Vortex Flow Meters

[Hamilcar]

Dear Engineers

Recently I read an article about flow metering, which stated the following:

1) 'Coriolis meters are not recommended for wet gas application' <<is this because it is dependent on the density of the gas and composition, hence fluctuating water content can affect the readings?

2) 'Vortex meters have the least problems with wet gas compared to other measuring principles, and only measure the gas component in wet gas application' <<< how is a vortex meter reading not effected by the water content in wet gas applications?

Any relavent information would be welcome

Regards

 

[dcasto]

First of all measureing multiphase is next to impossible, but the coriolis comes closest. Your comment is wrong, the coriolis meter doesn't care about density (other than physical constraints of velocity and presure drop).

Your statement on vortex meters must be from a vendor as no data supports this conclusion see:

http://www.ceesi.com/pubs/1006_GasMeterTechnologies.pdf

The quest for an (industry acceptable) two phase meter shall continue......

 

[JLSeagull]

The mass of any condensate is higher than gas and increased mass flow due to the liquid slug would be measured with the Coriolis flow meter.

 

[zdas04]

I think the whole article was written by a vendor of vortex meters. The first one I ran wasn't even compensated for pressure and tended to give +/-60% kind of values. They've gotten better, but they're still a long way from "having the least problems ...".

My preference for rapidly changing, slugging fluids is the V-Cone meter. It doesn't do all that much better job on slugging flows than the mass flow meters, but it seems to recover faster from a slug.

David

 

[quark]

This is a bit funny but I think the article mentioned by OP might be referring to the final read out in volumetric terms.

Assuming the temperature and pressure of the gas constant in both cases, higher moisture content in a gas flow should cause the Coriolis to read higher volumetric flowrate than a denstiy compensated Vortex. However, I don't know what is the use of that.

 

[Hamilcar]

Thanks all for the info.

I obtained that info from the Canadian process Equipment & Control news website, here is the link:

http://www.cpecn.com/onlineExclusiveViewer.php?onlineExclusiveKeyword=GasMeter&PHPSES

Yes I looked at V-Cone meters, in perticular the Roxar wet gas and the MRM V-Cone. The Roxar one claims to use microwave technology to measure the water content, the condensate is estimated by a ratio input. I am told they can handle wet gas applications and the sales engineer claims a slug will not effect the instrument.

I have looked at Coriolis meters too, but there is none suited for pipe sizes >6". There are some companies working on larger 12" ones, but these are still on the drawing board. I have noted some use the coriolis in parallel to cater for larger pipe sizes, but so far no vendors seem to recommend them for a 24" line with wet gas.

 

[dcasto]

So, what do you do downstream of the meter with big ol' slugs? I can not imagine your process just chugs along ingesting slugs happily. If you have that much liquid, separate the gas and liquid before measurement.

The coriolis meter measures mass and only mass. In the electronics it can take the input signal and perform time based calculations to arrive at an average stream density. It can then use that desity to get a volumetric flow (at flowing conditions). You still need to perform calculations to get back to standard conditions and thats where the rub comes from because to adjust back to standard, you need to know the composition.

 

[Hamilcar]

Well there is a slug catcher downstream, before the gas enters the process. Gas use to be separated from the liquid upstream at remote platforms but these were removed for economical reasons, just as they were successfully done at alot of offshore platforms in the North Sea.

 

[Hamilcar]

Should probable mention that metering cannot be done downstream of the slugcather, as the remote platforms feed into the same slug cather, and metering if required for each platform.

The Liquids content is <0.5%, this can be handled by some meters in the market but they do not meet the straight length requirement, pipe size and/or low pressure operation requirement (<15bara)
The V-Cone is the only one i have seen that meets all of these, but I was just curious as to what i had read in regard to vortex and coriolis meters.

 

[JLSeagull]

The Coriolis meter can only measure liquid density. The mass of the tubes is too great to provide density for gas applications.

Although somewhat different than the V-Cone, a few other head type flow meters like the Fluidic Techniques FlowPak also limit the straight run requirements. The head during a slug is likely outside the normal range. However modern dp transmitters are generally unaffected by actual dp well beyond their calibrated range.

 

[dcasto]

JLSeagull, not true, coriolis meters will measure gas densities, the problem is theie limits are velocities and mass rates. With gas, velocicities that cause more than a 10 or 20 psi drop create vibrations that the system cannot sorrt out from the vibrations induced on the meter to measure the forces. There is one company working on useing the coriolis meter to mass measure methane fuel to get better air fuel ratio control on large engines.

 

[JLSeagull]

I may have been wrong before sometime too.