Ultrasonic Flowmeters for Gas | Velocity Type Flow Meter Part II
We discuss the advantages and disadvantages of ultrasonic flowmeters in part two of this gas flow meter series on velocity flow meters. Three velocity type meters measure natural gas: turbine meters, ultrasonic meters, and vortex meters.
Ultrasonic Gas Flow Meters
Ultrasonic flow meters are one of the new gas technologies and are approved for custody transfer. Inline ultrasonic meters are highly accurate (0.05-0.2%) and compete with differential pressure (DP) and turbine flow meters. When used as a custody transfer meter, the ultrasonic must have at least three paths.
Clamp-on ultrasonic models are not approved in the U.S. for custody transfer at this time. They are nonintrusive as the transmitters clamp to the outside of the pipe. However, they are less accurate (about 1%) than the inline meter and used for monitoring, check metering, temporary flow measurement, and leak detection.
Ultrasonic flow meters are approved for custody transfer and perform well in large pipe sizes. Most Coriolis meters serve two inches or smaller pipe sizes, becoming expensive and unmanageable in larger line sizes. In most cases, ultrasonic meters are the better choice for 6″ pipes and larger over Coriolis.
Ultrasonic flow meters can measure the flow of nonconductive liquids, gases, and steam, something magnetic meters have limitations with. Given that oil and gas production, transportation, and refining industries fluids are nonconductive, the ultrasonic flowmeter excels in that market.
As a rule, the ultrasonic meters are highly accurate, repeatable, and tolerate extreme temperatures. They offer high rangeability and can measure in low- and high-flow conditions. They provide long-term reliability, and because they have no moving parts, they require little maintenance. In addition, they are self-diagnosing, and once calibrated, they can determine measurement shifts. The clamp-on models also offer flexibility and easy installation without penetrating the pipe.
Of course, ultrasonic meters have high initial costs. While dirty gas will degrade accuracy, Ultrasonic flowmeters handle impurities better than turbine meters. Additionally, sound, even noise outside of human perception, can interfere with the sonic pulses.
Manufacturers of Ultrasonic Flowmeters
Some manufacturers of ultrasonic flow meters include:
- Emerson Daniel
- Elster Honeywell
- FMC Technologies
If you are in the market for an ultrasonic flow meter, submit your inquiry here.
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