Tanks...which ones can't be re-hydro'ed?

[Hemlon]

It seems like I remember reading that certain air cylinders are not able to have new vis/hydro tests due to some issue with a metal alloy.

If I am buying used tanks, what do I need to look for to avoid getting stuck with unusable tanks?

 

[Gombessa]

Section I: Inspection and Testing of Luxfer Scuba Cylinders
Manufactured from 6351 Aluminum Alloy

Luxfer scuba cylinders were manufactured from 6351 aluminum alloy during the following periods:

• United States : 1972 through mid-1988
• England : 1967 through 1995
• Australia : 1975 through 1990

Luxfer requires that every Luxfer 6351-alloy all-aluminum scuba cylinder be visually inspected at least every 2.5 years by a properly trained inspector. As part of this inspection, Luxfer further requires that the cylinder neck be tested with an eddy-current device such as Visual Plus™, Visual Plus 2™, Visual Plus 3™,Visual Eddy™ or equivalent non-destructive testing equipment. When properly used, eddy-current devices contribute significantly to early detection of difficult-to-observe sustained-load cracks in the necks of 6351-alloy cylinders. If the cylinder passes the inspection, the inspector will document that fact. If the cylinder fails the inspection, it must be removed from service immediately. Do not use Luxfer 6351-alloy scuba cylinders that have not been both visually inspected and eddy-current tested and then properly documented.
This Luxfer-required visual and eddy-current inspection is in addition to periodic requalifications (including retesting and inspections) required or recommended by various regulatory agencies around the world. The intervals between retests and inspections vary from country to country.
In addition to the required inspection and testing described above and in keeping with U.S. scuba industry standards, Luxfer recommends that all Luxfer 6351-alloy scuba cylinders be visually inspected at least once each year by a properly trained inspector.
For cylinders in heavy use (for example, those filled five or more times a week), Luxfer recommends visual inspection every four months. For more information, refer to Luxfer’s Scuba Cylinder Inspection Guide, which is available by calling Luxfer at 800-764-0366 or by visiting the Luxfer web site at www.luxfercylinders.com.

 

[halocline]

Gombessa's post is really helpful and thorough. As a simple rule of thumb, you should probably avoid purchasing any aluminum tank made prior to 1988. It's not that all pre 1988 AL tanks are problematic (6351 alloy), but you'll save yourself some arguments with many dive shops that you will find unwilling to fill any pre-88 AL tanks.

 

[Stu S.]

There has been plenty of discussion on this topic. What Gombessa has posted is correct. I must report that some dive shops will not fill the 6351 Aluminum tanks, even though they pass all appropriate tests.

To summarize hundreds of posts: In the spirit of extra safety, or perhaps misunderstanding, a merchant may refuse to fill one of these. This seems to be regional in nature. If you see a deal on one of these, you may wish to call you local compressor operator before buying.

Provided you avoid the above issue.... buying a tank is the biggest bargain in SCUBA! No other dive item holds its value so well. You can't get squat for a used wetsuit, but a tank can always be sold. Used BC = not much resale; but a tank can often be sold for 90% of what you buy it for.

Good luck with it.

 

[Gombessa]

Just to disclose, my response above is cut and paste directly from Luxfer's site.

I've also heard that (but not personally experienced) some shops take care of the problem by just having a strict policy against filling ANY aluminum tank manufactured before 1990, 6351 or otherwise.

 

[diver 85]

Just to disclose, my response above is cut and paste directly from Luxfer's site.

I've also heard that (but not personally experienced) some shops take care of the problem by just having a strict policy against filling ANY aluminum tank manufactured before 1990, 6351 or otherwise.

I think most of Fl is that away AND the Fling won't fill them either(but they supply their own---@ least when I've been out on it the last 2 summers)

 

[Scared Silly]

Read this:

http://www.phmsa.dot.gov/staticfiles/PHMSA/DownloadableFiles/Files/3al_advisory.pdf

and this:

Hazardous Materials: Aluminum Cylinders Manufactured of Aluminum Alloy 6351-T6 Used in SCUBA, SCBA, and Oxygen Services--Revised Requalification and Use Criteria | Federal Register Environmental Documents | USEPA

 

[Hemlon]

There has been plenty of discussion on this topic. What Gombessa has posted is correct. I must report that some dive shops will not fill the 6351 Aluminum tanks, even though they pass all appropriate tests.

To summarize hundreds of posts: In the spirit of extra safety, or perhaps misunderstanding, a merchant may refuse to fill one of these. This seems to be regional in nature. If you see a deal on one of these, you may wish to call you local compressor operator before buying.

Provided you avoid the above issue.... buying a tank is the biggest bargain in SCUBA! No other dive item holds its value so well. You can't get squat for a used wetsuit, but a tank can always be sold. Used BC = not much resale; but a tank can often be sold for 90% of what you buy it for.

Good luck with it.

Just to avoid any confusion, I have my own tanks. I'm just looking to pick up a couple of extras.

 

[matt t.]

The only tanks that CAN'T be re-hydro'd are tanks that have already failed. There is no law against using the tanks mentioned above. Is it wise? That's up to you. If that was all there was to use and I was and I wanted to do the dive, I'd use them. YMMV.

 

[akdeepdiver]

The only tanks that CAN'T be re-hydro'd are tanks that have already failed. There is no law against using the tanks mentioned above. Is it wise? That's up to you. If that was all there was to use and I was and I wanted to do the dive, I'd use them. YMMV.

The above statement is somewhat false and misleading. It is correct in saying tanks made with 6351-T6 alloy can be put back into service as long as they have passed Hydrostatic retest, visual inspection, and eddy current inspection.

But to clarify which cylinders can not be returned to service. Tanks that can not be returned to service are those which have failed Hydro retest and are condemed.

AND

Tanks that are manufatured under a Special Permit (SP) or Exemeption (E), both aluminum and steel, which has expired and has not been renued by the DOT.

AND

Composite cylinders that have passed their wear out date of 15 years.

AND

Many other examples that can be found in 49 CFR.