PRESSURE CHAMBER

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PaulDoug

PaulDoug

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Joined
Mar 2, 2008
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Benton City, WA.
I'm wondering if anyone has made a pressure chamber out of anything other than a "paint pot"? I don't know how to relate to the strength it takes to contain the amount of pressure needed.

The only thing I have thought of so far is one of those heavy duty military metal ammo cases. Coarse than there the challenge of getting fittings for gauges and connectors on it.

Just curious.
 
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Please do not . . . .

Please do not attempt to build a pressure pot . .

I work in the petrochem industry & you would not believe the damage that is caused by a failed pressure vessel. . . There are a lot of considerations when building even the simplest pressurized vessel. Just 10 PSI in a poorly designed container will cause a lot of damage . .

Steve
 
I have contemplated making one as Jeff said it is probably easier and cheeper to buy one. I work for a fire sprinkler company and all our pipe and fittings are rated for 175 psi. But the problem is building it and making it functionable. I also know what all those items cost and even at our cost it is actully cheaper to go buy one at harbor freight. That is the big kicker as well, be very and I mean very careful when pressuring things up!!!!!
 
Slightest bit out of round totally changes how much pressure you can take. Just a little out of round , the pressure will push on the oblong sides of the pot which will squeeze the lid and the pot basically implodes then explodes. I just bought a new one a couple days ago and am waiting for it to get here. My HF pots, the lids are getting very warn because the clamps are digging holes in it and I never cared for the flimsy metal they are made of anyhow. It's almost like a cast iron type steel, it turns to dust if you grind on it. I bought a stainless steel pot, and the clamps attach to big thick fingers that extend out from the sides of the lid rather than having a tiny round screw digging into the rim of the lid. The new pot has a built in pressure valve I think, which would be a good thing because if it is built into the lid it won't leak like those cheap relief valves on the HF pots. Has wheels too. Cost 3 times as much, but I think it will be worth it from a safety aspect and I think the pot will last far more than 3 times longer. The more I use the HF pot the more nervous I get...I did have one blow apart on me a year or so ago and it was not pretty. It did not sail across the room, or blow into shrapnel like a grenade, but it did jump up off the table a few inches and the pot was rather squished, the worst part was all the resin mess everywhere and trying to clean it up as it was setting up and super hot at the same time.
 
workinforwood said:
Someone made one out of a propane tank. Seems easier and safer to just get a paint pot that is already designed for the job.
Click to expand...

Do not fool around with pressure. In the wrong place, at the wrong time, things can go drastically wrong and death can, and often is the result. Maybe not your own death, but someone else nearby ... like maybe one of your kids!

If you feel you want/need to build your own, then get EXPERT advice and/or assistance. Building even a small pressure pot will probably cost you way more than buying one at HF.

Am I trying to scare you ... YES I AM!
 
Just to pile on...
I used to work in a small cabinet shop. I asked about a HUGE hole in the ceiling. Prior to my time there, a water heater tank had been put to use to add capacity for the air compressor. It worked for some years, and then blew up, leaving the big hole in the ceiling to mark the event. It is not only the pressure, but also the cycles of pressurization which can fatigue the materials and lead to failure. The lesson: buy the engineered product, and have one less hole in you or your ceiling.
 
Well good info which is what I was looking for. That is probably why I never see any homemade ones posted here.

Thanks, I'll move on to thinking up some other way to hurt myself.....hmmm homemade tablesaw....
 
sdemars said:
Please do not attempt to build a pressure pot . .

I work in the petrochem industry & you would not believe the damage that is caused by a failed pressure vessel. . . There are a lot of considerations when building even the simplest pressurized vessel. Just 10 PSI in a poorly designed container will cause a lot of damage . .

Steve
Click to expand...

You are right if poorly designed and with air pressure it will blow!

I have build many pressure vessels and it is save if you use HYDRAULIC PRESSURE and not air. ( Pump a fluid) I have gone up to 9000 PSI and the worse that can happen is that it would sprung a leak but it would not explode as long as there is NO AIR in it. Simple physics, a fluid can not be compressed!

The big vessels I am using for stabilizing is build by a Company that specialize in building pressure vessels and the cost is around $12000-00 for a vessel. Not cheap but save.
 
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The only correct way to build a low pressure pot (under100psi) is with sch 80 steel pipe and weld flanges. This is the same stuff used in boiler applications. The welder needs to be a certified pipe fitting welder who can weld pressure vessels, now all that being said it would cost more for material and welding than to buy the proper unit unless you were a pipefitter. You would have to weld in thread-o-lets for pressure relief and gauges but it would hold and work well. Bear in ming there would be 8 3/4 in bolts clamping down the flange to seal it.
 
Just to chime in a thought but since doing one out of a HF paint pot does require mods how about mod'ing a pressure cooker?
 
Good friends, why play around with your future and possibly the life of anyone that may be near by.

Pressure pots are built to take the limits posted by their manufacturer. These things DO NOT cost anything like what it would cost if a homemade one failed and someone were to be injured, or your shop/home be damaged. Then you would be in serious trouble with SWMBO.

It just is not worth it in my book to even attempt to make one of the size we need to do pens. And just imagine the arguments from family members or friends that would never let you forget that they, "Told you it would hurt you!"

Now, it is completely different if one is in the business and doing pressure treatment on the professional level. Then by all means have one built correctly such as Constance has done, and others, and then you can write off the expense and make it worth while over a period of time.

A pressure cooker .... not in my head to even attempt it. These things are for an entirely different use of pressure. Now I have known folks that have used these cookers to steam treat their 'green' blanks and they have had great success. NEVER EVER DEFEAT THE PRESSURE REFLIEF VALVE on anything. It is there to save your life. If this little valve is not present, or it is not working properly, DO NOT USE THE DEVICE. You are just playing around with a source of some very serious injury and pain to come. :eek:

... Exiting soapbox now stage left ... :umbrella:
 
As I said before the pressure cooker was just a thought (sort of thinking out loud) On a another note what is the difference between the HF 2.5 gal and 5 gal besides volume. The 5 gal looks to be rated for higher pressure and currently per the web site are the same price. The only one I have seen in store is the 2.5. So is there an advantages that would swing the purchase of one over the other?
 
Paul, Pressure cookers do not work the lids buckle or the seals blow out. I've seen it tried before. You are also dead on in your thinking of why you do not "See" homemade ones. It is not that they where not made. they are just short lived. Believe it or not it took several years for the present ideas of pressure casting to be developed. All over much discussion about is it safe and all that. many false starts happened, a couple of attempts that met with a big puff if not a bang became evidence that it should not be played with. The systems that are in use today came from much dangerous trial and error. The Paint pot has been put to some extreme tests and has proven to be safe. Still there has been at least one case of an explosion that by grace did not result in an injury. but still even what we do today can fail. This really is on place that I say do not try for cheaper, easier, or faster. Play with it and improve it, but only with the knowledge that has been discovered before you. This really is dangerous stuff.
 
"Lazyguy" ... not beating you to death here with your idea on "making your own", just continuing to add my $0.02 worth of warning ideas on the issues of the dangers that can sometimes come from doing it yourself.

In response to your 2.5 gallon vs 5 gallon size I think that one big advantage would be the ability to do longer stock, not just more in quantity (obvious), but maybe a taller pepper grinder, handles, etc. In this case it would definitely be true that "size does matter!" :cool:
 
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