Onboard vs. Offboard Deco

silent running · 4th November 2006, 23:24

Quote: (Originally Posted by viscya)

????? Where is DrMike when you need him!

Viscya, I'm not suggesting that anybody go back on the loop after a CO2 hit. I don't think anybody else is either. I'm talking about having to go SCR to avoid a CO2 after a long overstay on the bottom and huge extra unplanned deco, like Mark posed in his extra deco emergency scenerio. It's about looking ahead when you have unplanned extra deco, only so much gas and only so much life left in the scrubber, a situation I hope none of us ever has to contend with. -Andy

silent running · 4th November 2006, 23:30

Quote: (Originally Posted by Mark Chase)

My dick still works OK

ATB

Mark Chase

He he he! A working willie is one thing most ladies insist on.

viscya · 5th November 2006, 00:25

Quote: (Originally Posted by silent running)

Viscya, I'm not suggesting that anybody go back on the loop after a CO2 hit. ... -Andy

SR,

I beg to differ. Mark is talking about it for a CO2 hit in this post:

Quote: (Originally Posted by Mark Chase)

Total loss of 02 and a C02 hit. Plugging in the 50 and running off that is a possibility ...
Mark Chase

Now if you are referring to this post:

Quote: (Originally Posted by Mark Chase)

Discuss the situation for me. Your stuck inside a wreck at 65m you have been there for an hour, you just got out but your scrubber is screwed because its the second dive on it and you don't trust it to last the 4 hours of deco, you haven't got enough bailout to go OC so you go semi closed.

Mark Chase

Mark is talking about SC to extend the GAS not the scrubber. What he is really alluding to is that someone running tables or an external Constant PO2 computer is screwed.

If you want to talk about using SC to extend your scrubber, I suggest taking it off line, so some novices does not mistake it for an accepted practice.

silent running · 5th November 2006, 01:46

Quote: (Originally Posted by viscya)

SR,

I beg to differ. Mark is talking about it for a CO2 hit in this post:

Now if you are referring to this post:

Mark is talking about SC to extend the GAS not the scrubber. What he is really alluding to is that someone running tables or an external Constant PO2 computer is screwed.

If you want to talk about using SC to extend your scrubber, I suggest taking it off line, so some novices does not mistake it for an accepted practice.

First off, why would I be screwed if I'm using an offboard comp? I would use the average mix I have in my gas list for my slung cyl mix in OC mode on the comp. At such a crisis point, with or without an inline sensor, you only have so much gas. Either it's enough to get out of the water safely at a 1/3 or 1/4 ratio, or it's not. An inline sensor will be able to tell you exactly when you're done with the deco based on your actuall inspired gas. An offboard comp will tell you the same info, based on the average mix. It's a little more risky, but in order to minimize the risk, I would probably breathe down the whole cyl if I had enough, even if my offboard comp says I'm done. Hopefully I will never face such a situation but I'm not willing to add another sensor, seals, and wire/clutter-all possible failure points-for a scenerio that I can still handle without all that stuff.

As for extending the scrubber, could you please explain how one can extend one's gas on SCR without extending one's scrubber as well?

If you have 2+ hrs on your scrubbber after being stuck in a wreck for an hr on your 2nd dive and then finally begin your ascent and switch out of constant PO2 mode, your TTS updates to 3/4hrs of deco, you then know that you'll probably will have a CO2 hit at about the 1 hr mark and decide to go SCR now to keep from exahusting the scrubber sooner rather than later, right?

SCR on CCR is not discussed much, I don't think any novices will mistake this discussion for an endorsement of it as first line BO practice. As soon as they take their CCR class, they'll find out that it's a last resort.

silent running · 5th November 2006, 02:31

Just to be clear viscya, I understand that the first benefit of going SCR is conserving gas when you don't have enough for OC BO. Whatever extra scrubber life you may gain will not be a lot-say another 25-30% ?-instead of if you had been able to keep the loop closed. But it is going to help keep you on the loop longer and the scrubber will be taxed less and less as you ascend.

Mark Chase · 5th November 2006, 12:02

Quote:

I beg to differ. Mark is talking about it for a CO2 hit in this post:

Just to clarifie, the question was what would force you to go semi closed and I replied (obviously not very clearley) Out of 02 OR a co2 hit. I said and in my post meaning 1 & 2 but seporatly.

Obviously you wouldent decide to stop running the unit on 02 and run it on 50% folowing a co2 hit.

Sorry for the confusion

Quote:

If you want to talk about using SC to extend your scrubber, I suggest taking it off line, so some novices does not mistake it for an accepted practice

Dont tell the RB80 boys that they will get realy upset. What are they doing? 12 hours on a scrubber slightly bigger than my inspo?

ATB

Mark Chase

dive2dive2000 · 5th November 2006, 20:41

Quote: (Originally Posted by PaulTG2)

Hello,

I am currently in the process of purchasing a CCR and have been tossing around the issue of onboard vs offboard decompression. I was wondering what people's overall thoughts were on this.

I believe I've settled on not having onboard decompressions and going with a wrist computer to do it. The primary reason is that, as happens from time to time, the rebreather has a problem and I decide to do a dive or two on OC until the Rebreather is fixed.

What are people's thoughts on onboard vs offboard decompression.

If you use onboard deco computers how do you handle situation where you have an OC dive -- or perhaps a dive on another rebreather -- when you're rebreather tanks.

Sincerely,

Paul

Hi Paul,

Which Rebreather are you buying? This might influence what direction you take in the beginning. I dive a PRISM with a Explorer computer. I always run tables and honestly with Pocket PC if my dive plan changes it is real easy to change tables. If money is tight a computer can go to the bottom of the wish list IMHO. I personally feel less stressed mentally running tables and end up using my computer as a Bottom timer. Hope this helps

4th November 2006, 23:24	#31 (permalink)
silent running Mature mouth breather Current Rebreather/s: Prism Topaz Other Rebreather/s: Join Date: Jun 2005 Location: U.S.A. Brooklyn, New York Posts: 1,813	Re: Onboard vs. Offboard Deco Quote: (Originally Posted by viscya) ????? Where is DrMike when you need him! Viscya, I'm not suggesting that anybody go back on the loop after a CO2 hit. I don't think anybody else is either. I'm talking about having to go SCR to avoid a CO2 after a long overstay on the bottom and huge extra unplanned deco, like Mark posed in his extra deco emergency scenerio. It's about looking ahead when you have unplanned extra deco, only so much gas and only so much life left in the scrubber, a situation I hope none of us ever has to contend with. -Andy
(Online)

4th November 2006, 23:30	#32 (permalink)
silent running Mature mouth breather Current Rebreather/s: Prism Topaz Other Rebreather/s: Join Date: Jun 2005 Location: U.S.A. Brooklyn, New York Posts: 1,813	Re: Onboard vs. Offboard Deco Quote: (Originally Posted by Mark Chase) My dick still works OK ATB Mark Chase He he he! A working willie is one thing most ladies insist on.
(Online)

5th November 2006, 00:25	#33 (permalink)
viscya Wrecking Crew Current Rebreather/s: Classic Kiss Other Rebreather/s: Join Date: Oct 2005 Location: Marlton New Jersey Posts: 140	Re: Onboard vs. Offboard Deco Quote: (Originally Posted by silent running) Viscya, I'm not suggesting that anybody go back on the loop after a CO2 hit. ... -Andy SR, I beg to differ. Mark is talking about it for a CO2 hit in this post: Quote: (Originally Posted by Mark Chase) Total loss of 02 and a C02 hit. Plugging in the 50 and running off that is a possibility ... Mark Chase Now if you are referring to this post: Quote: (Originally Posted by Mark Chase) Discuss the situation for me. Your stuck inside a wreck at 65m you have been there for an hour, you just got out but your scrubber is screwed because its the second dive on it and you don't trust it to last the 4 hours of deco, you haven't got enough bailout to go OC so you go semi closed. Mark Chase Mark is talking about SC to extend the GAS not the scrubber. What he is really alluding to is that someone running tables or an external Constant PO2 computer is screwed. If you want to talk about using SC to extend your scrubber, I suggest taking it off line, so some novices does not mistake it for an accepted practice. __________________ "There is nothing majestic or dignified about being left to silently rot and collapse under heaps of old fishing net forgotten and unappreciated in dark and unvisited waters." DrMike Last edited by viscya : 5th November 2006 at 00:28.
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5th November 2006, 01:46	#34 (permalink)
silent running Mature mouth breather Current Rebreather/s: Prism Topaz Other Rebreather/s: Join Date: Jun 2005 Location: U.S.A. Brooklyn, New York Posts: 1,813	Re: Onboard vs. Offboard Deco Quote: (Originally Posted by viscya) SR, I beg to differ. Mark is talking about it for a CO2 hit in this post: Now if you are referring to this post: Mark is talking about SC to extend the GAS not the scrubber. What he is really alluding to is that someone running tables or an external Constant PO2 computer is screwed. If you want to talk about using SC to extend your scrubber, I suggest taking it off line, so some novices does not mistake it for an accepted practice. First off, why would I be screwed if I'm using an offboard comp? I would use the average mix I have in my gas list for my slung cyl mix in OC mode on the comp. At such a crisis point, with or without an inline sensor, you only have so much gas. Either it's enough to get out of the water safely at a 1/3 or 1/4 ratio, or it's not. An inline sensor will be able to tell you exactly when you're done with the deco based on your actuall inspired gas. An offboard comp will tell you the same info, based on the average mix. It's a little more risky, but in order to minimize the risk, I would probably breathe down the whole cyl if I had enough, even if my offboard comp says I'm done. Hopefully I will never face such a situation but I'm not willing to add another sensor, seals, and wire/clutter-all possible failure points-for a scenerio that I can still handle without all that stuff. As for extending the scrubber, could you please explain how one can extend one's gas on SCR without extending one's scrubber as well? If you have 2+ hrs on your scrubbber after being stuck in a wreck for an hr on your 2nd dive and then finally begin your ascent and switch out of constant PO2 mode, your TTS updates to 3/4hrs of deco, you then know that you'll probably will have a CO2 hit at about the 1 hr mark and decide to go SCR now to keep from exahusting the scrubber sooner rather than later, right? SCR on CCR is not discussed much, I don't think any novices will mistake this discussion for an endorsement of it as first line BO practice. As soon as they take their CCR class, they'll find out that it's a last resort.
(Online)

5th November 2006, 02:31	#35 (permalink)
silent running Mature mouth breather Current Rebreather/s: Prism Topaz Other Rebreather/s: Join Date: Jun 2005 Location: U.S.A. Brooklyn, New York Posts: 1,813	Re: Onboard vs. Offboard Deco Just to be clear viscya, I understand that the first benefit of going SCR is conserving gas when you don't have enough for OC BO. Whatever extra scrubber life you may gain will not be a lot-say another 25-30% ?-instead of if you had been able to keep the loop closed. But it is going to help keep you on the loop longer and the scrubber will be taxed less and less as you ascend.
(Online)

5th November 2006, 12:02	#36 (permalink)
Mark Chase I go down for ages Current Rebreather/s: Classic Kiss Other Rebreather/s: Inspiration Classic Join Date: Jan 2005 Location: Kent Posts: 2,556	Re: Onboard vs. Offboard Deco Quote: I beg to differ. Mark is talking about it for a CO2 hit in this post: Just to clarifie, the question was what would force you to go semi closed and I replied (obviously not very clearley) Out of 02 OR a co2 hit. I said and in my post meaning 1 & 2 but seporatly. Obviously you wouldent decide to stop running the unit on 02 and run it on 50% folowing a co2 hit. Sorry for the confusion Quote: If you want to talk about using SC to extend your scrubber, I suggest taking it off line, so some novices does not mistake it for an accepted practice Dont tell the RB80 boys that they will get realy upset. What are they doing? 12 hours on a scrubber slightly bigger than my inspo? ATB Mark Chase __________________ Is it supposed to make that noise ? I took my unit to the dive shop and demanded they bolt on every thing that would fit. Join my elite diving teem and get a Tshirt "Doing It Chasey"Hammerhead Eccr Advanced Diving System
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5th November 2006, 20:41	#37 (permalink)
dive2dive2000 PRISM DIVER & LUVIN IT! Current Rebreather/s: Prism Topaz Other Rebreather/s: Join Date: Feb 2005 Location: Long Island, NY Posts: 788	Re: Onboard vs. Offboard Deco Quote: (Originally Posted by PaulTG2) Hello, I am currently in the process of purchasing a CCR and have been tossing around the issue of onboard vs offboard decompression. I was wondering what people's overall thoughts were on this. I believe I've settled on not having onboard decompressions and going with a wrist computer to do it. The primary reason is that, as happens from time to time, the rebreather has a problem and I decide to do a dive or two on OC until the Rebreather is fixed. What are people's thoughts on onboard vs offboard decompression. If you use onboard deco computers how do you handle situation where you have an OC dive -- or perhaps a dive on another rebreather -- when you're rebreather tanks. Sincerely, Paul Hi Paul, Which Rebreather are you buying? This might influence what direction you take in the beginning. I dive a PRISM with a Explorer computer. I always run tables and honestly with Pocket PC if my dive plan changes it is real easy to change tables. If money is tight a computer can go to the bottom of the wish list IMHO. I personally feel less stressed mentally running tables and end up using my computer as a Bottom timer. Hope this helps __________________ Safe Diving, Martin "but what's the fun of getting what you need, instead of what you want?"
(Offline)

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