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I'm trying to find a cheap manual vacuum pump for a sample transportation container that carries oxidizable samples of thin-film magnetic materials.

They already have a 15 nm Tantalum layer on top, so they can last for at least 2 days in normal air, but sometimes they need to be carried for longer in it.

So I was looking for a manual pump to carry with it in case it's needed, and I've seen that there are two cheap manual pumps used for two different applications: One is making vacuum in wine bottles and the other is making vacuum in bags.

And my main worry isn't about the piston they use, but rather on the valves, because of some tests I made with a coffee degassing valve earlier.

I know they're not intended for this, but they're also unidirectional. The problem is that they require a reasonable difference of pressure to open in the right direction, specially after they were exposed by a great difference of pressure in the wrong direction right before.

So if I used two of these valves in opposite directions to control the direction of flow with a piston, the container would never reach a good vacuum, it would be considerably worse than the vacuum reached in the piston.

So, in other words, I'm interested in knowing which valve (between those two options) opens the easiest with a difference of pressure in the right direction.

Thanks!

Ps.: Holding the vacuum isn't an issue, the container has a clamp to pinch the air hose in it to hold the vacuum, my main issue is about which one reaches the best vacuum.

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  • $\begingroup$ why do you need vacuum containment? ... wouldn't inert atmosphere be simpler? $\endgroup$
    – jsotola
    Nov 4 '21 at 5:36
  • $\begingroup$ you already asked at diy.stackexchange.com/questions/237724/… $\endgroup$
    – jsotola
    Nov 4 '21 at 5:41
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    $\begingroup$ So, purchase two examples and test, you say you are in a lab then testing should be easy. $\endgroup$
    – Solar Mike
    Nov 4 '21 at 6:32
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    $\begingroup$ @PeteW Thanks for the info, it's quite valuable. I ended up buying this vacuum pump (a wine one, not this one particular) because I concluded it would also be useful for doing some vacuum experiments using bottles and such. And if it's too poor I can try buying and adapting a vacuum valve from a vacuum bad into it, in case that valve does a better work. I'm sure the piston shouldn't be the problem. $\endgroup$ Nov 5 '21 at 5:38
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    $\begingroup$ @PeteW Just to mention that I tested them by checking the lowest temperature water boiled (while continuously pumped) and found pretty much the same thing. Considering I'm at sea level and using the Buck Equation I found a residual vapor pressure of 30 kPa, a little worse than your measurement, but very close. I then fitted a coffee valve inside the rubber cork to use it instead of the original and it improved to 25 kPa. It's really far from good, the pressure just fell to 1/4 of the atmospheric pressure. $\endgroup$ Nov 6 '21 at 6:05

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