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N2 makeup gas flow won't stabilize (too high)
Posted: Thu Jun 24, 2021 4:35 pm
by JWF239
Hello,
I have a new Agilent 8890 GC that has been giving me a lot of trouble considering it is a new instrument.
One thing I just noticed yesterday was that the instrument would not stabilize and kept saying make up gas not ready. I checked and my makeup was set to 2 mL/min but the actual flow was 2.4 mL/min. I can set the flow higher than the 2.4 and get the instrument to ready, or turn off the make up and get it to ready, but for whatever reason I cannot get the make up flow to go below the 2.4. Any ideas?
Re: N2 makeup gas flow won't stabilize (too high)
Posted: Thu Jun 24, 2021 7:55 pm
by James_Ball
Does it specify a range that it will support? I don't think I have ever seen anything that uses only 2ml/min of makeup flow.
Re: N2 makeup gas flow won't stabilize (too high)
Posted: Fri Jun 25, 2021 5:35 pm
by JWF239
Does it specify a range that it will support? I don't think I have ever seen anything that uses only 2ml/min of makeup flow.
The range is between 0 and 100. I agree the 2 seemed low but the method was developed by a custom solution group and the main thing I'm concerned with is that it was running at 2 ml/min just fine up until this week. Trying to determine what caused the change.
The unit is only about 6 months old and has been giving me a lot of trouble and this is just the latest example of unknown changes.
Re: N2 makeup gas flow won't stabilize (too high)
Posted: Sat Jun 26, 2021 7:47 am
by antonk
AFAIK Agilent flow regulators is actually a pressure controller with appropriate restrictor placed at output.
Probably it is not tightened well. Check your tubing.
Re: N2 makeup gas flow won't stabilize (too high)
Posted: Sun Jun 27, 2021 4:42 pm
by AICMM
jwf239,
A suggestion - turn off the hydrogen and air to the detector and see if the make-up can get to it's set point.
Best regards,
AICMM
Re: N2 makeup gas flow won't stabilize (too high)
Posted: Fri Jul 02, 2021 1:26 pm
by Peter Apps
Does it specify a range that it will support? I don't think I have ever seen anything that uses only 2ml/min of makeup flow.
The range is between 0 and 100. I agree the 2 seemed low but the method was developed by a custom solution group and the main thing I'm concerned with is that it was running at 2 ml/min just fine up until this week. Trying to determine what caused the change.
The unit is only about 6 months old and has been giving me a lot of trouble and this is just the latest example of unknown changes.
You are stressing over a pointless quirk in a method. Presuming that this is an instrument with an FID, 2 ml/min of makeup flow will make no difference at all to anything, as long as the column is properly installed. How long was the warranty on the instrument ?