Carrier Gas Flowrate Problem

[Sean]

I have a Varian CP 3800 GC with a type 1 EFC (1079 injection port).

The total flowrate of carrier gas is around 500 cc/min and I cannot find a way to reduce it. Also the pressure in the injection port is too high. The pressure at the gas cylinder is well within its limits.

I can reduce the flowrate to around 120 cc/min, but only by reducing the carrier gas pressure and then pressure in the injection port is too low.

I believe the problem is a broken flow controller but I was hoping someone might have some experience with a similar problem.


Thanks in advance.

[WK]

Hi Sean,
This is a vague memory from 5 years ago:
I had a similar problem when we had a CP8400 autosampler strapped onto the CP3800 - 1079 EPC. I think a different circuit board was required and subsequently it needed recalibration (?) since the carrier and split flows increased drastically.
Perhaps you have a circuit board failure?

WK

[Bernd]

Hello Sean,
check also the splitline, often here You can find condensate or dust or something else.
Check also the connections between the pneumatic-electronic part and the top of the instrument (Viton inlets 1/16" tubing)

Regards
Bernd

[BG]

Hello Sean,

Do you disassembly the left cover of the 3800 gc; perhaps you've catch splitline, or like Bernd sayed before the split line is blocked by condensate or dust.

Regards

[WK]

On this topic of 3800:
Have you had to replace either the 3800 carrier trap or 3800 split trap?
Does either affect flow?

[BG]

On my experience i never change the split trap and carrier trap
But do we speak about the same think trap under the 3800 GC, and not external trap before GC ?

[WK]

BG - thanks for the info - I did mean the traps inside the 3800.
Sean - sorry for extending the thread.
The internal plumbing of the 3800 is a little mysterious and full of connections - not helped by a lack of diagrams in manual.

[BG]

Sean,

I really think the pb is due to an obtruction of a 1079' tube.
Clean your injector by heating in first time to see the result and change eventually your insert (or control the insert mounting !)