28 Advanced Operation Manual
2 Flow and Pressure Modules
Restrictors
Both PCMs and auxiliary channels are controlled by pressure
setpoints. To work properly, there must be adequate flow
resistance downstream of the pressure sensor. Each channel
provides a frit- type restrictor. Four frits are available.
The one ring frit (low resistance, high flow) is installed in
all channels in the AUX epc when the instrument (or
accessory) is shipped. No frit ships in the PCM Aux channel.
Tabl e 2 Auxiliary channel frits
Frit marking Flow resistance Flow characteristic Often used with
Three rings
Blue
High 3.33 ± 0.3 SCCM @ 15 PSIG NPD Hydrogen
Two ri n gs
Red
Medium 30 ± 1.5 SCCM H2 @ 15 PSIG FID Hydrogen
One ring
Brown
Low 400 ± 30 SCCM AIR @ 40 PSIG FID Air, FPD Air,
QuickSwap, Splitter,
Deans Switch
None (brass tube) Zero No restriction Headspace vial
pressurization
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