Consensus on Overfilling Tanks?

[W W Meixner]

@W W Meixner try telling that to fill stations who are trying to make money. That is not a practical way to fill as it doubles the labor cost associated with filling. I have not seen that as SoP for any filling station, regardless of commercial gas cylinders, SCBA cylinders, or scuba tanks. The only exception to that I have ever seen is when PP filling custom trimix blends.

T...

What's right...and what's done...doesn't make what's done...right...

My shop practice was to do it right...and in seven years...no one complained...and we filled lots of cylinders...

And why start arguing bad practice...after all the arguing...bad practice...is still bad practice...

W...

 

[rob.mwpropane]

If you need more gas......
Why can't you just buy bigger tanks ??

Because I've bought enough dive stuff that I should be happy and dive with what I have for the time being, or at least try. I got the ds, the tanks, and the place to dive. The only plans that I might proceed with are setting up my 2 100's as doubles, and really that's just so I don't have to keep changing tanks and for redundancy.

But trust me, I've thought about it

 

[James79]

My 2 psi.... Aluminum and Steel are 2 extraordinarily different metals (in terms of how they handle stress). If you have the luxury of a shop that will fill to what you ask, do your own research and make an educated decision on where your risk tolerance lies. I will not over fill an aluminum, full stop. I own old school 72s (2250 working pressure), and prefer to run them at 2800 to 3000. Some run them higher than that. When I made my decisions, I looked up how hydro works, and what it's testing for, along with how the two types of metal react to stress.
My closest shop will only fill them to 2250 (making them effectively 65 CF tanks) due to liability/risk aversion. Their shop, their rules, and I respect that. I have another option a little further, that depends on who is running the fill station... some stop it at 2500, one I had to stop at 3200.
Best of luck
James

 

[grf88]

T...

What's right...and what's done...doesn't make what's done...right...

My shop practice was to do it right...and in seven years...no one complained...and we filled lots of cylinders...

And why start arguing bad practice...after all the arguing...bad practice...is still bad practice...

W...

Filling a tank to a pressure such that when it cools it is at the rated pressure is not bad practice, it is just not your practice.

 

[rob.mwpropane]

Excuse my ignorance, but is there chart somewhere (or maybe a calculation) for what tank pressures can be at certain temps? It would be nice to carry around something that I can show a shop. If they say no, at least I can say I tried and had fundamental science to back it up.

 

[tbone1004]

T...

What's right...and what's done...doesn't make what's done...right...

My shop practice was to do it right...and in seven years...no one complained...and we filled lots of cylinders...

And why start arguing bad practice...after all the arguing...bad practice...is still bad practice...

W...

You claimed that it is standard industry practice to fill to pressure, let it cool, then top off. Please show me in writing somewhere where that is a standard industry practice because otherwise your definition of "right" and "bad practice" are just your opinion and while I don't think hammering hydro pressure into a tank is really good for it, at the same time I do know that that is exactly how they are hydro'd, and fairly rapid flil to working pressure is how the industrial fill stations fill, as well as the SCBA bottles used in fire departments, and also how every military and government fill station I have seen operates.

 

[grf88]

I guess you could make one up using Charles's Law.

 

[tbone1004]

Excuse my ignorance, but is there chart somewhere (or maybe a calculation) for what tank pressures can be at certain temps? It would be nice to carry around something that I can show a shop. If they say no, at least I can say I tried and had fundamental science to back it up.

I think the rule of thumb is about 5psi per degree Fahrenheit.

 

[W W Meixner]

You claimed that it is standard industry practice to fill to pressure, let it cool, then top off. Please show me in writing somewhere where that is a standard industry practice because otherwise your definition of "right" and "bad practice" are just your opinion and while I don't think hammering hydro pressure into a tank is really good for it, at the same time I do know that that is exactly how they are hydro'd, and fairly rapid flil to working pressure is how the industrial fill stations fill, as well as the SCBA bottles used in fire departments, and also how every military and government fill station I have seen operates.

I've always believed that any good discussion enjoys a good argument...

Your argument is to argue a white dog black and then argue it white again...

Assuming you've taken a cylinder servicing course...what part of ''never over-pressurize a cylinder'' are you having a hard time understanding...if you still have you're course outlines...maybe you need to refresh your memory...

Proceed as you see fit...you don't need me...argue as much as you like...

I had assumed you were better than this...

W...

 

[kelemvor]

You know what I think is crazy? There are tank fill safety boxes that protect everything in the area if there's a rupture during fill. We had one at the local aquarium's fill station and beyond taking a little time/space to hook up it wasn't hard to use. If some shops are so freaked about fill safety and spending inordinate amounts of time filling slowly then why the heck don't they have a safety box? It always makes me scratch my head when I think about it. Sure the boxes aren't free but if you've gone to the expense of setting up a shop fill station then it's a drop in the financial bucket and takes very little space.

This russian model is quite a bit larger and more elaborate than the one at the local aquarium. They're a production item for some manufacturers (i.e. not custom made)...

Edit: this looks very similar to what I've used. $4359.00 new.

Stationary Containment Fill Stations

Here's one that recently sold for $700 used 1 Containment Fill Station for filling SCBA Bottles. - govdeals.com