How the Micro Motion
`Mass Flow and Density
`Sensor Works
`
`Mass Flow Measurement:
`Theory of Operation
`
`.cycle, it twists in the opposite direction. This
`tube twisting characteristic is called the
`Coriolis effect.
`
`The Micro Motion flowmeter measures finid
`mass in motion. A flowmeter is comprised of a
`sensor and a signal processing transmitter.
`Each sensor consists of one or two flow
`tubes enclosed in a sensor housing. The prin-
`ciple of operation is the same for all Micro
`Motion sensors. (cid:9)
`
`.
`. (cid:9)
`The sensor operates by application of New-
`ton's Second Law of Motion: Force = mass x
`acceleration IF = ma). The floWmeter uses this .
`law to determine the precise amount of mass
`flowing through the sensor tubes, .
`
`Due to Newton's Second Law of Motion, the
`amount of sensor tube twist is directly propor-
`tional to the mass flow rate of the fluid flow-
`ing through the tube. Electromagnetic velocity
`' detectors located on each side of the flow tube
`measure the velocity of the vibrating tube. The
`two velocity signals are sent to the transmitter
`where they are processed and converted to an
`output signal proportional to the mass flow
`rate. Sensor tube twist is proportional to mass
`flow and is determined by measuring the time
`difference exhibited by the velocity detector
`signals. During zero flow conditions, no tube
`Inside the sensor housing, the flow tube is vi-
`twitted at its natural frequency (11,:igure II by an '7 twist occurs and both sides of the tube cross
`electromagnetic drive coil locatec,'at the cenzrq the midpoint simultaneously. With flow, a
`twist occurs along with a resultant time differ-
`ter of the bend in the tube. The vibration is — (cid:9)
`similar to that of a tuning fork, covering less (cid:9)
`ence between midpoint crossing. This time
`than a tenth of an inch and completing-a fuff (cid:9)
`'difference appears as a phase shift between
`the two velocity signals and indicates mass
`cycle about 80 times each second. (cid:9)
`flow.
`
`As the fluid flows into the sensor tube, it is •
`forced to take on the vertical momentum of
`the vibrating tube. When the tube is moving
`upward cluring half of its vibration cycle (Fig-
`ure 21, the fluid flowing into the sensor resists
`being forced upward by pushing down on the
`tube. Having the tube's upward momentum as
`it travels around the tube bend, the fluid flow-
`ing out of the sensor resists having its vertical
`motion decreased by pushing up on the tube
`(Figure 2I. This causes the lion, tube to twist
`(Figure 3). When the tube is ntoying
`ward during the second halt of its vibration
`
`Benefits of Mass Flow Measurement
`
`Micro Motion flowmeters measure mass flow
`directly -not be inferred methods. The basis
`for all measurement is mass, length, and time.
`Since none of these is derived from another
`source, each is an ideal standard for accurate
`measurement. In the case of mass, this means
`that changes in fluid parameters such as tem-
`perature, pressure, density, viscosity, and
`conductivity have no affect on the mass of the
`fluid being measured.
`
`Fluid
`Force
`
`Figure 1
`Vibrating flow tube
`(single now tube shown)
`
`Flood
`Force
`
`Figure 2
`Fluid forces reacting to vibration of
`flow tube
`
`Twist
`Angle
`
`Figure 3
`End view of flow tube showing twist
`
`Micro Motion 1009
`
`1
`
`

`

`Density Measurement and
`Improved Process Control
`
`Density Measurement:
`Theory of Operation
`
`Coriolis flowmeters are excellent densitome-
`ters. The U-shaped sensor tubes are mounted
`in a fixed arrangement on one end and are
`free on the other end. This design configura-
`tion can be envisioned as a spring and mass
`assembly. The laws of physics describe the
`behavior of both systems; the relationship be-
`tween density (mass of fluid in the tubes) and
`vibrational frequency can be quantified.
`Once placed into motion, the spring and mass
`assembly will vibrate at its resonant frequen-
`cy. The Coriolis sensor is also vibrated at its
`resonant frequency using a feedback circuit
`and drive coil.
`
`A vibrating spring system can be mathemati-
`cally described. It is important to emphasize
`that the mass of the Coriolis spring assembly
`is comprised of two parts; the mass of the
`tube and the mass of the fluid in the tube. The
`mass of the tubes is fixed tor a given sensor.
`Since mass (fluid in the tubes) = density x
`tube volume, and the tube volume is a con-
`stant for any given sensor size, frequency of
`tube oscillation can be related to fluid density.
`Equation 1 shows how mass is determined.
`Equation 2 shows that fluid density is inverse-
`ly proportional to the square of the frequency.
`
`f
`
`2n
`
`P=
`4n 2Vf 2
`
`Mnibe
`
`V
`
`equation 1
`
`equation 2
`
`where f = frequency of oscillation
`K — spring constant
`m= mass
`V = volume
`p = density
`
`Benefits of Density Measurement
`Micro Motion density measurement products,
`in conjunction with a signal processing trans-
`mitter and sensor, offer accurate, on-line den-
`sity measurement that enhances process meas-
`urement and control. Density is an important
`process parameter for what it indicates about
`product quality, uniformity, and concentration.
`For example, acid and base concentration, %
`solids of slurries, Brix, % solids black liquor,
`net oil, and many other variables can often be
`determined by density measurement.
`
`Coriolis Flowmeter
`
`Spring & Mass
`Assembly
`
`/ 1
`
`M
`
`Micro Motion, Inc. (cid:9)
`
`7070 Winchester Circle • Boulder, Colorado 80301 • 1-303/530-8400 • TLX 450034 MICRO MOT BLDR
`Ordering and 24-hour service line: 1-800/522-6277 (MASS) • Application information and literature requests:
`1-800/322-5867 (JUMP) (in Colorado or outside the US, call 1-303/530-8400) • FAX 1-303/530-8422
`Europe: Groeneveldselaan 6, 3903 AZ, Veenendaal, The Netherlands, PH: 31-8385-63911, TLX: 844-37106, FAX 8385-63314
`
`.•1990. Micro Motion, Inc_ (cid:9)
`All Rights fil!Sell'ed
`
`7-90
`
`2
`
`

`

`Prodnutrit
`
`
`
`Micro Motion, Inc. advances Coriolis technology
`
`Model D65 Mass Flow
`and Density Sensor
`
`Micro Motion, Inc. continues to expand
`its product line with the introduction
`of the Model D65 mass flow and densi-
`ty sensor. Incorporating the latest in
`Coriolis sensor design, the D65 is an in-
`line Model D sensor designed for flow
`
`ranges from 0 to 15 lb/minute (0 to 6.8
`kg/minute) up to 0 to 300 lb/minute (0
`to 136 kg/minute).
`
`The D65 sensor offers all the benefits of
`a Model D sensor and is compatible
`
`with all Micro Motion transmitters, in-
`cluding the RFT SMART FAMILY°
`transmitter. It is offered with a variety
`of process connections; including 1/2-
`inch and 1-inch ANSI flanges and sani-
`tary fittings. Consult the specifications
`for more information and for dimen-
`sions.
`
`Accuracies for the D65 are +02% ±0.03
`lb/minute (0.014 kg/minute) for mass
`flow and as precise as ±0.001 glee for
`density.
`
`Features
`• Direct, mass flow measurement
`• Simultaneous density measurement
`• Non-intrusive sensor in compact, her-
`metically-sealed case
`• No moving parts
`• Remote electronics
`• Independent of:
`Temperature
`Pressure
`Density
`Viscosity
`Flow Profile
`
`Benefits
`• Superior accuracy
`• Universal calibration in mass units
`• Linear output
`• Maintenance free
`• No meter run requirement
`
`3
`
`(cid:9)
`

`

`Physical
`Characteristics
`
`Dimensions are in
`inches (mm)
`
`11
`(279)
`
`3.5
`(84)
`
`3
`(76)
`
`I
`
`14 (356)
`
`16.69 (424)
`
`Dim 'B'
`
`1 (cid:9)
`
`
`
`2.94 (75)
`
`3/4-14 NPT Fern.
`
`4
`4 (102)
`
`Junction Box
`4-inch (102) Dia
`
`3.94 (100)
`
`1/2 inch NPT Fem. Conduit Bushing
`
`Face to Face
`Dim 'A
`
`Shown
`
`1/2-inch ANSI
`Raised Face
`Flange
`(B16.5)
`
`1-inch ANSI
`Raised Face
`Flange
`(B16.5)
`
`Fitting
`
`—\
`1501b
`300 lb
`600 lb
`_ 900 lb
`#12 Union -3/4" NPT Fem.
`DIN PN40
`San-fig 1"(1-1/2" Clamp)
`JS14
`— JS12
`150 lb*
`300 1b*
`
`Dim 'A'
`+125 (3.2)
`
`16.19 (411)
`16.56 (421)
`17.06 (433)
`17.69 (449)
`14.31 (364)
`15.44 (392)
`16 (406)
`15.38 (391)
`15.19 (386)
`17.13 (435)
`17.63 (448)
`
`Dim 'B'
`
`3.5 (89)
`3.75 (95)
`3.75 (95)
`4.75 (121)
`1.19 (30)
`3.75 (95) (cid:9)
`2 (51)
`3.75 (95)
`3.75 (95)
`4.25 (108)
`4.88 (124)
`
`.
`
`*Matches face-to-face dimension of a D100 sensor with the same fitting.
`
`7070 Winchester Circle • Boulder, Colorado 80301 • 1-303/530-8400 • TLX 450034 MICRO MOT BLOB
`Service: 1-800/522-MASS, 24-hour line • Sales: 1-800/322-Jump for ordering and application information
`(Colorado, or outside U.S. call 1-303/530-8400) • FAX 1-303/530-8422
`
`In Europe: Groeneveldselaan 6, 3903 AZ, Veenendaal, The Netherlands, PH: 31-8385-63911, TLX: 37106, FAX 8385-63314
`
`01990, Micro Motion, Inc.
`All Rights Reserved
`
`4
`
`(cid:9)
`

`

`No-
`
`O
`
`O
`
`10 (cid:9)
`
`20 (cid:9)
`
`30 (cid:9)
`
`50
`
`100
`
`150
`
`Flow Rate (kg/minute)
`
`10
`
`5
`
`3
`
`1.0
`
`0.5
`
`0.3
`
`0.1
`
`0.05
`
`0.03
`
`0.01
`
`0.005
`
`0.003
`
`0.001
`5
`
`Pressure Drop (bar)
`
`Sensor
`Pressure Drop Charts
`
`0'
`
`20 (cid:9)
`
`30 (cid:9)
`
`50 (cid:9)
`
`100
`
`200
`
`300
`
`Flow Rate (lb/minute)
`
`150
`
`100
`
`50
`
`30
`
`10
`
`5
`
`3
`
`1
`
`.5
`
`.3
`
`.1
`
`.05
`
`.03
`10 (cid:9)
`
`Pressure Drop (psi)
`
`µ is fluid dynamic viscosity in centipoise. Pressure Drop Charts are for specific gravity = 1.0 SGUW. Consult Mass Flowmeter Se-
`lection Guide when correcting for other densities.
`
`D65 Sensor Sizing
`Information
`
`Equivalent Pipe Lengths
`
`Sched 40 pipe size (in.)
`
`Equiv. Pipe
`Length (ft.)
`
`Pipe Internal
`Dia. (mm)
`
`Equiv. Pipe
`Length (meters)
`
`0.5
`
`0.75
`
`1
`
`11
`
`45
`
`150
`
`16
`
`21
`
`27
`
`3.6
`15
`
`49
`
`Velocity factor (V) — .17 (.11 metric)
`
`For further information on use of the above sizing information consult the Micro Motion
`Mass Flowmeter Selection Guides.
`
`5
`
`

`

`Specifications
`
`Sensor
`Specifications
`
`Flow range
`Maximum
`Minimum
`
`Accuracy
`Mass
`Density
`
`Zero stability
`
`0 to 300 lb/min (0 to 136 kg/min)
`0 to 15 lb/min (0 to 6.8 kg/min) with RFT9712
`or FlowScale transmitters.
`
`±0.2% ± zero stability
`+0.001 g/cc with DMS or Net Computers; ± 0.002
`g/cc with RFT9712 only
`
`0.03 lb/min (0.014 kg/min)
`Zero set at process temperature ±20°F (±11°C)
`
`Operating temperature
`
`-400° to 350°F (-240 to 177°C)
`
`Rated operating pressure
`
`2250 psig (153 bar)
`
`Wetted parts
`
`316L stainless steel
`
`Sensor housing
`
`Hermetically-sealed 304 stainless steel
`
`Fluid fittings
`
`See Physical Characteristics
`
`Area classification
`
`UL and CSA approved for Class I, Div. 1, Groups
`C, D; Class II, Div. 1, Groups E,F,G; Class I, Div. 2,
`Groups A,B,C,D with RFT9712 transmitter.
`Cenelec and SAA approvals for EEx ib IIB T4 with
`the RFT9712 transmitter are pending.
`
`Weight
`
`17.3 lb (7.8 kg) with 1/2-inch 150-lb flanges
`
`6
`
`