tank size and pressure

[NAM001]

I'm amazed that people will recommend overfilling LP steels to recreational divers who are asking general questions about cylinders.

There are so many reasons why it's a bad thing to recommend.

1. As a practical matter, overfills are simply not available to most recreational divers. Dive shops outside cave country don't offer them.
   
2. HP steels have been in production since 1987 and are readily available new or used. People who want HP fills can get HP cylinders.
   
3. Burst disc failures can cause injury or property damage. Many if not most divers getting "cave fills" use an over-spec burst disc or blanking plug. Rec divers who don't realize that a burst disc change is part of the package are at greater risk from a failure. I believe @CuzzA had this happen. On the other hand, over-specing or blanking out a burst disc poses its own risks.
   
4. While there are not believed to have been any cylinder ruptures caused by cave fills, that doesn't mean the practice is safe enough for general recreational diving. a) There simply haven't been enough cave fills performed to draw a conclusion, especially to the higher pressures now considered acceptable. b) The field experience with cave fills is limited to those cylinders typically used for cave diving and should not be generalized to other types of LP steels, especially older, smaller cylinders such as LP72s and some LP50/LP52s.
   
5. While the jurisdictional questions are complex and enforcement spotty, it is unlawful under some circumstances.

You raise good points and you are right . One should not recommend overfilling tanks to rec divers. I do my best not to do that but also try to say that iff it happens the world will not end, using cave fills as an example. those that do cave fills know very well yo dont take a tank off the shelf and do it. there are eternal arguments regarding conercial and private actions. such as hydro is not a requirement to fill a tank. It would be if done in a comercial setting.

I would argue with the point that not enough tanks have been overfilled to make any determination on its safety. Again if you define safety on the tank stamp or the resultant outcomes. Hundreds of tanks are filled daily in cave country, and often well over 3500 normally 4000. 104's 108's are filled a lot to 4k. my 85's were filled to 4k several times in cave country even with trimix gasses as doubles. Personally the number 4000+ is mentally disturbing. but so is 61 ft for an OW diver who has been told their max depth allowed is 60 ft.

 

[NAM001]

So marketing jargon and half-accurate math is how we get to the numbers we're at....and, unfortunately, none of it is clear. However, OMS sells the Faber LP108 as an LP112. I believe that's because they use "technical atmospheres" of 14.2psi instead of 14.7psi (half-accurate math, again).

Typical understandings in cave country are that LP tanks are rated at their volumes at 2640psi. So an LP108 is 108ft3 at 2640psi. Discounting van der Waal forces, that would give you 147ft3 at 3600psi. Unfortunately, it's likely to be closer to 135ft3 (depending on what constants you believe and how you do your math) as there is a fall off from linearity as pressures increase.

they also sell a lp121 that is i think 125. i have at least 2 of them

 

[tbone1004]

So? This is the first time I haven't been able to find a thread that answers a question I have. I don't post because I don't have the experience to educate anyone or change misconceptions. I think you were one of the original replies that helped, so I do thank you for that. But what's this supposed to do?

and that's perfectly fine. I was going more for the fact that the forum doesn't always behave like this and hoping that you don't give up on participating or at least browsing the forum because this thread got a little sideways.

No opinions are unimportant though and while you don't feel like you can educate or change misconceptions, having your opinion and experiences out there are always good for others to read. Reading people like me yacking on every day can get a little boring, but on a lot of threads, bringing them back may be useful as things change and participants come in with different discussions. Very few threads these days are "novel" in terms of topic, but most of them have new and interesting information being brought up and having lively discussion is always a good thing

 

[MrBlenny]

And FWIW, as someone generally interested in all things scuba, I found this thread rather interesting Sometimes information gleaned via aggregation is more valuable than a singular statement of fact (at least for me.)

 

[MMM]

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A ScubaBoard Staff Message...

This thread, which had been closed for moderation after a few reports, is being re-opened. Many off-topic posts (and those quoting them) have been deleted. Please try and keep in mind what the OP is asking for and answer that question...not go off on your favourite hobby-horse, as distantly related as you may think it is. At best, that is dragging a thread off-topic; at worst, it is being a Point-of-View-Warrior. Thanks. Marg, SB Senior Moderator

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[W W Meixner]

and that's perfectly fine. I was going more for the fact that the forum doesn't always behave like this and hoping that you don't give up on participating or at least browsing the forum because this thread got a little sideways.

No opinions are unimportant though and while you don't feel like you can educate or change misconceptions, having your opinion and experiences out there are always good for others to read. Reading people like me yacking on every day can get a little boring, but on a lot of threads, bringing them back may be useful as things change and participants come in with different discussions. Very few threads these days are "novel" in terms of topic, but most of them have new and interesting information being brought up and having lively discussion is always a good thing

tbone...

I had nine posts deleted from this forum in defence of doing what's right...

The forum should have been modded the minute the cave divers chimed in...with the topic I dare not mention...or I'll have ten posts deleted...

''The Legends'' never pay attention to the OP's post...the Chairman needs to open a forum catagory specifically for the me...me...me tribe...he could call it...'''Where Gorillas Go to Bang on Their Chests''...or...''How I Do Everything Wrong''...

We're all eating grass in someone elses pasture...so chew nice...

Best...

Warren

 

[W W Meixner]

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A ScubaBoard Staff Message...

This thread, which had been closed for moderation after a few reports, is being re-opened. Many off-topic posts (and those quoting them) have been deleted. Please try and keep in mind what the OP is asking for and answer that question...not go off on your favourite hobby-horse, as distantly related as you may think it is. At best, that is dragging a thread off-topic; at worst, it is being a Point-of-View-Warrior. Thanks. Marg, SB Senior Moderator

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Hey Marg...

You will note...the poster/dragon...is eating the moderator...not the other way around...

W...