U.S. patent application number 11/709228 was filed with the patent office on 2007-08-23 for magnetic induction flowmeter having a plastic measuring tube.
This patent application is currently assigned to ABB Patent GmbH. Invention is credited to Dieter Keese.
Application Number | 20070193365 11/709228 |
Document ID | / |
Family ID | 38319777 |
Filed Date | 2007-08-23 |
United States Patent
Application |
20070193365 |
Kind Code |
A1 |
Keese; Dieter |
August 23, 2007 |
Magnetic induction flowmeter having a plastic measuring tube
Abstract
A magnetic induction flowmeter has a plastic measuring tube (1),
which can be inserted into a pipeline system, having at least two
mutually opposite measuring electrodes (3) introduced into the wall
of the measuring tube (1) in order to register a measuring voltage,
a magnetic unit (2), likewise arranged on the outside of the
measuring tube (1), generating a magnetic field aligned
substantially at right angles to the flow direction of the
conductive flow medium to be measured. The plastic measuring tube
(1) is equipped with means for diverting axial and thrust forces
which act from the outside on the measuring tube (1) inserted into
the pipeline system, in order to keep destructive mechanical
loadings away from the measuring tube (1).
Inventors: |
Keese; Dieter; (Wahlsburg,
DE) |
Correspondence
Address: |
BUCHANAN, INGERSOLL & ROONEY PC
POST OFFICE BOX 1404
ALEXANDRIA
VA
22313-1404
US
|
Assignee: |
ABB Patent GmbH
Ladenburg
DE
|
Family ID: |
38319777 |
Appl. No.: |
11/709228 |
Filed: |
February 22, 2007 |
Current U.S.
Class: |
73/861.12 |
Current CPC
Class: |
G01F 1/588 20130101;
G01F 1/58 20130101 |
Class at
Publication: |
73/861.12 |
International
Class: |
G01F 1/58 20060101
G01F001/58 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 23, 2006 |
DE |
10 2006 008 433.0 |
Claims
1. A magnetic induction flowmeter having a plastic measuring tube,
which can be inserted into a pipeline system, having at least two
mutually opposite measuring electrodes introduced into the wall of
the measuring tube in order to register a measuring voltage, a
magnetic unit, likewise arranged on the outside of the measuring
tube, generating a magnetic field aligned substantially at right
angles to the flow direction of the conductive flow medium to be
measured, wherein the plastic measuring tube is equipped with means
for diverting axial and thrust forces which act from the outside on
the measuring tube inserted into the pipeline system, in order to
keep destructive mechanical loadings away from the measuring
tube.
2. The magnetic induction flowmeter as claimed in claim 1, wherein
the means for diverting the axial and thrust forces comprise a
metal tube surrounding the measuring tube at a distance and, at
least at the end, connected to the measuring tube.
3. The magnetic induction flowmeter as claimed in claim 1, wherein
the means for diverting the axial and thrust forces comprise a
plurality of metal rod elements running along the measuring tube at
a distance from the latter and at a distance from one another and,
at least at the end, connected to the measuring tube.
4. The magnetic induction flowmeter as claimed in claim 1, wherein
the means for diverting the axial and thrust forces comprise a
casting compound surrounding the measuring tube.
5. The magnetic induction flowmeter as claimed in claim 2, wherein
the end connection is produced via an annular disk in each case
which is arranged at the end of the measuring tube and which is
fixed radially internally to the measuring tube and radially
externally to the metal tube or the rod elements or the like.
6. The magnetic induction flowmeter as claimed in claim 5, wherein
each annular disk is composed of a rigid plastic or of a metal.
7. The magnetic induction flowmeter as claimed in claim 5, wherein
each annular disk is fixed to the outside of the measuring tube so
as not to contact the substance to be measured.
8. The magnetic induction flowmeter as claimed in claim 7, wherein
the fixing is produced cohesively by means of adhesive bonding or
welding.
9. The magnetic induction flowmeter as claimed in claim 7, wherein
the fixing is produced cohesively by the fixing being concomitantly
injection molded during the injection molding of the tube.
10. The magnetic induction flowmeter as claimed in claim 1, wherein
the measuring tube is detachably inserted into the pipeline system
via flanged sections on both sides.
11. The magnetic induction flowmeter as claimed in claim 10,
wherein the flanged sections are at least partly a constituent part
of the annular disks.
12. The magnetic induction flowmeter as claimed in claim 3, wherein
the end connection is produced via an annular disk in each case
which is arranged at the end of the measuring tube and which is
fixed radially internally to the measuring tube and radially
externally to the metal tube or the rod elements or the like.
13. The magnetic induction flowmeter as claimed in claim 4, wherein
the end connection is produced via an annular disk in each case
which is arranged at the end of the measuring tube and which is
fixed radially internally to the measuring tube and radially
externally to the metal tube or the rod elements or the like.
14. The magnetic induction flowmeter as claimed in claim 2, wherein
the measuring tube is detachably inserted into the pipeline system
via flanged sections on both sides.
15. The magnetic induction flowmeter as claimed in claim 3, wherein
the measuring tube is detachably inserted into the pipeline system
via flanged sections on both sides.
16. The magnetic induction flowmeter as claimed in claim 4, wherein
the measuring tube is detachably inserted into the pipeline system
via flanged sections on both sides.
17. The magnetic induction flowmeter as claimed in claim 5, wherein
the measuring tube is detachably inserted into the pipeline system
via flanged sections on both sides.
18. The magnetic induction flowmeter as claimed in claim 6, wherein
the measuring tube is detachably inserted into the pipeline system
via flanged sections on both sides.
19. The magnetic induction flowmeter as claimed in claim 12,
wherein the measuring tube is detachably inserted into the pipeline
system via flanged sections on both sides.
20. The magnetic induction flowmeter as claimed in claim 13,
wherein the measuring tube is detachably inserted into the pipeline
system via flanged sections on both sides.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority under 35 U.S.C. .sctn.119
to German Application 10 2006 008 433.0 filed in Germany on 23 Feb.
2006, the entire contents of which are hereby incorporated by
reference in their entireties.
FIELD
[0002] A magnetic induction flowmeter having a plastic measuring
tube is disclosed, which can be inserted into a pipeline system,
having at least two mutually opposite measuring electrodes
introduced into the wall of the measuring tube in an electrically
insulated manner in order to register a measuring voltage, and a
magnetic unit, likewise arranged on the outside of the measuring
tube, generating a magnetic field aligned substantially at right
angles to the flow direction of the conductive flow medium to be
measured.
BACKGROUND INFORMATION
[0003] A magnetic induction flow meter is used as a flow meter for
liquids, pulps and pastes which have a specific minimum electric
conductivity. This type of flowmeter is distinguished by quite
accurate measured results, no pressure loss in the pipeline system
being caused by the measurement. In addition, magnetic induction
flowmeters have no parts which move or project into the measuring
tube and which, in particular, are subject to wear. The area of use
of the flowmeters of interest here extends primarily to
applications in the chemical industry, pharmaceuticals and the
cosmetic industry, and also the communal water and effluent
business as well as the foodstuffs industry.
[0004] Faraday's induction law forms a physical basis of the
measuring method of a magnetic induction flowmeter. This natural
law states that a voltage is induced in a conductor moving in a
magnetic field. During the utilization of this natural law for
measurement, the electrically conductive medium flows through a
measuring tube in which a magnetic field is generated at right
angles to the flow direction. The voltage induced in the medium is
picked up by an electrode arrangement. Since the measuring voltage
obtained in this way is proportional to the average flow velocity
of the flowing medium, the volume flow of the medium can be
determined from it. In addition, by taking account of the density
of the flowing medium, its mass flow can also be determined.
[0005] Measuring tubes of such magnetic induction flowmeters are
primarily composed of metal and, in order to implement the
measuring principle, are provided with internal electrical
insulation. In addition, there also exist plastic measuring tubes,
in which it is usually possible to dispense with additional
internal electrical insulation. The present disclosure relates to
the last-named type of measuring tubes.
[0006] DE 103 47 890 A1 reveals a generic magnetic induction
flowmeter whose measuring tube is composed of plastic. In order to
produce the measuring tube, a fiber composite material is used. The
measuring electrodes that contact the substance to be measured are
composed of metal plates, which are placed on a core and are
subsequently enveloped by the first wound layers of the fiber
composite material. After the wound layers have been cured, the
core is removed, so that the measuring electrodes are given contact
with the conductive flow medium. The surface structure of the
measuring tube can be configured within wide limits because of the
winding technique. For example, molded-on portions can be produced
in the end region of the measuring tube in order to achieve the
largest possible sealing areas. The magnetic unit is preferably
embedded completely within the wall of the measuring tube and is
therefore accommodated therein in a protected manner.
[0007] The wall thickness of the measuring tube consisting of
plastic has to be dimensioned in such a way that the material
withstands the external mechanical loadings. Disruptive external
mechanical loadings are produced, for example, by the pipeline into
which the measuring tube is inserted. Thus, depending on the
installation situation, disruptive mechanical influences in the
form of axial forces and/or thrust forces can occur on the
measuring tube and, in the extreme case, can lead to cracking or
even to fracture of the measuring tube.
[0008] Although these problems can be counteracted by an
appropriate material selection and also by generous dimensioning of
the wall thickness, this is often associated with considerable
expenditure on material and fabrication.
SUMMARY
[0009] A plastic measuring tube of a magnetic induction flowmeter
is disclosed to the effect that, by using simple means, destructive
mechanical loadings can be kept away from the measuring tube.
[0010] An exemplary plastic measuring tube is equipped with means
for diverting axial and thrust forces which act from the outside on
the measuring tube inserted into the pipeline system.
[0011] By using the force deflection means, which are additional to
this extent, destructive mechanical loadings can be managed in a
simple way. In this case, in the design of the measuring tube
itself, the loadings acting from the pipeline system can remain
disregarded. This is because these loadings are substantially kept
away from the measuring tube by the additional means for force
deflection. The measuring tube itself merely has to withstand other
loadings which, for example, are produced by pressure and
temperature of the flow medium flowing through. As a result, the
measuring tube itself can be quite thin-walled and therefore save
material. Accordingly, a low inherent mass can be achieved.
[0012] Suitable means for diverting the axial and thrust forces can
be a metal tube surrounding the measuring tube at a distance and,
at least at the end, connected to the measuring tube. As an
alternative exemplary embodiment, instead of a closed metal tube
for force diversion, to use individual rod elements arranged at a
distance from one another and from the measuring tube. Furthermore,
it is also possible to surround the measuring tube with a casting
compound made of a pourable material with adequate mechanical
loadbearing ability. In this case, this casting compound can either
be applied directly to the outside of the measuring tube or
likewise at a distance from the latter.
[0013] According to a further exemplary embodiment, the end
connection can be produced via an annular disk in each case which
is arranged at the end of the measuring tube and which is fixed
radially internally to the measuring tube and radially externally
to the metal tube or the rod elements or the like. To this extent,
the rod elements themselves can be rectilinear and can run parallel
to the measuring tube axis. Thus, starting from one end of the
measuring tube, the force flow runs via the annular disk arranged
here, then via the metal tube or the rod elements or the like to
the other annular disk and from there into the pipeline leading
onward. The measuring tube itself is thus freed to the greatest
extent from the disruptive mechanical loadings.
[0014] The annular disks to be used in conjunction with the metal
tube or the rod elements within the context of the means for
diverting the axial and thrust forces can be produced from a rigid
plastic or from a metal. In the latter case, a particularly high
mechanical loadbearing ability can be achieved with relative low
material thicknesses. However, an annular disc produced from metal
must be fixed to the outside of the measuring tube so as not to
contact the substance to be measured. This is because, by means of
this measure improving the exemplary embodiment further, it is
possible to ensure that disruptive electric potentials are not
passed on to the electrically conductive flow medium via the
metallic annular disks.
[0015] The fixing of the annular disk to the outside of the
measuring tube can be carried out cohesively by means of adhesive
bonding or welding. If the annular disk is comprised of metal, this
can be fixed to the plastic measuring tube in a straightforward
manner by means of adhesive bonding. If a plastic annular disk is
to be used, this can possibly be fixed by means of welding to the
measuring tube, likewise can be comprised of the same plastic.
Further alternative exemplary embodiments for cohesive fixings are
also conceivable. As compared with other types of fixing, the
exemplary types of fixing variously set forth above can be used
because of the simple implementation in terms of fabrication.
[0016] The measuring tube comprised of plastic can be inserted
detachably into the pipeline system, for example, via flanged
sections at the ends. In addition, it is also conceivable, instead
of the flanged sections, to insert the measuring tube into the
pipeline system via a plug-in connection or the like. If flanged
sections are used in order to produce a detachable connection of
the measuring tube in the pipeline system, then it is recommended
that these already partly be a constituent part of the annular
disks. To this extent, the annular disks constitute a functionally
integrated component.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] The disclosure will be illustrated in more detail below
together with the description of the various exemplary embodiments
and by using the figures, in which:
[0018] FIG. 1 shows an exploded illustration of a magnetic
induction flowmeter in a first exemplary embodiment,
[0019] FIG. 2 shows an exploded illustration of a magnetic
induction flowmeter in a second exemplary embodiment, and
[0020] FIG. 3 shows an exploded illustration of a magnetic
induction flowmeter in a third exemplary embodiment.
DETAILED DESCRIPTION
[0021] According to FIG. 1, the exemplary magnetic induction
flowmeter illustrated schematically here has a plastic measuring
tube 1. In this exemplary embodiment, the plastic used is polyether
ketone (PEEA). Arranged on the outside of the measuring tube 1 is a
magnetic unit 2, which generates a magnetic field aligned
substantially at right angles to the flow direction of the
conductive flow medium to be measured. The voltage induced in the
flow medium in this way is registered via two measuring electrodes
3 introduced opposite each other into the wall of the measuring
tube 1 and is then passed on to a signal processing device, not
further illustrated.
[0022] The quite thin-walled measuring tube 1, comprising plastic,
is also equipped with means for diverting external mechanical
loadings, which primarily act via the pipeline system. In this
exemplary embodiment, these means for diverting the axial and
thrust forces causing loadings comprise a metal tube 4 surrounding
the measuring tube 1 at a distance, which is fitted to the
measuring tube 1 via annular disks 5a and 5b arranged at the ends.
In this exemplary embodiment, the annular disks 5a and 5b are
comprised of metal and are connected cohesively via adhesive bonds,
radially internally to the measuring tube 1 and radially externally
to the enclosing metal tube 4. The connection is implemented in
such a way that the annular disks 5a and 5b are fixed to the
outside of the measuring tube 1--not making contact with the
substance to be measured.
[0023] In the exemplary embodiment illustrated in FIG. 2, as
distinct from the exemplary embodiment described above, instead of
a metal tube a plurality of rod elements 6a and 6b are used, which
form the force bridge between the two annular disks 5a' and 5b'
arranged at the ends of the measuring tube 1. Furthermore, the two
annular disks 5a' and 5b' likewise form flanged sections 6a and 6b
for the detachable fixing of the magnetic induction flowmeter in
the pipeline--not illustrated further. A flanged fixing of this
type is via known screw connections. Otherwise, the construction of
this exemplary embodiment corresponds to the construction of the
exemplary embodiment described above.
[0024] According to FIG. 3, in accordance with a further exemplary
embodiment, the means for deflecting the axial and thrust forces
loading the measuring tube 1 are a casting compound 8, which
encloses the measuring tube 1 and the components fitted in and on
the latter. The loadings acting from the outside are introduced
into the casting compound 8 via annular disks 5a'' and 5b'' fitted
to the measuring tube 1 at the ends. The casting compound 8 is
formed as a plastic cast and is applied to the measuring tube 1 by
being sprayed on. Glass fibers are embedded in the plastic in order
to increase the mechanical strength. The two annular disks 5a'' and
5b'' are braced against the cured casting compound 8 via tie rods 9
arranged axially parallel to the measuring tube 1, so that the
result overall is a stable unit. Otherwise, this exemplary
embodiment corresponds to the exemplary embodiment described
first.
[0025] The invention is not restricted to the exemplary embodiments
described in detail above. Thus, means configured in other ways for
diverting the disruptive axial and thrust forces are additionally
conceivable. Instead of rod elements 6a and 6b running
rectilinearly, curved rod elements can also be used which,
dispensing with separate annular disks, are fitted directly to the
measuring tube 1 at the ends. Overall, a flow meter formed in this
way is given an approximately barrel-like shape.
LIST OF DESIGNATIONS
[0026] 1 Measuring tube [0027] 2 Magnetic unit [0028] 3 Measuring
electrodes [0029] 4 Metal tube [0030] 5 Annular disk [0031] 6 Rod
element [0032] 7 Flanged section [0033] 8 Casting compound [0034] 9
Tie rod
* * * * *