DIY Pressure test vessel?

[don Francisco]

If you decide to build your own vessel, be sure to hydro test if at at least 1-1/2 times the desired working pressure. The safest way to do this is to fill the pressure vessel with water, so there is an absolute minimum air space, since the potential energy is proportional to the pressure and volume of the compressed air. Water being noncompressable in the ranges we're talking about, it doesn't accululate explosive energy. The vessel should be tested while submerged in a tank of water or swimming pool during the test to attenuate any burst energy & slow down or capture any schrapnel. Lastly be sure to install a safety relief valve reliably set at about 10% above the working range, or no more than 3/4 the proven test pressure.

You may think this is overkill, but compressed air has tremendous potential energy. An auto tire bursting when overinflated or if defective has enough explosive power to kill a man. That's why in some countries, inflation cages are mandatory safety devices where new tires are mounted commercially.

I am not saying that you shouldn't build your own pressure vessel, just that you should go about it knowing, and properly managing the risks. Even then, you're playing with dynamite.

 

[Stu S.]

Even then, you're playing with dynamite.

Mount a plastic plate 8 inches in diameter on a cylinder and pressurize to 125 psi?

That's over 6200 pounds of force on that plastic, and then you are going to put your face up against it and look in?

Don't do that.

 

[dumpsterDiver]

I appreciate all the advice....Anybody else.... I just need to take the housing to depth (in water) leave it there for a little while and release the pressure. I do not need to see inside the test vessel during the test.

 

[NorthWoodsDiver]

the appropriate thickness of lexan and attached to the proper container poses little threat but the key here is "proper".

if this was my project I would take a piece of 8" or 10" steel pipe say 3/8" wall thickness and machine both ends, one flat and the other with a good bevel. I would than take a piece of say 1/2" steel plate that has been media blasted and weld to the beveled end with a dual shielding wire-feed welder. this procedure will insure proper weld penetration and true fusion without any contamination. if you need top the welding process at any time I would grind the stop/start point out a bit to insure a true air tight weld. Just because its me I would do 3 passes around the device to insure a proper weld seal.

I would then make a ring or donut of sorts out of 1/2" plate and machine 1/4" 20 holes every 1.5 inches all the way around. this ring would then be installed on the outside of the chamber flush with the top and welded like the bottom.

I would than take a piece of polycarbonate lexan at least 1 inch thick and machine it into a circle and drill the appropriate holes to line up with the other ring we made earlier.

I would than take a piece of 1/4" steel plate and cut another ring to work as a sort of washer on top of the lexan with the appropriate holes in it. this ring would also have spokes spanning across like a wheel in say 4 places. this obstructs view to some degree but offers yet another form of safety.

Now I would get some 1/4" X20 threads per inch bolts about 2" long (grade 5 at least or 8 is better) and weld some 1/4" cold roll round bar to the heads of each bolt to make a "T" handle.

This thing would be big and heavy but would be "bulletproof" to a certain degree. Using products like lexan and Grade 8 hardware and DOM tubing and Hardened steel plate would make everything safer but the hardened materials are harder to machine so settling with heavier materials of a "softer" more machinable property would be much easier to work with.

I would assume you would also need an Oring seal on the lexan which would require another machining process but finding the proper size O-ring would be difficult.

A project like this would take me at least 8 hours to finish as its very labor intensive however you have the ability to make any type or size chamber you want.

if you need a larger chamber it is feasible to roll the steel necessary but the thickness of the metal to be rolled is severely limited. A square or rectangular tank could also be produced and would likely if done properly hold the pressures necessary for this project but would require far far more labor and materials.

I fully intend to make something like this in the future and you can be sure my results will be posted online.

 

[don Francisco]

Dumpsterdiver- read my post re: pressure cooker. It's ready made, cheap, reliable & safe. You couldn't build anything for less than a househiold pressure cooker costs. BTW I made a slight error. I rechecked my Sensus Pro data & found I've dived the unit to over 400' at which point the rubber safety valve blew out and the Sensus recorded an ascent of about 5,000'/min.

 

[pp-1-3-5-7-9]

I appreciate all the advice....Anybody else.... I just need to take the housing to depth (in water) leave it there for a little while and release the pressure. I do not need to see inside the test vessel during the test.

Not sure what size of the object you have intended to test it, if it's not a big one then you can try this one.

ALLOY PRODUCTS APC 1Gal T316L Stainless Pressure Vessel - eBay (item 320249979995 end time May-13-08 13:14:47 PDT)

 

[dumpsterDiver]

Dumpsterdiver- read my post re: pressure cooker. It's ready made, cheap, reliable & safe. You couldn't build anything for less than a househiold pressure cooker costs. BTW I made a slight error. I rechecked my Sensus Pro data & found I've dived the unit to over 400' at which point the rubber safety valve blew out and the Sensus recorded an ascent of about 5,000'/min.

Yes thanks. I had no idea that a pressure cooker could contain that kind of pressure. I always thought it was like one atmosphere or something.....

 

[Randy43068]

Or you could engineer a tank which when 1/2 full could submerge your item.
rig it with a way to raise your item being tested out of water.
Perhaps a screen or hardware cloth above water level.
I'm picturing a 10 gal fishtank with a pce of lexan glued to the top with an O-ring sealed hinged access door on one side.Fill tank to just under grate,install item to be tested,invert tank submerging test item,perform leak test.
Just for safety's sake, how about pulling a vacuum on the gas/air portion of the tank.
This way when a leak is shown it will be gas/air escaping from tested item, not water entering it.This way one could also test for leaks after battery changes on computers/dive watches.
***If Leak Occurs During Tests,One MUST Invert Test Tank Before Equalizing Pressure In Test Tank.***
Hope this helps you out

this sounds like a big accident waiting to happen.

 

[Randy43068]

We're only talking about 20-30 PSI max. MAX.

 

[viceroy]

Mythbusters from Discovery channel had a nice pressure tester which they used on a few myths.

Seemed pretty simple to make too!