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Old 01-17-2018, 08:17 PM   #1
Wilderness dave
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Tank fills

So Iíve heard you canít get tanks older than the h year 2000 filled in Florida or something like that?
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Old 01-18-2018, 05:33 AM   #2
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Re: Tank fills

Here is the summary for scuba cylinders:

All Walter Kidde DOT-3AL cylinders, of which production ceased in
January 1990, are made of alloy 6351-T6. Cliff Impact DOT-3AL cylinders
were made from alloy 6351-T6 before July 1990, at which time Cliff
Impact changed to alloy 6061-T6. Catalina Cylinders did not produce any
DOT-3AL cylinders from alloy 6351-T6; therefore, cylinders manufactured
by Catalina are not subject to this notice.
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 below;
2. Manufactured by Cliff-Impact before July 1990;
3. Manufactured by any other company in the United States,
excluding Catalina, before February 1990; or
4. Manufactured outside the United States.

Now lets focus on cylinders made by Luxfer as they are the most predominate scuba cylinder made with AL6351:

30 and 63 cu. ft............................. S30, S63 .... mfg date 5-88
40 cu. ft....................................... S40 ........... mfg date 6-88
50 and 92 cu. ft............................. S50, S92 .... mfg date 4-88
72 and 100 cu. ft........................... S72, S100 ... mfg date 8-87
80 cu. ft....................................... S80 ........... mfg date 1-88
80.8 cu. ft.................................... S80.8 ......... mfg date 5-87

By quickly scanning one can see that by July of 1988 Luxfer had quit making cylinders using AL 6351 and had fully switched over to AL6061. As importantly, given that the vast majority of aluminum scuba cylinders in use are AL80 for the most part one could "safely" say that any Luxfer AL80 made with a hydro year of 1988 were made using AL6061. Though I have seen a 1-88 hydro date for a Luxfer cylinder.


Where did the 1990 date cut off for not filling a cylinder that many shops use come from???

In a nutshell it an arbitrary date. As noted, Luxfer quit using AL6351 18 months before hand. Yet Walter Kiddie and Cliff Impact made cylinders using AL6351 through Jan 1990 and July 1990 respectively. I suspect the date which is a nice round number came from the observation that Cliff Impact cylinders were few and far between and while Walter Kiddie were common that the chance of Jan 1990 sneaking in was remote.

Commentary regarding the 1990 date. I have heard the reason for the 1990 date is that it easy to remember for those filling cylinders. I do not buy it. Those filling cylinders are suppose to be knowledgeable and trained in hazmat rules and CGA recommendations for their job. Which requires the ability to read. I do not believe that having a quick lookup table such the one above is so difficult that substituting an arbitrary date is reasonable.


So now that you have determined that you have a cylinder made from AL6351 what needs to be done with it?

The practical side. More and more shops are declining to fill cylinders made from AL6351. As such, before spending money on requalifying check to see if you can get it filled. Otherwise, it might just be a big wind chime.
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Old 01-19-2018, 02:16 AM   #3
Wilderness dave
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Re: Tank fills

Thanks for the info, looks like I’m good to go. I must admit my eyes started to glaze over a little though reading that. I have a couple steel and the others are new aluminum’s .
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