Inlet Pressure

[cwp]

Hi All,
I am working on setting up an Agilent/HP 6890Plus GC with a Tekmar 7000 headspace sampler. The split/splitless inlet on the GC is not reaching the pressure setpoint when the split ratio is less than 75. I leak checked my gas line fittings and couldn't find a leak.

Also (maybe unrelated), when I set the inlet pressure through Chemstation, the GC display interprets the set point as a different value. For example, I set the inlet pressure to 15 PSI through Chemstation and click Apply, but the GC display shows the setpoint at 13.7 PSI. If I close the method window in Chemstation (so the GC display is not keyboard locked) and set the pressure directly from the GC display, it reaches the correct pressure.

[Himar]

Could be a corrupt method as far as the chemstation set point not applying to the GC. Try loading the default.m method and see if it will accept the set points.

[Bigbear]

How have you connected the two, 7000 in series with the GC inlet flow?

[cwp]

Could be a corrupt method as far as the chemstation set point not applying to the GC. Try loading the default.m method and see if it will accept the set points.

I tried loading the default method but the inlet is still unable to reach pressure setpoint with anything less than 75 split ratio.

How have you connected the two, 7000 in series with the GC inlet flow?

The 7000 is connected directly to the 1/16" carrier line on the GC inlet manifold.

[Peter Apps]

There is a leak somewhere - check with a leak seeker, including the plumbing inside the headspacer.

Peter

[RogerBardsley]

Hi cwp,

I am an Applications Chemist for Teledyne Tekmar. If there is no leak following the leak seeker, the Tekmar Customer Support team may be able to help. The 7000 is out of production, but they may be able to help. Our support phone number is on our website.

Best Regards,
Roger Bardsley
Applications Chemist
Teledyne Tekmar

[cwp]

Hi All,
Thanks for the suggestions. I have found the problem.

The ferroule inside the zero dead volume union where I connected the Tekmar transfer line to the GC inlet was not seated properly. I redid the connection and was able to reach pressure setpoints.

Unfortunately, I am running across another problem with the GC inlet pressure. I have made a separate post for that issue as it is not related to this one (http://chromforum.org/viewtopic.php?f=2&t=26610). If anyone reading this is familiar with Tekmar 7000 headspace autosamplers, please read my other topic!

Thanks,
-CWP