AL80 @ 3500psi? Good or Bad? Or doesn't matter?

[frankc420]

The last time I had my tanks filled, which was about 1.5-2 months ago, they were filled to 3200psi, the temp was about 55-60, maybe less at the time. I was told that once the heat in the tank dropped, the psi would drop with it.

Well, I brought them home and stored them, I'm going diving this weekend so I wanted to check my seals and my new transmitter on my 1st, so I hooked up to both tanks and both were reading 3500psi. I drained them to 3200 and put the cap back on (wasn't too comfy with them reading 3500..) Funny thing, I'm going to guess the air temp between my storage room and carport is about 10-20 degrees difference, so after I drained out the 300psi from each tank, they started going back up again?

So the question stands, should I have left the tanks alone and been happy with the extra? Or did I do the right thing by releasing some of the pressure? I obviously don't know too much about my own tanks... I do know my 1st stage is rated to 3500psi (It's on the stage) and the valve is rated to 3000psi.. I don't know how much extra they can hold, that's why I was nervous about it!

 

[Dixie Sands]

Bad 4000psi is proper. Go complain

 

[SparticleBrane]

I would have been happy with the extra...

 

[SteveAD]

Overpressurizing tanks isn't a great idea, in fact it's illegal, but the violator would be the shop who filled it, not you. As far as safety goes, your AL80s have been tested up to 5000 psi (that is hydro test pressure), so the tank is unlikely to fail below that. they are also equipped with a burst disk, which is the pressure equivalent of a fuse. the burst disk is designed to fail well below test pressure and empty the tank. regular overfilling will weaken the burst disk and eventually cause it to fail, and might in the long term cause sufficient metal fatigue to cause the tank to fail hydro. but I would not worry about the tank blowing up in your garage.

 

[ClayJar]

I've never had it come up... it's always the other direction for me.

I would've used it as an excuse to dive the air out of them as soon as possible... but then again, any air in the tank is an excuse for me to dive the air out of it as soon as possible, so I'm not much help.

 

[SparticleBrane]

Fill 'em till they're round.

 

[frankc420]

Overpressurizing tanks isn't a great idea, in fact it's illegal, but the violator would be the shop who filled it, not you. As far as safety goes, your AL80s have been tested up to 5000 psi (that is hydro test pressure), so the tank is unlikely to fail below that. they are also equipped with a burst disk, which is the pressure equivalent of a fuse. the burst disk is designed to fail well below test pressure and empty the tank. regular overfilling will weaken the burst disk and eventually cause it to fail, and might in the long term cause sufficient metal fatigue to cause the tank to fail hydro. but I would not worry about the tank blowing up in your garage.

Thanks!

The above does make me wonder, how do tanks blow when dive shops are filling them if they have a burst disk?

 

[SparticleBrane]

Can't say I've ever heard of a tank blowing up while filling unless it was 6351.

 

[scubamurray]

For the short time I worked at a shop I filled up enough that when cooled the pressure did not drop below 3000 and bring on complaints.

A cracked neck is a risk with aluminum tanks, but no risk when tank visual plus with electric probe through the neck threads.

Very old steel tanks before careful screening could have water in them, rust and have weak points that allow splitting at lower pressures.

Proper procedures like proper burst disc (you could have yours checked by a shop) vis hudro etc. means little if any real risk to user, filler, transproter etc,.

Your gauge could also have a variable reading from shop gauge, which might be calibrated differently.

Hope this helps.

Bob Murray

 

[dsteding]

Thanks!

The above does make me wonder, how do tanks blow when dive shops are filling them if they have a burst disk?

The tank can let go below the burst disk pressure-but that seems to only apply to the old AL tanks that had problems.