Brooks Instrument SLA5840 - Manual (Page 28)

4-6
Brooks ® Model SLA5840
Section 4 Maintenance
& Troubleshooting Installation and Operation Manual
X-PR-SLA5800-RT-eng
Part Number: 541B120AAG
August, 2009
Q
GAS
= 2,000 sccm
= .269
Q
NITROGEN
= Q
GAS
x
= 2,000 x .269
= 538 sccm Nitrogen
P
GAS
P
NITROGEN
P
GAS
P
NITROGEN
Example:
In order to calculate the orifice conversion factor when using a gas mixture,
the following formula must be used:
Where P
1
= percentage of volume of gas 1
P
2
= percentage of volume of gas 2
P
3
= percentage of volume of gas n
Example: Find the Orifice Nitrogen equivalent of 20 slpm of a 20% Helium
(He) (orifice factor = 0.378) and 80% Chlorine (Cl
2
) (Orifice factor = 1.598)
gas mixture.
Orifice
Conversion
= 20 (.378) + 80 (1.598)
Factor 100
Mixture
Q
NITROGEN
= Q
GAS
x Orifice Conversion factor
= 20 x 1.439
= 28.78 slpm Nitrogen
2. If inlet and outlet pressure 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