Metco FMR unit conversion
06-29-2007, 01:28 PM,
Cool  Metco FMR unit conversion
I would like to convert FMR units in SCFH.
Metco DJ console flow meters show:

Air: SCFH=15.80x%
O2: SCFH=14.44x%

Are these equations OK ?

And for Hydrogen ??

Thank you
06-29-2007, 03:07 PM,
RE: Metco FMR unit conversion
Hi TintinMilou

Sign0016 to the Surface Engineering Forum.

If you have a copy of the Metco Diamond Jet Process Manual, there should be a section towards the back giving flow rate conversion tables for some fuels, oxygen and air.

Your equations seem ok if you are operating specifically at a pressure of 75 psi for air and 150 psi for oxygen only. (info from original Diamond Jet Process Manual)

air - SCFH = FMR . 15.795 . square root(P + 14.7/14.7)
oxygen - SCFH = FMR . 4.314 . square root(P + 14.7/14.7)

I would have thought Sulzer Metco would have flow rate conversion tables for hydrogen. My old manuals don't include hydrogen (propylene fuel only), later manuals might. We also need to be careful that we are talking about the exact same type of flow meter. If you can not obtain conversion tables you could do the maths
if you know the calibration details of the flow meter tube (gas type/molecular weight, pressure and temperature).
06-29-2007, 08:51 PM,
RE: Metco FMR unit conversion
Thank you very much Gordon !!!
07-02-2007, 06:00 PM, (This post was last modified: 07-15-2007, 06:18 PM by Gordon.)
RE: Metco FMR unit conversion
Hi Gordon,

Does back pressure from the torch effect your conversion formulas?


Edit: Nevermind, I figured it out. Smile
07-03-2007, 12:03 AM,
RE: Metco FMR unit conversion
Hi Rick (RGS)

Sign0016 to the Surface Engineering Forum.

For those that may not of figured it out:

Under normal operating conditions using flow meter tubes with the flow adjustor/throttle on the output side (usual set-up), back pressure from the gun should have little effect on the reading, as the flow meter tube should be under steady pressure as set from the gas supply regulators.

The only exception I know is for the Metco 3M/7M plasma hydrogen flow meter which has the adjustor on the input side (I think this was for safety reasons). This set-up does effect the reading as the tube pressure is dictated by the back pressure and not so much by the regulated input. In this case the conversion formulas are not accurate as pressure becomes an unknown factor.

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