Note: Descriptions are shown in the official language in which they were submitted.
CA 02754788 2011-09-08
MEASURING TRANSDUCER OF VIBRATION-TYPE, AS WELL AS AN IN-LINE
MEASURING DEVICE HAVING SUCH A MEASURING TRANSDUCER
The invention relates to a measuring transducer of vibration-
type for measuring a medium flowably guided in a pipeline,
especially a gas, liquid, powder or other flowable material,
especially for measuring a density and/or a mass flow rate,
especially also a mass flow integrated over a time interval,
of a medium flowing in a pipeline, at least at times, with a
mass flow rate of more than 2200 t/h, especially more than
2500 t/h. Additionally, the invention relates to an in-line
measuring device having such a measuring transducer.
Often used in process measurements, and automation,
technology for measuring physical parameters, such as e.g.
the mass flow, the density and/or the viscosity, of media
flowing in pipelines are in-line measuring devices, which, by
means of a measuring transducer of vibration-type, through
which medium flows, and a measuring, and operating, circuit
connected thereto, effect, in the medium, reaction forces,
such as e.g. Coriolis forces corresponding with mass flow,
inertial forces corresponding with density of the medium
and/or frictional forces corresponding with viscosity of the
medium, etc., and produce derived from these a measurement
signal representing the particular mass flow, viscosity
and/or density of the medium. Such
measuring transducers,
especially measuring transducers embodied as Coriolis, mass
flow meters or Coriolis, mass flow/ densimeters, are
described at length and in detail e.g. in EP-A 1 001 254, EP-
A 553 939, US-A 4,793,191, US-A 2002/0157479, US-A
2006/0150750, US-A 2007/0151368, US-A 5,370,002, US-A
5,796,011, US-B 6,308,580, US-B 6,415,668, US-B 6,711,958,
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US-B 6,920,798, US-B 7,134,347, US-B 7,392,709, or WO-A
03/027616.
Each of the measuring transducers includes a transducer
housing, of which an inlet-side, first housing end is formed
at least partially by means of a first flow divider having
exactly two, mutually spaced, circularly cylindrical, or
tapered or conical, flow openings and an outlet-side, second
housing end is formed at least partially by means of a second
flow divider having exactly two, mutually spaced, flow
openings. In
the case of some of the measuring transducers
illustrated in US-A 5,796,011, US-B 7,350,421, or US-A
2007/0151368, the transducer housing comprises a rather thick
walled, circularly cylindrical, tubular segment, which forms
at least a middle segment of the transducer housing.
For guiding the medium, which flows, at least at times, the
measuring transducers include, furthermore, in each case,
exactly two measuring tubes of metal, especially steel or
titanium, which are connected such that the medium can flow
in parallel and which are positioned within the transducer
housing and held oscillatably therein by means of the
aforementioned flow dividers. A first of the, most often,
equally constructed and, relative to one another, parallel
extending, measuring tubes opens with an inlet-side, first,
measuring tube end into a first flow opening of the inlet-
side, first flow divider and with an outlet-side, second
measuring tube end into a first flow opening of the outlet-
side, second flow divider and a second of the measuring tubes
opens with an inlet-side, first measuring tube end into a
second flow opening of the first flow divider and with an
outlet-side, second measuring tube end into a second flow
opening of the second flow divider. Each
of the flow
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dividers includes additionally, in each case, a flange with a
sealing surface for fluid tight connecting of the measuring
transducer to tubular segments of the pipeline serving,
respectively, for supplying and removing medium to and from
the measuring transducer.
For producing the above discussed reaction forces, the
measuring tubes are caused to vibrate during operation,
driven by an exciter mechanism serving for producing, or
maintaining, as the case may be, mechanical oscillations,
especially bending oscillations, of the measuring tubes in
the so-called wanted mode. The
oscillations in the wanted
mode are, most often, especially in the case of application
of the measuring transducer as a Coriolis, mass flow meter
and/or densimeter, developed, at least partially, as lateral
bending oscillations and, in the case of medium flowing
through the measuring tubes, as a result of therein induced
Coriolis forces, as additional, equal frequency oscillations
superimposed in the so-called Coriolis mode.
Accordingly,
the - here most often electrodynamic - exciter mechanism is,
in the case of straight measuring tubes, embodied in such a
manner, that, therewith, the two measuring tubes are
excitable in the wanted mode, at least partially, especially
also predominantly, to opposite phase bending oscillations in
a shared plane of oscillation, differentially - thus through
introduction of exciter forces acting simultaneously along a
shared line of action, however, in opposed direction.
For registering vibrations, especially bending oscillations,
of the measuring tubes excited by means of the exciter
mechanism and for producing oscillation measurement signals
representing vibrations, the measuring transducers have,
additionally, in each case, a, most often, likewise
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electrodynamic, sensor arrangement reacting to relative
movements of the measuring tubes.
Typically, the sensor
arrangement is formed by means of an inlet-side, oscillation
sensor registering oscillations of the measuring tubes
differentially - thus only relative movements of the
measuring tubes - as well as by means of an outlet-side,
oscillation sensor registering oscillations of the measuring
tubes differentially. Each of the oscillation sensors, which
are usually constructed equally with one another, is formed
by means of a permanent magnet held on the first measuring
tube and a cylindrical coil held on the second measuring tube
and permeated by the magnetic field of the permanent magnet.
In operation, the above described inner part of the measuring
transducer, formed by means of the two measuring tubes as
well as the thereon held exciter mechanism and sensor
arrangement, is excited by means of the electromechanical
exciter mechanism, at least at times, to execute mechanical
oscillations in the wanted mode at at least one dominating,
wanted, oscillation frequency.
Selected as oscillation
frequency for the oscillations in the wanted mode is, in such
case, usually a natural, instantaneous, resonance frequency
of the inner part, which, in turn, depends essentially both
on size, shape and material of the measuring tubes as well as
also on an instantaneous density of the medium; in given
cases, this wanted oscillation frequency can also be
influenced significantly by an instantaneous viscosity of the
medium. As a
result of fluctuating density of the medium
being measured and/or as a result of media change occurring
during operation, the wanted oscillation frequency during
operation of the measuring transducer varies naturally, at
least within a calibrated and, thus, predetermined, wanted
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frequency band, which correspondingly has a predetermined
lower, and a predetermined upper, limit frequency.
For defining a free, oscillatory length of the measuring
tubes and, associated therewith, for adjusting the band of
the wanted frequency, measuring transducers of the above
described type includeõ additionally, most often, at least
one inlet-side, coupling element, which is affixed to both
measuring tubes and spaced from the two flow dividers, for
forming inlet-side, oscillation nodes for opposite phase
vibrations, especially bending oscillations, of both
measuring tubes, as well as at least one outlet-side,
coupling element, which is affixed to both measuring tubes
and spaced both from the two flow dividers, as well as also
from the inlet-side, coupling element, for forming outlet-
side, oscillation nodes for opposite phase vibrations,
especially bending oscillations, of the measuring tubes. In
the case of straight measuring tubes, in such case, a minimum
separation between inlet side and outlet side coupling
elements (which, thus, belong to the inner part) corresponds
to the free, oscillatory length of the measuring tubes. By
means of the coupling elements, additionally also an
oscillation quality factor of the inner part, as well as also
the sensitivity of the measuring transducer, in total, can be
influenced, in a manner such that, for a minimum required
sensitivity of the measuring transducer, at least one
minimum, free, oscillatory length is provided.
Development in the field of measuring transducers of
vibration-type has, in the meantime, reached a level, wherein
modern measuring transducers of the described type can, for a
broad application spectrum of flow measurement technology,
satisfy highest requirements as regards precision and
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reproducibility of the measurement results.
Thus, such
measuring transducers are, in practice, applied for mass flow
rates from some few l/h (gram per hour) up to some t/min
(tons per minute), at pressures of up to 100 bar for liquids
or even over 300 bar for gases. The accuracy of measurement
achieved, in such case, lies usually at about 99.9% of the
actual value, or above, or at a measuring error of about
0.1%, wherein a lower limit of the guaranteed measurement
range can lie quite easily at about 1% of the measurement
range end value.
Due to the high bandwidth of their
opportunities for use, industrial grade measuring transducers
of vibration-type are available with nominal diameters
(corresponding to the caliber of the pipeline to be connected
to the measuring transducer, or to the caliber of the
measuring transducer measured at the connecting flange),
which lie in a nominal diameter range between 1 mm and 250 mm
and at maximum nominal mass flow rate of 2200 t/h, in each
case, for pressure losses of less than 1 bar. A caliber of
the measuring tubes lies, in such case, for instance, in a
range between 80 mm and 100 mm.
In spite of the fact that, in the meantime, measuring
transducers for use in pipelines with very high mass flow
rates and, associated therewith, very large calibers of far
beyond 100 mm have become available, there is still
considerable interest in obtaining measuring transducers of
high precision and low pressure loss also for yet larger
pipeline calibers, about 300 mm or more, or mass flow rates
of 2500 t/h or more, for instance for applications in the
- petrochemical industry or in the field of transport and
transfer of petroleum, natural gas, fuels, etc.
This leads,
in the case of correspondingly scaled enlarging of the
already established measuring transducer designs known from
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the state of the art, especially from EP-A 1 001 254, EP-A
553 939, US-A 4,793,191, US-A 2002/0157479, US-A
2007/0151368, US-A 5,370,002, US-A 5,796,011, US-B 6,308,580,
US-B 6,711,958, US-B 7,134,347, US-B 7,350,421, or WO-A
03/027616, to the fact that the geometric dimensions would be
exorbitantly large, especially the installed length
=
corresponding to a distance between the sealing surfaces of
both flanges and, in the case of curved measuring tubes, a
maximum lateral extension of the measuring transducer,
especially dimensions for the . desired
oscillation
characteristics, the required load bearing ability, as well
as the maximum allowed pressure loss. Along with that, also
the empty mass of the measuring transducer increases
unavoidably, with conventional measuring transducers of large
nominal diameter already having an empty mass of about 400
kg.
Investigations, which have been carried out for
measuring transducers with two bent measuring tubes,
constructed, for instance, according to US-B 7,350,421 or US-
A 5,796,011, as regards their to-scale enlargement to still
= greater nominal diameters, have, for example, shown that, for
nominal diameters of more than 300 mm, the empty mass of a
to-scale enlarged, conventional measuring transducer would
lie far above 500 kg, accompanied by an installed length of
more than 3000 mm and a maximum lateral extension of more
than 1000 mm. As a result, it can be said that industrial
grade, mass producible, measuring transducers of conventional
design and materials with nominal diameters far above 300 mm
cannot be expected in the foreseeable future both for reasons
of technical implementability, as well as also due to
economic considerations.
Proceeding from the above recounted state of the art, an
embodiment of the invention may provide a
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measuring transducer of high sensitivity and high oscillation
quality factor, which also in the case of large mass flow rates
of more than 2200 t/h, causes only a small pressure loss of
less than 1 bar and which also has a construction, which is as
compact as possible at large nominal diameters of over 250 mm.
In an aspect, there is provided a measuring transducer of the
vibration-type for registering at least one physical, measured
variable of a flowable medium guided in a pipeline, for
producing Coriolis forces serving for registering a mass flow
rate of a flowable medium guided in a pipeline, or for both
registering at least one physical, measured variable of a
flowable medium guided in a pipeline and producing Coriolis
forces serving for registering a mass flow rate of a flowable
medium guided in a pipeline, said measuring transducer
comprising: a transducer housing, with an inlet-side, first
housing end formed by means of an inlet-side, first flow
divider, and with an outlet-side, second housing end formed by
means of an outlet-side, second flow divider, said first flow
divider including exactly four, mutually spaced, flow openings,
which are so arranged that imaginary areal centers of gravity
associated with the cross sectional areas of said flow openings
of said first flow divider form the vertices of an imaginary
square, said cross sectional areas lying in a shared,
imaginary, cutting plane of said first flow divider, and said
second flow divider including exactly four, mutually spaced,
flow openings, which are so arranged that imaginary areal
centers of gravity associated with the cross sectional areas of
said flow openings of said second flow divider form the
vertices of an imaginary square, said cross sectional areas
lying in a shared, imaginary, cutting plane of said second flow
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divider; four, straight, measuring tubes connected to said
first and second flow dividers for guiding flowing medium along
flow paths connected in parallel, said measuring tubes
including a first measuring tube, which opens with an inlet-
side, first measuring tube end into said first flow opening of
said first flow divider and with an outlet-side, second
measuring tube end into said first flow opening of said second
flow divider, said measuring tubes including a second measuring
tube, which opens with said inlet-side, first measuring tube
end into said second flow opening of said first flow divider
and with an outlet-side, second measuring tube end into said
second flow opening of said second flow divider, said measuring
tubes including a third measuring tube, which opens with said
inlet-side, first measuring tube end into said third flow
opening of said first flow divider and with an outlet-side,
second measuring tube end into said third flow opening of said
second flow divider; and said measuring tubes including a
fourth measuring tube, which opens with said inlet-side, first
measuring tube end into said fourth flow opening of said first
flow divider and with an outlet-side, second measuring tube end
into said fourth flow opening of said second flow divider; and
an electromechanical exciter mechanism for producing,
maintaining, or both producing and maintaining mechanical
oscillations of said four measuring tubes, said exciter
mechanism including a first oscillation exciter and said
exciter mechanism being adapted to excite the first and second
measuring tubes to execute opposite phase bending oscillations
in a shared imaginary first plane of oscillation and to excite
the third and fourth measuring tubes to execute opposite phase
bending oscillations in a shared imaginary, second plane of
oscillation.
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There is also provided an in-line measuring device for
measuring at least one of: a density and a mass flow rate of a
medium flowing in a pipeline, said in-line measuring device
comprising: such a measuring transducer; as well as measuring
device electronics electrically coupled with the measuring
transducer.
Another aspect provides the use of such a measuring transducer,
for measuring at least one of: a density and a mass flow rate
of a medium flowing in a pipeline, at least at times, with a
mass flow rate of more than 2200 t/h.
An embodiment of the invention resides in a measuring
transducer of vibration-type for registering at least one
physical, measured variable of a flowable medium guided in a
pipeline, especially a gas, a liquid, a powder or other
flowable material, and/or for producing Coriolis forces serving
for registering a mass flow rate of a flowable medium guided in
a pipeline, especially a gas, a liquid, a powder or other
flowable material. The measuring transducer comprises,
according to the invention, a, for example, essentially tubular
and/or externally circularly cylindrical, transducer housing,
of which an inlet-side, first housing end is formed by means of
an inlet-side, first flow divider having exactly four, for
example, circularly cylindrical, tapered or conical, flow
openings spaced, in each case, from one another, and an outlet-
side, second housing end is formed by means of an outlet-side,
second flow divider having exactly four, for example,
circularly cylindrical, tapered or conical, flow openings
spaced, in each case, from one another. Furthermore, the
measuring transducer according to the invention comprises
exactly four, straight measuring tubes forming flow paths
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arranged for parallel flow and connected to the, for example,
equally constructed, flow dividers for guiding flowing medium,
especially, measuring tubes held oscillatably in the transducer
housing only by means of said flow dividers and/or equally
constructed and/or at least pairwise parallel relative to one
another. Of the
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four measuring tubes of the measuring transducer of the
invention, a first measuring tube, especially a circularly
cylindrical, first measuring tube, opens with an inlet-side,
first measuring tube end into a first flow opening of the
first flow divider and with an outlet-side, second measuring
tube end into a first flow opening of the second flow
divider, a second measuring tube, especially a circularly
cylindrical, second measuring tube, opens with an inlet-side,
first measuring tube end into a second flow opening of the
first flow divider and with an outlet-side, second measuring
tube end into a second flow opening of the second flow
divider, a third measuring tube, especially a circularly
cylindrical, third measuring tube, opens with an inlet-side,
first measuring tube end into a third flow opening of the
first flow divider and with an outlet-side, second measuring
tube end into a third flow opening of the second flow
divider, and a fourth measuring tube, especially a circularly
cylindrical, fourth measuring tube, opens with an inlet-side,
first measuring tube end into a fourth flow opening of the
first flow divider and with an outlet-side, second measuring
tube end into a fourth flow opening of the second flow
divider.
Additionally, the measuring transducer of the
invention comprises an electromechanical exciter mechanism,
for example, one formed by means of an electrodynamic
oscillation exciter, for producing and/or maintaining
mechanical oscillations, for example, bending oscillations,
of the four measuring tubes, wherein the exciter mechanism is
embodied in such a manner that, therewith, the first
measuring tube and the second measuring tube are excitable,
during operation, to opposite phase, bending oscillations in
a shared, imaginary, first plane of oscillation, and the
third measuring tube and the fourth measuring tube are
excitable, during operation, to opposite phase, bending
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oscillations in a shared, imaginary, second plane of
oscillation, especially a second plane of oscillation
essentially parallel to the first plane of oscillation.
In a first further development of the invention, the
measuring transducer additionally comprises a first coupling
element of first type, especially a plate-shaped first
coupling element of first type, which is affixed at least to
the first measuring tube and to the second measuring tube and
spaced on the inlet side both from the first flow divider as
well as also from the second flow divider for forming inlet-
side, oscillation nodes at least for vibrations, especially
bending oscillations, of the first measuring tube and for
thereto opposite phase vibrations, especially bending
oscillations, of the second measuring tube, as well as a
second coupling element of first type, especially a plate-
shaped second coupling element of first type and/or a second
coupling element constructed equally to the first coupling
element and/or a second coupling element parallel to the
first coupling element, which second coupling element of
first type is affixed at least to the first measuring tube
and to the second measuring tube and spaced on the outlet
side both from the first flow divider as well as also from
the second flow divider, as well as also from the first
coupling element, for forming outlet-side, oscillation nodes
at least for vibrations, especially bending oscillations, of
the first measuring tube and for thereto opposite phase
vibrations, especially bending oscillations, of the second
measuring tube.
In a first embodiment of the first further development
of the invention, it is additionally provided, that all four
measuring tubes are connected with one another mechanically
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by means of the first coupling element of first type as well
as by means of the second coupling element of first type.
In a second embodiment of the first further development
of the invention, it is additionally provided, that the first
coupling element of first type is plate shaped, especially in
such a manner, that it has essentially a rectangular, square,
round, cross shaped or H-shaped basic shape.
In a third embodiment of the first further development
of the invention, it is additionally provided, that the
second coupling element of first type, especially a coupling
element of construction equal to that of the first coupling
element of first type, is plate shaped, especially in such a
manner, that it has a rectangular, square, round, cross
shaped or H-shaped basic shape.
In a fourth embodiment of the first further development
of the invention, it is additionally provided, that the first
coupling element of first type is affixed also to the third
measuring tube and to the fourth measuring tube, and that the
second coupling element of first type is affixed to the third
measuring tube and to the fourth measuring tube.
In a fifth embodiment of the first further development
of the invention, it is additionally provided, that a center
of mass of the first coupling element of first type has a
distance to a center of mass of the measuring transducer,
which is essentially equal to a distance of a center of mass
of the second coupling element of first type to said center
of mass of the measuring transducer.
In a sixth embodiment of the first further development
of the invention, the measuring transducer is additionally so
embodied, that a free, oscillatory length, L18x, of the first
measuring tube, especially of each of the measuring tubes,
corresponding to a minimum separation between the first
coupling element of first type and the second coupling
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element of first type, amounts to less than 2500 mm,
especially less than 2000 mm and/or more than 800 mm.
Especially, the measuring transducer is, in such case,
additionally so embodied, that each of the four measuring
tubes, especially measuring tubes of equal caliber and/or
equal length, has a caliber, which amounts to more than 60
mm, especially more than 80 mm, especially in such a manner,
that a caliber to oscillatory length ratio of the measuring
transducer, as defined by a ratio of the caliber of the first
measuring tube to the free, oscillatory length of the first
measuring tube, amounts to more than 0.07, especially more
than 0.09 and/or less than 0.15.
In supplementation of the first further development of the
invention, it is additionally provided, that the measuring
transducer further comprises a third coupling element of
first type, for example, a plate-shaped, third coupling
element of first type, which is affixed at least to the third
measuring tube and to the fourth measuring tube and spaced on
the inlet side both from the first flow divider as well as
also from the second flow divider, for forming inlet-side,
oscillation nodes at least for vibrations, especially bending
oscillations, of the third measuring tube and for
thereto
opposite phase vibrations, especially bending oscillations,
of the fourth measuring tube, as well as a fourth coupling
element of first type, for example, a plate-shaped, fourth
coupling element of first type, which is affixed at least to
the third measuring tube and to the fourth measuring tube and
spaced on the outlet side both from the first flow divider as
well as also from the second flow divider, as well as also
from the third coupling element of first type, for forming
outlet-side, oscillation nodes at least for vibrations,
especially bending oscillations, of the third measuring tube
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and for thereto opposite phase vibrations, especially bending
oscillations, of the fourth measuring tube. In
such case,
for example, also all four measuring tubes can be connected
with one another mechanically by means of the third coupling
element of first type as well as by means of the fourth
coupling element of first type.
In a second further development of the invention, the
measuring transducer additionally comprises a first coupling
element of second type, for example, a plate shaped or rod
shaped, first coupling element of second type, which is
affixed only to the first measuring tube and to the third
measuring tube and spaced both from the first coupling
element of first type as well as also from the second
coupling element, of first type for synchronizing vibrations,
especially bending oscillations, of the first measuring tube
and thereto equal frequency vibrations, especially bending
oscillations, of the third measuring tube, as well as a
second coupling element of second type, for example, a plate
shaped or rod shaped, second coupling element of second type,
which is affixed only to the second measuring tube and to the
fourth measuring tube and spaced both from the first coupling
element of first type as well as also from the second
coupling element of first type, as well as also from the
first coupling element of second type, especially in such a
manner, that the first and second coupling elements of second
type are placed in the measuring transducer lying opposite
one another, for synchronizing vibrations, especially bending
oscillations, of the second measuring tube and thereto equal
frequency vibrations, especially bending oscillations, of the
fourth measuring tube. In
supplementation thereof, the
measuring transducer can further comprise a third coupling
element of second type, for example, a plate shaped or rod
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,
,
shaped, third coupling element of second type, which is
affixed only to the first measuring tube and to the third
measuring tube and spaced from the first coupling element of
second type, for synchronizing vibrations, especially bending
oscillations, of the first measuring tube and thereto equal
frequency vibrations, especially bending oscillations, of the
third measuring tube, as well as a fourth coupling element of
second type, for example, a plate shaped or rod shaped,
fourth coupling element of second type, which is affixed only
to the second measuring tube and to the fourth measuring tube
and spaced, in each case, from the second and third coupling
elements of second type, especially in such a manner, that
the third and fourth coupling elements of second type are
placed lying opposite one another in the measuring
transducer, for synchronizing vibrations, especially bending
oscillations, of the second measuring tube and thereto equal
frequency vibrations, especially bending oscillations, of the
fourth measuring tube.
Moreover, the measuring transducer can
comprise,
additionally, a fifth coupling element of second type, for
example, a plate shaped or rod shaped, fifth coupling element
of second type, which is affixed only to the first measuring
tube and to the third measuring tube and spaced from the
first and third coupling elements of second type, for
synchronizing vibrations, especially bending oscillations, of
the first measuring tube and thereto equal frequency
vibrations, especially bending oscillations, of the third
measuring tube, as well as a, for example, a plate shaped or
rod shaped, sixth coupling element of second type, which is
affixed only to the second measuring tube and to the fourth
measuring tube and spaced, in each case, from the second,
fourth and fifth coupling elements of second type, especially
in such a manner that the fifth and sixth coupling elements
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of second type are placed in the measuring transducer lying
opposite one another, for synchronizing vibrations,
especially bending oscillations, of the second measuring tube
and thereto equal frequency vibrations, especially bending
oscillations, of the fourth measuring tube.
In a first embodiment of the invention, it is additionally
provided, that each of the four measuring tubes, especially
measuring tubes of equal caliber and/or equal length, has a
caliber, which amounts to more than 60 mm, especially more
than 80 mm.
In a second embodiment of the invention, it is additionally
provided, that the first flow divider has a flange,
especially a flange having mass of more than 50 kg, for
connecting the measuring transducer to a tubular segment of
the pipeline serving for supplying medium to the measuring
transducer and the second flow divider has a flange,
especially a flange having a mass of more than 50 kg, for
connecting the measuring transducer to a segment of the
pipeline serving for removing medium from the measuring
transducer.
Developing this embodiment of the invention
further, each of the flanges has a sealing surface for fluid
tight connecting of the measuring transducer with the, in
each case, corresponding tubular segment of the pipeline,
wherein a distance between the sealing surfaces of both
flanges defines an installed length of the measuring
transducer, especially an installed length amounting to more
than 1200 mm and/or less than 3000 mm.
Especially, the
measuring transducer is additionally so embodied, that, in
such case, a measuring tube length of the first measuring
tube corresponding to a minimum separation between the first
flow opening of the first flow divider and the first flow
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opening of the second flow divider is so selected, that a
measuring tube length to installed length ratio of the
measuring transducer, as defined by a ratio of the measuring
tube length of the first measuring tube to the installed
length of the measuring transducer, amounts to more than 0.7,
especially more than 0.8 and/or less than 0.95, and/or that a
caliber to installed length ratio of the measuring
transducer, as defined by a ratio of the caliber of the first
measuring tube to the installed length of the measuring
transducer, amounts to more than 0.02, especially more than
0.05 and/or less than 0.09.
Alternatively thereto or in
supplementation thereof, the measuring transducer is so
embodied, that a nominal diameter to installed length ratio
of the measuring transducer, as defined by a ratio of the
nominal diameter of the measuring transducer to the installed
length of the measuring transducer, is smaller than 0.3,
especially smaller than 0.2 and/or greater than 0.1, wherein
the nominal diameter corresponds to a caliber of the
pipeline, in whose course the measuring transducer is to be
used.
In a third embodiment of the invention, it is additionally
provided, that a measuring tube length of the first measuring
tube corresponding to a minimum separation between the first
flow opening of the first flow divider and the first flow
opening of the second flow divider amounts to more than 1000
mm, especially more than 1200 mm and/or less than 2000 mm.
In a fourth embodiment of the invention, it is additionally
provided, that each of the four measuring tubes, especially
four measuring tubes of equal caliber, is so arranged, that a
smallest lateral separation of each of the four measuring
tubes, especially measuring tubes of equal length, from a
16
CA 02754788 2011-09-08
housing side wall of the transducer housing is, in each case,
greater than zero, especially greater than 3 mm and/or
greater than twice a respective tube wall thickness; and/or
that a smallest lateral separation between two neighboring
measuring tubes amounts to, in each case, greater than 3 mm
and/or greater than the sum of their respective tube wall
thicknesses.
In a fifth embodiment of the invention, it is additionally
provided, that each of the flow openings is so arranged, that
a smallest lateral separation of each of the flow openings
from a housing side wall of the transducer housing amounts,
in each case, to greater than zero, especially greater than 3
mm and/or greater than twice a smallest tube wall thickness
of the measuring tubes; and/or that a smallest lateral
separation between the flow openings amounts to greater than
3 mm and/or greater than twice a smallest tube wall thickness
of the measuring tubes.
In a third further development of the invention, the
measuring transducer additionally comprises a plurality of
annular stiffening elements, especially equally constructed
stiffening elements, serving for increasing the oscillation
quality factor of the measuring tubes. Each
of the
stiffening elements is so placed on exactly one of the
measuring tubes that it grips around such along one of the
peripheral lines of the measuring tube.
According to an
embodiment of the third further development of the invention,
there are placed on each of the measuring tubes at least four
annular stiffening elements, for example, equally constructed
stiffening elements, especially in such a manner, that the
stiffening elements are so placed in the measuring
transducer, that two adjoining stiffening elements mounted on
17
CA 02754788 2011-09-08
the same measuring tube have, relative to one another, a
separation, which amounts to at least 70% of a tube outer
diameter of said measuring tube, at most, however, 150% of
such tube outer diameter, for example, a separation in the
range of 80% to 120% of such tube outer diameter.
In a fourth further development of the invention, the
measuring transducer additionally comprises a sensor
arrangement for producing oscillation measurement signals
representing vibrations, especially bending oscillations, of
the measuring tubes, by reacting to vibrations of the
measuring tubes, especially bending oscillations excited by
means of the exciter mechanism. The
sensor arrangement is,
for example, an electrodynamic sensor arrangement and/or is
formed by means of oscillation sensors constructed equally to
one another.
In a first embodiment of the fourth further development
of the invention, it is provided, that the sensor arrangement
is formed by means of an inlet-side, first oscillation
sensor, especially an electrodynamic, first oscillation
sensor and/or a first oscillation sensor differentially
registering oscillations of the first measuring tube relative
to the second measuring tube, as well as by means of an
outlet-side, second oscillation sensor, especially an
electrodynamic, second oscillation sensor and/or a second
oscillation sensor differentially registering oscillations of
the first measuring tube relative to the second measuring'
tube, especially in such a manner that a measuring length of
the measuring transducer corresponding to a minimum
separation between the first oscillation sensor and the
second oscillation sensor amounts to more than 500 mm,
especially more than 600 mm and/or less than 1200 mm, and/or
in such a manner that a caliber to measuring length ratio of
18
CA 02754788 2011-09-08
,
the measuring transducer, as defined by a ratio of a caliber
of the first measuring tube to the measuring length of the
measuring transducer, amounts to more than 0.05, especially
more than 0.09.
Additionally, the first oscillation sensor
can be formed by means of a permanent magnet held on the
first measuring tube and a cylindrical coil permeated by the
magnetic field of the permanent magnet and held on the second
measuring tube, and the second oscillation sensor by means of
a permanent magnet held on the first measuring tube and a
cylindrical coil permeated by the magnetic field of the
permanent magnet and held on the second measuring tube.
In a second embodiment of the fourth further development
of the invention, it is additionally provided, that the
sensor arrangement is formed by means of an inlet-side, first
oscillation sensor, especially an electrodynamic, first
oscillation sensor and/or a first oscillation sensor
differentially registering oscillations of the first
measuring tube relative to the second measuring tube, by an
outlet-side, second oscillation sensor, especially an
electrodynamic, second oscillation sensor and/or a second
oscillation sensor differentially registering oscillations of
the first measuring tube relative to the second measuring
tube, by an inlet-side, third oscillation sensor, especially
an electrodynamic, third oscillation sensor and/or a third
oscillation sensor differentially registering oscillations of
the third measuring tube relative to the fourth measuring
tube, as well as by an outlet-side, fourth oscillation
sensor, especially an electrodynamic, fourth oscillation
sensor and/or a fourth oscillation sensor differentially
registering oscillations of the third measuring tube relative
to the fourth measuring tube, especially in such a manner,
that a measuring length of the measuring transducer
corresponding to a minimum separation between the first
19
CA 02754788 2011-09-08
oscillation sensor and the second oscillation sensor amounts
to more than 500 mm, especially more than 600 mm and/or less
than 1200 mm, and/or in such a manner that a caliber to
measuring length ratio of the measuring transducer, as
defined by a ratio of a caliber of the first measuring tube
to the measuring length of the measuring transducer, amounts
to more than 0.05, especially more than 0.09. In
such case,
in advantageous manner, the first and third oscillation
sensors can be interconnected electrically in series in such
a manner, that a combined oscillation measurement signal
represents combined inlet-side oscillations of the first and
third measuring tubes relative to the second and fourth
measuring tube, and/or the second and fourth oscillation
sensors can be interconnected electrically in series in such
a manner, that a combined oscillation measurement signal
represents combined outlet-side oscillations of the first and
third measuring tubes relative to the second and fourth
measuring tube.
Alternatively or in supplementation, the
first oscillation sensor can further be formed by means of a
permanent magnet held on the first measuring tube and a
cylindrical coil permeated by the magnetic field of the
permanent magnet and held on the second measuring tube, and
the second oscillation sensor by means of a permanent magnet
held on the first measuring tube and a cylindrical coil
permeated by the magnetic field of the permanent magnet and
held on the second measuring tube, and/or the third
oscillation sensor by means of a permanent magnet held on the
third measuring tube and a cylindrical coil permeated by the
magnetic field of the permanent magnet and held on the fourth
measuring tube and the fourth oscillation sensor by means of
a permanent magnet held on the third measuring tube and a
cylindrical coil permeated by the magnetic field of the
permanent magnet and held on the fourth measuring tube.
CA 02754788 2011-09-08
In a sixth embodiment of the invention, it is additionally
provided, that a mass ratio of an empty mass of the total
measuring transducer to an empty mass of the first measuring
tube is greater than 10, especially greater than 15 and
smaller than 25.
In a seventh embodiment of the invention, it is additionally
provided, that an empty mass, M18, of the first measuring
tube, especially each of the measuring tubes, is greater than
20 kg, especially greater than 30 kg and/or smaller than 50
kg.
According to an eighth embodiment of the invention, it is
additionally provided, that an empty mass of the measuring
transducer is greater than 200 kg, especially greater than
300 kg.
In a ninth embodiment of the invention, it is additionally
provided, that a nominal diameter of the measuring
transducer, which corresponds to a caliber of the pipeline,
in whose course the measuring transducer is to be used,
amounts to more than 100 mm, especially greater than 300 mm.
In advantageous manner, the measuring transducer is
additionally so embodied, that a mass to nominal diameter
ratio of the measuring transducer, as defined by a ratio of
the empty mass of the measuring transducer to the nominal
diameter of the measuring transducer, is smaller than 2
kg/mm, especially smaller than 1 kg/mm and/or greater than
0.5 kg/mm.
In a tenth embodiment of the invention, it is additionally
provided, that the first and the second measuring tubes are
21
CA 02754788 2011-09-08
of equal construction, at least as regards a material, of
which their tube walls are, in each case, composed, and/or as
regards their geometrical tube dimensions, especially a tube
length, a tube wall thickness, a tube outer diameter and/or a
caliber.
According to an eleventh embodiment of the invention, it is
additionally provided, that the third and fourth measuring
tubes are of equal construction, at least as regards a
material, of which their tube walls are, in each case,
composed, and/or as regards their geometric tube dimensions,
especially a tube length, a tube wall thickness, a tube outer
diameter and/or a caliber.
In a twelfth embodiment of the invention, it is additionally
provided, that the four measuring tubes are of equal
construction, as regards a material, of which their tube
walls are composed, and/or as regards their geometric tube
dimensions, especially a tube length, a tube wall thickness,
a tube outer diameter and/or a caliber. It
can, however,
also be of advantage, when, alternatively thereto, both the
third measuring tube as well as also the fourth measuring
tube are different from the first measuring tube and from the
second measuring tube as regards their respective geometric
tube dimensions, especially a tube length, a tube wall
thickness, a tube outer diameter and/or a caliber.
In a thirteenth embodiment of the invention, it is
additionally provided, that a material, of which the tube
walls of the four measuring tubes are at least partially
composed, is titanium and/or zirconium and/or duplex steel
and/or super duplex steel.
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CA 02754788 2011-09-08
In a fourteenth embodiment of the invention, it is
additionally provided, that the transducer housing, the flow
dividers and tube walls of the measuring tubes are, in each
case, composed of steel, for example, stainless steel.
In a fifteenth embodiment of the invention, it is
additionally provided, that the minimum bending oscillation,
resonance frequencies at least of the first and second
measuring tubes are essentially equal and the minimum bending
oscillation, resonance frequencies at least of the third and
fourth measuring tubes are essentially equal. In
such case,
the minimum bending oscillation, resonance frequencies of all
four measuring tubes can be essentially equal or, however,
also kept only pairwise equal.
In a sixteenth embodiment of the invention, it is
additionally provided, that the four flow openings of the
first flow divider are so arranged, that imaginary areal
centers of gravity associated with the cross sectional areas,
especially circularly shaped cross sectional areas, of the
flow openings of the first flow divider form the vertices of
an imaginary square, wherein such cross sectional areas lie
in a shared, imaginary cutting plane of the first flow
divider extending perpendicularly to a longitudinal axis of
the measuring transducer, especially a longitudinal axis
parallel to a principal flow axis of the measuring
transducer.
In a seventeenth embodiment of the invention, it is
additionally provided, that the four flow openings of the
second flow divider are so arranged, that imaginary areal
centers of gravity associated with the cross sectional areas,
especially circularly shaped cross sectional areas, of the
23
CA 02754788 2011-09-08
flow openings of the second flow divider form the vertices of
an imaginary square, wherein such cross sectional areas lie
in a shared, imaginary cutting plane of the second flow
divider extending perpendicularly to a longitudinal axis of
the measuring transducer, especially a longitudinal axis
parallel to a principal flow axis of the measuring
transducer.
According to an eighteenth embodiment of the invention, it is
additionally provided, that the exciter mechanism is formed
by means of a first oscillation exciter, especially an
electrodynamic, first oscillation exciter and/or a first
oscillation exciter differentially exciting oscillations of
the first measuring tube relative to the second measuring
tube.
Especially, the exciter mechanism is formed by means
of a second oscillation exciter, for example, an
electrodynamic second oscillation exciter and/or a second
oscillation exciter differentially exciting oscillations of
the third measuring tube relative to the fourth measuring
tube. In
such case, it is additionally provided, that the
first and second oscillation exciters are interconnected
electrically in series, in such a manner, that a combined
driver signal excites combined oscillations of the first and
third measuring tubes relative to the second and fourth
measuring tube. The
oscillation exciter of the exciter
mechanism can be formed, for example, by means of a permanent
magnet held on the first measuring tube and a cylindrical
coil permeated by the magnetic field of the permanent magnet
and held on the second measuring tube, and wherein the second
oscillation exciter is formed by means of a permanent magnet
held on the third measuring tube and a cylindrical coil
permeated by the magnetic field of the permanent magnet and
held on the fourth measuring tube.
24
CA 02754788 2013-09-16
78639-48
In a nineteenth embodiment of the invention, it is
additionally provided, that. a middle segment of the
transducer housing is formed by means of a straight tube, for
example, a circularly cylindrical, straight tube.
In a twentieth embodiment of the invention, it is
additionally provided, that the transducer housing is
essentially tubularly embodied, for example, circularly
cylindrically embodied. In
such case, it is additionally
provided, that the transducer housing has a largest housing
inner diameter, which is greater than 150 mm, especially
greater than 250 mm, especially in such a manner, that a
housing to measuring tube inner diameter ratio of the
measuring transducer, as defined by a ratio of the largest
housing inner diameter to a caliber of the first measuring
tube is kept greater than 3, especially greater than 4 and/or
smaller than 5, and/or that a housing inner diameter to
nominal diameter ratio of the measuring transducer, as
defined by a ratio of the largest housing inner diameter to
the nominal diameter of the measuring transducer is smaller
than 1.5, especially. smaller :than 1.2 and/or greater than
0.9, wherein the nominal diameter corresponds to a caliber of
the pipeline, in whose course the measuring transducer is to
be used. The
housing inner diameter to nominal diameter
ratio of the measuring transducer can, in such case, in
advantageous manner, be, for example, also equal to one.
Moreover, an embodiment of the invention resides in an in-line
measuring device for measuring a density and/or a mass flow rate,
especially also a total mass flow totaled over a time
= interval, of a medium, especially of a gas, a liquid, a
powder or other flowable material flowing in a pipeline, at
CA 02754788 2013-09-16
78639-48
least at times, especially with a mass flow rate of more than
2200 t/h, which in-line measuring device, especially an in-
line measuring device embodied as a compact device, comprises
one of the aforementioned measuring transducers as well as a
measuring device electronics electrically coupled with the
measuring transducer, especially also a measuring device
electronics mechanically rigidly connected with the measuring
transducer.
A basic idea of an embodiment of the invention is to use, instead of
the two measuring tubes, through which the medium flows in parallel,
as used in the case of conventional measuring transducers of
large nominal diameter, four straight measuring tubes,
through which the medium flows in parallel, and so, on the
one hand, to enable an optimal exploitation of the limited
offering of space, while, on the other hand, being able to -
assure an acceptable pressure loss over a broad measuring
range, especially also in the case of very high,, mass flow
rates of far over 2200 t/h. Moreover, the effective flow
cross section of the inner part resulting from the total
cross section of the four measuring tubes can, in comparison
to conventional measuring transducers of equal nominal
diameter and equal empty .mass having only two measuring
tubes, be directly increased by more than 20%.
A possible advantage of the measuring transducer of an embodiment of
the invention resides additionally in the fact that predominantly
established, structural designs, such as regards materials
used, joining technology, manufacturing steps, etc., can be
applied, or must only be slightly modified, whereby also
manufacturing costs are, in total, quite comparable to those
of conventional measuring transducers. As a result, a further possible
advantage of an embodiment of the invention is to be found in the fact
26
CA 02754788 2013-09-16
78639-48
chat, thereby, not only an opportunity is created
implementing comparatively compact measuring transducers of
vibration-type also with large nominal diameters of over 150
mm, especially with a nominal diameter of larger 250 mm, with
manageable geometric dimensions and empty dimensions, but,
additionally, also; this can be accomplished in an
economically sensible manner.
The measuring transducer of an embodiment of the invention may be,
consequently, especially suitable for measuring flowable media
guided in a pipeline having a caliber of larger 150 mm, especially
of 300 mm or greater. Additionally, the measuring transducer may
also be suitable for measuring also mass flows, which are, at
least at times, greater than 2200 t/h, especially, at least
at times, amounting to more than 2400 t/h, such as can occur
e.g. in the case of applications for measuring petroleum,
natural gas or other petrochemical materials.
The invention, as Well as other advantageous embodiments
thereof, will now be explained in greater detail on the basis
of examples of embodiments presented in the figures of the
drawing. Equal parts are provided in the figures with equal
reference characters; when required to avoid clutter or when
it otherwise appears sensible, already mentioned reference
characters are omitted in subsequent figures.
Other
advantageous embodiments or =further developments, especially
also combinations of first only individually explained
aspects of the invention, will become evident additionally
from the figures of the drawing, as well as also alone from
the dependent claims.
In particular, the figures of the drawing show as follows:
27
CA 02754788 2011-09-08
Figs. 1,2 an in-line measuring device serving, for example,
as a Coriolis flow/density/viscosity transducer,
in perspective, also partially sectioned, side
views;
Figs. 3a,b a projection of the in-line measuring device of
Fig. 1 in two different side views;
Fig. 4 in perspective, side view, a measuring transducer
of vibration-type, installed in an in-line
measuring device of Fig. 1;
Figs. 5a,b a projection of the measuring transducer of Fig.
4 in two different side views; and
Figs. 6a,b projections of an inner part of the measuring
transducer of Fig. 4 in two different side views.
Figs. 1, 2 show, schematically, an in-line measuring device
1, especially an in-line measuring device embodied as a
Coriolis, mass flow, and/or density, measuring device, which
serves for registering a mass flow m of a medium flowing in a
pipeline (not shown) and for representing such in a mass
flow, measured value representing this mass flow
instantaneously. The medium can be practically any flowable
material, for example, a powder, a liquid, a gas, a vapor, or
the like. Alternatively or in supplementation, the in-line
measuring device 1 can, in given cases, also be used for
measuring a density p and/or a viscosity q of the medium.
Especially, the in-line measuring device is provided for
measuring media, such as e.g. petroleum, natural gas or other
petrochemical materials, which are flowing in a pipeline
having a caliber greater than 250 mm, especially a caliber of
28
CA 02754788 2011-09-08
300 mm or more. Especially, the in-line measuring device is
additionally provided for measuring flowing media of the
aforementioned type, which are caused to flow with a mass
flow rate of greater than 2200 t/h, especially greater than
2500 t/h.
The in-line measuring device 1 comprises, for such purpose: A
measuring transducer 11 of vibration-type, through which the
medium being measured flows, during operation; as well as,
electrically connected with the measuring transducer 11, a
measuring device electronics 12, which is here not shown in
detail, but, instead only schematically in the form of a
contained unit. In
advantageous manner, the measuring
device electronics 12 is so designed that, during operation
of the in-line measuring device 1, it can exchange measuring,
and/or other operating, data with a measured value processing
unit superordinated to it, for example, a programmable logic
controller (PLC), a personal computer and/or a work station,
via a data transmission system, for example, a hardwired
fieldbus system and/or wirelessly per radio.
Furthermore,
the measuring device electronics 12 is so designed, that it
can be fed by an external energy supply, for example, also
via the aforementioned fieldbus system. For
the case, in
which the in-line measuring device 1 is provided for coupling
to a fieldbus, or other communication, system, the measuring
device electronics 12, especially a programmable measuring
device electronics, includes, additionally, a corresponding
communication interface for data communication, e.g. for
sending the measured data to the already mentioned,
programmable logic controller or a superordinated process
control system.
29
CA 02754788 2011-09-08
Figs. 4, 5a, 5b, 6a, 6b show different representations of an
example of an embodiment for a measuring transducer 11 of
vibration-type suited for the in-line measuring device 1,
especially one serving as a Coriolis, mass flow, density
and/or viscosity, transducer, which measuring transducer 11
is applied, during operation, in the course of a pipeline
(not shown), through which a medium to be measured, for
example, a powdered, liquid, gaseous or vaporous medium, is
flowing. The
measuring transducer 11 serves to produce, as
already mentioned, in a medium flowing therethrough, such
mechanical reaction forces, especially Coriolis forces
dependent on mass flow, inertial forces dependent on density
of the medium and/or frictional forces dependent on viscosity
of the medium, which react measurably, especially
registerably by sensor, on the measuring transducer. Derived
from these reaction forces describing the medium, by means of
evaluating methods correspondingly implemented in the
measuring device electronics in manner known to those skilled
in the art, e.g. the mass flow, the density and/or the
viscosity of the medium can be measured.
The measuring transducer 11 includes a transducer housing 71,
which is, here, essentially tubular, and externally
circularly cylindrical, and which serves, among other things,
also as a support frame, in which other components of the
measuring transducer 11 serving for registering the at least
one measured variable are accommodated to be protected
against external, environmental influences. In
the example
of an embodiment shown here, at least one middle segment of
the transducer housing 71 is formed by means of a straight,
especially circularly cylindrical, tube, so that, for
manufacture of the transducer housing, for example, also cost
CA 02754788 2011-09-08
effective, welded or cast, standard tubes, for example, of
cast steel or forged steel, can be used.
An inlet-side, first housing end of the transducer housing 71
is formed by means of an inlet-side, first flow divider 201
and an outlet-side, second housing end of the transducer
housing 71 is formed by means of outlet-side, second flow
divider 202. Each
of the two flow dividers 201, 202, which
are, in this respect, formed as integral components of the
housing, includes exactly four, for example, circularly
cylindrical or tapered or conical, flow openings 201A. 2012,
201c, 201D, or 202A, 2022, 2020, 202D, each spaced from one
another and/or each embodied as an inner cone.
Moreover, each of the flow dividers 201, 202, for example,
manufactured of steel, is provided with a flange 61, or 62,
for example, manufactured of steel, for connecting of the
measuring transducer 11 to a tubular segment of the pipeline
serving for supplying medium to the measuring transducer, or
to a tubular segment of such pipeline serving for removing
medium from the measuring transducer. Each
of the two
flanges 61, 62 has, according to an embodiment of the
invention, a mass of more than 50 kg, especially more than 60
kg and/or less than 100 kg. For
leakage free, especially
fluid tight, connecting of the measuring transducer with the,
in each case, corresponding tubular segment of the pipeline,
each of the flanges includes additionally, in each case, a
corresponding, as planar as possible, sealing surface 61A, or
62A= A
distance between the two sealing surfaces 61A, 62A of
both flanges defines, thus, for practical purposes, an
installed length, 1,11, of the measuring transducer 11. The
flanges are dimensioned, especially as regards their inner
diameter, their respective sealing surface as well as the
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CA 02754788 2011-09-08
flange bores serving for accommodating corresponding
connection bolts, according to the nominal diameter D11
provided for the measuring transducer 11 as well as the
therefor, in given cases, relevant industrial standards,
corresponding to a caliber of the pipeline, in whose course
the measuring transducer is to be used.
As a result of the large nominal diameter lastly desired for
the measuring transducer, its installed length Lll amounts,
according to an embodiment of the invention, to more than
1200 mm.
Additionally, it is, however, provided that the
installed length of the measuring transducer 11 is kept as
small as possible, especially smaller than 3000 mm. The
flanges 61, 62 can, as well as also directly evident from Fig.
4 and such as quite usual in the case of such measuring
transducers, be arranged, for this purpose, as near as
possible to the flow openings of the flow dividers 201, 202,
in order so to provide an as short as possible inlet, or
outlet, as the case may be, region in the flow dividers and,
thus, in total, to provide an as short as possible installed
length 1,11 of the measuring transducer, especially an
installed length Lll of less than 3000 mm. For an as compact
as possible measuring transducer with an also in the case of
desired high mass flow rates of over 2200 t/h, according to
another embodiment of the invention, the installed length and
the nominal diameter of the measuring transducer are so
dimensioned, matched to one another, that a nominal diameter
to installed length ratio 1D11/ Lll of the measuring transducer,
as defined by a ratio of the nominal diameter D11 of the
measuring transducer to the installed length L11 of the
measuring transducer is smaller than 0.3, especially smaller
than 0.2 and/or greater than 0.1.
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CA 02754788 2011-09-08
In an additional embodiment of the measuring transducer, the
transducer housing comprises an essentially tubular, middle
segment.
Additionally, it is provided that the transducer
housing is so dimensioned, that a housing inner diameter to
nominal diameter ratio of the measuring transducer defined by
a ratio of the largest housing inner diameter to the nominal
diameter of the measuring transducer is, indeed, greater than
0.9, however, smaller than 1.5, as much as possible, however,
smaller than 1.2.
In the case of the here illustrated example of an embodiment,
there adjoin on the inlet and outlet sides of the middle
segment, additionally, likewise tubular end segments of the
transducer housing. For the case illustrated in the example
of an embodiment, in which the middle segment and the two end
segments, as well as also the flow dividers connected with
the respective flanges in the inlet and outlet regions all
have the same inner diameter, the transducer housing can in
advantageous manner also be formed by means of a one piece,
for example, cast or forged, tube, on whose ends the flanges
are formed or welded, and in the case of which the flow
dividers are formed by means of plates having the flow
openings, especially plates somewhat spaced from the flanges
and welded to the inner wall orbitally and/or by means of
laser.
Especially for the case, in which the mentioned
housing inner diameter to nominal diameter ratio of the
measuring transducer is selected equal to one, for
manufacture of the transducer housing, for example, a tube
matched to the pipeline to be connected to as regards
caliber, wall thickness and material and, in that respect,
also as regards the allowed operating pressure and having a
length correspondingly matching the selected measuring tube
length can be used. For
simplifying the transport of the
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CA 02754788 2011-09-08
measuring transducer, or the totally therewith formed, in-
line measuring device, additionally, such as, for example,
also provided in the initially mentioned US-B 7,350,421,
transport eyes can be provided affixed on the inlet side and
on the outlet side externally on the transducer housing.
For conveying the medium flowing, at least at times, through
pipeline and measuring transducer, the measuring transducer
of the invention comprises, additionally, exactly four,
straight, measuring tubes 181, 182, 183, 184 held oscillatably
in the transducer housing 10, especially measuring tubes 181,
182, 183, 184, which are parallel relative to one another
and/or equally long, which, during operationõ in each case,
communicate with the pipeline and, at least at times, are
caused to vibrate in at least one oscillatory mode, the so-
called wanted mode, suited for ascertaining the physical,
measured variable.
Especially suited as wanted mode and
naturally inherent to each of the measuring tubes 181, 182,
183, and 184 is a bending oscillation, fundamental mode, which
at a minimum bending oscillation, resonance frequency, f181,
f182 f183 r or f184 has exactly one oscillatory antinode.
Of the four - here essentially circularly cylindrical, of
equal length and parallel relative to one another as well as
to the above mentioned, middle tubular segment of the
transducer housing - measuring tubes, a first measuring tube
181 opens with an inlet-side, first measuring tube end into a
first flow opening 201A of the first flow divider 201 and with
an outlet-side, second measuring tube end into a first flow
opening 202A of the second flow divider 202, a second
measuring tube 182 opens with an inlet-side, first measuring
tube end into a second flow opening 201B of the first flow
divider 201 and with an outlet-side, second measuring tube end
34
CA 02754788 2011-09-08
into a second flow opening 202B of the second flow divider
202, a third measuring tube 183 opens with an inlet-side,
first measuring tube end into a third flow opening 201c of the
first flow divider 201 and with an outlet-side, second
measuring tube end into a third flow opening 2020 of the
second flow divider 202 and a fourth measuring tube 184 opens
with an inlet-side, first measuring tube end into a fourth
flow opening 201D of the first flow divider 201 and with an
outlet-side, second measuring tube end into a fourth flow
opening 2020 of the second flow divider 202. The
four
measuring tubes 181, 182, 183, 184 are, thus, connected to the
flow dividers 201, 202, especially equally constructed flow
dividers 201, 202, to form flow paths connected in parallel,
and, indeed, in a manner enabling vibrations, especially
bending oscillations, of the measuring tubes relative to one
another, as well as also relative to the transducer housing.
Additionally, it is provided, that the four measuring tubes
181, 182, 183, 184 are held oscillatably in the transducer
housing 71 only by means of said flow dividers 201, 202.
The measuring tubes 181, 182, 183, 184, or a therewith formed,
inner part of the measuring transducer 11, are, such as
directly evident from the combination of Figs. 1, 2 and 4 and
such as also usual in the case of such measuring transducers,
encased by the transducer housing 71, in the illustrated case
practically completely. Transducer housing 71 serves, in this
regard, thus not only as support frame or holder of the
measuring tubes 181, 182, 183, 184, but also for protecting
them, as well as also other components of the measuring
transducer placed within the transducer housing 71, from
external environmental influences, such as e.g. dust or water
spray. Moreover, the transducer housing 71 can additionally
also be so embodied and so dimensioned, that it can, in the
CA 02754788 2011-09-08
case of possible damage to one or a plurality of the
measuring tubes, e.g. through crack formation or bursting,
completely retain outflowing medium up to a required maximum
positive pressure in the interior of the transducer housing 71
as long as possible, wherein such critical state can, such
as, for example, also indicated in the initially mentioned
US-B 7,392,709, be registered and signaled by means of
corresponding pressure sensors and/or on the basis of
operating parameters produced internally, during operation,
by the mentioned measuring device electronics. Used
as
material for the transducer housing 71 can be, accordingly,
especially, steels, such as, for instance, structural steel,
or stainless steel, or also other suitable, or usually
suitable for this application, high strength materials.
According to an embodiment of the invention, the four
measuring tubes 181, 182, 183, 184 are additionally so embodied
and so installed in the measuring transducer 11, that at
least the minimum bending oscillation, resonance frequencies
fln, f182 of the first and second measuring tubes 181, 182 are
essentially equal and at least the minimum bending
oscillation, resonance frequencies f183, f184 of the third and
fourth measuring tubes 183, 184 are essentially equal.
According to an additional embodiment of the invention, at
least the first and second measuring tubes 181, 182 are of
equal construction as regards a material, of which their tube
walls are composed, and/or as regards their geometric tube
dimensions, especially a tube length, a tube wall thickness,
a tube outer diameter and/or a caliber. Additionally, also
at least the third and fourth measuring tubes 183, 184 are of
equal construction as regards a material, of which their tube
walls are composed, and/or as regards their geometric tube
36
CA 02754788 2011-09-08
dimensions, especially a tube length, a tube wall thickness,
a tube outer diameter and/or a caliber, so that, as a result,
the four measuring tubes 181, 182, 183, 184 are, at least
pairwise, essentially of equal construction. According to an
additional embodiment of the invention, it is, in such case,
additionally provided, to construct both the third measuring
tube as well as also the fourth measuring tube, such that the
two measuring tubes are different from the first measuring
tube and from the second measuring tube, as regards their
respective geometric tube dimensions, especially a tube
length, a tube wall thickness, a tube outer diameter and/or a
caliber, especially in such a manner, that the minimum
bending oscillation, resonance frequencies of the four
measuring tubes are only pairwise equal. Through the, thus,
created symmetry breaking in the case of the four measuring
tubes 181, 182, 183, 184, among other things, the sensitivity,
the oscillatory behavior, especially the mechanical
eigenfrequencies, and/or the cross sensitivity to the
primary, measuring influencing, disturbance variables, such
as, for instance, a temperature, or pressure, distribution,
the loading of the medium with impurities, etc., of the two,
in this respect, mutually different, measuring tube pairs 181,
182, or 183, 184, can be matched, with targeting, to one
another and, thus, an improved diagnosis of the measuring
transducer, during operation, can be enabled. Of course, the
four measuring tubes 181, 182, 183, 184 can, in case required,
however, also be of equal construction as regards a material,
of which their tube walls are composed, and/or as regards
their geometric tube dimensions, especially a tube length, a
tube wall thickness, a tube outer diameter and/or a caliber,
especially in such a manner, that, as a result, the minimum
bending oscillation, resonance frequencies of all four
measuring tubes 181, 182, 183, 184 are essentially equal.
37
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Suited as material for the tube walls of the measuring tubes
is, again, especially, titanium, zirconium or tantalum.
However, serving as material for the four measuring tubes 181,
182, 183, 184 can be also practically any other therefor
usually applied, or at least suitable, material, especially
such with a thermal expansion coefficient as small as
possible and a yield point as high as possible. For
most
applications of industrial measurements
technology,
especially also in the petrochemical industry, consequently,
also measuring tubes of stainless steel, for example, also
duplex steel or super duplex steel, would satisfy the
requirements as regards mechanical strength, chemical
resistance as well as thermal requirements, so that in
numerous cases of application of the transducer housing 71,
the flow dividers 201, 202, as well as also the tube walls of
the measuring tubes 181, 182, 183, 184 can, in each case, be
made of steel of, in each case, sufficiently high quality,
this being of advantage, especially as regards material, and
manufacturing, costs, as well as also as regards the
thermally related dilation behavior of the measuring
transducer 11, during operation.
In an additional advantageous embodiment of the invention,
the flow openings of the first flow divider 201 are
additionally so arranged, that imaginary areal centers of
gravity, which belong to the cross sectional areas, here,
circularly shaped cross sectional areas, of the flow openings
of the first flow divider lying in a shared, imaginary,
cutting plane of the first flow divider extending
perpendicularly to a longitudinal axis of the measuring
transducer, especially a longitudinal axis parallel to a
principal flow axis of the measuring transducer, form the
38
CA 02754788 2011-09-08
vertices of an imaginary square.
Additionally, the flow
openings of the second flow divider 202 are so arranged, that
imaginary areal centers of gravity belonging to the, here,
likewise circularly shaped, cross sectional areas of the flow
openings of the second flow divider 202 form the vertices of
an imaginary square, wherein such cross sectional areas lie,
in turn, in a shared, imaginary, cutting plane of the second
flow divider extending perpendicularly to a longitudinal axis
of the measuring transducer, especially a longitudinal axis
parallel to a principal flow axis of the measuring
transducer. As a result of this, an envelope the four
measuring tubes 181, 182, 183, 184 forms essentially a right
cuboid-like body with a square-like base having a quadruple
symmetry, whereby the space requirement of the inner part
formed by means of the four measuring tubes 181, 182, 183, 184
can be minimized in a manner supporting the compactness of
the measuring transducer 11 as a whole.
According to an additional embodiment of the invention, each
of the measuring tubes is additionally so arranged in the
measuring transducer, that a smallest lateral separation of
each of the four measuring tubes (here, of equal length) from
a housing side wall of the transducer housing is, in each
case, greater than zero, especially, however, greater than 3
mm and/or greater than twice a respective tube wall
thickness, or that a smallest lateral separation between two
neighboring measuring tubes is, in each case, greater than 3
mm and/or greater than the sum of their respective tube wall
thicknesses. Accordingly, additionally, each of the flow
openings is so arranged, that a smallest lateral separation
of each of the flow openings from a housing side wall of the
transducer housing 71 is, in each case, greater than zero,
especially greater than 3 mm and/or greater than twice a
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CA 02754788 2011-09-08
smallest tube wall thickness of the measuring tubes 181, 182,
183, 184, or that a smallest lateral separation between the
flow openings is greater than 3 mm and/or greater than twice
a smallest tube wall thickness of the measuring tubes 181.
182, 183, 184. For
such purpose, according to an additional
embodiment of the invention, the four measuring tubes 181,
182, 183, 184 and the transducer housing 71 are so dimensioned
and matched to one another, that a housing to measuring tube,
inner diameter ratio of the measuring transducer, as defined
by a ratio of the largest housing inner diameter to a caliber
at least of the first measuring tube is greater than 3,
especially greater than 4 and/or smaller than 5.
As already initially mentioned, in the case of the measuring
transducer 11, the reaction forces required for the measuring
are effected in the medium being measured by causing the
measuring tubes 181, 182, 183, 184 to oscillate in the so-
called wanted mode. For
such purpose, the measuring
transducer comprises additionally an exciter mechanism 5
formed by means of at least one electromechanical, for
example, electrodynamic, oscillation exciter acting on the
measuring tubes 181, 182, 183, 184, and serving for causing
each of the measuring tubes, operationally, at least at
times, to execute, and to maintain, oscillations suitable, in
each case, for the particular measuring, especially bending
oscillations, in the so-called wanted mode, with, in each
case, sufficiently large oscillation amplitude for producing
and registering the above named reaction forces in the
medium. The at least one oscillation exciter serves, in such
case, especially for converting an electrical excitation
power P
- exc fed from a corresponding measuring, and operating,
circuit e.g. of the above named Coriolis, mass flow meter
into such, e.g. pulsating or harmonic, exciter forces Fexc,
CA 02754788 2011-09-08
which act, as simultaneously as possible, uniformly, however,
with opposite sense, on the measuring tubes. The
exciter
forces Fexc can be tuned, in manner known, per se, to those
skilled in the art, by means provided in the already
mentioned measuring, and operating, electronics, e.g. by
means of an electrical current, and/or voltage, control
circuit, as regards their amplitude, and e.g. by means of
phase control loop (LL), as regards their frequency;
compare., for this, for example, also US-A 4,801,897 or US-B
6,311,136.
As a result of medium flowing through the measuring tubes
excited to oscillations in the wanted mode, there are induced
in the medium Coriolis forces, which, in turn, effect
deformations of the measuring tubes corresponding to an
additional, higher oscillation mode of the measuring tubes,
the so-called Coriolis mode. For
example, the measuring
tubes 181, 182, 183, 184 can, during operation, be excited, by
the electromechanical exciter mechanism acting thereon, to
bending oscillations, especially to an instantaneous
mechanical eigenfrequency of the inner part formed by means
of the four measuring tubes 181, 182, 183, 184, in the case of
which they are - at least predominantly - laterally deflected
in respective planes of oscillation and, such as directly
evident from the combination of Figs. 3a, 3b, or 6a, 6b, are
caused to oscillate pairwise in a shared plane of oscillation
XZ1, or XZ2, relative to one another with essentially opposite
phase.
This, in particular, in such a manner, that
vibrations executed by each of the measuring tubes 181, 182,
183, 184, during operation, simultaneously, are developed, at
least at times, and/or at least partially, in each case, as
bending oscillations about an imaginary, measuring tube
longitudinal axis connecting the first and the, in each case,
41
CA 02754788 2011-09-08
associated second measuring tube end of the respective
measuring tube, wherein the four measuring tube longitudinal
axes extend, in the here illustrated example of an embodiment
with four mutually parallel measuring tubes 181, 182, 183, 184
equally parallel relative to one another, such as do the
measuring tubes 181, 182, 183, 184, and, moreover, also
essentially parallel to an imaginary longitudinal axis of the
total measuring transducer imaginarily connecting the two
flow dividers and extending through a center of mass of the
measuring transducer. In
other words, the measuring tubes
can, such as quite usual in the case of measuring transducers
of vibration-type, in each case, at least sectionally, be
caused to oscillate in a bending oscillation mode in the
manner of a string clamped on both ends. Accordingly, in an
additional embodiment, the first and second measuring tubes
181, 182 are caused, in each case, to execute bending
oscillations, which lie in a shared first plane of
oscillation XZ1, and, thus, are essentially coplanar.
Additionally, it is provided that the third and fourth
measuring tubes 183, 184 equally oscillate in a shared, second
plane of oscillation XZ2, especially one essentially parallel
to the first plane of oscillation XZ1, with opposite phase
relative to one another; compare, for this, also Figs. 6a,
6b.
In an additional embodiment of the invention, the measuring
tubes 181, 182, 183, 184 are excited by means of the exciter
mechanism 5, during operation, at least partially, especially
predominantly, to bending oscillations, which have a bending
oscillation frequency, which is about equal to an
instantaneous mechanical resonance frequency of the inner
part comprising the four measuring tubes 181, 182, 183, 184 or
which at least lies in the vicinity of such an eigen-, or
42
CA 02754788 2011-09-08
resonance, frequency. The
instantaneous mechanical bending
oscillation resonance frequencies are, in such case, as is
known, dependent in special measure on size, shape and
material of the measuring tubes 181, 182, 183, 184, as well as
also on an instantaneous density of the medium flowing
through the measuring tubes, and can, thus, during operation
of the measuring transducer, be variable within a wanted
frequency band having an expanse of several kilohertz. In
the exciting of the measuring tubes to a bending oscillation
resonance frequency, on the one hand, an average density of
the medium instantaneously flowing through the four measuring
tubes can be easily ascertained on the basis of the
instantaneously excited oscillation frequency. On the other
hand, also, in such manner, the electrical power
instantaneously required for maintaining the oscillations
excited in the wanted mode can be minimized. Especially, the
four measuring tubes 181, 182, 183, 184, driven by the exciter
mechanism, additionally, are, at least at times, caused to
oscillate with essentially equal oscillation frequency,
especially at a shared natural mechanical eigenfrequency of
the inner part. Moreover, it is provided that the measuring
tubes 181, 182, 183, 184, caused to oscillate at essentially
equal frequency, are so excited, that, at least in the case
of no flowing medium, the first and third measuring tubes 181,
183 oscillate essentially synchronously relative to one
another, i.e. with essentially equal oscillation form,
essentially equal phase position and about equal oscillation
amplitude. In manner analogous thereto, in the case of this
embodiment of the invention, also the second and fourth
measuring tubes 182, 184 are caused to oscillate essentially
synchronously relative to one another.
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CA 02754788 2011-09-08
The exciter mechanism according to an embodiment of the
invention, is embodied in such a manner that, therewith, the
first measuring tube 181 and the second measuring tube 182 are
excitable, during operation, to opposite phase, bending
oscillations in the shared first plane of oscillation XZ1 and
the third measuring tube 183 and the fourth measuring tube
184, during operation, to opposite phase bending oscillations
in the shared second plane of oscillation XZ2, especially a
shared second plane of oscillation XZ2 essentially parallel to
the first plane of oscillation XZ1. In
an additional
embodiment of the invention, the exciter mechanism 5 is
formed therefor by means of a first oscillation exciter 51,
especially an electrodynamic, first oscillation exciter 51
and/or a first oscillation exciter 51 differentially exciting
oscillations of the first measuring tube 181 relative to the
second measuring tube 182.
Additionally, it is provided, that the first oscillation
exciter 51 is an oscillation exciter of electrodynamic type
acting simultaneously, especially differentially, on at least
two of the measuring tubes 181, 182, 183, 184.
Accordingly,
the first oscillation exciter 51 is formed additionally by
means of a permanent magnet held on the first measuring tube
and a cylindrical coil permeated by the magnetic field of the
permanent magnet and held on the second measuring tube,
especially in such a manner of a coil, plunging arrangement,
in the case of which the cylindrical coil is arranged
coaxially to the permanent magnet and the permanent magnet is
embodied in the form of an armature moved plungingly within
the coil. In a
further development of the invention, the
exciter mechanism comprises additionally a second oscillation
exciter 52, especially an electrodynamic, second oscillation
exciter 52 and/or a second oscillation exciter 52 constructed
44
CA 02754788 2011-09-08
equally to the first oscillation exciter 51 and/or
differentially exciting oscillations of the third measuring
tube 183 relative to the fourth measuring tube 184. The
two
oscillation exciters can, in advantageous manner, be
interconnected electrically in series, especially in such a
manner, that a combined driver signal excites oscillations of
the first and third measuring tubes 181, 183 together relative
to the second and fourth measuring tubes 182, 184. In
an
additional embodiment, the second oscillation exciter 52 is
formed by means of a permanent magnet held on the third
measuring tube and a cylindrical coil permeated by the
magnetic field of the permanent magnet and held on the fourth
measuring tube.
As shown in Fig. 4, the first oscillation exciter 51 is
arranged in above the first and second measuring tubes 181,
182 and, thus, also above a combined local center of gravity
of all four measuring tubes 181, 182, 183, 184, which lies in
an imaginary cross sectional plane passing through the
installed position of said oscillation exciter, whose inner
part is formed by means of the four measuring tubes. As a
result of the arrangement of at least one oscillation exciter
of the exciter mechanism 5 outside of the above described
combined center of gravity of the four measuring tubes,
supplementally to bending oscillations, in advantageous
manner, also wanted torsional oscillations can be excited,
simultaneously or intermittently. In
this way, in medium
instantaneously located in the measuring tubes 181, 182, 183,
and 184, respectively, in considerable measure, also
frictional, or shear, forces, principally dependent on
viscosity, can be induced, which, in turn, react dampingly
and, thus, measurably, on the oscillations of the measuring
tubes 181, 182, 183, and 184, respectively. Based thereon, for
CA 02754788 2011-09-08
example, on the basis of the driver signal fed into the
exciter mechanism 5, especially its electrical current level,
in case required, also a viscosity of the medium guided in
the measuring transducer can be ascertained.
It is noted here, additionally, that, although the
oscillation exciter of the exciter mechanism illustrated in
the example of an embodiment acts, in each case, about
centrally on the measuring tubes, alternatively or in
supplementation also oscillation exciters acting on the inlet
and on the outlet sides on the respective measuring tubes can
be used, for instance in the manner of the exciter mechanisms
proposed in US-A 4,823,614, US-A 4,831,885, or US-A
2003/0070495.
As evident from Fig. 2 and 4 and usual in the case of
measuring transducers of the type being discussed,
additionally provided in the measuring transducer 11 is a
sensor arrangement 19, for example, an electrodynamic sensor
arrangement, reacting to vibrations of the measuring tubes
181, 182, 183, or 184, especially inlet, and outlet-side
vibrations, especially bending oscillations excited by means
of the exciter mechanism 5, for producing oscillation
measurement signals representing vibrations, especially
bending oscillations, of the measuring tubes and influenced,
for example, as regards a frequency, a signal amplitude
and/or a phase position - relative to one another and/or
relative to the driver signal - by the measured variable to
be registered, such as, for instance, the mass flow rate
and/or the density and a viscosity of the medium,
respectively.
46
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In an additional embodiment of the invention, the sensor
arrangement is formed by means of an inlet-side, first
oscillation sensor 191, especially an electrodynamic, first
oscillation sensor and/or a first oscillation sensor
differentially registering at least oscillations of the first
measuring tube 181 relative to the second measuring tube 182,
as well as an outlet-side, second oscillation sensor 192,
especially an electrodynamic, second oscillation sensor
and/or a second oscillation sensor differentially registering
at least oscillations of the first measuring tube 181 relative
to the second measuring tube 182, which two oscillation
sensors deliver, respectively, a first, and a second,
oscillation measurement signal reacting to movements of the
measuring tubes 181, 182, 183, 184, especially their lateral
deflections and/or deformations. This, especially, in such a
manner, that at least two of the oscillation measurement
signals delivered by the sensor arrangement 19 have a phase
shift relative to one another, which corresponds to, or
depends on, the instantaneous mass flow rate of the medium
flowing through the measuring tubes, as well as, in each
case, a signal frequency, which depends on an instantaneous
density of the medium flowing in the measuring tubes. The
two oscillation sensors 191, 192, for example, oscillation
sensors constructed equally to one another, can, for such
purpose - such as quite usual in the case of measuring
transducers of the type being discussed - be placed
essentially equidistantly from the first oscillation exciter
51 in the measuring transducer 11. Moreover, the oscillation
sensors of the sensor arrangement 19 can, at least, insofar
as they are of equal construction to that of the at least one
oscillation exciter of the exciter mechanism 5, work
analogously to its principle of action, for example, thus be
likewise of electrodynamic type. In a further development of
47
CA 02754788 2011-09-08
the invention, the sensor arrangement 19 is additionally
formed also by means of an inlet-side, third oscillation
sensor 193, especially an electrodynamic, oscillation sensor
and/or an oscillation sensor differentially registering
oscillations of the third measuring tube 183 relative to the
fourth measuring tube 184, as well as an outlet-side, fourth
oscillation sensor 194, especially an electrodynamic, fourth
oscillation sensor 194 and/or an electrodynamic oscillation
sensor differentially registering oscillations of the third
measuring tube 183 relative to the fourth measuring tube 184.
For additional improving of the signal quality, as well as
also for simplifying the measuring device electronics 12
receiving the measurement signals, furthermore, the first and
third oscillation sensors 191, 193 can be electrically in
series interconnected, for example, in such a manner, that a
combined oscillation measurement signal represents combined
inlet-side oscillations of the first and third measuring
tubes 181, 183 relative to the second and fourth measuring
tubes 182, 184. Alternatively or in supplementation, also the
second and fourth oscillation sensors 192, 194 can be
electrically in series interconnected in such a manner, that
a combined oscillation measurement signal of both oscillation
sensors 192, 194 represents combined outlet-side oscillations
of the first and third measuring tubes 181, 183 relative to
the second and fourth measuring tubes 182, 184.
For the aforementioned case, that the oscillation sensors of
the sensor arrangement 19, especially oscillation sensors
constructed equally to one another, should register
oscillations of the measuring tubes differentially and
electrodynamically, the first oscillation sensor 191 is formed
by means of a permanent magnet held to the first measuring
tube - here in the region of oscillations to be registered on
48
CA 02754788 2011-09-08
the inlet side - and a cylindrical coil permeated by the
magnetic field of the permanent magnet and held to the second
measuring tube - here correspondingly likewise in the region
of oscillations to be registered on the inlet side -, and the
second oscillation sensor 192 is formed by means of a
permanent magnet held - in the region of oscillations to be
registered on the outlet side - to the first measuring tube
and a cylindrical coil permeated by the magnetic field of the
permanent magnet and held to the second measuring tube - here
correspondingly likewise in the region of oscillations to be
registered on the outlet side.
Equally, additionally also
the, in given cases, provided, third oscillation sensor 193
can correspondingly be formed by means of a permanent magnet
held to the third measuring tube and a cylindrical coil
permeated by the magnetic field of the permanent magnet and
held to the fourth measuring tube, and the, in given cases,
provided, fourth oscillation sensor 194 by means of a
permanent magnet held to the third measuring tube and a
cylindrical coil permeated by the magnetic field of the
permanent magnet and held to the fourth measuring tube.
It is to be noted here additionally that, although, in the
case of the oscillation sensors of the sensor arrangement 19
illustrated in the example of an embodiment, the oscillation
sensor is, in each case, of electrodynamic type, thus, in
each case, formed by means of a cylindrical magnet coil
affixed to one of the measuring tubes and a therein plunging
permanent magnet correspondingly affixed to an oppositely
lying measuring tube, additionally also other oscillation
sensors known to those skilled in the art, such as e.g.
optoelectronic sensors, can be used for forming the sensor
arrangement. Furthermore, such as quite usual in the case of
measuring transducers of the type being discussed,
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CA 02754788 2011-09-08
supplementally to the oscillation sensors, other, especially
auxiliary sensors, or sensors registering disturbance
variables, can be provided in the measuring transducer, such
as e.g. acceleration sensors, pressure sensors and/or
temperature sensors, by means of which, for example, the
ability of the measuring transducer to function and/or
changes of the sensitivity of the measuring transducer to the
measured variables primarily to be registered, especially the
mass flow rate and/or the density, as a result of cross
sensitivities, or external disturbances, can be monitored
and, in given cases, correspondingly compensated.
For assuring an as high as possible sensitivity of the
measuring transducer to the mass flow, according to an
additional embodiment of the invention, the oscillation
sensors are so arranged on the measuring tubes in the
measuring transducer, that a measuring length, L19, of the
measuring transducer corresponding to a minimum separation
between the first oscillation sensor 191 and the second
oscillation sensor 192, amounts to more than 500 mm,
especially more than 600 mm.
The exciter mechanism 5 and the sensor arrangement 19 are
additionally, such as usual in the case of such measuring
transducers, coupled in suitable manner (for example,
hardwired by means of corresponding cable connections) with a
measuring, and operating, circuit correspondingly provided in
the measuring device electronics. The
measuring, and
operating, circuit, in turn, produces, on the one hand, an
exciter signal correspondingly driving the exciter mechanism
5, for example, an exciter signal controlled as regards an
exciter current and/or an exciter voltage. On
the other
hand, the measuring, and operating, circuit receives the
CA 02754788 2011-09-08
oscillation measurement signals of the sensor arrangement 19
and generates, therefrom, sought measured values, which, for
example, can represent a mass flow rate, a totaled mass flow,
a density and/or a viscosity of the medium being measured and
which, in given cases, can be displayed on-site and/or also
sent to a data processing system superordinated to the in-
line measuring device, in the form of digital, measured data
and there correspondingly further processed. The
above
mentioned application of differentially acting, oscillation
exciters, or oscillation sensors, in the case of the here
illustrated inner part, introduces, among other things, also
the advantage, that for operating the measuring transducer of
the invention, also such established measuring, and
operating, electronics can be used, such as have found broad
application, for example, already in conventional Coriolis,
mass flow and/or density measuring devices.
The measuring device electronics 12, including the measuring,
and operating, circuit, can, furthermore, be accommodated,
for example, in a separate electronics housing 72, which is
arranged removed from the measuring transducer or, such as
shown in Fig. 1, is affixed directly on the measuring
transducer 1, for example, externally on the transducer
housing 71, in order to form a single compact device. In the
case of the here illustrated example of an embodiment,
consequently, placed on the transducer housing 71 is,
additionally, a neck-like, transition piece serving for
holding the electronics housing 72.
Within the transition
piece can additionally be arranged a feedthrough for the
electrical connecting lines between measuring transducer 11,
especially the therein placed oscillation exciters and
sensors, and the mentioned measuring device electronics 12.
The feedthrough is manufactured to be hermetically sealed
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CA 02754788 2011-09-08
and/or pressure resistant, for example, by means of glass,
and/or plastic potting compound.
As already multiply mentioned, the in-line measuring device
and, thus, also the measuring transducer 11, is provided,
especially, for measurements also of high mass flows of more
than 2200 t/h in a pipeline of large caliber of more than 250
mm.
Taking this into consideration, according to an
additional embodiment of the invention, the nominal diameter
of the measuring transducer 11, which, as already mentioned,
corresponds to a caliber of the pipeline, in whose course the
measuring transducer 11 is to be used, is so selected, that
it amounts to more than 100mm, especially, however, is
greater than 300mm.
Additionally, according to a further
embodiment of the measuring transducer, it is provided, that
each of the measuring tubes 181, 182, 183, 184 has, in each
case, a caliber Dn corresponding to a particular tube inner
diameter, which amounts to more than 60 mm. Especially, the
measuring tubes 181, 182, 183, 184 are additionally so
embodied, that each has a caliber Dn of more than 80 mm.
Alternatively thereto or in supplementation thereof, the
measuring tubes 181, 182, 183, 184 are, according to another
embodiment of the invention, additionally so dimensioned,
that they have, in each case, a measuring tube length Ln of
at least 1000 mm. The measuring tube length Ln corresponds,
in the here illustrated example of an embodiment with equal
length measuring tubes 181, 182, 183, 184, in each case, to a
minimum separation between the first flow opening 201A of the
first flow divider 201 and the first flow opening 202A of the
second flow divider 202.
Especially, the measuring tubes
181, 182, 183, 184 are, in such case, so designed, that their
measuring tube length Ln is, in each case, greater than 1200
mm.
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Accordingly, there results, at least for the mentioned case,
that the measuring tubes 181, 182, 183, 184 are composed of
steel, in the case of the usually used wall thicknesses of
over 1 mm, a mass of, in each case, at least 20 kg,
especially more than 30 kg. One tries, however, to keep the
empty mass of each of the measuring tubes 181, 182, 183, 184
smaller than 50 kg.
In consideration of the fact that, as already mentioned, each
of the measuring tubes 181, 182, 183, 184, in the case of the
measuring transducer of the invention, weighs well over 20 kg
and, in such case, such as directly evident from the above
dimensional specifications, can have a capacity of easily 10
1 or more, the inner part comprising then the four measuring
tubes 181, 182, 183, 184 can, at least in the case of medium
with high density flowing through, reach a total mass of far
over 80 kg.
Especially in the case of the application of
measuring tubes with comparatively large caliber D18, large
wall thickness and large measuring tube length Ln, the mass
of the inner part formed by the measuring tubes 181, 182, 183,
184 can directly, however, also be greater than 100 kg or, at
least with medium flowing through, e.g. oil or water, be more
than 120 kg. As a result of this, an empty mass Mil of the
measuring transducer amounts, in total, also to far more than
200 kg, and, in the case of nominal diameters Dil of
significantly greater than 250 mm, even more than 300 kg. As
a result, the measuring transducer of the invention can have
a mass ratio M11/M18 of an empty mass Mil of the total
measuring transducer to an empty mass Mn of the first
measuring tube of easily greater than 10, especially greater
than 15.
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CA 02754788 2011-09-08
= In order, in the case of the mentioned high empty mass Mil of
the measuring transducer, to employ the therefor, in total,
applied material as optimally as possible and, thus, to
utilize the - most often also very expensive - material, in
total, as efficiently as possible, according to an additional
embodiment, the nominal diameter Du of the measuring
transducer is so dimensioned relative to its empty mass N11,
that a mass to nominal diameter ratio Mil/ Dil of the measuring
transducer 11, as defined by a ratio of the empty mass Mil of
the measuring transducer 11 to the nominal diameter Dil of the
measuring transducer 11, is smaller than 2 kg/mm, especially
as much as possible, however, smaller than 1 kg/mm. In order
to assure a sufficiently high stability of the measuring
transducer 11, the mass to nominal diameter ratio MH/ Dil of
the measuring transducer 11 is, at least in the case use of
the above mentioned conventional materials, however, to be
chosen as much as possible greater than 0.5 kg/mm.
Additionally, according to an additional embodiment of the
invention, for additional improvement of the efficiency of
the installed material, the mentioned mass ratio M11/M18 is
kept smaller than 25.
For creation of a nevertheless as compact as possible
measuring transducer of sufficiently high oscillation quality
factor and as little pressure drop as possible, according to
an additional embodiment of the invention, the measuring
tubes are so dimensioned relative to the above mentioned,
installed length LH of the measuring transducer 11, that a
caliber to installed length ratio D18/ LH of the measuring
transducer, as defined by a ratio of the caliber D18 at least
of the first measuring tube to the installed length L11 of the
measuring transducer 11, amounts to more than 0.02,
especially more than 0.05 and/or less than 0.09.
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CA 02754788 2011-09-08
Alternatively or in supplementation, the measuring tubes 181,
182, 183, 184 are so dimensioned relative to the above
mentioned installed length Lil of the measuring transducer,
that a measuring tube length to installed length ratio 1,18/ LI'
of the measuring transducer, as defined by a ratio of the
measuring tube length L18 at least of the first measuring tube
to the installed length L11 of the measuring transducer,
amounts to more than 0.7, especially more than 0.8 and/or
less than 0.95.
In case required, possibly or at least potentially,
mechanical stresses and/or vibrations caused by the
vibrating, especially in the mentioned manner, relatively
large dimensioned, measuring tubes at the inlet side or at
the outlet side in the transducer housing can e.g. be
minimized by connecting the four measuring tubes 181, 182,
183, 184 with one another mechanically at least pairwise on
the inlet side, and at least pairwise on the outlet side, in
each case, by means of coupling elements serving as so-called
node plates - in the following referred to as coupling
elements of first type. Moreover, by means of such coupling
elements of first type, be it through their dimensioning
and/or their positioning on the measuring tubes, mechanical
eigenfrequencies of the measuring tubes and, thus, also
mechanical eigenfrequencies of the inner part formed by means
of the four measuring tubes as well as thereon placed,
additional components of the measuring transducer and, thus,
also its oscillatory behavior, in total, can, with targeting,
be influenced.
The coupling elements of first type serving as node plates
can, for example, be thin plates, or washers, manufactured
especially from the same material as the measuring tubes,
CA 02754788 2011-09-08
= which, in each case, corresponding with the number and the
outer dimensions of the measuring tubes to be coupled with
one another, are provided with bores, in given cases,
supplementally, slitted to the edge, so that the washers can
first be mounted onto the respective measuring tubes 181, 182,
183, or 184 and, in given cases, thereafter still be bonded to
the respective measuring tubes, for example, by hard
soldering or welding.
Accordingly, the measuring transducer comprises, according to
an additional embodiment of the invention, a first coupling
element 241 of first type, which is affixed on the inlet side
at least to the first measuring tube and to the second
measuring tube and spaced both from the first flow divider as
well as also from the second flow divider for forming inlet-
side, oscillation nodes at least for vibrations, especially
bending oscillations, of the first measuring tube and for
thereto opposite phase vibrations, especially bending
oscillations, of the second measuring tube, as well as a
second coupling element 242 of first type, especially a second
coupling element 242 constructed equally to the first coupling
element, which is affixed on the outlet side at least to the
first measuring tube 181 and to the second measuring tube 182
and spaced both from the first flow divider 201 as well as
also from the second flow divider 202, as well as also from
the first coupling element 241, for forming outlet-side,
oscillation nodes at least for vibrations, especially bending
oscillations, of the first measuring tube 181 and for thereto
opposite phase vibrations, especially bending oscillations,
of the second measuring tube 182. As directly evident from
Fig. 4, or Figs. 5a, 5b, the first coupling element 241 of
first type is affixed on the inlet side also to the third
measuring tube 183 and to the fourth measuring tube 184 and
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CA 02754788 2011-09-08
= spaced both from the first flow divider 201 as well as also
from the second flow divider 202, for forming inlet-side,
oscillation nodes also for vibrations, especially bending
oscillations, of the third measuring tube 183 and for thereto
opposite phase vibrations, especially bending oscillations,
of the fourth measuring tube 184, and the second coupling
element 242 of first type is affixed on the outlet side also
to the third measuring tube 183 and to the fourth measuring
tube 184 and spaced both from the first flow divider 201 as
well as also from the second flow divider 202, as well as also
from the first coupling element 241, for forming outlet-side,
oscillation nodes at least for vibrations, especially bending
oscillations, of the third measuring tube 183 and for thereto
opposite phase vibrations, especially bending oscillations,
of the fourth measuring tube 184, so that, as a result, all
four measuring tubes 181, 182, 183, 184 are mechanically
connected with one another by means of the first coupling
element 241 of first type as well as by means of the second
coupling element 242 of first type.
Each of the two
aforementioned coupling elements 241, 242 of first type,
especially coupling elements constructed equally to one
another, is, according to an additional embodiment of the
invention, plate shaped, especially in such a manner, that it
has, as well as also directly evident from the combination of
figures, a rather rectangular or also square, basic shape or,
however, that it has, rather, a round, an oval, a cross
shaped or, such as, for example, also provided in US-A
2006/0283264, a rather H-shaped basic shape.
Additionally,
the two coupling elements 241, 242 are oriented essentially
parallel relative to one another.
As directly evident from Fig. 4, or Figs. 5a, 5b, the two
aforementioned coupling elements 241, 242 are additionally so
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CA 02754788 2011-09-08
embodied and so placed in the measuring transducer, that a
center of mass of the first coupling element 241 of first type
has a distance to a center of mass of the measuring
transducer 11, which is essentially equal to a distance of a
center of mass of the second coupling element 242 of first
type to said center of mass of the measuring transducer 11,
especially in such a manner, that the two coupling elements
241, 242 are, as a result, arranged symmetrically to a shared
imaginary cross sectional plane, in each case, cutting
centrally through the measuring tubes 181, 182, 183, 184.
For additionally increasing the degrees of freedom in the
case of optimizing the oscillatory behavior of the inner part
formed by means of the four measuring tubes 181, 18
--2, 183, 184,
the measuring transducer 11 comprises, according to a further
development of the invention, additionally a third coupling
element 243 of first type, which is affixed on the inlet side
at least to the third measuring tube 183 and to the fourth
measuring tube 184 and spaced both from the first flow divider
201 as well as also from the second flow divider 202 for
forming inlet-side, oscillation nodes at least for
vibrations, especially bending oscillations, of the third
measuring tube 183 and for thereto opposite phase vibrations,
especially bending oscillations, of the fourth measuring tube
184. Moreover, the measuring transducer 11 comprises, in the
case of this further development, a fourth coupling element
244 of first type, especially a fourth coupling element
constructed equally to the third coupling element 243 of first
type, which fourth coupling element is affixed on the outlet
side at least to the third measuring tube 183 and to the
fourth measuring tube 184 and spaced both from the first flow
divider 201 as well as also from the second flow divider 202,
as well as also from the third coupling element 243 of first
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CA 02754788 2011-09-08
type, for forming outlet-side, oscillation nodes at least for
vibrations, especially bending oscillations, of the third
measuring tube 183 and for thereto opposite phase vibrations,
especially bending oscillations, of the fourth measuring tube
184.
Each of the two aforementioned third and fourth coupling
elements 243, 244 of first type, especially third and fourth
coupling elements constructed equally to one another, is
embodied, according to an additional embodiment of the
invention, again, plate shaped, especially in such a manner,
that it has a rectangular, square, round, cross shaped or H-
shaped, basic shape. Additionally, the two aforementioned
third and fourth coupling elements 243, 244 are oriented
extending essentially parallel relative to one another.
As shown in Fig. 4, or in Figs. 5a, 5b, the third coupling
element 243 of first type is affixed on the inlet side also to
the first measuring tube 181 and to the second measuring tube
182 and spaced both from the first flow divider 201 as well as
also from the second flow divider 202, as well as also from
the first coupling element of first type 241 and the fourth
coupling element 244 of first type is affixed on the outlet
side also to the first measuring tube and to the second
measuring tube and spaced both from the first flow divider as
well as also from the second flow divider, as well as also
from the second coupling element, so that, as a result, all
four measuring tubes 181, 182, 183, 184 are also mechanically
connected with one another by means of the third coupling
element 243 of first type as well as by means of the fourth
coupling element 244 of first type.
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CA 02754788 2011-09-08
. As directly evident from the combination of Figs. 4, 5a, 5b,
also the third and fourth coupling elements 243, 244 are
additionally so embodied and so placed in the measuring
transducer, that a center of mass of the third coupling
element 243 of first type has a distance to the center of mass
of the measuring transducer, which essentially is equal to a
distance of a center of mass of the fourth coupling element
244 of first type to said center of mass of the measuring
transducer, especially in such a manner, that the two
coupling elements 243, 244 are, as a result, arranged
symmetrically to a shared imaginary cross sectional plane, in
each case, cutting centrally through the four measuring tubes
18k, 182, 183, 184= Additionally, according to a further
embodiment of the invention, the four coupling element 241,
242, 243, 244 of first type are so arranged in the measuring
transducer, that the distance of the center of mass of the
third coupling element 243 of first type from the center of
mass of the measuring transducer is greater than the distance
of the center of mass of the first coupling element 241 of
first type from said center of mass of the measuring
transducer and greater than the distance of the center of
mass of the second coupling element 242 of first type from
said center of mass of the measuring transducer.
As directly evident from the combination of Figs. 4, 5a and
5b, a minimum separation between the coupling element of
first type affixed on the inlet side to a particular
measuring tube and lying nearest to the center of mass of the
measuring transducer 11 - here thus the first coupling
element 241 of first type -, and the coupling element of first
type affixed on the outlet side to said measuring tube and
lying nearest to the center of mass of the measuring
transducer - here thus the second coupling element 242 of
CA 02754788 2011-09-08
first type -, defines, in each case, a free, oscillatory
length, 1,18,, of such measuring tube, wherein, according to an
additional embodiment of the invention, the coupling elements
of first type are so placed in the measuring transducer,
that, as a result, the free, oscillatory length of each of
the measuring tubes 181, 182, 183, 184 amounts to less than
2500 mm, especially less than 2000 mm and/or more than 800
mm. Alternatively or in supplementation, it is additionally
provided, that all four measuring tubes 181, 182, 183, 184 have
the same, free, oscillatory length 1,18x.
It can additionally, in the context of a still simpler and
yet more exact adjusting of the oscillatory behavior of the
measuring transducer, be quite of advantage, when the
measuring transducer, such as, for example, provided in US-A
2006/0150750, moreover, has still other coupling elements of
the aforementioned type serving for forming inlet, or outlet,
side, oscillation nodes for vibrations, especially bending
oscillations, of the first measuring tube and for thereto
opposite phase vibrations, especially bending oscillations,
of the second measuring tube, or for vibrations, especially
bending oscillations, of the third measuring tube and for
thereto opposite phase vibrations, especially bending
oscillations, of the fourth measuring tube, for example,
thus, in total, 6 or 8 such coupling elements of first type.
For creation of an as compact as possible measuring
transducer of sufficiently high oscillation quality factor
and high sensitivity in the case of as little pressure drop
as possible, according to an additional embodiment of the
invention, the measuring tubes 181, 182, 183, 184 are so
dimensioned relative to the mentioned free, oscillatory
length that a caliber to oscillatory length ratio D18/L18), of
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CA 02754788 2011-09-08
the measuring transducer, as defined by a ratio of the
caliber D18 of the first measuring tube to the free,
oscillatory length 1,18x of the first measuring tube, amounts
to more than 0.07, especially more than 0.09 and/or less than
0.15.
Alternatively or in supplementation, for this,
according to an additional embodiment of the invention, the
measuring tubes 181, 182, 182, 184 are so dimensioned relative
to the above mentioned installed length Lil of the measuring
transducer that an oscillatory length to installed length
ratio L18x/ Lll of the measuring transducer, as defined by a
ratio of the free, oscillatory length 1,18x of the first
measuring tube to the installed length Lil of the measuring
transducer, amounts to more than 0.55, especially more than
0.6 and/or less than 0.9.
According to an additional embodiment of the invention, the
oscillation sensors, relative to the free, oscillatory
length, are so arranged in the measuring transducer, that a
measuring length to oscillatory length ratio of the measuring
transducer, as defined by a ratio of the mentioned measuring
length of the measuring transducer to the free, oscillatory
length of the first measuring tube, amounts to more than 0.6,
especially more than 0.65 and/or less than 0.95.
For creation of an as compact as possible measuring
transducer, which is, nevertheless, however, as sensitive as
possible to mass flow, according to an additional embodiment
of the invention, the oscillation sensors are so arranged in
the measuring transducer relative to the installed length of
the measuring transducer that a measuring length to installed
length ratio of the measuring transducer, which is defined by
a ratio of the measuring length to the installed length of
the measuring transducer, amounts to more than 0.3,
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CA 02754788 2011-09-08 '
especially more than 0.4 and/or less than 0.7. Alternatively
or in supplementation, the oscillation sensors are, according
to an additional embodiment of the inventionõ so placed in
the measuring transducer relative to the measuring tubes,
that a caliber to measuring length ratio 1318/L19 of the
measuring transducer, which is. defined by a ratio of the
caliber D18 of the first measuring tube to the measuring
length L19 of the measuring transducer, amounts to more than
0.05, especially more than 0.09. In an additional embodiment
of the invention, additionally, the above mentioned measuring
length L19 is kept smaller than 1200 mm.
In an additional embodiment of the invention, it is further
provided that the measuring tubes 181, 182, 183, 184 are
driven, during operation, pairwise synchronously, thus with
equal phase position, so that the oscillations of all four
measuring tubes 181, 182, 183, 184 are only pairwise out of
phase. In advantageous manner, the oscillatory behavior of
the inner part formed by means of the four measuring tubes
181, 182, 183, 184, together with the exciter mechanism, and
the sensor arrangement, as well as also the driver signals
controlling the exciter mechanism, are so matched to one
another, that at least the oscillations of the four measuring
tubes 181, 182, 183, 184 excited in the wanted mode are so
developed, that the first and the second measuring tubes 181,
182 oscillate with essentially opposite phase relative to one
another, thus with an opposing phase shift of about 180 , and
also the third and fourth measuring tubes 183, 184 oscillate
with essentially opposite phase relative to one another,
while, simultaneously, the first and third measuring tubes
181, 183 oscillate with essentially equal phase relative to
one another and the second and fourth measuring tubes 182, 184
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CA 02754788 2011-09-08
oscillate with essentially equal phase relative to one
another.
Therefore, the measuring transducer includes, according to a
further embodiment of the invention, additionally a first
coupling element 251 of second type, especially a plate shaped
or rod shaped, first coupling element 251 of second type,
which is affixed only to the first measuring tube 181 and to
the third measuring tube 183 and spaced both from the first
coupling element 241 of first type as well as also from the
second coupling element 242 of first type, for synchronizing
vibrations, especially bending oscillations, of the first
measuring tube 181 and thereto equal frequency vibrations,
especially bending oscillations, of the third measuring tube
183.
Furthermore, the measuring transducer comprises, at
least in the case of this embodiment of the invention, at
least a second coupling element 252 of second type, especially
a plate shaped or rod shaped, second coupling element 252 of
second type, which is affixed only to the second measuring
tube 182 and to the fourth measuring tube 184 and spaced both
from the first coupling element 241 of first type as well as
also from the second coupling element 241 of first type, as
well as also from the first coupling element 251 of second
type, for synchronizing vibrations, especially bending
oscillations, of the second measuring tube 182 and thereto
equal frequency vibrations, especially bending oscillations,
of the fourth measuring tube 184. As
directly evident from
the combination of Figs. 4, 5a and 5b, the first and second
coupling elements 251, 252 of second type are placed in the
measuring transducer 11 as oppositely lying to one another as
possible.
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CA 02754788 2011-09-08
An advantage of the mechanical coupling of the measuring
tubes in the above described manner is, among other things,
to be seen in the fact that the four measuring tubes 181, 182,
183, 184 are reduced to two measuring tube composites acting,
in each case, effectively as one oscillatory system, each
thus acting essentially as a single measuring tube, since the
exciter forces produced by the exciter mechanism 5 act, due
to the mechanical coupling, both between the first and second
measuring tubes 181, 182 as well as also equally between the
third and fourth measuring tubes 183, 184, and, in turn, also
the reaction forces caused in the through-flowing media for
purposes of the measuring are transmitted, in each case,
together back to the oscillation sensors of the sensor
arrangement 5. Furthermore, possible differences between the
individual measuring tubes 181, 182, 183, 184 can as regards
their nominal oscillatory behavior, e.g. as a result of non-
uniform flow, different temperatures, and/or different
density distributions, etc., be cancelled in very simple
manner. The application of coupling elements of second type
has additionally also the advantage, that each of the two
measuring tube composites formed, thus, in very simple
manner, acts, not only for the exciter mechanism, but equally
also for the sensor arrangement 19, and, thus, also for the
measuring, and operating, circuit of the measuring device
electronics 12, in total, practically, in each case, as a
single measuring tube, and the measuring transducer 11, thus,
from the point of view of the measuring, and operating,
circuit, seems to have only two measuring tubes oscillating
relative to one another. As a result of this, at least for
the preprocessing and possible digitizing of the oscillation
measurement signals, proven signal processing technologies
and also proven, especially two channel (thus processing
oscillation measurement signals delivered from only two
CA 02754788 2011-09-08
oscillation sensors) measuring circuits from the field of
Coriolis, mass flow, or density measurement, can be utilized.
Equally, thus, also for the operating circuit driving the
exciter mechanism, driver circuits known to those skilled in
the art, especially such operating on one channel, thus
delivering exactly one driver signal for the exciter
mechanism, can be directly used. In case required, however,
also the oscillation measurement signals delivered, in each
case, from the two or more oscillation sensors can, however,
also be individually preprocessed and correspondingly
digitized in, in each case, separate measuring channels;
equally, in case required, also the, in given cases, present,
two or more oscillation exciters can be operated separately
by means of separate driver signals.
According to an embodiment of the invention, the measuring
tubes 181, 182, 183, 184, as well as the coupling elements
connecting these with one another, are, consequently,
additionally so formed and so mechanically coupled with one
another by means of coupling elements of second type, in
given cases, supplementally also by means of coupling
elements of first type, that a first measuring tube composite
formed from the first and the third measuring tubes 181, 183
and a second measuring tube composite formed by the second
and the fourth measuring tubes 182, 184 have essentially the
same mechanical eigenfrequencies.
In the example of an embodiment shown here, the first
coupling element 251 of second type is affixed to the first
and third, measuring tubes 181, 183, respectively, in the
region of 50% of a minimum separation between the first
coupling element 241 of first type and the second coupling
element 242 of first type -, as a result, thus at about half
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CA 02754788 2011-09-08
= the free, oscillatory length of the first and third measuring
tubes 181, 183, respectively.
Additionally, also the second
coupling element of second type is in corresponding manner
affixed to the second and fourth measuring tubes 182, 184,
respectively, in the region of 50% of a minimum separation
between the first coupling element 241 of first type and the
second coupling element 242 of first type, thus at about half
the free, oscillatory length of the second and fourth
measuring tubes 182, 184, respectively.
In advantageous manner, the coupling elements of second type
can supplementally also serve as holders of components of the
exciter mechanism 5.
Therefore, according to an additional
embodiment of the invention, it is provided, that each of the
oscillation exciters 51, 52, especially equally constructed
oscillation exciters, is held, partially, in each case, on
two coupling elements of second type - here, the first and
second coupling elements 251, 252 - lying opposite to one
another.
Thus, it can, in very effective and, equally as
well, very simple manner, be assured, that the exciter force
generated by means of the oscillation exciter 51 effects at
least predominantly synchronous, especially also of
essentially equal phase to one another, bending oscillations
of the first and third measuring tubes 181, 183, or the second
and fourth measuring tubes 182, 184. For example, in the case
of electrodynamic oscillation exciters, the cylindrical coil
can be affixed to the first coupling element of second type
and the, in each case, associated permanent magnet to the
oppositely lying, second coupling element of second type.
For the mentioned case, in which the exciter mechanism 5 has
two oscillation exciters 51, 52 both the first oscillation
exciter 51 as well as also the second oscillation exciter 52
can, in each case, be held on the first and second coupling
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CA 02754788 2011-09-08
. elements 251, 252 of second type, for example, also in such a
manner, that, as directly evident from Fig. 4, or Fig. 5a,
there is a minimum separation between the first and second
oscillation exciters 51, 52 of more than twice as large as a
tube outer diameter of the measuring tubes 181, 182, 183, 184,
at least, however, of the first measuring tube 181.
In this
way, in total, an optimal exploitation of the available room
in the inner space of the transducer housing 71 is enabled, as
well as also a simple mounting of the oscillation exciters 51,
52.
According to an additional embodiment of the invention, the
measuring transducer comprises, additionally, a third
coupling element 253 of second type, for example, again, a
plate shaped or rod shaped, coupling element of second type,
which is affixed only to the first measuring tube 181 and to
the third measuring tube 183 and spaced both from the first
coupling element 241 of first type as well as also from the
second coupling element 242 of first type, as well as also
from the first coupling element 251 of second type, for
synchronizing vibrations, especially bending oscillations, of
the first measuring tube 181 and thereto equal frequency
vibrations, especially bending oscillations, of the third
measuring tube 183, as well as a fourth coupling element 254
of second type, especially a plate shaped or rod shaped,
coupling element of second type, which is affixed only to the
second measuring tube 182 and to the fourth measuring tube 184
and spaced both from the first and second coupling elements
of first type as well as also from the second and third
coupling elements of second type, in each case, for
synchronizing vibrations, especially bending oscillations, of
the second measuring tube 182 and thereto equal frequency
vibrations, especially bending oscillations, of the fourth
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CA 02754788 2011-09-08
= measuring tube 184. The third and fourth coupling elements
253, 254 of second type are, such as directly evident from the
combination of Figs. 4, 5a and 5b, preferably placed in the
measuring transducer 11 lying opposite to one another.
Additionally, the measuring transducer 11 comprises,
according to an additional embodiment of the invention, a
fifth coupling element 255 of second type, especially a plate
shaped or rod shaped fifth coupling element 255 of second
type, which is affixed only to the first measuring tube 181
and to the third measuring tube 183 and spaced both from the
first and second coupling elements of first type as well as
also from the first and third coupling elements of second
type, for synchronizing vibrations, especially bending
oscillations, of the first measuring tube 181 and of thereto
equal frequency vibrations, especially bending oscillations,
of the third measuring tube 183, as well as a sixth coupling
element 256 of second type, especially a plate shaped or rod
shaped, sixth coupling element 256 of second type, which is
affixed only to the second measuring tube 182 and to the
fourth measuring tube 184 and spaced, in each case, both from
the first and second coupling elements of first type as well
as also from the second, fourth and fifth coupling elements
of second type, for synchronizing vibrations, especially
bending oscillations, of the second measuring tube and of
thereto equal frequency vibrations, especially bending
oscillations, of the fourth measuring tube.
The fifth and
sixth coupling elements 255, 256 of second type are,
preferably, again, placed lying opposite to one another in
the measuring transducer 11.
@Furthermore, it can be of advantage to use the
aforementioned coupling elements of second type additionally
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CA 02754788 2011-09-08
also for holding individual components of the sensor
arrangement. In
accordance therewith, it is provided,
according to an additional embodiment of the invention, that
the inlet-side, first oscillation sensor 191 is held,
partially, in each case, on the third and fourth coupling
elements 253, 254 of second type.
Additionally, the second
oscillation sensor 192 is, in corresponding manner, held on
the fifth and sixth coupling elements 255, 256 of second type.
Thus, it can, in very effective, equally as well very simple
manner, be assured, that the oscillation measurement signal
generated, during operation, by means of the first
oscillation sensor 191 represents. at least predominantly,
synchronous, inlet-side, bending oscillations (especially
also bending oscillations of equal phase to one another) of
the first and third measuring tubes 181, 183 relative to the
equally synchronized, inlet-side, bending oscillations
(especially also bending oscillations of phase equal to one
another) of the second and fourth measuring tubes 182, 184, or
that the oscillation measurement signal generated, during
operation, by means of the second oscillation sensor 192
represents, at least predominantly, synchronous, outlet-side,
bending oscillations (especially also bending oscillations of
phase equal to one another) of the first and third measuring
tubes 181, 183 relative to the equally synchronized, outlet-
side, bending oscillations (especially also bending
oscillations of phase equal to one another) of the second and
fourth measuring tubes 182, 184. For example, in the case of
electrodynamic oscillation sensors, the cylindrical coil of
the first oscillation sensor 191 can be affixed to the third
coupling element of second type and the associated permanent
magnet to the oppositely lying, fourth coupling element of
second type, or the cylindrical coil of the second
oscillation sensor 192 can be affixed to the fifth, and the
CA 02754788 2011-09-08
associated permanent magnet to the oppositely lying, sixth
coupling element of second type. For the mentioned case, in
which the sensor arrangement 19 is formed by means of four
oscillation sensors 191, 192, 193, 194, according to an
additional embodiment of the invention, both the first
oscillation sensor 191 as well as also the third oscillation
sensor 193 are, in each case, partially held on the third and
fourth coupling elements of second type, especially in such a
manner, that, such as directly evident from the combination
of Figs. 4, 5a and 5b, a minimum separation between the first
and third oscillation sensors 191, 193 is more than twice as
large as .a tube outer diameter of the first measuring tube
181. In
corresponding manner, additionally, also the second
oscillation sensor 192 and the fourth oscillation sensor 194
can, in each case, be held on the fifth and sixth coupling
elements of second type, especially in such a manner, that,
as directly evident from the combination of Figs. 4, Sa and
5b, a minimum separation between the second and fourth
oscillation sensors 192, 194 is more than twice as large as a
tube outer diameter of the first measuring tube 181, whereby,
in total, an optimal exploitation of the room available in
the inner space of the transducer housing 71, as well as also
a simple mounting of the oscillation sensors of the sensor
arrangement 19, is enabled.
Therefore, according to an
additional embodiment of the invention, each of the
oscillation sensors, especially equally
constructed
oscillation sensors, of the sensor arrangement 19 is held on
two coupling elements of second type lying opposite to one
another.
For additional improvement of the oscillation quality factor
of the inner part in the case of an as short installed length
Lll of the measuring transducer 11 as possible, or an as short
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CA 02754788 2011-09-08
free, oscillatory length L18õ of the measuring tubes 181, 182,
183, or 184 as possible, the measuring transducer comprises,
according to an additional embodiment of the invention, a
plurality of annular stiffening
elements
221A,...222A,...223A,...224A,=.., especially annular stiffening
elements constructed equally to one another. Each
of these
stiffening elements is so placed on exactly one of the
measuring tubes 181, 182, 183, 184, that it grips around its
tube along an imaginary peripheral line thereof, especially a
circularly orbiting, peripheral line; compare, in this
connection, also the initially mentioned US-B 6,920,798.
Especially, in such case, it is, additionally provided, that
at least four of said stiffening elements 221A, 221B, 221c,
221D, or 222A, 222B, 222c, 222D, or 223A, 223B, 223c, 223D, or 224A,
2243, 224c, 224D, especially equally constructed stiffening
elements, are placed on each of the measuring tubes 181, 1821
183, and 184, respectively. The
stiffening elements
222A, = = = 223A,...224A,... are, in advantageous manner, so
placed in the measuring transducer 11, that two adjoining
stiffening elements mounted on the same measuring tube have,
relative to one another a separation, which amounts to at
least 70% of a tube outer diameter of said measuring tube, at
most, however, 150% of such tube outer diameter.
Found as
especially suitable has been, in such case, a separation of
neighboring stiffening elements relative to one another,
which lies in the range of 80% to 120% of the tube outer
diameter of the respective measuring tube 181, 182, 183, and
184, respectively.
@Through the application of four instead of, such as to this
point, two measuring tubes flowed-through in parallel, it is
then also possible to manufacture, cost effectively,
measuring transducers of the described type also for large
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CA 02754788 2011-09-08
mass flow rates, or with large nominal diameters of far over
250 mm, on the one hand, with an accuracy of measurement of
over 99.8% at an acceptable pressure drop, especially of
about lbar or less, and, on the other hand, to keep the
installed mass, as well as also the empty mass, of such
measuring transducers sufficiently in limits, that, in spite
of large nominal diameter, manufacture, transport,
installation, as well as also operation can always still
occur economically sensibly.
Especially also through
implementing of above explained measures for further
developing the invention - individually or also in
combination -, measuring transducers of the type being
discussed can also, in the case of large nominal diameter, be
so embodied and so dimensioned, that a mass ratio of the
measuring transducer, as defined by a ratio of the mentioned
empty mass of the measuring transducer to a total mass of the
inner part formed by means of the four measuring tubes and
the thereto held exciter mechanism, and sensor arrangement,
as well as, in given cases, components of the measuring
transducer affixed additionally to the measuring tubes and
influencing their oscillatory behavior, can be kept directly
smaller than 3, especially smaller than 2.5.
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