ISC posts test data

AD_ward9

Looks like there is something different on the test conditions to EN14143 (although depth is deeper). Would it be possible to post the whole NEDU report?

Alex

Drmike

Stoooppp Im turning pedantic! The tests were done on MK15 and Modified MK15 (code named mk15.5) if you read the whole report (1st line of intro says it all) you will see thats clear. If they were all uisng mk16 scrubbers then the last two quoted wob results would be the same! ...so clearly yes the use of mk16 scrubber had a positive effect but even without it in its basic standard from but set up with later rexnord dsv and mk16 hoses the mk15s performance looks far from abysmall at 2.29J/L

I dont have a mk15, I have a mk15.5

no cant send it as im in middle of rebuilding it, although i may bring it with me to the UK later this year for some diving (Oct time)

__________________
Cave diving is a sport
Wreck diving is a sport
Diving in general is a sport

'Rebreather diving' is not a sport
its the delusional obsession with a highly dangerous and often inappropriate piece of equipment

silent running

I'll try and post the whole PDF page, but I am a computer challenged...

silent running

Hi Alex, here is the link to the full PDF from 2001, hope it works:

http://www.steammachines.com/aa1-Testing.asp

Drmike

testing was done with unit in prone position rather than standing (like the ccrb and mk15 tests)

how do you see that (if at all) effecting results?

__________________
Cave diving is a sport
Wreck diving is a sport
Diving in general is a sport

'Rebreather diving' is not a sport
its the delusional obsession with a highly dangerous and often inappropriate piece of equipment

AD_ward9

Which is exactly my point. It is the difference between 2.29J/L and 1.97J/L. The straight Mk15 at 5.3J/L should be right over at the left as the worst performing rebreather of all. Sorry to be having a fit of the pedantics here, but it does affect your chart, which apart from this, is very nice indeed. If we all just juxter position the result columns the graph would become a joke.

Alex

AD_ward9

Found the figures: the table that is labelled Resistive Load is really WOB. The vertical figure is needed as well, as a Navy diver is more prone than the average sports dive.

I have had time to look through the PRISM report. The reason the published WOB for the Prism, and the Mk16 is low, is because it is the "additional" work of breathing: i.e. it does not include the human. As the thing doing the actual work is meant to be a human, then EN14143 includes him. This means that one has to add about 0.6J/L to the Mk15.5, Mk16 and Prism figures to compare with the CCRB table: i.e. the Mk15.5 with Mk16 mods becomes about 2.6J/L (just within the spec), the PRISM becomes 2.3J/L (even more within the spec). Though, to be fair, there is also a subtraction to do, because these figures are 5ft deeper than the depth used for EN14143: so, take away say 0.2, giving apples for applies figures of 2.4J/L for the Mk15.5 with Mk16 mods, and the PRISM turns in a very respectable 2.1J/L beating all pre-2004 sports rebreathers to the post. The straight Mk15 with no mods, picks up the booby prize at 5.7J/L.

On Mike's question, yes, orientation does make a difference. Upright is usually worse than prone, because the over-pressure trick to balance the Lissajou that I mentioned, has less range to work over, and there is more movement of the counterlung centroid as the counterlungs fill and empty (what NEDU call "elastance" and Qinetiq call "compliance").

Alex

Drmike

thanks alex - appreciate you taking the time to share

__________________
Cave diving is a sport
Wreck diving is a sport
Diving in general is a sport

'Rebreather diving' is not a sport
its the delusional obsession with a highly dangerous and often inappropriate piece of equipment

silent running

Alex, thanks for taking the time to look over the report and giving further explanation but can you clear up 2 things:

I can see again why you earlier brought up the issue of calibration of the breathing machine itself, but I couldn't find a part in the NEDU test that mentioned the WOB tests as being for "additional" work of breathing. Aren't all breathing machines used to measure WOB set up to duplicate the additional human WOB part of the loop, like the machine you used for your tests?

And isn't the 14143 done at 40m which is 5+m shallower than the NEDU test depth of 45.72m, not 5 ft shallower? -Andy

AD_ward9

Sorry my brain was in the wrong unit when I was typing. Yes, it is 5m shallower hence I suggested the WOB would be 0.2 lower than stated. 5ft would have made hardly any difference at all.

On the breathing machine issue, it is a matter of whether the equipment is being tested, or the effect of the equipment on the person. With the former, it is completely appropriate to remove the effect of the test equipment, but the latter means it must be included. EN14143 is a safety standard primarily, whereas the US Navy NEDU document is primarily for equipment procurement purposes. It is actually very hard to make the machine match a person from a dead volume and WOB perspective as well as all the other stuff (humidity, temperature etc), which is why earlier work tried to avoid. This issue of "additional work" is in the 1994 NEDU document which describes the methods they apply to assess UBAs. I will dig it out and post a reference to it (late here, so tomorrow).

Alex