1. SONARtrac® vs Ultrasonic Flowmeters
5/25/2018
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2. SONARtrac vs Ultrasonic Flowmeters Primary Differentiators
CiDRA SONARtrac Flowmeter
Ultrasonic
Flowmeter
Representative measurement
Full bore measurement
Measurement only from information along ultrasonic path
Capable of measuring slurries
yes
limited
Reliable measurement in presence of scale build-up
Accurate velocity measurement no
Works in presence of entrained air bubbles
Doppler: Low levels only
Transit Time: No
Can measure level of entrained air
Works on lined pipes (rubber, teflon, etc)
maybe
Works on fiberglass pipes
Requires coupling gel
Sensors require special alignment
Maintenance requirements
none
No drift mechanism
Does not wear out
periodic
Requires reapplication of ultrasonic gel (couplant)
Requires periodic re-calibration
Life cycle cost
lowest
medium
5/25/2018
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3. General Issues with Ultrasonic Flowmeters Doppler and Transit Time Ultrasonic Meters
Ultrasonic Transducer
Pipe Wall
Scattering Losses
Signal is Attenuated or May be Lost to Transducer Entirely
Refraction Angle Change
Attenuation through
liner or interfaces
Require good acoustic conduction through pipe wall and liners.
Will not work well for pipes with cemented lining.
Will have problems with fiberglass pipes
Ultrasonic Transducer
Liner
Attenuation in the liner or interfaces
Attenuation of Signal and Change in Beam Angle
Change in Beam Angle Generates Loss in Accuracy
Drying out of gel will cause loss of signal
5/25/2018
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4. Doppler Ultrasonic Flowmeters
Primary problems with operation:
Scale causes attenuation and refraction of the signal.
Continuous maintenance because the gel/couplant dries.
Low accuracy (+/- 20% unless calibrated on the pipe, but accuracy cannot be maintained)
Measurement is proportional to the cosine of the beam angle into the flowing material; as that is a small angle, even tiny changes of that angle (due to gel, contact, scale etc…) cause a big error in the measurement.
Measurement made using reflections, rather than measuring through the pipe so majority of the information gathered from volume is close to the pipe wall, making it sensitive to flow velocity profile and variations.
Additional problems:
Does not work with pure liquids. Requires solids/bubbles.
Requires minimum % of solids (~5%)
Requires minimum particle size (~ >100 um)
Not accurate in presence of high concentration of solids
Affected by bubbles (bubble velocity in vertical pipes is different than flow velocity, which causes attenuation of the signal and inaccurate measurement)
5/25/2018
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5. Doppler Ultrasonic Flowmeters Impact of Scale Build-up and Solids/Bubbles
Ultrasonic Transducer
Refraction of Ultrasonic Waves
Low Levels of Solids/Bubbles: Normal Operation
Ultrasonic Transducer
Scale
Attenuation in the Scale
Attenuation of Signal and Change in Beam Angle
Change in Beam Angle Generates Loss in Accuracy
Scale Buildup:
Loss of accuracy and eventual loss of signal
High Levels of Solids/Bubbles:
Loss of signal due to excessive amount of bubbles/solid particles
Ultrasonic Transducer
Liquid with Excessive Bubbles or Solid Particles
Loss of Signal Resulting in Loss of Measurement
5/25/2018
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6. Doppler Ultrasonic Flowmeters Accuracy Issues on Horizontal Lines
Ultrasonic Transducer
Refraction of Ultrasonic Waves
Accuracy dependent on knowing the precise angle of ultrasonic beam
The angle changes at every interface.
Unknowns in the acoustic velocity of the liner and the slurry contribute to errors in the measurement.
If the transducers are not perfectly aligned, errors in the angle will also occur and cause measurement errors.
5/25/2018
All Rights Reserved. Copyright CiDRA 2015

7. Doppler Ultrasonic Flowmeters Accuracy Issues on Horizontal Lines
Ultrasonic Transducer
Air bubbles will rise faster than the slurry.
Doppler meters will tend to track bubbles over solids. This will cause the meter to over read the flow.
5/25/2018
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8. Transit-Time Ultrasonic Flowmeters
Primary problems with operation:
Scale causes attenuation and refraction of the signal.
Continuous maintenance because the gel/couplant dries.
Accuracy is +/- 5% unless calibrated on the pipe.
No measurement if the flow has more than 10% solids/bubbles.
Additional problems:
Developed to work with only pure liquids.
High concentration of solids is a problem.
Measurement affected by any presence of bubbles (less than 10%), which causes attenuation of signal and measurement failure.
Transit-Time Ultrasonic flow meters are not recommended for slurry applications, which is known to have more than 10% of solid/bubble content.
5/25/2018
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9. Transit Time Ultrasonic Flowmeters Impact of Scale Build-up and Solids/Bubbles
Ultrasonic Transducer
Refraction of Ultrasonic Waves
Reflection
Clear Fluids: Normal Operation
Ultrasonic Transducer
Pipe Wall
Scale
Attenuation through Scale
Scattering Losses
Signal is Attenuated or May be Lost to Transducer Entirely
Refraction Angle Change
Scale Buildup:
Loss of accuracy and eventual loss of signal
Pipe Wall
Ultrasonic Transducer
Liquid with Air Bubbles or Solid Particles
Large Amount
of Attenuation
Loss of Signal from Attenuation Results in Loss of Measurement
Bubbles and Solids:
Loss of signal
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10. SONARtrac vs Ultrasonic Flowmeter Benefit Summary
Representative Measurement:
SONARtrac meters use the entire pipe volume.
Ultrasonic meters only use the information along ultrasonic path, making it highly sensitive to particles or other acoustic impedance mismatches.
Reliability:
SONARtrac meters do not lose velocity measurement in presence of scale.
Ultrasonic meters lose accuracy in presence of scale.
Entrained Air:
The entrained air measurement feature of the SONARtrac can be used to correct both density and flow.
Ultrasonic flow meters cannot measure entrained air, and their accuracy can be affected by the presence of air bubbles.
5/25/2018
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11. SONARtrac vs Ultrasonic Flowmeter Benefit Summary
Maintenance:
SONARtrac meters require little to no maintenance.
Ultrasonic meters require reapplication of gels/couplants.
 Operation:
SONARtrac meters measure in presence of solids/bubbles.
Ultrasonics have a very limited range of operation with solids/bubbles.
5/25/2018
All Rights Reserved. Copyright CiDRA 2015