4-10
Installation and Operation Manual
X-TMF-5860E-MFM-eng
Part Number: 541B106AAG
November, 2008
Brooks
®
Model 5860E
Section 4 Maintenance
Example:
The desired gas is Silane (SiH
4
).
The desired full scale flow rate is 200 sccm.
Sensor conversion factor is 0.68 from Table 4-3.
Air equivalent flow = 200/0.68 = 294.1 sccm air.
In the example above a size P restrictor would be selected. Both the
sintered metal and ACLFE are available for this size. Either type will work
however, since Silane is known to precipitate silicon dioxide particles when
contaminated an anti-clog laminar flow element should be selected for this
application.
NOTE: If the calculated flow rate is such that two different size restrictors
could be used, always select the larger size.
If a mixture of two or more gases are being used the restrictor selection
must be based on the air equivalent flow rate of the mixture.
Example:
The desired gas is 20% Helium (He) and 80% Chlorine (Cl) by volume.
The desired full scale flow rate of the mixture is 20 slpm.
Sensor conversion factor for the mixture is:
Air equivalent flow = 20/.903 = 22.15 slpm air.
In this example a size 4 wire mesh assembly would be selected.
