Pump for evaporating IPA off of small rope

[cmsileo]

Hello All,

I am trying to develop a process to improve the drying of a medical braid we produce. The braid is dipped in in water, then in IPA. We have a vacuum dessicator and would like to use it to vacuum dry the braid by reducing pressure causing any IPA or water to boil. Based on the room temperatures, we would need to bring the pressure down to around 15 mmHg to be sure we got everything boiled off.

I have been looking around for various pumps but am not very familiar with the different types and which are capable of pulling in vapors and holding a vacuum in this environment.

http://www.eng-tips.com/threadminder.cfm?pid=407#

Does anyone have any good recommendations for a reasonable pump to use or process tips?


Thanks

 

[btrueblood]

A decent 2-stage mechanical vacuum pump will easily reach 15 mmHg, and will be the cheapest and most reliable pump in my opinion. McMaster-Carr calls them "extreme vacuum pumps", Cole Parmer has similar pumps but you have to sort through them to find the ones capable of that high a vacuum level. Research the differences (wikipedia is your friend here_ between inHg (typically used when quoting gage vacuum, i.e. vacuum relative to atmospheric pressure, rather than absolute pressure), mmHg, Torr, microns. Your 15 mmHg is presumably an absolute pressure, approximately equal to 15 Torr, 15000 microns, or 2 mbar, or 29.5 inHg gage. Generally, that level of vacuum does not cause much concern for pump oil back-streaming assuming you get a good grade of vacuum oil and keep

Include a source of radiant heat (like an incandescent light bulb) in the vacuum chamber, in order to replace the heat lost by the rope due to heat of vaporization of the alcohol, this will speed the drying somewhat. Also, multiple vacuum cycles with dry air backfill in between, may show a faster drying time than a long single vacuum cycle. This is because the backfilling air re-warms the object being dried by convection heat transfer.

 

[btrueblood]

argh. Fast on the buttons again today.

"...oil back-streaming assuming you get a good grade of vacuum oil and keep ..."

should have been "...and keep it clean by changing it on a regular basis."