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Forward pressure valve leaks
Occasionally an increase in pressure, rather than
a decrease may be observed. This is usually due
to slight leakage into the module across the
forward pressure control proportional valve.
Although slight leaks of this nature do not create
chromatographic problems, they may obscure
other small leaks that do cause problems by
allowing air into the system. The valves can leak
at about 0.2 mL/min and be within specification.
To check for internal valve leakage (when leak
testing the EPC module only):
1. Remove the supply pressure at the carrier
inlet fitting, and quickly cap the fitting with
a solid 1/8-inch Vespel plug and a Swagelok
nut.
Released: April 2004
2. Check the actual pressure on the display and
Locating leaks on the flow module
6850 Series Gas Chromatograph Service Procedures
monitor it for 5 minutes. Pressure loss
should not be greater than 0.5 psi.
Caution
If the EPC module appears to have a leak,
you can remove it to locate the leaky compo-
nent. The leak test kit (part no. G1530-
60960) contains a longer ribbon cable to
allow you to lay the EPC module on the
benchtop for testing.
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