Vacuum Chamber Seal Ideas

[snowman]

I have a piece of Schedule 40 14" PVC pipe that I need to make in to a vacuum chamber. One end will be capped with a traditional 14" cap. The other end is the trick. I had originally planned to use a 14" PVC bolt up flange, but holy crap are they expensive. The actual cap will be a flat piece of 1/4" stainless steel. I just need some sort of seal that holds up between the PVC and the steel.

I'm really pretty flexibile in how this is going to be done. It will be exposed to dilute acids though, which makes choosing the sealing parts a little trickier. I've considered buying a piece of polypropylene as a cap, cutting a groove in it for a large viton O ring, then tie rodding it to the bottom to create tension.

Any other ideas?

I end up in similar situations trying to seal up makeshift vacuum chambers for controlled atmosphere metallurgy.

 

[Milland]

[Cranky old man hat on] Any plans for a protective cage around this chamber? PVC can fail sudenly, and a chamber that size under vacuum wouldn't be fun.

 

[Peroni]

One place I was at years ago had me making quite a few vacuum chamber seals from glass filled teflon.

 

[GregSY]

Welll...you don't give any details on how much vacuum you plan to pull or if the end needs to be transparent or not or how much temperature this whole thing will see....but I have a vacuum pot that has a clear plastic end of about 3/8" thickness. It is sealed by what looks to be a poured/flowed silicone goo-goo.

You could also use an o-ring instead of goo-goo.

Or make one out of aluminum plate if you don't need to see through it.

My lid has no mechanism for keeping it in place. I use some zip ties to keep it together for storage, but otherwise the vacuum is all it takes to stay secure.

Mine is not exactly like the one shown in this ebay add, but similar. I will note that these vacuum chambers are sold under the guise of 'degassing' and 'wood impregnation' and 'essential oils'. But in reality, they are sold by and large for people wishing to produce their own hash oil. Those rascally dopers!

2 Gallon Stainless Steel Vacuum Chamber kit Degassing Urethanes Silicone Epoxies 637509414047 | eBay

Multi-application - suitable for degassing urethanes, silicone, epoxies, stabilizing wood, filling molds, extracting essential oils from organic materials, etc.. Strong and durable stainless steel container with chemical-resistant silicone gasket.

www.ebay.com

 

[snowman]

PVC is rated for every bit of vacuum I'll be pulling without concern for failure at room temperature. I've used it extensively and never had a problem. This chamber is just being used as a liquid receiver.

The extent of the vacuum will be that which can be measured with a simple 0-30" Hg gauge. It's being pulled with a diaphragm pump or water venturi aspirator / eductor.

I can do a cast silicone if I need to, but frankly, they don't hold up well.

And yes, there is a lot of surplus technology coming off the weed industry. Unfortunately, around here, they've also filled up every available bit of industrial / commercial space that could normally house a small startup to grow weed.

 

[Thunderjet]

We use a 3/16 cross section buna N O ring.

McMaster-Carr

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We can pull around 3 atmospheres with it. You will need to have a retaining groove and crush it down around 20%.

A cap made of 6061 aluminum should do fine.

 

[Pete Deal]

I have a small chamber, 4” pipe, that I used an expandable pipe plug to seal the one end. Maybe not practical in 14” but I’d look what can be had.

 

[Scottl]

An old pressure cooker can be used to make a vacuum chamber. All you need to do is put your vacuum hose on the spigot where the regulating weight goes.

 

[snowman]

The goal is to be able to drop a 5 gallon bucket right into the PVC, then it'll collect the fluid being transferred. 5 Gallon buckets by themselves don't work for vacuum transfer as the walls cave in.

 

[DavidScott]

The easy way is a sheet of 30A rubber between your plate and pipe end, perhaps glue it to the plate. I have done the o-ring cap you describe with the o-ring sealing the id of the PVC pipe but it was a pain to remove. I would use PVC vs polypro though. You could have both your suction and vacuum hoses in the lid so they get out of the way when you pull the lid.

Why won't a wet shop vac work?

 

[Pete Deal]

Seems like an expensive project in PVC. Below is a vacuum chamber I made to catch fluids. It's 6" Sch 40 pipe but could be pretty scaled up. Hard to see but it has a ball valve drain.

 

[GregSY]

You could probably make a wagon wheel-shaped stiffener for the 5 gallon bucket that would prevent it from collapsing.

 

[EPAIII]

I guess I am a cranky old man too because that was my first thought.

PLEASE DO TAKE PRECAUTIONS.

As far as the end is concerned, I would just use another end cap. They are thick enough to drill and thread for pipe fittings. Then Teflon tape to seal the threads.

I have found pipe thread taps at local pawn shops literally for pennies on the dollar. Just need a few minutes in the rust removing stuff and they were good as new for all but NASA flight hardware.

[Cranky old man hat on] Any plans for a protective cage around this chamber? PVC can fail sudenly, and a chamber that size under vacuum wouldn't be fun.

 

[neilho]

The goal is to be able to drop a 5 gallon bucket right into the PVC, then it'll collect the fluid being transferred. 5 Gallon buckets by themselves don't work for vacuum transfer as the walls cave in.

Yup, they sure don't. That's been a problem for us too. We fill 5 gallon pails using vacuum transfer and drop the pail into 2 empty stacked buckets for filling. Works for us, but you may be drawing more vacuum. We're transferring vinegar, so the vacuum levels are low and transfer speed isn't critical.

Dunno what you're packing, but UN approved shipping buckets have thicker walls - .110" or so vs .078" for foodgrade buckets.

How would you deal with overflow?

 

[BoxcarPete]

For mildly acidic aqueous solutions, EPDM is your best option. You can use viton as well, but on an o-ring the size you are looking at the price difference will be relevant down to a single piece.

You want the permanently capped side down, and the removable cap up? Just groove the end of your PVC pipe for a -279 (cut the groove 0.180~0.200" wide and .110~.120" deep, leave a bit more meat on the ID than the OD, reinforcing the ID with a ring is recommendable as well) and stretch that bad boy in there. All you'll need to do is set your stainless plate on top and start pulling vacuum. Once your vacuum gets somewhere around 3-4 in Hg, you should see full squeeze on your o-ring. The weight of the plate itself should be enough to get you started.

 

[boslab]

I’ve used the 2 pack urathane stuff for a chamber seal, even silicone rubber worked ( lube one face with washing liquid to stop adhesion) sausage bags of nitrile ok but became detached easily.
Even leather was used in times gon by ( I saw one set of instructions with stuff like guttapercha whatever that is!
Used a rubber Bunsen tube on one thing, worked when greased with plumbers silicone grease ( cheaper than £60 tubes of DOW high vacuum grease )
Mark

 

[Conrad Hoffman]

I've messed with flat seals and they tend to suck in under vacuum. Better off with an O-ring in a groove.