4500 psi, carbon fiber SCBA tanks

[Pakprotector]

A short primer on SCBA tanks. They have a 15 year lifespan( with one exception ), and need a hydro test every 5 years. One at 5 years of age and one at 10...the last one expiring concurrently with the 15 year life. Consider them on a cost per year of ownership. A new one's price, divide by 15 years will net you something like $40/year. Used should be less than this... At near the end of life the cost seems to turn up since the kick-in-the-door price has dropped enough and for a 12-13 year old tank, the price can quite exceed a new one's on that $/year of service cost.

They come in 3 sizes, 30 min or 44 cubic foot, 45 min or 66 cubic foot and 60 min or 88 cubic feet. Most operations charge the same amount for a fill regardless of size so on that basis a big one is better. A big one is of course bigger and less convenient to lug around.

The tanks all have a common thread and sealing method, so a variety of valves can be screwed in. To use with an airgun, you should have a gage on the rifle side of the valve so you can tell what pressure you have put into its reservoir, and there will be a bleeder to drain the pressure so the rifle can be disconnected from it.
cheers,
Douglas

[roachcreek]

One thing to consider on carbon fiber scba tanks, is that if you fill them yourself with a Shoebox or other compressor, you are not limited to 15 years.

Actually the life of these tanks is unknown, in Europe they have a 30 year lifetime.

I use expired tanks that I got off of Ebay and I have current tanks also, does not bother me in the least.

There has never, ever been a scba tank that failed in air gunning.

Your chances of getting hurt by a falling meteorite are far better than getting hurt by an expired tank.

[Baja_Traveler]

And then you have the common metal cylinders. They have an unlimited shelf life - so long as they pass the 5 year hydro and visual inspections. Scuba tanks that have been used on multi day dive boats are more prone to internal corrosion due to being refilled onboard in a marine environment. Every time it's filled out there, the tiniest bit of salt water gets into the tank and it adds up over the years, the deck hands rarely if ever wipe down the fill whip before filling a tank.
Don't buy a used tank from a Divemaster or Instructor - when I was doing it, we would be in the water 5-6 times a week doing classes, and Divemasters like me who also did multi day dive trips had literally thousands of offshore fills on the tank. During the visual inspection if internal pitting is found, and is small enough as measured by a probe, the tank can be tumbled with ceramic media to clean out the corrosion and re hydro'ed.

The most common of the tanks is the ubiquitous "Aluminum 80" - it has a 3000 psi rating.
There are also steel 80 tanks, that have a lower rating, 2500 psi. Some of them may be marked "+P" and these can be filled to a higher pressure (2650 if I remember correctly). The +P rating does have a shelf life of 15 years, then the tank reverts back to the lower rating. My wife had these because the steel offers better buoyancy control when the tank gets empty.
Then you have the HP steel tanks. Mine are HP 130's and they are rated to 3500 psi (though in europe they are rated up to 4000) these tanks are heavy. I swear mine are better than 50 pounds each when full. All the high pressure tanks will have a screw-in DIN connector on them. They cannot use the common Yoke connector found on all the other scuba tanks because of the pressure involved.
There are also smaller "pony bottles" that may be found in the classifieds. Same rules apply to them, though they are usually in better shape because they are used less often (or never at all).

I won't give up my big HP tanks, but I will be in the market for a small carbon fiber pony bottle to carry with me while out hunting squirrels and rabbits. I like the idea of using a shoebox compressor and expired tanks. An expired tank can be picked up for nothing and be perfectly serviceable. The industry is extremely conservative when testing tanks, so a so-called failed tank is usually perfectly good (unless it has a cracked neck or huge internal pits)...

[Pakprotector]

The energy stored in 13 ci at 3000 psi is 51,000 FPE. Y'all are betting life and limb to avoid a trivial expense. Cost per year ownership is about a quarter of a tank of fuel for my Dodge, maybe a tin and a half of pellets...two at the outside. That y'all argue that it is 'perfectly serviceable' is just a bit much. Do please have the decency to advertise you are running expired tanks so that others don't have to unknowingly bet along with you.
cheers,
Douglas

[roachcreek]

Yeah I hear that argument all the time, but the fact is on risk management, you have to take failures against the users numbers, and there have never, read that again, never been, a failure with a air gunner and a expired scba tank.

Look at it this way, if you drive the LA freeway going to work and want to know your risk, you take the number of miles driven on that freeway by al drivers and the amount of fatal accidents and you do the math and get your chances of being in a fatal accident.

With scba expired tanks you can't do that, it has never happened to air gunners the risk is zero.

On this 15 year expense of ownership divided by 15 is a nice quote if your selling new tanks, or trying to rationalize why you bought the thing in the first place and remember even Compressor and tank salesmen have put up expired scba tanks for sale on the Yellow classifieds.

Now the fire department failures accounts for one, it was abused by a fireman who exposed it to chemical corrosion, it blew, and they should have known better. And that brings up doing the due diligence on the air gunners part don't use a tank with a dent in it, current or not, same thing if it has been painted, don't use it, deep scratches also.

Fire departments fill their tanks quickly which gives stress on the tanks by expansion. To fill a scba tank from 2800 to 45oo with a Shoebox compressor takes 2 to 3 hours it is slow and it does not produce heat or tank stress.

Question is, is a fireman with a 14 year 11 month old tank a walking time bomb in a burning building? Of course not, but listening to the "sky is falling" due to a expired air tank blowing up is just as much nonsence.

But if you can show me the carnage caused to air gunners by these tanks I will certainly be willing to listen, but fact is your going to be looking for that first accident long after I have rotted out a coffin liner, cause it has never happened Douglas. I have argued this subeject with the best of them, and the truth is there have been absolutely no accidents with air gunners.

Better chance of getting trampled by the cloned mammoth in the future than hurting yourself right now with a scba tank out of hydro, Why? Early men were trampled by mammoths, again no air gunners have been hurt by failed scba tanks.

That 15 year old date is something the government came up with as a guess that was based on absolutely no evidence what so ever for a product liability on a produt that was new and there was not track record for.

So your going to be hearing me tell you over and over again until your as sick of listening to it as the guys on the Yellow forum are who don't argue the point anymore with me, which is...................

"Show me the carnage."

Now having said all this, I don't use scuba tanks, when they fail, and they do, they are simply a metal bomb without fins and detonator.

[Pakprotector]

"With scba expired tanks you can't do that, it has never happened to air gunners the risk is zero."

You leave out a critical, 'yet'. Therefore you can not go calling it zero. Do what ever you want, but your justification does seem centered around a, 'hasn't happened yet, therefore it can not happen at all' and to put it quite bluntly, that argument is just plain poor.

I drive to work without killing myself in an accident, I have not died therefore the risk is zero.

Good luck RC, you are worth a wee bit more than $20/year just to me...I hope it is more to yourself.
cheers,
Douglas

[roachcreek]

An Alien invasion has not happened yet despite what the History channel tells us, well if you discount our southern border anyway, but the percentage of risk of space craft arriving in the evening sky this evening is exactly the same as air gunners blowing up a expired scba in good condition.

Meaning neither has happened as of yet.

Yes I do consider my safety, so I have to ask, can you show me the carnage from these tanks exploding?

I did warn you.:)

[BCB]

http://i42.tinypic.com/k1yvk0.jpg

I recently got into the airgun shooting hobby…

I thought that I had researched it well—but that proved to be wrong…

I am shooting the Marauder 22 which shoots at 3000 psi…

All well and good. But, I thought I could buy a used scuba tank and get it filled to 4500 psi—wrong…

There are used carbon fiber tanks, but usually they only have 5 or 6 or 7 years left on them and they are more than ½ the price of a new one with 15 years life…

I had to purchase a carbon fiber tank from a supplier in California…

Then, don’t forget all the fittings necessary to hook to the airgun to fill it, plus the fitting to allow a fire extinguisher place of the local fire department (if they will fill it for you)…

You get into big bucks…

Shoebox compressors are one thing, but you must have another compressor to feed it air. The shoebox costs $600 at the minimum…

With the price I have in my setup, I could have purchased 3 Contender barrels and a receiver. Now those things will shoot cast boolits and that is what we are all about…

I would think many times about a pcp airgun—at least the ones that need a 4500 psi air supply…

For those really interested in airguns…

http://www.gatewaytoairguns.org/GTA/index.php?PHPSESSID=d4e9db3bdfb35f271faf5ddcaebf99 c5&action=forum

Good-Luck…BCB

[MT Chambers]

You are best not to mess with the metal ones at 3000psi, you won't be happy, the Fibreglass wrapped 4500psi tanks are almost a necessity for PCP rifles, another important factor is to get a lot of shots per fill out of your gun, or you'll have to strap the tank to your back when you go out in the woods.

[Pakprotector]

I have a few Marauders. The 25 cal is shooting a fine string of pellets at greater than 1.3 FPE/ci of air usage from 2k-1k4 psi. JSB King velocity throughout the string( within 4% spread ) is 920 fps. The stock valve/porting needs to be much larger, and then low pressure operation is possible. Instead of a 1k5 psi pressure drop in a 4k5 psi tank, I now enjoy 2k5 worth of air out of 'em.

With a bit of careful looking, I have acquired all my carbon fiber tanks at less than 2/3 the cost of new on a per year of ownership cost. The number is actually closer to half...:)
cheers,
Douglas