DIY Vacuum & Heat Chamber

[ant...]

Ive built myself a Vacuum Chamber that can be heated too, from a simple pressure cooker pan.  Proper bell jars are too costly for me.

The fittings are removed from the top of the cooking pan and replaced with a vacuum gauge and a cooking thermometer, when the items are placed inside the pan I vacuum out the air to remove air bubbles from the final product, then I stick the pan on the cooker and slowly heat it to the temperature i want 40 to 80c.  Im sure the lack of air inside the pan will restrict the heat from travelling so well, but what heat the product gets from conduction will help the curring process.

In reverse this device could also be used as a small autoclave, if the items were vacuum bagged first then placed in the pan, it could be pressurized and heated.

[usn ret]

Ant, the pictures did not come out!    Pics please 
Cliff

[Bluechip]

Ant..

This intrigues me. I occasionally have dreams of making HV coils but... to get 'em to be reliable, they need to be vacuum impregnated with epoxy or lacquer. I have a vacuum pump of unknown provenance, no idea if it works, so ...

If I may ask, what do you make that requires the Vacuum Chamber.

How do you get the vacuum, and to what pressure (depression? )

Cliff is right, I see no pics. either ...   


Dave BC

[Bernd]

Cliff and Dave,

Here's something that might get you going in the right direction on making your own. It's from my web site. Vacuum Chamber
I have another version with a smaller vacuum pump (refer motor) in the works, but like all good projects it's on the "round-tuit" list. 

I'm sure if you got questions I'll hear from you guys.

Bernd

[ant...]

OK Cliff, you asked for a photo of a pan and here it is.  Taddaahhhh!!!



Bluechip - See that little blue thingy on the valve, its a vacuum tool, that cost me £45 from vacinnovation.co.uk and it runs off the compressor, 90 psi its good for getting the max of -25 on the vacuum gauge (-30 is a complete vacuum and your vacuum cleaner is good for about -10 to 15).  Fantastic little tool and much better than storing another big pump.

That black thingy sticking out of the pan is a digital food thermometer £6 and ive built that alloy holder, which has a 3.5mm hole to poke the steel probe through.

Next I would like to build a vacuum box with a rubber sheet that can be re-used, so i dont need to do vacuum bagging, mine always leaks.  Any ideas if it would work or where i could get the rubber sheet?

[Bluechip]

Ant

Thanks for the info, although the Vacinnovation site seems a bit sparse    . I will have to try my pump. I have a vacuum guage, but it's calibrated in Ins. Water rather than Mercury.

My compressor gives up to 110 PSI,  8 CFM FAD .. is at big enough ?

Dave BC

[usn ret]

Ant, when I was in the Navy more  years ago than I care to reveal, we tested barometricly release mechanisms from aircraft ejection seats using a vacuum box. I recall we used a vacuum pump from a refrigeration service kit.  We  run it to a simulated altitude and do a release to complete the test. The box {6" x 6" x 18"} was aluminum welded together to form an open top container with a rubber seal on the upper lip. We then laid either a very thick piece of glass or plexiglass against the seal,  as the vacuum increased the seal became tighter.  There was also a manual valve to release the vacuum after the test.  Our indicater was an aircraft altimeter so I don't know how much vacuum we actually pulled.  I hope this helps with future designs.
Cliff

[ant...]

Dave - 110psi is more than enough.  The vacinovations site is very sparce but their stocks are large and prices are low, thats why I always go there.

Cliff - That was the first idea i came up with but with a perspex box.  Finding the rubber seals always lets me down.

[usn ret]

Ant,
Something to think about for a seal.  A release agent on the glass/plexiglass top .  Next a bead of silicon sealant on the top/mating edge of the box. Place the glass on the box until the sealant is cured, them maybe a good seal?? 
Cliff 

[ant...]

Cliff

Thats clever, i hadnt thought of that.  Silicone does need air to dry though, so it would need to be a thin layer, and I think i would use a good layer of grease as the release agent.

As it happens i used silicone on the rim of the pressure cooker but even after 12 hours of drying, when I put the lid on and did a test the silicone stuck to the rubber seal.

[usn ret]

Ant,   Don't know if you caught it or not, there is an thread on vacuum pumps/etc at the bottom of composites and plastics.
Cliff


Google is your friend!!! I googled "vacuum chamber plans" , waaay too much info. Data overload. kind of makes my head want to explode!
C

[chillybilly]

A fridge pump will provide a good vacum ,bit tricky to get hold of regards the gas issue ,but if you should suck using the larger pipe into the body the discharge will be the smaller ,if poss make this longer incase the compressor throws a bit of oil out ,try to avoid allowing the comprossor to lie on its side in relation to its mounting points as this can cause issues with oil .

Just incase that helps   

[ant...]

If you go to your local tip, waste dump, they have seperate fridge & freezer container normally.  I asked the guy in charge and he let me at them with my tools, its just 4 bolts and cut the tubes and wires with pliers.  Wish id got a portable generator to test them though.  But they are free and if its no good you can always take it back and try again. 

[chillybilly]

yep local waste place is where you might find one .Some words of caution .

Make sure the gas has been removed from the sytem ,its not so much the possibility of physical injury more the massive legal implications that fridge gas now carries .

Be aware a fridge coompressor is considered hazardous waste due to the oil within  ,rather than the comp itself .Removing it from a waste dump could be percieved as theft by some people .

tips if you do get one ,
would be if you cut the comp out leave as much pipe as you can for you to fit onto .

If you get one from a recently degassed unit ,be aware that the refrigerant in the oil will behave like pop in a bottle if you shake /jolt the compressor ,thus spraynig all over your car on the way home and it stinks!!!

There may be an electrical thermal overload externally mounted on the body ,bi metalic switch job ,these are often the cause of failure to run issues.


As before leave a tallish stack on the discharge side .

Hope that helps ,just dont want anybody to find themselves in a knightmare with the law or the wife ,outside of this i have had much sucess with my fridge based compressors .

[chillybilly]

Also NRV valves in the right way for the respective pipes will help revent any passing in the compressor if things are a little worn