5/12/2020
Velocity Type: Ultrasonic Flowmeter
Overview
• Principle of Operation
– Use transmitted sound waves to determine the flow
rate [using Doppler and Transit Time techniques]
• Typical accuracy of 1 to 5% for microprocessor-
based units
– Better than 0.5% for precision units (I.e. Daniel
SeniorSonic)
• Rangeability of 20 to 50:1
• Measures liquids and gases with different
designs
D I C E T Flow Measurement
Ultrasonic Flowmeter
Transmitter and receiver
Acoustic Beam Acoustic Beam
Flow Profile
Clamp-On Wetted
Type Type
Doppler Effect Time of Flight
Flow Profile
D I C E T Flow Measurement
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Ultrasonic Flowmeter
• uses sound waves to determine flow rates of
fluids.
– Doppler Effect Method
• One of the 2 transducer mounted in the same case on one side
of the pipe transmits sound waves (constant frequency) into the
fluid. Solids or bubbles within the fluid reflect the sound back to
the receiver element. Frequency difference is directly
proportional to the flow velocity in the pipe.
D I C E T Flow Measurement
Principle of Doppler-effect ultrasonic
flowmeter with separated opposite-
side dual transducers
D I C E T Flow Measurement
5/12/2020
Ultrasonic Flowmeters
Principle of Operation
Doppler
Flowmeter
D I C E T Flow Measurement
Configurations of Doppler-effect ultrasonic
flowmeter. (a) Single transducer. (b) Tandem
dual transducer. (c) Separate dual transducers
installed on same side of pipe
D I C E T Flow Measurement
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Ultrasonic Flowmeter
Doppler meters measure the frequency shifts caused by liquid
flow. The frequency shift is proportional to the liquid’s
velocity.
D I C E T Flow Measurement
Ultrasonic Flowmeter
D I C E T Flow Measurement
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Ultrasonic Flowmeter
D I C E T Flow Measurement
Clamp-on Ultrasonic Flow Meter
(Courtesy: Endress+Hauser)
D I C E T Flow Measurement
5/12/2020
D I C E T Flow Measurement
Ultrasonic Flowmeter
• uses sound waves to determine flow rates of
fluids.
– Transit-Time Method
• 2 piezoelectric transducers mounted opposing, to focus sound
waves between them at 45° angle to the direction of flow within a
pipe. In a simultaneous measurement in the opposite direction to
fluid flow, a value (determined electronically) is linearly
proportional to the flow rate.
Transmitter
Upstream Transducer Receiver
FLOW
D I C E T Downstream Transducer Flow Measurement
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Principle of transit-time ultrasonic flowmeter, clamp-on
type. Transducers alternately transmit and receive
bursts of ultrasonic energy
D I C E T Flow Measurement
Ultrasonic Flowmeters
Principle of Operation
Transit-Time
Flowmeter
D I C E T Flow Measurement
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The operation is illustrated by the following
equations:
D I C E T Flow Measurement
D I C E T Flow Measurement
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D I C E T Flow Measurement
Ultrasonic Flowmeters
Performance Considerations
Reynolds number constraints
Entrained gas or particles for doppler
Clean liquids for time of flight
Installed without process shut down
Straight upstream piping requirements
D I C E T Flow Measurement
5/12/2020
Ultrasonic Flowmeter
Multi-path Ultrasonic
D I C E T Flow Measurement
D I C E T Flow Measurement
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Ultrasonic Flowmeter
Daniel Ultrasonic (Senior)
D I C E T Flow Measurement
D I C E T Flow Measurement
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D I C E T Flow Measurement
D I C E T Flow Measurement
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Ultrasonic Flowmeter
Transit Time Flowmeter
(Courtesy, Controlotron Corp.)
D I C E T Flow Measurement
D I C E T Flow Measurement
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D I C E T Flow Measurement
Ultrasonic Flowmeter
Common Applications
– Liquids and some gas applications
– Doppler flowmeters require entrained gas or
particles to reflect ultrasonic energy
– Where non-wetted sensors are applicable
– Existing installations where pipe modifications
are difficult or uneconomical
– Where exotic materials make other flowmeters
uneconomical
– Large pipes where in-line meters are
uneconomical
– Temporary installations
D I C E T Flow Measurement
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Ultrasonic Flowmeter
Benefits/Advantages
– Some designs allow measurements to be
made external to the pipe
• utilize no wetted parts
– Little maintenance required
– Pipe piggable without meter removal
– Newer multi-path microprocessor-based
spool designs are achieving good gas results.
AGA 9 issued in ‘98
D I C E T Flow Measurement
Ultrasonic Flowmeter
Limitations/Disadvantages
– Fluid changes affect measurement
– Proper installation is critical
– Long upstream/downstream straight piping
requirements
– Minimum Reynolds number constraint
– Only mixed success has been achieved thus far in
industrial flow applications
– 4-wire operation
D I C E T Flow Measurement
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Ultrasonic Flowmeter
Advantages: Disadvantages:
• Non-intrusive, • Maximum temperature 150°C
obstructionless • Particular fluid conditions are
• Wide rangeability (10:1) required (TOF-type: clean liquids;
• Easy to install (especially Doppler-type: particles or
for clamp-on version)
impurities in the stream)
• Cost virtually independent
of pipe size • Not very high accuracy (about
• The flow measurement is ±2%)
bi-directional • Doppler flowmeter clamp-on
type requires a pipe of
homogeneous material (cement
or fibreglass linings must be
avoided)
D I C E T Flow Measurement
Ultrasonic Flowmeter
ADVANTAGES
•No Moving Parts
•Unobstructed Flow Passage
•Wide Rangeability
V
DISADVANTAGES
•For Liquids Only (limited
gas)
•Flow Profile Dependent
•Errors Due To Deposits
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D I C E T Flow Measurement
D I C E T Flow Measurement
