (14, 16) by means of which the at least two radioactive radiation sources (2) can be positioned both ◯ in a row with one another in the at least one passage (13), and ◯ at a respectively defined vertical position within the immersion tube (5) can be positioned. Mounting device (1) according to Claim 1 , comprising six passages (13) which are arranged next to one another in a ring shape with respect to the axis of the passages (13). Holding device (1) according to at least one of the preceding claims, wherein the base body (12) is dimensioned with an outer diameter which corresponds at most to the inner diameter of the immersion tube (5), at least in a region in which the radioactive radiation sources (2) can be accommodated in rows one below the other. Mounting device (1) according to Claim 3 , wherein the outer diameter in the area in which the radioactive radiation sources (2) can be accommodated in rows one below the other is a maximum of 38 mm. Mounting device (1) according to at least one of the preceding claims, wherein the fixation (11) is designed as a flange for a flange connection (51) at the upper end region of the dip tube (5). Holding device (1) according to at least one of the preceding claims, wherein the radioactive radiation sources (2) are each encapsulated in a receptacle (15) whose outer cross-sectional shape corresponds approximately to the inner cross-sectional shape of the feedthrough (13). Holding device (1) according to at least one of the preceding claims, wherein the positioning device (14, 16) comprises - a rope (14) to which the respective radioactive radiation source (2) or the receptacle (15) is fastened, and - a clamp for releasably fixing the rope (14) to the holding device (1). Mounting device (1) according to Claim 6 and 7 , wherein the receptacle (15) in the region of the rope fastening has a conical shape tapering towards the rope (14). Holding device (1) according to at least one of the preceding claims, wherein at least the base body (12) is made of a steel, in particular a stainless steel. Measuring system that serves for radiometric measurement of the density of a medium (4) located in a container (3), comprising: - an immersion tube (5) that can be attached approximately vertically in the interior of the container starting from an upper side of the container (3), - a mounting device (1) according to one of the preceding claims that can be fastened to the upper end region (51) of the immersion tube (5) by means of the fixing (11), - at least two radioactive radiation sources (2) that can be positioned either ◯ in rows one below the other in the at least one passage (13), or ◯ at a respectively defined vertical position within the immersion tube (5), - a number of radiation detectors (6) corresponding to the radioactive radiation sources (2), that ◯ are each arranged at the vertical height of the corresponding radioactive radiation source (2) on the wall of the container (3), and ◯ that are designed to incoming radiation intensity of the corresponding radioactive radiation source (2), and - an evaluation unit which is designed to determine the density and/or the vertical density profile of the medium (4) based on the radiation intensities detected by the radiation detectors (6). Measuring system according to Claim 10 , wherein the immersion tube (5) for fastening the mounting device (1) is Claim 6 comprises a flange connection (51) at the upper end area. Method for positioning the at least two radioactive radiation sources (2) at the respectively defined vertical position within the immersion tube (5) by means of the mounting device (1) according to one of the Claims 1 until 9 , comprising the following method steps: - attaching the holding device (1) to the upper end region (51) of the immersion tube (5), wherein the at least two radioactive radiation sources (2) are arranged in rows one below the other in the at least one passage (13), - lowering the lower radioactive radiation source (2) to the respectively defined vertical position within the immersion tube (5) by means of the positioning device (14, 16), and - lowering the upper radioactive radiation source (2) to the respectively defined vertical position within the immersion tube (5) by means of the positioning device (14, 16).

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