Hi all,
I love Marilyn’s comment that “luck works as good as skill”! Sounds about right with the Silflow MCD! We tried them out after the sales pitch and were never able to use them reliably.
We use the Vici 1/32” crosses (ZX.5) and tees (ZT.5) with 0.25 mm bore and either 0.4 or 0.5 mm ferrules (for glass capillary or metal capillaries, respectively). These tend to be leak tight after the first couple oven cycles and stay leak tight
for weeks (don’t go tightening when they aren’t leaking!) and they aren’t crazy expensive. We typically use the tee for hydrogen and the cross for carbon (we replace the hydrogen reactor with a glass capillary and run it through the reduction reactor).
I complained at one point here about issues with the nuts on the Vici crosses/tees seizing over time. We found that after 1-2 months, the male threads on the nuts deform (or oxidize?) but the female threads on the cross/tee are ok. We replace
the nuts when the threads no longer turn cleanly. We now typically get a year or so out of a cross or tee (and they fail usually b/c bad nuts get over tighten and then can’t be removed).
On a side note, I went to order combustion and reduction reactors and was shocked on the price increases (reduction is now $465). Anyone have a trick for tightening unions on homebuilt reactors in tiny ovens? I used to do this all the time in
the Agilent GC, but the oven is so cramped in the Trace GC between the column and the reactors, it’s hard to get a good angle to tighten the union without snapping the ceramic tube. Does this require “luck" too?
Best,
Aaron
--------------------------------------------------
Aaron F. Diefendorf, Ph.D.
Associate Professor of Geology
Department of Geology
University of Cincinnati
PO Box 210013
Cincinnati, Ohio 45221-0013
Office: 513-556-3787
Website:
aarondiefendorf.weebly.com
Dear Isogeochemists,
These fittings were supposed to solve everything. Valco unions were easy to get leak tight, but if you needed to install a new column or reactor--forget the fitting. I had to throw them out and start over. Then the sled--as Seth mentioned, awful
device with 2-holed ferrules. Folks in my lab have similar experience using 0.5 mm capillary tubing and trying (repeatedly) to get them leak tight. We've learned the Siltight "blocks" wear out--and we've replaced them when they seem to have bits of capillary
stuck in them.
Finding another set of fittings defeats the purpose of the siltite! 8 unions instead of 4--ugh. This should be a message to Thermo engineers to try to fix this problem and come up with a solution. At first we thought it was sloppiness in putting them
together, but we've learned that's not the case. I think luck works as good as skill. Patience is key.
How about glass press fit fittings for the 0.4 to 0.5 mm union?
Marilyn Fogel
Hi all,
I have also suffered under the Silflow MCD. I can second Chris: getting the 0.4 size leak-free is *significantly* easier than getting the 0.5 leak free. I have had little luck in getting
0.5 ferrules leak free using fused silica capillary, much less with the metal capillary attached to the thermo reactors (this is almost impossible). I've been given the suggestion of pre-conditioning the ferrules by leaving them in a beaker in the GC oven,
but this hasn't helped at all. Like Chris, I have resorted to using 0.4 ferrules with fused silica capillaries and using microunions to join the FS capillary to the 0.45 mm OD metal capillary attached to the reactors and the backflush. I have not found a permanently
satisfactory union for this purpose - the most success I've had so far is using the Restek MXT union (Restek #21386). However, I have (literally last week) broken the nuts of one during tightening and have decided to try using fresh nuts with each install.
The MXT union was leak-free for about a month and I think could probably be maintained with as-needed (careful) tightening. I have also tried the Siltight microunion (Restek #23886), but I was only able to get that leak-free with the metal reactor capillary
once and have since given up on it. I've tried the Gerstel GRAPHPACK 3D/2 connector on the metal capillary (Restek #20272) without any success yet. It's worth noting that VICI sells a Valco microunion (VICI # EU.5) that I have yet to try, but uses the same
exact ferrules as the Restek MXT union.
Anyone with advice on a preferred microunion for the metal 0.45 mm OD capillary coming from the reactor would be welcome, although I've tried damned near every option at this point!
Stay sane and good luck!
Best,
Jack Hutchings, Ph.D.
Manager, Konecky Lab
Department of Earth and Planetary Sciences
Washington University in St. Louis
Hi Ewerton,
I had asked for advice on this very problem not too long ago. The solution for us was to use capillaries (0.4 size) on all SilFlow connections instead of the silcosteel (0.5 size) that runs from the reactors and backflush, then I have to run a
microunion between the reactor/backflush and the Silflow. After that, I can get the system leak tight (after a few temperature cycles and tightening the union). I know other folks successfully use the Valco as a replacement, so you can consider that if you
have gotten the system leak tight using Valco?
Cheers,
Chris
—
Chris Wurster, Ph.D.
Senior Research Associate
Centre of Excellence for Australian Biodiversity and Heritage
College of Science, Technology, and Engineering
James Cook University
Cairns 4870
Australia
Office: D3-114
Fax: +61 7 4232 1583
Dear Isogeochemists,
Recently, we had a Delta V Plus installed in our lab. This equipment has installed with a Silflow platform to direct the samples to reactors. We are experiencing a constant leak coming from the Silflow, we did some tests to make sure that, exchanging
the Silflow for a Valco 4-way valve, and the leaks disappear using the Valco valve. We had tightened the nuts of the Silflow using the Fingertite as mentioned by Thermo, we are using the correct ferrule dimensions, and heated the oven at high temperature for
a few minutes but the leaks were coming from all nuts. Someone had experienced something similar when is working with the Silflow platform. If so, how to avoid or fix this problem?
Thank you,
Ewerton Santos
Department of Earth, Environmental and Planetary Sciences
Brown University
324 Brook Street
Providence, Rhode Island 02912
U.S.A.