composite cylinders

[imadiver]

Hello you all,
I'm thinking about buying lightweight composite double 15 litres.
Does annyone have expierience with these sets? How do they handle your balance? Are they easy to use one your basic deeper dives with Trimix and stagebottles?

Greets,

imadiver:hmmm:

[Uncle Pug]

If you are referring to the fiberglass wrapped aluminum SCBA cylinders used by firefighters...

They would be horrible buoyany and are totally unsuitable for diving.

[imadiver]

Their Carbon I guess ?!?
:confused:

[Rick Murchison]

In addition to unsatisfactory buoyancy characteristics, composite tanks aren't satisfactory in durability for day-to-day repeated banging around a boat use either. They are designed for limited duty emergency use, and that's what they're good for.
Rick

[roakey]

imadiver,

Welcome to the board!

They’re several materials that the wrapped cylinders use, carbon fiber as you mention and fiberglass. There are two major problems with using any kind of wrapped cylinders for diving. Though light above water they’re horribly buoyant in the water; you’d have to carry a LOT and I do mean a lot of extra lead to get below.

The weight belt you’d have to carry would offset any gain you realized in the lighter cylinders.

Secondly, the wrapping around the metal shell is porus and will allow water to be trapped against the [very thin] metal wall that’s the gas tight “seal” that actually holds in the gas. This will cause corrosion to set in fairly quickly, possibly resulting in a bomb.

Leave the composite cylinders for the firefighters.

Roak

[TRUETEXAN]

For what it's worth concerning composit cylinders. I use a carbon fiber composite cylinder on the Nitrous Oxide system in my hotrod boat, the cylinder is the same one used by firefighters on their Scott airpacks. I use this type of cylinder because it is lighter than the aluminum bottles and in Drag Racing every pound counts, however I can tell you that they would make lousy scuba tanks not only for the bouancy problems, but as Roak mentioned the material can and does absorb water ad this would be bad. The cylinder in my boat is never underwater but even evryday humidity at the boat races and general splashing causes it to absorb water, so I could not imagine them as bing good scuba tanks.

[Bob3]

The confusing comments you're seeing is because no one here in the US is familiar with the composite tanks made by Interspiro, they're not popular here in the US because of their high working pressure.
(nearly impossible to get a full fill)
Interspiro is the only manufacturer that I'm aware of that makes composite bottles suitable for scuba use.
That being said, I LOVE the balance of my steel Interspiros, even if they are a pain in the neck to get hydroed and filled.
The valve design also eliminates a whole host of entanglement hazards as well.

[roakey]

I had heard that there was a European mfg. of composite SCUBA cylinders, but that was the extent of it.

Do you know if they are DOT approved and if approved, if they have a “lifetime” of 15 years like other DOT composite cylinders?

Roak

[Tavi]

In "The Technical Diving Handbook" by Gary Gentile

Page 20 has a picture of Clark Pitcairn wearing steel doubles with 3 composite tanks attaced to them. he is also carrying a stage bottle. (the bouyancy of the composite tanks helps offset the negative bouyancy of the steel)

it also mentions that the cylinders are experimental.

man.... that looks like a lotta air.

it also mentions that these tanks are used mostly in European Countries and that few shops in the US can pump to 4,500 psi

interesting.....

[Bob3]

Do you know if they are DOT approved and if approved, if they have a “lifetime” of 15 years like other DOT composite cylinders?

I kinda doubt if the composite bottles are DOT approved, but I'll check. Some of their old steel cylinders were made in West Allis (Milwaukee) of all places.

The composites are supposed to be good for a 40 year minimum.

How's your Swedish?
http://www.dyk-brand.se/sidor/interspi.htm

[roakey]

Bob3 once bubbled...
How's your Swedish?
I dated a blonde once, does that count?

Roak

[DameDykker]

Just seen them here in Denmark. At 300 bars you really get a lot of air/mix. They are approximately double the price of normal cylinders. Accoding to the text: How's your Swedish? in the link they are made of carbon and polymeres (Swedish is very close to Danish) Though the info on the site is not very detailed. I'll visit the LDS with the bottles tomorrow and get some more info and get it to you as soon as possible.

[DameDykker]

Just checked today. The bottles at my LDS are made of a steel sleeve to contribute absolute no leakage and a carbon fiber reinforcement to provide structural strenght without the weight. They can be filled to 300 bar (4410 psi). They must be hydroed every three years - as opposed to the stell tanks which have a five year period between hydros. The new tanks have been approved by the Danish autorities. And accordig to the LDS most regulators will work at 300 bar delivery pressure without problems, however, air integraded computers might have problems.

I've checked my own Cobra and it has an operating interval of 0-300 bars, maximum pressure 360 bars, so that will be allright if I wanted to change tanks.

Hope that helped!

[JamesK]

Seeing as you mentioned using TriMix with these cylinders, I would like to point something out that I read the other evening.

In a book I am reading, "The Cave Divers" they discussed using full composite cylinders on some early deep exploration of a cave system in Florida, I believe it was Wakulla. They stated that the Helium would actually leak out of the tanks, and they would end up with a mix that had an extremely high PO2. This would happen after long dives, and resulted in some bad cases of oxtox and CNS hits. They said this happened because the He was lighter and smaller then the O2 that was in the tanks. The He being samller, was able to "squeeze" through material that made up the compsoite cylinder. I am not sure how accurate this is, but it is enough to make me want to do a LOT more research before considering using a full composite cylinder.

[DameDykker]

JamesK

You might very well be right. I used to work in a plant where the process involved Hydrogen flames, therefore, Hydrogen and Oxygen was piped in a lot of places. To test the absolute leak proof condition of all that tube every single piece was leak tested by applying hard vacuum on inside the fitting and then spraying Helium on the outside as Helium has extreemly small molecules. Inside the unit after the vacuum pump would then be a Helium detector to show any leaks. It is very difficult to get anything that leak proof! However, the actual mnufacture of the bottles will most likely know if their cylinders can be used with Helium/Trimix.

[Inspector]

Gentlemen,
Have a look at www.luxfercylinders.com then click on "scuba" It will provide current information on Luxfer's composite diving cylinder. Then goto www.psicylinders.com and click on the article titled "Presidents corner" You will find a comprehensive document on said same cylinders.

[canadiancavedigger]

and I ran across this domestic manufacturer that has DOT approved cylinders,whether these are scuba approved I do not know ..usefull?


http://www.bactechnologies.com/cylind.htm

[Daryl Morse]

Seeing as you mentioned using TriMix with these cylinders, I would like to point something out that I read the other evening.

In a book I am reading, "The Cave Divers" they discussed using full composite cylinders on some early deep exploration of a cave system in Florida, I believe it was Wakulla. They stated that the Helium would actually leak out of the tanks, and they would end up with a mix that had an extremely high PO2. This would happen after long dives, and resulted in some bad cases of oxtox and CNS hits. They said this happened because the He was lighter and smaller then the O2 that was in the tanks. The He being samller, was able to "squeeze" through material that made up the compsoite cylinder. I am not sure how accurate this is, but it is enough to make me want to do a LOT more research before considering using a full composite cylinder.I can't comment on the specific case to which you refer, but helium is commonly used for leak testing because of its propensity to find its way through small porosities. Hydrogen is also very slippery, but since it has explosive tendencies, it's not used for leak testing. Any composite tank intended to be used for helium would have to have been designed and tested for such a purpose.

[Bob3]

Nothing like reviving a 2 year old thread. ;)
Since this thread started back in '02, Luxfer has come out with a composite scuba cylinder, but the cost vs. life time of the critter makes it a big turnoff.
whether these are scuba approved I do not know ..
Those are the SCBA bottles, not really suitable for scuba.
It's still hard to beat a good steel bottle when it comes to price vs life expectancy.
Maybe in a few more years... :crafty:

[Curt Bowen]

I kinda doubt if the composite bottles are DOT approved, but I'll check. Some of their old steel cylinders were made in West Allis (Milwaukee) of all places.

The composites are supposed to be good for a 40 year minimum.

How's your Swedish?
http://www.dyk-brand.se/sidor/interspi.htm

Bob


I was thinking of these cylinders for my rebreather and foreign travel.

The 18 cfft / 3 liter cylinders i use now are heavy for air travel.

Once I get to the destination I am diving, its easier to just ad weight.

[DrDuktayp]

The local LDS was filling several composite tanks the other day. He is a 'tech' diver and instructor. Anyhow, I was asking about them and he was quick to point out that the composite construction had very poor bouyancy characteristics. He said that the composite construction was great for rescue work, but not for diving.

Now maybe the bouyancy might be okay for those that dive wet.

DrDuktayp