Channeling in vertical vs. horizontal transportation?

[divebutt]

here’s an interesting one for the group…

Been diving an Inspiration all season. Love it. 30+ hours or so on it. Should have gone to a rebreather years ago.

In all those dives, I’ve had 2 instances where I felt what I assume to be excess CO2. Not too bad - some increased respiration and pulse without an increase in exertion. First time, bailed out, felt normal after a half dozen breaths on OC, ascended fine. Second time, shallow and at end of dive. Ascended a bit and went back to normal. In both cases, about 3 hours on scrubber and 3 dives over 3 days, over the course of a week. Dives were on different fills of sorb. All lower energy shore dives, coldest temp around 50F. Temp stick showed majority of scrubber working.

Hoses are fine, mushroom valves are perfect, all o rings in place, sorb less than 12 months old and secured safely. Scrubber is sealed in its can between dive days.

One thing that comes to mind is transportation. The unit is typically horizontal while driving - on its back when dry and going to the site, and on its front going home.

Any thoughts or experience on that vs. Vertical storage during transport and the possibility of channeling?

Something else I’m missing? Instructors feedback was potentially kinked hose unkinking and releasing some CO2 from dead airspace or overpacked scrubber. Been very careful with both.

 

[Mobulai]

on its back when dry and going to the site, and on its front going home.

Why the flip in transport back and forth?

I can imagine vibration at transport that settles sorb parallel to flow axis might contribute to channeling — but nothing definitive
I’d personally rather transport while it’s vertical, and let the spring take care of the last bit of clearance drop
(Or am I mistaken and it’s a radial scrubber— not that familiar with Inspos)

 

[DiveLikeAMuppet]

Given the fact that you have 30 hours on the unit and probably loads of OC experience at the same divesites, my suspicion would be that you are breathing shallow and not exhaling properly. Could also be your position in the water. It's really easy to overbreathe the scrubber.

But I did personally wonder if storing the unit horizontally and driving long distances could settle the scrubber in some strange way that would not be fixed by springs and positioning the unit upright when kitting up.

 

[davehicks]

The rated duration of the Inspo is 3 hours (conservatively), and you report having issues after 3 hours. Transport position should only be a factor if the scrubber is prone to channeling.

That would suggest you might not be packing tightly enough. I'd look more closely at this. Personally, I use a soft bag lead weight 2lb (1kb) to tap on my scrubber to pack it down. This works much better than whacking it with my hand and hurts a lot less.

Perhaps have another Inspo diver watch you pack and assemble the entire unit and give you pointers. As a fairly new CCR diver you might benefit from some additional feedback. Asking for feedback on the forum is great, but some 1:1 feedback might be better.

Of course, you could just be over-breathing the scrubber as you get to the end of its runtime. Make sure you are fully exhaling and consider flushing your loop as you get to the end of your dives. This can help to avoid any CO2 accumulation.

 

[evandroairton]

When i transport to long distance i take the scruber, shake to hear if the sorb is loose (you may listen the shaking grains moving) and, thigh the spring a litle, as i assume that the bumping can make the screw to go loose.
And, as sayed, over breathing could be and issue.

 

[DiveLikeAMuppet]

When i transport to long distance i take the scruber, shake to hear if the sorb is loose (you may listen the shaking grains moving) and, thigh the spring a litle, as i assume that the bumping can make the screw to go loose.
And, as sayed, over breathing could be and issue.

Perhaps we are all overestimating how much the scrubber gets compacted in a car. Thinking of my JJ, a well-packed scrubber will settle very little after several hours to and from a dive site in very rough seas - maybe a quarter turn of the screw maximum if at all. I'm pretty certain I would need to run over speed bumps at high speed and damage my suspension to get the same effect in a car.

 

[mr_v]

Unless you're driving on country roads at high speeds and hitting some major washboard, I don't see transportation to be a major concern. There are a few places where I'll check the scrubber after a drive, but it is mostly because I OCD than anything else. If you do not repack used scrubber and are at least average when it comes to packing the sorb cassette, you should be okay. Kinks in hoses sound possible but not probable.

With 30 hours on the unit and 2 experiences, perhaps you underbreathe your lungs. There is a lot of dead air space in our air pathways and if you don't clear it all, you may end up with a CO2 hit. PPCO2 required for a hit is tiny.

As for transporting the unit, water position in the loop is the major factor. You don't want water to slosh around so you'd typically take the unit apart, dry it, then drive back. Alternatively, you position the unit in a way that prevents water from damaging cells or entering sorb.