The perils of owning LP tanks in the Midwest

[boulderjohn]

Not just a question for John, but everybody: Educate me here as to how tanks are rated. If a tank is LP vs. HP, is there not some inherent difference in the tank? Thicker walls, different threads, something like that? Why would you buy an LP tank and then outfit it with burst discs well beyond what it is supposed to use? Is it just to cheat the amount of gas that you are able to put in it, even though that might not be the safest idea?

@kmarks , this too has been discussed a lot, but if I recall, some posts in those threads by people who seemed to know what they were talking about asserted that there are metallurgical differences.

My understanding, which comes primarily from other threads and should not be considered expert, is that the alloys are different.

Years ago some friends and I were comparing a set of LP doubles with a set of HP doubles from the same manufacturer. They looked nearly (but not quite) exactly identical. The HP tanks had a much higher rated capacity, but if you did the math, you realized that no matter what pressure you filled them to, their contents would be the same--if you overfilled the LP tanks to 3,000 PSI and underfilled the HP tanks to 3,000 PSI, they had the same volume of gas in them. Subsequent research led us to believe that the difference was the alloy used in each.

 

[StefinSB]

Even worse when you get them back “under filled” and, after questioning why that is, were told that the + stamp was hard to see .....

 

[boulderjohn]

Even worse when you get them back “under filled” and, after questioning why that is, were told that the + stamp was hard to see .....

Here are some experiences with filling LP tanks in South Florida. It should show the randomness of the experience.

1. I used to use a now-closed shop called Fill Express. On their website, they had a resource page with various articles. One of the them explained why you should never, ever fill any tank of any kind past its rated pressure, even only a couple hundred PSI with the goal of having it cool to the rated pressure. In actual practice, that shop routinely filled all LP tanks to cool to 3,000.

2. After that shop closed, I used a dive shop that also had a boat, so it was very convenient to have the tanks filled right where the boat left for the dives. One day I picked up my tanks, and they were filled to a little over 2300 PSI. I asked about it, and the guy who filled it (new staff) said they were only rated to 2400. I pointed to the + sign, and he had no idea what that meant. I explained it, and after management confirmed it, he topped it off to 2600 (not 2640--he wouldn't go that far). One day the manager filled my tanks, and they were filled to 2500. When I asked about it, he said it was just too dangerous to fill LP tanks past the rated pressure, and he could not risk employee lives. I said, "OK, how about filling them TO the rate pressure?" He said I was just splitting hairs. That same shop had a policy of filling AL 80s to a cooled pressure of 3300 PSI in order to make customers happy, so when I did recreational dives with my friends who rented AL 80s, they had more gas in their AL 80s than I had in my LP 85s. Apparently they did not see any danger in overfilling AL tanks, just LP steel.

3. That same shop had another employee who was a cave diver. If he filled my LP tanks, it was an entirely different story.

4. On the day that the shop manager said I was splitting hairs in complaining about fills to 2500 in a tank with a rated capacity of 2640, I decided I would check out my options. I found another shop that said it routinely filled LP tanks to 3,000, so I went there for fills, even though it was a lot less convenient. When I would check the tanks after the fills, I don't believe I ever saw a total as low as 3,000. They were once filled to 3,800. (I never asked for overfills; that was their decision.)

SUMMARY: You have to check around. The difference between two shops a stone's throw from each other can be enormous.

 

[Lorenzoid]

American Code of Federal regulations

49CFR 173.301

Paraphrasing, but pressures at 70f may not exceed the service pressure. Pressures at 131f may not exceed 120% of the service pressure.

I.e. if the AL80 is at 131f when filling, it can legally be filled to 3750psi, but when it cools to 70f, it must be at service pressure.

Again, I know there are threads where this has been thoroughly hashed over, but doesn't 49CFR 173.301 relate to the transport of cylinders? Does the Dept. of Transportation (DOT) consider what happens in the back of a dive shop to be within its jurisdiction? Do they inspect dive shops?

 

[tbone1004]

Again, I know there are threads where this has been thoroughly hashed over, but doesn't 49CFR 173.301 relate to the transport of cylinders? Does the Dept. of Transportation (DOT) consider what happens in the back of a dive shop to be within its jurisdiction? Do they inspect dive shops?

Do they inspect shops? I've never heard of it. The dive shop is however filling cylinders commercially and if they abide by the law regarding burst discs, hydro testing, etc. why would someone balk when they decided to follow all of the laws instead of picking and choosing which ones are convenient?

Also note, it is technically illegal for an instructor to transport rented cylinders for students, or for dive shops to transport rented cylinders for customers. Thankfully no one really cares or enforces it, but it technically puts those cylinders being transported into "Commerce" where you need a hazmat endorsed CDL to transport them...

 

[formernuke]

I got rid of all my HP80s. I’m down to 85s and 50s. My usual place for AIR fills is closed while they’re on a trip to MX. I’m diving New Year’s, wanted fills before the holidays, and banked 32% (which I prefer to dive), plus slight overfills on my 85s. You’d have thought I was asking for someone to rob a bank when I asked about overfills! I wanted 3200 at the most.

I ended up at the shop @KathyV had previously recommended to me. They’ll overfill to 3000. I can deal with that. I drove the 40 minutes to drop tanks off tonight and I’ll pick up Saturday. I’ll have a proper, not hot, fill that way.

One shop I’d emailed told me overfills were illegal, immoral, and they weren’t risking their shop and employees for a $15 fill. Drama queen! They’re off my list for good. Location wasn’t very convenient, anyway.

Another shop won’t overfill, but they didn’t throw a tantrum when I had asked when in for something else a few weeks back.

And as a big plus, I found out the shop I went to has helium! I had thought there were only two shops in my area that offered it.

@Marie13 I'll fix that title for you, the perils of owning LP tanks literally anywhere except cave country.

In defense of that shop, they are illegal, so I can't really fault them on that...

Also, welcome to why so many of us have our own fill stations

NO shop here will fill more than a couple hundred above rated and is only to let the tank drift down if there is a long line, but hey my doubles lp 50's still hold the 100 cu I'm used to with my single 100's and trim better.

 

[Lorenzoid]

Do they inspect shops? I've never heard of it. The dive shop is however filling cylinders commercially and if they abide by the law regarding burst discs, hydro testing, etc. why would someone balk when they decided to follow all of the laws instead of picking and choosing which ones are convenient?

A regulation (like the CFRs as potentially applied to dive shops) that no authority believes they have jurisdiction and/or the ability to enforce is, well, unenforceable. Basically what I'd call null. If there's no direct liability for violating it, does it really exist as a practical matter? There is plenty on the books that looks on its face like someone could violate it, but it's simply not enforced for one reason or another. This is different than someone weighing the odds of getting caught before violating a law. In the case of a dive shop, there is nobody even interested in catching you. You've seen humorous lists of virtually unenforced laws like this, right? The Weirdest Law in Every State So I'm not really sure I buy the "it's illegal" argument. I'm more persuaded by "it's best practice in the industry for safety reasons not to overfill." They might also want to avoid overfilling to avoid potential liability to someone injured as a result (and a lawyer could attempt to use a violation of the CFRs as evidence of best practice). But "it's illegal"--as in, government authorities care about this--seems a stretch.

Also note, it is technically illegal for an instructor to transport rented cylinders for students, or for dive shops to transport rented cylinders for customers. Thankfully no one really cares or enforces it, but it technically puts those cylinders being transported into "Commerce" where you need a hazmat endorsed CDL to transport them...

I recall reading that in some prior thread. There are all kinds of situations that were never really contemplated--or were intentionally swept under the rug lest they open a can of worms--when laws and regulations were enacted.

 

[boulderjohn]

I recall reading that in some prior thread. There are all kinds of situations that were never really contemplated--or were intentionally swept under the rug lest they open a can of worms--when laws and regulations were enacted.

It might be interesting to write a book about all the rules and regulations that are regularly violated across the scuba industry. I don't think anyone wants to write that book though, because they are afraid someone in authority might get ahold if it and decide to start enforcing things. The Department of Justice would probably create a new division to deal with the way employees are paid by dive shop owners in America if they knew what was typically happening.

 

[tbone1004]

@Lorenzoid against the law is still against the law. Hydro's aren't checked or enforced by anyone either, however the liability you incur if something happens and the bottle was out of hydro is not worth the risk. You can't fault the dive shops for following all of the rules

 

[Lorenzoid]

@Lorenzoid against the law is still against the law.

I won't belabor trying to make my point, but you're not following what I'm saying. Okay, one more try. "Against the law" doesn't have a legal meaning in itself. Laws that no one has any intention of enforcing (or that can't be enforced as a practical matter) can be enacted, but they have no practical effect. If DOT officials give you a mystified look when you ask about dive shops, does the regulation really apply to dive shops? I think of the saying about "If a tree falls in a forest ...." I really have no knowledge of how the DOT views dive shops--this is just me spouting off on a hypothetical--but IF it's true they don't care or have never given it any thought, then I think the regulation as it might apply to dive shops is null.

Hydro's aren't checked or enforced by anyone either, however the liability you incur if something happens and the bottle was out of hydro is not worth the risk. You can't fault the dive shops for following all of the rules

Right. And that was what I was getting at in the second part of my comment: "They might also want to avoid overfilling to avoid potential liability to someone injured as a result (and a lawyer could attempt to use a violation of the CFRs as evidence of best practice)."

But those are two different concepts.