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n2diving · 14th February 2007, 15:12

Premix Rod: As pointed out, the premix rod provides very little benefit in our situation because we inject the O2 in the exhalation CL. Thus for us it adds complexitity with little or no perceived benefit. Since increased complexity incurs increased risk, I elected to remove it because its absence makes cartridge loading easier. I'm not recommending it's removal, and I don't know Dive Rite's official position on removal (or even if they have a position). I do know we are not the only ones to have done so.

Primary Monitoring: It's unclear to me how not monitoring the primary handset in our configuration could lead to a situation where we did not know our PO2. The typical configuration does require the diver to compare the primary display to the secondary HUD. However, we are monitoring PO2's via four sensors, three via the HUD of the secondary and one completely independent sensor via the VR3, none of which are dependent on operation of the primary. I suppose the primary could fail in two ways: one such that it fires the solenoid and causes a high PO2 or the other such that it does not fire the solenoid and causes a low PO2. In our case, failure of the primary such that a low PO2 is caused is unlikely since we don't rely upon the primary to maintain PO2 and such a failure would go unnoticed. A high PO2 would be noticed by our monitoring the four sensors from two other independent sources as well as the sound of the solenoid firing, which would be abnormal.

The risk would seem to be an unnoticed failure of the 'backup' function of the primary. We do check the operation of the primary correctly maintaining setpoint prior to entry. To me, it seems we have adequate redundancy without incurring additional burden of monitoring the two handset displays directly during the dive. However, I welcome further evaluation of the risks.

Helium Rich Mixtures: The WOB in the O2ptima is already so good that I have seen only minor improvements for super rich mixtures vs 21/35 in recreational depths. The primary reason for the experimentation was examine how much the flying after diving time could be shortened by replacing nitrogen with helium.

14th February 2007, 15:12	#9 (permalink)
n2diving www.RebreatherExpress.com Current Rebreather/s: Optima Other Rebreather/s: Inspiration Classic Join Date: Feb 2005 Location: Florida, USA Posts: 279	Re: My O2ptima Configuration Premix Rod: As pointed out, the premix rod provides very little benefit in our situation because we inject the O2 in the exhalation CL. Thus for us it adds complexitity with little or no perceived benefit. Since increased complexity incurs increased risk, I elected to remove it because its absence makes cartridge loading easier. I'm not recommending it's removal, and I don't know Dive Rite's official position on removal (or even if they have a position). I do know we are not the only ones to have done so. Primary Monitoring: It's unclear to me how not monitoring the primary handset in our configuration could lead to a situation where we did not know our PO2. The typical configuration does require the diver to compare the primary display to the secondary HUD. However, we are monitoring PO2's via four sensors, three via the HUD of the secondary and one completely independent sensor via the VR3, none of which are dependent on operation of the primary. I suppose the primary could fail in two ways: one such that it fires the solenoid and causes a high PO2 or the other such that it does not fire the solenoid and causes a low PO2. In our case, failure of the primary such that a low PO2 is caused is unlikely since we don't rely upon the primary to maintain PO2 and such a failure would go unnoticed. A high PO2 would be noticed by our monitoring the four sensors from two other independent sources as well as the sound of the solenoid firing, which would be abnormal. The risk would seem to be an unnoticed failure of the 'backup' function of the primary. We do check the operation of the primary correctly maintaining setpoint prior to entry. To me, it seems we have adequate redundancy without incurring additional burden of monitoring the two handset displays directly during the dive. However, I welcome further evaluation of the risks. Helium Rich Mixtures: The WOB in the O2ptima is already so good that I have seen only minor improvements for super rich mixtures vs 21/35 in recreational depths. The primary reason for the experimentation was examine how much the flying after diving time could be shortened by replacing nitrogen with helium. Last edited by n2diving : 14th February 2007 at 15:48.
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