User guide

4-18
Installation and Operation Manual
X-TMF-5850E-MFC-eng
Part Number: 541B102AAG
September, 2009
Section 4 Maitenance &
Troubleshooting
Brooks
®
Model 5850E
Q
GAS
x
Q
GAS
= Desired flow rate of the gas (sccm)
P
NITROGEN
= Density of Nitrogen at 70°F
P
GAS
= Density of the gas (taken at customer temperature)
SG
GAS
= Specific gravity of the gas (taken at customer
temperature)
Refer to Table 4-4 for specific gravities.
Example:
Q
gas
= 2,000 sccm
SG
gas
= .269
SG
Nitrogen
SG
gas
Q
Nitrogen
= SG
Nitrogen
= 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:
Orifice
Conversion
Factor 1
P
1
Orifice
Conversion =
Factor
Mixture
+ P
2
Orifice
Conversion
Factor 2
100
Orifice
Conversion
Factor n
+ P
n
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.
Orifice
Conversion = 20(.378) + 80(1.598)
Factor 100
Mixture
Q
Nitrogen
=Q
gas
(orifice conversion factor)
= 20 x 1.439
= 28.78 slpm Nitrogen
Q
GAS
x