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Vortex tx principle

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• These drawings show what happens when a golf ball moves through the air. When it’s moving slowly, like in a putt, the air flows smoothly around it like in the top drawing. This is called laminar flow and it doesn’t make any noise. The second illustration shows how air travels around the ball after a chip shot. There is some turbulence, but it’s not regular or strong. The bottom drawing shows how air travels around the ball during a hard drive. The ball is a blunt object. When air moves quickly around it, a strong regular eddy pattern, know as vortex shedding, will always be generated in its wake. The whiz you hear as it goes by is caused by these eddy’s tearing off the back of the ball. There are other examples of vortex formation: wind whistling through telephone wires, swirls of leaves behind a moving car, and whirl pools in a brook downstream of a rock.
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• This is a view from space looking down on a mountain top. The wind is blowing the clouds (from left to right) past a mountain top (the dark object to left of center). Notice the vortex formation within the clouds. With a streamline obstruction, the vortices would form alternately on each side of the obstruction. What we see here are two vortices on one side and a new vortex forming on the other side. The reason for this is the mountain top is non-symmetrical. ______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
• The shedding of vortices is a naturally occurring phenomenon dependent upon two key elements - a bluff body and a flowing medium. An analogy can be drawn between a flag pole and the shedder bar as the bluff body.
When you see a flag flapping in the breeze you are witnessing the same phenomenon that makes a vortex flowmeter work. The flapping is caused by a vortex alternately being created on either side of the flag and moving down stream with the wind. The vortex is a swirl of low pressure that pulls the flag in the direction of the vortex. The faster the wind blows, the faster these vortices are created and the faster the flag flaps.
In the case of a vortex flowmeter, inserting a non-streamlined part (bluff body) in the flow stream causes vortices to be alternately shed. The shedder bar in YEWFLO performs two functions; it creates the vortices and with the addition of our piezoelectric crystals senses them too. To assure regular vortex formation, the flow must be turbulent. In the case of YEWFLO this means a Reynolds number of at least 5000.
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• The one feature that is universal among the various vortex flowmeter designs is that the bluff body has a sharp edge on its upstream edge. It is this edge that improves the strength and regularity of vortex shedding. The sharp edge is only there to define the point of separation of the vortex swirl. Its sharpness is not critical to maintaining meter accuracy. In some installations the bluff body has suffered severe damage on the sharp edge, due to foreign matter striking it, without having significant effect on the meter’s accuracy.
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• The frequency of vortex shedding is directly proportional to the velocity of the flow in the pipe, which permits measurement of the flow rate by sensing the frequency of the vortex formation on the alternate sides of the bluff body. From this equation it can be seen that the Strouhal number must be determined and held constant for the vortex phenomenon to serve as a viable flow metering technique.
What is the Strouhal number? The Strouhal number is the ratio between the interval between the vortices and the shedder bar width. Since the shedder bar width is fixed, for the Strouhal number to remain constant the vortex interval must also be held constant. This interval remains constant when the pipe Reynolds number is within a certain range.
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• This graph shows that for YEWFLO the Strouhal number is constant and linear when the Reynolds number is above 20,000 . A 20,000 Reynolds number therefore defines the minimum linear flow rate while the maximum linear flow is defined by a velocity limitation. The Strouhal number becomes non-linear in the Reynolds number range of 5000-20,000, but is repeatable . Therefore, if viscosity and density remain constant, and in turn the Reynolds number, a correction factor can be applied to the output to compensate for this non-linearity. The 5000 Reynolds number then defines the “measuring” range of the meter at the low end..
A feature of the Style E amplifier is a Reynolds number correction function which linearizes the area from 5000-20000 Reynolds number. When activated, the flowmeter accuracy is 0.8-1% of rate in this range.
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• This graph illustrates the linearity associated with the output signal from a vortex meter. The output is linear between flow values referred to as Qmin and Qmax., which are the minimum and maximum linear flow rates.
Qmax is determined by a velocity limit of 10 m/s for liquids and 80 m/s for gas and steam . These are not hard velocity limits in that they can be exceeded by up to 15% on application.
While the K-factor of the meter is unaffected by changes in viscosity, density, pressure, etc.., the velocity at which vortices begin to be created and become stable enough to measure accurately will vary. We refer to this value as Qmin. Let’s go back to the flag example. We have all seen the flag flapping in the breeze, but on some days we can feel the breeze blowing but the flag isn’t flapping. Why not? For the flag to flap there must be enough breeze blowing, or energy, to lift the flag and create fully developed vortices. This is the same thing that happens in the vortex meter. In reality, high fluid viscosity&apos;s and/or low fluid densities will affect the value of Qmin. The YEWFLO sizing program does the number crunching to calculate this value and Qmax. By entering the customer’s process conditions, a performance table for all meter sizes is generated.
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• The above equation is basically the same used to describe the lift on an airplane wing. As the airplane gains more speed as it moves down the runway, the lift force increases to the point required to lift the plane into the air. You can see that the lift force, and in the case of the YEWFLO the magnitude of the amplitude of the pulse from the piezoelectric crystals, increases rapidly since it goes up as the square of the flowing velocity. Because of this relationship, the signal quickly overcomes any extraneous pipe noise which may exist in the system.
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• Differential Switched Capacitor Sensor (far left): Lateral port holes in the bluff body guide vortex pressure pulses into the oscillating tongue sensor. A drain port is provided to drain any trapped liquids inside the bluff body. Two electrodes are mounted on a single carrier rod and are centred in the lower cylindrical portion of the sensor. Two equal capacitors are formed between the electrodes and the inner wall of the oscillating tongue. Vortex pulses acting on the tongue mistune the capacitors which is detected by the differential switched capacitor circuit.
Thermistor Sensor (top right): This is an early design which incorporated a thermistor embedded in the shedder bar. Small differences in temperature were detected as the vortex swirls separated from the bluff body.
Integral Diaphragm Sensor (bottom right): A thin wall diaphragm on each side of the shedder bar is stressed by the vortex pressure pulses. The stress is transmitted via a silicone oil fill to a stress detector (piezoelectric). Later designs moved the diaphragm from the shedder bar up into the body of the meter, where it was less subject to damage.
YEWFLO Shedder Bar (middle): Embedded in the shedder bar are piezoelectric crystals. The frequency of stress changes in the shedder bar caused by the alternating lift of vortex formation is sensed by the crystals.
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• YEWFLO’s unique sensor design locates two piezoelectric crystals within the shedder bar itself. There are no ports or passages or linking mechanisms required to stress the crystals. This makes for a very reliable and rugged sensor. Notice there are no wetted welds and that the crystals are hermetically sealed from the environment. Two crystals are used for the purpose of noise reduction and improved signal strength. This is accomplished through the noise balance procedure, something unique to JYC. ______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
• YEWFLO’s unique sensor design locates two piezoelectric crystals within the shedder bar itself. There are no ports or passages or linking mechanisms required to stress the crystals. This makes for a very reliable and rugged sensor. Notice there are no wetted welds and that the crystals are hermetically sealed from the environment. Two crystals are used for the purpose of noise reduction and improved signal strength. This is accomplished through the noise balance procedure, something unique to JYC.
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• The real strength of YEWFLO is the rugged sensor design. The solid metal shedder bar is virtually indestructible, allowing YEWFLO to survive even the most radical process upset.
There are no ports to plug or torque tubes to break. No holes in the shedder bar reduce the possibility of failure or K-factor shift due to plugging from process contamination. With no thin diaphragms or torque tubes, YEWFLO is not subject to failure due to over-range flows or small amounts of corrosion .
YEWFLO features flowmeter bodies which meet all requirements of ANSI for pressure, temperature and metallurgy. Solid metal shedder bar seals limit the potential for fugitive emissions.
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• YEWFLO offers communication flexibility to communicate via remote handheld or locally through the local display interface or handheld terminal. DCS communication is also available.
It is programmable for;
1. type of output: 4-20 mA or pulse
2.type of display
3.thpe of process
It can correct for errors due to gas expansion and incorrect schedule pipe.
From a maintenance perspective the YEWFLO provides:
1. a more stable signal due to digital signal conditioning
2. the ability to drive the output to check the integrity of the loop
3. access to real time digital information
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• Vortex meters in general offer many advantages. For example:
A more accurate flow at a lower installed cost (the improved accuracy is due to the digital flow signal which provides an inherently linear output).
A wider application envelope providing wider rangeability when measuring liquids, gases or steam.
Measurement accuracy will not be affected by changes in density or viscosity when measuring in the operating range of the meter as defined by the YEWFLO sizing program.
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• To obtain maximum performance, the vortex flowmeter should be installed in a pipe with a straight run the same size as the nominal size of the meter. On the upstream side, the amount of straight run required depends on what is in the pipe ahead of the meter. The pipe on the downstream side of the meter should always be at least 5 diameters. Refer to the illustrations for the minimum straight run for a particular installation. Note that in all installations the mating pipe on either side of the meter must match the meter size.
If the meter cannot be located in the piping where the minimum straight run requirements can be met, it may be possible to install flow conditioners upstream of the vortex meter and reduce the upstream piping without significantly reducing the accuracy. Johnson Yokogawa provides a full range of flow conditioners for this purpose.
We recommend pipe schedule 40 for 1/2” through 2” meter sizes. For meters larger than 2”, use schedule 80 pipe or smaller. If pipe schedule other than above is used, Parameter D05 in the YEWFLO amplifier can be used to correct for errors due to mismatched pipe schedule.
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• YEWFLO can be installed at any angle around the pipe, with the converter located above, below or to the side of the piping, whatever suits the selected installation location best. Flow may be horizontal or vertical, as long as the pipe is completely full. For liquid applications vertical flow up is preferred, as this guarantees a full pipe at all times.
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• When metering a gas or steam where pressure and/or temperature compensation is required, pressure and temperature taps must be located downstream of the vortex meter. For pressure measurements, locate the pressure tap 3.5 to 7.5 inner pipe diameters downstream of the vortex shedder bar. For temperature measurements, the temperature tap should be located 1 to 2 inner pipe diameters downstream of the pressure tap.
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• The ID of the gaskets must be equal to or larger than the ID of the meter and mating pipe. the gaskets should be the self-centering type. It is important that the gaskets not protrude into the flow stream, otherwise accuracy will be adversely affected.
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• Rosemount requires 40D after an elbow; 4 times our recommendation of 10D. When a gate valve for throttling flow is mounted upstream of any meter, straight run requirements are usually considerable. Such is the case for both Rosemount and YEWFLO. A 30D to 40D straight run is recommended.
When the Rosemount meter is installed following the same piping recommendation as YEWFLO, their specified accuracy degrades. An additional 0.85% is added to their accuracy statement making liquid accuracy 1.5% and gas or steam 2.25% for an analogue meter and 2.2% with a pulse output.
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• When a Rosemount meter is installed after a reducer, Rosemount recommends 15D upstream of the meter while YEWFLO’s requirement is only 10D. With an expander their requirement is 35D upstream to our 10D.
When the Rosemount meter is installed following the same piping recommendation as YEWFLO, their specified accuracy degrades. An additional 0.85% is added to their accuracy statement making liquid accuracy 1.5% and gas or steam 2.25% for an analogue meter and 2.2% with a pulse output.
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• The differential switched capacitor sensor of Endress &amp; Hauser detects the vortices shed by the bluff body. The lower sensor section contains the capacitive pick-up system which projects into the radial bore of the bluff body. Lateral port holes in the bluff body guide vortex pressure pulses into the oscillating tongue sensor. A drain port is provided to drain any trapped liquids inside the bluff body.
Two electrodes are mounted on a single carrier rod and are centred in the lower cylindrical portion of the sensor. Two equal capacitors are formed between the electrodes and the inner wall of the oscillating tongue. Vortex pulses acting on the tongue mistune the capacitors, which is detected by the differential switched capacitor circuit. The elastic behaviour of the carrier rod and tongue are matched, which effectively cancels any pipe vibration acting on the sensor. The carrier rod and tongue move in synchronism regardless of the axis of vibration. In theory, any external effects of vibration are eliminated and only vortex pulse signals are processed by the electronics.
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• This adjustment balances the noise component in the output of the two piezoelectric crystals so that a high signal to noise ratio can be obtained. The crystals are positioned in the shedder bar so that one crystal primarily measures flow frequency, but unfortunately picks up some pipe vibration noise also. The other crystal is positioned such that it picks up primarily the pipe vibration noise. The construction and position of the crystals is also such that the ratio of the noise component of each crystal’s output (N1/N2) is approximately constant regardless of the frequency of noise vibration and acceleration.
By performing the noise balance procedure, N2 is set equal to N1. Since the output of the lower crystal is 180 deg. out of phase with the upper crystal, and therefore has reverse polarity, when the output of the two crystals is added the noise component is eliminated:
SNET = (S1 + N1) + NB(-S2 -N2)
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• This adjustment balances the noise component in the output of the two piezoelectric crystals so that a high signal to noise ratio can be obtained. The crystals are positioned in the shedder bar so that one crystal primarily measures flow frequency, but unfortunately picks up some pipe vibration noise also. The other crystal is positioned such that it picks up primarily the pipe vibration noise. The construction and position of the crystals is also such that the ratio of the noise component of each crystal’s output (N1/N2) is approximately constant regardless of the frequency of noise vibration and acceleration.
By performing the noise balance procedure, N2 is set equal to N1. Since the output of the lower crystal is 180 deg. out of phase with the upper crystal, and therefore has reverse polarity, when the output of the two crystals is added the noise component is eliminated:
SNET = (S1 + N1) + NB(-S2 -N2)
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• This adjustment balances the noise component in the output of the two piezoelectric crystals so that a high signal to noise ratio can be obtained. The crystals are positioned in the shedder bar so that one crystal primarily measures flow frequency, but unfortunately picks up some pipe vibration noise also. The other crystal is positioned such that it picks up primarily the pipe vibration noise. The construction and position of the crystals is also such that the ratio of the noise component of each crystal’s output (N1/N2) is approximately constant regardless of the frequency of noise vibration and acceleration.
By performing the noise balance procedure, N2 is set equal to N1. Since the output of the lower crystal is 180 deg. out of phase with the upper crystal, and therefore has reverse polarity, when the output of the two crystals is added the noise component is eliminated:
SNET = (S1 + N1) + NB(-S2 -N2)
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• ### Vortex tx principle

1. 1. YEWFLO Vortex Flowmeter from yewflo april 1997 YOKOGAWA 1
2. 2. History of YEWFLO 1969 Yokogawa designs first Vortex meter 1995 Mass YEWFLO introduced 1982 Dual piezoelectric sensor 1979 First industrial YEWFLO released yewflo 1990 10,000 units (Europe) 1987 First 0.5inch Vortex flowmeter 1992 YEWFLO 100% European made 1989 First “Smart” Vortex flowmeter april 1997 1993 Microproccessor based “SMART” YOKOGAWA 2
3. 3. Principle of Operation Mountain top Vortices yewflo april 1997 YOKOGAWA 5
4. 4. Principle of Operation Light breeze - Laminar flow, no vortices formed Stiff breeze - Transition flow, irregular vortex formation Strong wind - Turbulent flow, regular vortex pattern yewflo april 1997 YOKOGAWA 6
5. 5. Principle of Operation Vortices shed continuously Alternating from side to side Shedding frequency proportional to velocity yewflo april 1997 YOKOGAWA 8
6. 6. YEWFLO’s Unique Sensor Construction How Does It Work? Crystal A Crystal B Force Force yewflo Force april 1997 YOKOGAWA 9
7. 7. Principle of Operation The Karman vortex frequency “f” is proportional to the velocity ”v”. Therefore, it is possible to obtain the flow rate by measuring the Karman vortex frequency: f = St (v/d) where: f = Karman vortex frequency St = Strouhal number (constant) v = Velocity d = Width of vortex shedder yewflo april 1997 YOKOGAWA 10
8. 8. Principle of Operation St = Strouhal number (constant) FLOW d TOP A d/A ≈ 0,14 (for almost all suppliers) By increasing the flow velocity (V) the distance ‘A’ is constant only the number of vortex per time period increases (frequency). yewflo april 1997 YOKOGAWA 11
9. 9. Principle of Operation VELOCITY S T R O U H A L # 80 M/s (GAS) 10 M/s (LIQUID) LINEAR RANGE 0.3 0.2 MEASURING RANGE 0.1 5 x 103 yewflo 2 x 104 REYNOLDS NUMBER april 1997 YOKOGAWA 12
10. 10. Principle of Operation 21,8 mA 20 mA 4 mA 0 mA yewflo april 1997 YOKOGAWA 13
11. 11. Principle of Operation 1. Vortices are generated by the shedder bar 2. Shedder bar is subjected to alternating lift a. Occurs at the same frequency as that of vortex shedding 3. Alternating lift produces stress changes detected by the piezoelectric elements hermetically sealed in the shedder bar 4. The intensity of the alternating lift, and in turn the amplitude of the pulse (E), is given by: E = FL = (rV2) yewflo april 1997 YOKOGAWA 14
12. 12. Technical Features POTTING COMPOUND CAPSULE ASSEMBLY “O” RING SEAL HERMETIC SEAL METAL TUBE METAL DISC CERAMIC PLATE INSULATOR (SHRINK TUBING) PIEZOELECTRIC CRYSTALS METAL PLATE SOLID METAL SHEDDER BAR yewflo april 1997 YOKOGAWA 17
13. 13. Technical Features “O” Ring Seal Metal Tube Piezoelectric Crystals Metal Plate Metal Disc Ceramic Plate Solid Metal Shedder Bar yewflo april 1997 YOKOGAWA 18
14. 14. Technical Features Solid metal shedder bar No thin diaphragms to damage Non-wetted piezoelectric sealed sensor Proven reliability 250 year MTBF yewflo No ports to plug april 1997 YOKOGAWA 19
15. 15. Technical Features Indicator/Totalizer Local Interface Amplifier • Remote available Gasket Hermetically Sealed Sensor • High Reliability Body • Fully casted Shedder Bar • Solid metal • Rugged construction • No moving parts yewflo april 1997 YOKOGAWA 20
16. 16. Use & Application (Money wise) 1996 P.D 16% Thermal 8% Coriolis 12% Magnetic 17% yewflo 2000 Turbine 15% Thermal Coriolis 7% Ultrasonic 11% D.P. 14% Other .5% P.D. 16% 14% Magnetic 17% Vortex 6% april 1997 Turbine 13% Ultrasonic 12% D.P. 14% Other .7% Vortex 7% YOKOGAWA 22
17. 17. Use & Application YEWFLO*E Sales By Meter Size Units 15.0% 10.0% 5.0% Percentage of Total 20.0% 0.0% 15 25 40 50 80 100 150 200 250 300 Meter Size (mm) yewflo april 1997 Units % YOKOGAWA 24
18. 18. Use & Application Orifice/DP - Lower installed cost, higher accuracy, no zero drift Turbine - No moving parts Mass - Pressure/temperature compensated gas/steam Vortex Mass Orifice/DP Turbine PD Mag Rotameter Ultrasonic Vortex < 6% yewflo april 1997 YOKOGAWA 26
19. 19. Use & Application Huge flowmeter market untapped by Vortex Vortex is still a “NEW” technology All Flowmeters YEWFLO The real competition is other flowmeter technologies yewflo april 1997 YOKOGAWA 27
20. 20. Use & Application  BEST       Liquid, gas, and steam applications Clean, low viscosity fluids Low corrosive chemicals Cryogenic fluids Fluid temperatures up to 400 degr.C Marginal  Moderately viscous fluids (i.e... 3 to 10 cp.)  Light slurries (<< 1%)  Moderately corrosive chemicals  Avoid     yewflo Multi-phase fluids High viscosity fluids (i.e... 10 cp. & higher) Extremely corrosive chemicals (i.e... no Stainless or Hastelloy C) High solids content april 1997 YOKOGAWA 28
21. 21. Use & Application  Accuracy  Typical Accuracy specifications Liquids: ± 1% of flow rate Gas / Steam: ± 1.5% of flow rate  Each meter should be wet calibrated prior to shipment  Degradation in accuracy can be caused by... poor installation build up on the shedder bar erosion of the shedder bar changes in the process conditions measuring flow rates less than the stated minimum linear flow rate  Compare to that of present flow metering device (i.e.... differential pressure transmitter and orifice plate) yewflo april 1997 YOKOGAWA 29
22. 22. Use & Application  Rangeability  Fixed by Reynolds number, meter design, and process conditions  Determined by minimum linear and maximum flow rates  Typical rangeability Liquids: up to 20:1. Highly viscous fluids have reduced rangeability Gas / Steam: up to 30:1  May vary slightly by vendor yewflo april 1997 YOKOGAWA 30
23. 23. Use & Application Microprocessor Based Electronics - allows remote communications and self-diagnostics No potentiometers or Switches - eliminate failures caused by corrosion Up-Grade Kits - bring new functionality and reliability to earlier YEWFLO models Surface Mount Electronics - low heat generation and fewer component failures Single Amplifier for all Applications - reduced spare parts requirements yewflo april 1997 YOKOGAWA 31
24. 24. Use & Application      Remote communication via local display interface, handheld interface or DCS Field selectable outputs Multiple displays: rate, % of rate, total One common amplifier for all applications Available with compensation for:  gas expansion  incorrect pipe schedule  accuracy errors down to 5000 Reynolds number    Improved digital filtering Ability to drive an output Real time information on:     yewflo frequency actual velocity span velocity reynolds number april 1997 YOKOGAWA 32
25. 25. Vortex Flow Meter Advantages Digital flow signal No zero drift Pulse output for totalizing Low installed cost Wide rangeability Inherently Linear output Low pressure drop Liquid, steam, or gas applications Immune to density & viscosity changes yewflo april 1997 YOKOGAWA 33
26. 26. YEWFLO Performance Benefits High Accuracy - 1% of rate for liquids and gas 5-Point Linearization Function - dramatically enhances accuracy Mismatched Pipe Correction - adjusts for different diameters between flowmeter and piping Reynolds Number Linearization - increases low end accuracy down to 5000 Reynolds number Automatic Gas Expansion Factor Correction - dramatically improves accuracy Temperature Compensation - eliminates ambient temperature effects on the analogue output Turn Down - as high as 20:1 provides accurate control over wider conditions yewflo april 1997 YOKOGAWA 34
27. 27. Use & Application Piping Requirements yewflo april 1997 YOKOGAWA 35
28. 28. Use & Application Proper piping requirements Liquid Gas    yewflo Position insensitive Full pipe required Good alignment of piping april 1997 YOKOGAWA 36
29. 29. Use & Application P&T compensation yewflo april 1997 YOKOGAWA 37
30. 30. Use & Application Proper gasket selection and installation Gasket     yewflo Correct I.D. required Self Centering (Recommended) Proper material Problems occur if... gasket is too small, gasket is deformed, has shifted position, or if the mating pipe connection is misaligned. april 1997 YOKOGAWA 38
31. 31. 40D Pipe Length Requirements 5D Rosemoun t Rosemount vs. Yokogawa 10D 5D Yokogawa 35D 5D Rosemount 30D 5D Yokogawa yewflo april 1997 YOKOGAWA 46
32. 32. Pipe Length Requirements 5D 15D Rosemoun t Rosemount vs. Yokogawa 10D 5D Yokogaw 5Da 35D Rosemount 10D 5D Yokogawa yewflo april 1997 YOKOGAWA 47
33. 33. YEWFLO’s Unique Sensor Construction •Non-wetted piezoelectric sensor, hermetically sealed •Solid metal shedder bar •No ports to plug •No thin diaphragms to damage •Proven reliability validates 250 year MTBF yewflo april 1997 YOKOGAWA 50
34. 34. YEWFLO Style “E” Signal Adjustment Procedure yewflo april 1997 YOKOGAWA 51
35. 35. Problem Solving The type of problems that can be solved include: Output occurs with no flow Unstable output at low flow High output for a known flow rate High output (beyond programmed span) yewflo april 1997 YOKOGAWA 52
36. 36. Piping Checkout Procedure Make sure there is sufficient straight run upstream and downstream Check for excessive vibration Install appropriate support Remote mount the amplifier Mount the meter so shedder bar is perpendicular to axis of vibration Check the gaskets yewflo april 1997 YOKOGAWA 53
37. 37. Piping Checkout Procedure Be sure wafer style meters are properly aligned When using a remote amplifier, confirm: Interconnecting cable properly terminated Remote housing well grounded Confirm amplifier is correctly connected to the flow tube yewflo april 1997 YOKOGAWA 54
38. 38. YEWFLO’s Unique Sensor Design How Does It Work? Flow Flow hits the shedder bar, separates and due to the shape of the bar forms Crystal A vortices. The vortices create Crystal B an alternating pressure differential across the bar. Force The bar is physically stressed toward the low pressure side of the bar. yewflo H april 1997 A piezoelectric crystal converts a mechanical stress into an electrical pulse. The crystals are hermetically sealed and not in contact with the process. L YOKOGAWA 55
39. 39. Mechanical Pipe Noise With no flow through the meter, any output from the crystals is noise and is caused by ambient vibration around the meter. No Flow Signal Vibration Vibration Vibration Crystal A Crystal B Vibration yewflo april 1997 YOKOGAWA 56
40. 40. YEWFLO Style E Noise Filtering Low Frequency Cut-off Filter High Frequency Cut-off Filter Flow Rate Signal Amplitude Qmax Qmin Trigger Level Adjustment (TLA) Frequency Flow Rate vs. Freq. Amplitude vs. Freq. yewflo april 1997 Noise Judge (Variable TLA) YOKOGAWA 57
41. 41. Noise Balance Adjustment BEFORE NOISE BALANCE Sensor fixing Plate UPPER CRYSTAL LOWER CRYSTAL S1 S1 -S2 -S2 + - + N.B. D/2 FLOW STRESS D D/2 yewflo april 1997 YOKOGAWA 58
42. 42. Noise Balance Adjustment BEFORE NOISE BALANCE Sensor fixing Plate UPPER CRYSTAL LOWER CRYSTAL N1 N1 N2 -N2 A/2 VIBRATION STRESS + - + N.B. A N1 + - A/2 N.B. -N2 AFTER NOISE BALANCE yewflo april 1997 YOKOGAWA 59
43. 43. Noise Balance Adjustment BEFORE NOISE BALANCE Sensor fixing Plate UPPER CRYSTAL LOWER CRYSTAL S1 N1 S1 -S2 -N2 -S2 -N2 A/2 D/2 VIBRATION STRESS + - D/2 + N.B. A FLOW STRESS D N1 S1 + - A/2 N.B. N1 -S2 -N2 SNET AFTER NOISE BALANCE yewflo april 1997 YOKOGAWA 60
44. 44. Noisy “No Flow” Signal Before Noise Balance Trigger Level No Flow Signal 50 Crystal A 0 % Crystal B Signals from Crystal A and Crystal B are added yewflo 100 The resulting signal passes through the Schmitt Trigger. If the amplitude of the signal exceeds the trigger level setting, the output of the circuit is triggered and a square wave with a frequency identical to the noise component exceeding the trigger level is generated. april 1997 The frequency is converted to an analogue value and produces a flow reading when in fact there is no flow through the meter. YOKOGAWA 61
45. 45. Noisy “No Flow” Signal After Noise Balance No Flow Signal Trigger Level 50 Crystal A 0 No Output Crystal B Sum of signals from “A” and “B” now has reduced amplitude. yewflo Amplitude of resulting signal less than that of Trigger Level. Schmitt trigger does not turn on. april 1997 100 % No flow indication. YOKOGAWA 62
46. 46. Noisy “Low Flow” Signal Before Noise Balance Low Flow Signal Trigger Level Crystal A 50 0 Crystal B Signals from Crystal A and B are added. Since the flow and noise components of each are not equal the result is a sine wave whose value is greater than A but less than B and which also contains a large noise component. yewflo 100 % The resulting signal passes through the Schmitt Trigger. Since the amplitude of the noise component exceeds the trigger level, the output of the circuit is triggered and the square wave output contains a frequency identical to the noise component. april 1997 The frequency is converted to an analogue value and produces a “noisy” flow reading. YOKOGAWA 63
47. 47. Noisy “Low Flow” Signal After Noise Balance Low Flow Signal Trigger Level Crystal A 50 0 Crystal B Signals from Crystal A and B are added. Since the noise components are equal but opposite they cancel out. Since the flow components of A & B are not equal the result when added is a clean sine wave whose value is greater than A but less than B. yewflo 100 % The resulting signal passes through the Schmitt Trigger. The output of the circuit is triggered and the square wave output contains a frequency proportional to the flow rate. april 1997 The frequency is converted to an analogue value and produces a stable flow reading. YOKOGAWA 64
48. 48. Noise Balance Adjustment BT200 Display Screen MENU MENU HOME DISPLAY SET 1 SET 2 ADJUST CONTROL TEST SET ADJ G: CHECK DATA H: MAINTENANCE M: MEMO ESC HOME F1 F2 F3 F4 F1 F2 F3 F4 Select H: MAINTENANCE by using the yewflo SET ADJ ESC F1 F2 F3 F4 F1 F2 F3 F4 Ì april 1997 or Ì A: B: C: D: E: F: buttons on the BT200 YOKOGAWA 65
49. 49. Noise Balance Adjustment BT200 Display Screen PARAM PARAM H20: MEASURE TP2 H01: N.BALANCE 1 -5< >10 H02:TLA 0 -1< >2 H03:GAIN 0 -7< >8 DATA DIAG PRNT EXECUTE H21: TP2 (Vp-p) 0.45 H30: REVISION EX 1.10 DATA ESC DIAG PRNT ESC F1 F2 F3 F4 F1 F2 F3 F4 F1 F2 F3 F4 F1 F2 F3 F4 Select Parameter H01 and vary the value to balance the noise component of the output. The effect of the noise balance adjustment can be seen by accessing parameters H20 & H21 and viewing the resulting change in the amplitude. yewflo april 1997 YOKOGAWA 66
50. 50. Noise Balance Adjustment This is basically a null-balance type adjustment; adjustment should be made throughout the range of values to determine the lowest noise setting. Selecting the proper noise balance (N.B.) value will reduce the amplitude of TP2-Com2 to it’s lowest value. Change the N.B. value until output of the meter indicates zero or until TP2-Com2 reading indicates the lowest value yewflo april 1997 YOKOGAWA 67
51. 51. TLA Adjustment If the meter continues to indicate above zero after the noise balance adjustment, the Trigger Level or TLA is used to set the minimum measurable flow or meter threshold. Noise Signal Amplitude Trigger Level The key to eliminating zero flow output is to reduce the amplitude of the signal to a value below that of the trigger level Output Trigger Level By adjusting the Trigger Level above the amplitude of the noise signal the output of the Schmitt trigger never turns on and the meter reads zero. yewflo Noise Signal Amplitude 0% Output 0% When the signal amplitude is below that of the trigger level the output of the Schmitt Trigger does not turn on april 1997 YOKOGAWA 68
52. 52. Trigger Level (TLA) Adjustment PARAM SET H01: N.BALANCE 1 H02: TLA 0 -5< >10 H02:TLA 0 H03:GAIN 0 DATA -1< >2 + 1 -1< >2 -7< >8 DIAG PRNT ESC CLR F1 F2 F3 F4 F1 F2 F3 F4 ESC F1 F2 F3 F4 F1 F2 F3 F4 Access parameter H02 (TLA). Note the set value and increase that value one step at a time until the output is zero. yewflo april 1997 YOKOGAWA 69
53. 53. Low-Cut Flow Rate Adjustment PARAM SET H04: H.F. FILTER H07: L.C. FLOWRATE 26 0 -3< >12 H06: NOISE JUDGE ACTIVE H07: L.C. FLOWRATE 26 E0 GPM DATA DIAG PRNT 30 ESC CLR F1 F2 F3 F4 F1 F2 F3 F4 ESC F1 F2 F3 F4 F1 F2 F3 F4 Access parameter H07. Enter the value of flow at which the meter’s output should drop to zero. yewflo april 1997 YOKOGAWA 70
54. 54. High Frequency Filter Filters out frequencies and eliminates noise such as sonic noise, pump noise or harmonic noise. First determine whether the noise frequency is above your maximum flow requirements: 1. Access parameter G02 (SPAN FREQUENCY) and record this value. 2. Access parameter G01 (FREQUENCY) and record this value. 3. If the G01 value is at least 1.2 times the G02 value, proceed with the high-cut adjustment. If there is less than a 20% difference, continuing with this adjustment may mean that readings in the high end of the flow range may not be possible. yewflo april 1997 YOKOGAWA 71
55. 55. High Frequency Filter Adjustment PARAM SET H04: H.F. FILTER H04: H.F. FILTER 0 0 -3< >12 H06: NOISE JUDGE ACTIVE H07: L.C. FLOWRATE 26 E0 GPM DATA DIAG PRNT 1 ESC CLR F1 F2 F3 F4 F1 F2 F3 F4 ESC F1 F2 F3 F4 F1 F2 F3 F4 Access parameter H04. Increase the set value by one step and observe the output. If the output is now zero, adjustment is complete. If not, continue increasing value until output is zero. yewflo april 1997 YOKOGAWA 72
56. 56. YEWFLO Style E Noise Filtering When is Noise Judge Used? Low Frequency Cut-off Filter Flow Rate Signal Amplitude Qmax High Frequency Cut-off Filter Qmin Trigger Level Adjustment (TLA) yewflo Frequency Flow Rate vs. Freq. Amplitude vs. Freq. april 1997 Noise Judge (Variable TLA) YOKOGAWA 73
57. 57. Noise Judge Adjustment PARAM SET H04: H.F. FILTER H06: NOISE JUDGE NOT ACTIVE 0 -3< >12 H06: NOISE JUDGE NOT ACTIVE H07: L.C. FLOWRATE 26 E0 DIAG PRNT ESC DATA GPM ACTIVE CLR F1 F2 F3 F4 F1 F2 F3 F4 ESC F1 F2 F3 F4 F1 F2 F3 F4 Access parameter H06 and be sure the filter is ACTIVE. yewflo april 1997 YOKOGAWA 74
58. 58. Noise Judge Adjustment PARAM SET B07: DENSITY UNIT B08: MIN DENSITY 8.34 LB/USGAL B08: MIN DENSITY 8.34 B09: TEMP UNIT DEG F DATA DIAG 16.6 PRNT ESC CLR F1 F2 F3 F4 F1 F2 F3 F4 ESC F1 F2 F3 F4 F1 F2 F3 F4 Access parameter B08 and change the value so it is twice the current value. Observe the meter output at various points in the flow range. If the output holds constant or drops out in spite of increasing flow, lower the value by 10%. Continue this procedure until the “flat spot” or drop out disappears. yewflo april 1997 YOKOGAWA 75
59. 59. YEWFLO*E Amplifier Calibration Procedure General Amplifier Check-out 1. Access parameter G02 (SPAN FREQUENCY) and record value. 2. Attached frequency generator to test points TP2 and COM2 and inject the same frequency as read in parameter G02. 3. Access parameter G01 (FREQUENCY) and confirm this value agrees with frequency in Step 2 above to within +/-0.1%. 4. Agreement confirms the general internal operation of the amplifier. A discrepancy indicates a problem which may require amplifier replacement. yewflo april 1997 YOKOGAWA 76
60. 60. YEWFLO*E Amplifier Calibration Procedure Analogue Output Test 1. Perform the amplifier checkout procedure. 2. Inject the frequency as read in parameter G02 and measure the current being produced by the amplifier. The output should be 20 mA, +/-.02 mA. 3. Remove the frequency generator, replace with shorting jumper and measure the output. The output should be 4 mA, +/-.02 mA. 4. A discrepancy in the outputs indicates a potential problem. yewflo april 1997 YOKOGAWA 77
61. 61. YEWFLO*E Amplifier Calibration Procedure Pulse Output Test 1. Perform the amplifier checkout procedure. 2. Connect a frequency counter across the “-” and “P” output terminals on the amplifier. Inject the frequency as read in parameter G02. Check to be sure the frequency counter reads this value to within +/-0.1%. 3. Remove the frequency generator and replace with shorting jumper. Check to be sure the frequency counter reads “0” Hz. 4. A discrepancy in the outputs indicates a potential problem. yewflo april 1997 YOKOGAWA 78