HI Matt--

Have you tried using a dryer/conditioner on the He line? 

John makes good points, and typically we'll also repack reactor after a few trays (solid samples here)

If the ceramic tube is warping more, the system might be running hot--or have a hot spot (get ready to replace heating element).  If the ceramic collar at the bottom chips or cracks, that can cause problems too.  Air will preferentially go up one side, cooling it a bit more than the other side.

take care,

gerry

On 7/24/2019 10:06 AM, Matthew Lachniet wrote:
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Hi all, 

I'm looking for ideas to help with a problem I had last year while running waters on my TC/EA (ConFlo III to Delta V Plus). 

Over the course of around 2-5 weeks while running water samples, the reaction product builds up on the outside of the glassy carbon tube to such a degree that it periodically fuses to the ceramic tube, ending up cracking both and resulting in rapid failure and an expensive replacement and downtime. 

Considering the high cost of He and glassy carbon tubes, I want to have a plan to solve this before running TC/EA again. 

I have the reverse flow modification on the TC/EA. 

I leak tested every part of the system I can think of using soap bubbles and never found a leak. I use Ultra High Purity Helium (grade 5, 99.999%). 

I never had this problem in the past until I switched gas suppliers so I did wonder if that was the reason. I could go to Research Grade He (99.9999%) but that is a much higher cost and haven't tried it yet. 

Reactor temperature was on the low side (1350 degrees C) because this is what was giving the lowest m/z 28 signal. Reaction at 1400 C or higher gave too much m/z 28 to get a good precision, so I wondered if the low reaction temperature could be a culprit. 

I don't know how accurate the thermocouple reading is. 

GC temp was around 85 degrees C. 

I always use super slow ramp rates on the Jumo controller to change temperature (usually over 12 hours or more to go from room temperature to 1350 C and vice versa). 

I also tried using the high purity ceramic tubes but that didn't solve it either.  

Any advice for how to handle this? Anything else I should look at? 

Thanks in advance, 

Matt