HPA Tank Failure - Should I Be Concerned? What Happens When A SCBA or SCUBA Tank Fails? What Happens When A Valve Fails? (VIDEOS)

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Ezana4CE

Ezana4CE

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Jan 15, 2021
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I've read several AGN posts about what a SCUBA or (mores in most of our cases) SCBA tank will and won't do when it fails. Similarly discussed is valve failure. Today I decided to look and see what I could find as far as video content on the topics. I didn't conduct an extensive search, but I found a few videos of interest.

This is a controlled experiment where what appears to be a SCUBA tank explodes in an explosion-proof compartment (due to what I assume to be filling the tank well beyond the maximum rated fill pressure). It appears if exploded when approaching 320 bar. I believe that SCUBA tanks are rated to safely hold 3000 psi or approximately 207 bar. Most SCBA tanks that concern airgunners are rated to be safely filled to maximum pressure of 4500 psi or approximately 310 bar.


In the following video, the valves on several HPA SCBA tanks were intentionally knocked off in a guillotine-styled device in an open and somewhat controlled setting. They behaved somewhat like cheap fireworks you may have played with as a child.


"MAE Test and Burst of a SCBA Cylinder - Self Contained Breathing Apparatus" This video appears to be a scholarly and scientific approach to explaining SCBA tank failure and is conducted and filmed in a controlled environment. According to the content creator(s), MAE stands for "Modal Acoustic Emission." I don't know what this is, but it gives me something to look into later. The content creator claims that this method is used by the United States Navy in expanding the life of SCBA tanks (refer to the video description within the link).


I will add videos to this post as I find them.
 
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I appreciate you looking up this stuff and putting a nice thread together so it is easily available. But I don't think this information is very useful to airgunners. I don't use a SCUBA tank and probably never will because they are heavy and can only be filled to about 3000 psi. I guess it is a little interesting to see the catastrophic damage that happened when one was filled to over 300 bar but I won't be doing that. It was also a little interesting to see that a SCBA tank with half the carbon fiber cut away didn't fail until over 12,000 psi but I won't be using a carbon fiber tank damaged at all let alone this grossly damaged. I have no way to fill one to 12,000 psi. It does show the tanks have some margin. I did not watch the hydrotest video, my tank is too old to get tested and I wouldn't get it done if I could. I do not see why I need a hydro test since I am confident it will just leak if it ever fails.

To me it is important to remember that a SCUBA tank is to provide breathing air for someone SCUBA diving. If it fails, they could die. Similarly a SCBA tank is to provide breathing air to a fire fighter who could die if it failed. For either of these applications a slow leak could be a huge problem or even deadly. For filling my airguns, a slow leak will be a disappointment but not at all life threatening. A very conservative service life and a frequent testing interval probably make sense when the result of a failure could be a death. I can't help but feel these requirements are overkill for me fill my PCPs.
 
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@JimD I'm not sure what the difference is in the comparative details of the damage following a SCUBA tank that explodes due to over pressurizing versus that of a damaged SCBA tank that is over pressurized. Information presented in this thread is used to paint a picture. There has been much conjecture on the topics in the forums with little evidence that I've seen. Herein lies some sort of evidence and thus
usefulness to air gunners. As long as there are questions or debates on safety regarding SCBA tanks (including buddy bottles and bottle fed airguns), I am of the opinion that evidence-supported information has a place and use in the airgun community.
 
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Still using my aluminum Luxfer SCUBA tank at 3k. One rifle is regulated at 1700 psi, another rifle has hammer spring issues above 2700 psi and finally rat smacker is good to 2k. The tank is hydro tested to 5k, then lucky you get it back for another 5 years. Very useful depending on your rifle(S) and where they fall out of regulation. I saw a video of my DOT 3 AL losing it at 8K.
 
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Ezana4CE,

The SCUBA example may be useful for people using SCUBA tanks since the pressure that caused failure is something compressors sold for PCPs could produce. But it is also below the pressure Dog says his SCUBA tank is tested to. I guess there are different pressure ratings for SCBA tanks? I don't know much about them. A conclusion that you may need to be careful with overfilling them if you have a lower rated one that could fail at 300 bar or whatever pressure your compressor could provide. This is just my conjecture but a uniform metal tank could be more susceptible to the catastrophic failure that was illustrated since there would not be a localized area where the stress got too high, it would be the whole tank. Or a large seam in the tank. But another element of these examples that does not apply to home filling of tanks, at least with the compressor I have, is the rapid fill. My little YH takes 5-10 minutes to go from ~4000 psi to 300 bar. I think slower filling reduces the chances of a catastrophic failure. I think the chances of a small leak type failure that can be detected and the filling stopped is better if the tank is being filled slowly.

But I still do not see how knowing a SCBA tank like I use could fail with extreme damage at a pressure I can't get to does much of anything for me. If anything, it seems like it could cause a user to ignore damage which I don't think is a good idea. The failure is just not at conditions that are even close to those a PCP user would ever see. 12,000 psi is just not something my tank will ever see.

I am concerned with the motivation of the people making these videos. Why are they not testing at conditions that a tank user would experience? Why fill extremely quickly? Because you know it could produce a more interesting catastrophic failure? Any maybe sell some tanks for you? Why not test some really old SCBA tanks? Or one with some damage from water? Maybe they have and I just haven't seen them. I've also seen them used inappropriately where they show the failure but do not explain the extreme conditions that led to it.

I remain convinced that testing at extreme conditions that are nearly if not totally unreachable by us PCP users is of limited value. I also remain appreciative that you spent the time to make the information available.

Jim
 
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When I went to the Mako maintenance school in Ocala Florida years ago they had a fill containment cabinet out in the parking lot. The cabinet would hold two cylinders and were isolated/seperated from each other. Their test, and I don’t know if it was an OSHA or some other agency requirement, required a cylinder to be taken to burst. The neigboring cylinder could not be damaged by the exploding cylinder. The cabinet was bulged out on all sides. They had to use a cutting torch to cut it open to check for damage to the second cylinder.
From the reading I have done on AGN there seems to be an undercurrent of some users to ignore hydro tests because they own their own compressors. To each his own. Even the cylinders on the rifles require hydros.

For carbon fiber tanks it’s really a good idea to protect it from scratches that damage carbon fibers, but it does take a lot of deep ones to condemn a cylinder (if inspected by a trained cylinder inspector). The condemning is way premature of possible rupture, but that’s what keeps us safe. A quick google search will yield the allowable damage to a CF SCBA.
Any SCBA valve that I’ve seen are aluminum. I have never heard of an SCBA valve breaking off but maybe it has occured, same for scuba tanks, but scuba tank valves are brass and may or may not be stronger than aluminum valves.
It’s not a bad idea to protect the tank surface from scratches and maybe the protector go high enough to protect the valve as well.
 
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Again, ANYTHING under pressure can send something flying somewhere. All these worst case scenarios that some people stress over are nothing to stress over especially how & what we airgunners use tanks for. The exploding tank "myth"? Get over it! CAN it happen, yes, possibly. LIKELY any one of us will see it happen? I said before, less likely than the Cubs winning World Series 2 years in a row! Those are odds I feel absolutely safe with.
 
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A data point that would be of interest is a detailed graph of the tanks pressure during one of the "burst" examples. If the measurements are taken over a short enough time interval I think we would see the fill rate decrease close to the time of rupture. Because the tank would leak first. But I've never seen that information in a form it could be seriously reviewed. I am mainly interested in SCBA tanks.
 
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After reading some responses in this thread I’m under the impression that the point of this thread is lost on some members. I have to accept some of the blame for not explicitly stating my intent when I created this thread. As long as threads like what’s discussed in the following link abound

N/A - High Pressure Fear - Rant/Vent : )

Anyone else still get freaked out dealing with the high pressure air in PCPs? Sometimes I wonder if I picked the wrong hobby or this is something that goes away over time. I just finished a barrel polish on my Rattler. Reassembled the whole thing, screwed the valve back in the CF 580cc tank...
www.airgunnation.com www.airgunnation.com

then I believe that my thread here will be valid to some degree. When I read threads like the one linked above, I see a lot of “I know this and because of that, you don’t have to worry about ‘xyz’” responses posted and repeated when the topic resurfaces. Those sorts of answers serve little purpose to some people who know almost nothing about HPA or PCPs. In my opinion you are essentially asking a stranger to trust you in order to allay their fears. Why not show them how something like what they claim they are afraid of can happen and how unlikely it is?

This is an informational thread. Period. I don’t understand what the arguments are with someone attempting to share information. And I didn’t intend to respond to some of the posts here until I saw the recent thread I listed above. It’s not the first or second thread I’ve read like that on AGN. Not will it be the last. This post isn’t about fearmongering and I’m no expert in high pressure air of SCBA tanks. I’m still learning myself. I saw a need and simply attempted to address it. @JimD If you didn’t need the information that doesn’t mean someone else doesn’t.

Before I understood much of anything about HPA I would get nervous in certain scenarios. Now I have more confidence working with it after reading, asking questions, being corrected, and watching videos like the ones in the first post. I’ve had a legitimate scare or two and was fortunate that I wasn’t injured. I can sympathize with people who have similar anxieties. If you have learned to respect high pressure air and know where the dangers truly lie, why downplay the importance of understanding to others that obviously don't get it? I also stated that I conducted a brief search when I found the videos that I posted in post #1. In so many words in post #3 I stated that I wanted to post evidence because threads and debates about this sort of thing will arise as long as new airgunners are attracted to the sport. If you have evidence that can help educate others on the relative safety of our PCPs, HPA compressors, SCBA tanks, fill lines, fittings, etc please feel free to share it here. That way when someone comes with a bomb theory, they can be referred here so they can see under what circumstances a SCBA tank becomes bomb-like. Or the importance or benefit of protecting the SCBA tank valve and having the threads on their SCBA tanks and airgun reservoirs inspected periodically. I’d like to encourage other to take what you can use from this thread. If you have something of value to add, please feel free to post it.
 
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Ezana4CE, sorry if I came across as a know-it-all. I think I thanked you in each post for taking the time to make the information available. Unfortunately some of the information available on-line on this topic seems to have been created to sell new SCBA tanks. I'm talking about the exploding tanks "tested" under unrealistic conditions. That sort of information is not informational in my opinion it is intended to create fears and thus sales. I am not trying to be critical of you, you didn't create it. But the fact that a SCBA tanks with half the carbon fiber missing in a significant sized area can fail catastrophically at 12,000 psi just doesn't do much for the normal PCP user. The pressure the SCUBA tank failed at is reachable with our compressors but no details on the tank seem to have been included. It seems like that pressure would have been within the design if not tested pressure for a normal 3000 psi SCUBA tank. Perhaps it was a 2000 psi tank? Even it it was a 3000 tank it shouldn't have been filled to over 300 bar.

I've tried to attach a report by the Navy that details their good experience with SCBA tanks. Large portions of it talk about an alternate testing program but there is still a lot of information on their experience. They use a lot of SCBA tanks.

My intention is not to criticize you it is to point out the unrealistic nature of some of the "information" you are linking. I hope that is useful. I don't think I've suggested that we do not need to be cautious with high pressure air. I believe we need to be careful to the point of being a little afraid. But we need good solid information about what we need to be afraid of. It's just my opinion but I do not believe that we need to be afraid of even an expired SCBA tank "exploding" when we're filling it with our 300 bar compressors. To my knowledge, nobody has ever had that happen and there are some reasons to believe that the way they are constructed makes that highly unlikely.

Jim

View attachment navy-self-contained-breathing-apparatus-scba-composite-cylinder-life-extension-research-project.pdf
 
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@JimD I wasn't thinking that you came across as a know it all, but some of your comments came across as dismissive when I read them. I'm thinking that if damaged carbon fiber SCBA tanks truly fail consistently at over 10,000 psi then my 4500 psi compressor shouldn't be a large concern in terms of producing pressure resulting in catastrophic failure of my 74 cuft CF SCBA tank. There have been several conversations in the "Tanks, Pumps, and Compressor" forum about the necessity and reliability of the auto-shut off features offered by a couple of vendors versus the necessity to stay and watch the SCBA tank during the entire fill cycle and similarly about reliance upon safety valves. I still think staying with your tank and compressor is necessary for safety, but after watching videos like these, I'm not convinced that someone should have to worry about their home being damaged by a compressor not capable of building the amount of pressure that we're told was produced to catastrophically rupture a damaged SCBA tank as seen in the video. I composed this thread with the content of many other threads in mind that I've read over the past couple of years. I think I was moved to post this after seeing a recent thread and I figured "These threads just aren't going to stop creating a hamster wheel of the same or similar information with little data or sources to support it."

I have looked into some writing on some research produced in attempt to enable the Navy to extend the life of their tanks. Those writings are great to read because there are SCBA tanks and HPA devices placed in various stations on board US Navy vessels. So those folks know their stuff. If we have any DC men or ex-DC men in the AGN community, I'd love to hear from them.
 
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I was reading some internet SCBA info and was reminded of something I saw some years back while scuba diving in Roatan.

The info I was reading was fire department handling of SCBA’s. The standard practice for the department was to store SCBA’s fully pressurized. For the fire service it’s a no brainer why they’re stored full. There’s another reason though why it’s better to store high pressure cylinders full, or pretty close.
And granted it’s also sort of a one in a million kind of reason.

Back to Roatan. At the dock where our dive boat tied up there was a scuba tank hanging on the wall. See photo below.
There was a fire one night on one of the dive boats that the staff had not removed the tanks that were used for diving earlier that day. All of the aluminum scubs tanks were at around 300-500psi. Several of the tanks ended up like the one in the photo. Why?

All scuba tanks have burst disks in them. Standard 3000 psi scuba tank burst disks are rated at 4500-5000psi. Pure aluminum is dead soft. It gets all its strength from tempering. Aluminum scuba tanks and SCBA cylinder liners are 6061-T6. The T6 refers to the temper that the aluminum is treated to, giving it tremendous strength. Years ago Luxfer made tanks from 6351 aluminum that had trace amounts of lead in them to aid manufacturing. A very small percent of those tanks developed cracks in the necks, typically in the threads. Today most dive shops won’t touch a Luxfer 6351 alloy tank and industry wide they are supposed to be removed from service by drilling a hole in the tank or permanently damaging the threads.

So why did the Roatan tanks blow up at only 300-500psi ? In a fire a full scuba tank will heat up and cause the burst disk to rupture and safely vent the gas. In the case of the Roatan tanks, the fire annealed (softened) the aluminum to where all the temper was relieved and the pressure in the tank didn’t reach burst disk pressure, which it probably never would have, and the softened aluminum let loose, violently.

Food for thought as to what pressure you store your SCBA’s at. Not trying to kick the beehive or scare anyone, just some information.

IMG_1546.jpeg


IMG_1544.jpeg
 
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Ezana4CE said:
After reading some responses in this thread I’m under the impression that the point of this thread is lost on some members. I have to accept some of the blame for not explicitly stating my intent when I created this thread. As long as threads like what’s discussed in the following link abound

N/A - High Pressure Fear - Rant/Vent : )

Anyone else still get freaked out dealing with the high pressure air in PCPs? Sometimes I wonder if I picked the wrong hobby or this is something that goes away over time. I just finished a barrel polish on my Rattler. Reassembled the whole thing, screwed the valve back in the CF 580cc tank...
www.airgunnation.com www.airgunnation.com

then I believe that my thread here will be valid to some degree. When I read threads like the one linked above, I see a lot of “I know this and because of that, you don’t have to worry about ‘xyz’” responses posted and repeated when the topic resurfaces. Those sorts of answers serve little purpose to some people who know almost nothing about HPA or PCPs. In my opinion you are essentially asking a stranger to trust you in order to allay their fears. Why not show them how something like what they claim they are afraid of can happen and how unlikely it is?

This is an informational thread. Period. I don’t understand what the arguments are with someone attempting to share information. And I didn’t intend to respond to some of the posts here until I saw the recent thread I listed above. It’s not the first or second thread I’ve read like that on AGN. Not will it be the last. This post isn’t about fearmongering and I’m no expert in high pressure air of SCBA tanks. I’m still learning myself. I saw a need and simply attempted to address it. @JimD If you didn’t need the information that doesn’t mean someone else doesn’t.

Before I understood much of anything about HPA I would get nervous in certain scenarios. Now I have more confidence working with it after reading, asking questions, being corrected, and watching videos like the ones in the first post. I’ve had a legitimate scare or two and was fortunate that I wasn’t injured. I can sympathize with people who have similar anxieties. If you have learned to respect high pressure air and know where the dangers truly lie, why downplay the importance of understanding to others that obviously don't get it? I also stated that I conducted a brief search when I found the videos that I posted in post #1. In so many words in post #3 I stated that I wanted to post evidence because threads and debates about this sort of thing will arise as long as new airgunners are attracted to the sport. If you have evidence that can help educate others on the relative safety of our PCPs, HPA compressors, SCBA tanks, fill lines, fittings, etc please feel free to share it here. That way when someone comes with a bomb theory, they can be referred here so they can see under what circumstances a SCBA tank becomes bomb-like. Or the importance or benefit of protecting the SCBA tank valve and having the threads on their SCBA tanks and airgun reservoirs inspected periodically. I’d like to encourage other to take what you can use from this thread. If you have something of value to add, please feel free to post it.
Click to expand...
Reality is that there will always be people who see danger at every shadow.
They literally look for stuff to worry about. They see danger no matter how remote the possibility that an event may occur.
I appreciate your effort to cast some light on the subject and hope that it reduces the stress for the habitual worry warts.
 
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Chukar60 said:
Reality is that there will always be people who see danger at every shadow.
They literally look for stuff to worry about. They see danger no matter how remote the possibility that an event may occur.
I appreciate your effort to cast some light on the subject and hope that it reduces the stress for the habitual worry warts.
Click to expand...
Knowledge is power.
 
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I've never had a desire to use a SCUBA tank with my PCPs but one thing this thread has done is give me more reasons not to use a SCUBA tank. The thin aluminum liner of a SCBA tank is at least a little bit like a giant rupture disk. It will not take much pressure, it will only stay intact when the carbon fiber is intact. If there is a local failure of the carbon fiber, the same area of the tank will open up and the air will leak through any remaining carbon fiber. Failure of a SCBA tank at 12,000 psi with half the carbon fiber missing is pretty impressive. It is fully possible to see this information as a reason not to fear SCBA tanks. We cannot create that sort of pressure.
 
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JimD said:
We cannot create that sort of pressure.
Click to expand...
Exactly right. Many PCP compressors have burst disks that will pop well before the burst pressure of an SCBA’s, and the SCBA also has a burst disk to protect it as well.

Your best bet is to protect your SCBA’s exterior from damage with a bag some other method.
 
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