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Scuba Forum / General / November 2003Piston or Diaphram
i am sure this has been asked 1000 times before, but is there any practical different (in use, realiability, cold water etc) been a balanced piston reg, and a balance diaphram or is it just two different ways to get to the same result? Does one perform better than another? > i am sure this has been asked 1000 times before, but is there any practical > different (in use, realiability, cold water etc) been a balanced piston reg, > and a > balance diaphram or is it just two different ways to get to the same result? > > Does one perform better than another? practicly speaking the only difference is that it's easier to seal a diapham reg for cold water / ??? ( damn it's too early in the morning - i'm drawing a blank on the word for "dirty" water ) > > i am sure this has been asked 1000 times before, but is there any practical > > different (in use, realiability, cold water etc) been a balanced piston reg, [quoted text clipped - 6 lines] > diapham reg for cold water / ??? ( damn it's too early in the morning - > i'm drawing a blank on the word for "dirty" water ) turbid perhaps? > > > i am sure this has been asked 1000 times before, but is there any > practical [quoted text clipped - 11 lines] > > turbid perhaps? or maybe just murky? snip >> two different ways to get to the same >> result? [quoted text clipped - 8 lines] > >or maybe just murky? Polluted or contaminated?? I dive in both,,,,, FFM and positive pressure. Disinfected afterwards.:-( -- Steve Barlow > snip > >> two different ways to get to the same [quoted text clipped - 13 lines] > I dive in both,,,,, FFM and positive pressure. > Disinfected afterwards.:-( Ummm, it's better to have dove in contaminated water than to never have dove at all? :-) > -- > Steve Barlow Big diffrence. Piston fails open (you get air) Diaphram (if it splits / cracks) you get nadda. Gue types seem to miss this. Piston dosen't like cold water, with the exception of. Sherwood (#1 in USN / UK / France cold water test for years) Scubapro seems to do ok in cold water as well I have never seen the USN test results on Scubapro. This basic 101 T > Big diffrence. > [quoted text clipped - 3 lines] > > Gue types seem to miss this. How would a piston "fail"? And why would it necessarily fail open? And if a diaphragm splits or cracks, which would require the application of a hatchet or similar tool in a very confined space, you simply lose a lot of air through the ambient chamber. There's still plenty to breathe. Making a modern reg fail is very very difficult. "mike gray, CID" <mikegrayCID@worldnut.nut> wrote in message news:SGgub.78028$Ec1.4057031@bgtnsc05- > How would a piston "fail"? And why would it necessarily fail open? Steve doesn't know the answers. Hell, he doesn't even know the questions. You are right Mike, a daiphragm reg with a cracked/split or even unseated diaphragm will just leak a lot of air but it's still breathable. I've done it before myself. And a piston reg isn't automatically "fail-safe" as I've had a piston reg fail shut before also (luckily, on the surface). Cheers David M >breathable. I've done it before myself. And a piston reg isn't >automatically "fail-safe" as I've had a piston reg fail shut before >also (luckily, on the surface). > >Cheers >David M Interesting, what brand? What was the internal problem? T > Interesting, what brand? > What was the internal problem? It was a rebadged cheapo brand that's popular in WA (Australia) called (ironically) "Performance". It's basically a scubapro ripoff. I didn't take it apart (didn't have the spanner to get the end cap off), but I believe it mught have been the piston o-ring had not been lubricated or something like that. The distributor took it away and returned it all fixed, saying there was "nothing wrong with it". Needless to say it's been living in a junk box since. Cheers David M >> Interesting, what brand? >> What was the internal problem? [quoted text clipped - 9 lines] >Cheers >David M Assuming you dive where you live, you lucky bastard :). Warm salt water and sun shine has to be the harshest on dive gear. Ok other than dragging your gear along the bottom whether it be coral or zebra mussels. I have seen warm salt water take the finish off those new fancy black light weight regs (Scubapro) My guess is salt crystallized in the piston chamber. The best reg for warm salt water is Sherwood, no ambient water enters the piston chamber and it doesn't need a lot of rising. There's only two manufactures that seem to get the piston thing right. Sherwood Scubapro Toto On Tue, 18 Nov 2003 03:51:14 GMT, "mike gray, CID" >How would a piston "fail"? And why would it necessarily fail open? > [quoted text clipped - 3 lines] > >Making a modern reg fail is very very difficult. True, but diaphragms do crack that's why they are included in overhaul kits. Whether it be bad batch or excessive cold or excessive use or high O2. Pistons tend to stick open generally the cause is the "O" ring around the sealing surface on the piston. Either dries out and sticks or crap gets in the chamber or a small cut allows air to by pass therefore not allowing the seating the piston in the off position. You need the hp side to seat the piston. Scubapro allows ambient water in the piston chamber which can hasten these problems. Sherwood dosen't instead it uses a dry bleed system (see their web site) Basically a controlled by pass of the hp side to the lp side of the seat through the piston's outer edge. The Sherwood has air on both sides of the piston. Scubapro has air on one side and ambient water on the other. Which to a fresh water wreck diver, could be a problem. Rust seems to get into the damest places. Scubapro does make one diaphram reg, I believe it is the MK 16. Which is about the only reg of their's I would be interested in. I never dive a diaphragm by it self. I use a Sherwood if I'm diving single reg. In the pass I have had problems with cold (slush) water dives. I have seen every reg under the sun fail in these conditions, but not the Sherwoods. The USN test back this up and until? 95 was the world standards for most navies extreme cold water reg. T > True, but diaphragms do crack that's why they are included in overhaul > kits. As a part that is continually flexing, that's not a bad idea. > Whether it be bad batch or excessive cold or excessive use or high O2. > Pistons tend to stick open generally the cause is the "O" ring around [quoted text clipped - 3 lines] > the off position. > You need the hp side to seat the piston. Or the spring breaks, or some a.shole drops his tank on your rig and deforms the piston or cylinder, or lightning hits it and fuses the piston to the housing, or.... There's a thousand things that can go wrong, the fact is that very few divers will ever see any of them happen. > Scubapro allows ambient water in the piston chamber which can hasten > these problems. (snip) In cold water diving (about which I know absolutely nothing)I suppose that could be a concern. As for rust, salt, foreign bodies getting in there, the concern is over-rated. And isn't that the same stuff that gets inside the ambient chamber of a diaphragm reg causing the diaphragm to crack, tear, dissolve, explode, or whatever? I don't disagree with any of the hypothetical piston vs. diaphragm stuff, just keep it in perspective - it's mostly marketing hype. > > True, but diaphragms do crack that's why they are included in overhaul > > kits. <cough> > As a part that is continually flexing, that's not a bad idea. Just don't use rubber, as Chico Escuela said; "Rubba Break." >> > True, but diaphragms do crack that's why they are included in overhaul >> > kits. [quoted text clipped - 4 lines] > >Just don't use rubber, as Chico Escuela said; "Rubba Break." I wonder want they are made of some look like rubber with string through it. So look like silicon. One manufacture brought out a new diaphragm reg with a silicon diaphragm. Between the refrigeration effect across the hp seat and the cold ambient water temperature. These diaphragms became so stiff, they wouldn't work. Seems 42 F water and 130 ft was the magic combination. There was never a recall, but the shops with a consciences called the regs back in for a free overhaul. The supplier gave out overhaul kits for free all the shop had to do was return the old parts. There was a world of difference in the quantity of the overhaul parts. The diaphragm was even colored blue so you couldn’t mistake for the older clear one. This was a sport reg so this should have been a non issue. This problem didn’t surface until they started selling them in colder areas. T srspencer@hotmail.com schrieb: > >> > True, but diaphragms do crack that's why they are included in overhaul > >> > kits. [quoted text clipped - 11 lines] > One manufacture brought out a new diaphragm reg with a silicon > diaphragm. Old Poseidon and Draegers have "rubber" diaphragms reinforced with fabric, or not. Newer Poseidons have a clear stuff, pretty hard, ,may be silicone, cuase this is most indifferent to temperature changes. I'd prefer the old rubber ones, though, because these work as a better seal between water and the regs innermost parts. You can see the difference when you service the regs, the rubber ruled ones are cleaner. ( except those regs from the Navy.... but these use them often as drysuit gas regs with an extra bottle, may be they just don't care when the bottle runs empty) A lifetime of 7 to 15 years is not unusual for the rubebr membranes. I have seen only one gone south ( still working, though, but with heavy indentions from the spring), but more of the hard silicone ones which showed tiny cracks. Matthias >In cold water diving (about which I know absolutely nothing)I suppose >that could be a concern. As for rust, salt, foreign bodies getting in [quoted text clipped - 4 lines] >I don't disagree with any of the hypothetical piston vs. diaphragm >stuff, just keep it in perspective - it's mostly marketing hype. The holes in the Scubapro are about 1/8 ". The hole in most diagram is 1/4 " or bigger then some have the hole covered and pressure is transmitted through it. Rusting getting next to the diaphragm as long as it doesn't effect the spring no big deal. Rust getting on the piston wall and nicking the o ring traveling up and down the wall is a problem. Wreck diving on steel wrecks, rust is a concern. Whether it's cutting holes in dry suits, mucking up the vis or working it's way into your reg. I would agree hype is the bigger problem. T > snip > [quoted text clipped - 12 lines] > > Polluted or contaminated?? ^^^^^^^^^^^^ that'll do!!!! man i hate early mornin brain lock. > I dive in both,,,,, FFM and positive pressure. > Disinfected afterwards.:-( > > -- > Steve Barlow mark wrote: > Does one perform better than another? You building an engine, or trying to avoid getting pregnant? JC > i am sure this has been asked 1000 times before, but is there any practical > different (in use, realiability, cold water etc) been a balanced piston > reg, and a balance diaphram or is it just two different ways to get to the > same result? > > Does one perform better than another? Define performance. Your question is like asking which is better, a Ford or a GM. In terms of "can I notice a difference in ease of breathability between a balanced piston vs a balanced diaphragm" the answer would be NO. Why? Because the 1st stages' job is to reduce high pressure gas to a workable intermediate pressure (IP), and an intermediate pressure is an intermediate pressure. Recovery or consistency to maintain a desired IP depends upon the flow rate of the 1st stage. A standard piston design has a flow rate in the range of 180 cf/min. Diaphragm 1st stages range from 200 cfm ~ 240 cfm. A high performance piston design can have a flow rate in excess of 600 cfm. In terms of maintenance, diaphragm regs generally have far more working parts. Both piston and diaphragm regs can be environmentally sealed. All diaphragm regulators as well as some piston designs have easy user adjustable IP settings (standard piston designs are not "user" changeable). Understanding what features are available (such as ability to enviro seal, high flow rate, user adjustable IP settings and so on) and what the pros and cons of each are may be more helpful to you. I'd suggest one first find the features that are important to them, then shop for a solution. -- Randy F. Milak ~The advantage of exercising every day is that you die healthier!~ > > i am sure this has been asked 1000 times before, but is there any > > practical different (in use, realiability, cold water etc) been a > > balanced piston reg, and a balance diaphram or is it just two different > > ways to get to the same result? > > > > Does one perform better than another? > ... > Understanding what features are available (such as ability to enviro seal, > high flow rate, user adjustable IP settings and so on) and what the pros > and cons of each are may be more helpful to you. I'd suggest one first > find the features that are important to them, then shop for a solution. Some food for thought about features and considerations of reg purchases with respect to piston vs diaphragm... The function of a 1st stage regulator is simply to lower the high pressure gas from the SCUBA cylinder to a lower, deliverable intermediate pressure for 2nd stage regulator operation. There are two basic 1st stage regulator designs. A diaphragm design and a piston design. We'll examine both, but examination can not be properly made without consideration of the 2nd stage that is going to be mated to it. The job of the 2nd stage regulator is simply to deliver ambient pressure gas to the diver via the 1st stage. There are two basic 2nd stage regulator designs. An upstream valve 2nd stage and a downstream valve 2nd stage. Basically, when an upstream 2nd stage regulator functions as designed, the valve is closed by default and must be 'working' in order to deliver gas to the diver. By contrast, when a downstream valve 2nd stage regulator functions as designed, the valve is open by default and must be 'working' in order to shut off gas to the diver. If the regulator malfunctions, it will simply free flow. That's why downstream regulators are referred to as 'fail safe'. Regardless of whether the 2nd stage is an upstream or a downstream design 2nd stage, the higher the 1st stage's intermediate pressure (IP) is set, the better or easier the 2nd stage will breath (or perform). Usual IP range is 125 psi to 150 psi for downstream 2nd stage and 175+ psi for an upstream 2nd stage. With respect to a downstream 2nd stage regulator, the caveat to a higher IP setting, is that the higher the IP is set, the more susceptible the 2nd stage regulator is to free flow and a higher probability of 1st stage 'freeze up'. Therefore, generally speaking: High IP = better (easier) breathing 2nd stage, faster IP recovery. High IP = higher probability of 2nd stage free flow in colder water. High IP = higher probability of 1st stage 'freeze up' in colder water. Lower IP = poorer 2nd stage breathing. Lower IP = less probability of 2nd stage free flow. Lower IP = less probability of 1st stage 'freeze up'. User adjustable IP settings may be advantageous to the diver whom may have occasion to sacrifice performance of breathing to lower risk of 2nd stage 'free flow' and/or 1st stage 'freeze up' such as an ice diving situation etc. The latter situation is made moot where a high performance 2nd stage regulator that utilizes a balance chamber design for the poppet assembly seating to the gas inlet orifice is employed. In which case, it won't matter what the IP setting is, simply because the cracking pressure (amount of vacuum) required to open said valve will remain constant (because it is balanced) regardless of IP allowing the regulator to perform at 'peek' even under lower IP conditions. Therefore, a high performance 2nd stage regulator that incorporates a balanced poppet assembly would be extremely advantageous to the diver diving colder water simply because no performance is lost if the diver chooses to lower (or keep low) the IP to prevent 1st stage freeze up (we'll discuss what 1st stage "freeze up" is in a moment). Even with a high performance 2nd stage that utilizes a balanced poppet chamber, consider that the higher the IP setting, the faster the gas will flow through the 1st stage (during recovery from each breath). The higher the gas flow rate is through the 1st stage, the faster that flowing gas will take the 'heat' from the 1st stage regulator. The colder the 1st stage gets, the more susceptible it is to "freeze up". Consider that a brass 1st stage can and will hold far more heat energy for longer periods than any given titanium 1st stage, making titanium 1st stages a less desirable choice for cold water diving. 1st stage regulator "freeze up" refers specifically to ice forming on the intermediate bias spring which regulates the IP. If ice forms on the bias spring, the bias spring will fail to operate as designed (because ice is preventing the spring from compressing and decompressing properly or even entirely). For a diaphragm design, the IP bias spring is far more encapsulated than any piston design (meaning water can not easily flow in and out of the ambient balance chamber, making that ambient balance chamber essentially a refrigerator), which contrary to popular belief, therefore makes all diaphragm designs more susceptible to "freeze up" than any piston design. Diaphragm 1st stage manufacturers therefore utilize "enviro sealing" to combat the potential problem. Some enviro seals are 'wet sealed' such as that found in the Poseidon Jetstream 1st stage or 'dry sealed' such as that found in certain APEX and Dive Rite 1st stages. The 1st stage 'freeze up' problem is then solved for a diaphragm regulator providing it is 'enviro sealed'. Therefore, a diaphragm 1st stage regulator that is not enviro sealed would be a less desirable, if not a bad choice for cold water diving. Piston design although less susceptible to "freeze up" than a basic diaphragm design because the balance chamber of a piston reg cannot easily hold stagnate water within it's ambient chamber space, can still freeze up the IP bias spring. With respect to piston design though, manufacturers have far more options than simply environmentally sealing the first stage. For example, bias springs can be/are teflon coated so that ice can not form on the spring in the first place. Thermo shims are used to isolate the bias spring from all other metal parts. It specifically prevents thermal bridging of the bias spring from the reg body which inevitably can lead to 'freeze up'. Therefore, any piston 1st stage design that does not incorporate some type of anti-freeze component(s) would be a less desirable, if not a bad choice for cold water diving. If one does not want the risk of 2nd stage regulator free flow in cold water, one should not purchase a downstream regulator. It's that simple. Otherwise, all downstream regulators are susceptible to 'free flow'. It's a part of the inherent design which is both a safety feature as well as a design flaw. Lowering IPs can help a great deal as well as proper diver breathing technique and so on. Most reg manufacturers nowadays are making the seating orifice from delrin or some other type of nylon (as opposed to metal in which ice can easily form and stick to) that won't allow for the formation of ice on its knife edge sealing surface. However, an already formed ice crystal can still prevent closure of the seat causing free flow in any downstream 2nd stage. Pilot valves such as those employed for use in an upstream valve are not susceptible to ice crystallization problems. An upstream valve requires a high (175 psi or more) IP to maintain satisfactory breathing performance however. With respect to free flows and higher IP settings for upstream valves, its not a consideration simply because upstream regulators can not free flow. When the diver is not inhaling, air at IP flows through the main valve poppet assembly and into the pilot chamber, actually pressing against the main poppet, keeping it in the closed position. However, the higher IP will make the 1st stage far more susceptible to 'freeze up' and therefore, enviro sealing the the 1st stage becomes almost mandatory for any 1st stage employed for use with an upstream 2nd stage used in colder water. Standard piston design regulators are by far the least expensive 1st stages on the market. They are the simplest and easiest to maintain. However, they are the poorest performers with respect to flow rate; do not incorporate user changeable IPs and can have a moderate to high probability of "freeze up" where no anti-freeze components are employed (to keep costs low of course). Standard piston designs are not a very good choice on so many levels, except where cost is a concern. Diaphragm regs run the price gamete from low, med. to high. Non enviro sealed diaphragm regs are usually the least expensive in the diaphragm market but are potentially the biggest POS and run the highest probability of "freeze up". All diaphragm 1st stages employ user adjustable IPs. EVERY diaphragm 1st stage on the market regardless of manufacturer, are essentially the same. The latter makes them easy to service and maintain as well, considering, if you know how one works, you know how they all work. Enviro sealed diaphragm regs have a decent flow rate and can be an all around good choice for the cold water diver in the moderate to high end price range. High performance piston regulators are in the higher price range only. They are by far the best flow performance regulators on the market. Without some type of anti-freeze componete(s) they run a moderately high probability of 'freeze up' due to the high flow rate inherently characteristic of high performance piston 1st stages. High performance piston regs which employ anti-freeze components have the best flow rate and therefore best performance, and can be an all around good choice for the cold water diver where price in not a concern. When choosing a regulator, also consider if the diver wish's a DIN or yoke connection and how that may affect a streamlined configuration for the 1st stage(s) in question. Consider the number of high and low pressure ports required for your application, where each is located, and whether the 1st stage employs a LP port swivel which lends towards a streamlined configuration and so on. The diver must consider gear maintenance to be a high priority. All the gear in the world will not help if it does not work. Warranty time; ease of service both locally and worldwide etc. are all important features. Most 2nd stages have a definitive right side 'up' and wrong side 'down' to them, whereas side exhaust regulators for example do not -- is it even a concern and so on? The ability to fix (i.e. tighten, adjust, free and clear etc.) a 2nd stage underwater may be an important consideration for the type of diving one may pursue. Therefore, how easy is it to remove the diaphragm cover and/or exhaust diaphragm cover underwater in order to clear out a possible obstruction and so on? Keep in mind, with respect to life support equipment, one usually gets what one pays for. Just some food for thought, YMMV. -- Randy F. Milak ~The only perfect science is hindsight!~ "Randy F. Milak" schrieb: That's why downstream > regulators are referred to as 'fail safe'. Except when they sit in a rebreather delivering oxygen. You do not wan't them freeflowing then into the loop. > Regardless of whether the 2nd stage is an upstream or a downstream design 2nd > stage, the higher the 1st stage's intermediate pressure (IP) is set, the better or > easier the 2nd stage will breath (or perform). Only when the snd stage is downstream, or upstream _and_ pneumatically balanced. > With respect to a downstream 2nd stage regulator, the caveat to a higher > IP setting, is that the higher the IP is set, the more susceptible the 2nd stage > regulator is to free flow and a higher probability of 1st stage 'freeze up'. Rather not. There are much more determinants to this, like bottle pressure, and pressure drop in the first stage. The higher the pressure drop, the more susceptibility, theoretically. What you probably refer to, is, that the higher gas velocity in a high iP first stage might cause water molecules to drop of their vapor phase when they hit a restriction, and thus cause freezing. It is really more a design factor. > Therefore, generally speaking: > High IP = better (easier) breathing 2nd stage, faster IP recovery. This is far more due to how the reg is 2balanced pneumatically. For instance, old dräeger regs had an IP of 4.5 to 6.5, and an amazingly fast recovery time, at least on my test bench. > High IP = higher probability of 2nd stage free flow in colder water. > High IP = higher probability of 1st stage 'freeze up' in colder water. The regs name is far more important ;-), if it begins with Scuba... watch out.. > spring from compressing and decompressing properly or even entirely). For a > diaphragm design, the IP bias spring is far more encapsulated than any piston > design (meaning water can not easily flow in and out of the ambient balance > chamber, making that ambient balance chamber essentially a refrigerator), which > contrary to popular belief, therefore makes all diaphragm designs more susceptible > to "freeze up" than any piston design. This may be new to the designers ;-). However, I smile at Scubapros frantic efforts to invent every other year new soon frustrating methods of keeping their regs from freezing. Have you ever seen the new poseidon first stage ? The spring cover basically consists of holes. The frige action you allude to is a simple question of how many holes are drilled into the spring chamber, not the principle of operation. Diaphragm 1st stage manufacturers > 'enviro sealed'. Therefore, a diaphragm 1st stage regulator that is not enviro > sealed would be a less desirable, if not a bad choice for cold water diving. Most diaphragm types are better without seal than any piston types. Nearly all cold water regs in cold Europe are diaphragm types, like Beuchat, Apeks, Poseidon, Mares, Divex. > spring. With respect to piston design though, manufacturers have far more options Better call it crutches, IMHO. > than simply environmentally sealing the first stage. For example, bias springs > can be/are teflon coated so that ice can not form on the spring in the first [quoted text clipped - 3 lines] > design that does not incorporate some type of anti-freeze component(s) would be a > less desirable, if not a bad choice for cold water diving. > If one does not want the risk of 2nd stage regulator free flow in cold > water, one should not purchase a downstream regulator. It's that simple. > Otherwise, all downstream regulators are susceptible to 'free flow'. It's a part > of the inherent design which is both a safety feature as well as a design flaw. Look at the Draeger Shark 2nd stage for a minute. Upstream, pneumatically balanced, when an undue rise of IP occurs, the OPV lets the gas escape... into the snd stage, you can breath it. Not much different from a downstream reg, n'est-ce pas ? > Lowering IPs can help a great deal as well as proper diver breathing technique and > so on. Most reg manufacturers nowadays are making the seating orifice from delrin > or some other type of nylon (as opposed to metal in which ice can easily form and > stick to) that won't allow for the formation of ice on its knife edge sealing > surface. It helps tremendously selling spare ones, too. > Standard piston design regulators are by far the least expensive 1st stages on > the market. They are the simplest and easiest to maintain. I always wondered why they discontinued the $pro all brass MK2. > Diaphragm regs run the price gamete from low, med. to high. Non enviro sealed > diaphragm regs are usually the least expensive in the diaphragm market but are > potentially the biggest POS and run the highest probability of "freeze up". 40 years of poseidon cyklon 300 tells a different story... All > diaphragm 1st stages employ user adjustable IPs. EVERY diaphragm 1st stage on the > market regardless of manufacturer, are essentially the same. Sorry, there are balanced ones, and unbalanced ones, too. The latter makes > them easy to service and maintain as well, considering, if you know how one works, > you know how they all work. Enviro sealed diaphragm regs have a decent flow rate > and can be an all around good choice for the cold water diver in the moderate to > high end price range. I believe it depends more on the design itself than wether you put the cap on... > High performance piston regulators are in the higher price range only. They are > by far the best flow performance regulators on the market. Ahemm, IMHO the Poseidon Extreme is the best performer in the market. Performance, btw, is something I judge in practice, not on the test bench. Most of Scubapros breathtaking delivery rates are faked, in that that they are driven by different supply gas than you would assume in normal SCUBA, and this in pulse mode, calculated to fake constant flow. Just my 2 Euro-CC Matthias > "Randy F. Milak" schrieb: > > Regardless of whether the 2nd stage is an upstream or a downstream design > > 2nd stage, the higher the 1st stage's intermediate pressure (IP) is set, > > the better or easier the 2nd stage will breath (or perform). > > Only when the snd stage is downstream, or upstream _and_ pneumatically > balanced. The higher the 1st stage's IP is set, the better or easier the 2nd stage will breath. EXCEPT in the case of a pneumatically balanced 2nd stage, which was already addressed. High or low IP makes no difference to the performance of any 2nd stage that is pneumatically balanced. > > With respect to a downstream 2nd stage regulator, the caveat to a higher > > IP setting, is that the higher the IP is set, the more susceptible the [quoted text clipped - 3 lines] > Rather not. There are much more determinants to this, like bottle > pressure, Cylinder pressure has absolutely nothing to do with any 2nd stage failure nor with a 1st stage 'freeze up'. However, if someone has some evidentiary to the contrary perhaps they could share it? > and pressure drop in the first stage. Yes, as it relates to gas velocity and it's cooling effect upon the 1st stage. > The higher the pressure drop, the more susceptibility, theoretically. IP pressure drop... That's what I said. > What you probably refer to, is, that the higher gas velocity in a high > iP first stage might cause water molecules to drop of their vapor phase > when they hit a restriction, and thus cause freezing. It is really more > a design factor. Negative, it has nothing to do with the internal components of a 1st stage whatsoever nor does it have to do with achieving the gas's dew point. The latter referenced failure point is a cold water problem, specifically fresh cold water where the water temperature is already near freezing (i.e. <5C / <40F) in the colder months or at depth year round (i.e. below 30mfw / 100ffw) and where the water turns to ice at 0C/32F. Salt water freezes at around -18 or so, making this much less problematic in salt water. However, the latter would also hold true for salt water providing the salt water temp was only a few degrees from its' freezing point as well. High gas velocity through a 1st stage causes the entire 1st stage to become very cold. The 'cold' affects only 1 part, that being the bias spring. When the bias spring becomes cold enough, ice WILL form on the spring and build up. Why? Because the water is only a few degrees from its' freezing point as it is, and the gas velocity only needs to cool the 1st stage by a few degrees. When enough ice has formed on that spring, the 1st stage will fail to operate as designed because it's compression characteristics have been hampered by the ice buildup. > This may be new to the designers ;-). However, I smile at Scubapros > frantic efforts to invent every other year new soon frustrating methods > of keeping their regs from freezing. > > Have you ever seen the new poseidon first stage ? Yes. > The spring cover basically consists of holes. They are not holes but I understand what yer saying, it's wide open and it's a very good design. I'd suggest that Poseidon's design enhancement is something most diaphragm manufacturers have missed the boat on. > The frige action you allude to is a simple > question of how many holes are drilled into the spring chamber, not the > principle of operation. No. Once again, fast moving gas will essentially "refrigerate" the 1st stage. Stagnant water held in a poorly drainable ambient chamber only makes the ice form faster, however one can never eliminate the problem unless one seals the bias spring from contact with the cold water. > Look at the Draeger Shark 2nd stage for a minute. Upstream, > pneumatically balanced, when an undue rise of IP occurs, the OPV lets > the gas escape... into the snd stage, you can breath it. Not much > different from a downstream reg, n'est-ce pas ? It only behaves the same under conditions where the 1st stage fails to seat, and the IP rises. In which case a downstream reg will simply free flow, whereas the other "bleeds" gas off into reg. I wouldn't call that the same. Now, consider a 2nd stage failure. When a downstream reg fails, it simply freeflows. When an upstream 2nd stage fails it does what?... Not much, exactly. > > Most reg manufacturers nowadays are making the seating orifice from > > delrin or some other type of nylon (as opposed to metal in which ice can > > easily form and stick to) that won't allow for the formation of ice on > > its knife edge sealing surface. > > It helps tremendously selling spare ones, too. Agreed. Obviously a nylon orifice cannot sustain a knife edge for anywhere near as long as a stainless steel one. But, it does prevent ice formation. :) > > Diaphragm regs run the price gamete from low, med. to high. Non enviro > > sealed diaphragm regs are usually the least expensive in the diaphragm > > market but are potentially the biggest POS and run the highest > > > > probability of "freeze up". > > 40 years of poseidon cyklon 300 tells a different story... That is not only anecdotal but you demonstrate a definite non-objective bias. > > All diaphragm 1st stages employ user adjustable IPs. EVERY diaphragm 1st > > stage on the market regardless of manufacturer, are essentially the same. > > Sorry, there are balanced ones, and unbalanced ones, too. Don't be sorry, only a dipshit who would purchase a non balanced first stage should be sorry. But you are correct with respect to adjustable IPs, and that's the problem with making generalized statements such as I've done; there're hard to defend. However, other than say Kirby Morgan, who even makes a non-balanced SCUBA 1st stage for the recreational dive market in this day and age? > > High performance piston regulators are in the higher price range only. > > They are by far the best flow performance regulators on the market. > > Ahemm, IMHO the Poseidon Extreme is the best performer in the market. > Performance, btw, is something I judge in practice, not on the test > bench. That is your opinion and it's valued. However, I'd suggest that test bench results are a little less biased than either you or I. :) I'll say this though, for icy diving there's probably no better reg on the planet than a sealed Jetstream with an Xstream and/or Odin. Those shower head regs, although not the best breathers to say the least, rarely fail nor will they ever free flow. Big bonus! :) > Just my 2 Euro-CC Just my 2 Cold Canadian Pesos imported under the Free Trade Agreement from the U.S.. -- Randy F. Milak ~And your crybaby whiny-assed opinion would be...?~ "Randy F. Milak" schrieb: > > > 2nd stage, the higher the 1st stage's intermediate pressure (IP) is set, > > > the better or easier the 2nd stage will breath (or perform). [quoted text clipped - 6 lines] > already addressed. High or low IP makes no difference to the performance of any > 2nd stage that is pneumatically balanced. Would you agree that it does make a difference to the cracking resistance of an unbalanced upstream 2nd stage ? > Cylinder pressure has absolutely nothing to do with any 2nd stage failure > nor with a 1st stage 'freeze up'. However, if someone has some evidentiary to the > contrary perhaps they could share it? Well, it's part of the physical properties of the gas breathed. Van de Waal coefficcients etc. These predict that the "temperature drop" due to Joule-tomphson effect, when breathing air, is maximum with a bottle pressure of 160-170 bar. > > What you probably refer to, is, that the higher gas velocity in a high > > iP first stage might cause water molecules to drop of their vapor phase [quoted text clipped - 3 lines] > Negative, it has nothing to do with the internal components of a 1st stage > whatsoever nor does it have to do with achieving the gas's dew point. Not the dew point, but the water molecules mass inertia. It keeps them going straight when they should turn. Same action in a compressor filter designed exactly with this phenomen in mind. > High gas velocity through a 1st stage causes the entire 1st stage to > become very cold. The 'cold' affects only 1 part, that being the bias spring. [quoted text clipped - 4 lines] > designed because it's compression characteristics have been hampered by the ice > buildup. Yes, and this independently wether there is some sort of rubber, grease, whatsoever, on the spring. Once the spring housing is full of ice ( and this ice can make a pretty bulk around the reg, the spring action may be hampered. > it's a very good design. I'd suggest that Poseidon's design enhancement is > something most diaphragm manufacturers have missed the boat on. We´hen you see it, you start asking why they did not design it like that from the beginning... it's so simple... > > The frige action you allude to is a simple > > question of how many holes are drilled into the spring chamber, not the [quoted text clipped - 3 lines] > stage. Stagnant water held in a poorly drainable ambient chamber only makes the > ice form faster, No objection. Just keep the water running. Through big holes. however one can never eliminate the problem unless one seals the > bias spring from contact with the cold water. Or this. > > Look at the Draeger Shark 2nd stage for a minute. Upstream, > > pneumatically balanced, when an undue rise of IP occurs, the OPV lets [quoted text clipped - 5 lines] > whereas the other "bleeds" gas off into reg. I wouldn't call that the same. Now, > consider a 2nd stage failure. When a downstream reg fails, it simply freeflows. So you can breathe by the freeflow... This is no problem with Poseidons or other 2nd stages of similar geometry. However, with ordinary regs, I believe this can be somewhat unpleasant. > When an upstream 2nd stage fails it does what?... Not much, exactly. You mean, when it sticks closed, there is no rise in IP because there is no demand, or venturi action, which opens the first stage's valve? May be, but up to now I only had upstream 2nd "fail" open, meaning there was a little blowby which you might ignore or not. > Agreed. Obviously a nylon orifice cannot sustain a knife edge for > anywhere near as long as a stainless steel one. But, it does prevent ice > formation. :) Hm, there comes to my mind just a few regs which are known here for notorious freezing.... > > > Diaphragm regs run the price gamete from low, med. to high. Non enviro > > > sealed diaphragm regs are usually the least expensive in the diaphragm [quoted text clipped - 4 lines] > That is not only anecdotal but you demonstrate a definite non-objective > bias. Well, some experience as well... Among else, I dive a cyklon 300 since 1984. Among else, that means Scubapro MK 10BA, MK2, D350, Drager PA 80, Secor 200,300, Shark, Apeks TX 20, 50, 100, Monomat, Duomat. there're > hard to defend. However, other than say Kirby Morgan, who even makes a > non-balanced SCUBA 1st stage for the recreational dive market in this day and age? Scubapro MK 14, Poseidon Cyklon 300 ( unofficialy, you get it, but it is not in the charts) > Jetstream with an Xstream and/or Odin. Those shower head regs, although not the > best breathers to say the least, rarely fail nor will they ever free flow. Big > bonus! :) Well they are a bit "digital" ;-), like driving a diesel... They may freeflow when illadjusted, and that's frightening to see ( especially the gauge...) > > Just my 2 Euro-CC > > Just my 2 Cold Canadian Pesos imported under the Free Trade Agreement from > the U.S.. Don'let the FBI know ;-) Matthias > That is your opinion and it's valued. However, I'd suggest that test >bench results are a little less biased than either you or I. :) I'll say this >though, for icy diving there's probably no better reg on the planet than a sealed >Jetstream with an Xstream and/or Odin. Those shower head regs, although not the >best breathers to say the least, rarely fail nor will they ever free flow. Big >bonus! :) >-- >Randy F. Milak >~And your crybaby whiny-assed opinion would be...?~ Easy there, I have dove Poseidon's for close to 20 yrs in cold fresh water. I have yet to try another reg at depth that delivers as cleanly and easily in all positions. That said I would never dive one on it's own. You name the high end GUE suggested reg’s, I have dove them. There just not Poseidons nor work as well for me. Back to Topic. I never had a free flow, but I have had the first stage ice up and lock.(both on my twins) First one then a few breaths later the second one. Used a Brut (Sherwood) on a travel bottle to get my a.s and my partners out of there. His two Poseidon's locked up as well. His USD Artic crapped as well. I wasn't about to suck pure O2 (MR 12’s) The small single hole doesn't allow for a lot of water exchange. I have used the cold kit, but it can get cut or knocked off while wreck diving. Or the dam thing just falls off in transit. I have used the old back up of a condom, but they fail pretty easily in inside a wreck. Besides try explain to the wife what condoms and vodka are doing in with your dive gear:). And in both cases it has rendering the extra protection useless. The other caution is to use high proof vodka, doesn't stain when the cap comes off and if it enters the reg not as big a deal as glycol. Lastly they can free flow, but out of the blow off on the hose. This generally is a service issue. Since they normally creep before they get to this stage, it’s more the dolt on the mouth piece’s fault. ie They burp once in a while when not used but pressurized. Some just ignore this because as they breathe it the burping stops. Big mistake. I use a intermediate pressure gauge and when I can’t get it to lock up at 141 psi, in it goes for service. The jargon for this is "excessive creep". Some creep is allowed, but it must lock up. Freshly serviced, there should be no creep, if there is you have a defective seat or it was installed without the right tool and got damaged. It should be changed, the shop isn’t out anything because the sales rep should exchange the defective seats. This is not that common for new seats but does happen. Some shops just swap the seats around in the kits, it will work sometimes. But in the end, you end up with a bunch of defective seats in stock. This where the reg gets the reputation of being hard to work on. Plus they frustrate the tech because he's working with defective seats. When I first took over a dive shop, one of the first things I did was toss out any seat that look like it had been swapped out. After a while I found the ones I missed the hard way. (ie have to redo the reg wouldn't pass the bench test). After that it was a piece of cake and I ended up doing most of the P's in southern Ontario. On average would be 3 or 4 a week year round. I did service other bands as well and subcontracted those I was not certified by the manufacture to do. So I think I got a handle on reg's. I run with the old saying. What works, works. Then my personal mottos "After you" and "Here we go again?" (aka reinventing the wheel) Maybe that's why I continue to suck air. Toto > Define performance. Your question is like asking which is better, a Ford or a > GM. They both use a 4 cycle reciprocating piston engine, so not really a good analogy. A better one would be "Which is better, a traditional piston engine car or a rotary engine". Like the "traditional" engine, diaphragm regs are limited in throughput, but not so as 99.9% of divers would ever notice, they are an older design, and more "reliable" without extensive servicing. Piston regs, like a rotary engine, are a newer design, have a much higher throughput that to 99.9% of divers should only be of academic interest, need more care, have more troublesome seals, and need more frequent servicing. Either type will do the job though. Cheers David M > Piston regs, like a rotary engine, are a newer design, Only by a year. Crossley's reg (1825) was diapragm, Pouilliot (1826) designed both diaphragm and piston regs, though his Hydroploma used the piston design. Guillaumet (1838) dove a diaphragm design and Rouguayrol-Denayrouze (1872), the first commercially succesful scuba unit, was diaphragm. And Commheines used neither in his G.C. 47, with which he dove to 174 feet off Marseille in July, 1943. The G.C. 47 used a bladder which shrinks when inhaling, triggering gas flow. In 1958, Sherwood purchased a patent for a piston regulator and began mass production of variants branded US Divers, SCUBAPro, Dacor, Nemrod, Healthways, Voit and others. It is reported that Sherwood paid nothing for the patent. Pouillot may have had something to do with the price. > > Piston regs, like a rotary engine, are a newer design, > > Only by a year. But still newer, and thus by extension most likely an attemp to evolve/improve in one or many of several aspects. A "better mousetrap" so to speak. Like the rotary engine. Cheers David M > > > Piston regs, like a rotary engine, are a newer design, > > [quoted text clipped - 6 lines] > Cheers > David M yeah, if they could solve the rotor seal problems, it would be a better mousetrap. -- An amateur built the ark ....professionals built the Titanic. > yeah, if they could solve the rotor seal problems, it would be a better > mousetrap. Just like sand getting in the o-rings of a piston reg! It all comes down to your priorities though - I mean some people don't mind having to change apex seals in their 13B's every so often for the increase in power to weight ratio etc... Cheers David M >> > > Piston regs, like a rotary engine, are a newer design, >> > [quoted text clipped - 9 lines] > yeah, if they could solve the rotor seal problems, it would be a better > mousetrap. It's only in the last twenty years that they got the rings in a boinger to last, and the seals in the newer rotaries are a lot better. It's the O-rings between housings that go to hell. "mike gray, CID" schrieb: > > mousetrap. > > It's only in the last twenty years that they got the rings in a boinger > to last, and the seals in the newer rotaries are a lot better. It's the > O-rings between housings that go to hell. And sometimes the O-ring that seals the high pressure bolt into the housing. This is due to "user error", mostly when people have dirt in their DIN valve, and put leverage on the reg housing, instead of on its fastening screw, to be able to unscrew it from the bottle. This may loosen the central bolt, thus allowing to much idle for the O-ring, cuasing the pressure to nag on its rim, allowing water ingress in further progress. Divers might not notice it, because they may have devellopped a habit of tightening the central screw ever so often. Matthias I'm a bit confused. My reader says that Randy sent his note of Nov. 19 on Nov. 30th. Anyone else see that? > I'm a bit confused. My reader says that Randy sent his note of Nov. 19 on > Nov. 30th. Anyone else see that? My 'puter clock was accidentally reset by me checking dates... please forgive the faux pau. -- Randy F. Milak ~Boy's 'bout as bright as a wind-up clock without a key!~
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