Luxfer 14cuft 2015 psi Cylinder - hard to find - new hydro $125 shipped

[Scared Silly]

Luxfer 14cuft 2015 Cylinder - hard to find - new hydro $125 shipped

I recently found a couple of these cylinders which are no longer made. They are hard to find.

Cylinder markings: CTC/DOT - 3AL2015 KK7284 LUXFER 5^86 Hydro 3/25 VE

While this cylinder is made from Al6351 they were not subject to Sustained Load Cracking. They have never been part of the DOT advisories. That said as required, it did have a visual inspection done as part of the hydro.

The valve is Sherwood valve. I did do a visual inspection there are surface blemishes but no pitting or other issues. I would have no problem putting my inspection sticker on it.

While the cylinder has been used after 39 years it still the original bar tag on it. If you want a pony bag for it I will toss that in.

 

[Scared Silly]

Bump. Reusing old advert.

 

[Tracy]

Cylinder markings: CTC/DOT - 3AL2015 KK7284 LUXFER 5^86 Hydro 3/25 VE

While this cylinder is made from Al6351 they were not subject to Sustained Load Cracking. They have never been part of the DOT advisories. That said I did have a visual inspection done as part of the hydro.

Where did you read this?
DOT requires eddy testing on all 6351 alloy tanks to the best of my knowledge. I have never found an exemption written anywhere.
I certainly wouldn't expect them to exempt an AL14. I have seen several of them with neck cracks over the years. Hard to know if it was because of the alloy or because they always got filled to 3000 and became work hardened.

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[Scared Silly]

Where did you read this?
DOT requires eddy testing on all 6351 alloy tanks to the best of my knowledge. I have never found an exemption written anywhere.
I certainly wouldn't expect them to exempt an AL14. I have seen several of them with neck cracks over the years. Hard to know if it was because of the alloy or because they always got filled to 3000 and became work hardened.

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A ScubaBoard Staff Message...

This thread has been temporarily moved from Classifieds to a discussion forum

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Read carefully what I wrote as you are conflating the advisory and DOT requalification rules.

I wrote: While this cylinder is made from Al6351 they were not subject to Sustained Load Cracking. They have never been part of the DOT advisories. Here is the advisory:

Notice No. 94-7; Safety Advisory; High Pressure Aluminum Seamless and Aluminum Composite Hoop-Wrapped Cylinders

Here are the cylinders involved in the advisory:

Do.............. 30 and 63 cu. ft...................................... S30, S63 5-88

Do.............. 40 cu. ft............................................. S40 6-88
Do.............. 50 and 92 cu. ft...................................... S50, S92 4-88
Do.............. 72 and 100 cu. ft..................................... S72, S100 8-87
Do.............. 80 cu. ft............................................. S80 1-88
Do.............. 80.8 cu. ft........................................... S80.8 5-87

Note this cylinder is a 14 cu.ft. cylinder with a working pressure of 2015 psi. and is not on the list. Opposed to all of the scuba cylinders in the list which have a 3000 psi working pressure.

That said, I could have been clearer in writing: That said I did have a visual inspection done as part of the hydro. I changed that.

Also if one looks at the history of the SLC issue, CO2 cylinders were initially on the advisory but were dropped from being required to have a VE. That is because CO2 cylinders have a lower working pressure 1800 psi and are filled less frequently. PHMSA stated: The ruptures are directly related to the increased frequencies with which these cylinders are filled and their higher operating pressures.

Similar applies as to why 14 cu.ft. cylinders with a working pressure of 2015 psi were never on the advisory, lower working pressure and filled less frequently.

As such, my advert is accurate.

Finally if your aluminum cylinders had working pressure of 2015 psi and were filled to 3000 psi. Then that is on you for overfilling.

 

[Tanks A Lot]

I'm not entirely sure that this is a fair representation of the DOT 94-7 advisory.

The advisory indicates that a fairly low-pressure cylinder ruptured while being filled to its service pressure of 152 bar (2216 psi).

The way I, and pretty much any inspector I know, interpret the list you quoted is as a helpful guideline. It was meant to determine when the switch from 6351-T6 to 6061-T6 aluminum was made, not to provide an exact list of cylinders requiring special attention. At the very bottom, under industrial cylinders, it specifically calls out low-pressure cylinders:

Do.............. Service Pressures 2016 and 3000 psig.................. 8‐89

Further below, it reads:

[...]
Until determined otherwise, any DOT‐3AL or DOT‐E 7235 cylinder should be assumed to be made of alloy 6351‐T6, if it was:
1. Manufactured by Luxfer USA before the applicable date listed in the chart above;
[...]

It might be that you're placing too much emphasis on the specific cylinder sizes listed in the advisory. I believe the paragraph beneath the list clarifies that the advisory was intended to apply to all 6351-T6 cylinders, not just certain sizes. The paragraph continues with:

For aid in determining whether a cylinder is constructed with alloy 6351‐T6, contact the cylinder manufacturer or distributor. [...] Any person who owns, uses, fills, or retests an affected cylinder should take the following precautions:

1. Do not fill the cylinder to greater than the marked service pressure, except during a hydrostatic test.
2. Do not fill a cylinder that is beyond its required retest date.
3. Do not use a SCUBA or SCBA cylinder that is beyond its required retest date.
4. Whenever you remove the cylinder valve, visually inspect the interior of the cylinder neck and shoulder area for cracks. Any evidence of a crack or crack-like defect may require further evaluation. [...]

For these reasons, I think Tracy is on the right track. This cylinder is most certainly part of the advisory and subject to SLC. Like Tracy, I have seen a few low-pressure cylinders with cracks in them.

 

[Tracy]

I'm not entirely sure that this is a fair representation of the DOT 94-7 advisory.

The advisory he is citing was sent in 1994. It was one of the first advisories about SLC when their was very limited information on them.

 

[-JD-]

[ETA: Clarification "Maybe 6351"]
Anecdotal, but is relevant to the [MAYBE 6351] Luxfer 14s: Cylinder Crack

An Aluminum Alloy 6531 Cylinder Crack
by
Larry "Harris" Taylor, Ph.D.

This material is copyrighted and the author retains all rights. This article is made available as a service to the diving community by the author and may be distributed for any non-commercial or Not-For-Profit use.
All rights reserved.
i​

There have been catastrophic failures in aluminum scuba cylinders manufactured with aluminum alloy 6531. These cylinders were manufactured in the United States by a variety of manufacturers from 1971 to 1988.

This problem began in 1983 when failures in hoop wrapped cylinders resulted in fatalities. Initial investigation of these failures suggested 4 possible explanations:
a. cracking occurred exclusively at the neck ... the region of highest residual stress associated with manufacturing
b. some cylinders had folds in the neck region
c. the aluminum had high levels (> 100 ppm) of lead
d. recycled scrap had been used in their manufacture
In general, the first item above is relevant to scuba cylinders.
The cracks in 6531 alloy cylinders primarily occur in the neck region (figure below) where the crown (threaded portion) meets the body of the cylinder. This volume of the cylinder has the highest residual metallurgical stress from the manufacturing process. This suggests that the cracks are a result of residual stress associated with manufacturing and not exclusively a result of excessive internal gas pressure or poor design. Briefly, the cracks extend from notches created when the cylinder neck is made. Over time, the point of notch formation extends and forms cracks. Crack formation is driven by the combination of applied pressure from gas contents acting on regions of residual stress from the manufacturing process. This process, termed Sustained Load Cracking (SLC) takes many years to create a crack large enough to effect cylinder integrity. Thus far, the cracks have been limited exclusively to the 6531 alloy.​

​

As a result of crack appearances in numerous aluminum cylinders and some catastrophic failures, scuba manufacturers switched alloys used to manufacture scuba cylinders in the late 1980's from aluminum alloy 6531 to aluminum alloy 6061. Luxfer claims that the 6061 alloy is not subject to SLC, but some metallurgists dispute this claim.
In 1999, both the US Department of Transportation (DOT) and the National Institute for Industrial Safety and Health (NIOSH) expressed concerns over aluminum cylinders used in scuba diving. While many cylinders will show cracking in the thread region (easily seen by a skilled visual inspector using appropriate lighting), some cylinders apparently develop internal cracking in the neck/crown region of the cylinder that cannot be seen by visual inspection. So, it cannot be assumed that all cylinders will show cracks in the thread region or leak prior to catastrophic failure.
Since these cracks take many years to develop, the best strategy to prevent explosive cylinder failure is a a combination of hydrostatic testing, visual inspection (with particular attention to the threads), and so called eddy-current testing. Eddy current testing uses electromagnetic induction to create an electrical current within the metal being tested. Anomalies in the metal structure (like internal cracks from SLC) will alter the circular path (an eddy current) of the induced current. These alterations can be detected by a skilled tester. It is particularly important that the eddy current technician be properly trained. (Manufacturers report a large number of eddy-current condemned cylinders had no flaws).​

My Experience​

Below are images of a Luxfer aluminum 6531 alloy 14 ft3 cylinder ("pony bottle") purchased in October of 1982. After years of sitting unused on a shelf, an attempt was made in 2009 to return the cylinder to service. Although the cylinder failed my visual inspection, out of curiosity, I submitted it to a new (for me) hydrostatic tester. The cylinder failed hydrostatic testing. Examination of the neck region revealed Sustained Load Cracking. The neck region (magnified 20 x using a hand held digital Microscope by Celestron) is shown below:​

​

This crack extended through the neck region to the outside of the cylinder. The outside of the cylinder is shown below:​

​

​

​

20 x 400x​

​

Finally, scuba gear is never discarded ... scuba stuff removed from service simply becomes a training aid.​

Further Reading
High, Bill, Cracking and Ruptures of SCBA and SCUBA Aluminum Cylinders Made from 6351 Alloy (available from psi)
Price, JWH & Ibrahim, RN. Cracking in Aluminum Gas Cylinders: A Review of Causes & Protection Measures, Practical Failure Analysis, 3(6), 2003, 47-55.

Acknowledgements
Hydrostatic Testing & Welding, Inc. Lambertville, Michigan
Top

About the Author: ​

Larry "Harris" Taylor, Ph.D. is a biochemist and Diving Safety Coordinator at the University of Michigan. He has authored more than 200 scuba related articles. His personal dive library (See Alert Diver, Mar/Apr. 1997, p. 54) is considered by one of the best sources of information in North America.

Copyright 2016 - 2025 by Larry "Harris" Taylor
All rights reserved.
Use of these articles for personal or organizational profit is specifically denied.
These articles may be used for not-for-profit diving education​

At one point, I had determined that my 10A87 marked one was probably 6351, but I can't find the documentation currently. It is living (out of hydro) at my service bench as a low-pressure test reservoir (<1000 psi) where it is gently trans-filled occasionally. Fingers crossed.

 

[Scared Silly]

I just went back and looked at Luxfer's notices. We are all wrong. Either that Luxfer is wrong

Between 1987 and 1988, Luxfer Gas Cylinders discontinued use of 6351 aluminum alloy and began using a proprietary version of 6061 aluminum alloy for all its aluminum cylinder models manufactured in the United States. Listed below are the dates by model number when the transitions to the new alloy occurred. Any current Luxfer models that do not appear on this list were never made from 6351 alloy in the first place and have always been made from Luxfer’s proprietary 6061 alloy.

SCUBA​

S30, S63 -May 1988
S40 – June 1988
S50, S92 – April 1988
S72, S100 – August 1987
S80 – January 1988
S808 – May1987

As I read the above S14 were never made from Al6351.

 

[-JD-]

I just went back and looked at Luxfer's notices. We are all wrong. Either that Luxfer is wrong



As I read the above S14 were never made from Al6351.

Any current Luxfer models that do not appear on this list were never made from 6351 alloy in the first place and have always been made from Luxfer’s proprietary 6061 alloy

The "current" qualifier could make that meaningless. When was the S14 removed from the product line? When did that notice come out?

A technical parsing of the verbiage and lack of supporting information, admittedly.

ETA: If the S14 was always was made of 6351 and they just dropped the product rather than transitioning to 6061 that would satisfy the text. [ETA3: Additional information ... I find references to Luxfer S14s with 1992 Born-on dates: Closed - Luxfer s14 (Yes the 2015 psi one) & Luxfer 14 cubic foot pony bottle | #220723153 & 14 CF PONY TANK,ARGON ,SPARE AIR,SCUBA DIVING TANK, | #77344389]

ETA2: According to this the technical bulletin was posted in 2003 and 6351 was completely discontinued by June 1988

Sustained-load cracking (SLC) in ruptured scuba cylinder made from 6351 aluminum alloy - Luxfer Gas Cylinders

SLC is a thoroughly researched and well-documented metallurgical phenomenon that occasionally develops in cylinders made from 6351 alloy, as well as in other types of pressure vessels and structural components under stress for sustained periods of time. SLC has occurred in cylinders manufactured...

www.luxfercylinders.com

Sustained-load cracking (SLC) in ruptured scuba cylinder made from 6351 aluminum alloy

SLC is a thoroughly researched and well-documented metallurgical phenomenon that occasionally develops in cylinders made from 6351 alloy, as well as in other types of pressure vessels and structural components under stress for sustained periods of time. SLC has occurred in cylinders manufactured by various companies, including Luxfer. Cylinders that have been mechanically damaged, over-filled or otherwise abused are more susceptible to SLC, which is not a manufacturing defect, but a phenomenon inherent in the metal itself.

Research has consistently shown that sustained-load cracks grow very slowly, typically taking eight or more years to grow large enough to cause a cylinder leak or, in extremely rare cases, a rupture. Because SLC growth is so slow, properly trained inspectors have adequate opportunity to detect cracks and remove cylinders from service during normal annual inspections or as part of the DOT-required requalification process every five years. Both Luxfer and DOT have long maintained that proper, diligent inspection by correctly trained personnel is the best way to avoid cylinder-related accidents.

It is important to note that SLC has occurred only in a small number of older cylinders made from 6351 aluminum alloy. Cylinders made from 6061 aluminum alloy, the metal currently used by all U.S. manufacturers, have not exhibited SLC.

Luxfer discontinued use of 6351 alloy in June 1988 and since that time has only manufactured scuba cylinders from Luxfer’s proprietary L6X® formula for 6061 aluminum alloy. Out of more than 40 million cylinders, no Luxfer cylinder made from L6X® (6061) alloy has ever exhibited a sustained-load crack.

For more detailed information about SLC, visit the Luxfer website at www.luxfercylinders.com, click “Support” on the top menu bar, click “Frequently Asked Questions” on the left-hand menu and then click the “Sustained-load Cracking (SLC)” heading. For specific dates when Luxfer switched different cylinder models from 6351 to 6061 alloy, click “Support,” then “Technical Bulletins” and scroll down to Dates when Luxfer changed its aluminum alloy from 6351 to 6061 (posted November 12, 2003).

If you have additional questions, call Luxfer’s toll-free customer service line: 800-764-0366.

1See Department of Transportation: HM-220F, Federal Register, Vol. 71, No. 167, pages 51122-51129.

Posted by Luxfer

If the S14s were discontinued by November 12, 2003 then the "Any current Luxfer models that do not appear on this list were never made from 6351 alloy in the first place and have always been made from Luxfer’s proprietary 6061 alloy. " verbiage may be completely non-determinative.

 

[rsingler]

We're chasing our tails. I'll contact PCI and ask them to follow up with Luxfer. They have  extensive contacts within the industry. A straightforward question to answer. Do you have a picture of the serial number?