O
`
`United States Patent [191
`Thompson
`‘
`
`.
`
`[11] Patent Number:
`[45] Date of Patent:
`
`5,050,439
`Sep. 24, 1991
`
`[54] CORIOLIS-TYPE MASS FLOWMETER
`CIRCUITRY
`
`_
`[75] Inventor: Duane T- Thompson, Frankhn, Mass-
`[73] Assignee: The Foxboro Company, Foxboro,
`Mass.
`
`4,777,833 10/1988 Carpenter ...................... .. 73/861.38
`4,782,711 11/1988 Pratt ............................... .. 73/861.38
`4,817,448 4/1989 Hargarten et a1.
`'
`73/86l.38
`4,823,614 4/1989 Dahlin ................. .. 73/86188
`4,831,855 5/ 1989 Dahhn ............................ .. 73/861.38
`FOREIGN PATENT DOCUMENTS
`
`[21] Appl. No.: 420,569
`.
`[22] Flled‘
`
`Oct- 12’ 1989
`
`[60]
`
`Data
`'
`Relat US. A l‘
`ed
`pp ‘canon
`Division of Ser. No. 116,257, Oct. 29, 1987, Pat. No.
`4,911,020, which is a continuation-in-part of Ser. No.
`923,847, Oct. 28, 1986, Pat. No. 4,891,991.
`[51] Int. Cl.5 .............................................. .. G01F 1/84
`[52] US. Cl, .............. .,
`_ _ ,
`73/361,33
`[58] Field of Search ....................... .. 73/86l.38, 861.37
`[56]
`References Cited
`
`0212782 3/1987 European Pat. Off. .
`WO8505677 12/1985 PCT Int’l Appl. .
`WO8600699 1/1986 PCT 11181 Appl. .
`WO8702469 4/1987 PCT Int’l Appl. .
`.
`Primary Examiner-Herbert Goldstein
`Attorney’ Agent, or Firm_FiSh & Richardson
`'
`
`ABSTRACT
`[57]
`Displacement 591159“ at Opposite ends of at least one
`oscillating conduit produce output signals from which
`the drive component or the Coriolis component, or
`preferably both, are recovered. An osc1llatory dr1ve
`s1gnal is derived from the dr1ve component, and a mass
`?ow signal is derived from the Coriolis component. The
`U'S- PATENT DOCUMENTS
`remaining drive Component in a CQmbination 0f the tW0
`Re. 31,450 11/1983 Smith ............................. .. 73/136138
`sensor outputs is nulled by amplitude control of one
`3,509,767 5/1970 Greer ...................... .f. 73/705
`73/ 194 M sensor output. Two force drivers at opposite ends of the
`3,927,565 12/ 1975 Pavlin 6t 81
`73/361-38
`conduit are driven by complementary drive signals to
`411271023 11/1978 C01‘ 6‘ al
`4‘l87’721 2/1980 Smlth """" "
`73/194 B.
`which a perturbation signal is added. The remaining
`4,192,184 3/1980 Cox et a1.
`73/194 B
`.
`.
`.
`.
`.
`4,252,023 2/1981 smith at al_
`73/861_38
`perturbation s1gnal in a lcombmation of the two sensor
`4,311,054 1/1982 Cox et a1’
`73/861353
`outputs 1s nulled by addmg compensation to both drive
`4,422,338 12/1983 Smith ....... __
`73/861,355
`signals to eliminate drive force imbalance. Synchronous
`4,491,009 1/1985 Ruesch . . . . . . . . . . .
`. . . . .. 73/32 A
`demodulation is used in the preferred embodiment to
`73/ 861-38
`detect several parameters in a combination of the sensor
`4,655,039 4/ 1937 I‘19191261! et a1
`gab?“ et a1‘ ' ' ' ' ' '
`outputs. In a dual loop con?guration, pairs of sensors
`
`' ' " ' ' "
`
`' ' ' ' ' " 73/861'38
`4’7O3’6O0 11/1987 853mg; ' ' ' ' ' '
`‘ls/861.38
`4,747,312 5/1988 Herzl ........ ..
`73/861.38
`4,756,l97 7/1988 Herzl
`4,759,223 7/1988 Frost .............................. .. 73/861.38
`
`and/or force drivers are located at opposite ends of
`each Com-‘111" 569110“
`
`21 Claims, 12 Drawing Sheets
`
`Micro Motion 1027
`
`1
`
`

`

`US. Patent
`
`Sep. 24, 1991”
`
`Sheet 1 of 12
`
`v 5,050,439
`
`
`
`on Timmmd mm>_mo\\.
`
`.r.
`
`2
`
`

`

`US. Patent
`
`Sep. 24, 1991
`
`Sheet 2 of 12
`
`’ 5,050,439 .
`
`
`(SERIES FLOW )
`
`FIG. 2A
`
`FIG. 3
`
`/Ie\
`
`4o
`
`DRIVER/BET.
`08.0 \i
`
`,-
`
`.
`
`. DRIVER/BET.
`J” M
`38
`
`_
`
`,
`
`-"
`
`3
`
`

`

`US. Patent
`
`Sep. 24, 1991_
`
`Sheet‘ 3 of 12
`
`1 5,050,439
`
`FIG.
`
`4
`
`34
`
`36
`
`so‘ A
`
`38
`
`5 2/
`42
`
`48
`
`4__
`
`'
`5'
`
`y.
`'4
`
`____________
`
`62
`
`H6. 6
`
`/ / //\"""ER
`Con-A
`
`MAGNET
`
`POLE
`PIECE
`
`////
`
`FIG. 6A
`
`4
`
`

`

`US. Patent
`
`'Sep. 24, 1991
`
`Sheet 4 of 12
`
`5,050,439
`
`lo"
`
`20
`
`1
`
`OUT
`
`‘70,80
`
`FIG. 7
`
`70, 8O
`
`~54
`
`70,80
`8 / 4
`
`OUT
`——->
`
`CORIOLIS
`MODE
`
`DRWE
`MODE
`
`COMMON
`MODE
`
`He. 9
`
`5
`
`

`

`US. Patent
`
`Sep. 24, 1991 _
`
`Sheet 5 of 12
`
`5,050,439
`
`FIG. 10A
`
`FIG. 108
`
`FIG. 11A
`PERPENDICULAR
`
`|N-LINE
`
`6
`
`

`

`US. Patent
`US. Patent
`
`Sep. 24, 19in
`Sep. 24, 1951
`
`Sheet 6 of 12
`Sheet 6 of 12
`
`5,050,439
`5,050,439
`
`
`
`7
`
`

`

`US. Patent
`
`Sep; 24, 1991
`
`Sheet 7 of 12
`
`5,050,439
`
`2moo;
`
`Oh
`
`mumOum
`
`amaze
`
`A
`
`women.
`
`mmZmo
`
`A
`
`moon.
`
`ON
`
`Oh
`
`memo...
`
`mw>_mo
`+Aa.
`
`FDmkDO
`
`0N.
`
`mwddIOJ
`
`INF...“—
`
`.2.2...
`
`wuzwmmmwm
`
`medmmzmo
`
`mmnkdmodso
`
`mowo...
`
`amaze
`
`A.»
`
`oz_n_2<o.woo_2
`
`.NAFI
`5%an$sz..I
`
`025.240MQOEm>EQ
`
`\Jmid
`
`.mOmd
`
`OOEMOI£3m
`
`om
`
`m.
`
`moo.—
`
`
`
`3%:.8;
`
`
`
`0023memzmm
`
`0023m\E2<mmm
`
`On.
`
`2mm
`
`OJJmkzobm—ZA‘
`>3mz_mNI:On
`
`m0h<4£0m0
`
`0
`
`0m
`
`mum00
`
`8
`
`
`
`
`
`
`
`

`

`US. Patent
`
`Sep. 24, 1991
`
`Sheet 8 of 12
`
`5,050,439 _
`
`}TDA-DrF-D
`FLOWOUTPUT
`FREQUENCY
`
`REFERENCEGENERATOR
`
`'0?!
`
`>.
`
`3%w
`g
`
`2m
`
`”0
`55.1
`cm
`
`9
`
`

`

`US. Patent
`US. Patent
`
`Sep. 24, 1991
`Sep. 24, 1991
`
`Sheet 9 of 12
`Sheef 9 of 12
`
`I 5,050,439
`I 5,050,439
`
`26:
`
`10
`
`10
`
`

`

`US. Patent
`
`_ Sep. 24, 1991
`
`Sheet 10 of 12
`
`5,050,439
`
`
`
`@659» 52 w B
`
`HmEP+OF A
`
`oQdI
`
`
`
`“.2 m U “Tl wonSmQ
`
`
`
`Ow: 20mm
`
`11
`
`

`

`US. Patent
`
`Sep.24,1991
`
`Sheet 11 of 12
`
`5,050,439
`
`baa“58+
`
`1&8
`
`mum?
`
`.95.
`
`.uwfif
`
`mm?
`
`8sz
`
`mesuxfi
`
`we:
`
`_.85
`
`8stE88ch_
`
`E1smmE96:um"...m.a1N6.yor00>
`
`82.2..m.Am.3813.
`
`9&2:2an:
`
`
`
`05..2.“—
`
`ZRVEOmu
`
`00>20E
`
`00>20E
`
`E689
`
`2:.0E
`
`20mm
`
`12
`
`12
`
`
`

`

`US. Patent
`
`_ Sep.24, 1991
`
`Sheet 12 0f 12
`
`1 5,050,439
`
`261 1
`
`
`
`25.2 v68 a:
`
`2.9m
`
`“mg...
`
`was
`
`1 98.6
`
`$30-95
`
`@705
`
`
`
`“GE $53
`
`$5.: z. 95%“ ME
`
`
`
`2_ 9m m0 mw'UB M4013 Q m8 n5 mvg
`
`
`
`Ill _1||||
`
`5 .
`mqdama
`
`
`
`g: .
`
`13
`
`

`

`1
`
`CORIOLIS-TYPE MASS FLOWMETER
`CIRCUITRY
`
`5
`
`CROSS-REFERENCE TO RELATED
`APPLICATION
`The present application is a division of application
`Ser. No. 07/116,257, ?led Oct. 29, 1987, now U.S. Pat.
`No. 4,911,020, which isa continuation-in-part of U.S.
`patent application Ser. No. 923,847 ?led Oct. 28,.1986,
`now U.S. Pat No. 4,89l,99l by Wade M. Mattar et al.
`entitled “Coriolis-Type Mass Flowmeter” assigned to
`the assignee of the present application and incorporated
`herein by reference in its entirety.
`
`5,050,439
`2
`point for oscillation and thus obviate separate rotary or
`?exible joints and moreover offers the possibility of
`using the resonant frequency of vibration to reduce
`drive energy.
`Several aspects of oscillating conduit Coriolis mass
`flowmeters require electronic instrumentation. First,
`inducing the oscillation in the conduit requires a drive
`control system sensitive to spurious vibration and capa
`ble usually of maintaining a constant amplitude as well
`as frequency of oscillation. Second, the movement of
`the conduit has to be detected and measured in such a
`’ way as to reveal the amount of the extraneous-deflec
`tion or offset of the conduit due exclusively to Coriolis
`force. This application presents electronic instrumenta
`5 tion for implementing drive control and sensing func
`tions in oscillating conduit Coriolis mass ?owmeters.
`
`20
`
`2 Lil
`
`30
`
`3 LII
`
`BACKGROUND OF THE INVENTION
`The present invention relates to electronic control
`and sensing circuitry for oscillating conduit Coriolis
`type mass flowmeters.
`'
`A mass flowmeter is an instrument which provides a
`direct indication of the quantity or mass, as opposed to
`volume or velocity,_ of material being transferred
`through a pipeline.
`One class of mass measuring flowmeters is based on
`the well-known Coriolis effect. Coriolis forces are ex
`hibited in the radial movement of mass on a rotating
`body. Imagine a planar surface rotating at constant
`angular.velocity about an axis, perpendicularly inter
`secting the surface. A mass travelling radially outward
`on the surface at what appears to be a constant linear
`speed actually speeds up in the tangential direction
`because the larger the radial distance of a point from the
`center of rotation, the faster the point must travel. The
`increase in velocity, however, means that the mass has
`been indirectly accelerated. The acceleration of the
`mass generates a-reaction force, called the Coriolis
`effect, in the"plane of rotation perpendicular to the
`instantaneous radial movement of the mass. In vector
`terminology, the Coriolis force vector is the cross
`product of the angular velocity vector (parallel to the
`rotational axis) and the velocity vector of the mass in
`the direction of its travel with respect to the axis of
`rotation (e.g., radial). Consider the mass as a person
`walking a straight line radially outward on a turntable
`rotating clockwise at a constant rate and the reaction
`force will be manifested as a listing to the left to com
`pensate for acceleration.
`The potential applicability of the Coriolis effect to
`mass ?ow measurement was recognized long ago. If a
`pipe is rotated about a pivot axis orthogonal to the pipe,
`.50
`material flowing through the pipe becomes a radially
`travelling mass which, therefore, experiences accelera
`tion. The Coriolis reaction force experienced by the
`travelling ?uid mass is transferred to the pipe itself as a
`de?ection or offset of the pipe in the direction of the
`Coriolis force vector in the. plane of rotation.
`Coriolis-type mass flowmeters induce a Coriolis force
`in two signi?cantly different ways: by continuously
`rotating or by oscillating back and forth. The principal
`functional difference is that the oscillating version, un
`like the continuously rotating one, has periodically (i.e.,
`usually sinusoidally) varying angular velocity produc
`ing, as a result, a continuously varying level of Coriolis
`force. A major dif?culty in oscillatory systems is that
`the Coriolis effect is relatively small compared not only
`65
`to the drive force but even to extraneous vibrations. On
`the other hand, an oscillatory system can employ the
`bending resiliency of the pipe itself aspa hinge or pivot
`
`SUMMARY OF THE INVENTION
`A general feature of the invention is a signal process
`ing and control system for a Coriolis-type mass flowme
`ter characterized by oscillating several conduit sections
`in synchronism, detecting displacement of respective
`ends of the sections and producing two corresponding
`complementary sensor outputs for each section, each
`including a drive component and a Coriolis component,
`combining corresponding ones of the displacement sen
`sor outputs for both conduit sections and recovering at
`least one of the components from the two combined
`sensor outputs.
`Preferred embodiments of the invention include the
`following features taken individually and in various
`combinations‘. An oscillatory drive signal is derived
`from the drive component and a mass flow signal is
`derived from the Coriolis component. Preferably, a
`mass ?ow indication is derived by synchronous demod
`ulation of the recovered Coriolis component with re
`spect to a quadrature reference signal. An oscillatory
`drive signal is derived from the recovered drive compo
`nent. The natural resonant frequency of the conduit
`section is tapped by proportioning the drive signal to
`the ?rst derivative of the recovered drive component.
`In the preferred embodiment, a dual loop con?guration,
`pairs of sensors and force drivers, are located at oppo
`site ends of each conduit section. The outputs of sensors
`at corresponding ends are summed. Complementary
`drive signals are applied to the respective drivers at
`opposite ends.
`Another general feature of the invention is‘related to
`providing gain balance between the sensor channels.
`Any remnant of the drive component remaining in a
`combination of the two sensor outputs designed to can
`cel the drive components is nulled by amplitude control
`of one sensor output or output channel for a combina
`tion of corresponding sensor outputs. in a preferred
`embodiment of this system, a channel gain imbalance
`signal is developed and employed to control the ampli
`tude of one sensor output. In the preferred system, the
`recovered Coriolis component is synchronously de
`modulated with respect to an in-phase reference signal
`to generate a balance error signal.
`Another general feature of the invention provides
`- compensation for drive force imbalance. In particular,
`two force drivers at opposite ends of the conduit section
`are driven by complementary drive signals to which a
`perturbation signal is added. Any remnant of the pertur
`bation signal in a combination of the two sensor outputs
`designed to cancel the drive components is nulled by
`
`40
`
`45
`
`55
`
`60
`
`14
`
`

`

`5
`
`25
`
`5,050,439
`4
`3
`tor output to improve gain balance. A perturbation
`adding compensation to both drive signals to eliminate
`signal is applied to both channels corresponding to
`drive force imbalance. In the preferred embodiment,
`opposite ends of the loop sections in quadrature with
`the perturbation signal is out-of-phase with the drive
`the sensed drive component with phase reversal every
`signal, preferably in quadrature therewith. Since such a
`few cycles. The resulting third demodulator output is
`perturbation signal would cause a gradual rotation of
`drive phase if continuously applied, the polarity of the
`combined with the drive signals to reduce drive imbal
`perturbation signal is periodically reversed. In the pre
`ance.
`ferred system, the recovered Coriolis component is
`The signal processing and control system based- on
`synchronously demodulated with a reference signal
`phase measurements, according to the invention, elimi
`replicating the phase and frequency of the perturbation
`nates the need for tracking absolute amplitude of tube
`signal to produce a drive force balance error signal. A
`deflections. In the preferred system, the same signals
`compensation signal is derived by algebraic combina
`which are employed to derive the mass flow indication,
`tion of the error signal with the drive signal.
`develop the self-oscillating drive signal. The parallel
`Another general feature of the invention is the tech
`arrangement of drivers and/or sensors for two loops
`nique of synchronously demodulating one of the recov
`enhances the symmetry and balance of the drive signals
`ered components with respect to a reference signal
`and increases the number of shared common elements.
`having a predetermined phase relationship with the
`Imbalances inherent in the' system due to differences in
`other component. For example, the recovered Coriolis
`channel gain and drive force are automatically reduced
`component is synchronously demodulated in the pre
`by closed loop control systems which improve the ac
`ferred embodiment with a reference in quadrature with
`curacy and reliability of the ?owmeter.
`the recovered drive component to yield a mass ?ow
`Other advantages and features will become apparent
`indication. A speci?c feature of the preferred embodi
`from the following description of the preferred embodi
`ment of the invention is the provision of plural synchro
`ment and from the claims.
`nous demodulators employing a plurality of respective
`reference signals each having a different phase relation
`ship with the other recovered component. One or more
`of these reference signals is developed by generating an
`intermediate signal, with a voltage controlled oscillator,
`for example, phase-locked to the recovered drive com
`ponent and at a frequency which is a multiple of the
`frequency of the recovered drive component, counting
`transitions of the intermediate signal to produce a plu
`rality of counter outputs, and logically combining the
`counter outputs to produce one or more reference sig
`nals at the same frequency and with a selected phase
`relationship to the recovered drive component for use
`as a synchronous demodulator reference.
`In the preferred embodiment, the drive control and
`measurement system is employed with a dual parallel
`loop, dual drive Coriolis mass ?owmeter in which each
`loop has an oscillating straight section with sensors and
`drivers located respectively at both ends of the straight
`section. Sensor outputs and drive inputs for correspond
`ing ends of the two loop sections are connected in paral
`lel to form respective channels. In the embodiment
`45
`speci?c to the con?guration having two loops and two
`pairs of displacement sensors, output signals from sen
`sors at corresponding ends are summed and demodu
`lated before being combined with demodulated summed
`output signals “from the sensors at the opposite ends to
`yield sum and difference signals representing, by design,
`Coriolis mode de?ection and the sensed drive compo
`nent. The sensed drive component signal is differenti
`ated and passed through a linear attenuator controlled
`by comparison of the full-wave-recti?ed drive signal
`component to a DC reference voltage. Complementary
`versions of the gain-control]ed-differentiated drive sig
`nal component are applied respectively to force drivers
`for corresponding ends of the loop section.
`The Coriolis mode deflection signal in the preferred
`embodiment is demodulated synchronously with three
`different reference signals: a ?rst signal in quadrature
`with the sensed drive component (yielding flow data), a
`second signal in phase with the sensed drive component
`(yielding gain imbalance data), and third signal alter
`nately in phase and 180° out of phase with the sensed
`drive component (yielding drive imbalance data). The
`gain of one channel is adjusted by the second demodula
`
`DESCRIPTION OF THE PREFERRED
`EMBODIMENTS
`We ?rst briefly describe-the drawings.
`FIG. 1 is an oblique isometric view of a double loop,
`dual drive, central manifold, Coriolis effect mass ?ow
`meter.
`FIG. 2 is a plan schematic view of the flowmeter of
`FIG. 1 with a' parallel flow manifold block.
`FIG. 2A is a plan schematic fragmentary view like
`that of FIG. 2 with a series flow manifold block.
`FIG. 3 is a side schematic view of the apparatus of
`FIG. 2 in elevation taken in the indicated direction
`along lines 3-3.
`FIG. 4 is a side elevational view of the apparatus of
`FIG. 1 in more detail with portions of the central mani
`fold assembly broken away to reveal the inlet and outlet
`chambers.
`FIG. 5 is a sectional view with portions in plan taken
`in the direction indicated along the lines 5-5 of FIG. 4.
`FIG. 6 is a side elevational view of the central mani
`fold assembly with the tubes and support arm in section
`taken in the direction indicated along the lines 6-6 of
`FIG. 4.
`FIG. 7 is a plan view of an in-line embodiment of a
`double loop, dual drive Coriolis effect mass ?owmeter
`in which the planes of the loops are oriented parallel to
`the process line.
`FIG. 8 is a side elevationalview of the apparatus of
`FIG. 7.
`FIG. 9 is a schematic representation of three modes
`of motion of the apparatus of FIGS. 1 and 7.
`FIGS. 10A and 10B are contrasting schematic repre
`sentations of dual and single node plates respectively .
`under exaggerated torsional in-plane deflection.
`FIGS. 11A and 11B are contrasting schematic repre
`sentations of the effect of exaggerated torsional deflec
`tion on the pipeline connected to the casting 16 in the
`‘perpendicular and in-line embodiments, respectively. _
`FIGS. 12 and 13 are schematic, perspective and plan
`representations of alternate loop con?gurations, respec
`tively.
`FIG. 14 is a functional block diagram of an electrical
`circuit for the drivers and detectors associated with the
`
`55
`
`65
`
`15
`
`

`

`5
`.
`perpendicular and in-line embodiments of FIG. 1 and
`FIG. 7.
`FIG. 15 is a functional block diagram of another
`electrical circuit for the drivers and detectors associated
`with the perpendicular and in-line embodiments of FIG.
`1 and FIG. 7.
`FIG.‘ 16 is a schematic illustration of tube end dis
`placement polarity assignments for the circuit of FIG.
`15.
`FIG. 17 is a detailed electrical schematic of the three
`part demodulator circuit of FIG. 15 which acts on the
`Coriolis mode de?ection signal.
`FIG. 18 is a detailed electrical schematic of the phase
`locked reference generator of FIG. 15.
`FIG. 19 is a timing diagram for representative signals
`in the circuit of FIG. 18.
`
`10
`
`1
`
`15
`
`20
`
`5,050,439
`6
`for example, 0.825 inch in a one-inch pipe embodiment.
`The node plate serves as a stress isolation bar and de
`?nes a common mechanical ground for each loop.
`An advantage of the node plate 41 as mechanical
`ground compared to the casting 16 is that the intercon
`nection of the plate and inlet/outlet legs 22, 24 is by way
`of completely external circular weldments on the upper
`and lower surfaces of the plate, forming two external
`rings around each leg. In contrast, the butt welds of the
`tube ends to the bosses on the casting 16 are exposed on
`the interior to the process ?uid which will tend in time
`to corrode the weldments faster if they are in constantly
`reversing torsional stress.
`Manifold casting 16 is channeled inside so that the
`inlet stream is diverted in parallel to upright legs 22 of
`loops l8 and 20 as shown in FIG. 2. The loop outlet
`from upright legs 24 is combined and diverted to the
`outlet of the meter, back to the pipeline 10. The loops 18
`and 20 are thus connected in parallel, ?ow-wise as well
`as geometry-wise.
`.
`FIG. 2A shows a variation in which the channels in
`manifold block 16’ are modi?ed for series flow through
`the loops. Blocks 16 and 16’ are otherwise interchange
`able.
`The manifold casting 16 is shown in FIGS. 4 and 5. A
`pair of offset overlapping channels 42 and 44, parallel to
`the process line, are connected to the respective integral
`inlet and outlet pipe sections 10’ by means of larger
`offset openings 46 and 48. Channels 42 and 44 are in
`communication respectively with the inlet and outlet of
`the meter to form intake and exhaust manifolds. A pair
`of vertical spaced ports 52 through the casting 16 com
`municate the inlet legs 22 of the loops 18 and 20 with the
`intake manifold formed by channel 42. Likewise, a pair
`of vertical spaced ports 54 communicate the upright
`outlet legs 24 of loops 18 and 20 with the exhaust mani
`fold formed by channel 44. As shown in FIGS. 4 and 6,
`the ends of the two pairs of upright legs 22 and 24 are
`butt welded to hollow conical'bosses 56 rising integrally
`from the casting coaxially with respective ports 52 and
`54.
`The electrical driver/detector assemblies are sup
`ported independently on the outboard ends of rigid
`opposed arms 60 and 62 in the form of T-beams securely
`attached to opposite faces of the manifold casting 16 by
`disk shaped mounting ?anges 64. Flanges 64 and casting
`16 may be matingly keyed as shown in FIG. 5 for extra
`stability. Cantilevered arms 60 and 62 extend parallel I
`within the planes of the two loops 18 and 20 and the
`vertical plates of the arms pass between the corners 38
`and 40 where the driver/ detector assemblies are located
`for both loops.
`As shown in FIGS. 1 and 5 at the end of the upper
`deck of each cantilevered arm 60, 62, two identical
`solenoid type driver assemblies 70 are located and held
`in position by driver brackets 72. Each driver comprises
`a pair of push/pull solenoid coils and pole pieces 74
`which act on ferromagnetic slugs 76 welded onto oppo
`site sides of the lower turn 38, 40. Thus, there are eight
`independent drivers, one pair for each end of each loop
`18, 20. Each driver imparts reciprocal sideways motion
`to the tube between the slugs 76.
`Problems have surfaced with solenoid drivers of the
`type shown in FIGS. 1 and 5. The solenoid actuators
`are highly nonlinear and force is dependent on static
`positions. These problems are alleviated by changing to
`a moving magnet design. The magnet may be mounted
`to and extend laterally from the side of the tube at the
`
`MECHANICAL DESIGN
`A speci?c tubular con?guration is described herein in
`two orientations, perpendicular and in-line with respect
`to the direction of the process ?ow, i.e., the direction of
`flow in a straight section of pipeline in which the meter
`is to be inserted. The implementations illustrated herein
`are designed for one inch pipelines for a variety of prod
`ucts including petroleum based fuels, for example. The
`25
`flowmeter described herein, of course, is applicable to a
`wide variety of other speci?c designs for the same or
`different applications.
`FIG. 1 illustrates a double loop, dual drive/detector
`system with torsional loading of the tube ends where
`they are connected to a single rigid central manifold
`connected in line with the process flow. The same em
`bodiment is shown in FIGS. 1, 2 and 3-6 with more
`detail being provided in FIGS- 4»6.
`The mass flowmeter of FIG. 1 is designed to be in
`serted in a pipeline 10 which has had a small section
`removed or reserved to make room for the meter. The
`pipeline 10 is equipped with opposing spaced ?anges 12
`which mate with mounting flanges 14 welded to short '
`sections of pipe 10' connected to a massive central mani
`40
`fold block 16 supporting the two parallel planar loops
`18 and 20. The con?guration of loops 18 and 20 is essen
`tially identical. Thus, the description of the shape of
`loop 18 holds true for loop 20 as well. Manifold block
`16 is'preferably a casting in the shape of a solid retangu
`lar block with a flat horizontal upper surface or top 160
`and integral pipe sections 10’. The ends of loop 18 com
`prise straight preferably vertical parallel inlet and outlet
`sections or legs 22 and 24 securely af?xed, e.g., by butt
`welding, to the top of the manifold 16a in close proxim
`ity to each other. The base of loop 18 is a long straight
`section 26 passing freely through an undercut channel
`28 in the bottom face of the casting 16. The long straight
`section 26 at the base of the loop 18 is connected to the
`‘ upright legs 22 and 24 by respective diagonal sections
`30 and 32. The four junctions between the various
`straight segments of the loop 28 are rounded by large
`radii turns to afford as little resistance to flow as posssi
`ble. In particular, upright legs 22 and 24 are connected
`to the respective diagonal segments 30 and 32 by means
`of apex turns 34 and 36 respectively. The ends of the
`long straight base section 26 are connected to the re
`spective ends of the diagonal segments 30 and 32 by'
`lower rounded turns 38 and 40.
`The parallel inlet/outlet ends 22, 24 of both loops 18
`and 20 pass through a correspondingly apertured isola
`tion plate or node plate 41 which is_ parallel to surface
`16a and spaced therefrom by a predetermined distance,
`
`45
`
`50
`
`55
`
`65
`
`16
`
`

`

`7
`location of one of the slugs 76 inside a stationary coil
`with a ferromagnetic cover, as shown schematically in
`FIG. 6A. In this embodiment, the drivers or drive mo
`tors as they are more properly termed, are energized by
`passing current through the coils in a similar manner.
`However, only one drive motor is needed for each end
`of each tube and coils for drive motors or correspond
`ing ends of respective tubes are electrically connected
`in series rather than in parallel, as indicated in FIG. 15,
`for example.
`By energizing the driver pairs on opposite ends of the
`same tube with current of equal magnitude but opposite
`sign (180° out of phase), straight section 26 is caused to
`rotate about its coplanar perpendicular bisector 79
`which intersects the tube at point c as shown in FIG. 1.
`The drive rotation is thus preferably in a horizontal
`plane about point e. The perpendicular bisectors for the
`straight sections of both loops preferably lie in a com
`mon plane of symmetry for both loops as noted in FIG.
`1.
`
`35
`
`Repeatedly reversing (e.g., controlling sinusoidally)
`the energizing current of the drives 70 causes the
`straight section 26 of the loop 18 to execute an oscilla
`tory motion about point c in the horizontal plane. The
`motion of each straight section 26 sweeps out a bow tie
`25
`shape. The entire lateral excursion of the loop at the
`corners 38 and 40 is small, on the order of g of an inch
`for a two foot long straight section 26 for a one inch
`pipe. This displacement is coupled to the upright paral
`lel legs 22 and 24 as torsional de?ection about the axes
`of the legs 22 and 24 beginning at the node plate 41. The
`same type of oscillatory motion is induced in the
`straight section of the loop 20 by the other respective
`pair of complementary drives 70 supported on the outer
`ends of the upper deck of the cantilevered arms 60 and
`62, respectively.
`The central vertical portion of the T-beam extends
`between the corners 38 and 40 of the two loops 18 and
`20, respectively, and supports detector assemblies 80 on _
`brackets 82 at the respective ends of the arms 60 and 62.
`Each of the four detector assemblies 80 includes a posi
`tion, velocity or acceleration sensor, for example, a
`variable differential transformer having a pair of coils
`mounted on the stationary bracket 82 and a movable
`element between the coils affixed to the tube corner 38,
`40. The movable element is connected to a strap welded
`to the corner 38, 40 of the loop as shown. Conventional
`optical, capacitive or linear variable displacement trans
`ducers (LVDT’s) may be substituted. It is desirable for
`the position detector to have an output that is linear
`with respect to displacement over the limited deflection
`range and relatively insensitive to motions substantially
`skewed with respect to the plane of the respective loop.
`However, the implementation of the detector is a matter
`of design choice and does not form a part of the present
`invention.
`The driver detector assembly pairs 70, 80 for loop 18
`are designated A and B corresponding to the opposite
`ends of the straight section 26 of loop 18. Likewise, the
`driver/detector assemblies for the other parallel loop 20
`are designated C and D for the left and right ends as
`viewed in the drawing.
`An alternate embodiment of the same parallel loop
`con?guration shifted 90° is shown in FIGS. 7 and 8.
`Here, the planes of the loops l8 and 20 are‘ arranged
`parallel to the process ‘?ow direction. In-line pipe sec
`tion 10” connecting the mounting ?ange to the some
`what abbreviated manifold casting'16 is extended (or
`
`20
`
`5,050,439
`8
`connected to another pipe segment) to traverse the
`entire length of one side of the loops 18 and 20. The
`motion of the loops and location of the node plate and
`driver/detector assemblies are identical to those in the
`perpendicular embodiment of FIG. 1. In the in-line
`embodiment of FIGS. 7 and 8, however, the driver/de
`tector assembly arms 60' and 62’ may, if desired, be
`supported over their entire length by the respective
`pipe section 10". The parallel flow paths among the
`loops 18 and 20 in FIGS. 7 and 8 are identical to those
`in the embodiment of FIG. 1. The channeling of the
`manifold casting 16" is somewhat different in that the
`manifolds 42' and 44' are perpendicular to the coaxial
`inlet/outlet lines.
`The motion of the straight sections 26 of loops 18 and
`20 for either perpendicular or in-line embodiments is
`shown in three modes a,'b and c in FIG. 9. Drive mode
`b is oscillatory about point 0 with the two loops rotating
`synchronously but in the opposite sense, i.e., while loop
`18 rotates clockwise, loop 20 is undergoing counter
`clockwise rotation. Consequently, respective ends such
`as a and c as shown in FIG. 9 periodically come to
`gether and go apart. This type of drive motion induces
`Coriolis effects in opposite directions as shown in a of
`FIG. 9. Coriolis mode motion thus tends to pivot the
`whole planes of the loops 18 and 20 respectively but in
`the opposite direction. The Coriolis effect is greatest
`when the two straight sections 26 are parallel as shown
`in a of FIG. 9 because the sinusoidally varying angular
`velocity is then at its maximum. Because the Coriolis
`mode motion of each loop is in the opposite direction,
`the straight sections 26 move slightly toward (or away
`from) each other as shown in a of FIG. 9.
`A common mode motion undesirable in this instru
`ment, would be one which deflected the loops in the
`same direction as shown in c of FIG. 9. This type of
`motion might be produced by an axial wave in the pipe
`line itself in the embodiment of FIG. 1 because the loops
`are oriented perpendicularly to the pipeline. The in-line
`embodiment of FIGS. 7 and 8 might be less susceptible
`to this type of extraneous vibration.
`The resonant frequency of the Coriolis motion and
`common mode motion should be determined by design
`con?guration to be different from the resonsant fre
`quency of the oscillatory motion of the straight section,
`i.e., the drive mode.
`The further the displacement of the node plate 41 in
`FIG. 1 from the casting 16, the higher the resonant
`frequency of the loop in the drive mode. However, the
`node plate also tends to reduce the Coriolis effect dis
`plac