Column head pressure, but no flow

[Vox]

I am currently running a 5890a. I have column head pressure but no flow. It's a new column and I conditioned it yesterday and I was still getting flow today. I turned on all the other gases, set the oven temp and detector/injector temps and now I have no flow. Is my column plugged?

At some point during the conditioning someone turned the N2 off (I have no idea who would feel the need to turn off the gas on a machine they have no clue about), but I turned the gas on and was getting flow yesterday. After I conditioned it yesterday I let the oven cool and turned the oven off overnight leaving 6ml of flow. Today I still had that 6ml of flow then I turn everything else on and now I have no flow. I'm very confused and scared. Thanks for any help.

[DR]

2-3 steps I'd take:

1) Reinstall the injector end of the column after cutting off ~15cm. If that works, great. If not

2) Repeat procedure at detector end.


3) Knock some sense into whoever shut your gas off. It won't help unplug your column, but it will make you feel better and possibly prevent it from happening again.

[Vox]

I depressurized my system and now I have flow! I decided to do things one at a time to get it restarted.

I turned on the oven, the flow decreased slightly. Then I turned on the injector to the correct temperature, flow plummeted! When I open the left panel the main flow control module is rotated to the left like someone just cranked on the control to try and get more flow out of it. I'm thinking it's bad. I'm switching to injector B. I'll report back what I find.

Or did I overtighten something when I installed the column? Thanks.

[Peter Apps]

Hi Vox

How are you measuring the flow ?. What kind of column do you have, and what kind of inlet ? Is the nitrogen that got turned off the carrier gas, or the detector make-up ? Have you checked for leaks (which can be difficult with nitrogen as carrier gas).

Peter

[Vox]

When my injector temp gets over 135 my flow drops like a rock. What would cause this? Should I just switch to Injector B? Thanks.

[Vox]

Flow is being measure by pressing flow A. N2 is carrier gas.

[Vox]

Packed column and a split/splitless inlet adapted over to packed. I'll take some pictures.

[JI2002]

Flow is being measure by pressing flow A. N2 is carrier gas.

That's not how the flow should be measured. Measure the flow rate from the detector side by using a flow meter.

Are you using constant flow or constant pressure? As long as you have enough column head pressure, you should have flow.

[Peter Apps]

If the flow stops when the injector gets hot it is probably something expanding and blocking off the gas flow. Would I be right in guessing that the top of you column almost touches the septum (this will depend on how heavilty the inlet is modified) ? Then when the inlet gets hot the septum expands and seals over the top of the column. Do you have pressure control or mass flow control ? - if the latter you should see the inlet pressure rise as the flow falls. If this is plausible then just move the column down a couple of mm.

Peter

[Vox]

Peter is a genius. Thanks! Now, to get my FID to light...

My ignitor may just be shot. I'm going to get some matches and I'll try that after lunch.

Thanks everyone.

[Consumer Products Guy]

Don't go running for the matches just yet. I'll assume that your ignitor is not glowing orange when you push the button. Allow your hydrogen and air have been flowing for about 10 minutes. Take your 5/16 open end wrench and back off the ignitor about 1/2 turn, then retighten it. Take a screwdriver and loosen the detector screws one turn, then retighten. We often find that poor contact causes the ignitor to behave like it's burnt out. Re-try lighting the detector.