[iain-hsm]

A picture tells a 1000 words.

The temperature rise shows a rock steady slow climb after a 5 minutes delay and gives a sure fire safe and reliable measure of temperature!

Just a shame that at the same time your C02 jumps all over the place!!

C02 spikes at 1.2Kpa but the temp stick shows no problem...go figure!

Full report will be published next four weeks. Iain Middlebrook HSM

[Padowan]

Very interesting to actually see come comparitive scientific data. Certainly looks like the technology is a very good indicator (although the fact that AP are using this should indicate it's usefulness!).

One quick question. There is one temperature trace there, was that a single thermistor near the outlet of the scrubber?

[Mark Chase]

I wasn't aware the raise in temp was an issue. I understood that all the temp stick did was tell you how far up the scrubber the active front was. This equates to remaining dwell time which equates to how long the scrubber will last before it breaks through?

Are you suggesting that momentary spikes in Co2 production should equate to spikes in temperature. Does the exothermic reaction react that quickly? Doesn’t the temp stick indication of the working front indicate the point at which such spikes can not be handled by the remaining dwell time?

I would have thought the warning system would be designed to allow for a range of spikes and troughs in the CO2 production. Thats what I would have done if I designed it.

ATB

Mark Chase

[caveseeker7]

Quote: (Originally Posted by iain-hsm)

C02 spikes at 1.2Kpa but the temp stick shows no problem...go figure!

Oooops!

[Andy M]

Quote: (Originally Posted by iain-hsm)

The temperature rise shows a rock steady slow climb after a 5 minutes delay and gives a sure fire safe and reliable measure of temperature!

Very interesting. Please can you detail the test rig, was it an Evo scrubber and where were the temperature samples taken exactly. How was CO2 produced and introduced into the scrubber?

Thanks

[wedivebc]

This just shows it should not be refered to a CO2 detector but a scrubber life indicator which is what it was designed to do.

[edster]

Are you suggesting that momentary spikes in Co2 production should equate to spikes in temperature.


Surely even if there were, the thermal capacity of the scrubber material would absorb the heat of reaction for quite a while, especially if the reaction front is near the bottom of the scrubber and the hotter gas has all that material to go over - if you see a temp spike it probably means a) your near the end of the scrubber life and b) you've got a spike... oh bugger

[iain-hsm]

Quote: (Originally Posted by Andy M)

Very interesting. Please can you detail the test rig, was it an Evo scrubber and where were the temperature samples taken exactly. How was CO2 produced and introduced into the scrubber?

Thanks

Ok sorry about that. For clarity this was an actual dive, the C02 was produced by the diver during an open water dive and logged by a C02 detector in the breathing loop (inhale side hose) The C02 data in turn was used by the wrist controller to automatically flush the bag.

The data is still raw so I really didn’t want to make any conclusions however:



What the print out shows is the first 70 minute period of a dive showing C02 against temperature. The points of interest are:

1. The log recorded a massive rise in C02 of 1 kPa in the bag during the first heavy work period 20 minutes into the dive

2. Four further heavy spikes were recorded at 40, 50, 55 and 60 minutes with a peak of 1.2 Kpa into the dive again during a heavy work period.

3. The main point to be made is that the bag spiked with the work load ( a known fact)

4. In the event that no C02 detector (and no solenoid diluent flush controller) had been fitted then no flushing would have been performed during this dive and we would have been looking at a possible different outcome.

5. Now consider the temperature graph this shows a non event, nothing.

[dive2dive2000]

What kind of ccr and what find of scrubber?
Martin

Quote: (Originally Posted by iain-hsm)

Ok sorry about that. For clarity this was an actual dive, the C02 was produced by the diver during an open water dive and logged by a C02 detector in the breathing loop (inhale side hose) The C02 data in turn was used by the wrist controller to automatically flush the bag.

The data is still raw so I really didn’t want to make any conclusions however:



What the print out shows is the first 70 minute period of a dive showing C02 against temperature. The points of interest are:

1. The log recorded a massive rise in C02 of 1 kPa in the bag during the first heavy work period 20 minutes into the dive

2. Four further heavy spikes were recorded at 40, 50, 55 and 60 minutes with a peak of 1.2 Kpa into the dive again during a heavy work period.

3. The main point to be made is that the bag spiked with the work load ( a known fact)

4. In the event that no C02 detector (and no solenoid diluent flush controller) had been fitted then no flushing would have been performed during this dive and we would have been looking at a possible different outcome.

5. Now consider the temperature graph this shows a non event, nothing.

[iain-hsm]

Quote: (Originally Posted by edster)

Are you suggesting that momentary spikes in Co2 production should equate to spikes in temperature.


Surely even if there were, the thermal capacity of the scrubber material would absorb the heat of reaction for quite a while, especially if the reaction front is near the bottom of the scrubber and the hotter gas has all that material to go over - if you see a temp spike it probably means a) your near the end of the scrubber life and b) you've got a spike... oh bugger

No not at all, in fact what the dive log shows is that temperature has nothing much at all to do with C02 production that is relevant to diving. Although present has no (added little)relevance to C02 production in varying work loads.



This is just one log number 43 we have during these trials. Note this was in the first 20 minutes of the dive not at the end. The absorbent was new fresh and properly tamped. This has nothing to do with a ”reaction front” the diver continued to perform a normal profile and decompression obligation. The soda lime was still working fine at the end of the dive.



Point is during heavy work you produce C02. This can spike the breathing loop in a massive C02 loading. In the event that C02 is not monitored and a controller does not automatically flush the bag, then the high C02 spike you see in the print out would have continued across the page.