Ultrasonic Flowmeters: a Technology Whose Time Has Come

Introductionmeasurement. Flow speed is not uniform throughout
One of the most surprising developments inthe flow path. By calculating the flow rate at more
flowmeter technology in the past few years hasthan one location in the flow stream, multipath
been the rapid growth in ultrasonic flowmeters. Moreultrasonic flowmeters can achieve flow measurement
and more users are recognizing the benefits of theaccuracies as high as 0.5 percent or 0.25 percent.
nonintrusive technology that ultrasonic flowmetersSome natural gas production companies use ultrasonic
offer.flowmeters to measure natural gas as it is
Ultrasonic Flowmeter Technologytransferred to natural gas transmission companies.
Ultrasonic flowmeters utilize two differentTransmission companies also use ultrasonic
technologies: Transit time and Doppler. Both areflowmeters to measure natural gas being delivered to
primarily used for closed pipe applications. Transit timeutilities that sell natural gas to business and residential
ultrasonic flowmeters have two transducers thatcustomers. Ultrasonic flowmeters are often selected
send two acoustic signals from one side of the pipefor new metering stations being built. Users report
to the other. One transducer is a sending transducerthat, despite the higher initial cost of ultrasonic gas
and the other is a receiving transducer.flowmeters, they can save substantial amounts of
Transit time flowmeters are mainly used on cleanmoney over orifice plate installations by selecting
liquids. For dirty liquids, e.g., liquids containing particlesultrasonic meters. In some cases, users who have
or bubbles, Doppler ultrasonic flowmeters are used.tried out ultrasonic flowmeters for natural gas
Doppler flowmeters also have two transducers thatmeasurement are also replacing orifice plate and
act as sender and receiver, and they use an acousticturbine meters with ultrasonic flowmeters.
signal to determine flow rate. Instead of bouncing theA Geographic Perspective
signal off the other side of the pipe, however,While ultrasonic flowmeters are used widely in the
Doppler flowmeters reflect the signal off the particlesUnited States and in Europe, there is a difference in
in the flow stream. As the acoustic signals arestyle between the US companies and the European
reflected off the particles, a frequency shift in thecompanies. Clamp-on ultrasonic flowmeters have
signals is created. This frequency shift is proportionalhistorically been more successful in the United States
to flow rate. The ultrasonic flowmeter uses thisthan spoolpiece meters. Controlotron, located in
frequency shift to calculate flow rate.Hauppauge, New York, was the first company to
Natural Gas Applicationsintroduce clamp-on ultrasonic flowmeters for
For natural gas applications, the primary technologicalcommercial applications in 1972.Spoolpiece meters
breakthrough responsible for increased use ofhave historically received better acceptance in Europe
ultrasonic flowmeters is the development of multipaththan in the US, and European suppliers such as
transit time flowmeters. Single path transit timeKrohne are emphasizing spoolpiece meters in their
flowmeters determine flow rate by using a singleresearch and development efforts. Siemens’
ultrasonic beam or path to calculate the flow rate.introduction of their Sitrans F spoolpiece meter at the
Multipath ultrasonic flowmeters use two or more1997 Achema show is very much in the European
paths, thereby achieving a more accuratetradition.