Brooks Instrument 5851i - Manual (Page 43)

4-15
Installation and Operation Manual
X-TMF-5851i-MFC-eng
Part Number: 541B109AAG
September, 2009
Brooks ® Model 5851 i
Section 4 Maintenance
& Troubleshooting
Flow Rate: 100 slpm
Outlet Pressure: 30 psig
Inlet Pressure: 50 psig
1. Determine Nitrogen equivalent flow rate (refer to Table 4-3).
Q
Nitrogen
= Nitrogen equivalent flow rate (sccm)
Q
gas
= Desired flow rate of the gas (sccm)
D
Nitrogen
= Density of Nitrogen at 70°F
D
gas
= Density of the gas (taken at customer
temperature)
SG
gas
= Specific gravity of the gas (taken at customer
temperature)
Refer to Table 4-3 for specific gravities.
Example:
In order to calculate the orifice conversion factor when using a gas mixture,
the following formula must be used:
Where P1 = percentage by volume of gas 1
P2 = percentage by volume of gas 2
Pn = percentage by volume of gas n
Example: Find the Nitrogen equivalent flow for 20 slpm of a 20%
Helium and 80% Chlorine gas mixture.