Coriolis Mass Flow Measurement and Calibration in Natural Gas Applications

Emerson's Marc Buttler


In this 27-minute YouTube presentation video, Custody Transfer Measurement and Calibration Round Robin Testing for Natural Gas with Coriolis Meter, Emerson’s Marc Buttler explains Coriolis meter calibration process and Piece Wise Linearization (PWL). His discussion includes Coriolis meter principles of operations, AGA Report No. 11— Measurement of Natural Gas by Coriolis Meter, conversion of mass to gas standard volume, calibration options, and field verification.

In explaining Coriolis principles of operation, Marc notes how mass is measured directly because the vibrating tubs are sensitive to bulk inertial forces of the fluid’s mass. As a mass moves toward or away from the center of rotation inside of a rotating tube, the particles generate inertial forces on the tube. The measurement of this vibration is not affected by changes in fluid properties and velocity profile. Vibration pickup coils measure the sinusoidal waves of the two vibrating tubes. In a no flow condition the two sine waves are in sync with one another.

Flow causes a twisting effect in the tubes, which puts the sine waves out of phase with one another. By measuring this phase shift, the amount of mass flow is calculated. See 4:30 into the video for Marc’s description of how this measurement is performed.

For natural gas metering applications, a Micro Motion Coriolis meter with Tall Tube Geometry is recommended, since the mass of gas is so much less than liquid and longer tubes are required to get the Coriolis effect and the level of accuracy required for custody transfer applications. These applications require highly accurate measurements since custody transfer involves the change in ownership of the natural gas.

He referenced the 2nd edition of the AGA Report No. 11 which tightened measurement performance requirements from +/- 1.0% to +/- 0.7%. Diagnostic verifications were required to guide the users on when flow tests were needed to recalibrate and this calibration could be performed in the field.

To convert mass flow measurements to standard volume measurements, one doesn’t need to know pressure and temperature, like traditional volume flow measurements, but the density of the natural gas.

Watch Marc’s presentation for more on the calibration process and the opportunity for Piece-Wise (stepwise) Linearization for adjustments across the range of flow measurements.

Learn more about Coriolis flow measurement in the Micro Motion area of Emerson.com and connect and interact with other flow and oil & gas experts in the Flow and Oil & Gas groups in the Emerson Exchange 365 community.

Posted Wednesday, May 9th, 2018 under Flow, Oil & Gas.

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