Clear vacuum tube search

[esbdmb]

Hi, I'm trying to find a material that is clear (possibly acrylic?) that I can hook up to a vacuum pump for some testing we need to do. The ideal solution would be something that is 3/8" dia and it only needs to be 4 or 5 inches long - a test tube would be perfect, but it has to stand up to a vacuum - I could insert it into a vacuum hose and hook the hose up to our manifold.

Any ideas?

Thanks!

 

[handleman]

Vacuum is not so much pressure. I would go ahead and try a test tube.

-handleman, CSWP (The new, easy test)

 

[hacksaw]

vacuum hose...thats a real trick, what sort of vacuum are you working with mmHg? Torr? milliTorr?

 

[esbdmb]

Hacksaw - around 10 mT would be the max (or I guess the min!).

 

[SnTMan]

esbdmb, how about some clear vinyl with a spring around it. From the hardware store.

Regards,

Mike

 

[ShaggyPE]

Agree with Handleman, you effectively need a tube that can withstand 15 psi pressure differential... where the exterior of the tube has the higher value.

Here is an online calculator for stress in a tube with pressure differentials. I did a quick calc for 3/8" ID, .125 Wall... the stress was miniscule... tinker with it.

http://www.engineeringtoolbox.com/stress-thick-walled-tube-d_949.html

-Dustin
Professional Engineer
Pretty good with SolidWorks

 

[esbdmb]

Thanks for all the responses! But I'm not getting what you're saying, I need the tube to be closed on the bottom and the top open so I can 'shove' it inside a vacuum hose. Then we want to pull a vacuum and see what happens to something that will be in the 'tube'. It's been in a steel tube up to this point and we want to see what is going on.

 

[Compositepro]

Any standard test tube can easily withstand the forces of vacuum. Any further questions?

 

[MiketheEngineer]

So you are basically saying you have an open ended tube and you are putting the WHOLE thing in a vacuum??

If I am reading is correctly there will be NO differential pressure around/in/outside the "tube. Basically you could put almost anything in there as long as it not alive or closed ended??

 

[esbdmb]

Mike, no the tube will be put partially into a hose that is pulling a vacuum so the outside of the tube will be in atmosphere.

 

[HDS]

Glass test tubes are used for this everyday all over the world without a problem.

 

[esbdmb]

I'll go ahead and try glass then - I'll let you know how it works in about a month.

Thanks again.

 

[HDS]

please do tell us how it worked. Most people fail to close the loop here.

 

[MiketheEngineer]

OH ---- Duh...

Depending on the amount of vacuum - I have broken them - sometimes - sometimes not. Like that answer??

 

[ShaggyPE]

How are you sealing the connection between vacuum and atmoshpere? The force/pressure to seal might cause a lot of stress in the glass testube. It won't be the vacuum that is breaking the glass, but the squeezing of the tube in order to seal the interface.

-Dustin
Professional Engineer
Pretty good with SolidWorks

 

[Compositepro]

I have connected vacuum to 1/2" diameter test tubes using a 1/2" Swagelock fitting with a teflon ferrule. This also allowed for 15 psi of positive pressure as well as vacuum.A rubber vacuum hose is the simplest possible method and can work fine. There is some risk of it slipping off if not fixtured adequately.