ISC posts test data

paulraymaekers · 11th April 2008, 17:29

Quote: (Originally Posted by AD_ward9)

In EN14143:2003 it states clearly in Section 6.3.2 that WOB and respiratory pressure has to be measured against the displaced volume, i.e. the piston in the breathing machine. That is one point is in the mouthpiece and the other the end of the piston volume inside the breathing machine. This correlates completely with the EN14143 calibration Lissajou, which gives 25mbar positive pressure under those circumstances, when the dimensions of the breathing machine match a human (dead volume, internal resistance etc).

Alex, that sounds weard to me..

I have been interpreting that WOB and respiratory pressure has to be 'plotted' against displaced volume, and not measured: exactly the graph from wich we can mesure the WOB
as far as I have seen a breathing machine like the ANSTI does in no means mach a human body in dead volume.. already the connection hoses from the piston to the mouthpiece, length minimum 3/4 meter, diameter 50/60mm
I have always interpreted the calibration orifice beiing used just to check volume displacement against pressurediff..

am I completely wrong, or do we express ourself wrongly??

paul

AD_ward9 · 11th April 2008, 17:38

Quote: (Originally Posted by paulraymaekers)

Alex, that sounds weard to me..

I have been interpreting that WOB and respiratory pressure has to be 'plotted' against displaced volume, and not measured: exactly the graph from wich we can mesure the WOB
as far as I have seen a breathing machine like the ANSTI does in no means mach a human body in dead volume.. already the connection hoses from the piston to the mouthpiece, length minimum 3/4 meter, diameter 50/60mm
I have always interpreted the calibration orifice beiing used just to check volume displacement against pressurediff..

am I completely wrong, or do we express ourself wrongly??

paul

The displaced volume is the piston movement. You can measure it. It means the Lissajou is the displaced volume against pressure.

The pressure is relative pressure. The issue is relative to what? This is where the calibration Lissajou comes in. If you put the calibration orifice on a true sine flow machine, relative to the outside of the mouthpiece, you do not get a WOB of 3.3J/L at 50msw. It you put the reference in the volume being moved with the tubes similar to a human, then you get the reference Lissajou exactly.

We are aware the ANSTI machines do not match a human. That is why we spent a lot more than an ANSTI machine on one that does match a human, including the bronchial resistance.

This may, or quite likely may not, be what the EU Committee intended to achieve, and the woolly wording of where the reference is other than its hydrostatic position, does not help one bit. They may have also come up with the calibration orifice by mistake: transparency in the process would be most welcome. It a tester were to take the reference point directly outside the mouthpiece, one can chop almost 0.8J/L from the graph I posted: that is how large these differences in measurement method can be. DL reads EN14143 as a safety document for human safety, and given the indicator on the calibration Lissajou they use, then it appears to be correct to do the proper safety test and measure relative to the moving volume with the right breathing machine. NORSOK is more explicit with this, in that the breathing simulator should simulate a human.

For example, take the DL Sports rebreather we have had sitting about for quite a while, as the safety case progresses slowly forward. It has a true WOB of 2.19 J/L, and 2.68 J/L on a human (40msw, 75lpm RMV, 3 litre stroke, air). We can remove the "+b" part of the equation just by measuring the WOB relative to a suitable point in the water (at the suprasternal notch position), and chop 0.8J/L off this figure, to claim 1.4 J/L to 1.88 J/L, but frankly, that is not the true result when used on a human diver.

Alex

paulraymaekers · 11th April 2008, 17:59

Quote: (Originally Posted by AD_ward9)

We are aware the ANSTI machines do not match a human. That is why we spent a lot more than an ANSTI machine on one that does match a human, including the bronchial resistance.

This may, or quite likely may not, be what the EU Committee intended to achieve, and the woolly wording of where the reference is other than its hydrostatic position, does not help one bit. They may have also come up with the calibration orifice by mistake: transparency in the process would be most welcome. It a tester were to take the reference point directly outside the mouthpiece, one can chop almost 0.8J/L from the graph I posted: that is how large these differences in measurement method can be. DL reads EN14143 as a safety document for human safety, and given the indicator on the calibration Lissajou they use, then it appears to be correct to do the proper safety test and measure relative to the moving volume with the right breathing machine. NORSOK is more explicit with this, in that the breathing simulator should simulate a human.

so this means that al the CE WOB tests done on the actual CE rated units, and other publisched results, have not been done according to the 'intention' of the CE14143, but in a practical way, and taking a ref pressure somewhere static in the pressure vessel?

paul

Dive!Dive! · 11th April 2008, 18:00

All,
This is interesting stuff, but I have another related question.
As far as I understand the tests under discussion, all of them relate to the use of air ?
I (like a lot of people I guess) use some He below 40m. So, lets say hypothetically I have a 'good' result of '2' on Air and another result of '3' . also on air at say 50m, what would the rough impact of using say 18/45 be?
Cheers
Steve

AD_ward9 · 11th April 2008, 18:08

Quote: (Originally Posted by paulraymaekers)

so this means that al the CE WOB tests done on the actual CE rated units, and other publisched results, have not been done according to the 'intention' of the CE14143, but in a practical way, and taking a ref pressure somewhere static in the pressure vessel?

I am saying there is lots of scope for interpretation in these standards, that can be used well, or used "to get a pass". It is therefore essential to publish the cal data and details of exactly how the test was carried out. By offering to measure these things under identical conditions, I hope the playing field will stay level, and perhaps future versions of the standards will be a bit clearer.

Alex

11th April 2008, 17:29	#181 (permalink)
paulraymaekers rEvo's daddy Current Rebreather/s: rEvo Other CCR Home Build Other Rebreather/s: rEvo Other CCR Home Build Join Date: May 2005 Location: belgium Posts: 1,377	Re: Free Whisky Offer Quote: (Originally Posted by AD_ward9) In EN14143:2003 it states clearly in Section 6.3.2 that WOB and respiratory pressure has to be measured against the displaced volume, i.e. the piston in the breathing machine. That is one point is in the mouthpiece and the other the end of the piston volume inside the breathing machine. This correlates completely with the EN14143 calibration Lissajou, which gives 25mbar positive pressure under those circumstances, when the dimensions of the breathing machine match a human (dead volume, internal resistance etc). Alex, that sounds weard to me.. I have been interpreting that WOB and respiratory pressure has to be 'plotted' against displaced volume, and not measured: exactly the graph from wich we can mesure the WOB as far as I have seen a breathing machine like the ANSTI does in no means mach a human body in dead volume.. already the connection hoses from the piston to the mouthpiece, length minimum 3/4 meter, diameter 50/60mm I have always interpreted the calibration orifice beiing used just to check volume displacement against pressurediff.. am I completely wrong, or do we express ourself wrongly?? paul __________________ www.rEvo-rebreathers.com .... the earth is flat, Elvis is alive, and radial scrubbers give longer dwell time than axials...
(Online)

11th April 2008, 17:38	#182 (permalink)
AD_ward9 So much more to learn Current Rebreather/s: Other CCR Other Rebreather/s: Other CCR Join Date: Jun 2005 Location: Scotland Posts: 1,589	Re: Free Whisky Offer Quote: (Originally Posted by paulraymaekers) Alex, that sounds weard to me.. I have been interpreting that WOB and respiratory pressure has to be 'plotted' against displaced volume, and not measured: exactly the graph from wich we can mesure the WOB as far as I have seen a breathing machine like the ANSTI does in no means mach a human body in dead volume.. already the connection hoses from the piston to the mouthpiece, length minimum 3/4 meter, diameter 50/60mm I have always interpreted the calibration orifice beiing used just to check volume displacement against pressurediff.. am I completely wrong, or do we express ourself wrongly?? paul The displaced volume is the piston movement. You can measure it. It means the Lissajou is the displaced volume against pressure. The pressure is relative pressure. The issue is relative to what? This is where the calibration Lissajou comes in. If you put the calibration orifice on a true sine flow machine, relative to the outside of the mouthpiece, you do not get a WOB of 3.3J/L at 50msw. It you put the reference in the volume being moved with the tubes similar to a human, then you get the reference Lissajou exactly. We are aware the ANSTI machines do not match a human. That is why we spent a lot more than an ANSTI machine on one that does match a human, including the bronchial resistance. This may, or quite likely may not, be what the EU Committee intended to achieve, and the woolly wording of where the reference is other than its hydrostatic position, does not help one bit. They may have also come up with the calibration orifice by mistake: transparency in the process would be most welcome. It a tester were to take the reference point directly outside the mouthpiece, one can chop almost 0.8J/L from the graph I posted: that is how large these differences in measurement method can be. DL reads EN14143 as a safety document for human safety, and given the indicator on the calibration Lissajou they use, then it appears to be correct to do the proper safety test and measure relative to the moving volume with the right breathing machine. NORSOK is more explicit with this, in that the breathing simulator should simulate a human. For example, take the DL Sports rebreather we have had sitting about for quite a while, as the safety case progresses slowly forward. It has a true WOB of 2.19 J/L, and 2.68 J/L on a human (40msw, 75lpm RMV, 3 litre stroke, air). We can remove the "+b" part of the equation just by measuring the WOB relative to a suitable point in the water (at the suprasternal notch position), and chop 0.8J/L off this figure, to claim 1.4 J/L to 1.88 J/L, but frankly, that is not the true result when used on a human diver. Alex Last edited by AD_ward9 : 11th April 2008 at 17:50.
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11th April 2008, 17:59	#183 (permalink)
paulraymaekers rEvo's daddy Current Rebreather/s: rEvo Other CCR Home Build Other Rebreather/s: rEvo Other CCR Home Build Join Date: May 2005 Location: belgium Posts: 1,377	Re: Free Whisky Offer Quote: (Originally Posted by AD_ward9) We are aware the ANSTI machines do not match a human. That is why we spent a lot more than an ANSTI machine on one that does match a human, including the bronchial resistance. This may, or quite likely may not, be what the EU Committee intended to achieve, and the woolly wording of where the reference is other than its hydrostatic position, does not help one bit. They may have also come up with the calibration orifice by mistake: transparency in the process would be most welcome. It a tester were to take the reference point directly outside the mouthpiece, one can chop almost 0.8J/L from the graph I posted: that is how large these differences in measurement method can be. DL reads EN14143 as a safety document for human safety, and given the indicator on the calibration Lissajou they use, then it appears to be correct to do the proper safety test and measure relative to the moving volume with the right breathing machine. NORSOK is more explicit with this, in that the breathing simulator should simulate a human. so this means that al the CE WOB tests done on the actual CE rated units, and other publisched results, have not been done according to the 'intention' of the CE14143, but in a practical way, and taking a ref pressure somewhere static in the pressure vessel? paul __________________ www.rEvo-rebreathers.com .... the earth is flat, Elvis is alive, and radial scrubbers give longer dwell time than axials...
(Online)

11th April 2008, 18:00	#184 (permalink)
Dive!Dive! New Member Current Rebreather/s: Megalodon Other Rebreather/s: Join Date: Sep 2006 Location: Somerset, UK Posts: 93	Re: ISC posts test data All, This is interesting stuff, but I have another related question. As far as I understand the tests under discussion, all of them relate to the use of air ? I (like a lot of people I guess) use some He below 40m. So, lets say hypothetically I have a 'good' result of '2' on Air and another result of '3' . also on air at say 50m, what would the rough impact of using say 18/45 be? Cheers Steve
(Online)

11th April 2008, 18:08	#185 (permalink)
AD_ward9 So much more to learn Current Rebreather/s: Other CCR Other Rebreather/s: Other CCR Join Date: Jun 2005 Location: Scotland Posts: 1,589	Re: Free Whisky Offer Quote: (Originally Posted by paulraymaekers) so this means that al the CE WOB tests done on the actual CE rated units, and other publisched results, have not been done according to the 'intention' of the CE14143, but in a practical way, and taking a ref pressure somewhere static in the pressure vessel? I am saying there is lots of scope for interpretation in these standards, that can be used well, or used "to get a pass". It is therefore essential to publish the cal data and details of exactly how the test was carried out. By offering to measure these things under identical conditions, I hope the playing field will stay level, and perhaps future versions of the standards will be a bit clearer. Alex
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