Help me find a pressure/vacuum tank!

[Picard Kills Kirk]

I am looking into getting some sort of tank/canister that I can create a vacuum in, then later pressurize to assist in dyeing woods.

I am looking in the 1-10 gallon size range.

If it helps, what will basically happen is that I will put the wood in the container, shut it, and create a vacuum. From there, I would like to insert dye into the container through a valve losing as little vacuum as possible (the option to turn the vacuum back on at this point would be nice in case I mess up on the valve). Then after a while I would like to release the vacuum slowly and pressurize the container for a little before releasing the pressure and opening it up.

I have been googling like crazy but I keep getting industrial size tanks or vacuum cleaners for carpets.

Maybe I am not calling this tank the right name? Any help would be greatly appreciated.

[HongKongFooey]

Is this anything like you're looking for?

[Picard Kills Kirk]

Ah yes, it is! Apparently "pressure pot" is the term I was looking for. You either already knew exactly what I was looking for, or your googling abilities are legendary. Either way, thanks!

[FE3O4ENAIL]

How about a used pressure cooker? Cheap, strong, and available at second hand stores.

[Picard Kills Kirk]

That's an interesting idea. I've never used a pressure cooker before (for anything). I forgot to mention that I'm looking in the range of 50-80 psi. What type of pressure do they use when cooking?

[Q.E.D.]

Not even close. Pressure cookers typically operate at about 15 PSIG max.

[HongKongFooey]

Originally Posted by Picard Kills Kirk

I forgot to mention that I'm looking in the range of 50-80 psi.

Are you sure you need that much pressure or is that just an estimate for your process?

[HongKongFooey]

Originally Posted by Picard Kills Kirk

You either already knew exactly what I was looking for, or your googling abilities are legendary.

Hah, I wish it was the latter but I had a good feeling that was what you had in mind.

I see you're planning to dye the wood so you will need the 50 - 80 psi range. Somehow I missed that part of the OP.

[Picard Kills Kirk]

Originally Posted by Q.E.D.

Not even close. Pressure cookers typically operate at about 15 PSIG max.

Man, if only I knew a real life Tim Allen...

[Gbro]

An outdated 30 lbs fire extinguisher?
Don't know how much of a vacuum it would handle but they are capable of that kind of pressure.

[Santo Rugger]

Originally Posted by Picard Kills Kirk

Ah yes, it is! Apparently "pressure pot" is the term I was looking for. You either already knew exactly what I was looking for, or your googling abilities are legendary. Either way, thanks!

Did you get what you needed? If not, I can ask around; plenty of enclosed explosives testing chambers are designed for much higher PSI ratings than you're looking for. Snap-On makes some chambers I've seen used, for example.

[Santo Rugger]

Okay, I'm an idiot. Turns out, some joker epoxied Snap-On buttons onto a few of our tanks. I've been getting shit for asking who made the other ones all day. Turns out, they're all made in house. Sorry I couldn't have been more help, but hopefully you got as much of a laugh out of it as those guys did.

[Projammer]

You didn't mention the dimensions of the wood you intend to treat, but a trip to your local plumbing supply will probably turn up everything you need.

Some pipe with screw on caps. And caps of course. Valves and fittings for vacuum and dye entry.

If you need large diameters you might be able to use PVC to save costs.

[FE3O4ENAIL]

Originally Posted by Q.E.D.

Not even close. Pressure cookers typically operate at about 15 PSIG max.

Yes, looking at mine the gage goes into the red zone above 20 psi. Sorry.
You could also try paint pots that use a seperate spraygun. The one I have shows it will take 60 psi air.

[Zany Zeolite Zipper]

Originally Posted by Projammer

You didn't mention the dimensions of the wood you intend to treat, but a trip to your local plumbing supply will probably turn up everything you need.

Some pipe with screw on caps. And caps of course. Valves and fittings for vacuum and dye entry.

If you need large diameters you might be able to use PVC to save costs.

It's probably not a very good idea to monkey around with haywire solutions when you are looking at 80psi. Even on a little three inch pipe you have 565lbf, or 2.5kN (on the threads), lets assume a 300g end cap, that force can produce a 8.3km/s/s of (F/m=a) acceleration. Assuming, 0.01s rupture, and final velocity is (v=at) 83m/s, with a kinetic energy of (KE=1/2m*v*v) 1.0kJ, which Wiki says is edging into rifle territory. So please don't cobble together a solution.

Everybody in construction knows a friend of a friend who swears that they saw a split rim tire go through a cinder-block wall because it was put together incorrectly. And then there is the guy who lost a finger/hand/etc when he though he found a pressure leak and put his hand in front of it.

Even small pressure vessels are very expensive, say $20,000* for a little one (0.5m diameter, 1.4m height), and you can double that if you want stainless steel. *Based on an equipment costing text.

[zut]

Originally Posted by Picard Kills Kirk

Ah yes, it is! Apparently "pressure pot" is the term I was looking for. You either already knew exactly what I was looking for, or your googling abilities are legendary. Either way, thanks!

I only gave that page a cursory glance (so perhaps this is a non-issue), but if you buy some sort of pressure pot, make sure it's rated for vacuum pressure if you're also using it for same. Pressure vessels with externally applied pressure (vaccum tanks, in this instance) are susceptable to buckling, which is not an issue for internal pressure pressure vessels. The vessels on the linked page look pretty stout, but internal pressure rating is not necessarily a good guide for vacuum rating. As a cite, I offer a 2-liter pop bottle.

[Zany Zeolite Zipper]

Of course Mythbusters got a regular hot water heater to over 330psi. But I am not sure you want to do that in your garage.

Then there is this fun video of a tank car implosion.

One of my profs likes to tell a story about how he destroyed a $20k piece of lab equipment checking for leaks. He decided to put it under a vacuum, and wait and see if the pressure increased, but instead it broke because it couldn't tolerate low pressure.

[Magiver]

Originally Posted by Zany Zeolite Zipper

Then there is this fun video of a tank car implosion.

That looks exactly like a Mr. Science experiment where he heats water to steam in a 55 gallon drum, seals it and then sprays cold water on it.

With the crowd around the rail tank it looks like a deliberate event.

[Projammer]

Originally Posted by Zany Zeolite Zipper

It's probably not a very good idea to monkey around with haywire solutions when you are looking at 80psi.

I wouldn't have suggested it if I didn't remember having used PVC pipe with a rating of 200psi stamped on it.

So I'd recommend checking the rating stamped on the pipe itself.

[HongKongFooey]

The problem is that pressurizing the pipe with compressed gas isn't the same as pressurizing with water which the PVC pipe was made for. It's not my area of expertise but AFAIK PVC shatters when it fails under pressure whereas ABS would split. That's not to say it would fail when pressurized to 80 psi just a reminder to the OP to be aware of the potential failure points which could also become projectiles as Zany Zeolite Zipper mentioned. Anything you thread into the pipe (end caps, gauges) needs to have threads rated for your working pressure and introduces a weakness in your system. No matter what method you use consider installing a pressure relief valve.

[Rick]

Originally Posted by HongKongFooey

The problem is that pressurizing the pipe with compressed gas isn't the same as pressurizing with water which the PVC pipe was made for.

I'm gonna have to ask for a cite on that.

[HongKongFooey]

Originally Posted by Rick

I'm gonna have to ask for a cite on that.

Certainly:
Here's one from an OEM

They also caution against using their product to store or convey air or other gases or failing to vent trapped air. It is increasingly common for such practices to void any warranties. Many accidents have been reported as a result of air testing or trapped air. Most manufacturers of plastic pipe and fittings have had to investigate field failures caused by either air testing or trapped air.

osha

An employee in a Texas plant was injured recently by a rupture in a PVC compressed air line. Plastic projectiles from the point of rupture caused lacerations of the employee's hand. This is noteworthy because the Plastic Pipe Institute, in its Recommendation B dated January 19, 1972, recommends against the use of thermoplastic pipe to transport compressed air or other compressed gases in exposed plant piping.

The state of Washington has notified the public that PVC pipe is not to be used in compressed air systems

Yahoo! Answers

PVC-U (Polyvinyl chloride, unplasticized) - Highly popular due to its availability and relatively low cost. PVC pipes are available in a wide variety of sizes and pressure ratings. In industry, however, they are illegal for compressed air applications—if they are damaged under pressure the plastic can fail explosively.

ABS (Acrylonitrile butadiene styrene) - Another popular plastic piping material, more expensive and less common than PVC but available in the same sizes and pressure ratings. Unlike PVC, it is used in compressed air systems as it splits rather than shatters on failure. It also has a greater temperature tolerance (-40°C to +80°C compared to 0°C to +60°C for PVC).

ETA: It's illegal here too by the way but happens all the time on various sites especially in mines where they are exempt from many of the provincial health and safety regulations.

[mga405]

Hi, I new to this forum, but I do this to stabilize wood to make knife handles. i use a 2 1/2 gal pressure pot originally made to be used with a paint spray gun. I have it hooked up with pressure line, vacuum line and use a metering tube with a valve to let in epoxy resin/ and or dye. Works great up to about 100psi pressure and 20+ hg vacuum.

[mga405]

I forgot to mention-I got mine at Harbor Freight, new for under $100.

[CutterJohn]

Originally Posted by Rick

I'm gonna have to ask for a cite on that.

Pipe failure with a gas is much more catastrophic than with a liquid, as the gas can expand far, far more. This makes the pipe fragments fly all over the place. When the same piping is burst with a liquid inside, only a small amount of liquid needs to escape before the pressure is equalized, as liquids compress only a very small amount when under pressure.

Its a concern over pipe failure.. So long as the pipe doesn't fail, then of course it would perform just fine with a gas inside. Its just unsafe to do so.

[CutterJohn]

oh, and http://www.graco.com/Internet/T_PDB....ingAccessories



Drat.. it seems I was beat too it.

[CutterJohn]

Originally Posted by mga405

I forgot to mention-I got mine at Harbor Freight, new for under $100.

This one? http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=93119

[mga405]

That's the one 2 1/2 gal for 79.95 and a 5 gallon for 99.95. i can send a you a pdf file that showsn step by step what I did with pictures showing steps.