Cylinders Composite Materials

[TomCross]

Hi,
Looking at new cylinders manufactured from "composite" material they had a sticker that said "Do not paint".
Does this apply to all cylinders manufactured from composite materials.
Also notice "Do not stamp" ....
Tom

 

[Buliwyf]

Can't paint. The wrapping needs to be visible to be checked every time you use them.

The epoxy is very hard, like ceramic. Stamping will destroy the tank.

 

[wolfgangmob]

Painting them is the same as painting a metal tank, it hides possible flaws like scratches. Also, as a reminder, if looking at a composite tank make sure it is suitable for diving. Composite tanks are used in other applications such as SCBA gear for fire fighting where the weight saving is highly desired and as fill tanks for paintball or pneumatic air guns. For those uses the tanks are not necessarily designed to handle submersion into salt water that will lead to premature failure and possible even a rupture if the composite gets severely compromised in a way you might not even notice without very close inspection.

 

[ajduplessis]

Composite cylinders is severely positive buoyant making them bad applications for scuba IMO

 

[Scuba Scott]

I love my steel tanks because they are more negatively buoyant.
I imagine a composite tank would be only slightly less buoyant than a similarly sized lift bag.
I don't believe there is any scenario where I would want to use one for scuba and if I tried I doubt I could carry enough lead to sink with one on.

 

[tbone1004]

disclaimer, I am a textile engineer and supply the raw materials for these tanks and other applications. I have done quite a bit of work with composite pressure cylinders, so this is not "gut feelings" or "observational analysis", these opinions are based on research and data.

they do not represent a good value for most scuba applications.
short shelf life due to inability to properly test for damage-hydro's offer literally 0 indication of a composite cylinders health.
highly susceptible to damage with normal use in a diving application. this damage is not easy to detect and requires horrifically expensive equipment to detect if it is not visible to the naked eye, similar to inconel
poor buoyancy characteristics

outside of specialized use for expedition diving, I don't foresee these taking off. they are used in asia where they are considered disposable due to the exceptionally low cost, used in sump diving because of various reasons dealing with cylinder weight and it being easier to carry lead on a weight harness while in the dry sections, but for normal use, I would never invest in one. The risks are too high, and the rewards don't exist