How long will you let the scrubber sit

[matt]

Perhaps some reading on the topic would help understand what moisture means for Sofnolime:

http://www.molecularproducts.com/pd...echnical Article Sofnolime 2550 USP Grade.pdf

http://www.molecularproducts.com/pdf/Sofnolime 2550 USP Version 9 Feb 2010.pdf

AFAIK from my reading the moisture is chemically part of the material, it's not water sat on the surface and cannot be replaced by soaking and is nothing to do with being used in a humid environment.

Personally if I had not used a packed scrubber I'd return it to the tub. If used then I'll bin it to clean the unit at the end of the trip.

Matt.

 

[gianaameri]

Perhaps some reading on the topic would help understand what moisture means for Sofnolime:

http://www.molecularproducts.com/pd...echnical Article Sofnolime 2550 USP Grade.pdf

http://www.molecularproducts.com/pdf/Sofnolime 2550 USP Version 9 Feb 2010.pdf

AFAIK from my reading the moisture is chemically part of the material, it's not water sat on the surface and cannot be replaced by soaking and is nothing to do with being used in a humid environment.

Personally if I had not used a packed scrubber I'd return it to the tub. If used then I'll bin it to clean the unit at the end of the trip.

Matt.

Absolutely correct.

I never intended to suggest that moisture could be replaced by soaking, and this I stress for the avoidance any doubt.

My purpose of soaking was to stress the Sofnolime to mimic in a rudimentary way the conditions of very long storage of a used scrubber as some were suggesting it is O.K. to re-use a part used scrubber after very long storage (14 days according to rEVO, 1 year according to Dave, forever according to Hannsing).

My personal limit is what my instructor (the most conservative) told me and it is 3 days maximum after initial use (so Day 1 I fill and use, and Day 3 to the very latest it is binned after use).

 

[matt]

I don't think any real testing has been done on used scrubber material so a cautious approach like Gian suggests works for me.

Matt.

PS I've no idea why I decided to post in the JJ section, this seems totally unrelated to JJ.

 

[lizardland]

I don't think any real testing has been done on used scrubber material so a cautious approach like Gian suggests works for me.

Matt.

PS I've no idea why I decided to post in the JJ section, this seems totally unrelated to JJ.

There is an old Canadian defence study on storing part-used scrubbers.

 

[matt]

There is an old Canadian defence study on storing part-used scrubbers.

I think the link was posted recently elsewhere, but I didn't get chance to follow it. What's the summary?

 

[Garspeed]

I think the link was posted recently elsewhere, but I didn't get chance to follow it. What's the summary?

Matt

I posted in Inspo forum, safe after 7 days of storage but not tested beyond this figure as that was all they were interested in. Settlement due to vibration seemed to be a bigget concern though.

Cheers
Gar

 

[Andy T]

Then I shall soak some in washing up liquid, carry it around in my underwear for a fortnight, mix it with some Moroccan spices and if it still smokes well after all that will dive a fresh fill and put the experimental one in a hookah...

It has as much validity as yours but with extra fun added...


BTW freezing lime is a bad idea, you didn't need to experiment to find that out, it is known....

An ingenious experiment Sir. We look forward to reading about the results.

 

[matt]

Matt

I posted in Inspo forum, safe after 7 days of storage but not tested beyond this figure as that was all they were interested in. Settlement due to vibration seemed to be a bigget concern though.

Cheers
Gar

Thanks! I'd be happy with 7 days too, but at the end of the trip (usually no more than 14 days) I'd bin it. 3 days is aggressive, but sensible, sorb is cheap.

Matt.

 

[Andy T]

My purpose of soaking was to stress the Sofnolime to mimic in a rudimentary way the conditions of very long storage of a used scrubber as some were suggesting it is O.K.

Immersing scrubber media in water in no way mimics long storage.

Sorb is a mixture of calcium hydroxide and sodium hydroxide. The calcium hydroxide is sparingly soluble in water and the sodium hydroxide is readily soluble. If you add water you will simply get a nasty caustic solution, with most of the calcium hydroxide not dissolving. When you pour off the liquid to recover the solid material you will remove much the the sodium hydroxide and this will stop or greatly impair the material from absorbing carbon dioxide.

As others have already pointed out, fresh sorb contains a significant about of water. The main concern around storing sorb is the loss of this water, a secondary concern is if it is exposed to any carbon dioxide during storage. Fresh sorb in an air tight container should be good until the manufacturer's expiry. In makes no difference if the air tight container is the original keg, or a scrubber in a plastic bag.

Storage of used sorb is another matter. Personally I leave the rebreather with the hoses off over night in an air conditioned room, to allow excess condensation to dry. Then I replace the hoses and close the BOV. Typically it gets left like this for 1 to 2 weeks, but it has been up to two months without any issues. I am not saying this is safe, or best practice, simply that it is what I routinely do and so far it has worked for me.

One very important point when storing used sorb is to remember that it must never be taken out of the scrubber. Unpacking sorb to dry it is very dangerous and will expose you to a very high risk of a CO2 hit.

 

[gianaameri]

Immersing scrubber media in water in no way mimics long storage.

Sorb is a mixture of calcium hydroxide and sodium hydroxide. The calcium hydroxide is sparingly soluble in water and the sodium hydroxide is readily soluble. If you add water you will simply get a nasty caustic solution, with most of the calcium hydroxide not dissolving. When you pour off the liquid to recover the solid material you will remove much the the sodium hydroxide and this will stop or greatly impair the material from absorbing carbon dioxide.

As others have already pointed out, fresh sorb contains a significant about of water. The main concern around storing sorb is the loss of this water, a secondary concern is if it is exposed to any carbon dioxide during storage. Fresh sorb in an air tight container should be good until the manufacturer's expiry. In makes no difference if the air tight container is the original keg, or a scrubber in a plastic bag.

Storage of used sorb is another matter. Personally I leave the rebreather with the hoses off over night in an air conditioned room, to allow excess condensation to dry. Then I replace the hoses and close the BOV. Typically it gets left like this for 1 to 2 weeks, but it has been up to two months without any issues. I am not saying this is safe, or best practice, simply that it is what I routinely do and so far it has worked for me.

One very important point when storing used sorb is to remember that it must never be taken out of the scrubber. Unpacking sorb to dry it is very dangerous and will expose you to a very high risk of a CO2 hit.

I suspected as much which is why storing used sorb (wet, lumpy, phlegm, and all the stuff with normally lives happily in mouth, throat, and lungs...) for a "long" time is not the prudent course of action.

So, I used to change scrubber every 5 - 6 days, and after a near death experience extending that limit, I now change after maximum 3 days of use.

There is no scientific basis in the suggestions in this thread that 15 days, 1 year, forever... is safe or fine.

Given the price of Sorb relative to the value of life, and given that we don't know what is the safe limit, it is reckless to encourage NOT replacing your Sorb after use other than doing so "frequently and regularly."

My thoughts... no science behind it, just common sense and prudence.

 

[matt]

Good post, few comments:

As others have already pointed out, fresh sorb contains a significant about of water.

Target is 19% in manufacture, at least 10% is needed for a good reaction and below 5% there are stated problems with efficacy.

The main concern around storing sorb is the loss of this water, a secondary concern is if it is exposed to any carbon dioxide during storage. Fresh sorb in an air tight container should be good until the manufacturer's expiry. In makes no difference if the air tight container is the original keg, or a scrubber in a plastic bag.

AFAIK and after much discussion it transpires that the plastic keg allows water to evaporate out and that this is the main driver for the use-by date.

Matt.

 

[Bythesea]

My thoughts... no science behind it, just common sense and prudence.

Really or is it just paranoia mixed with limited understanding?

 

[gianaameri]

Really or is it just paranoia mixed with limited understanding?

I do not dispute I/we do not know.

I believe it is prudence having accepted I/we do not know, but call it "paranoia with limited understanding" if that is what makes you happy (and store the scrubber "forever" if that is what you chose to do).

Gotta get my rebreather ready now and fill the scrubber!

 

[matt]

Really or is it just paranoia mixed with limited understanding?

Actually I'm with Gian. Common sense says to me that you don't risk you're life for a tenner. No need to chuck unused material in the bin, but no need to roll the dice either.

Matt.

 

[Bythesea]

Actually I'm with Gian. Common sense says to me that you don't risk you're life for a tenner. No need to chuck unused material in the bin, but no need to roll the dice either.

Matt.

Agreed but the moment it was suggested as a test to soak the lime in fresh water for a few days all credibility was lost IMO....

That is what I referred to with the words limited understanding, even my high school grasp of chemistry tells me that is a non starter....

If the Lime is in the scrubber and not sat exposed in warm, dry conditions it will retain an acceptable moisture content, that is science right there...

It is no different to it being sat in the plastic container it comes in...

Time will tell I guess, in my scrubber is a fill from two weeks ago, it has just under an hour on it.... I will report back tomorrow..... or not....

 

[matt]

Agreed but the moment it was suggested as a test to soak the lime in fresh water for a few days all credibility was lost IMO....

Fair point, it as a bit whacky!

Time will tell I guess, in my scrubber is a fill from two weeks ago, it has just under an hour on it.... I will report back tomorrow..... or not....

I'd say that's fine, but I wouldn't try putting 3 hrs at 60m on it !

Matt.

 

[gianaameri]

This thread has been truly inspirational.

I started the testing last night.

When filling the scrubber I put a little bit of fresh Sofnolime in a plastic jug. Then, later, added a small amount of fresh tap water to simulate what would happen inside a rebreather (in a grossly rudimentary and unscientific way).

Drained any excess water, Sofnolime very well wet like on the bottom of a Scrubber (radial,, or top of the Scrubber like in some axials), sealed it in a bag, and left it overnight.

With surprise, I found this morning the lot was drier and the Sofnolime appears to have swollen... so some kind of reaction took place despite the lot being sealed in a bag.

I have now left it to dry and tonight will test to see if the Sofnolime is still reactive to CO2.

I put the records of the test on my site CO2 Absorbent section (Wilbo edit: should you choose to register).

Maybe somebody more scientific and technical than I already has an explanation as to the reasons for the swelling.

Off diving!

 

[Bythesea]

 

[lizardland]

Last night, fueled by red wine and the naughty bits in Lip Service, I put some petrol in a bucket. I left it three hours then dropped a match on it... what do you know?

Results uploaded here : http://3.bp.blogspot.com/-7H2NGXhI9ms/TdLwpzzg88I/AAAAAAAAAIA/gcDdqTkeJkY/s1600/burnt+house.jpg

 

[plazma]

This thread has been truly inspirational.

I started the testing last night.

When filling the scrubber I put a little bit of fresh Sofnolime in a plastic jug. Then, later, added a small amount of fresh tap water to simulate what would happen inside a rebreather (in a grossly rudimentary and unscientific way).

Drained any excess water, Sofnolime very well wet like on the bottom of a Scrubber (radial,, or top of the Scrubber like in some axials), sealed it in a bag, and left it overnight.

This would simulate flooding and that would mean binning the scrubber after the dive. My scrubber have newer been soaking wet. Water vapor from breathing is totally different than pouring liquid water.

With surprise, I found this morning the lot was drier and the Sofnolime appears to have swollen... so some kind of reaction took place despite the lot being sealed in a bag.

It's a known fact sofnolime swells with water. Used scrubber is more tightly packed because of this. Flooding the scrubber may also cause the wob to increase because of moisture swelling. This is one more reason to bin the flooded scrubber after the dive.

I have now left it to dry and tonight will test to see if the Sofnolime is still reactive to CO2.

I put the records of the test on .. CO2 Absorbent section.

Maybe somebody more scientific and technical than I already has an explanation as to the reasons for the swelling.

Whatever the result it is not very meaningful. Pouring liquid water does not anyway simulate using a scrubber a normal way nor does leaving it to dry.