Switching off GC-MS - non-return valve concern

Hello everyone,

I am going to have to switch off the GC-MS because of possible power cuts over the weekend.

I had read an Agilent document on how to switch off a GC-MS properly according to the amount of time it will be off but I cannot find it...

I do remember though that for a short period of time, the system can be vented just enough to remove the column and to plug the transfer line, pumped down again to recover the pressure and vented again.

The system will be switched off with the pump at <40% of the speed and hot zones below 60ºC.

I like this procedure because I don't want to have leaks at the o-rings when the system will get to atmospheric pressure (I have a sweet Hi Vac of 2.95E-09 right now).

However, I'm worried the non-return valve of the rough pump will fail and let oil in the system.

Should I let the MS under vacuum with the pump off or should I vent it completely until atmospheric pressure?


  • Hi

    Hope,Above is that document, you are looking for..

  • That's it! Thank you.

    But my I'm still concerned about the anti-suckback valve of the rough pump. 

    Can it get stuck and not function as it should?

  • Share pic of anti-suckback valve of rough pump then i can say...

  • I dont' know if the valve is with the pump or at the entrance of the MSD.

    Anyway, after talking with the lab manager, the system will be switched off under vacuum. 

  • In this picture, only, i can see exhaust filter in white color..

  • It's OK.

    I don't know if the valve is included in the pump or somewhere else.

    If the valve fails, we'll have to use our Agilent maintenance/repair contract to clean the system... ;)

  • The anti-suckback valve is built into the pump.  When you turn off the pump, watch the vacuum hose where it connects to the pump.  If you see some oil splash up into the hose, then the valve is not working properly.  If that's the case the rough pump would need replacement.  The vacuum hose is long enough that the chances of oil getting all the way into the MSD are very low.

  • Hi since your question is about the GC/MS I moved it from the Gas Chromatography forum to the GC/MS forum.

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