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Scuba Forum / General / July 2006SPGs
I was disassembling my SPG today since it has a crack in the case... I was curious what the threads that it uses are so that I might be able to replace it with a industrial gauge instead of going up to the LDS for one... I figured that it's unlikely that the various dive equipment companies manufacture their own gauges, they probably just have one of the gauge manufacturers put their name on the dial... Anyway, as I was disassembling it, I started examining the piece that screws into the hose and also the body of the gauge... Seems that it has screw threads on the smaller tip and an O-ring on the shaft that fits up inside the gauge housing... This got me to wondering what type of depth rating this sort of mechanism might be rated for... A quick look at various SPG ads on the net didn't show any ratings for any of them... Eventually, I came up with the following link in which at least *that* company specifies that their gauges are rated to 300 ft... http://www.noshok.com/files/pressure_gauges/NOSHOK_Aqua_Series_Pressure_Guages.pdf Knowing that there are those who go deeper than this, I have to wonder if they use a different type of SPG or if they just clean it out if it leaks... >I was disassembling my SPG today since it has a crack in the case... I > was curious what the threads that it uses are so that I might be able [quoted text clipped - 11 lines] > least *that* company specifies that their gauges are rated to 300 > ft... We have it on reasonably good authority (personal experience) that the O ring seal is good to about 3,500 psi, roughly 7,857 fsw. We don't suggest you accompany it to such depths. > Knowing that there are those who go deeper than this, I have to wonder > if they use a different type of SPG or if they just clean it out if it > leaks... At an intermediate pressure of 140 psi, the tank pressure required to get gas from your second stage is equal to ambient pressure at a little over 300 fsw. Anything over that, which I'd hope you have if you're at more than 300 feet, is gravy. For water to leak in, it has to overcome the pressure trying to get out. Not likely. To leak, the gauge would normally have to have a crack in the case, as yours did, and have a non oil filled space inside which, apparently yours also did. It's interesting that you found a depth rating on a SPG. I don't think I've ever seen one. On the other hand, I see depth ratings on air integrated computers regularly. That, however, is usually based on the computer's depth reading/deco calculating ability rather than the case's ability to stand the pressure. Lee > Seems that it > has screw threads on the smaller tip and an O-ring on the shaft that > fits up inside the gauge housing... Are you sure? AFAIK all modern SPGs employ a spool, a small unthreaded cylinder with o-rings on each end. It bridges the gap in the thread mating area. OTOH if it's really old, anything is possible. Its a critical maintenance item since the threaded connection per se is NOT watertight and there is typically water surrounding the spool after every dive. As long as the spool is keeping 3500 PSI in on one side, its a pretty safe bet its keeping the seawater out on the other. > This got me to wondering what type > of depth rating this sort of mechanism might be rated for... Uwatec, and Dive Rite (for two) have solid brass cases with thick crystal bezels, not cheap poly-carbonate like gauges you pointed to. The polycarbonate, along with cheap stamped metal case is the probably the reason for the pressure rating. They will cave, or else distort above 11 ata > http://www.noshok.com/files/pressure_gauges/NOSHOK_Aqua_Series_Pressure_Guages.pdf Uwatec and Dive Rite don't pressure rate theirs, but I'm pretty sure they go a lot deeper than we can. Whether or not $100 (vs 50) for one of these is worth it to you is a matter of taste. My experience is that the cheap ones tend to be more accurate. Note that the gauge housing is NOT (as you surmised) pressurized. The housing and bezel must remain at 1 ata (definitive p.s.i.g. reference) and Only the Bourdon tube sees pressurization. I don't think I'd like to keep a gauge that leaked water. Once you see it, it's probably been wet for a while and the blow out plug might not be the weakest part of the housing anymore. That would be a bad thing if the bourdon tube sprung a leak. Meanwhile If water is getting in, its not maintaining 1 ata internally, so the reading is not correct either, although it will be low. bullhshark > Are you sure? AFAIK all modern SPGs employ a spool, a small unthreaded > cylinder with o-rings on each end. It bridges the gap in the thread [quoted text clipped - 3 lines] > every dive. As long as the spool is keeping 3500 PSI in on one side, > its a pretty safe bet its keeping the seawater out on the other. Oh, I'm *very* sure since I disassembled the gauge... There are two O-rings on the unit... One is for keeping the 3500 psi in the gauge and it is a fairly small diameter O-ring... The other is for keeping water out of the housing and as such, doesn't need to withstand 3500 psi... It has quite a bit larger diameter than the inner O-ring... It doesn't appear to mate to a flat surface, but rather it is in contact with the cylindrical surface of the opening into the housing... > Uwatec, and Dive Rite (for two) have solid brass cases with thick > crystal bezels, not cheap poly-carbonate like gauges you pointed to. > The polycarbonate, along with cheap stamped metal case is the probably > the reason for the pressure rating. They will cave, or else distort > above 11 ata Actually, the unit that I posted has a cast bronze case, not stamped metal... I actually sounds better than a lot of the other ones that I've seen over the years... As far as the polycarbonate lense goes, if they made it thick enough, I suspect that it could easily handle more than 300 ft... > Uwatec and Dive Rite don't pressure rate theirs, but I'm pretty sure > they go a lot deeper than we can. Whether or not $100 (vs 50) for one > of these is worth it to you is a matter of taste. My experience is that > the cheap ones tend to be more accurate. I have no idea what the cost of that gauge might be since they don't post the price on the web site... I sent them an email, but they haven't responded yet... > Note that the gauge housing is NOT (as you surmised) pressurized. The > housing and bezel must remain at 1 ata (definitive p.s.i.g. reference) [quoted text clipped - 5 lines] > ata internally, so the reading is not correct either, although it will > be low. At 150 ft, it would be reading 67 psi low... Probably not enough that you would notice it... As you ascend, the difference would decrease, so one could consider it an additional safety margin... <grin> > Oh, I'm *very* sure since I disassembled the gauge... There are two > O-rings on the unit... I gathered that, but sometimes the spool is corroded itself into on side or the other and won't come out. But I gather you have that in hand...What brand is it? > At 150 ft, it would be reading 67 psi low... Probably not enough that Yeah, but I figured you were going at least twice that deep. I looked again (actually read the specs? Say it ain't so!), and it looks like they are a producer looking for a label. The specs say the scale has "Customer Design". Spool: http://www.diveriteexpress.com/regs/img/rg27aslg.jpg Thats a dive-rite, and it fits all the SPGs I have, even old-broken-water-leaking-polycarbonate-stamped-metal-USD crap from 1984. Diveriteexpress carries and sells them for cheap. It beats the sh.t out of trying to change th O-rings on those little bastidges. Our gear hardly ever gets dry so I replace them about twice a year just to keep it from getting too grungy. My OEM spools did not have the little flange. I don't know what purpose it serves but it doesn't get in the way. Maybe it keeps it from getting too deeply seated on one side or the other? The spools as well as the Dive rite gauge are available "naked" from here: http://www.diveriteexpress.com/regs/spgsonly.shtml bullshark > I gathered that, but sometimes the spool is corroded itself into > on side or the other and won't come out. But I gather you have > that in hand...What brand is it? Dacor... > Yeah, but I figured you were going at least twice that deep. I was just quoting the figures for a typical open water air dive... If I'm going to 300 ft, it's not going to be on air... Anway, the 300 ft figure would just be twice the 150 ft figure... > I looked again (actually read the specs? Say it ain't so!), and it > looks like they are a producer looking for a label. The specs > say the scale has "Customer Design". I suspect that they are like a lot of other things in that they manufacture the item and other companies put their label on it... They appear to make quite a few different types of gauges other than SPGs, so it would seem that they know what they're doing... Hell, it's not rocket science anyway... If you look at the internal workings of an SPG and the typical pressure gauge that goes on your shop air compressor, you'll see basically the same thing... Bourbon tube gauges are relatively simple devices... > Spool: http://www.diveriteexpress.com/regs/img/rg27aslg.jpg > [quoted text clipped - 4 lines] > bastidges. Our gear hardly ever gets dry so I replace them about > twice a year just to keep it from getting too grungy. That's not the piece I was talking aboiut... I have one of those, of course, but it is in the hose... Easy to pull out (other than the fact that my fingers are too large to get a grip on it)... The part that I'm talking about is what the hose end screws into... This piece unscrews from the gauge... It is hollow, of course, so that the gas can get to the bourbon tube from it... One end of the piece has small screw threads that screw into some sort of matching piece inside the gauge and the other end has screw threads that screw into the hose end... There is a shaft that is slightly smaller than the gauge housing and there is an O-ring on this shaft to prevent water from getting into the housing... Here's a photo of the piece... http://i6.tinypic.com/1z56j34.jpg > My OEM spools did not have the little flange. I don't know > what purpose it serves but it doesn't get in the way. Maybe > it keeps it from getting too deeply seated on one side or the > other? From looking at it, I would hazard to guess that it keeps you from losing the spool in the hose... The spool also seems to act as a reducer so that if your gauge blows out, the gas can only escape so fast... Of course, it's also easier to handle high pressure with a small tube than a large tube... > http://i6.tinypic.com/1z56j34.jpg When I had a blowout on the hose to my USD SPG, Jayna walked all over Cozumel before she found a shop that had the right parts to fix it. While I did not know the details at the time, it is my opinion that it was the spool that was the problem. I could be wrong, but her experience fixing my piece of dive equipment, suggests not all spools are, or at least were, standard. Knowing your taste for equipment that is older than you are, I have to suspect that what you're trying to deal with is a similar situation . . . or not. Bullshark tends towards more modern equipment, which may be why the spools he's familiar with seem to be more universal. Having said that, I'll now back out of a conversation that I don't know enough to remain active in. Lee > When I had a blowout on the hose to my USD SPG, Jayna walked all over > Cozumel before she found a shop that had the right parts to fix it. While I > did not know the details at the time, it is my opinion that it was the spool > that was the problem. The only HP related problem that I ever had was with a hose that had a bubble in it... I was still able to continue the dive and I had a spare one back at the hotel... I spent a couple of days in Coz trying to find a replacement also... > Knowing your taste for equipment that is older than you are, I have to > suspect that what you're trying to deal with is a similar situation . . . or > not. Although I would like to own and have a chance to dive a Mk-V, the equipment that I do own and dive is definitely not as old as I am... Some of it (i.e. my tanks) are older than many of the people on the dive boats though... All in all, I do like the classics though... Big honkin' pieces of steel and brass... None of this plastic crap that you see these days... > Although I would like to own and have a chance to dive a Mk-V, the > equipment that I do own and dive is definitely not as old as I am... Stay away from the Mk V, it's a horrible rig. Go for a Siebe Gorman 12 bolt commercial or, if you can afford it, a Lerios sponger. m > Stay away from the Mk V, it's a horrible rig. Go for a Siebe > Gorman 12 bolt commercial or, if you can afford it, a Lerios > sponger. I'm ex-Navy, so of course it would *have* to be a Navy Mk-V... >> http://i6.tinypic.com/1z56j34.jpg > [quoted text clipped - 5 lines] > I could be wrong, but her experience fixing my piece of dive equipment, > suggests not all spools are, or at least were, standard. I keep two styles in the Magic Bag. > Knowing your taste for equipment that is older than you are, I have to > suspect that what you're trying to deal with is a similar situation . . . [quoted text clipped - 3 lines] > he's familiar with seem to be more universal. Having said that, I'll now > back out of a conversation that I don't know enough to remain active in.  SignaturePopeye "Best thing for him, really, his therapy was going nowhere." -Dr. Hannibal Lector. www.finalprotectivefire.com > I could be wrong, but her experience fixing my piece of dive equipment, > suggests not all spools are, or at least were, standard. About 80% are the same, but the other 20% use a dozen different spools. m I've seen three basic spools, the one with the flange is generally on European gauges (Mares, Beuchot and Scubapro) the other two spools are similar and in most cases interchangeable). The spools use #3 o-rings. Timothy Ewing >> I could be wrong, but her experience fixing my piece of dive >> equipment, suggests not all spools are, or at least were, standard. > > About 80% are the same, but the other 20% use a dozen different spools. > > m SignatureCaptain of the Kilauea Volcano Jumpers The Big Islands Firediving Team http://www.firediving.com > I've seen three basic spools, the one with the flange is generally on > European gauges (Mares, Beuchot and Scubapro) the other two spools are > similar and in most cases interchangeable). The spools use #3 o-rings. Disassembly of my gauge had a "Made in Germany" stamp on the back of the dial... Although the dial face has 'Dacor' on it, it also has 'TAG' in small capital letters... I suspect that Dacor and many of the other dive equipment companies don't design and make their own SPGs... Maybe they just design the housing and use stock pressure gauge movements from other manufacturers... That would be simple enough to do... >> I've seen three basic spools, the one with the flange is generally on >> European gauges (Mares, Beuchot and Scubapro) the other two spools are [quoted text clipped - 7 lines] > movements from other manufacturers... That would be simple enough to > do... I'll be home later today, and see if I can find that Dacor guage. It has the same part you posted a photo of. SignaturePopeye "Best thing for him, really, his therapy was going nowhere." -Dr. Hannibal Lector. www.finalprotectivefire.com > I've seen three basic spools, the one with the flange is generally on > European gauges (Mares, Beuchot and Scubapro) the other two spools are > similar and in most cases interchangeable). The spools use #3 o-rings. What counts is the spool diameter at the o-ring seat. The flange and other details are stylistic concerns. The controlling factor is your HP Hose which AFAIK has been unchanged in nature since I started diving in 1984 (actually, I started in '79 but I didn't buy any equipment until '84). The size of the receiver orifice is the same in all my HP Hoses, or at least close enough to not matter. For reasons I don't understand, I keep useless hoses. I have a whole room full of them... The little flanged spool diverite sells fits every HP hose I have, and works for every SPG I have: miniature SP 2000 Swiss Uwatec 2000 Italian DiveRite 2005 ??? USD 1984 ??? Oceanic 1990 I have older spools that are bullet shaped on the end I have older spools that are cut square on the end I have older spools that are shorter I have older spools that are longer The part appears to be a universal replacement. I didn't think so at first, but at $3 apiece (I think they're less in person) they barely cost more than o-rings, which are a PITA to acquire, and even harder to change. So I got a few, tried them out, and they worked everywhere. Short of the long: Universal HP Hose takes universal spool. bullshark > > Yeah, but I figured you were going at least twice that deep. > > I was just quoting the figures for a typical open water air dive... Just kidding anyway. > That's not the piece I was talking aboiut... I have one of those, of > http://i6.tinypic.com/1z56j34.jpg I went and dug through my junk box and found an old broken USD, and it has exactly the same part. Basically just holding the Bourdon tube meachanism in place. The "good gauges" don't have it, so that may add significantly to their depth rating. > The spool also seems to act as a reducer so that if your gauge blows out, the gas > > can only escape so fast... I think it would blow out like a bullet. All my HP hoses have pin hole reducers cast in place anyway. You should see it when you unscrew the HP hose from the reg. The Uwatec gauge (US version) runs to 0-6000 psig. I can't remember who, but someone (Gray?) was looking for a higher capacity gauge a while back. Anyway, for my money the higher end gauges are worth it, even if they don't last long. They're the most important instrument in my rig, and even at $100, thats chicken feed compared to actually getting on a boat and diving (c: The dive rite, at 72 is a pretty good deal. Especially because you can buy the raw gauge. I hate paying for another HP hose and boot that I don't want when all I need is a gauge. bullshark TEST >TEST result: F- has anyone given you the rec.scuba welcome yet? > <capt.bill11REMOVETHIS@verizon.net> wrote: > has anyone given you the rec.scuba welcome yet? Capt. Bill is not new to the group. He just hasn't posted much lately. >> <capt.bill11REMOVETHIS@verizon.net> wrote: > >> has anyone given you the rec.scuba welcome yet? > >Capt. Bill is not new to the group. He just hasn't posted much lately. My bad then... In my experience TEST normally means "I'm a total Newsgroup newbie, is Outlook working?" > >> <capt.bill11REMOVETHIS@verizon.net> wrote: > > [quoted text clipped - 7 lines] > > "I'm a total Newsgroup newbie, is Outlook working?" He's running Forte. > TEST When starting a new thread please start from scratch. When you change the subject lime without removing the existing references your new thread is displayed in the midst of the existing thread Thanks John >TEST misc.test unmunge your address and you'll get dozens of emails from around the world telling you they've seen it. As far as spam is concerned. the average email address will stay spam free for between 3 and 6 months. Those mothers are nasty. Signaturedillon JAFO |
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