Quote: (Originally Posted by
caveseeker7)
Just a thought, I usually don't consider a unit stock when either electronics or the loop have been modified.
Seems the loop is the most important thing on a rebreather, modifications can influence many factors,
some rather important IMHO (like WOB, duration).
It is very hard to draw a clear line on what is a stock unit and what is a significantly modified unit. I agree on the WOB risks from mods to the loop, but scrubber duration is mostly down to scrubber geometry and the flow into the scrubber, unless people put in the wrong granules (often happens) - differences in packing are probably more relevant.
The three main factors for WOB are the mouthpiece, scrubber and CLs. Most mouthpiece mods I have seen are pretty well neutral, and few people change the scrubber on an eCCR. However changing CLs is definitely is a Major Modification, generally untested and negative in its effect.
I also agree with you that modifications are generally a bad idea. I believe manufacturers should reverse all mods other than added dive computers or PPO2 monitors, or a plain safety fix that is known by the manufacturer, when a unit comes in for service: to do anything else is inviting trouble. Not a popular view, but from the safety viewpoint this is the only defendable course, when very few people who modify units actually test their mod. I also have the view that units should be shut down if not serviced annually. Again, not a popular viewpoint but if we are going to reduce accident rates we need to learn from other industries where unstable life critical systems are used.
A good example of the side effect of mods is the BMCLs on the Inspo. That particular mod is much better executed than most, and much better thought out, even still it massively increases WOB, unless a lot of holes are made in the backplate that comes with the kit. I.E. mod the mod.
Alex