NITROX problems

[camerone]

My understanding is the Oxycheq sensor should be replaced annually even though I only do about 50 Nitrox tanks per year.

Just replace it when it dies. Its not actually an oxycheq sensor its a Teledyne. They are fine and then drop off a cliff performance wise and you will be turning the dial way up. Its pretty obvious when they fail.

Mine last about 2-2.5 years.

Yeah - they current limit in high PO2 situations. In an analyzer, I've even gotten 3+ years out of an Analytical Industries one (which is what I use in the rebreather...) I've never made it that long with the Teledyne cells, but 2-2.5 seems pretty reasonable.

Lifespan effectively has nothing to do with how many tanks you analyze. It's time from manufacturing and from first exposure. Years ago, those that didn't understand tried to use "cell savers" and other such nonsense like caps across the sensor face and inert gas "shields" when not in use. Most of it was silliness, where a tiny kernel of truth got really distorted.

Personally, I take my rebreather cells out each year and then install them in the O2 analyzers I have and use them for another year. It's both more dangerous and more likely that you will have a cell failure underwater than in an analyzer, because you're running higher partial pressures of O2; therefore you're going to see it first. Standard dive practice is to replace cells every 12 months in a rebreather regardless, and they're reasonably enough priced that I do it rather than push out to the 18 months they could potentially be okay.

Two simple checks for me for life in the analyzer: first, I just run 100% O2 across the face of the cell. If I get a 100% reading or close, it's fine. Second check - the calibration potentiometer eventually runs out of "range". It's deliberately chosen for the application to deal with a well functioning cell. As the cell ages, it gets turned up more and more to adjust the gain of the circuit. Eventually I start to run out of room.

FWIW, I usually end up with three spare cells from the rebreather swap before either of those happen.

[CaptnJack]

I'm sure my ~2-2.5 yr lifespan for analyzer cells is partly a function of being in a garage which is only barely warmer than outside in winter and only barely cooler than outside in summer. It would last longer at a consistent moderate temp.

In the RB I replace mine every January. I need to make a molex to other plug adapter so I can reuse CCR cells in analyzers.