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Question related to Model 1700 & 2700

Respected Sir,

We are using Model 1700 & 2700 for CNG gas measurement in Gas Dispenser/Compressor outlet. We are measuring Mass unit. 

our internal committee has raised question that "if heavy hydrocarbon gas or lean gas passes through Mass flow meter", will accuracy of MFM will affect or not?

What are the parameters need to be taken care while measuring mass through MFM?

Is there any requirement to change parameters on daily basis for better accuracy?

If I will get answer of such question it will help me a lot.

Thanks 

6 Replies

  • Please mention size and Model and make of the MFM. It is good to mention process flow range, line pressure and fluid properties (sp. gravity etc.). We know that it is CNG, however these details will help in answering accuracy related question. Thanks
  • In general, all of Emerson's Micro Motion Coriolis meters, including those with the 1700 and 2700 transmitters can measure gas (including CNG) in Mass units on an ongoing basis with no need to make any adjustments, even if the gas composition changes. However, this is only true for Mass units.

    If you want to indicate in units of Standard Volume, then you need to update the Base Density when it changes. The Base Density is the density at reference pressure and reference temperature, so it will only change if the composition of the gas changes. The Mass units are measured directly by the meter, so the composition has no affect on the meter accuracy in Mass units when using a Micro Motion Coriolis meter, but the Standard Volume is calculated from the Mass value AND the Base Density, so the Base Density value must be kept up to date if the composition changes.
  • In reply to Marc Buttler:

    Marc,
    Very clear answer !!!

    Major Chu

  • In reply to Marc Buttler:

    Sir,
    Thanks for your guidance
    I have couple of questions in mind that

    Q. 1. if we put 2 same (CNG050) MFM in series, will it gives same accuracy level or it will be different from one another.

    As per OIML meter alone +/-1% and whole system +/-1.5% error can be reported. is it true?

    Q.2. How to check accuracy level of MFM which measure Mass as unit is there any method to measure accuracy level.

    Q.3. what happened if oil or debris passes through MFM/Coriolis meters, will it affect accuracy?

    Regards
    Ghanshyam
  • In reply to Ghanshyam Valand:

    A.1. The two meters both have uncertainty, so they may not match exactly. However, they should always agree within the root-sum-square of their individual uncertainties.
    The OIML uncertainty for the meter alone is 1%, so RMS is SQRT(1^2 +1^2) = SQRT (2) = 1.414% Two meters in the same system should always agree within 1.414% unless there are other sources of uncertainty in the system that are not expected.
    A.2. I know two methods: a mass flow master meter or a cylinder on a weigh scale. For more details I can provide additional documentation. Send me an email address if you want more information on either of these methods.
    A.3. Oil or debris will not damage the CNG050 and the accuracy will not be harmed.
  • In reply to Marc Buttler:

    Thanks for reply
    my email id is : ghanshyamg.valand@adani.com

    Sir, we are measuring accuracy of MFM with Prover (which is calibrated with "FCRI, India"). We calibrate MFM by putting prover in series and taking 10 readings of vehicle filling and measure accuracy. If MFM accuracy in not as per requirement technical team change "Mass Factor" to appropriate level and match accuracy with Prover.

    We are not using weigh scale method to check accuracy level of MFM as government authority check with Prover only.

    Regards,
    Ghanshyam Valand