Please Explain Scrubbers!

nigelh

OK I'll try:

1. Why is the pack mounted on springs?
It closes the O-ring seal without having people screw it up tighter than it needs.

2. Don't they go BANG as a diver lands in the water, and cause the O ring to break it's seal?
Errr.... No. The seal may open and then the spring closes it again.

3. The Spacer Collar above the O ring seats in a bevelled channel, so will it not be displaced, and leak, even momentarily? Gas would rush PAST the scrubber, fuelled by the gas wavefront created by the piston-like cannister throw on that spring!
See 2. Actually there is very little pressure difference so there would be no rush of gas. And if there was it goes round the loop and gets scrubbed next time. This is only CO2. It came out of you and it isn't a problem unless it builds up over a period. A ring in a grove like that is a very efficent seal for low pressures. This is not the classic high-pressure O-ring that isn't round any more but is distorted by pressure into closing the seal. The maximum pressure here is driven by you just breathing. Not even blowing.

4. Why are there not additional seals around the belly or middle portion of the scrubber walls, so an O ring there would always make contact with both surfaces, regardless of travel magnitude? These would keep the alignment correct thereby maintaining seal integrity.
No pressure and the last thing we want is an un-ventilated cavity. Suddenly the O-rings would be under stress trying to maintain the gap at 1 bar.

5. Maybe there is no need to concern myself, as the CO2 is not kept on one side of the scrubber, but rather ABSORBED by the chemical reactions taking place in the material. But what about gas that bypasses the scrubber past the top O ring/collar seal?
The nice things about O-rings are that they make a good seal. Explain bypasses to me again.

Perhaps someone would be so kind as to share their experience with respect to the inevitable high impact (upon entries) on the scrubber for lets say a typical "giant stride" for example?
Done it. Rattles my teeth sometimes above 4 meters. Back in the bad old days you needed to check the handsets but the scrubber wasn't a problem.

6. How does the sprung Sofnolime Cannister not slop around?
Rhetoric. How should I know. It's inside a sealed box. I check it bounces when I assemble it. It's several kilograms so solid might be worse than sprung.

7. If water were to collect in the scrubber, then if inverted, would be allowed to wet the wiring, cells etc. So why is there not a watertight seal around the scrubber cannster? This would require ingress via the scrubber material itself, thereby maintaining vital function to continue unhindered.
Watertight? It's gas tight. This is the O-ring we've been discussing.
Water tends to get to the bottom because the loop is one way. The 'lime can actually soak up masses of water before it starts to get through. A total loop flood, which is what you are talking about will trash everything. However the inhale T-piece is probably more likely to be the villain in that case rather than water making it's way through the 'lime. The whole system is remarkably water tolerant which, for something you take to sea, is a good idea.

8. Why is there not a water sensor in teh bottom of the scrubber? It would be powered by it's own battery and simply activate a buzzer when the probes detect water level threshold.
Because it would go off on 60% of dives. Water at the bottom of the can is normal. You learn to roll it back into the counterlung in Inspo 101.

You're picking a fight with one of the bits of the Inspo that, unless it is badly mis-assembled, isn't a contributory factor in incidents. We have all tipped an inch of water out of scrubber on at least one occasion and wondered that it still worked when all it was was just a bit gurgly.

I'm a bit perplexed by the whole argument. We might be annoyed at APD for dragging their heels on first the ADV and now the BOV but the scrubber can is excellent. I was pleased that they didn't tamper with it when they produced the Vision.

__________________
nigelh

Scubascooby

Some good questions in my opinion. More people should ask questions like this before buying stuff.

Personally I don't like the scrubber design, specifically the moving canister and the o-ring that you have to remove to fill the can.

Removing a small, vital, single-point of failure while doing a scrubber fill seems wrong to me.

__________________
"dove" is NOT the past tense of "dive"

nigelh

Alternatively making you take it out and examine it routinely isn't all that bad.

__________________
nigelh

aainslie

Good point, Nigel.

I actually think the whole design is very clever. A single spring that keeps the canister tightly packed AND compresses the seal - very ingenious. Someone needs serious kudos for that scrubber design.

__________________
Andrew Ainslie

divemasterrob

Ah... well thank you people for your clarifications, and epsecially makes me rest eary now that I can go confidently in the knowledge that the scrubber IS well-designed and effective.

From your answers I basically I see now that...

1. that the pressure imbalance does not exist as (only) the diver pumps gas around the system only.
2. the sprung cannister and O ring seal ARE effective together, allowing the scrubber movement and the Sofnolime material to settle without either affecting seal integrity.
3. Geez those quarries must have some extreme entry points! Glad to see that one's TEETH are the only things that rattle, and NOT the filter system going "south". Should I pack a parachute or something to soften the landing?
4. Water (mostly small amounts) in the can - Oh OK I get that, and pleased that you have not found it a problem.
5. I understand that you stress that properly fitted and correctly aligned parts in the scrubber is KEY to it's proper function only. As with the rest of the unit - stuff MUST be carefully fitted as per - or risk failure, that's every diver's edict.
5. Also agree about great instruction and I WILL ask him to explain stuff too. But what your responses also prove that I have no need to ask about the scrubber seal/collar integrity. Also, sometimes due to some political or business imperitive answers from those instructing my come with a certain bias... That's why I asked people who just dive - YOU are ultimately the final word in objectivity.
You're right of course guys... and cheers again, I'll probably look back in a year of diving the "Inspo Way" and wonder why I had all these questions (fear of death) and what was I really going on about! However, I feel better my theory was ill-founded - proven by people who actually dive this kit, and still find it FUN!
Oh, and yes I don't mind being berated if I say the wrong thing... like they say in SOUTHPARK "there aint no such thang as a stoopid question... only stoopid PEOPLE!" Your generosity and venom are appreciated, just don't call me late to dive! Hehe