Overpressurizing / Overfilling steel tanks

[DA Aquamaster]

Whitelightnin once bubbled...
I currently use oxygen tanks for storage banks on my steel 72's. They (oxygen tanks) are rated for 2250 psi. I fill them to 2500 psi. I have heard of people using them as storage banks & filling them to 3500psi. Does anyone on here know of this being done?

I will hot fill non plus rated steel 72's to 2400-2500 psi, but it's a situation where when they cool to room temp they are right around 2250-2300 psi. I have gotten pretty good at feeling the temp of the side of the tank and knowing how much of an overfill I need to use to get the actual service pressure at room temp.

However I don't really regard this as an overfill as if I filled the tank very slowly to 225o psi at 70 degrees and then took it outside, where it was 105 degrees, the tank pressure would increase but it would not technically be overfilled as the service pressure is based on the pressure at room temp.

I think there is a critical difference between pushing a tank 300-400 psi to get a good fill when it cools and intentionally putting more cu ft of air in the tank that it was intended to hold.

 

[quimby]

Scuba_Vixen once bubbled...
They are not made from chromium-molibdenum (chome-moly) alloy.

Check any of the cave country fill places, noted for overfills, and they'll tell you the same thing.


Darlene

Then how can you explain DOT 3AA or even ICC3AA
chromium-molibdenum steel is chromium-molibdenum steel

 

[ImDiverDan]

I've heard that some folks have overfilled steel 72s. Not that I'd ever do this, but what's the typical overfill pressure?

 

[The Fresh Prince]

habitually take mine to 3000

 

[dsgobie]

10%

 

[Genesis]

I will go to the "+" rating (which they had in the first place) but not beyond.

Then again I don't overfill ANYTHING; my compressor is in my garage and I prefer that the contents, and all my body parts, remain intact.

 

[DA Aquamaster]

10% is 2475 psi and on a hot day I will fill to around 2600 psi to get an honest 2475 psi at around 70 degrees. I have done this for nearly the last decade and the tanks continue to pass their hydros with flying colors.

I would not even remotely consider pushing one to what amounts to a service pressure of 3000 psi as the 5/3rds hydro test pressure for a steel 72 is only 3750 psi. Pushing a steel 72 that hard is not smart and doing it routinely is a wonderful way to help your spouse collect on your life insurance.

 

[Genesis]

2600 is about where I "hot fill" them; they don't get as hot as their HP cousins as they are not cranked as high on the pressure.

 

[Rick Murchison]

I have only one... I don't fill mine over 2475.
I can't even count the times some shop rat has filled it to 3000.
So far still passing hydro, and it just passed its 31st birthday.
Rick

 

[Genesis]

...he's standing next to it when it goes "boom"

If I'm filling it in my garage, then I'm the guy who gets my arm, leg, or head blown off.

I'd be upset if the tank failed hydro as a consequence of this abuse, although frankly, I doubt it will happen - the specifications for steels say that they must pass 10,000 cycles to hydro pressure without exceeding their allowable stretch. So long as you do not STORE them with a gross overfill, they are unlikely to fail hydro on that basis. Possible, but unlikely.

However, if there is hidden trouble inside (e.g. line corrosion that you don't know about, as it happened since the last time you had the valve off) the failure mode may not be a hydro failure but rather a "boom."

Again, the DESIGN of the cylinders is supposed to preclude that, in that the standards require that INTENTIONAL damage be done (in the form of scoring to represent corrosion and/or physical damage) during the certification process and that under these circumstances the tank must leak before it explosively fails.

Nonetheless, I am not interested in being the guinea pig when the compressor is running in my garage.....