Helium leak rates: ppm & mbar*l/s

[NGiLuzzu]

In order to perform valve Fugitive Emissions tests, we use a VARIAN sniffer probe helium leak detector, which gives readings in mbar*l/s. Our usual European reference specification (Shell MESC SPE 77/312) also gives limits in the same measurement unit.
First of all, is anybody able to explain the physical meaning of "mbar*l/s"? Is that a flow rate or a concentration?
Then, how is it possible to relate this with "ppm"? As many leak detectors manufacturers have instruments with both scales, we think there must be a simple relation between the two units.
Many thanks in advance, 'NGL

 

[NGiLuzzu]

I found in Shell MESC SPE 77/312 (Revision: 26-11-2002), page 16, par. 6.1, note 7:
"... For leakage rates conversion factors see EN 1779 annex B
(1ppm He = 2.5 * 10-8 cm³ /s = 2.5 * 10-7 Pa*m3/s) ..."

This equivalence has been added in this latest revision of the document: if it's true, it means that
1 ppm = 25 mbar*l/s, or 1 mbar*l/s = 0.04 ppm of He.

Unluckily, EN 1779 (1999)standard does not explane how this could be derived. Is anybody able to do that?

Thanks in advance, 'NGL

 

[IRstuff]

Question and answer posted at:
thread124-48813

TTFN