Calibrating Coriolis Flowmeters In-Situ

Control Engineering Asia magazineEmerson’s Jonas Berge added a comment to a post, Mass Flow Measurement for Fuel Gases. In his comment, he pointed to a Control Engineering Asia article, Time for Calibration?, that he had written a couple years ago. In the article, Jonas explains how advanced diagnostics technology can help determine if a Coriolis flowmeter needs to be removed from the process or if it can wait.

Jonas opened with a great description of Coriolis measurement theory of operation:

A Coriolis flowmeter sensor consists of one or two tubes through which the fluid flows. A control circuit drives electric coils applying an oscillating force to the tubes moving them from side to side maintaining amplitude at its resonant frequency. As fluid passes through the tubes, they twist slightly due to the Coriolis effect. The amount of tube deflection is directly proportional to the mass flow and is registered as a phase shift from which the mass flow is calculated.

He notes that this Coriolis effect can also be used to measure density, that it can measure gases and liquids, and measurements are:

…largely unaffected by changes in temperature, pressure, density, viscosity, and flow profile. They also have high accuracy and repeatability.

If abrasive or corrosive fluids are being measured, the walls inside the Coriolis flowmeter sensor can thin, causing a change in stiffness. This process can cause the sensor’s calibration to drift. Jonas noted issues with calibration:

…too frequently is costly, is time consuming, and disrupts the production process. But if calibrating is not done often enough, product quality can be negatively impacted.

He highlighted the optimum solution:

…in-situ meter verification, a form of diagnostics by which the complete performance of a Coriolis flowmeter is verified. Electronics determine whether a Coriolis flowmeter has experienced a change in stiffness due to corrosion, erosion, or deformation.

…measured stiffness is compared to the original stiffness when the Coriolis flowmeter left the factory to determine if the structure of the sensor tubes has changed or been damaged in any way. Multiple test frequencies are used to keep the diagnostics independent of density and flow and thus can be performed on any process fluid; it need not be the same fluid as in the factory benchmarking.

This Micro Motion smart meter verification is embedded in the Coriolis flowmeter. This in-situ verification can be done remotely due to digital communications protocols such as HART, Foundation fieldbus, and WirelessHART along with electronic device description language (EDDL – IEC 61804-3). Jonas described how it works:

…EDDL wizards created by the flowmeter manufacturer guide the technician step-by-step; no specialized training is required to perform meter verification. Percent completion is displayed throughout the process so technicians know how much longer they need to wait.

The meter verification wizard makes this a simple pass or fail test, it does not present incomprehensible numerical values or charts that need interpretation, but rather offers actionable information.

In addition to verification, Jonas described abnormal situations that could be detected:

…advanced Coriolis flowmeters now have diagnostics that can detect and report bubble or slug flow to both operators and maintenance technicians directly at their workstations.

Give the article a read if you are using or looking into using Coriolis flow and density measurement in your process.

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16 comments

  1. What is Emerson’s statement of proof test coverage (e.g. for SIS testing) for the in-situ tests described in this article? I would apprreciate an e-mail with the answer to bmostia@sis-tech.com.
    Thanks
    William (Bill) L. Mostia, Jr. PE

  2. bita kazemian says:

    Mr. Cahill
    thanks for clear description of Coriolis meter.
    before we bought a Coriolis mass flow meter for ethane gas but we want to use this for other gas fluid , is it possible or not ?

    by other word , the Coriolis mass is just fabricated for a fluid we requested or not?
    thank you

  3. Nasreldin Galy says:

    We have two ultrasonic Flow meter UFC3000 measuring Diesel fuel to / from large Storage tank ..we in doubt whether those flow meters needs calibration or not ..what should we do to decide this matter model UFC 3000 F…EEx & UFC 030 F/..EEX ..Thanks ..Engineer Nasreldin Galy .. Dubai U.A.E FEWA Federal Electricity & Water Authority Dubai

  4. Dear Sir

    Need a “Mass Flow Meter” Calibration procedure. Could you send

    Best Regards

    Recai COŞKUN

  5. Jim Cahill says:

    Thanks for your request, Recai. I’ve sent a note to one of my colleagues who manage the Micro Motion brand to see what we might have to send you. You can also connect with the team via email at: flow.support@emerson.com

  6. Jim Cahill says:

    Recai, Here’s the feedback I received, “Calibration is only available through a licensed Emerson Service Center. Please contact your local office to find out about service options at: http://www2.emersonprocess.com/en-US/brands/micromotion/about-micromotion/Pages/Contact.aspx

  7. M. Farid says:

    Hi Jim,
    What coriolis transmitter output is recommended for LPG custody transfer application? is it pulse or analog? Could you advise the reason?
    Is there any difference in meter uncertainty for using analog i/o pulse output?
    If the distance between transmitter and flow computer is more than 500 meter, will it create problem for pulse?
    Thanks a lot.
    Farid

    • Jim Cahill says:

      Hi Farid, Thanks for your questions! Let me check with some of my colleagues and have them connect back with you.

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