aminotetrazole
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Glassware Vacuum
I recently asked what vacuum a glassware kit could withstand from a seller on ebay. They responded 0.098 MPa. When I convert this I end up with 735
mmHg, which doesn't seem like it would be able to withstand any reasonable vacuum at all. Is there something that I am missing? Thanks.
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Detonationology
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One atmosphere of pressure is 760 mmHg. If the seller stated that it could with stand 735mmHg, that basically means it can withstand 1 ATM of
negative pressure. HOWEVER, you should never exceed the rating posted, PERIOD! I have never felt comfortable nor the need to exceed ~450 mmHg. If
you seriously need glassware to withstand serious pressures, don't skimp out... buy American. It ain't worth loosing your life over.
[Edited on 1-30-2016 by Detonationology]
“There are no differences but differences of degree between different degrees of difference and no difference.” ― William James
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Sulaiman
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sorry to butt in, but this may be relevant,
I have wondered about this, using the above example of 1 ATM =760 mm Hg
and a rating of 735 mm Hg, implying a minimum absolute pressure of 25 mm Hg.
If ratings are exceeded and a vacuum of say 1mm Hg absolute is used
the stress is only increased by 759/735 = 1.033, a 3.3 % increase in stress
surely the safety margins are greater than this.
Then again, at 1000 ft. above sea level, -735 mm Hg gauge pressure is absolute vacuum ???
So what am I missing ?
[Edited on 31-1-2016 by Sulaiman]
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vmelkon
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Quote: Originally posted by aminotetrazole  | | I recently asked what vacuum a glassware kit could withstand from a seller on ebay. They responded 0.098 MPa. When I convert this I end up with 735
mmHg, which doesn't seem like it would be able to withstand any reasonable vacuum at all. Is there something that I am missing? Thanks.
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That looks weak. Yes, 0.98 MPa = 735 mmHg.
Even a PET plastic Pepsi bottle can handle 3 atm. I'm sure that the glassware should be able to do handle much lower pressures than 735 mm. However, I
have heard of a case of a glass buchner flask blowing because of low pressure.
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