Vacuum transfer

[Revival rum]

Are vacuum pumps used in distilleries for transfering spirits into pressure rated vessels via filters? What would be the pros and cons of such a system?

[MichaelAtTCW]

I don't see or hear of many people using vacuum pumps in distilleries in place of positive displacement or centrifugal pumps.

When cannabis was booming a couple of years ago there was a lot more interest in transferring/filtering via vacuum. Many cannabis extraction laboratory setups started off using vacuum filtration on very small scales. When they wanted to scale up, they assumed they just need to buy bigger vacuum pumps and bigger filters. It usually didn't turn out that way. Most found that it is much better to push through filters with positive displacement pumps than to try and pull through them.

In terms of cons: since vacuum is just the absence of atmospheric pressure, there is a hard limit to how much vacuum you can pull without breaking the laws of physics. The maximum vacuum you can pull is 29.92 in. Hg (or 1 ATM, 1.01 bar, or 14.7 PSI), and a perfect vacuum is very difficult to pull. Most filters are considered clogged at 30-35 psi. So you'll always be leaving more than half a filter's lifespan on the table if you try to pull through it with vacuum. Conversely, even a little G70 pump can push up to 100 psi.

Vacuum leaks are going to be much more difficult to detect than pressure leaks. You can see liquid squirting out of a pressure leak, or see a puddle that you can trace back to the source. Good luck finding a vacuum leak.

In terms of pros: some people like that product never touches the pump when using vacuum, which may be beneficial for safety. Also, many fillers use vacuum, since viscous products will fill much quicker than with gravity, and overflow can be sucked into a secondary chamber to keep levels consistent.

[Revival rum]

Many thanks Michael, It certainly sounds like a non starter!

[MichaelAtTCW]

Sure. BTW, there was a thread a while back that went into further detail on this topic. You'll see that one user in particular did have some compelling reasons for preferring to pull through filters.

As with many things, it can come down to personal preference, though I remain on the "always push through filters" side of the fence, myself — and if you ask people in the filtration industry, they will recommend the same except for specific circumstances.