Using SofNoLime797 indicating sorb (white to violet)

Sven Becker

Sven Becker

Member
This is a question about using indicating sorb as a tool to set the max time.
I really would appreciate answers from Paul Raymaakers and other professionals that have spent
a lot of time testing sorb.

I have dived Kiss Classic since 2004 nearly 1000 hours.
I have never had any hypercapnia issues.
(Twice I have had an awkward feeling and bailed out on the BOV for a couple of minutes until a burp
has revealed the taste of black grilled hot dogs eaten before the dive)

First 300 hours I used color indicating Spherasorb with max time 180 minutes.
If I exceeded that time there was a clear color warning in the 1 cm bottom part.

Since then I’m using SofNoLime797 indicating sorb (white to violet) with max time 240 minutes.
I hardly never have seen any trace of the violet color unless I exceed 240 minutes.
Note that the last dive always is a recreational dive (<30m, no deco), else I use it 180minutes.

Now the big question:

Given the filter is inspected directly after the dive,
is the first sign of violet color at the very bottom a good indicator of the filter max time?
 
I suspect that someone with more knowledge will be along shortly.
But from discussion with people far smarter than me:-
1) 797 will give you more duration than Spherasorb, but it's not a straight X% more and can be different for rebreather X and rebreather y.
2) Color change indication should not be used to indicate sorb health on a diving rebreather, the color change is only designed to be valid at 1ata whilst the sorb is in use (IE. in an anesthetic machine).
HTH
Simon A
 
I think most have discounted the indicating sorb as an accurate way of estimating sorb life. That said, on the CK, the bottom inch is the first to go, so if it is a good indicator, it would be showing you have heaps left. I think you already picked up on the indicator going away after a while with your quick inspection, but most people have little or no faith in it, as there isn't really any proven evidence of it's effectiveness as an indicator.

I wonder if anyone with a temp stick or RMS has any experience of correlating the sorb life from the heat sensors against indicators?

Dave
 
I used intersorb colour change a few months back in an inspo vision with temp stick. While my temp stick was showing me a +3/4 used scrubber @7 hours usage and time to change it out.. the colour of the sorb was only half shot. Based purely on the colour, I could have doubled my time..

Not a fan. I suspect it is as mentioned, Good in an operating room, monitored live as it gets used.
 
I wouldn't use the colour change to mean anything, it's not recommended (by APD at least). I would use it within the usual parameters, but don't prefer it, as the colour can cause a stain.

Matt.
 
Spiro said:
Based purely on the colour, I could have doubled my time.
Click to expand...

I understand the sentence I quote is intended as a rethorical statement, but I was under the impression that this is not the way scrubber remaining duration should be/is estimated. In other words, even if the color indicator provided a reliable measurement of the reaction front location, x% left wouldn't mean x% of the total duration is left. The prediction should account for a "safety buffer" below which no minimal guaranty of breakthrough-free/CO2 safe operation can be provided. That safety buffer might well be half of the scrubber for one manufacturer/scrubber, and 33% for another.
But honestly, without the manufacturers publishing their algorithms, it is impossible to know... The curves they publish are for constant, stable conditions and never (I think) correlated with reaction front position (they may have the data internally though).
In any case, if you'd wait until your whole scrubber was color-exhausted, you'd probably would have suffocated by hypercapnia by then!
 
matt said:
This is not directly relevant [different grade, pre-packed, not diving], but interesting to someone wishing to read-around the topic:

http://www.molecularproducts.com/pd...rtridges for Low Flow Anaesthesia Medical.pdf

Matt.
Click to expand...
Thanks for the link.
Quite relevant if not "directly", in particular the quote at the bottom of page 2:
" The picture opposite shows an absorber run to 0.5% CO2 at the outlet, which is considered the end-point. Since the violet band has NOT reached the bottom, a common The picture that sentence is referring to shows coloring of between 1/3 to 1/2 of the sorb...

However, I note that on page 3, they go on to explain that, for the purpose of addressing some customer inquiries, they did different kinds of tests than the ones typically used for estimating the capacity of canisters. Specifically, they simulated serial breathing (use, stop for 12 hrs, use again) instead of continuous breathing until CO2 rise. Their conclusion is, in my opinion, pretty badly worded (although I understand that they mean that they stand by their original recommended duration):
"[it] indicated longevities which exceeding those initial guaranteed by Molecular products upon the introduction of the units several years before".
From this to conclude that it is safe to use their product longer than initially recommended, there is a step that many might be tempted to make!
 
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