Hi all,

Could anyone advise me how to convert cfm to slpm?
I'm running a A3000 Metco system on with a S3 robot. I'm spraying PAC and Praxiar powders and I believe they quote their gas flow in cfm.
Looking at conversion charts 1 cfm = 28.3 lpm thus a typical gas flow of 100 cfm = 2830 lpm right? This doesn't seem right since the A3000 only allows 100 slpm! Am I missing something with the standard part of standard litres per minute?

For the flow above (Praxiar Inco 718 powder Argon flow - 3M) the guys have the machine set to 55 slpm. I've no clue how they came to this figure.... taking to them they don't either!

Thanks

Jim

Hi Jim

Understanding gas flow and measurement in thermal spray processes does seem to cause a lot of confusion, particularly when trying to relate gas flows between different control systems for operation of the same gun, like trying to duplicate parameters between 7MC, 9MC and A3000 etc. for say a 9MB gun.

First point, we are considering a volumetric measurement per amount of time of gas. Problem here is that, what is important to the thermal spray process, is the AMOUNT of gas (number of atoms/molecules or mass). A volumetric measurement of a gas is really meaningless by itself, unless we consider the effects of temperature and pressure (same number of atoms/molecules or mass of a gas will ocupy different volumes if we change conditions of temperature or pressure). So it is important that if volumetric flow is used to measure/contol the amount of gas, then conditions need to be known and flow units standardised. Common units used:
* Metco Flow Meter Reading (FMR) (specific to equipment/process)
* SCFH (Standard Cubic Feet per Hour (70F)
* N.L.P.M or SLPM (Normal/Standard Litres per Minute (0C)

If we consider say an older 7MC system, which uses flow meter tubes and reads in Metco Flow Meter Reading (FMR) units. These units are practically meaningless outside of the equipment/material spray parameters designed for it. Conversion to standard units is possible knowing FMR, pressure, temperature and tube calibration conditions (see here) Hydrogen secondary gas is far more complicated I won't explain here (see here). More recent equipment either use flow meters (using specific parameters) designed to give direct readout in SCFH or SLPM/NLPM or mass flow meters.

Quote:Looking at conversion charts 1 cfm = 28.3 lpm thus a typical gas flow of 100 cfm = 2830 lpm right? This doesn't seem right since the A3000 only allows 100 slpm! Am I missing something with the standard part of standard litres per minute?

Yes, 1 cfm = 28.3 lpm thus a typical gas flow of 100 cfm = 2830 lpm
Are you sure you not confusing CFM with CFH? 100 SCFH is in the right ball park for plasma gas flow. 1 SCFH = 0.472 LPM so 100 SCFH = 47.2 LPM - more like it?
but wait, 47.2 LPM from above calculation really means 47.2 LPM @ 70F around normal atmosheric pressure (standard conditions for SCFH). This is not the same as SLPM/NLPM where standard conditions are 0C not 70F . So we need to apply corrections for the different conditions. So 100 SCFH = 47.2 LPM = 43.8 SLPM or NLPM.
You can use the plasma gas flow calculator to do this easily by inserting say 100 value into one of the SCFH boxes, calculate and read across.

Final point, you need to be careful where your gas flow parameters are coming from and you need to know what equipment and gun (and set-up) they are intended for. For example you can not use 3MB/7MB/9MB gas flow parameters say for a F4 gun or for that matter when using different nozzles.

Sorry for long lecture just trying to cover everybody. Hope it helps.

TurbineRepair Wrote:Hi all,

Could anyone advise me how to convert cfm to slpm?
I'm running a A3000 Metco system on with a S3 robot. I'm spraying PAC and Praxiar powders and I believe they quote their gas flow in cfm.
Looking at conversion charts 1 cfm = 28.3 lpm thus a typical gas flow of 100 cfm = 2830 lpm right? This doesn't seem right since the A3000 only allows 100 slpm! Am I missing something with the standard part of standard litres per minute?

For the flow above (Praxiar Inco 718 powder Argon flow - 3M) the guys have the machine set to 55 slpm. I've no clue how they came to this figure.... taking to them they don't either!

Thanks

Jim

hello
please can you explain the terms :
cfm?

lpm,?
and splm?
i tried to understand but terms can means several things,of course I UNDERSTAND YOU but young people must undestand what you say,in this case you have to give them complete meaning of abreviations
may be they have solution for you and me

Hi Hvofhamid

Sorry if the meaning of the abreviations were not clear

CFM - Cubic Feet per Minute
LPM - Litres per Minute
FMR - Metco Flow Meter Reading
SCFH - Standard Cubic Feet per Hour
N.L.P.M or SLPM - Normal/Standard Litres per Minute

Gordon Wrote:Hi Hvofhamid

Sorry if the meaning of the abreviations were not clear

CFM - Cubic Feet per Minute
LPM - Litres per Minute
FMR - Metco Flow Meter Reading
SCFH - Standard Cubic Feet per Hour
N.L.P.M or SLPM - Normal/Standard Litres per Minute

thanks gordon,it s very nice of you

Gordon,

Again thank you for the explanation. I understand the situation much better now with regards to the standard units and converting between the 2.

Our Sulzer commissioned A3000 system is calibrated to automatically control the pressure to achieve the desired flow rate in slpm, or so I'm told! I think I will check this with Sulzer.

Praxiar did state to me that their units were in cfm but perhaps they meant cfh? The next time we use thier powder I'll give them a call.

I'm still a little worried by our operators though. I asked how they convert the Praxiar units to meet our machines input requirements. They stated they divide by 2.2. The trouble is they managed to calculate 100/2.2 = 55!! I think I may have my work cut out?

Hvofhamid,

Sorry for the ambiguity, working in the aerospace sector I find abbreviations a real pain- I’m still trying to find out what a EMU is, I thought it was flightless bird or something to do with Rod Hull!

Regards

Jim