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Post by technidiver on Jul 3, 2019 11:10:02 GMT -8
So I've been doing some reading on LP tanks (especially the 72) and I've come to the consensus tha it's ok to fill it to 3000+. North Florida Cave divers routinely fill lp steel tanks to 3000+ and have had no problems.
As for using yoke on that pressure, again if done properly, no problem.
Sheck Exley used 4000+ on his 800 footers and Cousteau used 300 bar tanks in the hydrodynamic pack. Both used yokes.
The perfect DH for the higher pressures is likely the Spiro Mistral. Plenty of proof of it being used on higher pressures. The yoke is sturdy too. Perhaps it's possible to throw on a heavy yoke as well.
Let me know what you guys think. I've been filling my 72s to 2800, but that's hot so it goes down to the 10% overfill level of 2500.
TD
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Post by SeaRat on Jul 3, 2019 11:57:52 GMT -8
I would be Leary of using a LP cylinder designed for 2475 beyond that (that's the "+" rating, and gives the cylinder a full 71.2 cubic feet of air). I know about the Florida cave divers, and their reasoning was that shortening the life of the cylinder was less risky than running out of air in a cave, which is actually reasonable. But as a common practice, I don't think it would be good. Luis might have more engineering information than do I.
Now, about the yolk. The regular Aquamaster yolk was used by the U.S. Navy at 3000 psig. The photos I showed on the old aluminum 90 Navy tanks clearly show the older style yolk. But at the U.S. Naval School for Underwater Swimmers, these tanks were filled to only just above 2000 psig too.
Now, about the LaSpiro Mistral used at 3000 psig; yes, they apparently were used at that pressure. BUT, they will breath much harder than at the lower pressure. The USD Mistral was not designed for 3000 psig, and that pressure could cause seat damage.
A better alternative would be any of the two-stage regulators for 3000 psig. I know that the Royal Aquamaster was designed for 3000 psig (my brother's RAM is on a 3000 psig twin 45s right now), as was the AMF Voit Trieste. Later Dacor models, the R-4 would also work well with 3000 psig.
Just some thoughts.
John
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Post by technidiver on Jul 3, 2019 16:48:22 GMT -8
The tanks maximum pressure is 3750 PSI, 5/3rds its working pressure. I read that none of the 72s have had shortened life spans, none have exploded, and no one has seen one do anything crazy under these higher pressures. I do understand about Mistral no being so good for higher pressures. Would it be possible to swap a spiro seat into a USD? Just an idea, and the spring too! The seat and springs are really the only differently designed parts for the regs.
Now I'm not saying it should be done to 3750. But I won't lose sleep for 3000. My doubles set pressurized to 3000 gives 170cf of air and is a fraction of the size and cost of 80s. However I don't need any weight when I wear them, they're extremely heavy and negative. Better at the end of the dive.
TD
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Post by SeaRat on Jul 3, 2019 16:52:14 GMT -8
The tanks maximum pressure is 3750 PSI, 5/3rds its working pressure. I read that none of the 72s have had shortened life spans, none have exploded, and no one has seen one do anything crazy under these higher pressures. I do understand about Mistral no being so good for higher pressures. Would it be possible to swap a spiro seat into a USD? Just an idea, and the spring too! The seat and springs are really the only differently designed parts for the regs. Now I'm not saying it should be done to 3750. But I won't lose sleep for 3000. My doubles set pressurized to 3000 gives 170cf of air and is a fraction of the size and cost of 80s. However I don't need any weight when I wear them, they're extremely heavy and negative. Better at the end of the dive. TD TD, If you do this, filling the steel 72s to 3000 psig, be sure to change out the overpressure burst disc on the valve/manifold. In the sun, you may have one go if you don't change it to 3000 psig. Having a burst disc go on you will be quite a wake-up call. Also, this can cause injuries/damage. Again, not recommending this fill though. I just bounced this off my LDS owner, and she said that filling these tanks to 3000 psig will fatigue the steel over time. It probably will result in the tank not passing hydro, and also no reputable dive shop will do such an overfill. If you are filling them yourself, you can probably do it, but neither she nor I would want to be around the system when such an overfill was being done. Now, these do happen in dive shops (mistakes do happen), and once or twice probably won't be a problem. But doing it repeatedly will (not might) cause metal fatigue. Why risk it? John
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Post by vance on Jul 3, 2019 17:07:33 GMT -8
I don't like the idea of 3000+ psig on vintage regulators, esp. an unbalanced singlestage regulator. That's a lot of strain on a yoke designed for 2250 psig max, and the breathing effort will be higher than designed for. If your diving style and ability allows for it, more power to you, but keep an eye on the yoke for stress cracks!
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Post by technidiver on Jul 3, 2019 18:26:54 GMT -8
Yes, I'll have to change out the burst discs. I've heard some styles are better than others. Something about the one piece burst discs being prone to popping or malfunction. 1 or two times, no problem. I agree. More than 1-2 times, no problem again as long as it's within the limits. There's limits for a reason. The 3AA marking states that the tank will likely fail at 5/3rds the working pressure. Could go sooner, could go later. As for the yokes, I remember Jay mentioned stress cracks on them. I always check mine for nicks and damage. No cracks yet. It's more of the issue with the O ring, than the actual yoke. The o ring extrusion is the problem, but that is extremely unlikely even with the older yokes. The newer yokes as well as the Conshelf Heavy Yoke work well with higher pressure, they just have to be tightened nicely. There's a reason why the Spiro Mistral has a hex fitting for a wrench to help tighten or untighten it TD Please feel free to add more, I think it's good to keep ideas flowing.
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Post by SeaRat on Jul 3, 2019 21:23:07 GMT -8
TD,
I have a set of twin 45s that I've had since the 1980s. I have not overfilled them, and they are still in almost pristine condition. I dove them last Saturday at Big Eddy in the Clackamas River. They have been in continuous service since I bought them new, and are the only set I have that are that old. Treated well, steel tanks will last almost forever.
You state:
Now, I cannot say much about Sheck Exley, other than that he died on one of his very deep dives. But the Cousteau dive, where they put 300 bar (300 bar x 14.7 psi/bar = 4410 psig) into those tanks, and they were so heavy in the water that they needed floats on them to make them divable using Cousteau's system. They were also probably only used on those particular dives (the Britannic?). Please take a look at these dives, and the tanks that they are using for their triples.
Now, a couple of points: --First, I don't think I've seen these tanks on any other of the Cousteau dives. That means that these tanks were only used on these Britannic dives. I don't remember seeing that at the Tacoma vintage diving museum, so I'm not sure whether they have survived. --Second, look at the floats Cousteau used to get them to neutral buoyancy. I think if you filled twin 72s to 3000+, their buoyance characteristics would be dramatically altered. --Third, Cousteau needed this to use the Aqualung, his creation, in deep water. He was diving to nearly 300 feet, as I recall. He did not, ever, like rebreathers, as he almost lost his life twice on oxygen rebreathers before inventing the Aqualung. --Fourth, I'll make some calculations, and get back to you about the amount of extra breathing air you will get by filling to 3000 psig.
Okay, here's the calculation:
71.2 ft3 / 2475 psi = x ft3 / 3000 psi
71.2 ft3 x 3000 psi / 2475 psi = X ft3
X ft3 = 213,600 ft3 / 2475
X = 86.3 ft3
The difference between the two:
86.3 ft3 - 71.2 ft3 = 15.1 ft3
Is it worth this to gain 15 cubic feet?
John
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Post by technidiver on Jul 3, 2019 21:41:49 GMT -8
Thats fair. Anything treated well would last long, especially the steel. I do agree there. The size of the tanks as well as the air caused the set to be extremely negative. Those are also massive tanks. I still have no idea what size they are. John, here's a post I refer to often. Ryan Spence's post I believe is the fifth one down and is my source about the hydrodynamic tank as well as the 5000 PSI tanks used in the 80s. Titanium I believe. vintagescuba.proboards.com/thread/340?page=2TD
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Post by technidiver on Jul 3, 2019 21:46:33 GMT -8
This brings me to my next point, would you change your mind if I threw the idea of overfilling a HP designed cylinder? Let's say a 3442 Faber to 4000 or to 300 bar. Across the pond that is normal, or so I hear! And DIN would be standard, I don't think they'll even cater to yoke divers LOL!
TD
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Post by technidiver on Jul 3, 2019 21:50:10 GMT -8
TD, I have a set of twin 45s that I've had since the 1980s. I have not overfilled them, and they are still in almost pristine condition. I dove them last Saturday at Big Eddy in the Clackamas River. They have been in continuous service since I bought them new, and are the only set I have that are that old. Treated well, steel tanks will last almost forever. You state: Now, I cannot say much about Sheck Exley, other than that he died on one of his very deep dives. But the Cousteau dive, where they put 300 bar (300 bar x 14.7 psi/bar = 4410 psig) into those tanks, and they were so heavy in the water that they needed floats on them to make them divable using Cousteau's system. They were also probably only used on those particular dives (the Britannic?). Please take a look at these dives, and the tanks that they are using for their triples. Now, a couple of points: --First, I don't think I've seen these tanks on any other of the Cousteau dives. That means that these tanks were only used on these Britannic dives. I don't remember seeing that at the Tacoma vintage diving museum, so I'm not sure whether they have survived. --Second, look at the floats Cousteau used to get them to neutral buoyancy. I think if you filled twin 72s to 3000+, their buoyance characteristics would be dramatically altered. --Third, Cousteau needed this to use the Aqualung, his creation, in deep water. He was diving to nearly 300 feet, as I recall. He did not, ever, like rebreathers, as he almost lost his life twice on oxygen rebreathers before inventing the Aqualung. --Fourth, I'll make some calculations, and get back to you about the amount of extra breathing air you will get by filling to 3000 psig. Okay, here's the calculation: 71.2 ft3 / 2475 psi = x ft3 / 3000 psi 71.2 ft3 x 3000 psi / 2475 psi = X ft3 X ft3 = 213,600 ft3 / 2475 X = 86.3 ft3 The difference between the two: 86.3 ft3 - 71.2 ft3 = 15.1 ft3 Is it worth this to gain 15 cubic feet? John 15 X 2 would be 30, so perhaps. For 15 alone, no. Might as well sling a pony. But for the added safety of extra air, hell why not. So it works out that for a "72" it's about 34.7 psi per foot of air.
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Post by SeaRat on Jul 3, 2019 21:53:01 GMT -8
TD, Thanks for that link. If you'll look at the photos of the seat, the Mistral seat has a very small metal disc in the center which receives the pin. For the USD Mistral, this disc is "floating" in the teflon materials for the seat. Because of this, what happened to mine was that it was pushed down and sideways, breaking the seal, and causing a heavy leak, at 3000 psig. It is possible that the LaSpiro Mistral is constructed differently, and that this "disc" is actually a part of the brass and anchored into the brass, so that it won't sink into the lighter material of the seat. Note the difference in the center of these two seats. Here's the difference in size of the two seats too. I still think that for the higher pressures, a two-stage regulator would be better. John
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Post by SeaRat on Jul 3, 2019 21:56:10 GMT -8
Here is the quote from Ryan Spence:
John
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Post by SeaRat on Jul 3, 2019 22:52:08 GMT -8
This brings me to my next point, would you change your mind if I threw the idea of overfilling a HP designed cylinder? Let's say a 3442 Faber to 4000 or to 300 bar. Across the pond that is normal, or so I hear! And DIN would be standard, I don't think they'll even cater to yoke divers LOL! TD TD, Maybe. A HP steel cylinder with a rated pressure of 3442 psig, having a 10% overfill, is 3786 psig. That is about 3800 psig (rounded). 200 psig more and you have 4000 psig. That's basically a 16% overfill. So, maybe... Now, I'd like to throw in a research question. If you decide to do this, and overfill the 2250 psig-rated tanks to 3000 plus psig, will you consider recording the dates of each overfill, and doing an actual hydro on the cylinders each year? Getting data is what I'm after, and I don't see anything concrete, other than hear-say evidence that this has been done. But if we can document that the overfilling did not deform the tanks outside the hydro limits, then we have something to go on. Of course, it may also document the opposite too, in which case you would probably want to know that the tank(s) are about to fail. John
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Post by Deleted on Jul 4, 2019 8:51:33 GMT -8
I'll throw my 2 cents in here: I have burst disks on one set of my twin 45's and both of my 72's.....they are for 3000 psi tanks and when I needed new disks to replace the old style lead bb's, this type is all the dive shop had.
That being said.........errors can occur...one dive shop pumped my twin 45's (voits) to 3500 psi by accident. The girl running the compressor was yapping at someone else and didn't pay attention when she set the tanks up for refill.....the burst didk let go and that was a interesting moment. She (the owner) replaced the burst disks with new ones but the lowest she had them for was again 3000 psi tanks. A year later that 1880 rated tank passed hydro with at 2025+ rating.
In 2005, my youngest son and I were on a dive boat in the Gulf with about 30-40 other folks. The guy who was assigned out of that party to refill everyones tanks didn't realize ours were 72's, not a newer hp tank. He filled them to 3000psi....when I reattached my reg to my tank I realized what he had done.....dumping 500psi from two tanks was a crowd gatherer on that little boat. (100 foot ex-oil rig crew boat)....one of those 72's was a 1962 manuf. date with the old vertical 1/2 j valve. Didn't show any signs of stress, still use it today.
I use my own compressor now, and keep my twins at 2000 and 2100 respectively and the 72's at 2500psi (cooling down to 2480 or so)
My point is, old steel can take a lot of abuse...I stretch mine a bit I know, but knowing where they have ventured in the past with refills I am not worried.....they will out last me and perhaps my son when he inherits them.
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Post by technidiver on Jul 4, 2019 9:48:37 GMT -8
This brings me to my next point, would you change your mind if I threw the idea of overfilling a HP designed cylinder? Let's say a 3442 Faber to 4000 or to 300 bar. Across the pond that is normal, or so I hear! And DIN would be standard, I don't think they'll even cater to yoke divers LOL! TD TD, Maybe. A HP steel cylinder with a rated pressure of 3442 psig, having a 10% overfill, is 3786 psig. That is about 3800 psig (rounded). 200 psig more and you have 4000 psig. That's basically a 16% overfill. So, maybe... Now, I'd like to throw in a research question. If you decide to do this, and overfill the 2250 psig-rated tanks to 3000 plus psig, will you consider recording the dates of each overfill, and doing an actual hydro on the cylinders each year? Getting data is what I'm after, and I don't see anything concrete, other than hear-say evidence that this has been done. But if we can document that the overfilling did not deform the tanks outside the hydro limits, then we have something to go on. Of course, it may also document the opposite too, in which case you would probably want to know that the tank(s) are about to fail. John John I think that's an excellent idea. I can acquire a 72 single tank for about $100 (Canadian so it would be cheaper for those of you south of me!) and to add to your idea, I run that tank a little higher than 3000, perhaps to 3200-3300. So a HP fill on my 72s, and then an ultra HP fill on a single. I've never been good with recording data, so I can attempt to make a spread sheet or something similar to aid with that. PM John if you have any additions. TD
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