Clamp-on pressure measuring device

Abstract

The invention relates to a clamp-on pressure measuring device (1) for detecting the pressure in a pipeline (2), the pressure measuring device being constructed in layers consisting of a contact pressure part (10), a decoupling element (11), at least one strain gauge (12), a coupling element (13), an evaluation unit, and a clamping device (14). The decoupling element (11) is suitable for transferring the contact pressure generated by the clamping device (14) in the radial direction to the at least one strain gauge (12) and thus ensuring a force-fitting and / or form-fitting connection between the at least one strain gauge (12), the coupling element (13), and the pipeline surface (2a) while allowing a freedom of movement in the longitudinal and circumferential direction of the pipeline (2), and the coupling element (13) is suitable for transferring a pipeline surface (2a) deformation, resulting from the pressure in the interior of the pipeline (2), to the at least one strain gauge (12).

Description

[0001] Clamp-on pressure gauge

[0002] The invention relates to a clamp-on pressure measuring device for detecting a pressure prevailing in a pipeline.

[0003] Pressure gauges or pressure sensors are used in many industrial sectors for pressure measurement. They often consist of a pressure sensor, which acts as a transducer for the process pressure, and evaluation electronics for signal processing. The pressure sensors detect the pressure either capacitively or resistively.

[0004] In industrial process engineering, pressure, flow, and temperature measurement devices are primarily integrated into existing piping systems. Besides individual measuring instruments, it is also known in pressure measurement technology to permanently and directly apply strain gauges to the surface of pipelines or tools. Examples of this can be found in the German patent applications EP 2 352 902 B1, DE 102020 105 712 A1, and DE 102017 125 724 A1.

[0005] It is already common practice to design ultrasonic flowmeters as clamp-on devices. The advantage of these clamp-on devices lies in their ease of use. Unlike permanently integrated flowmeters, these clamp-on flowmeters can simply be attached to a suitable pipe section from the outside. This pipe section, to which the clamp-on device is attached, effectively becomes the measuring pipe, eliminating the need to insert a separate measuring pipe into the piping system or to create an opening in the wall of the existing measuring pipe for inserting the device. This makes the use of clamp-on ultrasonic flowmeters simple and cost-effective.

[0006] However, implementing such a measuring device in the field of pressure measurement technology is considerably more difficult. The main reason for this is the reliable transmission of mechanical stresses from the pipeline to the strain gauge(s).

[0007] The object of the invention is to propose a pressure measuring device that can be easily attached to the wall of a pipeline as a clamp-on measuring device and reliably determines measured values ​​of the pressure prevailing inside the pipeline.

[0008] The problem is solved according to the invention by a pressure measuring device having the features of claim 1. Advantageous embodiments of the invention are specified in the dependent claims.

[0009] The pressure gauge according to the invention essentially consists of a pressing element, a decoupling element, at least one strain gauge, a coupling element, an evaluation unit, and a clamping device. The decoupling element, the at least one strain gauge, and the coupling element are arranged in layers between the pressing element and the pipe surface. With the aid of the clamping device, which can be designed, for example, as a clamp, the preferably clamp-block-shaped pressing element and the intervening layers of decoupling element, strain gauge, and coupling element can be pressed onto the pipe surface, thereby securely and preferably also releasably attaching the entire pressure gauge to the pipe surface.

[0010] The decoupling element is designed to transmit the contact pressure generated by the clamping device radially to the at least one strain gauge, thereby ensuring a force-fit and / or form-fit connection between the at least one strain gauge, the coupling element, and the pipe surface, while still allowing freedom of movement in the longitudinal and circumferential directions of the pipe. The coupling element enables the transmission of pipe surface deformations resulting from internal pressure to the at least one strain gauge.

[0011] This means that via a radial, quasi-point-like force application by the clamping element, which is converted or transferred to the at least one strain gauge as a uniform, area-wide force, the movement of the pipe surface in the x- and z-axes can be directly transferred to the at least one strain gauge via the coupling element located between the at least one strain gauge and the pipe surface due to the friction-fit and / or positive-locking connection. Finally, the values ​​measured by the strain gauge can be electronically evaluated and output as a measurement signal using the evaluation unit.

[0012] The invention proposes a pressure measuring device that can be easily attached to a suitable section of a pipeline without requiring an opening in the wall of the measuring tube for insertion of the device. The coupling element transmits the surface changes of the pipeline, caused by the pressure of the medium inside the pipeline, to the strain gauge(s) and detects them.

[0013] An advantageous embodiment of the invention provides that the coupling element consists of a carrier material with a grain structure, and that at least one strain gauge rests directly on the grain structure. During assembly, the numerous small grains of sand effectively dig into the strain gauge. The resulting positive fit ensures that surface changes in the pipeline are optimally transferred to the strain gauge(s). Preferably, the carrier material is designed as a conductive film with the grain structure sprayed onto a creep-resistant adhesive or as sandpaper.

[0014] A further advantageous embodiment of the invention provides that at least two strain gauges are included, arranged opposite each other on the pipe surface. If, for example, a bending moment has been unintentionally introduced into the pipe due to temperature-related changes in pipe length or deformation, this could then be neutralized in a simple manner. Furthermore, natural vibrations and low-frequency resonances in long pipes could be detected and eliminated accordingly.

[0015] A further advantageous embodiment of the invention provides that at least two strain gauges are included, arranged side by side or one above the other, such that a first strain gauge can detect longitudinal expansions of the pipe surface and a second strain gauge can detect transverse expansions of the pipe surface. A further advantageous embodiment of the invention provides that the strain gauge(s) is / are designed as a micro strain gauge (MSG). This is a micro strain gauge used to measure minute deformations.

[0016] The invention will now be explained in more detail using an exemplary embodiment with reference to the drawing.

[0017] Figure 1 shows a very schematic, exploded view of a clamp-on pressure gauge 1 according to the invention, which is arranged on a pipeline 2. The pressure gauge 1 consists of a clamping element 10, a decoupling element 11, preferably designed as a rubber layer, a strain gauge 12, a coupling element 13, and a clamping device 14, which is only partially indicated. Not shown are an evaluation unit and corresponding connections for supplying power to the pressure gauge 1 and for transmitting the measurement signals to a higher-level control unit, e.g., a PLC.

[0018] The decoupling element 11, the strain gauge 12, and the coupling element 13 are arranged in layers, one above the other, between the pressure element 10 and the pipe surface 2a. Using the clamping device 14, which is preferably clamp-like and arranged around the pipe 2, the clamp-block-like pressure element 10 and the intervening layers of decoupling element 11, strain gauge 12, and coupling element 13 are pressed onto the pipe surface 2a, thus firmly and ideally also releasably attaching the entire pressure gauge 1 to the pipe surface 2a. The coupling element 13 consists of a carrier material with a grain, e.g., sandpaper or a conductor film with grains sprayed onto a creep-resistant adhesive.During assembly, the many small grains of sand essentially dig into the strain gauge 12, thus ensuring a primarily positive connection between the strain gauge 12 and the coupling element 13. The deformations of the pipe surface 2a resulting from pressure inside the pipe are then optimally transferred to the strain gauge 12. The single large arrow and the several small arrows below it illustrate that, via a radial, quasi-point-like force application by the clamping element 10, this force is converted or transferred into a uniform, area-wide force on the strain gauge 12, so that, via the coupling element 13 located between the strain gauge 12 and the pipe surface 2a, the movement of the pipe surface 2a in the longitudinal and circumferential directions, i.e.,in the x- and z-axes, due to the primarily positive-locking connection in this embodiment, the force is transferred directly to the at least one strain gauge 12. However, a combination of friction-locking and positive-locking connections or friction-locking alone is also conceivable.

[0019] Not explicitly shown, but included in the invention, is an embodiment with two strain gauges 12 arranged side by side or one above the other. Crucially, one of the strain gauges 12 can then detect the longitudinal expansions of the pipe surface 2a, and the other strain gauge 12 can detect the transverse expansions of the pipe surface 2a.

[0020] Reference symbol list

[0021] 1 Clamp-on pressure gauge

[0022] 2 Pipeline

[0023] 2a Pipe surface

[0024] 10 pressure part

[0025] 11 Decoupling element

[0026] 12 strain gauges

[0027] 13 Coupling element

[0028] 14 Clamping device

Claims

Patent claims 1. Clamp-on pressure gauge (1) for detecting a pressure prevailing in a pipeline (2), comprising a clamping element (10), decoupling element (11), at least one strain gauge (12), a coupling element (13), an evaluation unit and a clamping device (14), wherein the decoupling element (11), the at least one strain gauge (12) and the coupling element (13) are arranged layered on top of each other between the clamping element (10) and the pipeline surface (2a) and the clamping device (14) is suitable for firmly attaching the pressure gauge (1) to the pipeline surface (2a), wherein the decoupling element (11) is suitable for transmitting the clamping pressure generated by the clamping device (14) in a radial direction to the at least one strain gauge (12) and thus for a force-fit and / or form-fit connection between the at least one strain gauge (12),to ensure the coupling element (13) and the pipe surface (2a), but allowing freedom of movement in the longitudinal and circumferential direction of the pipe (2), wherein the coupling element (13) is suitable for transmitting the deformations of the pipe surface (2a) resulting from pressure inside the pipe (2) to the at least one strain gauge (12), and wherein the evaluation unit is suitable for electronically evaluating the values ​​measured by the at least one strain gauge (12) and outputting them as a measurement signal.

2. Pressure measuring device according to claim 1, wherein the coupling element (13) consists of a carrier material provided with a graining and the at least one strain gauge (12) rests on the graining.

3. Pressure measuring device according to claim 1 or 2, wherein the coupling element (13) is designed as a creep-resistant adhesive with sprayed-on grit or as sandpaper.

4. Pressure measuring device according to claim 2 or 3, wherein the grain consists of corundum, quartz or diamond.

5. Pressure measuring device according to one of the preceding claims, comprising at least two strain gauges (12) arranged opposite each other on the pipe surface (2a).

6. Pressure measuring device according to one of the preceding claims, comprising at least two strain gauges (12) arranged side by side, one above the other or one inside the other, such that a first strain gauge can detect longitudinal expansions of the pipe surface and a second strain gauge can detect transverse expansions of the pipe surface.

7. Pressure measuring device according to one of the preceding claims, wherein the decoupling element (11) is designed as a rubber layer or made of an elastomer.

8. Pressure measuring device according to one of the preceding claims, wherein the clamping device (14) transmits the force to the pressure part (10) via a ball joint.

9. Pressure measuring device according to one of the preceding claims, wherein the contact part (10) has a recess on the side facing the decoupling element (11) into which the decoupling element (11) can move.

10. Pressure measuring device according to one of the preceding claims, wherein the strain gauge(s) (12) is / are designed as a Micro Strain Gauge (MSG).

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