DE102008039464A1 - Multilayered measuring pipe for use in e.g. clamp-on ultrasonic flowrate measuring system in hygiene application, has material layers including thickness at thin side of each layer not exceeding wavelength of ultrasound signal in each layer - Google Patents

Abstract

The pipe (3) has a measuring pipe wall (10) including two material layers (7, 8) as an acoustic damper, where thicknesses of the material layers at a thin side of each layer do not exceed a wavelength of an ultrasound signal in each layer. The wall includes a third material layer (9) in an area of two ultrasonic transducers (2) e.g. clamp-on-ultrasonic transducers, which are provided on an outer wall (14) of the pipe. The two material layers are made of different materials. The pipe is monolithically designed.

Description

The The present invention relates to a measuring tube of an ultrasonic flow measuring system for determining and / or monitoring the flow of a Measuring medium through the measuring tube, which ultrasonic flow measuring system at least one ultrasonic transducer and at least one control / evaluation unit which control / evaluation unit based on the measurement signals or based on measurement data derived from the measurement signals, the volume and / or the mass flow of the flowing in the measuring tube Determined measuring medium, the ultrasonic transducer at least one electromechanical Transducer element which transmits ultrasonic signals and / or receives.

Ultrasonic flowmeters are widely used in process and automation technology. They allow in a simple way, the volume flow and / or Determine mass flow in a pipeline.

The known ultrasonic flowmeters often work after the Doppler or after the transit time difference principle.

At the Runtime difference principle, the different maturities of ultrasonic pulses relative to the flow direction of Liquid evaluated.

For this Ultrasonic pulses are at a certain angle to the tube axis sent both with and against the flow. Out the transit time difference can be the flow rate and so that with known diameter of the pipe section of the volume flow determine.

At the Doppler principle will be ultrasonic waves with a specific frequency coupled into the liquid and that of the liquid Evaluated reflected ultrasonic waves. From the frequency shift between the coupled and reflected waves also the flow rate of the liquid determine.

reflections in the liquid, however, occur only when air bubbles or impurities are present in this, so this principle mainly with contaminated liquids Use finds.

The ultrasonic waves are generated or received with the help of so-called ultrasonic transducers. For this purpose, ultrasonic transducers are firmly attached to the pipe wall of the relevant pipe section. More recently, clamp-on ultrasonic flow measurement systems have become available. In these systems, the ultrasonic transducers are pressed against the pipe wall only with a tension lock. Such systems are for. B. from the EP 686 255 B1 . US-A 44 84 478 or US-A 45 98 593 known.

Another ultrasonic flowmeter, which operates on the transit time difference principle, is from the US-A 50 52 230 known. The transit time is determined here by means of short ultrasound pulses.

One big advantage of clamp-on ultrasonic flow measuring systems is that they do not touch the measuring medium and on one already existing pipeline are attached.

The Ultrasonic transducers usually consist of a piezoelectric Element, also called piezo for short, and a coupling layer, also coupling wedge or less commonly called Vorlaufkörper. The coupling layer is usually made of plastic, the piezoelectric element exists in industrial process measuring technology usually from a piezoceramic. In the piezoelectric element, the Ultrasonic waves generated and the coupling layer to Passed pipe wall and from there into the liquid directed. Because the speed of sound in liquids and plastics are different, the ultrasonic waves broken in the transition from one medium to another. The angle of refraction is determined in the first approximation according to Snell's law. The angle of refraction is thus dependent on the ratio the propagation speeds in the media.

Between the piezoelectric element and the coupling layer can be another Coupling layer may be arranged, a so-called adaptation layer. The adaptation layer assumes the function of Transmission of the ultrasonic signal and at the same time the reduction a reflection caused by different acoustic impedances at boundary layers between two materials.

A major disadvantage, in particular of clamp-on systems, but also of inline ultrasonic flow measuring systems, is the propagation of so-called tube waves in the measuring tube. The ultrasonic signal coupled into the measuring tube by an ultrasonic transducer used as transmitter propagates not only on its actual sound path in the measuring tube, but also as a tube wave in the measuring tube wall. The tube waves can propagate so much over the measuring tube wall between the transmitter and the receiver that the actual measuring signal on the signal path in the measuring medium interferes with these tube waves and thereby significantly worsens the measuring accuracy. Especially for measuring tubes with large wall thicknesses in the range of multiple wavelengths of Ul used This signal effect exists.

There conventionally clamp-on ultrasonic flow measurement systems used in applications that are not for use of inline systems are suitable, such. B. for special hygiene applications or with aggressive measuring media, measuring tubes for high pressures however, have large wall thicknesses, These measuring tubes are not for the use of clamp-on systems very unfavorable.

The The object of the invention is to provide a measuring tube for the Use of ultrasonic flow measurement systems to provide which strongly suppresses the propagation of tube waves.

The The task is solved by a measuring tube of an ultrasonic flow measuring system for determining and / or monitoring the flow of a Measuring medium through the measuring tube, which ultrasonic flow measuring system at least one ultrasonic transducer and at least one control / evaluation unit which control / evaluation unit based on the measurement signals or based on measurement data derived from the measurement signals, the volume and / or the mass flow of the flowing in the measuring tube Determined measuring medium, the ultrasonic transducer at least one electromechanical Transducer element which transmits ultrasonic signals and / or receives, wherein the measuring tube has a measuring tube, which Meßrohrwandung at least partially from a first Material layer and at least a second material layer consists, wherein the thicknesses of the first and the second material layers on the each thinnest point of the respective material layer at most the simple of the wavelength λ of Ultrasonic signal in the respective material layer amount. A multi-layered part of a wall of the measuring tube thus exists from at least two material layers. The material layers, whose thicknesses are at most the simple of the wavelength λ of Amount to ultrasonic signal in the respective material layer, are acoustically damping. The individual can Material layers of the multilayer part of the measuring tube approximately have the same layer thicknesses. However, in one embodiment at least one material layer of the multilayer part of the measuring tube a different thickness to the first material layer. The material layers of the multi-layered part of the measuring tube can over their longitudinal extent is changing or approximately have constant thicknesses.

In In one embodiment of the invention, the thicknesses are at the respective thinnest point of the first and further material layers at most 0.8 times the wavelength λ of Ultrasonic signal in the respective material layer, preferably maximum 0.5 times, in particular at most 0.3 times, in particular Not more than 0.2 times, in particular at most 0.1 times.

A particularly preferred embodiment of the invention Solution has a first and at least another, second material layer, each having a thickness each thinnest point of the respective material layer of at most 0.5 times the wavelength λ of Ultrasonic signal in the respective material layer. A variant has the thicknesses of said material layers with at least 0.2 times the said wavelength of the ultrasonic signal out.

In In a further embodiment of the invention, the longitudinal dimensions are each approximately the thinnest point of Material layers at least twice the wavelength λ of Ultrasonic signal in the respective material layer, in particular at least five times, in special execution at least ten times the wavelength λ of Ultrasonic signal in the respective material layer. The longitudinal extent is essentially approximately perpendicular the thickness of the respective material layer. The thinnest Position here denotes the part of the individual material layer, which is at most the simple of the wavelength λ of Ultrasound signal in the respective material layer is thick.

Such Measuring tubes can be highly flexible, but at the same time high static load capacity. The material layers are preferred radially layered, d. H. from the inside to the outside of the Measuring tube.

In In another embodiment, the measuring tube has its total axial length is approximately the same Outside and inside diameter. The wall thickness of the multi-layered part of the measuring tube can thereby of the wall thickness of a single-layered part by intermediately stored cavities differ.

Next Made are on the outer wall of the measuring tube at least two clamp-on ultrasonic transducer attachable and / or there are at least two in the Meßrohrwandung Inline ultrasonic transducer attachable.

According to an advantageous development of the measuring tube according to the invention, the measuring tube wall in the region of the ultrasonic transducer consists of exactly one third material layer. The measuring tube wall thus has in the region of the ultrasonic transducer exactly a third material layer, which is continuous from the measuring tube inner wall to the measuring tube outside wall. In the area of the Ultra Sound transducer is thus only a single-layered part of the measuring tube. Exactly one massive layer of material runs from the measuring tube inner wall to the measuring tube outside wall. This is advantageous for the use of a clamp-on ultrasonic transducer on the outside of the measuring tube. The input and / or output ultrasonic signals are thus not interrupted by separate layers. In this case, the third material layer in particular has a thickness greater than the single wavelength λ of the ultrasound signal in the third material layer. In one embodiment, the wall thickness of the measuring tube is approximately constant over the entire measuring tube thickness. This has the consequence that the third material layer has a thickness which corresponds approximately to the sum of the first and the further material layers of the multilayer part of the measuring tube and any voids between the material layers.

To achieve this embodiment z. B. with a massive use in an otherwise multi-layered measuring tube, which the multi-layered interrupts, or z. B. with multi-layer inserts in an otherwise massive measuring tube. The bets can be tubular or cup-shaped.

A Another variant of the invention provides a single-layer insert with circumferential multilayer ring in front. This use can z. B. used in an existing single-layer piping system become. On the one-layered part of the insert can then a Ultrasonic sensor can be applied. The insert decreases in the Use in an approximately circular tube the Shape of a simply curved shell. The hole in the pipe and the corresponding filling this form of the hole Insert can be either round or square.

A very advantageous development of the invention Measuring tube can be seen in that the measuring tube wall at least a bore for use of at least one ultrasonic transducer.

A advantageous development of the invention Measuring tube suggests that the first material layer can be produced from a first material and that at least the second material layer produced from a second material is, wherein the first and the second material differ from each other.

in this connection can z. B. the material of the material layer, which is the measuring medium touched, so the measuring tube inner wall forms, of the material the material layer, which the measuring tube outer wall, ie the measuring tube wall forms the environment differ. Another Variant is that between two material layers of the multilayer Part of the measuring tube, which consist of the same material, another material layer is made of a different material. Such separation or intermediate layers are preferably made of a sound-damping Material or a material with corresponding acoustic impedance in Compared to the surrounding layers, made.

In In one embodiment, the materials differ one or several material layers of the multilayer part of the measuring tube from the material of a single-layered part of the measuring tube. The third Material layer thus has one of the first and / or second Material layer on different material.

In a further embodiment of the invention, the differ Materials of the measuring tube not from the piping system in the environment of the measuring tube, d. H. So from the pipe sections surrounding the measuring tube a piping system, in which the measuring tube is used.

A further advantageous embodiment of the invention Measuring tube provides that all material layers of the measuring tube can be produced from one and the same material. In a variant are at least the material layers contacting the measuring medium the measuring tube is made of the same material as a pipeline system, in which the measuring tube is embedded. Another version shows that the first and / or the second material layer of the measuring tube are made of the same material as the third material layer.

at A very advantageous development of the invention is the measuring tube built monolithic. The measuring tube is in one piece. It is therefore manufacturable from one piece. Produce for example via electrochemical Deposition processes such as galvanization, by casting with lost cores or by winding a coil into a spiral. plastic is for example by means of a rapid prototyping method or to produce related processes.

These Design differs from a multi-layered part of the measuring tube, a silencer adapter, which in one-piece and / or single-layer measuring tube is stored and / or between two integral and / or embedded einschichtigen Meßrohrteilen. Methods such pipes are to produce z. B. the welding of individual parts or nesting and shrinking several pipe parts a multi-layer pipe part.

According to one advantageous development of the invention Measuring tube is suggested that the first and at least the second material layer non-positive and / or cohesive connected to each other. The multilayer part of the measuring tube can certainly with the single-layered part of the measuring tube and / or the form-fitting and / or materially connected to the surrounding piping system be, between the material layers of the multilayer part However, there is no positive and / or material connection. The layers do not touch, z. B. when a filled and / or unfilled cavity between the layers of material exists, and / or they are loosely on each other. However, the material layers are of the multi-layered part over the single-layered part the measuring tube and / or over the surrounding piping system or via attached pipe flanges interconnected.

A further embodiment of the solution according to the invention shows that opposite surfaces of the configured first structurable first and second material layer are. Through opposing structures arise small, definable points of contact. This is a cavity definable between the material layers, which z. B. also with fill a mechanically soft and / or compressible material leaves. Furthermore, this allows the material layers connect positively and / or non-positively.

A advantageous development of the invention Measuring tube is that the measuring tube by means of an electrochemical Deposition method can be produced, with two or more different Materials can alternate in any order, such as For example, low and high density metals.

In a further embodiment of the invention, the measuring tube with Two or more different manufacturing processes can be built up in layers. For example, an electroplated surface a damping material layer, ie a material layer of the multilayer part of the measuring tube, still to be painted or mechanically to edit, z. B. to knurling. This can be a structured Surface to be obtained. On this embossed or structured surface could be exemplary another material layer are applied, for. B. by shrinking two Pipes into each other. This will ensure that the surfaces Both material layers only selectively with each other in direct Standing in contact. The same effect can be achieved with a structured sheet, which is wound into a multilayer pipe.

Farther the problem underlying the invention is solved by the use of a multilayer pipe section with at least two layers of material as an acoustic damper between two single-layer pipe sections, wherein the at least two Material layers have thicknesses, which thicknesses at the respectively thinnest point of the respective material layer at most the simple of the wavelength λ of an acoustic Be signal in the respective material layer. The least two layers of material are preferably radially superimposed layered from the measuring tube inner wall to the measuring tube outside wall. At least one of the two single-layer pipe sections is acoustically coupled with an ultrasonic transducer.

The The invention will be explained in more detail with reference to the following figures.

1 shows a multi-layered measuring tube with single-layer inserts in the region of two clamp-on ultrasonic transducers,

2 shows a single-layer measuring tube with two clamp-on ultrasonic transducers and a multilayer tube piece in between,

3 shows a multilayer measuring tube with two inline ultrasonic transducers used.

In 1 is a measuring tube 3 represented, which a Messrohrwandung 10 from the measuring tube inner wall 15 to the measuring tube outside wall 14 which consists of two material layers 7 . 8th consists. This measuring tube wall 10 may also consist of several layers of material according to the invention. The thicknesses of the material layers 7 . 8th However, it is limited to the simple of the wavelength of a used ultrasonic signal in the measuring tube. This has the acoustically damping effect, which means the propagation of tube waves, especially between the ultrasonic sensors 2 , is prevented. Two ultrasonic transducers 2 each with an electromechanical transducer element 5 are on the measuring tube 3 applied. It is therefore a clam-on ultrasonic flow measuring system 1 ,

The first material layer 7 is in this example the medium contacting material layer. So this forms the measuring tube inner wall 15 , Conversely, the measuring tube outside wall 14 from the second material layer 8th educated. The third material layer 9 is from the measuring tube outside wall 14 to the measuring tube inner wall 15 continuously. Here forms the third material layer 9 one into the otherwise multi-layered measuring tube 3 used insert. The insert thus forms both a part of the measuring tube outer wall 14 as well as the measuring tube inner wall 15 ,

This insert can be provided both in Holes in the otherwise multi-layered measuring tube 3 be introduced and, for. B. by a welded joint, with the otherwise multi-layered measuring tube 3 be connected, whereby the insert part of the measuring tube 3 is, or the single-layer use, so the third layer of material 9 , and the multi-layered part of the measuring tube, here the first material layer 7 and the second material layer 8th , have been prepared in a primary molding process, for. As by casting or galvanizing or by rapid prototyping.

As already mentioned, could be the multilayered part of the measuring tube z. B. also from three superimposed Material layers exist. A kind of sandwich would emerge. The first and the second material layer would be here include a fourth layer of material. Suitable materials as such separation or intermediate layer are z. B. aluminum between two steel or stainless steel layers, an oxide layer, z. B. by a surface treatment of the first and / or second Material layer. Depending on the expected application temperature is also Plastic suitable, for. B. as a foil, or ceramic, solder, adhesive, Liquid or gas, eg. B. at an air gap between the first and second material layers. A vacuum is also conceivable.

This embodiment differs from a multilayer part of the measuring tube, a silencer intermediate piece which is embedded in a one-piece and / or single-layer measuring tube and / or interposed between two one-piece and / or single-layered measuring tube parts, as shown in FIG 2 is shown.

2 discloses an ultrasonic flowmeter 1 with a measuring tube 3 from three pieces of pipe. A multilayer pipe piece 12 is between two single-layer pipe sections 13 appropriate. On the single-layer pipe sections 13 from only one material layer 9 , are on the outside wall 14 , in each case an ultrasonic sensor 2 appropriate. Both ultrasonic transducers 2 each have at least one electromechanical transducer element 5 , The between the two single-layer pipe sections 13 attached multilayer pipe section 12 has a first material layer in this example 7 and a second material layer 8th on. The first material layer 7 forms part of the inner wall 15 of the measuring tube 3 , which is the measuring medium 4 limited in its extent radially outward, while the second material layer 8th the part of the outer wall 14 of the measuring tube 3 forms. Other parts of the inner and outer wall 14 . 15 of the measuring tube 3 be from the material layer 9 of the single-layered measuring tube piece 13 educated. Both material layers 7 . 8th of the multilayer pipe section 12 have at their thinnest point a thickness which corresponds at most to the wavelength of the ultrasonic signal used. Preferably, they are even only 0.5 times as large. The third material layer 9 however, it is much thicker. In this embodiment, all material layers 7 . 8th . 9 About the tube length approximately constant thick.

This embodiment of a multilayer insert, in this case a multi-layered measuring tube piece 12 , in an otherwise single-layer measuring tube thus differs significantly from the design 1 where single-layer inserts into an otherwise multi-layered measuring tube 3 are introduced.

The first and the second material layer 7 . 8th lie only loosely on each other. They are not directly connected. Only through the third material layer 9 they communicate with each other. Can be produced in one piece this embodiment z. B. by electrochemical deposition. Another possibility for the production consists of the individual material layers 7 . 8th of the multilayer muffler spacer 12 individually to the single-layer pipe sections 13 to weld. As the first and the second material layer 7 . 8th in this example, approximately constant in thickness and also approximately the same thickness and the third material layers 9 are also approximately constant in thickness, are the third material layers 9 approximately twice as thick as the first two layers of material 7 . 8th ,

3 shows an in-line ultrasonic flow measuring system 1 with a multilayer measuring tube 3 , The measuring tube here consists of one, the measuring medium 4 touching and thus the measuring tube inner wall 15 forming first material layer 7 and a second material layer forming the measuring tube outside wall 8th , In the measuring tube 3 are holes 11 provided, in which the ultrasonic transducer 2 with the electromechanical transducer elements 5 are used. Due to the multilayer structure of the measuring tube wall 10 Be the measuring interfering tube waves between the ultrasonic sensors 2 avoided. For this purpose, have two material layers 7 . 8th corresponding maximum thicknesses.

1

Ultrasonic flowmeter

2

ultrasound transducer

3

measuring tube

4

measuring medium

5

electromechanical transducer element

6

Control / evaluation unit

7

First Material layer

8th

Second Material layer

9

third Material layer

10

Messrohrwandung

11

drilling

12

multilayer pipe section

13

Single layer pipe section

14

outer wall of the measuring tube

15

inner wall of the measuring tube

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - EP 686255 B1 [0008]
• - US 4484478 A [0008]
• - US 4598593 A [0008]
• - US 5052230 A [0009]

Claims (10)

Measuring tube ( 3 ) of an ultrasonic flow measuring system ( 1 ) for determining and / or monitoring the flow of a measuring medium ( 4 ) through the measuring tube ( 3 ), which ultrasonic flow measuring system has at least one ultrasonic transducer ( 2 ) and at least one control / evaluation unit ( 6 ), which control / evaluation unit ( 6 ) based on the measurement signals or on the basis of measurement data, which are derived from the measurement signals, the volume and / or the mass flow of the in the measuring tube ( 3 ) flowing measuring medium ( 4 ), wherein the ultrasonic transducer ( 2 ) at least one electromechanical transducer element ( 5 ) which transmits and / or receives ultrasonic signals, wherein the measuring tube ( 3 ) a measuring tube wall ( 10 ), which measuring tube wall ( 10 ) at least partially from a first material layer ( 7 ) and at least one second material layer ( 8th ), wherein the thicknesses of the first and the second material layers ( 7 . 8th ) at the thinnest point of the respective material layer ( 7 . 8th ) at most the simple of the wavelength λ of the ultrasonic signal in the respective material layer ( 7 . 8th ) amount. Measuring tube ( 3 ) according to claim 1, characterized in that the measuring tube wall ( 10 ) in the region of the ultrasonic transducer ( 2 ) from exactly one third material layer ( 9 ) consists. Measuring tube ( 3 ) according to claim 1 or 2, characterized in that on the outer wall ( 14 ) of the measuring tube ( 3 ) at least two clamp-on ultrasonic transducers ( 2 ) are attachable and / or in the measuring tube wall ( 10 ) at least two inline ultrasonic transducers ( 2 ) are attachable. Measuring tube ( 3 ) according to claim 1 or 2, characterized in that the measuring tube wall ( 10 ) at least one bore ( 11 ) for use of at least one ultrasonic transducer ( 2 ) having. Measuring tube ( 3 ) according to one of claims 1 to 3, characterized in that the first material layer ( 7 ) can be produced from a first material and that at least the second material layer ( 8th ) can be produced from a second material, wherein the first and the second material differ from each other. Measuring tube ( 3 ) according to one of claims 1 to 3, characterized in that all material layers ( 7 . 8th . 9 ) of the measuring tube ( 3 ) are made of one and the same material. Measuring tube ( 3 ) according to one of claims 1 to 5, characterized in that the measuring tube ( 3 ) is constructed monolithically. Measuring tube ( 3 ) according to one of claims 1 to 6, characterized in that the first and at least the second material layer ( 7 . 8th ) are not positively and / or materially connected to each other. Device according to one of claims 1 to 8, characterized in that the measuring tube ( 3 ) can be produced by an electrochemical deposition process. Use of a multilayer pipe section ( 12 ) with at least two layers of material ( 7 . 8th ) as an acoustic damper between two single-layer pipe sections ( 13 ), wherein the at least two material layers ( 7 . 8th ) Thicknesses, which thicknesses at the respectively thinnest point of the respective material layer ( 7 . 8th ) at most the simple of the wavelength λ of an acoustic signal in the respective material layer ( 7 . 8th ) amount.