14 Flow and Pressure Modules
Operation Manual 203
Restrictors
The Aux EPC and aux PCM channel use frit-type restrictors to allow accurate flow control.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.
When installing or replacing a frit, always use a new O-ring (5180-4181, 12/pk).
Table 23 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 rings
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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