To what pressure are you filling your PST 104s to?

[Scubaroo]

A bit off thread... but I found this gem of a quote while reading an Australian dive site, regarding the "true" bursting pressure of some aluminum tanks that had failed hydros....

at the test station, we had some ali cylinders that had been failed due to folds / cracks in the neck etc... so when bored, decided to "pump up" a few... they split down the sides, none at LESS than 500 bar... tried 6 cylinders... one made it to 650...

500 bar is about 7250psi...
650 bar is about 9400psi...

:boom:

 

[ninja]

Originally posted by maddiver
Well.........................PSTs are pretty good.

But I would be hesitant to suggest there is no reason to dive with anything but steel. How about ow with wesuit? What about stages? Both of those applications the correct tool for the job is alum tanks.

PST are perfect doubles for fl caves with drysuit but they are not practical in other areas (such as the Yucatan) where you can dive forever on double 80s with a wetsuit and also avoid the potential for overtaxing the entry and exit ladders (that already look shakey).

They are pretty bulletproof as far as hydros and overfills are concerned.

Well I guess their is no diving anywhere else in the world!! The Great lakes you will use a dry suit and even with your stage bottles you need the extra ballast ! Fabers suck for this and aluminum are not even an option! Bring on the 104's the heavier the better!

Len

 

[Rick Murchison]

Originally posted by maddiver
Bob-

While it is physically possible to dive steels with a 3mm wetsuit in ow (and it at first glance has many compelling reasons) the real issue I have with it (and I dm'ed on west coast of FL for years) is that you have no redundant buoyancy device (ie drysuit) and essentially no ditichable weight.

Au contraire, my young friend... there are many ways to assure redundancy in lift - the easiest is to carry a lift bag. No sweat.
Rick

 

[Lost Yooper]

I fill mine to 3300-3500psi routinely (both PST and Fabers).

Mike

 

[Uncle Pug]

Hey Yooper Duper...
Glad you're still alive and kickin' !!!
Long time no post

 

[maddiver]

Ok rick- I'm not going to bite....real hard on this one until I understand where you are going?

Do you mean that you would dive in deep ow with say a 3mm suit and double pst 104's and taking your lift bag and consider this adequate and 'optimal' configuration (in terms of buoyancy needs)?

Feel free to make that 3mm a 6.5mm or whatever for discussion sake. I am real interested in how your lift bag could be of great use **immediately** like within 5 secs if your wing came apart in really deep ow. Would a drysuit with this tank configuration not be more appropriate? I'm not saying that you haven't been doing it like this for years and getting away with it, or that you have to stop if you have been...merely looking for the logical support. Why not go to alum 80s for ow if you choose the wetsuit? If you choose a drysuit then by all means go with the steels (doubles only not stage steel).

I really doubt you could swim up (more like just maintaining your depth) a set of 104s with a 3mm wetsuit and deploy a lift bag without major co2 retention and heavy exertion/sac increase but if you have actually tried this to prove to yourself you can do it (ie no gas in your wing at 100' +) I would love to hear about it. Certainly I defer to your experience on this one as I have never worn 104s and wetsuit in ow or tried the method which you suggest.


Please explain to us in detail the use of a lift bag (and whether it is closed or open celled) and why it is appropriate as your primary source of back up buoyancy. Where to store it? How to deploy it in an emergency etc...

Originally posted by Rick Murchison

Au contraire, my young friend... there are many ways to assure redundancy in lift - the easiest is to carry a lift bag. No sweat.
Rick

 

[caverkevin]

I remember the days before I knew any better. Diving 104's with wetsuits. Open ocean, 130 feet, 5mm and double 104's. I had a dive-rite super wing, no problems, so I felt safe. Then diving caves with a with a two piece 7mm, I lost both cells on that super wing. Lucky I was able to crawl back to the surface. Key word 'crawl' not 'swim'!!!

I would be REALLY careful if your last ditch plan is to ride to surface on a lift bag. Most everyone I have ever heard of using this method get to take another ride, a chamber ride.

Don't take me wrong, 104's are great tanks. I use mine a bunch. But take a look at the context here. Do you really need excess of 200 ft^3 of gas for a 100 foot dive. This would be something to evaluate!!!

KLJ

 

[maddiver]

Kevin-

As always, thanks for a logical and well experienced answer that clearly spells out the issues associated with this thread. On a side note, I did see this guy carrying a lift bag in a cave on my last Yucatan trip. He was going to use it to 'back up his bc' in there.

Originally posted by caverkevin
I remember the days before I knew any better. Diving 104's with wetsuits. Open ocean, 130 feet, 5mm and double 104's.......Then diving caves with a with a two piece 7mm, I lost both cells on that super wing. Lucky I was able to crawl back to the surface.
KLJ

 

[caverkevin]

On a side note, I did see this guy carrying a lift bag in a cave on my last Yucatan trip. He was going to use it to 'back up his bc' in there.

This made me think of the lady in the TV ad "help! I've fallen and I can't get up". Instead this time, "Help! I've over-inflated my lift bag and I am stuck to the ceiling".

You have to be kidding me on this one. A lift bag for a bail-out plan in the caves. Yucatan no less. Next you are going to tell me he was wearing double 104's, steel stage bottles and a 3mm shorty.

This is some crazy stuff, using lift bags for back-up bc's. I wonder where this idea started. I can't think of any training manuals I have ever seen it printed in. Sounds to me like something a dive instuctor that does no real diving, would tell another diver that does not know any better.

KLJ

 

[maddiver]

Nope- this guy had double alum 80s and a SS backplate with the pocket thingy (kind of weird to see with a lift bag pooched up in it getting ready to go in the cave). Full Suit- I guess to be atleast a 5mm. No stage, no deco bottle. I don't know if those Halcyon Closed cell bags come with Speleothem induced damage warranties?

Had I remembered the camera......

Originally posted by caverkevin

This made me think of the lady in the TV ad "help! I've fallen and I can't get up". Instead this time, "Help! I've over-inflated my lift bag and I am stuck to the ceiling".

You have to be kidding me on this one. A lift bag for a bail-out plan in the caves. Yucatan no less. Next you are going to tell me he was wearing double 104's, steel stage bottles and a 3mm shorty.

KLJ