HP 5973 MSD, Hardware Manual

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72
Troubleshooting
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How do I find the air leak?
1 Look for the last seal that was disturbed.
• If you just pumped down the MSD, press on the sideplate to check for proper
seal. Poor alignment between the analyzer and the GC/MSD interface seal can
prevent the sideplate from sealing.
• If you just replaced the reagent gas bottle or gas purifier, check the fittings you
just opened and refastened.
2 Check for tightness of seals at injection port and interface column nuts.
Ferrules for capillary columns often loosen after several heat cycles. Do not
overtighten the interface nut.
3 If any of the VCR fittings in the flow module have been loosened and then
retightened, the gasket must be replaced. These gaskets are good for one
use only.
4 Remember that most small air leaks visible in CI mode are located in either
the carrier gas or reagent gas flow paths.
Leaks into the vacuum manifold are not likely to be seen in CI because of the higher
pressure inside the ionization chamber.
5 Half-split the system.
• By closing valves starting at the gas select valves (
Gas Off
and
Purge
turned on),
then moving farther “downstream” to the isolation valve ( Gas Off turned on and
Purge turned off.)
• You can cool and vent the MSD, remove the GC column, and cap off the interface.
If you are used to using argon or other introduced gas to find air leaks, note that
this does not work well for the reagent gas flow system — it takes as long as 15
minutes for the peak to reach the ion source if the leak is at the inlet to the flow
module.
& $ 8 7 , 2 1
Do not loosen the nuts on any VCR fittings unless you intend to replace the gaskets.
Otherwise, you
will
create an air leak.