Help Validate Facts on Overfill to LDS

[nauidiver2004]

I walked in to a diveshop to pick up fins one day, and the owner of the shop was overfilling some tanks. Well the burst disc failed on one of them and the neck popped off. This thing took off like a missle through the roof and nearly took me with it. Take it from someone who has seen these things pop: You don't want to do this.

The same diveshop has tried to kill me a few times since then. It may not be the tanks, but the poor care they have recieved. This shop is The Aquatic Center in Gainesville, Florida. Please avoid at all costs.

Thanks,

-V

There we go, first hand account that overfilling cylinders reduces the safety margin

Ken

 

[PRL]

But we're saying here that at 130F tank temperature, it's legal to overfill by 25%...?

That's a LOT.

From my understanding. Service pressure is directly related to temperature and will rise with temperature. The service pressure stamped on the neck is at 70F standard. By filling a 2400psi+ tank to 2940 at 130F you are filling the tank to the service pressure, Not overfilling it. If it was any other way than every time we have a tank in a hot car we are breaking the law because the pressure in the cylinder will be higher than the stamped pressure on the tank.
There are two guidelines, one for aluminum tanks only, that states that no 3AL should be filled over the marked pressure on the neck. In this case it seems that for aluminum tanks the service pressure on the neck is an absolute pressure for filling. (probably because most failures related to the 3AL cylinders happen at fill time)
And a second guideline. A fill rate of between 300 - 600 psig/minute is recommended. This should keep the temperature lower than an expected temperature in lets say a hot car trunk.

 

[wettek]

True, the bands would have also streached but the cylinder wall would still have deformed around the band. If you don't believe that, then explain how a water jet machiene can cut through plate steel

This is because water jet cutters run at 10,000 psi + and use an abrasive mixed into the water stream. How a steel tank would deform from a 1/2 mm thick cylinder band is beyond me. I think the band retainers would let go or the band stretch before a tank wall would deform around it.

 

[PRL]

BTW
130F = 327.59K
70F = 294.26K
The service pressure of a 2400psi+ tank at 130F would be 2671.87psi+, add the 10% for the plus and the tank should have 2939psi (not 2940psi sorry)

 

[nauidiver2004]

This is because water jet cutters run at 10,000 psi + and use an abrasive mixed into the water stream. How a steel tank would deform from a 1/2 mm thick cylinder band is beyond me. I think the band retainers would let go or the band stretch before a tank wall would deform around it.

Think of the steel on a molecular level. As the tank expands the molecules flow around the bands.

 

[wettek]

Think of the steel on a molecular level. As the tank expands the molecules flow around the bands.

This is reality, not a scene from the matrix, The steel bands will not "flow" anywhere.

 

[wettek]

This is reality, not a scene from the matrix, The steel bands will not "flow" anywhere.

Sorry, meant to say the steel of the tank is not going to "flow" around the bands.
I will just morph back into my wetsuit.

 

[PhotoTJ]

If the steel expands, and encounters resistance, it will expand around the area of resistance.

 

[DEEPTEK]

All tanks sold in the UK, France, have M-25 valves. Thye do not have Burst dics.

But they put 4000 in them in Europe, you just have to stack 2 or 3 burst disk. In Italy they said it was ok.

Heaven forbid that you have the FIRST steel that explodes and it gets found out that it gets found out that it was being overfilled. Any attorney I know would love to have that case.

 

[wettek]

If the steel expands, and encounters resistance, it will expand around the area of resistance.

I would love to know where I can get a jacket whose Tank strap attachments will hold back a tank sufficiently to force a tank to distort around it. There is an awful lot of force required to distort a tank.Tough gear.