What pressure would you fill a pair of AL80s to?

[jlillest]

In the interest of generating discussion, let's see what people would be comfortable filling their aluminum tanks to. Assume the following:

1. You want the most gas you can get without endangering the longevity of the tank from stress/fatigue
2. AL40, AL80 or similar common aluminum tank rated to 3000psi.
3. You're filling for a dive and will use it within a week or will bleed it.
4. Tank is in viz (which means it has good hydro) and is "good" aluminum (not older crack-prone models)
5. Choose the pressure you're aiming to get after the tanks cools

[Superlyte27]

3600

[Superlyte27]

3600

haha I just noticed the poll.

[cerich]

hmmm, having inspected thousands of tanks in the day and taken a few courses on them alum gets no more than a 10% overfill from me, expecting a cool to ~rated pressure. They scare the #### out me to overfill them. They just aren't that forgiving to repeated overfilling, the alum stretches, does not contract and gets lots of little cracks in the alum, that is why the visual eddy process is now used. newer alloy alum tanks still have the same tendencies, just not as bad by far but they still get respect.

Steel tanks that aren't exemption cylinders...what will the compressor do?

[jlillest]

haha I just noticed the poll.

Yeah, I was a bit slow in getting the poll up. Apparently you have to create a thread first and then complete the poll as a second step.

[MORGAN]

3300 hot, 3000 cool.

[Jax]

Interesting. Some people fill to 3300 to cool to 3000, and others fill to 3200 to cool to 3000.

Is it a function of the compressor? Faster-filling = more heat = higher fill level to cool to 3000?

[next gen]

3000, because of the elasticity of steel I'm ok with pumping steel tanks to 3600, Aluminium tanks I do not like to over fill because they fatigue faster than steels. An over pumped aluminium tank scares me.

[cerich]

I would guess that the folks that fill to 3200 to cool to 3000 have more patience than those of us that fill to 3300...the 3300 crowd fills faster. The 3200 crowd is more cautious.

Interesting. Some people fill to 3300 to cool to 3000, and others fill to 3200 to cool to 3000.

Is it a function of the compressor? Faster-filling = more heat = higher fill level to cool to 3000?

[firemedic1015]

I don't think Jon is looking for how high do you fill so that it cools to 3000... I think he's looking for more of a how high would you fill it to go on a dive, particularly an exploration type dive. It might be hard to get an honest answer on an open forum but "rumor has it" that in the circumstances described, 3900 shouldn't be a problem.