Scba tank warning

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BenjaminM

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Jun 23, 2022
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Northern Alaska, USA
Well, I bought a couple “bargain” scba tanks off eBay. At first they seemed alright, then I had a valve fail. No big deal I thought, I’ll just take the opportunity to buy one of “air tanks for sale’s” nice valves in 7/8” to replace the Scott firefighter valve that failed… I’ll rebuild that valve to have as a spare in a pinch.

A word of caution, if you’re going to buy used tanks. Check them for moisture before you even think about filling them. This thing was loaded with water, and because of the scba valve design (has a small brass shaft sticking down into the tank) my attempts to turn the tank upside down to purge moisture which the design did not allow.

I cleaned the tank with a provided cleaner the seller sent with it, used piping hot tap water, rinsed twice, then boiled a kettle of water for the final rinse. That heated the tank enough to dry itself and with a charge of dry air purged the tank. It worked well.

Fortunately there were no corrosion issues, but with that much moisture, it would have headed that way if I hadn’t caught it.

I should have done this cleaning and inspection before my initial fill. Lesson learned. I am definitely a beginner here, making beginner mistakes.

Now I’m just waiting on my yong heng parts to arrive so I can fill the thing…hopefully it’s smooth sailing from here. All in all I can’t say buying old scba tanks is saving as much money as I thought it would.
 
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For me personally, for my safety and the safety of my family, I prefer to stay away from used scba tanks of unknown origin. There is just too much potential hazard when dealing with that much pressure. I had to replace my first scba tank last October. Its 15 year lifespan had come to an end. It was expensive; but what I purchased was peace of mind knowing that in my home I have a safe tank that could be hydro-tested every five years. I fill mine at our local airgun store and they require tanks be “in hydro”.
Kenny
 
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Hydro testing is destructive testing on carbon fiber scba tanks.

Ultrasonic testing is the ONLY acceptable method of testing a CF tank. The USN was able to extend all extended service certified CF tanks to 30 years of service (no material changes were made to the tank itself) when ultrasonic testing was used.

It completely floors me that we have not yet learned that carbon fiber does not share the same qualities as metal tank materials and that damage is done to static fibers every time a hydro test is performed, shortening the tanks life.
 
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You're right, CF doesn't share the same characteristics of metal. Metal work fatigues where CF doesn't. When a tank liner is wrapped there's uneven tension as the tow unwinds from it's spool. The tighter ones will be loaded closer to failure than the rest. Remember, a tow can have 3k to 12k strands and that tow will only be about the width of a kite string or just a little larger. I've tested thousands of CF uni directional tensiles and they all popped and ping way before failure and they're only about.040 thick and.500 wide. They also would take between 5k and 8k lbs of load before breaking.

Oh, I forgot to say I cut that straw piece off of my scba tank valves so I can blow out any collected water.
 
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DesertSilver said:
You're right, CF doesn't share the same characteristics of metal. Metal work fatigues where CF doesn't. When a tank liner is wrapped there's uneven tension as the tow unwinds from it's spool. The tighter ones will be loaded closer to failure than the rest. Remember, a tow can have 3k to 12k strands and that tow will only be about the width of a kite string or just a little larger. I've tested thousands of CF uni directional tensiles and they all popped and ping way before failure and they're only about.040 thick and.500 wide. They also would take between 5k and 8k lbs of load before breaking.

Oh, I forgot to say I cut that straw piece off of my scba tank valves so I can blow out any collected water.
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Yeah, I’ll be doing that myself in the future… Lesson learned.
 
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Chief Ten-Beers said:
Since I have never owned one of these tanks, can you just remove the Valve and rinse and dry it out as well as inspect?
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Yes....

But resealing and opening can be difficult and in my opinion, that's when damage happens.

I remember a SCBA being held in a vice and you could hear the 'crunch' of the fibers. Destroyed the tank.
 
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Kgphotos said:
For me personally, for my safety and the safety of my family, I prefer to stay away from used scba tanks of unknown origin. There is just too much potential hazard when dealing with that much pressure. I had to replace my first scba tank last October. Its 15 year lifespan had come to an end. It was expensive; but what I purchased was peace of mind knowing that in my home I have a safe tank that could be hydro-tested every five years. I fill mine at our local airgun store and they require tanks be “in hydro”.
Kenny
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I did buy a new tank (97cf) as well, but wanted the 30 min size to try a more portable option. I might use it 2 years or may keep it going for 10. That remains to be seen. It was a cheap enough way to feel out the idea-at least until you start replacing valves lol…that bit me on the expense side.

I have no commercial fill businesses closer than a 200 mile plane ride away, and then it’d be hazmat with only a couple available fights per year for “hazmat” stuff, so I fill my own tanks-staying “in hydro” isn’t practical for my location, or required that way.

I know a guy who spent over 4 months waiting two bottles of propane for his stove.

After reading up on the navy studies it seems that hydro testing itself is the one of the larger causes of tank damage.
 
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Firewalker said:
Yes....

But resealing and opening can be difficult and in my opinion, that's when damage happens.

I remember a SCBA being held in a vice and you could hear the 'crunc' of the fibers. Destroyed the tank.
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I wrapped this thing up in a yoga mat for grip and put a big wrench on the flats on the valve. It was still pretty difficult to take off the valve.
 
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airgunmike56 said:
I wouldn't have a metal tank in my house, Carbon fiber wrap for me 100%, Kinda of apples to oranges but I had a diet coke explode in the storage closet, Just metal fatigue,
Mike
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I know of oxygen and nitrogen tanks lasting many many years, and I’ve got some co2 tanks for carbonating home brew, but 4500 psi tanks have an enormous amount of energy stored in them… they all make me appropriately nervous lol.
 
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Firewalker said:
Yes....

But resealing and opening can be difficult and in my opinion, that's when damage happens.

I remember a SCBA being held in a vice and you could hear the 'crunc' of the fibers. Destroyed the tank.
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I just sat on mine. I've got a 12inch crescent wrench that I used on the flats on the valve then gripping the tank with my legs loosened it up. My other scba tank is on way to tight so I haven't been able to remove it. It's so dry most of the time where I live I don't really worry about water getting into the tank.
 
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BenjaminM said:
I know of oxygen and nitrogen tanks lasting many many years, and I’ve got some co2 tanks for carbonating home brew, but 4500 psi tanks have an enormous amount of energy stored in them… they all make me appropriately nervous lol.
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I spun out an old 100# Nitrogen tank from the rack last week that the original stamp was 1923.

101 years old and still in service with a 2023 stamp on it after hydro.
 
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BenjaminM said:
I have no commercial fill businesses closer than a 200 mile plane ride away
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Yes, I am very fortunate to have a local air gun retailer only about 15 minutes away from my home. I can drop off my tank, go grab some In N Out and then pick up the tank topped off and ready to go. Usually costs about $8. I would have to purchase a compressor if I didn’t have this store so close.
Kenny
 
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airgunmike56 said:
Alaska ? are you in the middle of nowhere?
I am envies' in the summer, Maybe not so much in the winter,
Its still on my bucket list, Maybe not on motorcycle anymore,
Mike
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Yeah, in a “bush village“ of about 20 people. It’s pretty remote lol. Winters are rough at times.

I think off and on about buying a bike down in the lower 48 and making the ride up, that’d be a fun tim.
 
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BenjaminM said:
I wrapped this thing up in a yoga mat for grip and put a big wrench on the flats on the valve. It was still pretty difficult to take off the valve.
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Typically, a sharp blow with a mallet and wrench is all it takes, it’s usually Just the stiction of the large o-ring that needs to be broken loose.
 
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Scotty1 said:
Typically, a sharp blow with a mallet and wrench is all it takes, it’s usually Just the stiction of the large o-ring that needs to be broken loose.
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In my case I had an 18” wrench on there and still had to lets say ”shock” it loose…the round shape is challenging to hold securely while administering force.
 
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