The perils of owning LP tanks in the Midwest

[tbone1004]

Mine all have 5,250psi burst discs. Ask @boulderjohn about his burst disc experience.

Mine have 5250 burst disks as well. The shop tonight checked when I dropped my tanks off.

burst discs are rated either at working pressure or test pressure. Either way it is 90% of test pressure. 3000psi AL tanks are tested at 5000psi, HP steels at 5250, so they blow at basically the same pressure

 

[boulderjohn]

Mine all have 5,250psi burst discs. Ask @boulderjohn about his burst disc experience.

OK, I am going to guess that the following is what is being referenced here.

My LP108 doubles had burst discs intended to handle cave fills. I was using them, though, in a dive shop in south Florida where most (but not all) of the employees were afraid to fill LP tanks to the rate pressure, let alone over it. That was fine with me. The deco dives we were doing did not require overfilled 108s, so I took what they gave me.

One day I picked up my tanks in preparation for the dive, and the employee who filled them told me that he had detected a small leak in one of the burst discs and had fixed it. I thanked him, figuring he had put a wrench to it and tightened it.

On my way home to Colorado, I stopped off in Marianna, Florida, for some cave diving. I dropped my tanks off at Cave Adventurers for fills and headed out to do some other work. I came back quite a few hours later to see that the shop was a real mess. Something massive had happened. When I asked what had gone on, people asked, "You mean you don't know?!?!?!" No, I didn't know. It turned out that the helpful South Florida employee had fixed my burst disc by replacing it with a standard disc for an LP tank, which did not work out very well for a cave fill at Marianna. I wasn't there, so I still have never seen a blown burst disc, but I can describe the aftermath.

 

[KathyV]

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'm glad that they were able to help you! They been our dive shop for years and they have always treated us well.

We are warm-water recreational divers but I know that the shop and the owner do a lot of work with advanced and technical divers so I am not surprised that they were able to meet your needs. Have fun diving!

 

[JahJahwarrior]

I'm always very hesitant to document illegal activities in writing.

If I were a dive shop, my official position would be no overfills. If you email me asking about it, the answer would be no overfills.

If you show up in person with a burst disk that is rated high enough to let me fill to 3900psi without blowing,
Well, I won't put in writing what I would do, but I hope you can infer.

I'm sure the blue steel guy was a salesman, not an engineer, and I'm sure their lawyers tell them how to respond to questions like "am I allowed to break the law?" with an answer like "no."

Having LP tanks in south florida is a pain in the butt. Getting fills down here at all is a pain. They don't know my name, they want to look all around the tank for hydro, they want me to write down the serial number and document the o2 in a book before leaving the store. They don't fill in 10 minutes. They ask me for certifications. They don't think to look on the bottom of a stage bottle for a vip sticker. But in their defense, a lot of idiots buy ancient 6351 cylinders on craigslist and come in asking for a fill without a certification...

 

[Lorenzoid]

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

I apologize for asking something that I know has been discussed many times, but exactly what law is being referring to?

 

[kmarks]

My LP108 doubles had burst discs intended to handle cave fills. I was using them, though, in a dive shop in south Florida where most (but not all) of the employees were afraid to fill LP tanks to the rate pressure, let alone over it. That was fine with me. The deco dives we were doing did not require overfilled 108s, so I took what they gave me.

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?

 

[Lorenzoid]

@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.

 

[Marie13]

I'm always very hesitant to document illegal activities in writing.

If I were a dive shop, my official position would be no overfills. If you email me asking about it, the answer would be no overfills.

If you show up in person with a burst disk that is rated high enough to let me fill to 3900psi without blowing,
Well, I won't put in writing what I would do, but I hope you can infer.

I'm sure the blue steel guy was a salesman, not an engineer, and I'm sure their lawyers tell them how to respond to questions like "am I allowed to break the law?" with an answer like "no."

Having LP tanks in south florida is a pain in the butt. Getting fills down here at all is a pain. They don't know my name, they want to look all around the tank for hydro, they want me to write down the serial number and document the o2 in a book before leaving the store. They don't fill in 10 minutes. They ask me for certifications. They don't think to look on the bottom of a stage bottle for a vip sticker. But in their defense, a lot of idiots buy ancient 6351 cylinders on craigslist and come in asking for a fill without a certification...

The shop could have simply said “We don’t do overfills” and left it at that. No need for the additional drama queen crap.

 

[boulderjohn]

I'm always very hesitant to document illegal activities in writing.

If I were a dive shop, my official position would be no overfills. If you email me asking about it, the answer would be no overfills.

I am sure JahJahwarrior is using the term "illegal" very loosely to include a wide variety of issues that could lead to the sort of trouble he describes, and I fully concur. In this post I would like to extend that policy both as a warning to other posters and as advice on reading social media posts written by seasoned scuba experts in general.

When I was getting my DM training, the other candidates and I were in the pool area of the dive shop when a shop customer asked some questions of the Course Director who was teaching our class. After the initial question, she asked him a question about a medical issue she was having, and one of the other DM candidates immediately chimed in with an opinion. The course director cut him off, and after the customer left, he said to us, "The doctor is never in! We are not doctors, and we don't give medical advice!" The message is that you don't offer direct statements on anything that can come back to haunt you if a person following your advice has a problem. That would be especially true if the advice you are offering is outside of the law or any other standard procedure.

On ScubaBoard, if you go to the diving medicine section, you may sometimes see occasions where I have offered opinions. Note how carefully those opinions are written, and note that if there is any questionable issue whatsoever, my opinion will usually be to get expert help. Note that the doctors and other medical experts, like Duke Dive Medicine, will only give standard statements related to the case, the kinds of information you would find if you went to WebMD, and will avoid diagnosing the individual case. They will often make a point of that.

That policy extends to all scuba-related areas that are controversial. Let's say that on a ScubaBoard thread you said there was no problem doing something that is outside mainstream practice, and someone following your advice has an accident. You could be in real trouble if someone decided to find out why that person made that decision and decided it was your fault.

Yes, I have admitted that I have had my LP tanks overfilled, but I only do so in the context of that practice being generally accepted in a portion of the diving community. I have never suggested in writing to anyone that they do it. That is a decision for them to make without my personal advice. I HOPE I am protected by the fact that it is a common practice in certain areas, but I could be wrong.

 

[tbone1004]

I apologize for asking something that I know has been discussed many times, but exactly what law is being referring to?

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.