Relationship between GPM(Liquid) and SCFH(gases) 1

[chicopee]

A product catalog details a table of liquid flow rates GPM's and gas flow rates in SCFH's for excess flow check valves. Is a relationship available that relates GPM and SCFH for different liquified products?

 

[SNORGY]

You could derive such a table, but it's not as straightforward as your question - as worded - appears to be hoping. These things depend on densities, viscosities, coefficients of discharge, compressibility, and a host of other component-specific data. Good resources would be a Control Valve Handbook and Crane Technical Paper 410 / 410M. With those two references, you could derive relations that get you in the ball park.

I assume you are not concerned with flow undergoing a phase change through the component. It would get much more involved for multiphase or flashing flow.

Regards,

SNORGY.

 

[IRstuff]

Wouldn't it be related through the molar mass, i.e,

GPM*density/molar_mass = moles/time

and then whatever conversion gets you from liters/mole/time to SCFM?

TTFN

FAQ731-376

 

[SNORGY]

Could be. But as a dummy "Mechanical" type, I try to avoid moles. Mainly because I keep catching them in my garden eating my avogadros.

Regards,

SNORGY.

 

[zdas04]

No. You cannot do this. SCF is a statement of the imaginary volume of gas at an arbitrary set of standard conditions--the term SCF is not defined for any liquid products. If you want to develop a gpm to ft^3/hr graph for a given liquid, it is easy and linear.

To develop a gas capacity of a check valve, you have to be working in mass flow terms or in volumes at actual conditions, not "standard" mythology. I can get a LOT more SCF's of Helium through a check valve in an hour at 1,000 psig than I can get of CO2 at 0 psig. The capacity of the valve is a function of things like fluid velocity, acceptable dP, fluid properties, etc.--none of which are available in an SCF evaluation.

David

 

[BigInch]

Crude oil and refined products are always custody transferred at a standard defined by the custody transfer contract. Great pains are taken to ensure accuracy by calibrating the flowmeters by running a prover loops at the beginning of every shift, significant change in pressure or temperature, significant change in ambient temperature and on every change of product.

In fact the same standard volumetric error in a gasoline measurement would be 126 times more significant than the same error in a natural gas measurement, if you consider paying for BTU content in a standard volumetric unit of each. Nobody likes getting paid less than they deserve, or more than they should for these high volumes, so great care is taken in standardizing each gallon to the exact standard condition as specified in the sales contract. Liquid prover loops used at a tanker loading terminal can cost millions of dollars. When you realize that only a 1/2 % error in loading a supertanker can mean a fight over 1 million dollars, you get some idea why a proof of exact liquid quantities becomes important. At some crude import/export terminals that error could easily mean
2 Billion dollars a year (even at today's low price)

Prover Loops,

http://info.smithmeter.com/literature/docs/liquid flow provers.pdf

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[BigInch]

To answer your question, yes. Liquid standard volume calculations are based on their expansion with temperature, although they do change volume with pressure, that's a very, very small coefficient. Standard pressure is 0 psig.

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[chicopee]

I believe that I have located a reference material that may answer my original post. If any one is interested check out the Warren Controls VSSTR-905 "valve sizing and selection technical reference" .PDF file under

http://www.warrencontrols.com.

 

[BigInch]

I don't see the answer to the question I thought you asked above, unless you mean the tiny reference to the liquid's specific gravity at 60F. But if you're happy, I'm happy.

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"Being GREEN isn't easy" ..Kermit

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[chicopee]

I'll do some reverse engineering and I'll calculcate the Cv's for liquid and vapor phase for a particular fluid using the same reverse back flow valve.

 

[BigInch]

Rereading your question, perhaps you are needing the relationship that takes into consideration the specific gravity and the viscosities of different liquids, yes? I wouldn't call that a relationship between gpm and SCFH.



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"Being GREEN isn't easy" ..Kermit

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[BigInch]

Liquid Flowrate Corrected for SG and [ν]

Q = Fv * Cv*([Δ]P/SG)^0.5

Q Flowrate through the valve gpm
[Δ]P Pressure Drop across the valve psi
SG Specific Gravity of the liquid related to water = 1.0

Fv Viscosity Correction
1<[&nu;]<1.5
Fv = 0.99
1.5<[&nu;]<=1000
Fv = -0.1728 * Log₁₀[&nu;] + 1.04
[&nu;] Viscosity centiStokes

**********************
"Being GREEN isn't easy" ..Kermit

http://www.youtube.com/watch?v=hpiIWMWWVco

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