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Post by snark3 on Jul 7, 2019 18:50:09 GMT -8
Our LDS just went up to $12 for a fill
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Post by snark3 on Jul 7, 2019 18:57:01 GMT -8
TD- I've often thought about trying to rig triple 72's. I was thinking making a set of doubles, then using a second set of bands to add a third tank. It could be set up either strait across or maybe in a triangle. Depending on the particular setup, one reg on the doubles and a second reg on the single. The biggest flaw I could think of was where am I going to get a crane to lift this mess?
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Post by technidiver on Jul 7, 2019 19:36:08 GMT -8
Skip, now this is where the fun begins. The setup is going to weight in at around 105 pounds empty, depending on what harness plate, etc you have with it. Add air. Another 10 pounds. Plus a wetsuit fins mask, and before you know it the kit is 120 pounds. I believe John has mentioned that before, but to add onto both of your ideas I believe an setup filled to 3000 PSI for 3 72s would work well in the way that the two tanks are manifolded with the third tank inverted. DH on the middle of the two tanks, with an LP hose the DH, meaning you can isolate the third tank as well as the other two tanks since the older manifolds only isolate the reg. When I disassemble my doubles in the fall for hydro (believe their due) I'll see what concoction I can rig. Disclaimer: rig is not to be used for everyday dives (only dives that you want to throw out your back and end up complaining the next week) TD
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Post by snark3 on Jul 8, 2019 10:42:45 GMT -8
TD- Why invert the third tank? Is there an advantage to having it inverted? I've heard of people doing this I just don't know why.
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Post by technidiver on Jul 8, 2019 10:52:17 GMT -8
TD- Why invert the third tank? Is there an advantage to having it inverted? I've heard of people doing this I just don't know why. To aid with turning off and turning on the valve in case of an emergency, or for isolation. Makes it much easier and handier. I've never tried it before, but it seems logical. TD
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seabob
Senior Diver
Instructor Trainer evaluator through all OW and Tech
Posts: 59
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Post by seabob on Jul 9, 2019 9:52:33 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 I have a set of twin 10 liter tanks I got while in Turkey in 2000. They physically are smaller than a 72, but are rated at 300 bar so hold around the equivalent of an AL 80.Manifold does not even have a burst disc. Being in North Florida, I am well aware of the double and triple discing of 72's The main concern is not tank rupture, but in the U.S. tanks have to be hydro tested. Continual overpressure actually stretches the tank to the point that eventually after a hydro it does not return to specification size. How do we get around that? Fill our own tanks. Hydro is a D.O.T. thing for interstate travel of compressed gas cylinders. Europe doesn't have the D.O.T.
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Post by technidiver on Jul 9, 2019 10:43:42 GMT -8
SeaBob, could you post a picture of those tanks with the manifold? Would love to see them!
Filled my 72s to 2600 today. LDS owner says "how much do you want in them?" My response "Ah just top them up past 2500."
I'm heading up to Tobermory in two weeks. When I head up to Tobermory, the tanks will be filled to 2800. Maximize space, money, and time. LOL.
TD
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Post by nikeajax on Jul 9, 2019 12:28:47 GMT -8
We have had many heated debates about the subject of the older aluminum tanks: but the reason why these tanks need to be hydro'ed is because they can and will crack under sustained loads. The critical test is the eddy current testing: this is used to find any cracking that might be happening, and it begins at a microscopic level and can take years to where they will have catastrophic-failures. The industry switched the alloy because of this type of sustained load cracking: as of now, the newer tanks do not crack like the older ones can.
I own one of these tanks, and if I use it, I make very certain that the eddy testing is up to date.
I may be wrong, but, I believe it was Luis who said they fail when they are being refilled, not while in a diving situation. But, what I do remember is, him saying is that a friend of his was killed when one of these tanks exploded: with very good reason this subject is something that gets his hackles-up!
JB
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Post by scubalawyer on Jul 9, 2019 17:58:17 GMT -8
We have had many heated debates about the subject of the older aluminum tanks: but the reason why these tanks need to be hydro'ed is because they can and will crack under sustained loads. The critical test is the eddy current testing: this is used to find any cracking that might be happening, and it begins at a microscopic level and can take years to where they will have catastrophic-failures. The industry switched the alloy because of this type of sustained load cracking: as of now, the newer tanks do not crack like the older ones can. I own one of these tanks, and if I use it, I make very certain that the eddy testing is up to date. I may be wrong, but, I believe it was Luis who said they fail when they are being refilled, not while in a diving situation. But, what I do remember is, him saying is that a friend of his was killed when one of these tanks exploded: with very good reason this subject is something that gets his hackles-up! JB I can attest to that. A few years ago I took my beloved yellow USD Twin 50's in for hydro and eddy testing because they were the BAD alloy. Both passed. I was ecstatic as I bought them new in 1976 and we had shared many an adventure together. Alas, on first fill post hydro/eddy testing I was getting micro bubbles out around one neck-valve seal. Changed o-rings again, even took a dremmel and some polishing brushes to clean out the seal area. Took a while of eliminating leak possibilities. Finally got out my son's old microscope and took a peak at the threads. Sure enough you bet your sweet bippy there was the itty bitty hairline crack running up through the neck threads. My beloved tanks are now a giant paperweight. M
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Post by nikeajax on Jul 9, 2019 18:18:35 GMT -8
Whenever I go into Steele's, Jim always has a few tanks laying about that have failed: they always have the crack marked with a black sharpie and "fail" scribbled right near the crack...
JB
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seabob
Senior Diver
Instructor Trainer evaluator through all OW and Tech
Posts: 59
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Post by seabob on Jul 10, 2019 4:10:54 GMT -8
SeaBob, could you post a picture of those tanks with the manifold? Would love to see them! Filled my 72s to 2600 today. LDS owner says "how much do you want in them?" My response "Ah just top them up past 2500." I'm heading up to Tobermory in two weeks. When I head up to Tobermory, the tanks will be filled to 2800. Maximize space, money, and time. LOL. TD I will take a couple of pictures and post a link as soon as I get a chance.
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seabob
Senior Diver
Instructor Trainer evaluator through all OW and Tech
Posts: 59
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Post by seabob on Jul 10, 2019 4:14:47 GMT -8
We have had many heated debates about the subject of the older aluminum tanks: but the reason why these tanks need to be hydro'ed is because they can and will crack under sustained loads. The critical test is the eddy current testing: this is used to find any cracking that might be happening, and it begins at a microscopic level and can take years to where they will have catastrophic-failures. The industry switched the alloy because of this type of sustained load cracking: as of now, the newer tanks do not crack like the older ones can. I own one of these tanks, and if I use it, I make very certain that the eddy testing is up to date. I may be wrong, but, I believe it was Luis who said they fail when they are being refilled, not while in a diving situation. But, what I do remember is, him saying is that a friend of his was killed when one of these tanks exploded: with very good reason this subject is something that gets his hackles-up! JB Agreed. The older AL tanks are a whole different issue from steel. When doing V.I.P.'s when I worked at a dive shop I actually saw some neck cracks. Owners weren't happy when I condemned them.
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seabob
Senior Diver
Instructor Trainer evaluator through all OW and Tech
Posts: 59
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Post by seabob on Jul 10, 2019 5:32:09 GMT -8
SeaBob, could you post a picture of those tanks with the manifold? Would love to see them! Filled my 72s to 2600 today. LDS owner says "how much do you want in them?" My response "Ah just top them up past 2500." I'm heading up to Tobermory in two weeks. When I head up to Tobermory, the tanks will be filled to 2800. Maximize space, money, and time. LOL. TD <center><a href="https://www.use.com/OiIMx" target="_blank"><img border="0" src="https://www.use.com/images/s_1/dfc4013328dccbcc31c7.jpg"></a></center> At 300 bar they actually total 211.88 cf
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Post by snark3 on Jul 10, 2019 9:33:12 GMT -8
I think I've posted this link before in another thread, but I think its worth repeating. underseadivers.com/wp1/gear/aluminum-tank-policy/ In my opinion a new AL 80 costs about $150, is it worth endangering yourself or the person filling the tank to save 150 bucks. I have 3 of these "ticking time bombs" I wont even store them with air in them. My AL50 is on the project list to be made into a gas grill.
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Post by SeaRat on Jul 10, 2019 12:26:03 GMT -8
We have had many heated debates about the subject of the older aluminum tanks: but the reason why these tanks need to be hydro'ed is because they can and will crack under sustained loads. The critical test is the eddy current testing: this is used to find any cracking that might be happening, and it begins at a microscopic level and can take years to where they will have catastrophic-failures. The industry switched the alloy because of this type of sustained load cracking: as of now, the newer tanks do not crack like the older ones can. I own one of these tanks, and if I use it, I make very certain that the eddy testing is up to date. I may be wrong, but, I believe it was Luis who said they fail when they are being refilled, not while in a diving situation. But, what I do remember is, him saying is that a friend of his was killed when one of these tanks exploded: with very good reason this subject is something that gets his hackles-up! JB Agreed. The older AL tanks are a whole different issue from steel. When doing V.I.P.'s when I worked at a dive shop I actually saw some neck cracks. Owners weren't happy when I condemned them. "The owners weren't happy when condemned them..."! My, they just don't understand the explosive power of compressed air. John
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