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?

Thanks

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