5890 flow problem

[jfrankh]

Hi. I am trying to resurrect a 5890A that hasn't been used
since the late 90's. It has an auxiliary flow panel and a
nitrogen-phosphorus detector. I have been warned about
potential problems with the detector, but a gas flow problem
has stopped me before I could even turn on the detector

The gases were already plumbed as indicated in the manual,
so I have installed new traps and pressurized the gas lines.
The gases are carrier and detector makeup (He), as well
as H2 and Air. The auxiliary panel gauges indicate that the
gases are reaching this panel acceptably. Unfortunately, I cannot
seem to get any flow to the detector. Even after turning the
mass flow controller many times counterclockwise, and the
backpressure regulator many times clockwise, column head
pressure has remained at zero, and no flow has reached the
detector (according to my bubble meter). I took apart the
tubing directly upstream of the front flow panels, and there is
plenty of pressure.

So I wonder, is there a blockage in the front panel valves or gauges,
or have I in my ignorance of 5890A construction missed something
obvious, like a "turn all gas flows ON" switch?

thanks in advance for your comments!

[Les]

Has the possiblity of a bad mass flow controller been eliminated? I've replaced a few bad ones in my time. Once I had problems with reproducability, while sitting in front of the GC with the flow meter attached, I watched the split flow ramp up and then back down. Amazed I sat and watched. The same happened a few minutes later but not the same magnatude.
Replaced the split flow mass controller.... problem disappeared.

[jfrankh]

Thanks Les,

I haven't swapped any parts out yet.
That'll be the next step if I can't find the
secret "block all flows" switch.

[Consumer Products Guy]

All those parts should still be available, and field installable by you.

[gcguy]

Is it just the make up gas that you get no flow from. Inside the make up on/off gas valve the is a small adjusting screw. This can be set to closed even though the valve appears open.

[jfrankh]

Good question, gcguy. Actually there seems to be a problem
with all the gases. I have a bubble meter attached to the top of the
detector, and no movement of gas is evident even when the
carrier, makeup, and detection gases (He, He, air, H2) are "on" at the
auxilliary panel. At the same time, I can't ge the "column
head pressure" guage to respond to anything. I've verified
that I'm working with the correct inlet and detector.

I'll fiddle with that inner adjusting screw some more.
Thanks again.

Consumer Products Guy, that's a relief. Thanks for pointing
that out.

Unless I hear more from you and other GC Wizards, I'll start
swapping out parts from some idle GCs we have to see if it makes
a difference. I'll let you know when I find out what the problem was.

thanks again!

[Consumer Products Guy]

Restek also sells repair parts for Agilent 5890s. I'd start with the detector flows first, get those going. Those little O-rings with the split fingertight nuts going to the panel flow components are tough, the can fall off easily. for the column flow, you'll need to install a column or block off the inlet, the control is "later" in the flow path than the split.

[Ron]

I think there are many potential problems with this GC. Lack of headpressure at the injection port could be a mass flow controller, or it could be a very large leak somewhere in the inlet system. It also sounds like the detector may have a very large leak, otherwise you should see some flow from the detector from some of the gases. The odds of all flow controllers failing at once are highly unlikely.

This is a very old GC that has not been run for at least 5 years according to the original information. It may be more cost effective to simply buy a new GC with a warranty instead of spending all the time and effort required to get this one running again. Try to find out why the GC has not been used for all this time. It is rare for a properly functioning instrument to be allowed to sit for 5 years.

[arie2044]

hi jfrankh
in my knowledge of hp5890 it is very hard not to have flows for 4 streams i'm affraid you have the problem in the purification units or at the inlet you crossed the connections. the worst situation can be at the mass flow controlers when the needles are broken inside ( it happens)
try to remove the valve needles and then apply pressure at the inlet and see what you get
good lack

[Russ]

If I am reading your message correctly, you said you are getting flow to the instrument (front flow panel) but are not measuring it at the detector. You also are apparently not getting carrier flow to the detector which goes through a different flow regulator. Like arie2044, I am having problems coming up with a single thing that could be causing these (other than this instrument has been scavenged for parts) so I will throw out some simple checks you may have already performed. 1) When you said you "took apart the tubing directly upstream of the front flow panels" are you talking about the auxilliary panel or the ones inside the left panel of the GC? If you haven't already done so, remove the left side panel and check to make sure you have flow to the carrier flow controller (and the detector flow controller as well). 2) What may be very basic but often gets overlooked in our lab is the condition of the adapter used for measuring flows (though I am not sure that this would cause no flow to be measured). Make sure the o-ring on it is in good shape with no tears. 3) Make sure the detector "adapter" ferrule is in good shape and that the adapter is tight. 4) Are you measuring flows with a column installed or with the detector plugged off? 5) If you haven't already done so, you might also take the detector apart and check the condition of all o-rings in it and the jet. I guess it is possible for a jet to be so plugged that no flow gets past it.

[jfrankh]

Thanks all for the replies. Since my last post, I obtained a leak detector and found a major leak in the inlet region. . .the glass liner was smashed and its o-ring was melted onto it. Isn't that lovely? I cleaned the inlet and replaced everything, and immediately started getting a flow to my bubble meter (attached to the detector) and now the column head pressure gauge is responding. Oddly, now the auxillary gas is reaching the detector. Clearly I have much to learn about this thing. The detector also has a leak. I shall tackle that next and report back.

thanks again!

PS, the last user was a grad student who had probably never used a chromatograph of any type before. It hadn't been used for years before him, and he couldn't get it to work

Instrumentation is definitely not everyone's specialty.