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Post by SeaRat on Nov 5, 2005 6:51:09 GMT -8
The Trieste II could accept a J-valve. AMF Voit made them off the first stage design for the Titan II, and both regulators could be modified to accept a J-valve on the regulator.
John
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Post by Gomez' echo on Nov 5, 2005 7:05:00 GMT -8
And here were a couple more: (Thanks to Roberts' Basic Scuba) The nortorious Northhill Air Lung: And the Viking Lung (affectionally known as the "beer-can regulator) Made by Christensen Tool & Engineering, Inc., 11 Commerce ST., Norwalk, Conn.
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Post by Captain on Nov 5, 2005 8:20:53 GMT -8
Several of the reported failures of steel tanks was a result of rust on the outside of the tank under the rubber or plastic boot. I would advise anyone using steel tanks to either don't use boots or remove them and rinse the tank and boot after every dive especially it was used in salt water.
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Post by luis on Nov 5, 2005 9:29:16 GMT -8
Those diagrams of the Northhill Air Lung and the Viking Lung are great.
Thanks simonbeans
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Post by nemrod on Nov 5, 2005 9:41:03 GMT -8
KC, I still have to say that tanks are not exploding regularly. It is an uncommon condition. Sure there have been various reasons both aluminum and steel tanks rupture. I don't see people swimming around with tanks popping on their backs--lol--that would almost be kinda funny. The only way to put your fear to rest is to look inside the tank and of course know what your looking for in there. You can get a small string light or wand light from your friendly local SnapOn truck. You might find something at Sears or even my least favorite tool junk store--Harbor Freight. To do good inspection you will need to get a fair amount of light in there.
KC, I guess the reason I tend not to worry about water in my tanks causing them to "explode" is that down in my basement I have a pile of tanks, many older than dirt and they ain't got no rust and they ain't gonna explode. I have looked inside lot's of abused tanks and from time to time see damage that might be dangerous but it is not something that keeps me up at night.
Some of the later model J valves from Dacor are 3000 psi service, I mostly dive with steel 72s as is probably the case with most vintage divers so J valves for 2450 psi are common.
"Just because a person's asking vintage diving questions and has a low post count doesn't mean they're a drooling idiot lol." Never said you were and I want to welcome you to vintage diving and please stay around and ask some more good questions so we got something to yammer on about! Yes, sincerely thanks for the questions.
The guys at works seem to always come to me for advice--beats me--I have learned though over the years, that people often don't initially give up all the goods---SO--- here is the thing, you are the best judge of your equipment/tanks safe condition. If you have some reason to believe your tank may be dangerous then please don't use it. Certain aluminum tanks have a history of neck fractures and other issues for example that are not really corrosion related.
I suck my tanks completely dry all the time--lol--in fact, my Mistral will breath a tank way down as might yours and I have several single hose units that will near about put a vacum on a tank!
Your local LDS is your first resource and often they do know what they are doing but these days I would take everything they say with a grain of salt until I have done buisness with them enough to trust them. Dive shops including the ones around here are not expert on anything other than selling plastic junk. They have no idea how to fill a tank with a J valve and several times I have had to show them how to operate their compressor. It is a weird world out there chocked full of misinformation.
Good luck and may your diving days be free of exploding tanks!
James
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Post by SeaRat on Nov 5, 2005 9:49:52 GMT -8
Here's one that never left the drawing board, but Emile Gagnan did design a single stage regulator with a J-style reserve. It became the AMF Voit 50 Fathom, without the reserve. John
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Post by luis on Nov 5, 2005 10:07:10 GMT -8
Hi SeaRat If you look at and take apart the top of a DCAR valve you will see a small orifice in the center of the adjusting slotted piece. You can unscrew the outer ring with pressure in the tank as long as the valve is closed and there is no regulator etc attached (I have done it many times). Inside you will find that that orifice leads to a small piston of the same diameter as the air flow orifice. The water pressure pushing into this piston works in parallel to the spring force. Therefore the ambient pressure (times the area, the areas cancel out) can be added linearly to the spring force. This is such a simple device it doesn’t require any extensive pneumatic analysis. As far as I know this is the only valve that contains that feature. The DCAR pressure compensation is additive to the so called pressure compensation caused by the fact that your regulator can operate with lower tank pressures at shallower depth. The fact that at shallower depth you can breathe with lower tank pressures is what Mr. Roberts is referring to when he talks about J valves being depth compensated. This is kind of stretch on my definition of depth compensated. I may be wrong or may be overlooking something, but I am qualified to perform pneumatic analysis on what is a relatively simple pneumatic system. My background includes 25 years as a mechanical engineer doing analytical work on many different types of systems (structural, pneumatics, hydraulics, heat transfer, etc.). I have been kiddingly known to being an anal kind of guy… lol. Back in the 70’s I also did regulator, valves and compressor repairs, as well as VIP’s and tank hydro testing. The statement from Mr. Balder that reads: “CAUTION: THE PRESSURE AT WHICH THIS WARNING TAKES PLACE IS INTERNAL CYLINDER PRESSURE AND NOT THE SURROUNDING PRESSURE”, is a true statement. The 300 psi reserve mechanism is going to activate at 300 psi independent of depth. This is a constant volume of air held in reserve. For a two stage regulator to breathe easily you have to supply it with a pressure above its intermediate pressure plus the ambient pressure. This provides a depth compensation feature that works above and beyond the truncating pressure of the reserve valve. It actually works whether you have a reserve or not. If you take your regulator to 670 ft, it will need 300 psi + the IP above the truncating pressure of the reserve, but the reserve will be the same. Unless you are Nemrod; he claims he can pull a vacuum out of a tank. The precise behavior of the reserve will vary a little, depending on whether it’s restricting mechanism has a soft or a hard seat. Another great feature of the DCAR valve is that you can work on the reserve with air in the tank. Back in the 70’s (when I lived in Puerto Rico), when we flew to the Virgin Islands I used to trick the reserve so we could leave about 100 psi (or less, a low safe pressure) and luggage handlers in PR couldn’t tell. When we arrived at the VI, I replaced the appropriate parts and went to the LDS to fill the tanks. On the way back home I normally didn’t bother since it was easy for me to remove the valves and look inside.
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Post by SeaRat on Nov 5, 2005 11:04:48 GMT -8
Luis,
Great information. I'll look at that valve later this weekend. I stand corrected, and appreciate this forum for providing access to this kind of information. It informs us all.
I am curious about one of your statements above:
Does this mean that a regulator with the J-reserve feature (Trieste II or Sportsways Navy and Calypso single hose) would be depth compensated?
John
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Post by luis on Nov 5, 2005 11:19:34 GMT -8
“Does this mean that a regulator with the J-reserve feature (Trieste II or Sportsways Navy and Calypso single hose) would be depth compensated?”
Yes, by the definition of depth compensated as mentioned by Mr. Roberts (and others in the industry, as described above), but not by the added reserve pressure that a DCAR valve will provide.
The J valve mechanism incorporated into those regulators is located in the flow path before the first stage mechanism. They behave the same as if they were physically located in the tank valve.
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Post by SeaRat on Nov 5, 2005 11:54:26 GMT -8
Luis, Thanks. Others, This thread came with the question about how to dive without a SPG. My recommendation is not to dive without a SPG and a K-Valve (no reserve), unless a J-valve mechanism is incorporated into the regulator. Diving, even in shallow water, without any reserve is not a good idea. Some regulators have the calibrated orifice reserve (automatic reserve), and that works as long as the diver is not in an overhead environment. As stated by KC, you can dive with a K-valve with a bail-out bottle (Spare Air, or a second cylinder) and maintain a safety factor. The regulator J-valve on a double tank unit has an advantage, in that it reserves 300 psi in both cylinders, rather than 500 psi in one cylinder. I'm thinking of doing some diving where I have no SPG (river diving, less than 30 feet depth), and use both a 300 psi reserve on my regulator and a 500 psi J-reserve on one cylinder. If I do that with my twin 42s, then I've made the following calculations: 500 psi/1800 psi = X / 42 cubic feet; X = 11.67 cubic feet of reserve air in the reserve cylinder 300 psi/1800 psi = X / 72.33 cubic feet; X = 12.06 cubic feet of reserve air in the rest of the twin cylinder block Total in reserve = 300 psi reserve + 500 psi reserve = 11.67 cubic feet + 12.05 cubic feet = 23.7 cubic feet of air in reserve If I do this, then I am retaining in reserve (the two different reserves) 28% of my air supply. Cousteau, and many French divers, used the triple tank system, but a reading of the patent (US Patent #2,485,039) shows that they held one entire cylinder of the three-cylinder aqualung as their reserve. It was activated by a valve at the bottom of the reserve cylinder. When Cousteau's team went to the quad aqualungs, they again held one full cylinder as their reserve, and again it was activated by opening a valve at the bottom of the unit. In the Cousteau-Gagnan patent, they state: I changed one word in this, from a word that would not get through the internal checking system for obscene words to the word "valve." John
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Creed
Pro Diver
Posts: 189
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Post by Creed on Nov 5, 2005 20:32:11 GMT -8
There have been several studies related to tank corrosion. In particular at Battelle Memorial Institute and the University of Rhode Island. To make a long story short, the presence of water, especially salt water, in combination with the high partial pressure of oxygen in a SCUBA tank can cause enough oxidation to cause a tank to fail in a relatively short time period. It is worst for steel tanks, but aluminum tanks will also pit. In one test (in the 1970’s) at the University of Rhode Island they kept steel tanks with a little salt water and full pressure in a warm environment. At the end of a 100 day test the tanks had lost as much as 2/3 of the wall thickness. This is enough for a catastrophic failure / explosion. If your tank is ever fully discharged (empty) you don’t need a new VIP sticker, but you do need to make sure the inside is dry before refilling. The easiest way to check is to look inside. True. Salt and warmth will eat a tank easily. But, the original poster specifically asked about diving in a quarry, which I assume would be fresh water. As such, he would have quite a bit more time to clean out the tank.
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Post by joaquim on Nov 5, 2005 21:09:16 GMT -8
I belive the sequence of scuba valve nomenclature went something like: I valves (pillar, post etc with a tiny on/off butterfly knob on the top) J valves (sporting a reserve switch and the on/off knob on the side) and then K valves (j valves without the reserve and on/off knob on the side).........
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Post by duckbill on Nov 6, 2005 2:07:04 GMT -8
Hi Luis. Thankyou for taking the time to clarify and make corrections to the J-valve discussion. I lost some sleep and got a headache trying to make heads or tails out of Mr. Fred Roberts' explanation. I love his "Basic SCUBA" book, but I think he could have been more clear here, and may possibly even have been wrong. I am still trying to understand what he was trying to say. I'm not so sure that you understand him correctly either (no offense), as your idea of what he was saying would be just as true for a regulator on a K-valve: The fact that at shallower depth you can breathe with lower tank pressures is what Mr. Roberts is referring to when he talks about J valves being depth compensated. This is kind of stretch on my definition of depth compensated. Mr. Roberts is specifically talking about the "cut off point", but I think he gets the concept reversed. In light of Mr. Balder's statement, I think that the ambient pressure is supposed to be subtracted from the cut off pressure, not added to it. The cut off pressure doesn't change at depth with reference to the tank, but does change relative to the ambient pressure. Ref. Fred Roberts- "Basic SCUBA" "Because the regulator supplies air at ambient pressure, the spring setting will always be the reserve spring value plus ambient pressure. The resulting pressure will be the cut off point. For example, at 100 feet the gauge ambient pressure is over 44 psig greater than it is at the surface; thus regulator cut off is about 44 psig higher and reserve will therefore occur at 344 psig rather than 300 psig." Obviously, it is very easy to check a pressure gauge hooked up to an HP port to see that depth makes no difference to the actual cut off pressure. I haven't noticed any changes, and I wouldn't expect to see any either, considering that my J-valve and SPG are sealed from the effects of ambient pressure. I found Mr. Balder's caution to be more practical and easy to understand. He makes the (correct) point that the reserve cut off pressure, while constant to the rigid cylinder, is going to be lower relative to the ambient pressure. Ref. Mr. Balder- "The Complete Manual of Skin Diving", as quoted by SeaRat "CAUTION: THE PRESSURE AT WHICH THIS WARNING TAKES PLACE IS INTERNAL CYLINDER PRESSURE AND NOT THE SURROUNDING PRESSURE. Therefore, for example, at a 100-foot depth, about 50-psi water pressure, a 300-psi tank reserve would be only 250 psi more than the water pressure." And, yes, at 673 ft. a regulator would see exactly zero pressure from the tank at a 300 psi reserve cut off. The pressure in the tank would be 300 psig, just as the ambient pressure would also be 300 psig= NO RESERVE! until you begin an ascent (I hope you're not breathing air and have about 100 decompression stage bottles and some meals along the way ). I sure wish I knew exactly to what Mr. Roberts was referring.
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Post by RMannix on Nov 6, 2005 3:32:15 GMT -8
Nope i'm using an al 80 and a dw mistral, You might not want to use that tank at 3000 PSI with the DW Mistral, it can damage the reg.
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Post by nemrod on Nov 6, 2005 10:50:40 GMT -8
"You might not want to use that tank at 3000 PSI with the DW Mistral, it can damage the reg."
Yeah, I caught that too but there was a thread some time back and I guess some people have tried it. The bad thing is that Mistral seats are rare and expensive. I just got a brand new one to save for a rainy day. I think much use at 3000 psi would damage the seat. I would not put my Mistral to that abuse anyway. I suppose people on a budget have to do with what they got as they begin vintage diving. The cost of a long yoke, a banjo bolt for spg and finding a good steel 72 can be an expense undertaking plus the other odds and ends so it takes time to accumulate the goodies, oh, and the J valve, and on top of that many folks run into the LDS nazis who simply want to grind your vintage gear into scrap and sell you brand new TUSA plastic junk and Sea Knight super BC constrictors with 25 D rings. I think it is diffucult to imagine how someone not from the vintage era could/would be mislead by "modern" diving practice and training and how much actual misinformation exists out there. I have in my hand an old Skindiver from 63 where there is a Nemrod adv. and the copy reads , "C'mon in... the water is fine". The lady has a wonderful looking wet suit and a strange looking single hose with a J valved tank. The fellow has a double hose also on a J valve tank. If I had to guess I think the picture was taken at Alexander Springs Fla. They have no BCs, no MaeWests no nothing. I can see their J rods and their simple tank harness, this is like a time warp---the way it was. I notice he has no weight belt and she has a weight belt slung low on her hips. Has anyone noticed that nowadays people wear the weight belt cinched up under their arm pits very nearly? When I use a weight belt I leave it so loose it barely is prevented from falling off my hips so that it sits below my tank waist strap. I suppose in the pre BC era the loss of a belt was no big deal because you did not have the super SeaKinght supercharged 25 D ring 75 lb lift BC engulfing your person that would rocket you to the surface. The contrasts are amazing. James
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