[Itsgotatail]

So, for the second time now, the power cut out last night while my oven was purging. Of course the vacuum pump oil pulled into the oven spraying all over and ruining a gorgeous half pound slab Jager shatter. Obviously a big, very costly disappointment. What's the easiest way that I can keep this from happening again? A check valve of sorts? A small triclamp column (4"×12"?) that sat between my pump and oven that could catch the oil? I was in tears when I got up today to find this.

[MrBungle]

Have you checked your oven for leaks?

[WaterFarmFan]

Sorry to hear that. You can add a tee a few feet from your pump and then place a normally open motorized valve at the end. You wire the valve to a power strip that also has your pump on it. When the power strip is active, the pump will run and the valve will close. If power fails (or you manually shut off strip), the valve will return to open automatically and prevent the oil from sucking in your oven.

[OldPhart]

Sounds like your pump needs new valves in it. I haven't messed with extraction, but the vac pumps that I have used for hvac will hold vacuum when turned off.

[Itsgotatail]

Great idea with that T valve setup. The oven holds a vacuum for 24 hours fine without any visible drop on the pressure gauge. When brand new, this vacuum pump would do the same. I don't believe there is any kind of check valve in either the pump or oven (newer AI 1.9 w\5 sided heating). It's not a great pump - an HFS 12cfm 2-stage - ~$200 new. But it does the job for now. Thanks for the help! If I were to put a cold trap in, I suppose I would want to put that T between it and the pump.

[Gray Wolf]

Originally Posted by Itsgotatail

So, for the second time now, the power cut out last night while my oven was purging. Of course the vacuum pump oil pulled into the oven spraying all over and ruining a gorgeous half pound slab Jager shatter. Obviously a big, very costly disappointment. What's the easiest way that I can keep this from happening again? A check valve of sorts? A small triclamp column (4"×12"?) that sat between my pump and oven that could catch the oil? I was in tears when I got up today to find this.

A check valve will work, but all have pressure losses across them, which will limit your vacuum at the oven. I've used spring ball checks before, but took the spring out and put the ball check in a vertical position.

A normally closed, power to open, vacuum rated solenoid valve will also work, with less losses.

We switched to an oil less Welch 2052 pump.

[OldPhart]

I've been thinking about this, and there is really no way to assure yourself that oil can't get back to the oven, other than a trap. I'm thinking something like a paint pot, https://www.grainger.com/product/1ZMG5 would be cheap enough, require no other pieces or parts, and stand no chance of failing. Just put this between the pump and the oven. No "tee" or anything, use two different ports, and NOT the port with the dip tube on it. If it did suck the oil out of the pump, it would just harmlessly collect in the paint pot. Just a thought, I like trying to find low tech solutions to interesting puzzles.