Agilent 7890A GC unable to reach set pressure

Discussions about GC and other "gas phase" separation techniques.

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Hello everyone
I am working with an Agilent 7890A GC. The main problem is that the inlet (split/splitless) is unable to reach any set pressure and remains extremely low and shuts off after a few minutes. Initially, the total flow (50 mL/min) is usually able to reach the set flow but it never works more than a few minutes.

The carrier gas is helium and I have checked extensively for leaks with a helium detector. I have also tried swapping out the EPC with no success.

Gas saver is off

I’ve put my thumb over the split vent exhaust, no change in pressure.

I have also performed a SS Inlet Pressure Decay Test, the pressure does not hold, however, I am unable to find leaks.

Any help is appreciated, Thank you
vedv wrote:
Hello everyone
I am working with an Agilent 7890A GC. The main problem is that the inlet (split/splitless) is unable to reach any set pressure and remains extremely low and shuts off after a few minutes. Initially, the total flow (50 mL/min) is usually able to reach the set flow but it never works more than a few minutes.

The carrier gas is helium and I have checked extensively for leaks with a helium detector. I have also tried swapping out the EPC with no success.

Gas saver is off

I’ve put my thumb over the split vent exhaust, no change in pressure.

I have also performed a SS Inlet Pressure Decay Test, the pressure does not hold, however, I am unable to find leaks.

Any help is appreciated, Thank you


Change septum.

Best regards

Henry
Did you cap off the septum purge outlet? We had an inlet recently that would not reach setpoint and the solenoid for the septum purge control was defective and was allowing all the flow to exit the septum purge. If you have a flow meter attach it to the septum purge outlet and see if the flow is near 5ml/min or closer to 100ml/min as ours was.
The past is there to guide us into the future, not to dwell in.
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