Brooks Instrument 5851EM - Manual (Page 50)

4-12
Brooks ® Models 5965, 5851EM
Section 4 Maintenance
& Troubleshooting Installation and Operation Manual
X-TMF-5965-5851EM-MFC-eng
Part Number: 541B122AAG
September, 2009
Example:
Q
gas
= 2,000 sccm
= 2,000 x .269
= 538 sccm Nitrogen
In order to calculate the orifice conversion factor when using a gas mixture,
the following formula must be used:
Where P
1
= percentage by volume of gas 1
P
2
= percentage by volume of gas 2
P
n
= percentage by volume of gas n
Example: Find the Nitrogen equivalent for 20 slpm of a 20% Helium and
80% Chlorine gas mixture.
Q
Nitrogen
= Q
gas
(orifice conversion factor)
= 20 x 1.439
= 28.78 slpm Nitrogen
2. If inlet and outlet pressures are given in gauge pressure (psig) add 14.7
to convert to absolute pressure (psia).
Outlet Pressure — 30 psig + 14.7 = 44.7 psia
Inlet Pressure — 50 psig + 14.7 = 64.7 psia