Overfilling aluminum tanks

[ShakaZulu]

Still waiting on the DIN valve clarification...

Yes they do, and so should all of us. Really makes the O-Ring blowout problem disappear...........

 

[WarmWaterDiver]

They don't necessarily 'tend' to do this - in the Dutch Caribbean finding tanks with DIN valves or convertible yoke-or-DIN valves was a real challenge this May. The only spot we found the 'convertible' tank valves on Curacao was the dive operation associated with the Seaquarium and Breezes resort - catering largely to the American tourists. The 'Dutch' dive shops we used for other dives had only tanks with yoke tank valves.

I've found this to be the case in other such areas - for example French Polynesia - yoke tank valves are pretty much the standard when we visited there in November 2002.

What Europeans do in Europe may be another matter.

And I think filling a 'rigid' pressure vessel to its test pressure with gas and circumventing safety devices like burst disks is akin to playing Russian roulette with a semi-auto pistol instead of revolver. The beauty of pressure testing using a virtually incompressible fluid is if there is loss of containment, only a tiny volume need escape for a huge decrease in pressure - hence why hydro (water) testing is done. This is true whether aluminum or chrome-moly steel in my book - ever check the ductile to brittle transition temperatures for chrome-moly steels? Filling till stickers crack - I can only say "Not In My Back Yard"!

 

[pasley]

All I have to say is....
Darwin Awards and
http://www.connected.bc.ca/~baquatics/explode.html
http://www.scubabomb.freeservers.com/

If I were a customer, I would expect to be informed when these tanks were being overfilled past their limits so I could leave the store.
'nuff said

 

[Al Mialkovsky]

Scary photos Pasley.

I don't overfill them by more than 100 pounds, ever. I try to get them spot on actually.

 

[hecker-the-wrecker]

I bought a new alumminum 100 & the l.d.s. always fills it to 3500. This is the pressure with the tank cool, at the dive site. how much will 200 or 300 psi effect the life of this tank(per fill)??? ( It won't blow up tomorrow, will it?)

 

[JS1scuba]

I bought a new alumminum 100 & the l.d.s. always fills it to 3500. This is the pressure with the tank cool, at the dive site. how much will 200 or 300 psi effect the life of this tank(per fill)??? ( It won't blow up tomorrow, will it?)

The aluminum 100 cuft tank has a service pressure of 3300 psi. All service pressures are calculated at 70 degrees F. Where we are here in Lake Havasu AZ it's normally 100 F in the summer filling cylinders in that temp is a bear. It's not uncommon for our cylinders to be filled here a few hundred PSI over the working pressure. Once they hit the water (60 degrees they are at full working pressure. Each degree of temp change affects the cylinder by 5 PSI.

On the other side of the coin, if the aluminum cylinder is regularly being filled over its working pressure it can cause stress and ultimate damage to the cylinder, which will only be found out at the 5 year hydrostatic testing.

As to blowing up. If the cylinder is valved properly with a proper saftey assembly, (burst disk) the probability of a cylinder blowing up is insignificant, provided of course this is a realtively new cylinder (under 10 years old). If the cylinder sees lots of fills, from full to empty (like in the Carribean) those tanks should probably be taken out of service after 10 years. Remember aluminum is a brittle material it only has a certain amount of stretch. If you care for the cylinder properly, service the valve each year at the VIP, repalce the saftey with each valve sevice and keep the fills within the working pressure an aluminum cylinder should serve you well for a very long time. I have some personal cylinders that are more than 15 years old and are perfect.

As to your LDS filling your 3300 psi tank to 3500 psi. It probably wont harm it but it is over the spec of the tank. Then again is his gauge accurate ?

Regards,

 

[hecker-the-wrecker]

I've tried both of MY spg's and I know my reading of 3500 is accurate, my tank seems to be the only one to get filled like this consistantly,(of our group) maybe because it's black??

 

[ussmeg]

The burst disc is designed to fail well below the hydro test pressure. In the event of a serious overfill situation or other condition where the service pressure could be grossly exceeded (fire, etc) the disc is supposed to fail to vent the tank before it is at risk of failing. But people who overfill tanks have a habit of installing two burst discs which defeats the purpose. If there are a pair of 4K discs in the valve, the tank is going to fail first.

The Burst Disc is supposed to be set at the HYDRO Pressure. Its very dangerous over filling Aluminum tanks. If you ever get a chance to see a cracked one you won't even want to be in the store when aluminum's are being filled.
Paul

USSDPV Hydro #D565