Rule of thumb of how much vacuum does lab glass stand?

Sometimes I have to apply vacuum to all kind of different borosilicate glass equipment like:

• liebig condensers

• fractional distillation apparatus

• spiral condensers

• chromatography column

• and so on...

While I know that a thick walled round bottom flask will pretty much stand any vacuum my vacuum pump can produce, I am not so sure for something as fragile as a spiral condenser.

Is there a kind of rule of thumb how much mBar thin walled glass equipment like spiral condensers or chromatography columns can stand without risk of implosion?

• The risk of implosion is always here, even properly certified glassware may get a tiny crack and implode. Always assume that the risk exists. Be especially suspicious with flasks above 100 ml except for very thick-walled ones for vacuum filtering. That said, there is no much difference from 0.01 kPa and 10 kPa as the outside pressure is 99+ and 90+ kPa respectively (10% difference), so if a piece of glassware can be evacuated by water ejector to meaningful degree, it usually can withstand any vacuum within. – permeakra Jan 29 '18 at 21:14
• That said, you should be suspicious of large flat and almost flat surfaces and sharp angles.Small tubes are fine. Glass condensers are usually meant to be used with vacuum. – permeakra Jan 29 '18 at 21:14
• How can you use a chromatography column "in vacuum"? Are you meaning to clean/dry it? – Alchimista Jan 30 '18 at 10:18
• Scratches and cracks have a much larger effect on strength for internal pressures than for external pressures, due to the nature of compression strain verses tensile strain. – Max Power Apr 18 at 22:16

The basic rule is that the stress on an evacuated glass vessel is pretty much the same at 0.01 mbar (oil pump), 1 mbar (membrane) or 25 mbar (water jet) absolute internal pressure. 0.99999, 0.999 or 0.975 bar $$\Delta p$$ to the outside make very little difference if the thing goes pop.