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The gas delivery system must meet the following
requirements:
• Stainless steel diaphragm tank regulators
capable of sufficient supply pressure (see
6850 Site Prep/Installation Manual for pres-
sures).
• All metal plumbing module comprised of
clean 1/8-inch copper (part number
5180-4196) or stainless steel tubing and
Swagelok fittings (many times "clean" tub-
ing from other vendors has caused high FID
background). The gas delivery module must
be leak free.
Released: April 2004
• Gas traps are recommended for carrier and
FID noise can be caused by many contributing
factors, including:
1. Contamination in the gas supplies to the GC.
6850 Series Gas Chromatograph Service Procedures
makeup gas supplies. Minimum trap configu-
ration should be:
All metal, conditioned moisture trap closest
to the tank (part number 5060-9084)
All glass, indicating O
2
GC (part number IOT-2-HP)
Never use traps made of plastic or that use
O-ring seals.
Normally if there is gas contamination, the
background will also be abnormally high
(> 20 pA).
trap closest to the
296
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