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View Full Version : Unused fill - How long to keep?



Jase
31-12-2012, 06:42 PM
So, new fill added last night. Pre breathe to check all well (Cells, Temp stick, Taste, Feel Etc).

Dive aborted prior to leaving this morning. No chance of diving (even in a pool) the next few days.

What's the consensus here? Bin it now or good enough for next year!

Jase

matt
31-12-2012, 07:04 PM
Forever. Unless it's your lunchbox we're talking about - best to unpack that today!

Sorb - I'd return it to the tub and repack next time.

Matt.

Barrygoss
31-12-2012, 07:09 PM
Damn, no thanks button... :)
It's a chemical reaction started and continued by CO2. Until enough CO2 has passed over it, it's not finished.
No CO2, no reaction and the lime is in stasis.

B

matt
31-12-2012, 07:16 PM
-> http://i1214.photobucket.com/albums/cc497/MatthewOutram/TDF/thanksbutton_zps5e3e5aa6.png

Darren A
31-12-2012, 07:23 PM
-> http://i1214.photobucket.com/albums/cc497/MatthewOutram/TDF/thanksbutton_zps5e3e5aa6.png

Where's that button then? Can't see it.

Barrygoss
31-12-2012, 07:32 PM
Where's that button then? Can't see it.

Methinks he's trolling for greens, instead ;)

Oh, and I'd not bother to repack the fill. Seal the unit up and park it in the garage. Ready to go for next time.

B

Logun
31-12-2012, 07:33 PM
Methinks he's trolling for greens, instead ;)

Does that mean hes asking for reds? :D

matt
31-12-2012, 07:53 PM
Methinks he's trolling for greens, instead ;)

Oh, and I'd not bother to repack the fill. Seal the unit up and park it in the garage. Ready to go for next time.

B

Trolling, bahf. ;)

Matt.

http://i1214.photobucket.com/albums/cc497/MatthewOutram/TDF/thanksbutton_zps5e3e5aa6.png

Darren A
31-12-2012, 07:55 PM
Does that mean hes asking for reds? :D

Everyone is dishing out greys at the the moment aren't they?

Soggy
31-12-2012, 08:07 PM
I wouldn't worry aout the fill, leave the unit sealed up and then dive it.

Jase
31-12-2012, 08:16 PM
I wouldn't worry aout the fill, leave the unit sealed up and then dive it.

Yeah, that was my thinking actually. Left one before for a few days and even used a part used one for a pool session but never had one with just a Pre breathe not used. Thought if I leave unit sealed, no problems, but as I have breathed it surely I have contaminated it and really need to clean it? 8 fill against my life isn't really the issue, just grates!

So options are...

1. Bin it.
2. Tip back in container.
3. Seal scrubber.
4. Leave as is.

What to do!

Jase

Hot Totty
31-12-2012, 08:20 PM
Me I take stack out put in placcy bag until I want it ;)

matt
31-12-2012, 08:22 PM
Yeah, that was my thinking actually. Left one before for a few days and even used a part used one for a pool session but never had one with just a Pre breathe not used. Thought if I leave unit sealed, no problems, but as I have breathed it surely I have contaminated it and really need to clean it? 8 fill against my life isn't really the issue, just grates!

So options are...

1. Bin it.
2. Tip back in container.
3. Seal scrubber.
4. Leave as is.

What to do!

Jase

2.

I don't suggest tipping it back in the keg just for fun. I suggest it so that you are completely sure what's in the stack when you next need it. I keep my fresh sorb in the keg and the old in the bin. I don't have a half-way-house. Then again I am an anal ☺☺☺☺, YMMV.

Cheers
Matt.

johnny boy
31-12-2012, 08:34 PM
5. Give it to Brian

Jase
31-12-2012, 08:36 PM
5. Give it to Brian

Goddard?

Soggy
31-12-2012, 09:20 PM
2.

I don't suggest tipping it back in the keg just for fun. I suggest it so that you are completely sure what's in the stack when you next need it. I keep my fresh sorb in the keg and the old in the bin. I don't have a half-way-house. Then again I am an anal ☺☺☺☺, YMMV.


tape and a marker pen, should do the trick. Date filled and hours on stack.

One of the handy things with a sentinel is that when you reset the timer/monitor on the stack, when you refill the stack, it tells you what you have left on the stack. I tend to always fully prep the unit from start to finish, so refill stack and prep unit, then if i don't dive it gets stored as good-to-go.

matt
31-12-2012, 09:33 PM
I once dived with someone who prep'd there unit 7 days in advance. When they jumped in the observant skipper noticed immediately that there was a problem. He didn't know what - but he knew there was a problem. The diver later reported that at 2-3m they knew they didn't have much time left. They came abruptly to the surface. Luckily the loop dropped from their mouth as they broke the surface, or the ending could have been a little different.

On getting out the kit was inspected - no scrubber. Clean forgot to fit it as the lime was not available when the kit was assembled.

Since then my kit is either diving or disassembled.

I accept I'm peculiar :-)

Matt.

Soggy
31-12-2012, 09:47 PM
I once dived with someone who prep'd there unit 7 days in advance. When they jumped in the observant skipper noticed immediately that there was a problem. He didn't know what - but he knew there was a problem. The diver later reported that at 2-3m they knew they didn't have much time left. They came abruptly to the surface. Luckily the loop dropped from their mouth as they broke the surface, or the ending could have been a little different.

On getting out the kit was inspected - no scrubber. Clean forgot to fit it as the lime was not available when the kit was assembled.

I'd wonder how he prepped his kit, mine is start to finish with no distractions, if you prep it one friday from end to end then why would the scrubber me missing 1,2 or 7 days later. That sounds to me more like bad prep.

I guess we each have our very anal ways of prepping units, I know i'm very anal start to finish and that includes my start up routine on the boat. I've been known to tell the odd club member to "feck off" when they've tried talking to me while i'm kitting up =D

Hot Totty
31-12-2012, 09:48 PM
I'd wonder how he prepped his kit, mine is start to finish with no distractions, if you prep it one friday from end to end then why would the scrubber me missing 1,2 or 7 days later. That sounds to me more like bad prep.

I guess we each have our very anal ways of prepping units, I know i'm very anal start to finish and that includes my start up routine on the boat. I've been known to tell the odd club member to "feck off" when they've tried talking to me while i'm kitting up =D

+1

matt
31-12-2012, 10:03 PM
I'd wonder how he prepped his kit, mine is start to finish with no distractions, if you prep it one friday from end to end then why would the scrubber me missing 1,2 or 7 days later. That sounds to me more like bad prep.

I guess we each have our very anal ways of prepping units, I know i'm very anal start to finish and that includes my start up routine on the boat. I've been known to tell the odd club member to "feck off" when they've tried talking to me while i'm kitting up =D

Yes - we all said at the time "how could that happen". But it did. And he's a good diver - fastidious. I too would tell you to feck off if I was in the middle of prepping the unit.

Matt.

Ruffy
31-12-2012, 10:12 PM
Not notice anything during the pre-breath??

Soggy
31-12-2012, 10:17 PM
Not notice anything during the pre-breath??

depends on how long your pre-breath is and how good you do it.

Mister Mike
31-12-2012, 10:54 PM
This would be picked up by the C02 sensor , coming soon from APD for fitment to Vision units.

matt
31-12-2012, 11:18 PM
It was a meg.

nickb
01-01-2013, 09:46 AM
Not notice anything during the pre-breath??Most pre-breathes I witness probably wouldn't reveal a missing scrubber. Most of mine too if I'm being honest.

matt
01-01-2013, 09:49 AM
Most pre-breathes I witness probably wouldn't reveal a missing scrubber. Most of mine too if I'm being honest.

I'm convinced that break-through will not be detected on the bench. The pre-breath does nothing, IMHO, but check that the system is working - cells good, alarms working, and for me that the temp-stick comes up (so scrubber working, to some extent). I used to do 10 min pre-breath, but now 3 mins is OK for me.

Matt.

Soggy
01-01-2013, 10:16 AM
I'm convinced that break-through will not be detected on the bench. The pre-breath does nothing, IMHO, but check that the system is working - cells good, alarms working, and for me that the temp-stick comes up (so scrubber working, to some extent). I used to do 10 min pre-breath, but now 3 mins is OK for me.


Mine a 5 minute pre-breath cos thats what the timer says, contrarty to popular belief its not onerous and ive never found it to be an issue as long as your prep routine allows for it. I'm much the same, i use the pre-breather to make sure everything comes up to speed, cells moving, and temp-stick comes on and the scrubber sees some sort of heating movement.

One thing i've always tend to notice is everyone does more than a 3 minute pre-breath. Its not often i see someone kit up a unit on a hardboat and jump straight in, usually your sat for a few minutes while the skipper sorts out shots and checks the tide.

Janos
01-01-2013, 10:36 AM
If it's a brand new scrubber, then I'd either seal it - in the unit, or in a carrier bag. I'd be happy leaving this for around a month or so. More than that and there's something wrong with my diving!

Janos

Hot Totty
01-01-2013, 10:37 AM
Tend to be a case of per breathe then once on the loop generally stay on the loop, so my prebreathe can be anything from 5mins to 20mins, if I'm still sitting after that the skippers fucked the shot/slack up ;)

Simon TW
01-01-2013, 10:40 AM
Matt I think I know to whom you refer, Meg instructor?

I often leave a part used scrubber for a month or so. I wrap it in cling film first and then seal it in a bag.

Garf
01-01-2013, 10:44 AM
Since then my kit is either diving or disassembled.

I accept I'm peculiar :-)

Matt.

Well, yes, you are. However, that doesn't stop it from being good advice :)

Soggy
01-01-2013, 10:57 AM
I often leave a part used scrubber for a month or so. I wrap it in cling film first and then seal it in a bag.

whats the cut-off point for you ditching that part used scrubber?

matt
01-01-2013, 11:10 AM
Well, yes, you are. However, that doesn't stop it from being good advice :)

:D


Matt I think I know to whom you refer, Meg instructor?

I often leave a part used scrubber for a month or so. I wrap it in cling film first and then seal it in a bag.

Probably you do, Simon. ;-)

Janos
01-01-2013, 11:15 AM
whats the cut-off point for you ditching that part used scrubber?

For me it's more than a couple of weeks, mainly because of the logistics of my diving.

- I start a deep dive with a new scrubber
- I start a weekend or longer trip with a new scrubber - just because of the logistics

So I'll only re-use a scrubber if I've done a couple of 45min dives in a day, and then I'm going to do something similar. So this means either for a day trip with the club to (say) Brighton where we'll do a wreck and a drift, or a day in a quarry.

This leads me binning quite a few part-used scrubbers, and given you're only saving 4 or so, I tend to bin it more often than not.

Janos

matt
01-01-2013, 12:02 PM
whats the cut-off point for you ditching that part used scrubber?

For me, I ditch if I open the unit. Life is too short to worry about a pints worth of lime. If the unit is good for another dive I leave it on the bench. If I want to dry it/clean it/fettle it - new scrubber.

Matt.

the diving tiler
01-01-2013, 12:19 PM
Sometimes I leave my unused lime in the unit for 8 weeks due to shite weather. I dont use part used scrubber unless its same day diving, then its only 30 or 40m dives on the day.

mark vaughan
02-01-2013, 08:33 PM
The cost of the lime does not bother me, as most of the time we spend 40 to 50 to go out on a charter to enjoy dive where i do not want that little devil on my shoulder playing with my mind could i get a CO2 hit , bin the lime and have a good time , what we must remember we do not do dive for 30 minute bottom times most after at least a hour long and with a bit of deco could be run time of 90 mins and higher.

For sure if i am doing a 50 mtr dive for 45 mins ,the run time could be 120mins fresh lime every time no matter what i have done with it prior or not, its iver that or breathing 150ltrs per minute
plus on bailout if you can get on it.

steve6690
02-01-2013, 08:44 PM
I wouldn't worry aout the fill, leave the unit sealed up and then dive it.

Is what I did after an abortive day last september. Sealed in a tub or sealed in a unit....

Sent from my GT-I9300 using Tapatalk 2

Major Clanger
04-01-2013, 02:42 PM
It was a meg.

Had he turned it on 7 days in advance as well? How could someone miss there not being a scrubber, having to take the head off to start it. Gob smacking really and I'm not usually too critical of these things.

matt
04-01-2013, 02:48 PM
Had he turned it on 7 days in advance as well? How could someone miss there not being a scrubber, having to take the head off to start it. Gob smacking really and I'm not usually too critical of these things.

To me it's a simple procedural mistake. I would never assemble the unit in advance of a dive like this and if I had I would dismantle it when I knew my dive was postponed. IMHO this mishap happened because no particular procedure was being followed - just doing the best on the day then going for a beer expecting to dive tomorrow when I'll remember the scrubber is not fitted.

I don't use a check list, but I do follow my method each time. And if I am distracted - I start over. Many times I have wondered - whilst that guy was distracting me did I really put the o-ring in? I'll immediately go back to the boat and strip and start over. It keeps me up at night not to.

YMMV.

Matt.

dlk
04-01-2013, 02:56 PM
I've always thought I'd keel over on a 5 min pre-breathe without the scrubber.
Who's tried it?

Major Clanger
04-01-2013, 02:57 PM
To me it's a simple procedural mistake. I would never assemble the unit in advance of a dive like this and if I had I would dismantle it when I knew my dive was postponed. IMHO this mishap happened because no particular procedure was being followed - just doing the best on the day then going for a beer expecting to dive tomorrow when I'll remember the scrubber is not fitted.

I don't use a check list, but I do follow my method each time. And if I am distracted - I start over. Many times I have wondered - whilst that guy was distracting me did I really put the o-ring in? I'll immediately go back to the boat and strip and start over. It keeps me up at night not to.

YMMV.

Matt.

A procedural mistake may have been the start of the problem but how does anyone miss the big white thing that the big black thing plugs in to after powering up. Must have been having a really off day.

matt
04-01-2013, 05:17 PM
I've always thought I'd keel over on a 5 min pre-breathe without the scrubber.
Who's tried it?

This is not true unless you start some exercise. From what I have observed sat on the bench all is well and good but it's the swim to the shot that gets you.

Matt.

matt
04-01-2013, 05:23 PM
A procedural mistake may have been the start of the problem but how does anyone miss the big white thing that the big black thing plugs in to after powering up. Must have been having a really off day.

I haven't followed the argument...the unit, to all external appearances was ready to dive. The cannister was in but no lime was loaded. The intention was to prep the unit for a dive. Everything going smoothly until the realisation that the lime had not arrived on-site. Rather than abandoning the attempt the unit was still prep'd and strapped to the bench. The lime could be fitted tomorrow. 7 days later the lime had been forgotten and the diver was in the water minus the lime.

Matt.

Major Clanger
04-01-2013, 07:55 PM
I haven't followed the argument...the unit, to all external appearances was ready to dive. The cannister was in but no lime was loaded. The intention was to prep the unit for a dive. Everything going smoothly until the realisation that the lime had not arrived on-site. Rather than abandoning the attempt the unit was still prep'd and strapped to the bench. The lime could be fitted tomorrow. 7 days later the lime had been forgotten and the diver was in the water minus the lime.

Matt.

Ah with you now, when you said forgot to fit it, thought you meant the clear can and lime. Can now see how forgetting the fill may have occurred, though still quite a bit of an oversight (clanger).

matt
04-01-2013, 08:41 PM
Ah with you now, when you said forgot to fit it, thought you meant the clear can and lime. Can now see how forgetting the fill may have occurred, though still quite a bit of an oversight (clanger).

Some might say a Major Clanger!

Major Clanger
04-01-2013, 10:21 PM
Some might say a Major Clanger!

And therein lies the source of a name :)

BTS
04-01-2013, 10:34 PM
I've always thought I'd keel over on a 5 min pre-breathe without the scrubber.
Who's tried it?

I know someone who tried it under controlled conditions, I will get the time frame off him but he said he started hallucinating at 12% CO2

Baron015
05-01-2013, 12:12 AM
If it's a brand new scrubber, then I'd either seal it - in the unit, or in a carrier bag. I'd be happy leaving this for around a month or so. More than that and there's something wrong with my diving!

Janos

How important do you think is the carrier bag ? For a partially used scrubber which I intend to reuse, I tend just to take it out of the unit and put it on the shelf in the study (properly marked with remaining duration of course and date). I've got one on the shelf now from my last dive some time in earlyish December.

Not a lot of gas movement through the scrubber when on the shelf, so I always figured that it would be fine. Not had any problems this way, but would like to keep it that way as well !! I could start using a bag I guess.

Air cienu,
Tb.

Sent from my iPad using Tapatalk HD

Jase
05-01-2013, 01:41 AM
So,

From the OP, quite a considerable difference of opinion.

Personally, as the unit has been untouched the last week, I am gonna dive it as is in a puddle on Sunday (<20M). Remainder goes in the bin.

Can't see any CO2 has entered the unit as its been airtight since I pre-breathed it a week or so back. I'll flush the counter lungs through and do a good clean though as its been sat a week, tomorrow afternoon.

From the range of experience on here, no one has mentioned what they were taught on any courses they have undertaken....

Regards,

Jase

Marc_d
05-01-2013, 03:08 AM
I always answer this in my own head with " Is my life and the people in my life I would leave behind worth more than the 5 /6 pounds for a fresh scrubber fill ?"
Do you jump in thinking nice new scrubber all looking good or spend the dive wondering if you should have changed it not having 100% focus on the dive.

It's like people who jump in with half or less than full bail out cylinders on serious dives, isn't your life worth more than 3 /4 for a fill or top up ?

I once got in to dive the moldavia and a guy next to me had 2 x 11's Ali's on, and I thought great stick near him plenty of gas if needed on top of mine ( 2 x 11's) but not when his each had just 80 bar in.

Amazing, would you jump the traffic lights with one eye closed? Doubt it.

My 2p.

Scrubber kept for one to two weeks if blown out then repacked with having kept sealed in unit and all tests started again from scratch night before and on route to site. Anal but makes you feel good in the head.

matt
05-01-2013, 08:54 AM
How important do you think is the carrier bag ?

Probably stops any spills or other poop getting on it - but other than that not a lot, I reckon. Why don't you keep it in the unit in the shed with everything else?

Matt.

nickb
05-01-2013, 04:23 PM
I know someone who tried it under controlled conditions, I will get the time frame off him but he said he started hallucinating at 12% CO2Who was 'controlling it? How was this 12% measured?

Extreme and Dangerous CO2 Levels



slightly intoxicating, breathing and pulse rate increase, nausea: 30,000 ppm
above plus headaches and sight impairment: 50,000 ppm
unconscious, further exposure death: 100.000 ppm


By my arithmetic, that's 10%

Neil Brock
05-01-2013, 04:31 PM
slightly intoxicating, breathing and pulse rate increase, nausea: Looking at new motorbike
above plus headaches and sight impairment: Paying to run new motorbike
unconscious, further exposure death: When err indoors see's the cost of the bloody thing


By my arithmetic, that's Usualy 2-3 months

BTS
05-01-2013, 04:31 PM
Who was 'controlling it? How was this 12% measured?

Extreme and Dangerous CO2 Levels



slightly intoxicating, breathing and pulse rate increase, nausea: 30,000 ppm
above plus headaches and sight impairment: 50,000 ppm
unconscious, further exposure death: 100.000 ppm


By my arithmetic, that's 10%

He is a GP, he had a full medical team inc gasmen... I will get more details from him next time I see him...

nickb
05-01-2013, 04:41 PM
He is a GP, he had a full medical team inc gasmen... I will get more details from him next time I see him...I'd love to read the protocol for this. Find out where the results were published too and share that with us.

CO2 has a distinct smell, but it's not normally like bullshit ;)

iamyourgasman
05-01-2013, 06:41 PM
For the record, CO2 is an odourless and tasteless gas. Now smelling your own or even worse others breath is a different kettle of fish ;)

BTS
05-01-2013, 07:04 PM
I'd love to read the protocol for this. Find out where the results were published too and share that with us.


No protocol, no papers published, he just did it because he could, something to do on a Friday night if you will. Not everything in life needs to be fully documented to be true nick...

WFO
05-01-2013, 07:13 PM
So,

From the OP, quite a considerable difference of opinion.

Personally, as the unit has been untouched the last week, I am gonna dive it as is in a puddle on Sunday (<20M). Remainder goes in the bin.

Can't see any CO2 has entered the unit as its been airtight since I pre-breathed it a week or so back. I'll flush the counter lungs through and do a good clean though as its been sat a week, tomorrow afternoon.

From the range of experience on here, no one has mentioned what they were taught on any courses they have undertaken....

Regards,

Jase

I've no course things to add but remember reading a USN manual that basically said "it's fine", and the scrubbers we're talking about are a lot less aggressively used, and much more capable than the LAR-V scrubbers they were on about.

Jase
08-01-2013, 01:14 PM
So, for completeness, I thought I would post again.

Decided to keep unit intact until ready for use and then do a normal pre flight check prior to diving.

Dived the fill mentioned in the thread yesterday. 2 pretty steady dives @20M for around 50 or so minutes. Experienced no problems whatsoever.

Cleaned unit and disposed of fill upon return and everything was as expected.

For me, whilst this exercise would indicate that you can pre breathe a fill and then leave it a while before using, I generally won't. I certainly wouldn't tip it back in the tub, leave it any longer, take it out of the unit, put it in the fridge or indeed any other suggestion. As has been pointed out, we're talking about 8. This is however just my opinion.

Thanks for all the comments. I think what's been most interesting is that no one has said 'but on my course I was told this...'

Jase

Kermit
08-01-2013, 01:40 PM
I know someone who tried it under controlled conditions, I will get the time frame off him but he said he started hallucinating at 12% CO2
I tried it (dry) and I was gasping like a fish out of water before I even thought about hallucinating. Can't remember what the time was but I think it was somewhere between 3 and 5 minutes (ish).

Also tried with scrubber but no O2. At 0.1 bar I was bright blue but didn't feel too bad. I was stopped by my safety "diver" who was getting rather worried.

BTS
08-01-2013, 04:32 PM
I think what's been most interesting is that no one has said 'but on my course I was told this...'



Ok, on my course I was told this...

The reaction moves up the stack so lets say for example and the figures are made up for simplicity, for the first ten minutes of breathing all the CO2 is removed by the bottom inch of lime, this means the lime above that line is untouched and still offer full scrubbing capability.

This is how a temp stick works, it tracks where the heat is in the stack, where the heat is the reaction is, above this point will be cooler as there is less or no reaction taking place as there is less or no CO2 left in the gas...

In conclusion, yes you can pre breathe, you can do two dives over a weekend, say 1 @ 30M for an hour 1 @ 20M for an hour, leave it a week and go the next weekend for another hour at 20M....

What were you taught on your course?

BTS
08-01-2013, 04:34 PM
Also tried with scrubber but no O2. At 0.1 bar I was bright blue but didn't feel too bad. I was stopped by my safety "diver" who was getting rather worried.

Lack of O2 is supposed to be a pleasant, almost euphoric way to go....

Soggy
08-01-2013, 04:37 PM
Ok, on my course I was told this...

The reaction moves up the stack so lets say for example and the figures are made up for simplicity, for the first ten minutes of breathing all the CO2 is removed by the bottom inch of lime, this means the lime above that line is untouched and still offer full scrubbing capability.

This is how a temp stick works, it tracks where the heat is in the stack, where the heat is the reaction is, above this point will be cooler as there is less or no reaction taking place as there is less or no CO2 left in the gas...

In conclusion, yes you can pre breathe, you can do two dives over a weekend, say 1 @ 30M for an hour 1 @ 20M for an hour, leave it a week and go the next weekend for another hour at 20M....

What were you taught on your course?

I think someone on here has a great analogy (possibly Janos) about demons catching molecules. I understand that it starts with low density gas and it mostly caught at the bottom of the stack but gas does move past this and get caught higher up, thus the whole stack becomes warm. As you dive deeper the gas density increases and more gas passes the front of the stack and gets caught further back, then the front of the stack is exhausted and this line of exhausted material moves towards the top of the stack. So the whole stack works to remove CO2 but its the bottom thats worn out first and this worn out line moves towards the top of the stack.

BTS
08-01-2013, 04:42 PM
I think someone on here has a great analogy (possibly Janos) about demons catching molecules. I understand that it starts with low density gas and it mostly caught at the bottom of the stack but gas does move past this and get caught higher up, thus the whole stack becomes warm. As you dive deeper the gas density increases and more gas passes the front of the stack and gets caught further back, then the front of the stack is exhausted and this line of exhausted material moves towards the top of the stack. So the whole stack works to remove CO2 but its the bottom thats worn out first and this worn out line moves towards the top of the stack.

That is a better way of putting it than I did....

Jase
08-01-2013, 05:27 PM
What were you taught on your course?

Basically, don't breathe it until your gonna nearly use it (night before at most perhaps) and then pretty similar to yourself, use it within limits. So, perhaps one deeper dive (60M+) and bin it or perhaps a couple of dives as you suggest. I wouldn't use half a fill and then leave it a few weeks and dive the remainder. Pratically speaking, aside from where in the fill is doing what, I am going to breathe through this thing. If its had my breath through it 2 weeks ago and then just sat and festered, despite being proud of my oral hygiene, that can't be a good thing?

Each to their own I guess, but for the cost of a pint and having spent about 8 grand getting this far, I'll play it safe.

BTS
08-01-2013, 05:52 PM
I don't think there would be much festering going on in a scrubber stack....

I have a scrubber that is coming on for three weeks sat in the cupboard, it has done a couple of dives, I have no qualms about putting it back in for a 25M bimble this weekend...

DiverMike
08-01-2013, 07:37 PM
For me once the scrubber is in it stay in until it goes in the bin. If I assemble my unit without lime I leave the temp stick disconnected so on switching on I have a reminder. Normally I'll have fresh lime for a weekend away or for a deep dive. I'm happy with lime in my box for months between dives. I'll open the unit to dry the loop but the canister remains intact. I've got 2 hrs 20 left in from this weekend (only did40 minutes on Sunday) so that will do me for my next weekend in early Feb (or at least he Sat depending on he run times)

What is it that folks thinks happens to part used lime o make it become unsuitable for use?

Janos
08-01-2013, 09:25 PM
I think someone on here has a great analogy (possibly Janos) about demons catching molecules.
It wasn't me. It was Madmole quoting Gordon Henderson.

Sadly he's site is down, but I've copied it here from the wayback machine.



How does the Scrubber work During a Dive?

A lot of people cant seem to get their head around how the scrubber works while diving and how depth, breathing rate etc effects it. Gordon Henderson came up with the best explanation yet for the non techie

------------------------------------------------------------------------------------------------------------------------------

<FX: TwilightZone music...>

Here on Zorg, we abducted some humans to test your resistance to CO2 and the efficiency of our patented CO2 grabbing demon chamber.

We took a human and connected a hose to them. The hose supplies gas and has one-way valves. The exit of the hose goes into a box. Inside this box are 1000s of little demons. These demons adore CO2. They will grab a passing molecule of CO2 and hang onto it for the rest of their lives. They can only hold one each. After the CO2 demon box there is another box with different demons inside - these count the number of O2 molecules you have used and replaces them.

We observed that humans when in a steady state consume the same amount of O2 per breath, regardless of the pressure we subjected them to. When given 100 molecules of our gas, they would use 4 molecules of our oxygen and turn this into 3 molecules of CO2 and 1 molecule of water vapour.

So in the test, with 100 molecules of gas in the loop. The human push/pulled this through the box with the CO2 demons in it. Every breath, 3 lucky demons grab a CO2 molecule each and are happy for the rest of their lives. We repeated this for many of your earth hours, pushing 100 molecules of gas through the CO2 box at a nice steady rate - the happy demon front line progressed linearly through the CO2 demon box until eventually they are all happy. At that point, the loop gas has some CO2 in it and we observed that the humans started to show signs of unease, panic and general ill-feeling. They eventually died a rather uncomfortable death.

To continue our experiments, we abducted more humans and carried on, this time we subjected them to a pressure of 2 bar. This is the same as being under 10 metres of your water. There is now 200 molecules of gas in the loop, but the human still only uses 4 molecules of O2 and turnes these into 3 molecules of CO2 and 1 water vapour. Each breathe pushes 200 molecules through the CO2 demon chamber, so the demons have to work faster to grab the CO2 molecules and die happy. Sometimes a front-line demon misses, but the 2nd line catches it OK. This carries on and eventually all the demons are happy, then as above, the human dies painfully and horribly from CO2 poisoning.

We needed to do more experiments, so we continued with our abduction programme. Now we're testing to 90m. There are now 1000 molecules of gas in the loop, but as observed before, then humans still only take 4 molecules of O2 out and metabolises these into 3 of CO2 and one of water with each breath, However, the poor CO2 demons now have 1000 molecules of gas going through their chamber like a hurricane, and in those 1000 molecules there are still only 3 molecules of CO2! It's now very hard for the demons to catch a CO2 molecule and hang on to it! The front-line demons have a real hard time catching the CO2 molecules and a lot more pass further down the line to be caught by the latter ones. Eventually, the front-line demons are full, but still the latter ones need to work to catch the CO2 and there will come a stage where there aren't enough latter ones who can catch the CO2 fast enough, so some will get through. Eventually so many will get through that the human starts to notice it and dies horribly as before - even when there are still some unhappy and empty CO2 demons left.

Continuing our experiments with more abducted humans, we test again at 90m, but then we decide to ascend the human to some depth where the number of molecules in the loop is much less, so each breath the CO2 demons have more of a chance to catch the CO2 molecules left.

Eventually, after 100's of trials, killing a great many humans every time, (And you should have seen our abduction budget! Off the scale!) we have come up with some rules for keeping humans alive and maximising the happiness of the CO2 demons. Our rules are many, long and complex but to simplify them for you humans we have reduced them to 3 simple rules..

Rule 1: You have 3 hours maximum.

Rule 2: For subsequent dives deeper than 20m: You must leave the bottom when the _total time_ breathed through the system reaches 140 minutes.

Rule 3: For subsequent dives deeper than 50m: You must leave the bottom when the _total time_ breathed from the system reaches 100 minutes.

<FX: We return to our normal program>



I'm glad the Inspiration was machine tested at DERA. Glad I wasn't the human being killed every time. I wonder what other rebreathers would show given the same tests? I wonder why others don't bother with these tests, and instead resport to cycling in the garage with a unit on their backs. It's fairly obvious from reading above that things happen differently at depth. The deeper you go, the wider the reaction front becomes and eventually you'll run out of scrubber before the reaction front reaches the end.

On my first hit, I was on my 2nd 60m dive with the same scrubber. First had been 60m for 30 minutes and about 60 minutes of deco. Second was 60m for 30 minutes... Thats 20 minutes at depth too many. (3rd rule) Combine that with an increase in breathing rate and workload and bingo, I got a hit. You can not do 2 x 30 minute, 60m dives on the same scrubber without violating the rules.

Enjoy,

Gordon

(Many thanks to Gordon for allowing me to use this)



Diver Mole, "Your Inspiration Buddy" (http://wayback.archive.org/web/20080207100709/http://www.btinternet.com/~madmole/divemole.htm)

Janos

paulnlowry
08-01-2013, 09:51 PM
Love the analogy of the little demons.

Baron015
08-01-2013, 10:44 PM
Probably stops any spills or other poop getting on it - but other than that not a lot, I reckon. Why don't you keep it in the unit in the shed with everything else?

Matt.

I wish I had a shed. I feel incomplete. Like only half a man.


Sent from my iPad using Tapatalk HD

NeilB
09-01-2013, 06:24 AM
Jase.....Steve (you know him and the sort of diving he does) says he is quite happy to wrap his scrubber in a bag and use a few weeks later. Take that as instructor talk or experienced user :)

dwhitlow
09-01-2013, 10:25 AM
I wish I had a shed. I feel incomplete. Like only half a man.
Don't worry I have no shed either. I just make do with a purpose built part of the kitchen for storing my unit ;)

Jase
09-01-2013, 11:57 AM
Jase.....Steve (you know him and the sort of diving he does) says he is quite happy to wrap his scrubber in a bag and use a few weeks later. Take that as instructor talk or experienced user :)

Respect that, but for me, in my mind, I'll change it. I want to get in the water for a 10 or 100M dive, both of which I do with the same standard of prep, 100% happy with myself and my kit. Clearly, you can reuse a part used scrubber, that was never really my question in the OP though.

Interesting to hear what others do though. I've probably learnt more watching other divers on a boat than any course has taught me.

Jase

BTS
09-01-2013, 01:24 PM
Clearly, you can reuse a part used scrubber, that was never really my question in the OP though.


Then what was the question because that's what it sounded like...

Markymark75
09-01-2013, 01:38 PM
I've always thought I'd keel over on a 5 min pre-breathe without the scrubber.
Who's tried it?

Any takers - is it for science and everything...

Kermit
09-01-2013, 02:07 PM
Any takers - is it for science and everything... See #61

Jase
09-01-2013, 11:17 PM
Then what was the question because that's what it sounded like...

So, originally asked what others do with a brand new fill, ready to go, that's been prebreathed only. Keep it in the unit, bin it, take it out and store it etc....

Thread kinda drifted off into part used scrubbers and CO2 after that.

BTS
10-01-2013, 06:41 AM
ah, OK, leave it in the unit ready to go for next time...

Nitnab Nhoj
10-01-2013, 08:34 AM
Any takers - is it for science and everything...

Yes. You don't need five minutes.

Major Clanger
10-01-2013, 08:52 AM
ah, OK, leave it in the unit ready to go for next time...

Only thing I'd add is if unit's stored in garage, bring it in if freezing temperatures forecast.

BTS
10-01-2013, 10:33 AM
In the garage!!! You mean you don't sleep with your unit? I have a onesie for mine 'n' evryfink...

Major Clanger
10-01-2013, 10:48 AM
What I do with my unit when it's at home is not for this forum. All I can say is that she's well attended to...but needs a wipe down now and then...

Dean the Diver
01-05-2013, 11:24 PM
Just did my Tec 40 (mod 1) course 2 weeks ago, was advised by my Instructor to bin a partially used scrubber after 3-4 days!!

Did a 80 min dive 22m (new scrubber), but binned it as didn't dive unit again for 6 days. Then (new scrubber) 35m dive for 50 mins followed by a 25m dive for 60 mins. Binned it again (as that was 6 days ago) and am now waiting to dive unit, hopefully next week!

Just following what I was taught!

Regards, Dean

BTS
02-05-2013, 05:34 AM
Just following what I was taught!

Regards, Dean

Sometimes it is worth checking the science behind what you are taught. How does a half used scrubber decay when sat in a cupboard?

davydiver
02-05-2013, 07:37 AM
Its clear from the many 'part used scrubber' threads on various forums that there its very much down to the individual as to how they decide when to ditch a part used scrubber.

Mark Rowe
02-05-2013, 07:50 AM
I've always thought I'd keel over on a 5 min pre-breathe without the scrubber.
Who's tried it?

I did this yesterday on my MK6 as part of the discussion on CCRX and the death of diver who dived MK6 with no scrubber fitted, and my education as didn't know what it felt like.
No scrubber, 5 minutes static sat down pre breathe (on gopro but not viewed it yet - packing too as on way to Dahab now)
3 minutes in - higher breathing rate which continued to climb -panting like a dog at 5 - cant see how anyone would miss it slight headache which increased afterwards. However on this discussion and part used I would double the time or do the pre breathe walking as the exercise will pick up any issue faster.

Mark

ARJAYM
02-05-2013, 06:17 PM
Its clear from the many 'part used scrubber' threads on various forums that there its very much down to the individual as to how they decide when to ditch a part used scrubber.

Yeah ditto.

Also depends on instructor, organisation and surely you should consider manufacturers recommendations too.

I cant help thinking that some are confusing and mixing advice on part used and refilling.

BTS
02-05-2013, 06:23 PM
Yeah ditto.

Also depends on instructor, organisation and surely you should consider manufacturers recommendations too.




It depends on none of these things, it is chemistry and chemistry doesn't change dependant on who teaches it or who makes the plastic bucket you keep it in...

DiverMike
03-05-2013, 07:13 AM
For me there are some immutable rules:
never disturb the scrubber stack
er think thats it

some rules that I'd flex slightly
3 hrs run time
shallower than 50m after 100 min
shallower than 20m after 140 min
I'm personally happy adding ~15 minutes or so to these (including the pre breath) if I'm shallow and a bail to OC would be a no drama event

and some logistics rules
run time shortened to avoid changing lime on the boat
fresh fill for every diver deeper than 45m to give me loads of scrubber time.

If undisturbed the scrubber stack is a chemical filter and I can't see any chemistry as to why it would date expire. That said speaking with the blokes at AP when I collected my unit - there are too many variables for repetitive dives to give concrete advice, but the 3 hour rule is based in cold water and high CO2 production so a worse case scenario.

BTS
03-05-2013, 09:20 AM
, but the 3 hour rule is based in cold water and high CO2 production so a worse case scenario.

4 degrees/40lpm IIRC...

my sac is a third of that or less on an average day. I am not sure of the relevence of the 4 degree external temp as the stack will generate its own heat through reaction. Chemical reactions are generally more effective at warm temps than cold.

So a much lower sac and higher expernal temp should extend the life past three hours, seems no one is willing to commit to figures over the three though...

Capt Morgan
03-05-2013, 09:57 AM
An interesting view on this from Steve Lewis (http://decodoppler.wordpress.com/2013/01/24/how-much-of-a-conservative-are-you/)

dwhitlow
03-05-2013, 10:26 AM
So a much lower sac and higher expernal temp should extend the life past three hours, seems no one is willing to commit to figures over the three though...
I don't think the SAC has anything to do with the life of the scrubber as the SAC is about how much gas is being moved whereas the life of the lime is about the amount of CO2 being exhaled.

A low SAC could indicate a level of CO2 retention is being tolerated whereas a high SAC is likely to result in more effective removal of CO2 from the body. Therefore, whilst a low SAC may be useful on OC it is not useful on CCR.

Nobody will commit to values because they depend on a number of factors and the costs of getting it wrong is potentially high.

The amount of CO2 being expelled depends on the size of the person, their metabolic rate and the amount of work they are doing. More CO2 production results in the consumption of more lime.

If the water is cold the temperature in the scrubber, especially the outside of the scrubber, will fall and with it the rate of the chemical reaction and with that the effectiveness of the scrubber.

The greater the depth the denser the gas and therefore a larger quantity of gas is holding the same amount of CO2. This reduces the probablity of CO2 molecules encounting some lime and therefore reduces the effectivenss of the scrubber.

As others have said, a fresh scrubber always for anything deep whilst for shallow dives I am willing to run the scrubber longer.

nickb
03-05-2013, 10:29 AM
I don't think the SAC has anything to do with the life of the scrubber as the SAC is about how much gas is being moved whereas the life of the lime is about the amount of CO2 being exhaled.It will make a difference to dwell time which is necessary for adequate conversion of the CO2.

dwhitlow
03-05-2013, 10:43 AM
It will make a difference to dwell time which is necessary for adequate conversion of the CO2.
True that is anotehr factor. This all just reinforces the view that if you are ever asking yourself whether to change a scrubber, or not, the answer should always be YES.

Jackdiver
03-05-2013, 10:51 AM
True that is anotehr factor. This all just reinforces the view that if you are ever asking yourself whether to change a scrubber, or not, the answer should always be YES.

The only time I've had a break through, before the dive I was thinking to myself 'Hmm... should I change this scrubber?'

Guess what I didn't do...

:)