DE20313930U1 - Pressure sensor tube extension equalization device has internal membrane with rounded corrugations fitting matching grooves in outer tube - Google Patents

Abstract

A pressure sensor tube extension equalization device has a stiff outer tube (1) divided into a measurement space and a pressure sensor fluid inlet (3) chamber by a shell membrane (2) with rounded corrugations (4) at the ends fitting into grooves in the outer tube.

Description

-jpfrJNE & PARTNER

TBK Patent POB 20 19 18 80019 Munich

TBK Patent, Bavariaring 4-6, 80336 Munich, Tel.: +49 89 544690, Fax: +49 89 532611 (G3) +49 89 5329095 (G3+G4), postoffice@tbk-patent.de

Patent attorneys

Dipl.-Ing. Reinhard Kinne Dipl.-Ing. Hans-Bernd Pellmann Dipl.-Ing. Klaus Grams Dipl.-Ing. Aurel Vollnhals Dipl.-Ing. Thomas JA Leson Dipl.-Ing. Dr. Georgi Chivarov Dipl.-Ing. Matthias Grill Dipl.-Ing. Alexander Kühn Dipl.-Ing. Rainer Böckelen Dipl.-Ing. Stefan Klingele Dipl.-Chem. Stefan Bühling Dipl.-Ing. Ronald Roth Dipl.-Ing. Jürgen Faller Dipl.-Ing. Hans-Ludwig Trösch Attorneys at Law Michael Zöbisch

8 September 2003 DE 39315

WIKA Alexander Wiegand GmbH & Co. KG Klingenberg/Main, Germany

"Compensation corrugation to compensate for the length expansion of the pipe sensor at

Pipe pressure seals"

Dresdner Bank, Munich Account 3939 844 Bank code 700 800 00 IBAN No.: DE47 7008 0000 0393 9844 00

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UFJ Bank Limited, Düsseldorf J K&.ö)t)047 .* I BlZ 3(H307 0D IBAN-NiiDEOi 3033 CCOOOOOO5000147

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DESCRIPTION

The invention relates to a pipe pressure seal. Pipe pressure seals are installed in pipelines through which the measured medium flows in order to be able to measure the pressure in the pipeline. Such pipe pressure seals have a rigid jacket tube and an elastic membrane sleeve accommodated therein, which is connected to the jacket tube at its ends in a fluid-tight manner. The membrane sleeve divides the interior of the jacket tube into two spaces, a space through which the measured medium flows and an inner space separated from it by the membrane sleeve, which is filled with a pressure seal fluid.

The diaphragm sleeve can be elastically deformed according to the pressure in the medium chamber, thereby displacing the diaphragm seal fluid or increasing the pressure of the diaphragm seal fluid in the associated space between the jacket tube. This pressure change is measured with a pressure-sensitive device.

Particularly in plants in the food and pharmaceutical industries, the pipelines and the pipe pressure seals installed in them are cleaned or disinfected by flushing with hot steam. This autoclaving process with hot steam causes sudden, extreme temperature changes in the membrane sleeve, which is then subjected to corresponding thermal expansion and thus changes in length. However, the membrane sleeve is firmly clamped in place at both ends by the firm connection to the jacket pipe. When the temperature suddenly increases due to the introduction of steam, the membrane sleeve expands considerably, while the jacket pipe cannot initially follow the temperature increase because the jacket pipe is not in direct contact with the medium flowing in the membrane sleeve (hot steam during autoclaving). The very thin membrane, which is usually designed with a thickness in the range of fractions of a millimeter, can

due to thermal expansion, permanent folds, kinks or other deformations can form, which can cause permanent deviations in the measured value display when the system is restarted, i.e. both the zero point position and deviations in the characteristics of the measurement curve. In extreme cases, the formation of folds can also lead to diaphragm rupture.

In contrast, the invention is based on the object of creating a pipe pressure transmitter that can be exposed to rapid temperature increases in the pipeline, such as when flushing with hot steam, without permanent measurement value deviations or damage to the membrane occurring.

The problem is solved with a pipe pressure transmitter having the features of claim 1.

According to the invention, the diaphragm sleeve has at least one ring shaft which serves to compensate for expansion. The ring shaft allows longitudinal expansion of the diaphragm sleeve between the fixed clampings at its two ends. During longitudinal expansion, the base sections of the shaft move towards or away from each other, while the crown region and the base region of the shaft convert this change in length into an increase or decrease in the curvature. If the dimensions are selected so that the entire expected change in length of the diaphragm sleeve is absorbed by elastic deformation of the ring shaft, the expansion process is completely reversible, i.e. when the diaphragm sleeve subsequently shrinks when cooling to the working temperature or after the jacket pipe has reached the same temperature as the diaphragm sleeve, the diaphragm sleeve essentially returns to its original shape, so that the response to the internal pipe pressure again corresponds to the design and/or initial value.

Furthermore, the invention can also be used advantageously in cases where there are larger differences in thermal expansion between man-

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telrohr and diaphragm sleeve due to the materials used, although the jacket tube and the diaphragm sleeve have approximately the same temperature. In this case, the dimensions of the diaphragm sleeve and jacket tube are matched to one another at a design temperature. By using the ring shaft, the operating temperature ranges of certain material pairings can be extended, since the differences in length change are compensated by the ring shaft.

Preferably, the ring shaft has a rounded cross-section in both its crown and base areas. This round shape does not produce any sharp bends or kinks, which could lead to the membrane sleeve breaking at the kink point when subjected to alternating bending stress. In addition, the rounded shape of the shaft enables the bending stress to be better distributed over the length, ensuring that only deformations occur in the purely elastic range.

Preferably, the casing tube has a rounded annular groove corresponding to the annular shaft near at least one of its ends, in which the annular groove is accommodated. The annular shaft is designed as a bulge outward from the tube cross-section of the diaphragm sleeve and the tube cross-section is not narrowed. This prevents the pressure measurement from being impaired by congestion effects and, in addition, the free tube cross-section is maintained so that solid or viscous media can pass through the diaphragm sleeve without clogging.

Alternatively, the ring shaft can also be designed to protrude into the interior of the diaphragm sleeve without giving up its function as expansion compensation.

The ring shaft and, if applicable, the ring groove can be arranged anywhere along the length of the membrane sleeve. Since the membrane sleeves can basically have any cross-section,

but usually have circular-cylindrical end areas for connection to the jacket pipe, it is preferable to form the ring wave in one or both end areas. This can reduce or eliminate the influence of the ring wave on the areas of the diaphragm sleeve that can be deformed for pressure measurement.

Several ring waves can also be formed next to each other at one or both end areas of the membrane sleeve; this depends on the expected change in length and the elasticity of the membrane material.

According to an advantageous embodiment of the invention, a pipe pressure transmitter with a ring shaft in the diaphragm sleeve can be produced by turning one or more rounded ring grooves into the jacket tube at the position or positions provided for the ring shaft(s). The diaphragm sleeve manufactured with excess length is then connected to the jacket tube at one end, e.g. by welding. A rubber cushion is then inserted into this assembly and expanded so that the ring shaft(s) with the ring groove in the jacket tube are embossed into the diaphragm sleeve as a counterpart. Finally, the other end of the diaphragm sleeve is then attached, e.g. by welding. The diaphragm sleeve can also be glued or soldered for attachment; this depends on the material pairing of the diaphragm sleeve/jacket tube.

Alternatively, a membrane sleeve can be used which already has the ring wave(s) embossed and is then installed in the casing tube. When using membrane sleeves made of non-metallic materials (e.g. plastics), the ring waves can also be formed using other processes.

The invention will now be explained in more detail using an embodiment with reference to the drawing.

Fig. 1 an embodiment of a pipe pressure transmitter with a membrane sleeve with two ring shafts; and

Fig. 2 shows schematically an enlargement of detail X from Fig. 1 to show details of the ring shaft.

The pipe pressure transmitter shown in Fig. 1 has a casing pipe 1, a membrane sleeve 2 arranged in the casing pipe 1 and a space filled with pressure transmitter fluid, which can be connected to a pressure measuring device (not shown) via a connection 3. The casing pipe 1 is formed at each of its ends with a flange 13 which has a groove 11 for receiving a seal (not shown). The pipe pressure transmitter is installed in a pipeline (not shown) using the flanges 13.

As can be seen further in Fig. 1, the membrane sleeve 2 extends parallel to the inner wall of the jacket pipe and at a distance therefrom, so that the space for the diaphragm seal fluid is limited between the inner wall of the jacket pipe and the membrane sleeve wall. For this purpose, the middle section of the jacket pipe 1 is slightly enlarged in diameter in order to ensure this space when a circular cylindrical membrane sleeve 2 is used, which is welded to the jacket pipe 1 at its axial ends at 12. In this context, it should be noted that both a circular cylindrical membrane sleeve and other shapes of membrane sleeve can be used. Preferably, all membrane sleeves used have a circular cylindrical attachment area in the connection area to the jacket pipe, with an annular shaft 4 preferably being designed as a rotating annular shaft in this area.

In the pipe pressure seal shown in Fig. 1, a membrane sleeve made of a metallic material is used in a jacket pipe made of a metallic material. Basically,

Other materials can also be used, whereby in this case the connection between the jacket pipe and the membrane sleeve is made of the appropriate material and gluing or other methods are used to create a tight connection. 5

The shape of the annular shaft 4, which is formed on the outer circumference of the diaphragm sleeve 2, is described in more detail with reference to the detail X in Fig. 2.

The ring shaft 4 has two base areas 41 and a crown area 42. As can be clearly seen in Fig. 2, both the crown area 42 and the base areas 41 are designed as rounded sections, i.e. no sharp edges or folds should be formed. This ensures that the spring effect at the bend can be designed in such a way that the deformation of the membrane sleeve there is always in the elastic (i.e. reversible) deformation range.

An annular groove 14 is screwed into the casing tube 1, which is also designed with rounded edges corresponding to the shape of the annular shaft 4. This annular groove 14 can fulfil several tasks, firstly it serves as a membrane bed that supports the annular shaft 4 when high internal pressures occur in the membrane sleeve 2, so that the annular shaft 4 is not permanently deformed even if excessive pressures are accidentally applied and the pipe pressure transmitter is therefore safe from overpressure.

On the other hand, the ring groove 14 can serve directly as a counterpart for the production of the ring shaft 4. For this purpose, a membrane sleeve with a corresponding excess length (compared to the inner length of the jacket tube between the weld seams) is inserted into the jacket tube and preferably initially welded to the jacket tube at one end. A rubber cushion is then inserted into the membrane sleeve and expanded, whereby the membrane material is forced to adhere to the inner wall of the ring groove.

This process embosses the ring wave into the membrane sleeve. After one or more ring waves have been embossed, the membrane sleeve is then welded to the casing tube at the other end.
5

Due to its arched shape, the ring shaft absorbs and compensates for longitudinal expansion of the membrane firmly clamped between the weld seams. This effect is important in cases where the temperature-related longitudinal expansion of the membrane sleeve and the jacket pipe are different from one another. On the one hand, this can be the case with the rapid increase in the temperature of the medium in the pipeline (steam sterilization) described at the beginning, where a temporal deviation in the temperatures of the jacket pipe and membrane sleeve occurs; on the other hand, the longitudinal expansion of the jacket pipe and membrane sleeve can differ from one another at the same temperature due to the material. In some designed in-line pressure seals, the jacket pipe is made of stainless steel (VA) and the membrane sleeve is made of tantalum (Ta). The thermal expansion coefficients (Xva = 16 x 10" ⁶ K" ¹ of VA and Or ₃ = 6.5 x 10" ⁶ K" ¹ of Ta show significant differences, so that with a membrane sleeve length of 10 cm and an operating temperature that is 100 ⁰ C higher than the manufacturing temperature, a length difference of approx. 0.1 mm already occurs. In this case too, the ring shaft has a compensating effect, so that signal shifts are suppressed at increased operating temperatures of the in-line pressure transmitter.

Finally, it should be noted that the ring shaft can also be designed to protrude into the interior of the diaphragm sleeve, or that the ring groove in the wall of the casing pipe can be dispensed with as long as the ring shaft can compensate for expansion. The number and position of the ring shaft or ring shafts can be adapted to suit the intended use of the pipe pressure seal.

Furthermore, rock pressure seals with or without a ring shaft can be manufactured from the same basic components, or the ring shaft can also be subsequently added to existing pipe pressure seals, so that the number of variants can be increased without increasing the number of different components. This can avoid adverse effects on material provision and storage in production.

The concept of the present invention is particularly applicable to a pipe pressure transmitter according to EP 0 629 864 Bl.

Claims (12)

1. Pipe pressure transmitter with a rigid jacket tube ( 1 ) and a diaphragm sleeve ( 2 ) arranged in the jacket tube ( 1 ), which divides the inside of the jacket tube into a measuring fluid space and a chamber for receiving a diaphragm fluid and is deformable following the pressure in the measuring fluid space, characterized in that the diaphragm sleeve ( 2 ) has at least one annular shaft ( 4 ). 2. Pipe pressure transmitter according to claim 1, characterized in that the ring shaft ( 4 ) is rounded in its foot sections ( 41 ). 3. Pipe pressure transmitter according to claim 1 or 2, characterized in that the annular shaft ( 4 ) has an arcuate cross-section. 4. Pipe pressure transmitter according to claim 1, 2 or 3, characterized in that the annular shaft ( 4 ) extends in the direction of the outer circumference of the membrane sleeve ( 2 ). 5. Pipe pressure transmitter according to one or more of the preceding claims, characterized in that the annular shaft ( 4 ) is formed in the axial end region of the membrane sleeve ( 2 ). 6. Pipe pressure transmitter according to one or more of the preceding claims, characterized in that an annular shaft ( 4 ) is formed in the region of each end of the membrane sleeve ( 2 ). 7. Pipe pressure transmitter according to one or more of the preceding claims, characterized in that the jacket pipe ( 1 ) has a receptacle ( 14 ) for the ring shaft ( 4 ) formed on its inner circumference. 8. Pipe pressure transmitter according to claim 7, characterized in that the receptacle is a rounded annular groove ( 14 ). 9. Pipe pressure transmitter according to one or more of the preceding claims, characterized in that the membrane sleeve ( 2 ) has a circular cross-section at least in the region of the annular shaft ( 4 ). 10. Pipe pressure transmitter according to one or more of the preceding claims, characterized in that the membrane sleeve ( 2 ) is made of a metallic material. 11. Pipe pressure transmitter according to claim 10, characterized in that the membrane sleeve ( 2 ) is welded at its ends to the jacket pipe ( 1 ). 12. Pipe sensor for a pipe pressure transmitter according to one or more of the preceding claims, characterized in that the pipe sensor has a membrane sleeve ( 2 ) with at least one annular shaft ( 4 ).