Tank enclosure…

I don’t think it would hurt to have it. My understanding of carbon fiber tanks is that they are far superior to steel or aluminum in the event of a failure in that they tend not to rupture in as explosive a fashion or to throw shrapnel. From what I’ve heard it typically takes 20k+ psi to cause a failure and they are seriously overbuilt, but that’s just something I read online and am repeating from memory so don’t take it as gospel.

Just know that ductile iron pipe is normally made for underground water systems usually conveying no more than ± 250PSI water pressure.
Although likely tested to well above that PSI, it's likely that the actual burst pressure is in the high 1,000 range, like maybe 1,700 PSI for an 8" diameter pipe.
While that is substantial, it isn't really enough to 'protect' you from a catastrophic event.
However, with the top open, most of the pressure will escape upward, meaning that much like a high-pressure nitrogen or similar cylinder having the valve broken off, it will spin out of control until the pressure is such that it no longer has the energy needed to do any harm.

My 2¢

shootinsquid said:

Found a piece of 9” diameter ductile iron scrap about 2’ tall @ 40 lbs, so decided to make an enclosure I can place my HPA bottles in while filling. The tank shown is a 9L, 7.5” diameter.

Good idea or supremely stupid due to bomb effect? If it’s the latter I’m out less than $10, so no big deal.

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Not necessary but probably won't hurt anything.

Like Revoman had mentioned any real risk is probably a broken valve. A ruptured tank is unlikely...verrry unlikely and if it did, all of that energy will have to be directed somewhere. Hopefully no one will be around to catch it if she blows.

That said, all of that stability will probably keep anytank upright. So that's a good thing.

I'm in the not necessary group, it just adds shrapnel.

Funny, but true. I went to work for one of the largest corporations in the world a bit over 40 years ago and spent 34 years there. We worked on "material development" and one thing we did often was fill CF air cyinders. We had an old setup that looked like an erector set, but it worked. I KID YOU NOT, the instructions said, and they followed this edict, to place the cylinder into a 10" diameter (IIR size correctly) piece of PVC pipe during filling. I would LOVE to know who thought that up and what they thought it would accomplish. That is a true story and when I supervised that area, we purchased a state-of-the-art filling station that had steel "drawer" type enclosures to hold tanks during filling. Whew! that's something only an engineer could come up with!

What was said about CF burst behavior is exactly true, they tend to leak with a rather ear splitting hiss, but no explosion. Of course it depends on the incident, but it's not something that is expected to happen. The build strength is far over their operating pressure.

Somebody posted pictures of a ruptured carbon fiber tank here but it's been awhile ago. Trusting my memory is a bit iffy but I am confident the tank had a big chunk of carbon fiber removed and still didn't fail until well over 10K pressure (less sure about the pressure but it was not near 5000). The carbon fiber kept pieces from flying out, still.

I use an expired Scott Air pack and I take no special precautions. I just do not see them as necessary. But if you do, that's totally OK. I keep my air pack in a wooden tray to protect it, however. I don't want to drop it, especially on the valve. I fill it with the tank in the tray and fill guns with it in the tray. Doesn't add much weight and also holds fill probes, dead head, some silicone oil, and targets.

When I used to fill my tanks at Sea Diver's in Ozark, Al. before Mr. George passed, he would fill them submerged in a large tank of water.

Avator said:

When I used to fill my tanks at Sea Diver's in Ozark, Al. before Mr. George passed, he would fill them submerged in a large tank of water.

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Filling tanks submerged is done more to cool the tank than it is for safety. Divers like big fills and if you just air them up dry they will heat up during the fill process and then lose pressure as they cool down.

Sawney Bean said:

Filling tanks submerged is done more to cool the tank than it is for safety. Divers like big fills and if you just air them up dry they will heat up during the fill process and then lose pressure as they cool down.

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At the time my tanks were a 100cf aluminum scuba tank with 3300 psi max fill and an 80cf steel scuba tank with the same max fill. Mr. George took care of the visual and hydro testing of both when needed. He always filled them in the water tank, let them cool and topped them off. It was a 2 hour round trip and I waited while he filled them. At that time I only had 2k fill guns... a Disco and an FD-PCP.

Avator said:

At the time my tanks were a 100cf aluminum scuba tank with 3300 psi max fill and an 80cf steel scuba tank with the same max fill. Mr. George took care of the visual and hydro testing of both when needed. He always filled them in the water tank, let them cool and topped them off. It was a 2 hour round trip and I waited while he filled them. At that time I only had 2k fill guns... a Disco and an FD-PCP.

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That'll give a good fill. A lot of divers are just in a hurry to get their tanks filled. Some people don't like having the tanks filled in water because they feel that water might get somehow get into the cylinder, but then they proceed to go underwater with them and somehow that's OK, but filling with most of the tank submerged isn't.

Sawney Bean said:

That'll give a good fill. A lot of divers are just in a hurry to get their tanks filled. Some people don't like having the tanks filled in water because they feel that water might get somehow get into the cylinder, but then they proceed to go underwater with them and somehow that's OK, but filling with most of the tank submerged isn't.

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Hmmm... wonder how they feel about having them hydro tested?