Chamber vacuum sealer caution

[etpm]

I love my chamber vacuum sealer but ran into a little problem today that I shoulda known better about. I was sealing some broccoli soup and it was warm. Not hot, just warm. Too warm as it turned out. As the pressure dropped the soup started to boil and it boiled so vigorously that it boiled out of the end of the bag and made a mess inside the sealer. I know that lowering the pressure also lowers the boiling temperature but I still made the mistake. So I cleaned up the sealer, cooled the bags in the fridge, and they sealed fine, no boiling. I won't do that again. Anyway, just thought I'd pass on my mistake.
Eric

 

[RobertN]

Reminds me of the time someone put a bumblebee inside the Hitachi Scanning Electron Microscope at work. As soon as the vacuum pumps came on it exploded and made real mess of the column. If I remember right, that system ran at 10-5 or 10-6 torr.

We used to do this for demonstrations when kids tours etc. But we used a well desiccated bumblebee at a little less vacuum than what we used doing failure analysis on silicon chips. This particular person put a freshly dead, not desiccated be in. Needless to say, they didn't use the SEM bug demonstrations again.

 

[etpm]

Years ago I made some vacuum chambers for one of my customers. They were two feet in diameter and were prototypes. They were going t o be pumped down to some micro torr vacuum. They had an acrylic lid. They asked for a lid that was 1.5 inches thick. I did the calcs on deflection of the material and told the engineer that it would deflect too much and probably break the seal. They said 1.5 inches was enough. It wasn't, they went to 2 inches thick. I still have a large piece of 1.5 inch acrylic, enough to make 3 more lids, sitting in my plastic stock rack.
Eric

 

[CalG]

My professional career was wrapped in vacuum technology. (I have a high vacuum, Physical Vapor Deposition plant in my down stairs laboratory ;-)

A vessel of water placed in a high vacuum chamber will boil until it freezes!
All at room temperature!

The water is hard on the pumps though.


Clean Dry and empty is the motto ;-)

 

[CalG]

Years ago I made some vacuum chambers for one of my customers. They were two feet in diameter and were prototypes. They were going t o be pumped down to some micro torr vacuum. They had an acrylic lid. They asked for a lid that was 1.5 inches thick. I did the calcs on deflection of the material and told the engineer that it would deflect too much and probably break the seal. They said 1.5 inches was enough. It wasn't, they went to 2 inches thick. I still have a large piece of 1.5 inch acrylic, enough to make 3 more lids, sitting in my plastic stock rack.
Eric

Even a perfect vacuum can not exceed 14.7 pounds per square inch pressure differential.

Vacuum being as close to nothing as humans can produce.

 

[CalG]

I'm looking for a "low tech" vacuum pump that can take a heavy water load.

Something to accelerate the boiling process of maple sap to syrup.

It's something well outside of my normal.

Dairy pumps are too costly. Maybe I'll run across one some day however.

 

[etpm]

Even a perfect vacuum can not exceed 14.7 pounds per square inch pressure differential.

Vacuum being as close to nothing as humans can produce.

Yeah, that's why micro torr means almost nothing to me in practical terms. But I'm not doing vapor deposition, I'm just vacuum sealing bags of soup, chicken broth, roasted chicken, sausages and the like. But I know better and still boiled soup in the sealer.
Eric

 

[etpm]

I'm looking for a "low tech" vacuum pump that can take a heavy water load.

Something to accelerate the boiling process of maple sap to syrup.

It's something well outside of my normal.

Dairy pumps are too costly. Maybe I'll run across one some day however.

There are oil less rotary vane pumps that pull a pretty good vacuum and can tolerate a lot of water. I just looked on eBay and say one for 75 bucks and another for 50 bucks. I guess you need to figure out how much air and vapor you need to move to decide on how big of a pump you need. Remember, if you pull a significant vacuum on a large container you risk collapsing it. That would be fun, hot maple syrup jetting all over the place.
Eric

 

[2LaneCruzer]

When I worked in the lab, we used vacuum to freeze dry (lypholyzing) microbial specimens. Seems they keep indefinitely. Also spent several years on an electron microscope; as I recall, we used vacuum to make carbon film sample holders for the microscope. Those were the days...1980's...the electronics filled one small room.