Chromatography Forum

Suppose you have a brownout or power unexpectedly coming on and off, with no time to properly vent/shutdown a GC/MS... in our experience it's better to just turn them off, because not doing so can result in a blown board. But what are the consequences of doing that? Oxidized source? Pump oil in the MSD?

Is there anything you can do to avoid those problems? I assume it helps to just leave the roughing pump on so at least some kind of vacuum is mantained? One setup we have (6890/5975) has the pump plugged directly into the MS so that's not an option. Anyone have any suggestions?

My past practice has been when the power has dropped and instrument have gone off line, to hit power mains as quickly as I can because the power may not come up "nicely" (low votage or go up and down). After the lights in the room come back on and don't flicker, turn everythign back on. It is the running with the voltage way off specification or spikes that I am trying to avoid.

Pumps should have an anti-backstreaming valve in them. I've seen one fail Carrier flow will stop on instruments with eletronic flow controllers, so the instrument will suck air through the septum purge or split valve. But that's life. I don't want to replace the main board in the mass spec or the rough pump. The loss of the column or doign some source cleaning comes with running the instrument anyhow - we may have just accelerated the process a bit.

Don's advice is good - if the power goes off, switch off at the mains until after it has come back on and settled down.

Some MSs have an option to fill themselves with helium from a separate line when vented - I'm not sure that it works when the power goes out though.

The only sure way to avoid these problems is backup power - I have a UPS and generator, and two week sago we had a three-day power outage which made them work for their living.

Peter

I always did what Don suggested in the past, well if it happened when we were at work. Usually it happened to us in the middle of the night when no one was here

Normally you won't have a problem with pumps back streaming, even the Agilent units with diffusion pumps can handle an unexpected shutdown pretty well. I have modified most of my units to have the rough pump plugged directly into an outlet so that once power comes on I do have rough vacuum at least, and last year we installed a 150Kw backup generator which comes on within 10 seconds of a power outage. It is a really nice thing to have as it brings the power back on smoothly when it starts up and also waits until you have smooth power for a few minutes before it shuts down again, preventing a lot of the surging that goes on when the power company turns the power back on.

Twenty years ago when I first began the worst thing was the HP 5995 GCMS's we had, those huge diffusion pumps would backstream every time there was a power outage and we were having those about twice a month.

Thanks for the advice, everyone. We've had our second day of power outages in under a week, with more to come I'm sure! We're lucky enough to have 24/5 staffing, at least, and if all goes well we'll have everyone trained up on what to do so I won't have to take frantic 3 am phone calls.