Building a Transparent Pressurize cylinder

[Akimbo]

@BRT

Don't confuse pressure rating and safe working ratings. Aside from the plastic projectiles, PVC is especially subject to accidental impact damage... bumping it while moving a ladder or piece of lumber in your shop for instance. There is a reason that OSHA prohibits it for above ground gas use:

OSHA Hazard Information Bulletins, The Use of Polyvinyl Chloride (PVC) Pipe in Above ground Installations

The noteworthy bit is:

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.

It probably won't kill you but it could easily disfigure and blind.

 

[northernone]

Having blown up a fair amount of pipe with various potato cannon designs in my childhood I have a hearty respect for shrapnel if the actual tube fails.

Fortunately my joints were the weakest link and more often I'd just blow off an end cap and scare the faithful dog. After he lost half his whiskers to a misfire on combustion based model he took to hiding under the porch. Proving the superior wisdom of man's best friend.

I'd be nervous with an air bell in the pressure chamber if approaching liquid service pressure in case of a blow out. No first
hand experience of this though.

Cameron

 

[Rred]

Polycarbonates (i.e. Lexan) tend to range from 10x to 100x stronger than acrylics (PlexiGlass) but there is a wide range in each material and more from each maker.

Depending on what you are looking for, I would suggest finding a SOURCE that carries "pipe" in the size range you anticipate using, and then ask that source where you can get the technical specs for their material. Every plastics maker has specs online, but once you move from "sheets" to extruded pipe, it will become harder to find any source. And when you want structural, not just ornamental pipe, harder again. You'll probably have to special order 8' pieces of it unless you find a really large mail-order source.

Then you'll have to consider the ways to fabricate end caps or seals.

You might also want to consider building a larger cube out of 1/2" polycarbonate to go around the whole thing, so that if it rapidly unassembles itself, the cube catches all the debris and contains the damage.

 

[kelemvor]

You might also want to consider building a larger cube out of 1/2" polycarbonate to go around the whole thing, so that if it rapidly unassembles itself, the cube catches all the debris and contains the damage.

An elegant and effective solution. Obviously, like many things diving related, it becomes a question of personal risk tolerance.

 

[BRT]

@BRT

Don't confuse pressure rating and safe working ratings. Aside from the plastic projectiles, PVC is especially subject to accidental impact damage... bumping it while moving a ladder or piece of lumber in your shop for instance. There is a reason that OSHA prohibits it for above ground gas use:

OSHA Hazard Information Bulletins, The Use of Polyvinyl Chloride (PVC) Pipe in Above ground Installations

The noteworthy bit is:


It probably won't kill you but it could easily disfigure and blind.

I'm well aware of the hazards. Not too hard to imagine an air bubble in a pvc water system, is it? Do those scare you? I think the risks are still pretty low or I would know personally of some failures with injuries in all these years. I fill my filter housing pressure tester up as full as I can with water and pressurize it with air. The air does not displace any of the water. I'm not afraid of it exploding.

 

[CandiveOz]

So anyway, I decided to try and build one of these babies. I had a chat with the guys in my dive club and one happened to be a technician in the medical/hospital equipment industry. He told me he would look in the recycling bin to see if he could find me some junk. I asked him about the risk of explosion and he didn't seem to be too concerned as long as it was well within the pressure rating of the unit. In his experience, when these filters fail they tend to crack rather than explode. Well, he dumped the stuff off at my place with an old pressure gauge and the attached pictures are the result. The Wilkerson is built out of solid aluminium. The cap itself weighs 2.5 lbs! The unit is rated to 150 psi which is more than I need for my testing. An aluminium cage protects the acrylic tank. I may need to cut a hole in the cage for a better viewing window. There is a hole at the bottom of the tank where we fitted a rubber washer and nut. The only thing I needed to buy was the tire valve. There is a warning not to remove the metal guard to minimise the danger of flying fragments in the event of a tank failure so there is an element of risk to take into consideration if you plan to build one. Then again there is an element of risk when you throw a bunch of scuba tanks in the trunk of your car to take to a dive site. So just be careful.

The unit can hold watch and puck type dive computers. I put on two valves, the black one is the pressure release valve when I want the DC to "surface" and the red one is to lock in the pressure after I pumped up the tank. I sometimes found that my hand pump would leak when I stopped pumping or if I disconnected it from the tire valve, there would be a sudden pressure drop. The red valve eliminates that problem.

 

[kelemvor]

Is the black cover required to hold on the clear part?

 

[CandiveOz]

Hi @kelemvor
No, the cage is not required for the system to work; you can leave it off. With other filters, the cap is screwed onto the acrylic tank. This unit has a locking ring, as shown in the photo, which locks the top cap on to the tank. Obviously the cage adds an additional level of protection.