5890 no gas purging

[MSCHemist]

I have an issue with my 5890 series II w/EPC FID. It seems no gas is getting through the purge tubing. Everything is going through the column. when I turn the flow controller up the pressure goes up and no gas is coming through the purge vent. It happened right after inlet maintenance. I am assuming either the split tube is clogged with condensed crud or the purge valve is stuck shut (though it was open at the time). I am hitting the purge valve and not hearing clicks anymore when opening and closing.

What are your suggestions?

[MSCHemist]

OK I am getting all out of sorts trying to figure out the flow path. I guess the chemical trap is for the carrier gas supply which is dumb as I have traps on my lines, the path from the purge line to the purge valve is clear, the septa purge is showing normal flow rate, Nothing is coming out of the split vent at the front of the instrument. Any ideas?

[MSCHemist]

Ok I've done so more digging arround and research and believe the issue is the proportional valve which is next to the purge valve. Does that sound right? IT also does not shut down it just sits there overpressure and sending >10ml/min down the column. I tried unhooking the tubing to it and the inlet still sits overpressure so could it be the solenoid?


http://chromforum.org/viewtopic.php?t=11811

[chemstation]

Hi,
I had a 6890 that was over pressuring, it had a clogged chemical trap on the septum purge line , as it
couldn't reduce the pressure.

The clicking noise you mention seems to be related to the split vent, if it is
related to the split vent. A very long time ago I had an issue of no split.

Within the solenoid is a metal bar with rubber inserts on the end of each end,
so that when energised, it would block off one flow path and open up a new path.

These rubber inserts had swollen, and so stopped the bar from moving, so
the flow path was now stuck.

For some reason forgotten, I was not able to get a replacement bar.

So I took the risk and found the sharpest scalpel , practiced on some speta.
and sliced the swollen ends so that they were flush again.(single motion cut, so no ridges are created)
re-assembled, and was still working even until the GC was replaced.

Alex

[MSCHemist]

Thanks I am pretty positive now it is the solenoid valve which is a common failure point on the 5890. I unhooked the line from the inlet and it depressurized and I un hooked the line from the solenoid to the proportioning valve and it did not. I found a source for them for ~$350 USD.

I always thought that big HPLC column looking chemical trap was for the split line but it is on the carrier gas feed up stream from the inlet. I am not sure what purpose it serves as I have traps on the carrier gas line.

[Peter Apps]

Varian (then Bruker, now someone else) also puts a small trap immediately upstream of the inlet. I suspect that it is related to the use of electronic pressure controls with plastic and elastomer components that outgas organics into the carrier gas - in the good old days there was a just pressure regulator upstream of the inlet, and it had a steel diaphragm.

Peter

[MSCHemist]

The only thing upstream of the inlet is the mass flow controller which is a manual gas flow regulator that sets the total flow to the inlet. I wonder if there is a way I could put it or some other trap before the solenoid to protect it from sample deposition in the future.

[Peter Apps]

The only thing upstream of the inlet is the mass flow controller which is a manual gas flow regulator that sets the total flow to the inlet. I wonder if there is a way I could put it or some other trap before the solenoid to protect it from sample deposition in the future.

I don't see why not - even if the mass flow controller has a plastic diaphragm it is probably pretty thoroughly degassed by years of carrier flow. You could just add a filter downstream of the inlet (nearly all GCs now have these). Use something with a small volume though or you might see the inlet pressure fluctuating.

Peter

[MSCHemist]

Darn it looks like there is a plug in the proportional control valve or it is frozen shut. I got a new solenoid and it goes to 1ml/min column flow when I unhook the line to the proportional control valve but when I hook it up to the PCV nothing will comes out the split and everything goes down the column. Is there any way to unplug it? I am assuming there is sample deposits in the line and valve?

[Yama001]

I do not think the proportional valve can be unclogged. Thats an event that often puts the old 5890 to bed, as it can be a pretty expensive part. Likely hard to find by now.

[KM-USA]

Is there a part number for this "proportioning valve", or a good picture? I'm junking a 5890 this week plus have some spare parts left over.

[MSCHemist]

I'd be very happy to buy it off you. I took mine off today and even tried flushing it with MeCl2 and everything it is jammed hopelessly shut.

19251-60720

It is a black on bottom cylinder with brass on top with two silver lines on top one goes to the solenoid which is right next to it and the other goes to the split vent at the front of the instrument. It also has an electronic cord with a big white rectangular 3 wire connector.

It is next to the solenoid and held on by a large flat hexagonal nut. It is attached to the final split line and is a real bear to take off the front of the instrument where the vent is (I don't care if you have to cut it I'll buy a union).

There are instructions and pictures on this old posting
http://chromforum.org/viewtopic.php?t=11811

my email is sschoenfeld[at]innovaflavors.com

[MSCHemist]

I do not think the proportional valve can be unclogged. Thats an event that often puts the old 5890 to bed, as it can be a pretty expensive part. Likely hard to find by now.

It is actually not hard to find but it is so darn expensive it isn't worth spending $900-$1200 new on an old 5890.

I had no idea there was nothing in between the splitline and the valves and that the stinking chemical trap was up stream of the inlet. It was the first time I took the full left pannel off because the 7673 tray can be touchy to get the right angle so it grabs and passes the vials correctly.

It is also a pain in the neck to take off without cutting the final vent line.

[KM-USA]

I don't have that part loose, the 5890 in lab being disposed is not EPC. But we are also ditching one in the warehouse that likely is, maybe I can check that in a few days.

[MSCHemist]

OK thanks I'll keep my eye on ebay or whatever. We probably aren't going to want to shell out $900-1200 on that old GC.