Boiling Water in a Vacuum at Room Temperature

My Vacuum pump and chamber arrived!

I went for a Bacoeng 3 CFM Single Stage Oil Filled Rotary Vane Pump (BA-1) and a slightly more expensive tempered-glass-topped 6.8L vacuum chamber.

I could have got the slightly cheaper perspex topped vacuum chamber, but this wasn’t that much more expensive. The glass one is safe against various solvents which will react with the perspex and crack it. I also thought having the valve in the metal chamber rather than drilled through the perspex part was more sensible.

The glass is pretty thick!

Setup

The first part was relatively easy: fill the pump chamber with the supplied oil. I also installed the valve into the chamber and hand tightened the nut to attach it.

It was a little unclear on what to do for the pressure gauge from the instruction sticker on it: apparently, its meant to measure the pressure in the chamber relative to your local pressure. It is not supposed to be completely sealed. I figured out what they probably meant was simply to puncture the rubber seal on the gauge with a pin.

Testing

I wanted to verify it could achieve and hold vacuum first, and it seems to be able to do both:

Messing About

Just for fun, I tried sticking a fizzy drink in there to see if it would remove the bubbles. It did so, but it looked like there was far more gas in the drink than I expected. I realised what was actually happening was the water was boiling in the vacuum!

Thoughts

It looks great for my purposes: I didn’t see any of the problems some people have reported with this range, such as inability to achieve/maintain vacuum, or the steel of the chamber itself deforming under pressure (or…. lack of it I guess)!

I did notice one thing though. After a few hours playing around with water, the oil in the pump looks cloudy: kinda like an oil/water emulsion:

I guess the oil is affected by whatever you remove from the vacuum chamber, and I’ve been pulling water vapour while messing around: this explains why people say you need to change the oil regularly. I’ve got some more vacuum pump oil on order and will drain the pump completely when it gets here; its probably not great to have water hanging around in there.