PDA

View Full Version : Eurtek 2016 - Temp Scrubber Presentation



cathal
12-10-2016, 09:14 PM
Unfortunately I could not make this presentation. Just wondering is anyone aware of the conclusions if any that were reached, particularly in relation to the RMS system?

Much obliged

Cathal

witchieblackcat
12-10-2016, 10:01 PM
The conclusion was that both the AP and Revo systems were pretty good at monitoring scrubber if you used it in a normal dive situation (i.e. a period of activity and then a period of less activity)

GLOC
13-10-2016, 05:27 AM
A bit more...

- The papers are going through the publication review process, and will be published publicly relatively shortly.
- It was a limited study to provide relative not absolute data.
- The temp-stick systems work well with a 'normal' dive & breathing profile - 1/2 the time at standard workload (6 METS), 1/2 the time at reduced workload (2 METS).
- The temp-stick systems do not work well with failures with up to half of the stack still showing as 'usable' if a full breathing profile of 6 METS was used.
- Combining temp-stick with CO2 sensing alarm provided better coverage in terms of breakthrough.

Understanding the limitations of the sensors is key to understanding what the warning system is telling you. The sensors detect heat due to the chemical reaction and when breathing really hard, the 'CO2 front' can be at a different place to the 'heat front' of the stack.

Energy58
13-10-2016, 07:04 AM
A bit more...

- The papers are going through the publication review process, and will be published publicly relatively shortly.
- It was a limited study to provide relative not absolute data.
- The temp-stick systems work well with a 'normal' dive & breathing profile - 1/2 the time at standard workload (6 METS), 1/2 the time at reduced workload (2 METS).
- The temp-stick systems do not work well with failures with up to half of the stack still showing as 'usable' if a full breathing profile of 6 METS was used.
- Combining temp-stick with CO2 sensing alarm provided better coverage in terms of breakthrough.

Understanding the limitations of the sensors is key to understanding what the warning system is telling you. The sensors detect heat due to the chemical reaction and when breathing really hard, the 'CO2 front' can be at a different place to the 'heat front' of the stack.

I guess that the stick takes a little while to "see" the heat of reaction and in any case the air is also acting as a coolant so the reaction front can zoom ahead of the highest temperatures recorded under high loads resulting in misleading outputs.

cathal
13-10-2016, 07:21 AM
Thanks all for these insights.


Sent from my iPhone using Tapatalk

nigel hewitt
13-10-2016, 09:24 AM
Some of us probably aren't capable of 6 METs of sustained exercise.

GLOC
13-10-2016, 09:48 AM
Some of us probably aren't capable of 6 METs of sustained exercise.
Agreed.

The point being made was that the temp stick sensors have their limitations and you need to understand them. Just because you have half the 'bars' available on the display it doesn't mean you have half the scrubber life left, especially if you then go into a full-on breathing session because you are working hard and breathing like a train.

Regards

MadUKDiver
13-10-2016, 02:04 PM
The point being made was that the temp stick sensors have their limitations and you need to understand them. Just because you have half the 'bars' available on the display it doesn't mean you have half the scrubber life left, especially if you then go into a full-on breathing session because you are working hard and breathing like a train.Regards

Yes, absolutely. This latest comparative study is useful in that it is a wake up call to many of us who thought such sensors were accurate under most scenarios. In the case of the AP sensor the manual does detail some limitations, work rate is mentioned but not in regard to potential impact of high work rate on the accuracy of any warnings. Here are the main extracts...


[From AP Manual 02/14]

The AP Scrubber Monitor performs reliably and consistently in cold as well as warm water, it copes with ascents and descents, and even works with part-used Sofnolime, giving warnings at appropriate times on the HUDs and buzzer.

The Temp-Stik Scrubber Monitor, if fitted, shows the diver the active area of the scrubber according to the dive conditions/work rate during the dive, not before the dive!

This does not measure or sense CO2, it monitors the warm areas of the scrubber giving a graphical indication to the diver of the active area of the scrubber bed. This is then compared to test data, and warnings are then generated in the display and HUDs. In this manner advance warnings can be given which are work, depth and water temperature related.

WARNING! This system does not measure CO2. It simply measures the temperature in the scrubber material at levels through the bed of Sofnolime. It therefore does not warn the diver if there is no Sofnolime present. It does not warn the diver when CO2 bypasses the Sofnolime cartridge due to for example a missing O-ring. It does not warn the diver of CO2 coming via damaged or missing mouthpiece non-return valves. IT DOES NOT DETECT CO2.

The first warning is given when only one segment on the right side of the scrubber monitor is shown as being active. This warning is suppressible (But the dive should be terminated).

NOTE: This system looks not only at the active area of CO2 absorbent, it also looks for abnormal temperature profiles. A warning may be given when CO2 is channelling through the bed. This warning though may prove to be too late for some individuals. This is NOT a CO2 detector or sensor!

It is noteworthy that solutions from two unrelated manufacturers exhibit similar responses in this study. Hopefully the manufacturers will respond once they have had time to review the test methods, results and conclusions.