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Scuba Forum / Scuba Equipment / March 2005Doubles question
I was wondering about a situation that could arise using doubles with an isolator manifold. Say you're diving, your primary reg freeflows, and you shut that reg down. Now, if you're not using an inflation system, your drysuit (and BC) are presumably hooked to your primary reg, which is now shut down. You can orally inflate the BC, but can no longer add air to the drysuit. I assume at this point you would abort the dive, so there would be no need to add air, only vent as you ascended? Am I thinking correctly? Or is it better to have an inflation system (argon bottle, etc.)? >I was wondering about a situation that could arise using doubles with an >isolator manifold. Say you're diving, your primary reg freeflows, and you [quoted text clipped - 4 lines] >no need to add air, only vent as you ascended? Am I thinking correctly? Or >is it better to have an inflation system (argon bottle, etc.)? I'm not a drysuit diver, but the answers to this seem pretty straight forward: You're most likely right about aborting the dive and about not needing to add additional gas to your drysuit, particularly if you're one who subscribes to the philosophy of using the drysuit for warmth and the BCD for buoyancy. There seems, however, to be more to the question than that. Specifically, there are options that would prevent the kind of problem you describe. On, which you mentioned, is an argon bottle for your drysuit. Another, however, is simply to hook the drysuit to one regulator and the BCD to the other. You've got all that is necessary to separate them, adding redundancy without adding complexity. Lee >I was wondering about a situation that could arise using doubles with an >isolator manifold. Say you're diving, your primary reg freeflows, and you [quoted text clipped - 4 lines] >no need to add air, only vent as you ascended? Am I thinking correctly? Or >is it better to have an inflation system (argon bottle, etc.)? If you are not using an independent drysuit inflation system like an argon bottle, the BC inflator hose is connected to one first stage (most people I know use the right post for this) and the drysuit inflator is connected to the other. This way, if you have to shut one post down, you still have an inflation source on the other post. Personally, I prefer to always use a separate inflation system when I'm diving with a drysuit (even if the bottle only contains air instead of 100% argon). -bob >Personally, I prefer to always use a separate inflation system when >I'm diving with a drysuit (even if the bottle only contains air >instead of 100% argon). Why, Bob? Argon I can understand, but a separte bottle for air only seems like unneeded complexity. Observation: Drysuite valves can fail. I've seen one freeflow into the suite. The solution was to disconnect the hose and ascend using the BCD to control bouyance.  SignatureCharlie Hammond -- Hewlett-Packard Company -- Ft Lauderdale FL USA (hammond@not@peek.ssr.hp.com -- remove "@not" when replying) All opinions expressed are my own and not necessarily my employer's. >>Personally, I prefer to always use a separate inflation system when >>I'm diving with a drysuit (even if the bottle only contains air >>instead of 100% argon). > > Why, Bob? Argon I can understand, but a separte bottle for air only > seems like unneeded complexity. You know one answer to this. You just didn't link it to the situation. Consistency. Argon provides a thermal benefit. A diver that desires that benefit, has to set up for it. He can reasonably be expected to retain the same configuration even when the Argon is not available or not necessary (I presume air is cheaper). The DIR philosophy makes this even more clear. Everything should be as close to the same as possible, every time. > Observation: Drysuite valves can fail. I've seen one freeflow into > the suite. The solution was to disconnect the hose and ascend using > the BCD to control bouyance. This leads to a second reason, at least in my twisted mind. If the valve into the drysuit fails, having a separate bottle does two things. It preserves your breathing gas and it provides an option for controlling suit inflation, opening and closing the valve on the separate bottle. Lee > >>Personally, I prefer to always use a separate inflation system when >>>I'm diving with a drysuit (even if the bottle only contains air [quoted text clipped - 9 lines] >presume air is cheaper). The DIR philosophy makes this even more clear. >Everything should be as close to the same as possible, every time. Frankly, I don't know if the "DIR philosophy" makes ANYthing "clear" -- I'm not even convinced that it is properly called a "philosophy". But this is another issue and probably beside the point here. Some philosopy says "keep it simple". The less gear your messin' with, the less things to go wrong. And some philosopy says "take the right gear for the dive youor doing". Both of these argue against an extra/unnecessary bottle and regulator. >> Observation: Drysuite valves can fail. I've seen one freeflow into >> the suite. The solution was to disconnect the hose and ascend using [quoted text clipped - 4 lines] >preserves your breathing gas and it provides an option for controlling suit >inflation, opening and closing the valve on the separate bottle. O.K., you've got a point here. Howeer, to my mind the added gear is not worht the value. The amount of breathing gas lost in the time it takes to pull the hose off the drysuit valve isn't that great. And the need to continue drysuit inflation while ascending from an aborted dive is not very great either. (Assuming a BCD to control bouyancy.) SignatureCharlie Hammond -- Hewlett-Packard Company -- Ft Lauderdale FL USA (hammond@not@peek.ssr.hp.com -- remove "@not" when replying) All opinions expressed are my own and not necessarily my employer's. > You know one answer to this. You just didn't link it to the situation. > Consistency. Argon provides a thermal benefit. A diver that desires that > benefit, has to set up for it. He can reasonably be expected to retain the > same configuration even when the Argon is not available or not necessary (I > presume air is cheaper). The DIR philosophy makes this even more clear. > Everything should be as close to the same as possible, every time. It's more likely because he has a squirt of helium in his back gas. Helium is a horrible insulator. > > You know one answer to this. You just didn't link it to the > situation. [quoted text clipped - 10 lines] > It's more likely because he has a squirt of helium in his back gas. > Helium is a horrible insulator. Plus it opens up that whole isobaric counterdiffusion thing, and we really don't want to go there :-) Thanks to all for what should have been an obvious solution. I guess I'll never do very well on a Mensa test! > ? Lee Bell wrote: > ? > You know one answer to this. You just didn't link it to the [quoted text clipped - 15 lines] > Plus it opens up that whole isobaric counterdiffusion thing, and we > really don't want to go there :-) > Thanks to all for what should have been an obvious solution. I guess I'll > never do very well on a Mensa test! We're just linking known information together to form a whole. True genius goes outside of the box to discover new information. Don't let doing well on MENSA tests bother you, one way or the other. There's most certainly more than one person present in the group that scored well enough to join but declined the "honor." Lee >>I was wondering about a situation that could arise using doubles with an >>isolator manifold. Say you're diving, your primary reg freeflows, and you [quoted text clipped - 5 lines] >>no need to add air, only vent as you ascended? Am I thinking correctly? Or >>is it better to have an inflation system (argon bottle, etc.)? Wrong. Why have two cylinders and two 1st stages and feed BOTH buoyancy devices from a single 1st stage? You would have to look at your hose configuration. Firstly you assume that both of your inflator hoses are fed from the primary (right post) 1st stage. This is incorrect and an illogical system. Your wing / BC should be fed from the primary 1st stage on the right hand cylinder and your drysuit should be fed from the backup 2nd stage on the left cylinder. Also, if both your BC and drysuit are fitted with the same connections (Schrader valve), which is easily accomplished by the purchase of a spare BC inflator hose and swapping the 'nipple' on the suit valve to the same as fitted to your BC / wing, then you can use either hose on either inflator (a good reason for a swivelling drysuit inflator valve). That way you have a buoyancy device active even if you need to shut down either cylinder. There is no need to go to the expense of an argon cylinder for dry-suit fills (unless you are diving on TriMix, and based upon your question I expect you're not). Tony, No one likes to be misquoted. If you will check the posts carefully, I did not post this part of the thread -- only replied to it. If you already have a separate argon drysuit inflation system (which I do), why not use it? I like the consistency and redundancy, and, as Al Wells mentioned, I often use helium, even for dives in the 80 to 130 ft range. For warmer water, like Florida cave diving, I often use air in the bottle instead of argon. Using helium to inflate you drysuit gets kinda chilly! Best, -bob >>>I was wondering about a situation that could arise using doubles with an >>>isolator manifold. Say you're diving, your primary reg freeflows, and you [quoted text clipped - 30 lines] >fills (unless you are diving on TriMix, and based upon your question I >expect you're not). > Tony, > > No one likes to be misquoted. If you will check the posts carefully, I > did not post this part of the thread -- only replied to it. That's because I as not answering your post by 'K's post He asked the question~: "I was wondering about a situation that could arise using doubles with an isolator manifold. Say you're diving, your primary reg freeflows, and you shut that reg down. Now, if you're not using an inflation system, your drysuit (and BC) are presumably hooked to your primary reg, which is now shut down. You can orally inflate the BC, but can no longer add air to the drysuit. I assume at this point you would abort the dive, so there would be no need to add air, only vent as you ascended? Am I thinking correctly? Or is it better to have an inflation system (argon bottle, etc.)?" My answer was based upon the obvious facts that: 1. He does not currently have a manifolded twinset. 2. He is getting either no advice or worthless advice from his local divers and dive shops. 3. He also does not have a Argon inflation system. READ THE QUESTION BEFORE RUNNING OFF AR THE MOUTH (or fingers). >> Tony, >> [quoted text clipped - 24 lines] > >READ THE QUESTION BEFORE RUNNING OFF AR THE MOUTH (or fingers) Looks like another village is missing an idiot. >>READ THE QUESTION BEFORE RUNNING OFF AR THE MOUTH (or fingers) > > Looks like another village is missing an idiot. That's a perfect case of the pot calling the kettle black. Or to quote another oft used phrase: people in glass houses should not throw stones. > Looks like another village is missing an idiot. Sorry, I forgot that those with the least to say open their mouths the most. If my last post was not clear enough for your monocellular brain, then I'll be blunt. If you've nothing worthwhile to say then SHUT UP! >I was wondering about a situation that could arise using doubles with an >isolator manifold. Say you're diving, your primary reg freeflows, and you >shut that reg down. Now, if you're not using an inflation system, your >drysuit (and BC) are presumably hooked to your primary reg, which is now >shut down. While configerations vary, few use one post for all functions. The goal in cold water diving is not to tax the regulator. You do this by using one primary for breathing and the other for inflation. If you shut down the post you are breathing from you switch to the post you were using for inflation. One would stabilize at depth, try to stop the free flow, and decide on an alternative after seeing if the leaking stops and how you feel about going on. > You can orally inflate the BC, but can no longer add air to the drysuit. I > assume at this point you would abort the dive, so there would be no need > to add air, only vent as you ascended? Am I thinking correctly? Or is it > better to have an inflation system (argon bottle, etc.)? There is nothing wrong with a separate inflation system. Other posters presented good points. An argon bottle, regulator, relief valve, and hose are more things to carry and maintain. Better is a relative term. >> You can orally inflate the BC, but can no longer add air to the drysuit. >> I assume at this point you would abort the dive, so there would be no [quoted text clipped - 4 lines] > presented good points. An argon bottle, regulator, relief valve, and hose > are more things to carry and maintain. Better is a relative term. And more to go wrong and get in the way of a nice simple configuartion. Less is often more. |
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