Aluminum Nitrox tank?

[Loneranger]

Stay away from any Luxfer tanks 1986 or older.

 

[No Fish]

you should service and clean the valves too...if they are included.

 

[herman]

The easiest way to determine if the tank MAY be 6315 is to simply look at the ORIGINAL hyrdo date. It's in plain text somewhere on the top of the tank. A Luxfer original hydro will look something like 05^90 for May 1990. The mark between the month and year is the seal of the hydro facility. Every facility has it's own unique seal. Luxfers looks like a arrow pointing up. It's usually the only one that is painted over. If it's 89 or later the tanks are not 6315. Like DA said, there is actually nothing wrong with the older tanks if they are properly checked. The biggest problem is many shops will not fill them. I have one of them and my shop will fill it if they have done the vis themselves. $40 is a great deal IF you can get them filled.
As for testing and cleaning, if they have been hydroed within the last 5 years, they do not need to be hydroed, just vis'ed. If your shop uses premix then you do NOT need to have the tank O2 cleaned, just vis'ed and marked for nitrox.

 

[DA Aquamaster]

Stay away from any Luxfer tanks 1986 or older.

That does not quite cover it - see the list below.

Run the serial numbers - your LDS should be able to find the month and year they were made; US made tanks are manufactured under strict DOT guidelines - STAY AWAY from 6351T-6 aluminum alloy tanks PERIOD.

"PERIOD" is a little overblown. You need to avoid 6351-T6 alloy tanks that are not properly inspected, or if your LDS will not fill them.

----

The quickest way to tell if a Luxfer tank is made from 6351-T6 alloy is to check the original hydro test date (the earliest one on the tank and also the one that is painted over) and also to identify exactly what you have for a tank. Luxfer tanks have an S followed by the capacity of the tank (in cubic feet when full) stamped on the shoulder to identify what it is.

The following is a list of dates (month and year) prior to which various Luxfer tanks were made from 6351-T6 Alloy. If the tank has a date equal to or later than those below it is made from 6061-T6 that is not known to have problems with sustained load cracking and is not subject to visual plus inspection requirements.

S30, 5-88
S40, 6-88
S50, 4-88
S63, 5-88
S72, 8-87
S80, 1-88
S80.8, 5-87
S92, 4-88
S100, 8-87

If you can only remember one date, remember that any Luxfer tank made after May 1988 will be the newer 6061-T6 alloy.

In addition, all Walter Kidde tanks were made of 6351-T6 alloy until they were acquired by Luxfer in about 1990.

Early Aluminum tanks made under the following exemptions prior to the adoption of the "3AL" standard were also 6351-T6 alloy tanks.

6498
7042
8107
8364
8422

The will be stamped with an E and the exemption number example: E6498. On most tanks this will have probably been stamped over with X's and "3AL" will have been marked above it. This was supposed to be done about 20 years ago when the tanks came in for their next hydro, but I still see some of these tanks today that have not been marked "3AL".

 

[mike_s]

Kelekealoha

just because they are the older alloy tanks, doesn't mean they are "bad tanks".
Out of the hundreds of thousands of those made, I think a grand total of 12
have exploded. now 12 is a pretty low number percentage wise, but if you're
the guy filling them and it explodes, you'll definately have a different opinion.
So most people (that know about this issue) have a HUGE preference not
to buy those alloy tanks. I've used them w/o problem though. Maybe I've
just been lucky. But I also wouldn't buy any more either. (I don't have my
old 6351 alloy tanks aymore.)

There are still tens of thousands of these tanks safely in use though today.
They just have to be properly inspected is all. However, you will find some
dive shops that will not fill them.


To get these tanks ready for use, you'll need a hydro and visual inspection.
A hydro will typically run you $20-$30 bucks at most dive shops. This
differs greatly per dive shop. I've seen them as high as $50 though and
our local hydro facility does them for I think $12-$15 (but thats the hydro
facility, not a the dive shop. Most dive shops don't actually do the hydro
but take them to a hydro facility.) My local shop charges $25 but takes
them up there and picks them up and then cleans them after the hydro.
A cleaning is not always required, but sometimes the hydro facility isn't
that clean or could leave a residue. A hydrostatic pressure test is required
every 5 years per DOT requirements.

A "visual inspection" will run you about $5-$15 depending on the dive shop.
Here they visually inspect the tank, check its threads and neck for crascking, etc.
This is a industry self imposed requirement and not a DOT requirement. Some
people will argue whether this is actually legally required, but that's a whole
different thread. Personally I think having them inspected at least once per
year is a good thing.

You can then either put "premixed" Nitrox of up to 40% nitrox in the without
any further requirements. People tend to put a large wrap around nitrox or
EAN sticker on the tank though.

If you don't use "premix" nitrox but use "partial pressure blending" nitrox, where
they first put pure oxygen in the tank and then top it off with air from a
o2 cleaned fill whip, then you'll need to have your tank and your valve O2
cleaned. Otherwise any hdyrocarbons in the tank could cause explosion issues
when pure oxygen is filled during the partial pressure fill process. After your
tank is O2 cleaned, it will have a special visual inspection sticker that says the
tank is O2 cleaned and can be used with pure oxygen. O2 cleaning runs
about $25 bucks per tank at one of my local shops, but I'm sure price
will vary per shop. (this is in addition to the visual)

To decide which is best for your, check with how they do things at your local
dive shop and how the nitrox fills are done. Also consider other places that you
might get your tank filled often, such as on weekend trips. This will help determine
which method works best for your diving.

 

[wreckchick]

Since I just did about a zillion hydros in the past week, I'm more than familiar with the difference between the 6351 and 6061 alloys. What I've found is that shops doing visual inspections using eyeballs, mirrors and flashlights are missing some of the cracks on the 6351 tanks. Some of the older visual eddy machines can be difficult to read and people aren't picking up the cracks OR the threads don't continue into the tank itself so the probe doesn't reach the bottom threads where the cracking is found. We're using a new machine called a Vis3 from Advanced Technologies and it's detecting cracks in previously inspected and eddied tanks.

There is nothing inherently wrong with many of the older tanks still in service, but make sure that the visual inspection and eddy current technician is proficient with the equipment and is likely to catch any of the small cracks before they become an issue. I'd personally have no problem diving any of the tanks I've inspected.

Rachel

 

[daniel f aleman]

Rachel, thanks for the Advanced Technologies reference. And, I love the bikini shot on the Boat page on the website.

 

[wreckchick]

Hehe... it's not me, don't get too excited

Rachel

 

[Kelekealoha]

I picked up the tanks today...$60 for the both of 'em. They are in perfect condition, and they're only 7 years old! The original owner is apparently a Navy SEAL, but he badly injured his ear, and can no longer dive. But, you can still imagine the shape he kept his gear in! Anyways, I took it in for a new hydro and vis inspect, and the guys at the shop were impressed with the deal I got. So thank you all for your help! Keep Bubblin