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  #11  
Old 01-06-2007
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We used these on our canal boat in France, and we were amazed to find them not yet on this continent.
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  #12  
Old 01-06-2007
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Before I retired in October 2005, I ran the program in the U.S. DOT that monitored the compliance for hazmat packaging, including compressed gas cylinders. My inspectors went to companies that manufactured such packaging for compliance with U.S. regulations.

I note that the "Progress" link on the web site indicates that as of 2005 or 2006, they were about to begin production of "DOT approved" 20-lb. cylinders. If they are now on sale, one assumes they received that approval, but I am checking with my old mates to confirm this.

New packaging technology for hazmat is accommodated through a "special permit" program (used to be called an "exemption" program). New packaging has to meet or exceed current regulatory requirrments. If it does, it gets a special permit number that must be marked on the packaging. Those who have seen these cylinders should find a "DOT-SP" marking followed by four or five numbers. The old exemption program required "DOT-E" followed by four or five numbers.

Composite tanks have been around for years, and are widely used as dive tanks and oxygen tanks for fire fighters. Most also have a 15-year useful life, at which time they are supposed to be disposed of.

Last edited by SailinJay; 01-06-2007 at 01:58 PM.
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  #13  
Old 01-06-2007
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"retrofit my current tank."
There used to be a place selling OPV valves online for about $9.95 if you wanted to do the retrofit youself. As usual, caution needs to be taken for sparks and explosive gasses. But with the added expense of recertifying older cylinders...they may not be worth retrofitting, IIRC if they are more than 5 years old some places won't fill them without charging you another $30++ to recertify them. And some places that swap tanks (rather than filling while you wait) will just take your old tank, regardless of valve and date, and swap it for you. Places that do BBQ supplies are more likely than marine suppliers.

Sailinjay-
"Composite tanks have been around for years, and are widely used as dive tanks" Composite SCUBA tanks?? To the *civilian* market in the US? AFAIK not at all.
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  #14  
Old 01-06-2007
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Hello--

The DOT defines any cylinder with a pressure above 900 psi as "high-pressure" and any cylinder below that as "low-pressure." In reality, most high-pressure cylinders are above 2,000 psi and most low-pressure cylinders are below 500 psi.

The normal requalification period for high-pressure cylinders is every five years, but some can go longer if in dedicated service, i.e., the same gas all the time. Low-pressure cylinders dedicated to propane use, such as gas grill tanks, can go 12 years before needing requalification. You are correct that many places simply swap out older tanks for newer tanks just to avoid the hassle.

I'll do some checking and get back to you on the point about the composite SCUBA tanks.

Last edited by SailinJay; 01-06-2007 at 05:32 PM.
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  #15  
Old 01-06-2007
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Quote:
Originally Posted by dawndreamer
We used these on our canal boat in France, and we were amazed to find them not yet on this continent.
Is it possible that our bureaucracy is slower than European bureaucracy?
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  #16  
Old 01-08-2007
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I stand corrected

Hellosailor--

I checked with my sources and you are correct: there are no composite tanks currently approved for dive tanks. I am told that approval is being sought for such usage, but the DOT engineering staff says that it is highly unlikely given what one would expect regarding the issue of corrosion by salt water.

Also, the cylinders manufactured by the Lite Cylinder Co. are authorized by DOT special permit (DOT-SP-13957) and the DOT engineers indicate they are excellent.
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  #17  
Old 01-08-2007
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Jay, I would have expected an FRP tank to be immune to the corrosive effects of salt water, certainly more so than metal tanks which always suffer galvanic problems are (for steel) rust pitting as well. But the entire dive market is a small one, perhaps the bottom line is simply that there isn't a big enough market to cover the costs of getting FRP tanks certified--and then fighting the existing distributors to get them into stores. I've heard some ugly tales about distribution in the dive shop business. Then too there are issues about US vs global distribution, often the standards conflict and the same product can't simply be sold to a global market. And if the tanks can hold higher pressure (like NASA's throw-away tanks used in the Apollo program) the dive shops won't like that either, because new compressors cost money.
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Old 01-08-2007
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Quote:
Originally Posted by hellosailor
And if the tanks can hold higher pressure (like NASA's throw-away tanks used in the Apollo program) the dive shops won't like that either, because new compressors cost money.
I don't think you would see dive shops buy new compressors. They can't pay for the ones they have.

The problems I see with composite scuba tanks is

a) They will be very boyant at the end of a dive (not good).

B) A scuba tank is used quite differently than most other tanks in that they get pressurized 3000 to 3500 lbs quickly and much more often, some times two or three times a day, than say a propane tank.

C)When a air is compressed it generates heat and will that heat cause a composite tank to degrade over time? not to mention the continual stresses of refilling. Which is why steel and aluminum tanks need to be tested regularly.

D) Many divers dive nitrox which is a higher level of O2 than air. When filling a tank with nitrox mix the tank is often partially filled with 100% oxygen then filled the rest of the way with air. 100% Oxygen and hydrocarbons don't play well together. Is a composite tank going to hold 100% Oxygen without any adverse affects?

E) Did you ever see the way divers treat their tanks?
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  #19  
Old 01-08-2007
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Quote:
Originally Posted by Sailormon6
Sailormitch, from your avatar, it looks like you're in the Annapolis area. I had the same problem and found a place near Annapolis to retrofit my aluminum tank. It cost about $30. The place is located on the east side of Solomon's Island Rd., south of Annapolis. It's near the shopping plaza where the small West Marine is located, and on the same side of the road. I don't remember the name of the place, but it's something like Annapolis Gas, or Anne Arundel gas. It only took about 30 minutes to do, and they did it while I waited.
Sailormon -- I live near Baltimore and get to Naptown quite often, so thanks for the tip. I'll check them out next time I go down that way.
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Old 01-08-2007
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HI Brezzin:

Easy on the diving gasses. The object of diving gas mixtures is to reduce the oxygen fraction not to increase it. Pure O2 is for aviators, not divers.
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