steel tanks?

[DA Aquamaster]

If it gets dropped in the water (which I have never seen happen, but I'm sure it occasionally does), just open the fill whip for a few seconds and blow any water out; it will quickly dry the fill whip.

The water baths let water in the tank myth is in fact my favorite myth.

Having water in the fill whip or in the tank valve is basically the only way to get water inside a tank - other than a really poorly maintained compressor with an inadequate water separator and dessicant in the filter.

The irony here is that the tank monkey at the wet fill station is well aware of this risk and will be more likely to routinely crack the valve on both the tank and whip to remove any water before connecting the two.

The guy in the dry fill station will be all warm and comfy in the knowledge that there is no water around - and will fail to crack the valve on the tank, allowing that drop or two of spray, water, rain, inside the valve to get blown inside the tank.

Hot fills are also common. I know very few shops that fill anything other than O2 at 50 psi per minute or less and not many will come back to top off the tank after it cools, so a 2800 psi fill in your 3000 psi tank is about average.

If the shop does not want to feel the shoulder to estimate the temperature and then add 200-300 psi over and above the service pressure as needed to ensure the tank is full and at rated pressure when it cools to room temp (and many do not under the mistaken belief they would be overfilling the tank) then filling in a water bath is the only reasonable way to ensure a good fill in a short period of time.

 

[SparticleBrane]

DAA -- If I am standing around while my tanks are being filled (frequently in cave country and most other places as well), I make sure that my cylinders don't have any water left in the valves. I don't leave something like that up to the fill station guy; I like to be 100% sure that water doesn't get in, or that I am at least doing what I can do to minimize it.

 

[Indian Valley Scuba]

Hey there Sparticle, I'd like to thank you for checking out our website www.IndianValleyScuba.com . There's a ton of great info there and we're not shy about sharing it! Thanks for quoting us.

 

[SparticleBrane]

Anytime
I did like your "free VIP & free hydro for life of the cylinder" promotion, just disagreed with some of the info posted about fills.

 

[Indian Valley Scuba]

Not a problem my friend, we all have our own opinions and that's why they make chocolate and vanilla! Great to have an intelligent exchange here!

The Free Lifetime Tank Inspection program is awesome, and it will usually pay for the tank in five years or so. We sell an awful lot of tanks that way. All inspections, including hydro's, are done in-house and turnaround is one to two days. Can't beat that!

 

[kidsdream]

Current LP and Mid pressure (3442) tanks are made precisely the same way, using the exact same materials (sort of like a Lexus's and Toyota being made on the same assembly line using the same engine).

Yes the sampling/test pressure is different, but this is a regulatory matter not a matter of actual capability or quality

Can you state any instance of accident or failure mode being related to fill pressure itself causing the failure of the tank itself (not withstanding that you must use a burst disk/valve assembly suitable for the pressure you expect to fill the tank to)?

That said, I think your shop's life time inspection policy is outstanding.

You (or the filler) might get seriously hurt filling a low pressure tank to 3,500 psi.

I am sure the poster was just using the physical size as an example, not the thickness of the material, pressure rating, burst disc rating, etc.

I would suggest you find a friendly local dive shop that will talk to you and show you how the tank neck markings are, so you can get a better handle on what you are looking at.

 

[Indian Valley Scuba]

Thanks for the compliment on our cylinder inspection program.

To answer your other question though, i am hardly a repository of cylinder failure statistics, however, in spite of local traditions, there are some rules here.

FACT: The US Code of Federal Regulations establishes the requirements for pressurizing steel cylinders beyond their stamped service pressure. 49CFR173.302 sets forth the requirements for pressurizing cylinders 10% in excess of its marked service pressure.

Yes of course anyone has the option to fill any cylinder to whatever pressure they wish; however, it will be interesting to see their position should they find themselves in court attempting to defend themselves for a practice that without exception is in violation of the law. I wonder how many shop owners are willing to roll the dice and be prepared to lose their business, home and other assets, as well as face the potential for very real time behind bars.

 

[SparticleBrane]

Current LP and Mid pressure (3442) tanks are made precisely the same way, using the exact same materials (sort of like a Lexus's and Toyota being made on the same assembly line using the same engine).

Note that the LP and 3442 series cylinders have different types of steel, and have different requirements for tensile strength. The difference isn't huge but it is there.

Then again, LP cylinders are regularly pumped to 3600psi or more in some parts of the country, and there certainly isn't an epidemic of cylinders exploding left and right.

 

[awills101]

ill probably just ask my shop to fill it to 3000psi so i can keep up with my dive buddies (they dive hp 120's)

and are there any advantages at all to buying a valve rated for a lower pressure? (i wouldnt think so but it doesnt hurt to ask) or should i just buy one rated to 3442?

 

[Scared Silly]

Originally Posted by Indian Scuba Website
from an engineering point of view there is no significant circulation of gas within the cylinder during the filling process!\

I am kinda surprised to read this as there is quite a bit of circulation that goes on when a cylinder is filled. Which is why one can partial pressure mix and take an immediate reading that is accurate.