How long can absorbent be stored?!

PacketSniffer · 10th February 2007, 14:51

Quote: (Originally Posted by jaap)

<snip>
I belive that very dry sorb is _very_ dangerous if the user does not perform a long prebreathing (>5min) to moisen the sorb and get a chance to feel if its working OK.

Yes. This statement is very important since one doesn't have the benefit of the activator any longer. It was used up when one starts the canister for the first time. This is why it is extremely important to pre-breathe a partially used canister in order to ensure you've given the canister enough time to start the chemical reaction.

Something that has not been stated clearly is the type of diving one does on a partially used canister. While some say don't use it past 24 hours, others say it's ok to use it much, much later (like years...lol) but aren't saying the type of diving they are doing. If one is doing deep, long, or cold dives, it's obvious a fresh fill is in order. Something to the other end of the spectrum can be more accomodating to a partially used canister.

Dutchy · 10th February 2007, 15:06

Quote: (Originally Posted by PacketSniffer)

This statement is very important since one doesn't have the benefit of the activator any longer.

What activator? If you are referring to the NaOH as an activator then that's not true. Although the NaOH is used in the second reaction step it is returned in the third reaction step. It is not used at all. If you were referring to water as the activator then that's used indeed, but (only slightly) more is produced as a result of the reaction. What is it that you designate as activator?

PacketSniffer · 10th February 2007, 15:51

Quote: (Originally Posted by Dutchy)

What activator? If you are referring to the NaOH as an activator then that's not true. Although the NaOH is used in the second reaction step it is returned in the third reaction step. It is not used at all. If you were referring to water as the activator then that's used indeed, but (only slightly) more is produced as a result of the reaction. What is it that you designate as activator?

If I understand it correctly, in soda lime, potassium hydroxide [KOH] is used as an activator. If using a partially used canister, it is no longer present due to the continued but diminishing chemical reaction that continues from the moment one stops breathing the loop from their dive. So, when one uses a partially used canister, it is important to ensure a fair amount of time for pre-breathing the unit since you don't have the aid of KOH.

For me, at this point in time, it is not so important to know how the process works as it is to know that there is a danger in not pre-breathing adequately a partially used canister. However, that does not mean I am not interested in the details. I continue to absorb as much information as I can comprehend and continue to seek these answers as I move forward in the never ending quest for experience in this fascinating sport. Please enlighten me if I don't have the details correct.

Cheers

**Gill Envy** · 10th February 2007, 17:40

Quote: (Originally Posted by nigelh)

After a day's diving I strip the rig, clean it, dry the head out, put it back together and close it up.

I assume the scrubber material will last longer than the oxygen cells, probably longer than the regulators. If my next dive is another short one I carry on using the same stuff but if it is a big one or a day trip I reload it. The chemistry is too simple to degenerate, well unless you flooded the thing.

Nigel, not sure if i'm reading your post right. I was doing pretty much the same thing, cleaning, re-assembling, until it dawned on me that the spring in the scrubber could get fatigued over time that way. Since the spring is one of the more important pieces for avoiding chanelling, i decided to start leaving the scrubber out. Eventually, and perhaps more importantly, I realized the main o-ring in the head could get flattened if i left the bucket on the head. Now i pretty much leave every part of the loop un-assembled (withing reason) if there are many days inbetween dives to keep all the O-rings in tip top shape.

jptaylor9 · 10th February 2007, 17:52

Quote: (Originally Posted by Gill Envy)

Nigel, not sure if i'm reading your post right. I was doing pretty much the same thing, cleaning, re-assembling, until it dawned on me that the spring in the scrubber could get fatigued over time that way. Since the spring is one of the more important pieces for avoiding chanelling, i decided to start leaving the scrubber out. Eventually, and perhaps more importantly, I realized the main o-ring in the head could get flattened if i left the bucket on the head. Now i pretty much leave every part of the loop un-assembled (withing reason) if there are many days inbetween dives to keep all the O-rings in tip top shape.

Have you spoken to anyone at AP about this? Just wondered what the factory view was?

**Gill Envy** · 10th February 2007, 17:55

Quote: (Originally Posted by PacketSniffer)

Yes. This statement is very important since one doesn't have the benefit of the activator any longer. It was used up when one starts the canister for the first time. This is why it is extremely important to pre-breathe a partially used canister in order to ensure you've given the canister enough time to start the chemical reaction.

Something that has not been stated clearly is the type of diving one does on a partially used canister. While some say don't use it past 24 hours, others say it's ok to use it much, much later (like years...lol) but aren't saying the type of diving they are doing. If one is doing deep, long, or cold dives, it's obvious a fresh fill is in order. Something to the other end of the spectrum can be more accomodating to a partially used canister.

I was instructed to leave the scrubber out to dry for 8 hours, to get excess moisture out and then bag it, to retain the rest of the moisture, which i'm told is more important an issue than keeping it sealed to avoid co2 exposure, as very little co2 will ever go through it passively.

Scrubber seems to not change at all with time, years might actually be acurate, but don't push it too hard, your life is more valuable than a fill, i get very leery after a couple of weeks.

My general rule of thumb: don't re-use after a dive deeper than recreational limits, best to chuck it, since the reactant front has gone deeper into the stack and is now hard to predict in terms of distance to breakthrough.

If i'm doing a deeper dive than previous, i chuck it... I do succesively shallower dives, to err on the side of narrower reactant fronts. This is all assuming that you stay within the time limits allowable for each depth, which is about as complicated to be totally sure of as decompression... the temp stick helps me cross check my guestimation (though i don't rely on it to push the limits, if it shows me a more conservative limit than i have sermized, i stick to that). And as PacketSniffer said so well, "If one is doing deep, long, or cold dives, it's obvious a fresh fill is in order. Something to the other end of the spectrum can be more accomodating to a partially used canister." accept that all of our dives are in relatively cold water (45-55 f).

**Gill Envy** · 10th February 2007, 18:01

Quote: (Originally Posted by jptaylor9)

Have you spoken to anyone at AP about this? Just wondered what the factory view was?

just checked with the wife, we both remember this being a recommendation during our mod1. I'm thinking tino re-iterated this in one of his threads, i might be wrong about who's post it was. Like anything you read on the inernet, if you like an idea, it's best to concur with one of your gurus or with the wonderful and most gracious Nickey at AP before putting it into action. Not joking, Nickey is very helpful, although with respect to scrubber recommendations, i think she has to follow the book on that one.

PacketSniffer · 10th February 2007, 18:13

Quote: (Originally Posted by Gill Envy)

And as PacketSniffer said so well, "If one is doing deep, long, or cold dives, it's obvious a fresh fill is in order. Something to the other end of the spectrum can be more accomodating to a partially used canister." accept that all of our dives are in relatively cold water (45-55 f).

And that is what I was getting at. People chime in from all over the world with their answers. But, often a piece of the answer is missing; in this case the environment. So we get all of these answers that are different. For you guys in the frigid water, most probably change it every dive regardless of time left on it vs. maybe someone from Hawaii who might be able to use the same fill a few times during the course of a week assuming they didn't go over the mfg. suggested accumulated time.

Quote: (Originally Posted by Gill Envy)

My general rule of thumb: don't re-use after a dive deeper than recreational limits, best to chuck it, since the reactant front has gone deeper into the stack and is now hard to predict in terms of distance to breakthrough.

This is another excellent point to make. Because as one example I've seen has shown is that the reactionary front gets very wide (in the stack length-wise) as it makes it's way to the end of the canister. So, the more spent it is, I would surmise the less reliable the absorbent may become for a partially used canister to be used again to exhaust it to its mfg suggested accumulated time.

Where is the gentlemen from Molecular Products?

Dutchy · 10th February 2007, 21:17

Quote: (Originally Posted by PacketSniffer)

If I understand it correctly, in soda lime, potassium hydroxide [KOH] is used as an activator.

If that is what you call the activator then that makes it clearer. Chemists will say that Potassium and Sodium are very much interchangably in many (nearly all) chemical reactions (Medics should disregard this sentence they know differently for their domain

) In both cases it isn't used up.
If there's truth in what you write then it must be though another mechanism e.g. less accesible because of bein enclose in the resulting calcium carbonate. I'll not dismiss the alleged effect just suggested mechanism. In the absence of facts I guess it's good to continue the good habit of prebreathing...
[/quote]

PacketSniffer · 10th February 2007, 21:27

Quote: (Originally Posted by Dutchy)

<snip>If there's truth in what you write then it must be though another mechanism e.g. less accesible because of bein enclose in the resulting calcium carbonate. I'll not dismiss the alleged effect just suggested mechanism. In the absence of facts I guess it's good to continue the good habit of prebreathing...

[/quote]

I was taught this by my Instructor. Subsequently, I did find the text that does explain it which is written by Joerg Hess, M.S. for that particular chapter. Please see IANTD Tek Closed Circuit Rebreather manual on page 51 & 52.

10th February 2007, 14:51	#21 (permalink)
PacketSniffer ~~~~~ #417 ~~~~~ Current Rebreather/s: Megalodon Other Rebreather/s: Join Date: Jun 2006 Location: Houston Posts: 432	Re: How long can absorbent be stored?! Quote: (Originally Posted by jaap) <snip> I belive that very dry sorb is _very_ dangerous if the user does not perform a long prebreathing (>5min) to moisen the sorb and get a chance to feel if its working OK. Yes. This statement is very important since one doesn't have the benefit of the activator any longer. It was used up when one starts the canister for the first time. This is why it is extremely important to pre-breathe a partially used canister in order to ensure you've given the canister enough time to start the chemical reaction. Something that has not been stated clearly is the type of diving one does on a partially used canister. While some say don't use it past 24 hours, others say it's ok to use it much, much later (like years...lol) but aren't saying the type of diving they are doing. If one is doing deep, long, or cold dives, it's obvious a fresh fill is in order. Something to the other end of the spectrum can be more accomodating to a partially used canister. __________________ Far better it is to dare mighty things, to win glorious triumphs, even though checked by failure, than to take rank with those poor spirits who neither enjoy much nor suffer much, because they live in the gray twilight that knows not victory or defeat.
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10th February 2007, 15:06	#22 (permalink)
Dutchy SK#007 Current Rebreather/s: Sport Kiss Other Rebreather/s: Join Date: Apr 2006 Location: Nieuwegein (The Netherlands) Posts: 724	Re: How long can absorbent be stored?! Quote: (Originally Posted by PacketSniffer) This statement is very important since one doesn't have the benefit of the activator any longer. What activator? If you are referring to the NaOH as an activator then that's not true. Although the NaOH is used in the second reaction step it is returned in the third reaction step. It is not used at all. If you were referring to water as the activator then that's used indeed, but (only slightly) more is produced as a result of the reaction. What is it that you designate as activator? __________________ = This post is environmentally friendly. It is composed of 100% recycled electrons only. = SK #007
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10th February 2007, 15:51	#23 (permalink)
PacketSniffer ~~~~~ #417 ~~~~~ Current Rebreather/s: Megalodon Other Rebreather/s: Join Date: Jun 2006 Location: Houston Posts: 432	Re: How long can absorbent be stored?! Quote: (Originally Posted by Dutchy) What activator? If you are referring to the NaOH as an activator then that's not true. Although the NaOH is used in the second reaction step it is returned in the third reaction step. It is not used at all. If you were referring to water as the activator then that's used indeed, but (only slightly) more is produced as a result of the reaction. What is it that you designate as activator? If I understand it correctly, in soda lime, potassium hydroxide [KOH] is used as an activator. If using a partially used canister, it is no longer present due to the continued but diminishing chemical reaction that continues from the moment one stops breathing the loop from their dive. So, when one uses a partially used canister, it is important to ensure a fair amount of time for pre-breathing the unit since you don't have the aid of KOH. For me, at this point in time, it is not so important to know how the process works as it is to know that there is a danger in not pre-breathing adequately a partially used canister. However, that does not mean I am not interested in the details. I continue to absorb as much information as I can comprehend and continue to seek these answers as I move forward in the never ending quest for experience in this fascinating sport. Please enlighten me if I don't have the details correct. Cheers __________________ Far better it is to dare mighty things, to win glorious triumphs, even though checked by failure, than to take rank with those poor spirits who neither enjoy much nor suffer much, because they live in the gray twilight that knows not victory or defeat. Last edited by PacketSniffer : 10th February 2007 at 15:53.
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10th February 2007, 17:40	#24 (permalink)
Gill Envy Shearwater Copis Diver Current Rebreather/s: Other CCR Other Rebreather/s: Evolution Other CCR Join Date: Nov 2005 Location: seattle Posts: 1,302	Re: How long can absorbent be stored?! Quote: (Originally Posted by nigelh) After a day's diving I strip the rig, clean it, dry the head out, put it back together and close it up. I assume the scrubber material will last longer than the oxygen cells, probably longer than the regulators. If my next dive is another short one I carry on using the same stuff but if it is a big one or a day trip I reload it. The chemistry is too simple to degenerate, well unless you flooded the thing. Nigel, not sure if i'm reading your post right. I was doing pretty much the same thing, cleaning, re-assembling, until it dawned on me that the spring in the scrubber could get fatigued over time that way. Since the spring is one of the more important pieces for avoiding chanelling, i decided to start leaving the scrubber out. Eventually, and perhaps more importantly, I realized the main o-ring in the head could get flattened if i left the bucket on the head. Now i pretty much leave every part of the loop un-assembled (withing reason) if there are many days inbetween dives to keep all the O-rings in tip top shape. __________________ Gill Envy ...Because I wasn't born with gills! ><(°>><(°>><(°>><(°>><(°>><(°>><(°>><(°>
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10th February 2007, 17:52	#25 (permalink)
jptaylor9 Member Current Rebreather/s: Inspiration Vision Other Rebreather/s: Inspiration Classic Join Date: Feb 2005 Location: London, UK Posts: 312	Re: How long can absorbent be stored?! Quote: (Originally Posted by Gill Envy) Nigel, not sure if i'm reading your post right. I was doing pretty much the same thing, cleaning, re-assembling, until it dawned on me that the spring in the scrubber could get fatigued over time that way. Since the spring is one of the more important pieces for avoiding chanelling, i decided to start leaving the scrubber out. Eventually, and perhaps more importantly, I realized the main o-ring in the head could get flattened if i left the bucket on the head. Now i pretty much leave every part of the loop un-assembled (withing reason) if there are many days inbetween dives to keep all the O-rings in tip top shape. Have you spoken to anyone at AP about this? Just wondered what the factory view was?
(Online)

10th February 2007, 17:55	#26 (permalink)
Gill Envy Shearwater Copis Diver Current Rebreather/s: Other CCR Other Rebreather/s: Evolution Other CCR Join Date: Nov 2005 Location: seattle Posts: 1,302	Re: How long can absorbent be stored?! Quote: (Originally Posted by PacketSniffer) Yes. This statement is very important since one doesn't have the benefit of the activator any longer. It was used up when one starts the canister for the first time. This is why it is extremely important to pre-breathe a partially used canister in order to ensure you've given the canister enough time to start the chemical reaction. Something that has not been stated clearly is the type of diving one does on a partially used canister. While some say don't use it past 24 hours, others say it's ok to use it much, much later (like years...lol) but aren't saying the type of diving they are doing. If one is doing deep, long, or cold dives, it's obvious a fresh fill is in order. Something to the other end of the spectrum can be more accomodating to a partially used canister. I was instructed to leave the scrubber out to dry for 8 hours, to get excess moisture out and then bag it, to retain the rest of the moisture, which i'm told is more important an issue than keeping it sealed to avoid co2 exposure, as very little co2 will ever go through it passively. Scrubber seems to not change at all with time, years might actually be acurate, but don't push it too hard, your life is more valuable than a fill, i get very leery after a couple of weeks. My general rule of thumb: don't re-use after a dive deeper than recreational limits, best to chuck it, since the reactant front has gone deeper into the stack and is now hard to predict in terms of distance to breakthrough. If i'm doing a deeper dive than previous, i chuck it... I do succesively shallower dives, to err on the side of narrower reactant fronts. This is all assuming that you stay within the time limits allowable for each depth, which is about as complicated to be totally sure of as decompression... the temp stick helps me cross check my guestimation (though i don't rely on it to push the limits, if it shows me a more conservative limit than i have sermized, i stick to that). And as PacketSniffer said so well, "If one is doing deep, long, or cold dives, it's obvious a fresh fill is in order. Something to the other end of the spectrum can be more accomodating to a partially used canister." accept that all of our dives are in relatively cold water (45-55 f). __________________ Gill Envy ...Because I wasn't born with gills! ><(°>><(°>><(°>><(°>><(°>><(°>><(°>><(°> Last edited by Gill Envy : 10th February 2007 at 17:57.
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10th February 2007, 18:01	#27 (permalink)
Gill Envy Shearwater Copis Diver Current Rebreather/s: Other CCR Other Rebreather/s: Evolution Other CCR Join Date: Nov 2005 Location: seattle Posts: 1,302	Re: How long can absorbent be stored?! Quote: (Originally Posted by jptaylor9) Have you spoken to anyone at AP about this? Just wondered what the factory view was? just checked with the wife, we both remember this being a recommendation during our mod1. I'm thinking tino re-iterated this in one of his threads, i might be wrong about who's post it was. Like anything you read on the inernet, if you like an idea, it's best to concur with one of your gurus or with the wonderful and most gracious Nickey at AP before putting it into action. Not joking, Nickey is very helpful, although with respect to scrubber recommendations, i think she has to follow the book on that one. __________________ Gill Envy ...Because I wasn't born with gills! ><(°>><(°>><(°>><(°>><(°>><(°>><(°>><(°>
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10th February 2007, 18:13	#28 (permalink)
PacketSniffer ~~~~~ #417 ~~~~~ Current Rebreather/s: Megalodon Other Rebreather/s: Join Date: Jun 2006 Location: Houston Posts: 432	Re: How long can absorbent be stored?! Quote: (Originally Posted by Gill Envy) And as PacketSniffer said so well, "If one is doing deep, long, or cold dives, it's obvious a fresh fill is in order. Something to the other end of the spectrum can be more accomodating to a partially used canister." accept that all of our dives are in relatively cold water (45-55 f). And that is what I was getting at. People chime in from all over the world with their answers. But, often a piece of the answer is missing; in this case the environment. So we get all of these answers that are different. For you guys in the frigid water, most probably change it every dive regardless of time left on it vs. maybe someone from Hawaii who might be able to use the same fill a few times during the course of a week assuming they didn't go over the mfg. suggested accumulated time. Quote: (Originally Posted by Gill Envy) My general rule of thumb: don't re-use after a dive deeper than recreational limits, best to chuck it, since the reactant front has gone deeper into the stack and is now hard to predict in terms of distance to breakthrough. This is another excellent point to make. Because as one example I've seen has shown is that the reactionary front gets very wide (in the stack length-wise) as it makes it's way to the end of the canister. So, the more spent it is, I would surmise the less reliable the absorbent may become for a partially used canister to be used again to exhaust it to its mfg suggested accumulated time. Where is the gentlemen from Molecular Products? __________________ Far better it is to dare mighty things, to win glorious triumphs, even though checked by failure, than to take rank with those poor spirits who neither enjoy much nor suffer much, because they live in the gray twilight that knows not victory or defeat. Last edited by PacketSniffer : 10th February 2007 at 18:18. Reason: Clarity
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10th February 2007, 21:17	#29 (permalink)
Dutchy SK#007 Current Rebreather/s: Sport Kiss Other Rebreather/s: Join Date: Apr 2006 Location: Nieuwegein (The Netherlands) Posts: 724	Re: How long can absorbent be stored?! Quote: (Originally Posted by PacketSniffer) If I understand it correctly, in soda lime, potassium hydroxide [KOH] is used as an activator. If that is what you call the activator then that makes it clearer. Chemists will say that Potassium and Sodium are very much interchangably in many (nearly all) chemical reactions (Medics should disregard this sentence they know differently for their domain ) In both cases it isn't used up. If there's truth in what you write then it must be though another mechanism e.g. less accesible because of bein enclose in the resulting calcium carbonate. I'll not dismiss the alleged effect just suggested mechanism. In the absence of facts I guess it's good to continue the good habit of prebreathing... [/quote] __________________ = This post is environmentally friendly. It is composed of 100% recycled electrons only. = SK #007
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10th February 2007, 21:27	#30 (permalink)
PacketSniffer ~~~~~ #417 ~~~~~ Current Rebreather/s: Megalodon Other Rebreather/s: Join Date: Jun 2006 Location: Houston Posts: 432	Re: How long can absorbent be stored?! Quote: (Originally Posted by Dutchy) <snip>If there's truth in what you write then it must be though another mechanism e.g. less accesible because of bein enclose in the resulting calcium carbonate. I'll not dismiss the alleged effect just suggested mechanism. In the absence of facts I guess it's good to continue the good habit of prebreathing... [/quote] I was taught this by my Instructor. Subsequently, I did find the text that does explain it which is written by Joerg Hess, M.S. for that particular chapter. Please see IANTD Tek Closed Circuit Rebreather manual on page 51 & 52. __________________ Far better it is to dare mighty things, to win glorious triumphs, even though checked by failure, than to take rank with those poor spirits who neither enjoy much nor suffer much, because they live in the gray twilight that knows not victory or defeat.
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