The perils of owning LP tanks in the Midwest

[NAM001]

@KWS my general rule is that per the CFR I am allowed to fill to 120% of capacity if the tank hits 131F. The tanks almost always hit that when filling especially if they are nearly empty and if you do that, then they should cool to roughly service pressure.
2475=>3100
2640=>3300
3000=>3750
3500=>4400

What do I do? It depends, but I think if you're filling at 600psi/min and the tanks are relatively empty, then setting the regulator to 20% over is pretty spot on IME.

I agree with you 100% and I believe that your settings are correct based on the final results of your system, common sense and the CFR's intent. There are many that do not think in that manor. Lots of shops say no more than WP on the gage, period at any time,,, just like they say no filling of tanks greater than 20 yo. It is the wrong application/ solution when things could be done correctly with a minimal of training/ understanding of the process for fill station operators. I think it is only going to get worse in many other areas. I have been playing with using towels on the tanks while filling only a couple, and keeping them wet and it drastically reduces the temp build up based on the final cooling PSI as a measurement metric. Ad a fan to that and it gets even better. I have also been expanding my fill capability to support filling several tanks at once. ( I use H valves on my tanks) so I fill a chain of 4-5 at a time. 90 percent of my tanks are lp steel tanks.

 

[-JD-]

I'm honestly not really following your point. Sorry.

When we dive we bring with us the gas we need to survive underwater. The fundamental question is "do I have the gas I need plus a reserve?" Certainly we select the tank(s) we use based upon buoyancy and volume characteristics but what matters is whether we have the volume of gas we need or not.

Getting worked up about whether I get 3000 psi in my LP85s or 3442 in my HP100s is a fools errand. I dive HP100s primarily. Sometimes I get a solid cool 3600 psi fill and sometimes they cool to 3300-3400. But what matters is do I have the gas to do the dive??? Anything extra is just left in the tank as the base for the next fill, right?

My counterpoint above was an explicitly over-the-top way of saying "Contents are key, but packaging counts too." There would be a lot of very happy people if someone figured out how to stuff 120cuft of air into a pony bottle at the other end of the continuum.

I agree, having sufficient gas to do the dive is the requirement. And a 5% underfill is not the end of the world on an HP100. If someone goofs and and fills it as a LP tank, though, you have a roughly 25% underfill and that can put a stop to some dives or just hammer the "value" of the dive.

If you are consistently getting out of the water with a lot of extra air, then great! Fill details really don't matter much. For the OP, who is newly cave-diving and limited by 1/6ths, every cuft really counts in terms of making the dive worthwhile.

Enough gas, in user-compatible containers is the end requirement.

 

[-JD-]

Around here people get pissed and tailgate, flash lights etc if you aren't going at least 30 mph over the posted speed limit.

Go with the flow or move the "H" over! Left-lane sitters obliviously (all to common) or self-righteously (you do know that "keep-right except to pass" is also the law, right) poking along at or below the limit end up precipitating more danger/bad driving situations.

I grew up in CT in the days where Staties ran GNXs as chase cars and used anything from Chevettes to Corvettes as radar cars. The only ones going 30+ over - the Staties - when it was shift change.

 

[Divin'Papaw]

My counterpoint above was an explicitly over-the-top way of saying "Contents are key, but packaging counts too." There would be a lot of very happy people if someone figured out how to stuff 120cuft of air into a pony bottle at the other end of the continuum.

I agree, having sufficient gas to do the dive is the requirement. And a 5% underfill is not the end of the world on an HP100. If someone goofs and and fills it as a LP tank, though, you have a roughly 25% underfill and that can put a stop to some dives or just hammer the "value" of the dive.

If you are consistently getting out of the water with a lot of extra air, then great! Fill details really don't matter much. For the OP, who is newly cave-diving and limited by 1/6ths, every cuft really counts in terms of making the dive worthwhile.

Enough gas, in user-compatible containers is the end requirement.

For sure! But then that really wasn’t what I was arguing.

 

[Marie13]

Update of sorts:

Took a new job that's 40 minutes from home. As soon as I got the job, I used Google Maps to see where the dive shops were in relation to new office. At new job, I'll be 5 minutes from a shop that banks 32%, but won't overfill (they were the ones who simply said they didn't overfill, but without the drama of another shop). $12/tank for my 85s.

Shop that fills to 3000 and has banked 32% is nearly an hour from the new office. Shop that only has air and fills to cool to 3600-3800 is 45 minutes from new office.

I've decided I'm going to primarily go with the shop 5 minutes from the new office. Drop tanks off at lunch and pick up after work. Maybe once they get to know me some, they will overfill a bit. I'd be happy with 3000. Fills to 2640 will work for my quarry diving. If I've got big dives, I'll drive the hour to the shop that fills to 3000.

 

[1bubbleoff]

I'd question WHY you insist on violating Federal law in regards to CFR's, ignore manufacturers engineering specifications
are not only asking, but willing to endanger a fill operators life with your request to overfill a pressure vessel, completely exposing a dive shop, it's employee's, ownership, and customers to potential catastrophic consequences, legally, morally, medically, and ethically....

It's really simple....if you have to cave fill to have an acceptable amount of gas for a specific dive, you have an equipment problem. Get larger tanks, or carry more tanks at rated pressure and volume. If you have a physical issue that precludes you from utilizing the proper equipment to meet the demands of the planned dive...maybe...you shouldn't be doing that dive.

At the end of the day, there are rules...and usually for good reason. The willingness to gloss over, make excuses for, or just plain ignore them...is what starts the accident chain.... that and a healthy dose of hubris will eventually bite you...

 

[rjack321]

I'd question WHY you insist on violating Federal law in regards to CFR's, ignore manufacturers engineering specifications
are not only asking, but willing to endanger a fill operators life with your request to overfill a pressure vessel, completely exposing a dive shop, it's employee's, ownership, and customers to potential catastrophic consequences, legally, morally, medically, and ethically....

It's really simple....if you have to cave fill to have an acceptable amount of gas for a specific dive, you have an equipment problem. Get larger tanks, or carry more tanks at rated pressure and volume. If you have a physical issue that precludes you from utilizing the proper equipment to meet the demands of the planned dive...maybe...you shouldn't be doing that dive.

At the end of the day, there are rules...and usually for good reason. The willingness to gloss over, make excuses for, or just plain ignore them...is what starts the accident chain.... that and a healthy dose of hubris will eventually bite you...

Hey scuba policeman, are you gonna call the FBI about the non-DOT carbon fiber tanks I have? How much I fill them to and what I use them for?

 

[MrVegas]

There would be a lot of very happy people if someone figured out how to stuff 120cuft of air into a pony bottle

I always wondered why my SPG goes to 5000. (Just kidding, of course.)

 

[rjack321]

I always wondered why my SPG goes to 5000. (Just kidding, of course.)

300 bar = 4351 psi
OMG we're all gonna diieeeeee

 

[DiveClimbRide]

I've got one that goes to 400 bar (~5800psi). Now I just need some 300bar tanks to overfill