Converting PPM to a leak rate.
Converting PPM to a leak rate.
(OP)
Hi all,
I am curious, how does one convert between a contamination level of process flow measured in PPM to its corresponding leak rate.
As an example given a process flow with a known mass flow rate, gas species, pressure, temperature and allowable contamination level (say 0.2 PPM) how do we determine the maximum allowable leak rate.
I would appreciate any feedback.
I am curious, how does one convert between a contamination level of process flow measured in PPM to its corresponding leak rate.
As an example given a process flow with a known mass flow rate, gas species, pressure, temperature and allowable contamination level (say 0.2 PPM) how do we determine the maximum allowable leak rate.
I would appreciate any feedback.





RE: Converting PPM to a leak rate.
It states that 'if the temperature and species of gas are known, the pressure term in this case can be directly converted into density and hence mass flow.' So then, my example:
For air leaking into a helium line resulting in a maximum 0.2 PPM (by mass) for 10 g/s flow rate of helium. This would result in 2x10^-7 g/s of containment flow.
m' = 2x10^-7 g/s = V'ρ.
At STP air has a ρ ~ 1.204x10^3 g/m^3
So V' = 1.667X10^-10 m^3/s
Therefore Leak Rate = V'P = (1.667X10^-10 m^3/s)(101325Pa)
Leak Rate = 1.68875x10-5 Pa m^3/s
Does anyone see any glaring flaws?
RE: Converting PPM to a leak rate.
RE: Converting PPM to a leak rate.
http://www.epa.gov/ttnchie1/efdocs/equiplks.pdf
RE: Converting PPM to a leak rate.
The equipment cannot be tested as we are not in possession of it yet, instead this leak rate will be set as a guideline to be placed in a contract for it.
RE: Converting PPM to a leak rate.
If the 0.2 ppm is on a mass basis, take your process flow in mass terms and multiply by 2e-7, that will give you your allowable leak rate.
If the 0.2 ppm is on a mole or volume basis, take your process flow in mass terms and convert to moles per time unit. Multiply by 2e-7, that will give you your allowable leak rate in moles per time unit and you convert back to mass or whatever units you want to put in the contract.
RE: Converting PPM to a leak rate.
If y is your known flow rate you can calculate x - the leakage rate.
RE: Converting PPM to a leak rate.
So its not as simple as finding what fraction of the flow the contamination is.
RE: Converting PPM to a leak rate.
RE: Converting PPM to a leak rate.
RE: Converting PPM to a leak rate.
And thank you chicopee I will try looking into it.
RE: Converting PPM to a leak rate.
RE: Converting PPM to a leak rate.
RE: Converting PPM to a leak rate.
RE: Converting PPM to a leak rate.
ppm is parts per million, percent is parts per hundred. Just divide by ten thousand. Ten ppm is 0.001%
Note that ppm can be figured based on weight ratio, volume ratio, or molar ratio. The percent figure above will be on the same basis.
RE: Converting PPM to a leak rate.
For water treatment.