User guide

Checking for Leaks 6
Advanced User Guide 147
To Perform a VI Pressure Decay Test
The pressure decay test checks for leaks from the inlet flow
module up to the column fitting.
Initially test the VI with a sampling system installed. If the
system fails the leak test, then isolate the VI from the sampler as
described in “To Prepare the VI for a Closed System Leak
Check” on page 150.
After performing maintenance, first check for leaks in
externally accessible areas. See “To Check for External Leaks”.
If a leak is known to exist, check the externally accessible inlet
fittings first, especially any connection that has seen recent
maintenance, such as the column connection, split vent line,
and so forth.
The pressure decay leak test described below requires removing
the column and capping the inlet column fitting. This test
can/cannot find the following types of leaks:
1 Gather the following (see Consumables and parts for the VI):
• No- hole ferrule
• 1/4- inch wrench
• Heat- resistant gloves (if the inlet is hot)
• Long column nut
• ECD/TCD Detector plug (part no. 5060- 9055)
2 Load the inlet maintenance method and wait for the GC to
become ready.
The test can find leaks at the: The test cannot find leaks at the:
sampler connection column fitting
pressure sensing line connection to
the interface
gas supply bulkhead fittings to the
flow module
split vent line connection to the
interface
tubing and connections in a transfer
line connected to the inlet
the connected sampler’s entire sample
flow path
flow manifold split vent valve
flow manifold septum purge valve
split vent tubing and trap