Air in nitrox tanks?

[Scared Silly]

Go a head and get certified as said it is worth the knowledge. In the mean time take all of the stickers off. Of course if the person doing the hydro or vis is doing their job the stickers will come off anyways. Otherwise how else would they discover the little gems Net Doc described?

 

[Papa_Bear]

Use 21% Nitrox then you can leave the stickers on! Under 40% use anything you want and have fun, I switch between 21% and 32% all the time! If you leave the sticker on then some other user will have to check for themselves and that would be the safest way to go!

 

[IceBergSlim]

Heck, I know someone who found a BOLT ground flat under a sticker. The tank had been drilled to remove it from service and someone threaded a bolt with a bit of epoxy and expected that to hold. YIKES!

Now THAT is somthing I would love to see. You have any photos of that particular DIY mod? I have seen the "Honlulu Hydro" but a full on, tank-wall re-surface job is one for the scrap book.

Please share if you have one layng around.

 

[Papa_Bear]

Go a head and get certified as said it is worth the knowledge. In the mean time take all of the stickers off. Of course if the person doing the hydro or vis is doing their job the stickers will come off anyways. Otherwise how else would they discover the little gems Net Doc described?

By doing a VIP! You can hid it from the outside, you can't on the inside! A bolt or screw will be a sore thumb on the inside of the tank!

 

[The Chairman]

By doing a VIP! You can hid it from the outside, you can't on the inside! A bolt or screw will be a sore thumb on the inside of the tank!

No need to even pull the valve this way. Corrosion on the outside is just as bad as it is on the inside. Stickers should be removed every year, even those cool ScubaBoard stickers. I see that many shops are destroying a failed tank by cutting the threads and the o-ring surface with a cold chisel and a three pound sledge. I deface the neck in four places just to be sure.

For those interested, Steve Fordyce (PSI #4) either had the tank there when I took my PSI course or had a picture of it. If the owner had gotten hold of an Inspection Sticker fraudulently, then this story might have had a sad ending.

 

[Luis H]

No need to even pull the valve this way. Corrosion on the outside is just as bad as it is on the inside. Stickers should be removed every year, even those cool ScubaBoard stickers. I see that many shops are destroying a failed tank by cutting the threads and the o-ring surface with a cold chisel and a three pound sledge. I deface the neck in four places just to be sure.

For those interested, Steve Fordyce (PSI #4) either had the tank there when I took my PSI course or had a picture of it. If the owner had gotten hold of an Inspection Sticker fraudulently, then this story might have had a sad ending.

I hope that they are aware that they are required (per CFR 49 section 180.205 General requirements for requalification of cylinders.) to get the owners permission before anyone can destroy the threads, O-ring seal, or drill a hole in any cylinder.

The requalifier is authorized (and required) to stamp X's over the DOT specification number and the marked pressure or stamp "CONDEMNED" on the shoulder, but not destroy the intedrity of the cylinder. See quote below.


I find it amazing that someone would put a screw to try to patch a condemned cylinder. It is just hard to comprehend what kind of an idiot would do that. All I can think of is that someone was trying to defraud someone else by selling them the condemned cylinder, with total disregard to all the possible outcomes.

I can understand why some LDS would want to go beyond the regulations to keep cylinders from being reused, but breaking the codes is not the proper way. They need owners consent to damage the O-ring seal, etc. or they are destroying private property.

49 CFR Ch. I (10-1-06 Edition)
180.205

(2) When a cylinder must be condemned,
the requalifier must
(i) Stamp a series of X's over the
DOT specification number and the
marked pressure or stamp "CONDEMNED"
on the shoulder, top head,
or neck using a steel stamp;
(ii) For composite cylinders, securely
affix to the cylinder a label with the
word "CONDEMNED" overcoated with
epoxy near, but not obscuring, the
original cylinder manufacturer's label;
or
(iii) As an alternative to the stamping
or labeling as described in this
paragraph (i)(2), at the direction of the
owner, the requalifier may render the
cylinder incapable of holding pressure.
(3) No person may remove or obliterate
the "CONDEMNED" marking. In
addition, the requalifier must notify
the cylinder owner, in writing, that the
cylinder is condemned and may not be
filled with hazardous material and offered
for transportation in commerce
where use of a specification packaging
is required.

 

[Scared Silly]

By doing a VIP! You can hid it from the outside, you can't on the inside! A bolt or screw will be a sore thumb on the inside of the tank!

Um, reread what I wrote. I was describing a visual inspection. Which starts by first examining the OUTSIDE of the cylinder. A cylinder can fail due to the outside wall being compromised just as as well on the inside. So if I see a reason to fail a cylinder due to the outside wall being compromised I will not bother removing the valve.

 

[castanagajt]

Thanks all, these are all great posts on this thread. I brought it to my my number #2 favorite shop with all 8 tanks and they found that some were 83's instead. The hydro and vis was much more affordable than anyone else. Especially, thanks to Scared Silly, Luis H. and Papa Bear for going the extra mile on this one!

 

[DA Aquamaster]

nope not certified for nitrox and I am debating is it worth for me to even be certified for nitrox. As for the tanks they are definitely 76's.. A few of the tanks had a manufacturer named scubapro and the valves are all from a company named beuchat. Strange tanks, indeed.

They are Faber 75.8's. Scubapro sold them in the 1980's to maybe 1990 or so.

They are great tanks combining all the nice qualities of a steel 72 with the slightly extra volume of a 2400 psi service pressure. They hold 69 cu ft at 2400 psi and achieve the 75.8 cu ft at 2640 psi, so the plus rating is helpful if you can get it.

The downside is that they are likely to be confused with steel 72's so watch for short fills and don't expect the same 3600 psi cave fill a north florida shop would give a faber 95 of the same vintage and made to the same engineering standard. (But at 3600 psi they would hold 103 cu ft as they are a 12 liter tank just like a steel 72 or the shorter and slightly fatter HP 100.

----

Mileage will vary on nitrox fills. Some shops still require tanks to be O2 clean even if they fill from a bank, stick or membrane system. In that case the "required" tank cleaning is often just a carefully guarded revenue source. In this area for example, the shop owners meet on a monthly basis and discuss and establish local policies and practices (and probably pricing, but that would be illegal). One of the end results is that tanks that are not O2 cleaned and also banded with those really horrible and totally meaningless nitrox bands cannot be nitrox filled even if a shop does not use partial pressure blending. They also will for the most part refuse to honor out of the area VIP and O2 clean stickers (fill express etc.)

It is all very annoying so I get my gas from one reasonable shop I have found in the area that will let you do your own O2 cleaning and provide the training to do it. Eventually shops with overly restrictive fill policies will drop them if consumers take their money elsewhere.

Where O2 clean does matter in on O2 mixes over 40% and on tanks that are filled with a partial pressure blend process where any mix over 40% is intorduced into the tank.

One of the ironies here is that a clean tank is not as vital as a clean valve. A dirty tank adds fuel, but it is not in an area also likely to see an ignition source. Scuba valves on the other hand are not designed for O2 service, open very fast and may have areas in them subject to compression heating where sudden bends or restrictions occur. So a clean valve is vital to safety but there are no doubt shops out there that insist on O2 clean tanks don't look twice at or clean the valve. If you really need an O2 clean tank, make sure you also have the valve O2 cleaned as well.

 

[SparticleBrane]

They are Faber 75.8's. Scubapro sold them in the 1980's to maybe 1990 or so.

They are great tanks combining all the nice qualities of a steel 72 with the slightly extra volume of a 2400 psi service pressure. They hold 69 cu ft at 2400 psi and achieve the 75.8 cu ft at 2640 psi, so the plus rating is helpful if you can get it.

The downside is that they are likely to be confused with steel 72's so watch for short fills and don't expect the same 3600 psi cave fill a north florida shop would give a faber 95 of the same vintage and made to the same engineering standard. (But at 3600 psi they would hold 103 cu ft as they are a 12 liter tank just like a steel 72 or the shorter and slightly fatter HP 100.

Thanks for that -- I was obviously wrong. Learn something new every day!