98 Agilent 7890 Series Troubleshooting
4 GC Not Ready Symptoms
The Inlet Pressure or Flow Fluctuates
A fluctuation in inlet pressure causes variations in the flow rate
and retention times during a run. Do the following:
• Check if the gas purifier or gas generator is operating at or
near capacity.
• Check the supply gas for sufficient delivery pressure.
• Verify that the supply pressure regulator is functioning
properly. Systems with long supply tubing lengths may
require a step-down regulator near the GC. Also, use an
additional regulator to smooth out fluctuations caused by gas
generators.
• Check for leaks. (See “Checking for Leaks”.) A large leak may
be present somewhere in the system. Use an electronic leak
detector to find leaks, then correct them. Do not forget to
check the column—a broken column is a very large leak.
• Check for large restrictions in the inlet liner or split vent
trap.
• Verify that the correct liner is installed. Some liners have
large pressure drops caused by design or tight packaging.
• Check for extreme changes in room temperature during runs.
Correct laboratory temperature problem or move the
instrument to a more suitable location.
• Check for a restriction in headspace, purge and trap, and any
other external sampling devices.
• Verify Auto Flow Zero feature is On. See AutoFlowZero.
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