Differences in the measured volume of two Ultrasonic flow meters installed approx. ~ 2 KM aparts. 1

[ArsalanKhan]

Dear forum members,

Hope you guys are doing well.
I have a query. At our metering station, a 10" NG USM is installed for volume measurement. At the downstream of our metering station, approximately after 2 KM of 14" underground pipeline, another 8" NG USM is installed at receiving station. There are differences in the meter reading of both USM, in range of approximately 1% to 8%.

As per my limited knowledge, this difference is due to the fact that the meters are far apart, which introduce some lag. Please correct me if I am wrong. I am seeking the reason behind this difference, please respond if you know it.

Your responses shall be highly appreciated.

Regards,

 

[3DDave]

Are they temperature and density/pressure compensated meters?

 

[ArsalanKhan]

If I am understanding your question correctly, you are taking about Pressure and temperature compensation, to compensate the difference in pressure and temperature at the time of calibration and site conditions. We are not using the Pressure and Temperature compensation in our meter.

 

[IRstuff]

We are not using the Pressure and Temperature compensation in our meter.

So, how can you possibly expect the meters to read the same?

TTFN (ta ta for now)
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[hacksaw]

Manual correction is the "traditional" method. Any flow meter manual, or supplier manual will show you how.

You'll need the P,T 20-30 pipe diameters upstream, adjacent to the meter location, and the fluid properties.
Check the meter calculation sheet used by the supplier, for a start.

 

[ArsalanKhan]

Can you please share the manual calculation pdf? I have checked the OEM manual couldn't found thus correction.

 

[hacksaw]

Show the manufacture's name and the device model number, together with the fluid properties, including pressure and temperature, and approximate fluid velocity.

Most ultrasonic meters used for precise measurements include the corrections you are seeking.

 

[georgeverghese]

Ultrasonic meters dont do well when there are liquid droplets or mists in the gas. Or worse, if there is a discrete liquid phase caused by high hydrocarbon or high water dewpoint. Scrubbers and separators fitted with wiremesh demisters or vane packs in NGL extraction plants with shallow dewpoint depression may permit liquid mist carryover into the product gas stream also.

 

[hacksaw]

Yes, and in some pipeline, 10 m/s slugging events can occur routinely.