Inspiration or Evolution?

nitrojunkie

The ability to travel with an evo is much better than the inspiration, but Dave T's points are right on about the benefit of using 2l or 3l bottles in an Inspiration. The evo is definately a little short for sitting around on a dive boat all kitted up but in the water it dives much nicer. I found the drag of the inspiration bothersome in high currents with the evo I find it much better. It's also better for squeezing through tight spots on a wreck.

Get the temp stick to make sure you have a method of watching the scrubber bed and 99% of the time you will be fine doing 2 deep deco dives a day on one fill of sorb. If you are really pushing the limits of depth/time beyond the norm I doubt you'll be doing 2 dives a day and you would likely be dumping the sorb after a single dive on either unit.

Without going over 50% of the scrubber monitor I'm getting 4-5 hours out of the evo scrubber in warm water/minimal currents. In cold water with heavier currents I scale it back to about 3 plus hours. These times seem to work out fine for almost all of the diving I do, which has been mostly in the 160-240' range since getting my evo last March. On 300' plus dives I personally change the scrubber after one dive unless I am planning a much shallower second dive.

I have had ONE series of dives where I came close to maxing out the scrubber. I was pushing the limits by doing a 3rd dive on a single sorb fill. It was a relatively shallow dive in warm water swimming with ripping currents. As I passed the 4 hour 40 minute mark, the scrubber alarm triggered it's first user cancelable alarm of I believe 4 (each of 5 minutes) before it finally gives the bail-out warning. I only had about 20 minutes of deco in which the scrubber regained some efficiency and stopped triggering the alarms. In a total of about 5 hours of serious current diving over 3 dives I found the limit I wouldn't plan on surpassing again. Previously I had done 5+ hours dive series in low current without going much beyond 50% of the scrubber monitor.

Obviously depths/temps/currents all have an impact on duration but unless you plan on doing over 5 hours in warm water or more than 3 hours in cold water the Evo scrubber is not much to worry about. In practical terms it really has more to do with convenience, can you get a full days diving in and change out the sorb at the end of the dive day.

On the gas front 13 CuFt cylinders are fine for deep diving, I generally find shallow water is where i might want to top off cylinders between dives because of the higher o2 mixes.

The harness sucks equally on both units.

Doug

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CCR900

Doug

May I ask two questions relating to your use of the tempstick.

- How many pixels are used on the Vision display? In other words how quickly will the display go from 1/4 left to zero.

- The tempstick sits in the middle of the scrubber (theoretically the warmest part of the scrubber) what is the risk of the cooler sides letting CO2 pass before the tempstick has time to say "no reaction". The temp stick is a heat sensor and not a CO2 sensor right?

Rgds

Fil

decoweenie

I only have my Evolution for a short period of time so haven't pushed it too much yet to learn the limit. However, the last 2 scrubber changes had ~5 hours (+/- few minutes) on each at 22-26C.

The first series was consisted of 2 trimix (max 72m) and 2 shallow (max 20m) dives. The HUD went red to signal the first "last bar" alarm on the scrubber monitor at approximately 4:45. I called the dive and we took ~15 mins to surface, but the alarm never came back as soon as we started the ascent.

The second series was 4 shallow (max 30m) dives and the monitor never exceeded 50% even at 5:00.

All dives were in no/low current environment.

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jradomski

sounds a bit fishy to me..

CO2 production can be pretty much figured out by oxygen consumption.. on the low side (burning mostly protein) figure about .7lof co2 per liter of oxygen, while on the high side1.1l of o2 per liter of oxygen (strictly sugars), for most diets the average should be about .9l of co2 per liter of oxygen.. Figure out carefully howmuch oxygen you are using during a dive and compare it to the temp stick, this should give you a reasonable estimate on how closely the monitor is working.. you can then convert this to a weight and compare it to what the scrubber is supposed to absorb..

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Joe Radomski
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decoweenie

Yes, IF you could be sure that all O2 "used" were metabolized by the diver and not wasted by doing no-flat'ish profiles.

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jradomski

You are always saying your profiles are square, so I guess you can be the perfect guinnea pig..

You oxygen use should not have much wasted gas.

And with a bit of record keeping (like pressure when you reached and left depth), it could be made even more accurate..

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Joe Radomski
CCR Trimix Instructor Trainer
ANDI Instructor Trainer Director #10

All posts are personal opinions and DO NOT reflect any affiliated agency unless specifically stated.

01RMB

I am not the most qualified to talk on how the scrubber monitor works and it has been discussed before and including in posts by Martin Parker so I won't be able to give any evidence or scientific explanation but from my experience I have found that the monitor works well.

From my understanding the temperature stik does not measure CO2 it measures where the reaction is occurring. As CO2 is being absorbed the temperature in the scrubber increases, as the reaction moves through the stack the part behind this reaction front cools. The scubber monitor is measuring the temperature differential.

The reaction front is a cone through the centre of the scrubber stack with the centre of the stack the advanced point of the front. CO2 will break through in the centre of the stack.

At depth the front moves quite fast through the stack. So whilst the absorbtion of more CO2 may still be possible at depth the point of the cone will reach the end of the scrubber quicker allowing CO2 to break through earlier. As you go shallower the front seems to flatten and slows to give you more time. It shows on the monitor as even moving back down the stack.

The two warnings from the scrubber monitor are to ascend immediately and to go open circuit immediately. From my discussions with Martin Parker the second warning had to be followed since CO2 breakthrough would happen very quickly thereafter.

The progress of the monitor is able to be followed. It works similar to a pressure gauge - the remaining scrubber life varies with depth and whilst you don't know in minutes how much longer you have got you can judge the progress to let you know when you should be getting out of there. There is enough resolution in the screen and the steps to give you plenty of time.

The scrubber monitor works really well because it takes into account the water temperature, depth, previously used scrubber time and personal CO2 production.

All I can suggest is once you try the scrubber monitor you will be happy with the results and will appreciate its worth to diving a rebreather. The people I know using it are quite happy and appreciate its value.

Cheers
Rod

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Cheers
Rod

decoweenie

Normally my profiles are square, but not on those 2 series of dives, unfortunately, due to the nature of the dives (i.e. training).

Oh, and I forgot... I am very far from being a "perfect" anything...

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CCR900

I have head comment that the 'event horizon cone' is in deed inverse, if so I would choose to be a little more conservative about pushing my scrubber even with a tempstick.

Going back to the original question, less the tanks and no sorb there can't be that much in it between the two versions for travelling, no?

F

decoweenie

It has been a while since school, but I would also think flow is slower near containing surfaces (i.e. weaker flow near walls of cave instead of center).

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