Bushed tanks at 3,000psi?

[Nemrod]

Has anyone used an aluminum 3000 psi tank on a bushed pipe thread valve using a bushing adapter? The valve is indicated as 2250 service but looks strong enough to run 3,000 psi which is really on 500 psi over the plus pressure these valves were used at? Any thoughts on this? What would be the max pressure you would use a bushed valve at in good condition with clean threads?

James

[duckbill]

Hi Nemrod,
I wouldn't do it. If you do, make sure you get stainless steel high pressure-rated bushings. They are hard to find around here even in pipe-to-pipe. I've never heard of them being available in straight thread/o-ring to pipe thread.
I've been told by a local hydro guy that bushings are actually legal for a dive shop to fill IF the bushing is, as mentioned, stainless and stamped as rated for the working pressure. He said he could get some to replace my 'illegal' bushings in a set of old 1800 psi 1942 Navy twin 38s I have. Maybe I'll have it done some day, but only my local shop would fill it for me. Probably about 99.5% of shops assume that ANY bushing is illegal.
I hope you have your own compressor!

[Bryan]

Why would you want to do this?

[Nemrod]

"Why would you want to do this?"

I cannot answer that because it is secret

I surely would like a source for such bushings as well.

James

[simonbeans]

Nemrod
I was having trouble moving around on the other forum. However, you can get a 45 cu ft low pressure steel from Leisurepro. A bit pricey however. http://www.leisurepro.com/Prod/ItemInde ... MST45.html

[Bryan]

James, I got my 30's from Dive Rite in Florida....They were not cheap but man are the comfortable to wear and haul around. As good as your SAC is I'm sure you could dive forever on them. I agree that steel would be perfect cause you would not need a weight belt in most cases....
I think Ryan Spence was talking about selling a set that he had ? You might E-mail him.

[captain]

James, if you missed my post on Dan's board I have two 316L stainless steel 1/2 pipe to 3/4 straight O ring seal bushings you can have. Let me know if you want them.

[duckbill]

Ya know, the more I think about this idea, the more I like it- IF you can find someone to fill them or you can do it yourself.
The biggest problem with 1/2" pipe fittings is that they become useless after a time due to thread-extusion from annual unscrewing and re-torquing at visual time. With a bushing as described, the 1/2" valve could stay screwed in the bushing and the bushing would be what is screwed in and out of the tank- howbeit a 3/4"-threaded tank.
So, now where can I get some?!

[Nemrod]

Does anyone have any information on how bushings became "illegal"? Just curious what the deal is. A lot of this stuff is cooked up by the evil PadI so they can sell you new neon pink gear. Does anyone know the story?

James

[1969ivan1]

I know of shoppes in Fla that will not even fill regular 1/2 pipe thread valved tanks. They say they are unsafe, but when asked to explain why they just repeat like parrots? A lot of this stuff is so weak and lame, just like VIPs. Why do we need vips on scuba tanks when no other tanks need them by law? I smell a rat!
I SAY DOWN WITH PADI! lets start a grass roots effort to free divers from the bondage!

[luis]

We need VIPs because our tanks are exposed to water too often and on occasion they are filled by incompetent dive shop operators (it only takes once).

Let me tell you a story:
About 30 years ago when I was working at Divers Service Center in Puerto Rico I bought three brand new steel 72 tanks. The very first weekend I used them, we had our tanks refilled at a dive shop in Fajardo, right on the marina. There were several of us unloading tanks from our boat directly to the fill station. The dive shop operator dropped the tanks into the cooling water (salt water) and filled them before I had a chance to blow some air to clear the valve.

That Monday back at DSC a gut feeling let me to open those tanks and VIP them. I am glad I did. Three drops of salt water, three pronounced lines of rust down the inside of the tanks.

A year later the inside of the tanks would have looked very ugly. Maybe ruined.
I remembered how nice they looked when I installed the valves the first time. Two weeks later I was tumbling them. It is amazing what salt water and high partial pressure of O2 can do to steel.

My point is (if it isn’t obvious) VIP’s do work. I have done my own at home and got the stickers from my local friendly dive shop.

I will get off my soap box now.

I do agree with all the other comments (I am not even going to comment about PADI). There is nothing wrong with 1/2” neck valves. They are used in oxygen tanks all over the country. Most portable O2 tanks use 1/2" valves.

I will try to find out about the legalities with bushings. I have been in touch with PSI (Professional Scuba Inspectors) many times this summer searching for information. I had three tanks condemned back in June by a local hydro station. They replaced them after I challenged their test data. That is a long story which I may post in a different thread.

[luis]

I just got of the phone with the manager of PSI and he confirmed that it is perfectly legal and acceptable to use bushings on Scuba cylinders as long as they are rated to the appropriate pressure.

The definition of "rated" is not precise because anyone can actually fabricate a bushing as long as they select an acceptable material and meet the proper thread standards.
I am certain that the stainless steel bushings mentioned above are perfectly acceptable.

I asked him were could I find written documentation if needed to show any local dive shop. The ruling standards would be coming form the Compress Gas Association (CGA). CGA documents are not available for free (like DOT standards) since they are not a government agency. It is kind of a drag because the DOT codes send you to CGA standards in several places.

He suggested that the next best document describing the use of bushings in Scuba tanks was the NOAA diving manual. I have an old (vintage) NOAA diving manual at home. I will be getting a new one soon.



On a related subject, if anyone needs copies of the DOT codes for pressure cylinders and tank re-qualification (hydro testing), the Code of Federal Regulations 49 (CFR49) are available for free on the web. Or if you would like I can email you the appropriate sections as Word files.

[treasureman]

Codes for hydro testing would be nice.

I once bought a used steel tank from a "reputable dive store' for 100 bnux. Got it home torqued off the valve. It appears to be a epoxy lined tank.

Guess what. No shop near me will fill it because it is epoxy linbed. money wasted

A word file is ok

to [email protected]

[oldmossback]

epoxy as in vinyl? Don't have that problem here.....at least not yet. It can be tumbled out if you have the time and dollars.....using steel ball media, like buckshot but made out of steel......works fine. Also, sand blasting works good also.........stay away from the dive stores on this, they don't believe anything but what they are taught, don't seem to have the ability to think outside the box to fix problems.

I had my first pair of 38's nickle plated, went to three platers before I found one who knew how to plate a tank on the outside.....it since has passed 4 hydros for the last 20 years.

Current pair are vinyl both in and out.....the one shop in town that's been around for as long as I've been diving has no problem with a liner.....just tumbles it if there is rust showing.....no problem..........

[luis]

As oldmossback says: “.....just tumbles it if there is rust showing..”

My impression is that internal linings is no reason to put a tank out of service.

The linings turned out not to be very effective in controlling corrosion and they make it more difficult to inspect for rust, but they are still perfectly good tanks.

There is a section on “Internal Linings” from the PSI book: Inspecting Cylinders by William L. High, which describes how to deal with the linings.

I own two lined tanks that were hydro and VIP this summer. I will probably have one of the tanks tumbled next year just to remove some rust. The tumbling should remove the loose paint covering any rust relatively easily.