Extendair

schford

If I get a flood I will bail out - my point is that whether micopore or traditional material is irrelevant for total WOB of the rebreather as the majority of WOB comes from valves, gas direction changes through the loop etc etc

__________________
Bailout and Kit Management account for Murphy's Law

The only bad question is one you did not ask and later wish you had.

Use of RBW is subject to the Rebreather World Terms & Conditions of Use

AD_ward9

I think you are missing the point.

The action of the scrubber generates water.

The amount of water added to the scrubber in the test, was very small: less than what is normally generated by the scrubber.

When we measure granular scrubbers after testing them to exhaustion, they have large increases in breathing resistance, in the same way that scrubbers do that have had water added to them.

On a second thread, the granular scrubber has much higher breathing resistance than the hoses or mushroom valve (assuming both are well designed). This is true for axial scrubbers. We have less data on radial scrubbers and they tend to vary more, but given apples for apples comparisons, the same applies.

Cheers

Alex

scubanimal

Alex,
You mentioned earlier that you eliminate the other components and focus on the WOB through the scrubber. Have you done tests of the various Rebreather loop designs to determine the extent that the basic design (mouthpiece, hoses, lungs etc) contributes to the overall WOB?

AD_ward9

Sorry, but seems to be a misunderstanding. See below.
Of course.

We have figures for every single part, both CAD simulations and actual measurements, and assemblies of those parts (e.g. from inhale bag port to exhale bag port in each direction).

All components in the loop are an issue for WOB. Things like drainage of water from counterlung bags, restrictions on counterlung movement, counterlung position, port position, hose geometry, mushroom geometry, spider shape and cross section, mouthpiece cross section, flow around ports and valves, scrubber inlet, scrubber flow cones, scrubber itself. I have posted pictures of the scrubber flow balancing process in the gallery, but this is done on every component. Often tiny things cause big changes in WOB: I see some of the mods on RBW and take a breath. I look forward to when HSM have their open testing facility in place so anyone can go along and test out their mods objectively: until then it is only the companies with the large investments in test kit that can test this stuff properly. We will share a lot of our data in the Open Revolution disclosures over the next few months, but some stuff is out already. For example, our FMECA Vol 4 shows the consideration of how many fingers on the spider, hose issues etc.

Alex

AD_ward9

With EACs, the difference in performance between a home build and a professionally built scrubber will be huge. They really are sensitive to uneven gas flow. We are aware of a 5:1 difference in scrubber endurance from different scrubber canister designs. There is more about this on a the Meg Extendair thread.

Alex

koputai

Thanks Alex.
I guess the two things go together, being sensitive to an even face pressure, and a very low resistance to flow. It's their own version of chanelling really isn't it.

Cheers,
Jason.

AD_ward9

Interesting the comparison with channelling: you are right, the analogy is there.

The essence is the EAC is almost completely idiot proof in use, but requires very careful canister design.

In contrast, any idiot can design a useable granular canister, but the user has to be very careful in using it so not to have tunneling, shifts with diver pitch, WOB increases with clumping etc.

In the modern environment of Health and Safety regulations, PPE etc, Granular suits a home builder. EACs suits professional companies.

Surprising there is not more innovation coming out of the Granular companies. Guess the dive market is just too small.

Alex

mattmexico

yo

I do have an adapther for my Meg - actually I do have a movie Meg, as they came and where intended to, and where actually used and dived in Romania with Extend's. I still do have the adapter, but that will fit only the movie Meg. As 10 units where made for the movie ( I believe ), and the units went to people who worked and dived on the movie set I would assume ( assumption is the mother of all **** up's ) that all of them 10 units had adapters with them.

saludos
Matt

__________________
N 20' 37.617'
W 87' 04.693'
www.andreaswmatthes.com

caveseeker7

As I didn't want to hijack the original thread I copied and pasted the quotes here:

and
I added the bold type in the last sentence there as it struck me as important.
What happened to the promised "much reduced chance of a caustic cocktail"?
This was by all reports a major caustic incident, in a pool no less!
One of the major advantages that I saw in the cartridges was the added safety in regards to caustic cocktails. That just went out the window. Along with all the hype about changing cartridges underwater. Don't get me wrong here, I'm not trying to bash the Titan (or Optima for that matter), but getting the same effects during a flood as granular absorbant comes as quite a suprise to me.

Actually I wonder if the increase in breathing resistance on granular scrubbers wouldn't act as a warning to come off the loop?

Tom, major thumbs-up for keeping a cool head and the incident from becoming a fatality.
To both Peri and you thanks for reporting the incident, it should prevent cartridge users from developing a wrong sense of safety regarding their scrubbers.

__________________
Cheers
Stefan



"Political Correctness is a doctrine, fostered by a delusional, illogical minority,
and rabidly promoted by an unscrupulous mainstream media,
which holds forth the proposition that it is entirely possible to pick up a turd by the clean end.!"

AD_ward9

The thing must have been sitting in water for at least 30 minutes to get anywhere close to the pH of granules in 30 seconds. The WOB increase must have been enormous!

Goes to reinforce what we have been saying, you need something to detect a flood and shut down the loop automatically.

Alex