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Scuba Forum / General / September 2004Tank Size Question
Ok, a question on tank size and pressure: Lets take two aluminum tanks, both 80 CuFt. One is rated 3000 psi Service Pressure and the other tank rated 3300 psi Service Pressure. What exactly is the difference here in performance between 3000 psi and 3300 psi? The amount of air a tank can hold is based on the cubic foot, right? So if both tanks are 80CuFt, then why would I want one rated for 3300psi? When your filling tanks, and the psi on the tank says 3000, then that means when the pressure gauge on the compressor read 3000 then your tank is filled, right? What about the 3300 tank? Do you have to fill it to 3300 psi to fill it up for use? If so, wouldn't that mean you have more air in the tank to breath? With 3300 psi, aren't you shoving more air into the tank than the 3000 psi tank? Please explain. Thanks > Please explain. You got ripped off in you cert class. Just like everyone else.  Signature"We're going to rush the hijackers." -Jeremy Glick, aboard United Airlines flight 93, September 11, 2001 > When your filling tanks, and the psi on the tank says 3000, then that >means when the pressure gauge on the compressor read 3000 then your tank is [quoted text clipped - 4 lines] >breath? With 3300 psi, aren't you shoving more air into the tank than the >3000 psi tank? The 3300psi tank will have a slightly smaller internal volume. You have to pump it to a higher pressure, but you still only pump 80cf into it. The 3000psi tank will also still contain roughly 13.3cf at 500psi. The 3300psi tank will contain roughly 12cf at 500psi, which means that the ONLY positive effect of the higher pressure cylinder is that it gives you 1cf more air to use before the DM bitches at you. IOTW, there is no reason to select the 3300 over the 3000. 80cf is 80cf, no matter the starting pressure. --- Rich http://richlockyer.tripod.com/ > The 3000psi tank will also still contain roughly 13.3cf at 500psi. > The 3300psi tank will contain roughly 12cf at 500psi, which means that > the ONLY positive effect of the higher pressure cylinder is that it > gives you 1cf more air to use before the DM bitches at you. Not true. Depending on the brand, there is a size difference, and it is signficant to some, and a buoyancy difference, enough to be significant to everybody. > IOTW, there is no reason to select the 3300 over the 3000. That is entirely a matter of opinion. My opinion differs from yours. All of my 80 cubic foot tanks are Catalina Compact 80s. They're about an inch shorter than the standard 80, making it possible for me to carry them without bending my elbows, ie making them easier to carry, and their about 4 lbs less buoyant, allowing me to dive my steel plate and wing, in warm water, with no lead at all. I'd say those are a couple of pretty good reasons to select the 3,300 over the 3,000. Lee > > The 3000psi tank will also still contain roughly 13.3cf at 500psi. > > The 3300psi tank will contain roughly 12cf at 500psi, which means that [quoted text clipped - 14 lines] > water, with no lead at all. I'd say those are a couple of pretty good > reasons to select the 3,300 over the 3,000. I was told at my dive class the aluminum 80 3000 psi was the most popular and standard use tank in the U.S. and Caribbean and general dive industry. Is this true? What about Australia and the Pacific Islands? I asked my instructor why he uses all aluminum, he said they don't rust as bad, and cheaper too. But aren't steel tanks supposed to last longer than aluminum? And if you have to get an internal inspection every year for rust, what difference does it make anyway? As long as you end all dives with at least 500psi in your tanks then why worry about water getting in? And don't steel tanks load to lower psi than aluminum? Isn't this easier on compressors? Instead of constantly filling tanks up to 3000 they could be filling tanks up to 2600psi or whatever, and the compressor wouldn't have to work as hard. <snip> > I was told at my dive class the aluminum 80 3000 psi was the most > popular and standard use tank in the U.S. and Caribbean and general dive [quoted text clipped - 9 lines] > filling tanks up to 2600psi or whatever, and the compressor wouldn't have to > work as hard. they don't rust at all! but they can corrode the 'paint' will lift off and be replaced by a white crust - not dangerous however. Al tanks aren't inspected for rust - they are inspected for cracks. Al tanks, when they do fail, tend to fail explosively. Al is more prone to stress fracture than steel. there is also the buoyancy question - a steel tank will often be more negative than Al ( the other advantage to a 3300psi Al bottle over a 3000psi Al one ) the "standard" Al 3000psi tank is ~ 4 lbs positive empty - thats 4 lbs of lead you need to wear. A comparable steel bottle will be ~neutral empty. there is also reg wear to consider a higher pressure in the tank causes more wear on the HP seat in the reg. > I was told at my dive class the aluminum 80 3000 psi was the most > popular and standard use tank in the U.S. and Caribbean and general dive > industry. Is this true? What about Australia and the Pacific Islands? It's the most common tank in the US. I'm less certain about its popularity. There are a lot of people that really like low pressure tanks and more than a few that like tanks rated for pressures even higher than the 3,300 psi you asked about. > I asked my instructor why he uses all aluminum, he said they don't rust > as bad, and cheaper too. They don't rust at all and they're considerably cheaper than comparable sized steel tanks. > But aren't steel tanks supposed to last longer than aluminum? How many lifetimes do you expect to use them for? > And if you have to get an internal inspection every year for > rust, what difference does it make anyway? Rust is only one of the things internal inspections look for, which is why aluminum tanks have to inspected too, at least that's what the shops that charge for the inspections say. > And don't steel tanks load to lower psi than aluminum? Not a meaningful question. Any tank can be loaded to any pressure up to its maximum working pressure. My old steel tanks, if I recall correctly, were rated for 2,450 psi. My wife's old aluminum tanks were rated to 3,000 psi. My current aluminum tanks are rated for 3,300 psi and my current steel tanks are rated for 3,500 psi. Any of them can be filled to a lower pressure simply by putting less gas in them. > Isn't this easier on compressors? Instead of constantly filling tanks up to 3000 they could be > filling tanks up to 2600psi or whatever, and the compressor wouldn't have to > work as hard. For most of us, it's not our compressor. You can fill to a lower pressure, but if you do, you get less gas or a bigger container. The primary advantage of high pressure fills is more gas and less space. Lee > > I was told at my dive class the aluminum 80 3000 psi was the most > > popular and standard use tank in the U.S. and Caribbean and general dive [quoted text clipped - 10 lines] > They don't rust at all and they're considerably cheaper than comparable > sized steel tanks. So, if I was going to buy two or three tanks for personal use, and I don't mind paying a few hundred dollars more for steel, should I definitely go with the steel or is it more of a personal choice? No tech diving for me, just recreational and no deeper than 100 feet. Also, what are the major companies that make tanks? I've seen mentioned Cataline and Luxfer. Is one better than the other? Has one company had more problems (explosive tanks!) than the other? I was on one online scuba shop, all the steel tanks they sell come with DIN. Is this standard for all or most steel tanks to use DIN over yoke? > So, if I was going to buy two or three tanks for personal use, and I > don't mind paying a few hundred dollars more for steel, should I definitely > go with the steel or is it more of a personal choice? No tech diving for > me, just recreational and no deeper than 100 feet. At this stage you are only prepared for shallow rec diving. If you are gonna buy tanks, buy the cheapest you can get (used al 80s, $35). But why buy tanks at all? If you travel, you won't be carrying them, if you dive less than 50 local dives a year, it's cheaper to rent them (purchase + annual vis + hydros + wirebrushing and painting). I own a couple sets of tanks, but only because I like to be able to go out on short notice and I don't want to be chasing around for custom fills. > Also, what are the major companies that make tanks? I've seen mentioned > Cataline and Luxfer. Is one better than the other? Has one company had > more problems (explosive tanks!) than the other? There are several companies that make tanks, none that I know of make both al and steel (though they sell under a variety of brand names). All currently manufactured tanks are equal in quality. Some older tanks use materials no longer acceptable. > I was on one online scuba shop, all the steel tanks they sell come with > DIN. Is this standard for all or most steel tanks to use DIN over yoke? Steels are almost all high pressure, and din is preferred for high pressure. Some (not all) din valves can be adapted to accept an A-clamp (yoke). Never use adapters on any piece of scuba gear. Adapters are for folks that bought the wrong piece of gear in the first place. >go with the steel or is it more of a personal choice? No tech diving for >me, just recreational and no deeper than 100 feet. Just go with a couple of Catalina or Luxfer 3000psi 80's. They'll last forever, and when you go on vacation, other than compensating for the buoyancy change in your suit, you won't have to make any other changes for rental tanks. The 3300psi 80s are indeed neutral, but that means that you'll need to add (somewhere around) 4 pounds for vacation dives, their weight distribution/trim may not be the same (meaning you get used to it, then end up on vacation with a standard 80 and have trouble keeping your feet up or down), and in many places, you may have trouble getting a fill to 3300. --- Rich http://richlockyer.tripod.com/ > >go with the steel or is it more of a personal choice? No tech diving for > >me, just recreational and no deeper than 100 feet. [quoted text clipped - 10 lines] > your feet up or down), and in many places, you may have trouble > getting a fill to 3300. All true. > So, if I was going to buy two or three tanks for personal use, and I > don't mind paying a few hundred dollars more for steel, should I definitely > go with the steel or is it more of a personal choice? No tech diving for > me, just recreational and no deeper than 100 feet. It's really a matter of personal choice. The biggest issues are buoyancy and trim. Different tanks have different buoyancy characteristics. I have 3,300 psi aluminum Catalina tanks. I like the fact that they are neutral when empty and, thanks to a lot of years of diving, my relatively low consumption rate allows me to stay down at moderate depths as long as most dive operators are willing to wait for me. I have 4 high pressure steel 100 cubic foot tanks. They're still less buoyant, but give me the gas to let me stay a bit deeper as long as I can stay shallower with the 80s. > Also, what are the major companies that make tanks? I've seen mentioned > Cataline and Luxfer. Is one better than the other? Has one company had > more problems (explosive tanks!) than the other? Catalina has been a high quality manufacturer from the beginning. Their tanks have had very few problems. Luxfer is the number one producer of aluminum tanks. They're also one of the manufacturers that used an inferior alloy up until about 1988. Since then, they've used the same alloy that Catalina always did. Luxfers tend to be a few bucks cheaper and a lot easier to find. I had to order my last two Catalina tanks. My steel tanks are made by PST. I really like the 232 bar valve on the new ones. It's convertable, allowing me to use either my Yoke/A Clamp regulators or my DIN regulators. My older steel tanks are also PST, but have the old 300 bar valves. They're usable only with my DIN regulators. > I was on one online scuba shop, all the steel tanks they sell come with > DIN. Is this standard for all or most steel tanks to use DIN over yoke? In the US, all high pressure tanks I know of come with DIN valves. I believe the low pressure steel tanks are available with A clamp, but you'll have to ask those that prefer them. That's not me. If you decide on hp steel tanks, check with diversdirect.com. They have good prices on the new style PST tanks. Lee > I was told at my dive class the aluminum 80 3000 psi was the most >popular and standard use tank in the U.S. and Caribbean and general dive >industry. Is this true? What about Australia and the Pacific Islands? For the most part, yes. > I asked my instructor why he uses all aluminum, he said they don't rust >as bad, and cheaper too. Cheaper is the primary reason. $100 vs $300. >But aren't steel tanks supposed to last longer >than aluminum? A lifetime, if cared for. >And if you have to get an internal inspection every year for >rust, what difference does it make anyway? As long as you end all dives >with at least 500psi in your tanks then why worry about water getting in? Water can still be blown in during filling. >And don't steel tanks load to lower psi than aluminum? Isn't this easier on >compressors? Instead of constantly filling tanks up to 3000 they could be >filling tanks up to 2600psi or whatever, and the compressor wouldn't have to >work as hard. Yup. Hey Jammer... he's one up on most OW graduates. --- Rich http://richlockyer.tripod.com/ > > I was told at my dive class the aluminum 80 3000 psi was the most > >popular and standard use tank in the U.S. and Caribbean and general dive > >industry. Is this true? What about Australia and the Pacific Islands? > > For the most part, yes. Well, as long as he is taking his own tanks to every dive location he visits, it probably doesn't really matter, does it? > > I asked my instructor why he uses all aluminum, he said they don't rust > >as bad, and cheaper too. > > Cheaper is the primary reason. $100 vs $300. VonF will be saving so much money because he purchased his own tanks to take on vacation with him. > >But aren't steel tanks supposed to last longer > >than aluminum? > > A lifetime, if cared for. Yeah, someone should remind him that the air pressure from being in the hold of the planes doesn't hurt the tanks at all. > >And if you have to get an internal inspection every year for > >rust, what difference does it make anyway? As long as you end all dives > >with at least 500psi in your tanks then why worry about water getting in? > > Water can still be blown in during filling. Of course, that's why we all look after our own gear. We can then make sure that none of that sort of thing happens. > >And don't steel tanks load to lower psi than aluminum? Isn't this easier on > >compressors? Instead of constantly filling tanks up to 3000 they could be [quoted text clipped - 4 lines] > > Hey Jammer... he's one up on most OW graduates. I don't think VonF has even shown up on Jammer's radar yet. (wg) > I don't think VonF has even shown up on Jammer's radar yet. Who? Signature"We're going to rush the hijackers." -Jeremy Glick, aboard United Airlines flight 93, September 11, 2001 > ? I don't think VonF has even shown up on Jammer's radar yet. > > Who? Exactly. "Never heard of him." > € I don't think VonF has even shown up on Jammer's radar yet. > > Who? Ah. The spotted owl speaks. > > ? I don't think VonF has even shown up on Jammer's radar yet. > > > > Who? > > Ah. The spotted owl speaks. You are up late. But at least most of us aren't still calling . . . whooo, whooo, whoooo, is this whistler guy? >>>€ I don't think VonF has even shown up on Jammer's radar yet. >>> [quoted text clipped - 3 lines] > > You are up late. Shhhh... You're disturbing the game... > >>>? I don't think VonF has even shown up on Jammer's radar yet. > >>> [quoted text clipped - 5 lines] > > Shhhh... You're disturbing the game... ;^) I'm sure you haven't forgotten that trying to get me to be quiet, only makes matters worse. But on that note, this place is all yours for a few hours. I'm taking my insomnia to bed and see how it works out. 'til tomorrow. >> > I was told at my dive class the aluminum 80 3000 psi was the most >> >popular and standard use tank in the U.S. and Caribbean and general dive [quoted text clipped - 4 lines] >Well, as long as he is taking his own tanks to every dive location he >visits, it probably doesn't really matter, does it? Of course not, but if he's wondering for dive planning purposes.... Imagine arriving at a destination where all of the dives are wonderful 120ft wall dives, and all they have are Al63s. Ugg. >> > I asked my instructor why he uses all aluminum, he said they don't >rust [quoted text clipped - 4 lines] >VonF will be saving so much money because he purchased his own tanks to take >on vacation with him. Cheaper is the reason... but not cheaper for the actual user silly. >> >And if you have to get an internal inspection every year for >> >rust, what difference does it make anyway? As long as you end all dives [quoted text clipped - 4 lines] >Of course, that's why we all look after our own gear. We can then make sure >that none of that sort of thing happens. Whether we do or not, making sure that you always have 500psi is no guarantee that you won't get a wet fill. >> Hey Jammer... he's one up on most OW graduates. > >I don't think VonF has even shown up on Jammer's radar yet. > >(wg) Oh yes he has :) --- Rich http://richlockyer.tripod.com/ > >> > I was told at my dive class the aluminum 80 3000 psi was the most > >> >popular and standard use tank in the U.S. and Caribbean and general dive [quoted text clipped - 8 lines] > Imagine arriving at a destination where all of the dives are wonderful > 120ft wall dives, and all they have are Al63s. Ugg. He will probably find that he's using the tanks offered by the dive op at his vacation spot. I'm sure that if the op normally takes their clients (divers) out for 120 ft wall dives, they don't have too many Al63's. > >> > I asked my instructor why he uses all aluminum, he said they don't > >rust [quoted text clipped - 6 lines] > > Cheaper is the reason... but not cheaper for the actual user silly. Silly? Silly? Who me? OK, OK, ya tagged me. Now you are IT. (wg) > >> >And if you have to get an internal inspection every year for > >> >rust, what difference does it make anyway? As long as you end all dives [quoted text clipped - 7 lines] > Whether we do or not, making sure that you always have 500psi is no > guarantee that you won't get a wet fill. LOL. > >> Hey Jammer... he's one up on most OW graduates. > > [quoted text clipped - 3 lines] > > Oh yes he has :) "Who?" Jammer, Sept. 5/2004 >> Of course not, but if he's wondering for dive planning purposes.... >> Imagine arriving at a destination where all of the dives are wonderful [quoted text clipped - 3 lines] >his vacation spot. I'm sure that if the op normally takes their clients >(divers) out for 120 ft wall dives, they don't have too many Al63's. True... but it could happen. He was just wondering. >> Cheaper is the reason... but not cheaper for the actual user silly. > >Silly? Silly? Who me? OK, OK, ya tagged me. Now you are IT. (wg) Yup. >> >I don't think VonF has even shown up on Jammer's radar yet. >> > [quoted text clipped - 3 lines] > >"Who?" Jammer, Sept. 5/2004 He was just pulling your lovely leg. --- Rich http://richlockyer.tripod.com/ > He was just pulling your lovely leg. Now, *there's* an image I can sleep with... Signature"We're going to rush the hijackers." -Jeremy Glick, aboard United Airlines flight 93, September 11, 2001 >> He was just pulling your lovely leg. > >Now, *there's* an image I can sleep with... Nighty night. --- Rich http://richlockyer.tripod.com/ > > I was told at my dive class the aluminum 80 3000 psi was the most > >popular and standard use tank in the U.S. and Caribbean and general dive [quoted text clipped - 11 lines] > > A lifetime, if cared for. The same claim was maid for aluminum tanks. So far, Catalina tanks have lived up to the claim. Luxfers didn't. > >And if you have to get an internal inspection every year for > >rust, what difference does it make anyway? As long as you end all dives [quoted text clipped - 8 lines] > > Yup. Funny, I could swear my 3,500 psi tanks are steel. Lee >> >compressors? Instead of constantly filling tanks up to 3000 they could >be [quoted text clipped - 5 lines] > >Funny, I could swear my 3,500 psi tanks are steel. Yup... and about availability now? PST cylinders are harder to find in SoCal than Neutronium. LDS got one set of double 104/130's in and said it'll be December before he MAY get another set. PST was forced to move their factory and has significantly scaled back on Scuba cylinder production. Sport Chalet still has a bunch of 3000psi LP 80's (with '02 hydros... and only 80cf at 3300 under the "plus" hydro) in stock, but the new tanks are a Norris (Kaiser Steel) 80 that still carries a plus rating, but fills to 3000psi under the plus. The thing is as heavy as an old PST LP104. --- Rich http://richlockyer.tripod.com/ > The 3000psi tank will also still contain roughly 13.3cf at 500psi. > The 3300psi tank will contain roughly 12cf at 500psi, which means that > the ONLY positive effect of the higher pressure cylinder is that it > gives you 1cf more air to use before the DM bitches at you. Funny way of looking at performance instead of reserve. BTW this is only true if the shop fill monkey actually fills the tank 3300 tank to 3300. If he stops at 3000 then there is 6cf LESS usable gas compared to the standard 3000psi AL80. (Based on true size of AL80 and delta pressure of 2500psi with service pressures of 3300 and 3000 ) > Ok, a question on tank size and pressure: > Lets take two aluminum tanks, both 80 CuFt. One is rated 3000 psi > Service Pressure and the other tank rated 3300 psi Service Pressure. What > exactly is the difference here in performance between 3000 psi and 3300 psi? > The amount of air a tank can hold is based on the cubic foot, right? So > if both tanks are 80CuFt, then why would I want one rated for 3300psi? The 3,300 psi tank will have a smaller internal size and, most likely, a smaller external size as well. In fact, the Catalina 3,300 psi 80 cubic foot tanks are about an inch shorter than the standard 80. That doesn't sound like much, but if you're on the short side of average, my 5'8" for example, that inch makes a big difference in how easy it is to carry the tanks. Currently, all 3,300 psi 80 cubic foot aluminum tanks are also about 4 lbs less bouyant than their 3,000 counterparts. That's 4 lbs of lead you don't can take off your weight belt, assuming of course, that you have 4 lbs on your weight belt otherwise. This has an added advantage that most don't expect. A standard 80, as it gets close to whatever minimum pressure you think appropriate, becomes bouyant and tend to be less stable on your back. The 3,300 psi tank, being neutral when empty, don't ever do this. Neither tank is going to float away on you, but there is a definite difference in how secure the less buoyant tanks feel. > When your filling tanks, and the psi on the tank says 3000, then that > means when the pressure gauge on the compressor read 3000 then your tank is > filled, right? You'd think so, but normally no . . . sort of. The 3,000 psi tank will be full when the pressure guage reads 3,000 psi AND the tank and gas in it have returned to room temperature. Gas heats up during the fill process. Most shops fill tanks to something more than 3,000 to get a temperature stabilized 3,000. > What about the 3300 tank? Do you have to fill it to 3300 psi to fill it > up for use? If so, wouldn't that mean you have more air in the tank to > breath? With 3300 psi, aren't you shoving more air into the tank than the > 3000 psi tank? Yes, no and no. Yes, you have to fill it to 3,300 to get the rated volume, but you don't have to fill it completely to use it. Most do, but you don't have to. If the internal volume of the 3,300 psi tank were the same as the internal volume of the 3,000 psi tank, then the higher pressure would mean more gas. The internal volume is not the same. They're called 80 cubic foot tanks because they each hold enough gas at their rated pressure to fill, if expanded to 1ata, to fill about 80 cubic feet. To make matters a bit more complex, most 80 cubic foot tanks actually hold about 78 cubic feet at their rated pressure. 80 is more a term of convenience than an accurate measurement. Lee > Ok, a question on tank size and pressure: > The amount of air a tank can hold is based on the cubic foot, right? So > if both tanks are 80CuFt, then why would I want one rated for 3300psi? I'm still trying to figure that one out myself :-) > When your filling tanks, and the psi on the tank says 3000, then that > means when the pressure gauge on the compressor read 3000 then your tank is > filled, right? Ignoring "hot fills", yes. > What about the 3300 tank? Do you have to fill it to 3300 psi to fill it > up for use? When it is filled to 3300psi, it has 80ft^3. But what this also means is that at 3000psi, its only 3000/3300 = 90% full: it will have 3000/3300 of 80ft^2, or roughly only 72ft^3. > If so, wouldn't that mean you have more air in the tank to breath? No. Its confusing because in the USA we refer to a tank by its capacity when it is filled to its operating pressure, instead of by its actual "dry" volume. > With 3300 psi, aren't you shoving more air into the tank than the > 3000 psi tank? You're not really shoving in "more" air. What happens is because the higher psi tank is physically smaller, you have to shove harder to get it in there... Think of taking the same amount of clothing on a trip, but packing it all into a smaller suitcase...you don't end up with more clothes. For two tanks of the same "size" rating, the one with the higher pressure will be a physically smaller tank internally. Externally, the tank _should_ also be smaller, but you do need more "meat" to the tank to withstand the higher operating pressure, plus the manufacturer may choose to do some other stuff too. For the 10% difference between an 80ft at 3000psi versus 3300psi, some people won't be able to eyeball the difference. For any group of tanks that all each rated at 80ft^3, all you're really doing is playing around with the formula: PV = constant Here, its (3000psi)(691in^3) = (3300psi)(628in^3) = "80ft^3" Just watch your units. -hh " H. Huntzinger" <{NOSPAM-rm_to_reply}rec-scuba@huntzinger.com> wrote in message news:{NOSPAM-rm_to_reply}rec-scuba-C77ED7.07453904092004@news-east.dca.gigan ews.com... > Think of taking the same amount of clothing on a trip, but packing it > all into a smaller suitcase...you don't end up with more clothes. Now that's something I can understand. It's starting to make sense now. Thanks > > With 3300 psi, aren't you shoving more air into the tank than the > > 3000 psi tank? [quoted text clipped - 8 lines] > For two tanks of the same "size" rating, the one with the higher > pressure will be a physically smaller tank internally. really well put! > -hh > Ok, a question on tank size and pressure: > [quoted text clipped - 17 lines] > > Thanks If you take 80 cubic feet of air and put it into a cylinder the size of a phone booth (remember those?), you would have about 15 PSI (ambient). Now take that same air and shove it into a coke can and the pressure would be tremendous! Your 3300 PSI 80 is just a little smaller than the 3000 PSI 80. I once got to see an experimental Russian titanium 80 that was just a little bigger than a football. Of course, no regular dive shop could fill it. 6000 PSI is my recollection of what it took to fill to 80 cubic feet. Just my $.02 SignatureRay Contreras =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- Webmonkey for: http://www.ossystems.com http://members.aol.com/gaspast http://www.rayzplace.com > If you take 80 cubic feet of air and put it into a cylinder > the size of a phone booth (remember those?), you would have > about 15 PSI (ambient). Now take that same air and shove it > into a coke can and the pressure would be tremendous! Methinks it wold be a liquid! > Your 3300 PSI 80 is just a little smaller than the 3000 PSI > 80. I once got to see an experimental Russian titanium 80 [quoted text clipped - 3 lines] > > Just my $.02 Once again the Metric system proves to be easier to understand, where the cylinder is measured by its true volume, irrelevant of pressure, thus a 15L cylinder has an actual internal volume of 15 Litres. The working pressure is separated, thus the common cylinder sizes in the UK, Europe & most of the world are: 1 or 1.5L (Argon suit inflation), generally only available as 200bar Aluminium. 3L (Pony size) 7L (commonly used for deco gas), or in high pressure steel (300 bar), may be twinned 10L for shallow single cylinder diving or twined up for smaller divers (like my wife's twinset) 12L, the most common size for Single-cylinder and for twinning purposes. 15L Often used for slightly deeper single tank diving and twinned for heavy breathers or deeper (tri-mix) diving. 18 & 20L cylinders are often used for cave diving and the 18L is well known for its excellent buoyancy characteristics. The 3L & 7L is available as either aluminium or steel, but the Aluminium versions are only available in 232bar (approx 3300 psi) The 7L and 12L steel cylinders are available in both 232 and 300bar (330 & 4000 psi) As a comparison of sizes: 3L cylinder at 232 bar is roughly equal to 24 CuFt 10L cylinder at 232 bar is roughly equal to 80 CuFt 12L cylinder at 232 bar is roughly equal to 100 CuFt 15L cylinder at 232 bar is roughly equal to 120 CuFt 7L cylinder at 300 bar is equal to 74CuFt 12L cylinder at 300 bar is roughly equal to 127 CuFt Simple! > Once again the Metric system proves to be easier to understand, where the > cylinder is measured by its true volume, irrelevant of pressure, thus a 15L [quoted text clipped - 29 lines] > > Simple! "Simple" doesn't take a page to explain. "PST 104 cu. feet". Now that's simple. Signature"We're going to rush the hijackers." -Jeremy Glick, aboard United Airlines flight 93, September 11, 2001 |
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