Cold v Warm

[Rickoz]

Hi all

I've been doing some reading on breathers & some say the breather is useable up to 3 hours in cold water.
(But nothing is ever said about warm water)

So my question is :
Does warm water make any diff to the scrubber life :confused1

Thank for your info guys & gals.

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Good to see ya on Ness inkandlo
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[ronccr]

good question.... here's the fact's:


To state a X CCR will get a X duration at X water temp,

scrubber design / loop design play a big role... the better the design, the greater efficiency.. the only way you will know valadate this is with independent testing.

CO2 absorbant? again, independent testing.... Temp has allot to with it. to determine you need the following:
- define co2 absorbant (sodasord & sofolime) most popular
- define scrubber type & efficency of breahthing loop.
- water temp
-Work of breathing rate.
- define lbs of co2 absorbant

http://www.steammachines.com/pdfs/TM01-03.pdf

for example...
PRISM scrubber has a radial flow (very efficent type) & contains 6lbs of co2 absorbant. testing at 4.5c or approx 40deg , using sofolime 8-12 mesh , by the US NAVY. Based on this testing, here is a rule set that works for PRISM> (air as dil)
- 4 hours in 40deg F water or 4.5 C.
- 5 plus hours in tropical water ( you need to define 60, 70, 80 deg F of water temp to exactly define.

Also note that if trimix / heliox is used the duration goes down.

It's allot of information, when 4 brads advertise x hours, you really need to define under what testing was this statement applied too.. The only way you will really know is to ask for the test data in writing...
Steammachine (PRISM) post soem of teh non-classified data on their website.
www.steammachines.com or try link below fopr Navy testing data on PRISM.
http://www.steammachines.com/pdfs/TM01-03.pdf

 

[caveseeker7]

So my question is :
Does warm water make any diff to the scrubber life :confused1

Rick, as Ron pointed out the only way to determine the exact duration is through testing (another parameter, by the way, is ambient pressure - the deeper you go the less duration you will have).

The different rebreather designs will react differently to the temperature changes based on the design of the scrubber containers and gas path.
Both the Inspiration and Prism for example have 'insulated' scrubbers, meaning the absorbant has a gas buffer around it. The Dolphin as an example doesn't. That gas space between the bucket and the basket will insulate a bit better than just the container material. Air will insulate a bit better than helium based mixes.

For an airpath example you can also look at the Inspiration and Prism.
In the Inspiration the exhaled gas has to move not only through the hoses and exhalation bag, but also down the pipe to the bottom of the bucket. The idea is that most condensation (cooling) happens before the gas enters the scrubber, and stays in the bottom pads of the basket. Warmth and moisture are added in the scrubbing process, giving the diver such gas to breath (after passing over the sensors, creating moisture problems on uncoated sensors).

In the Prism the exhaled gas enters the scrubber from the top and down the center tube, loosing less temperature. Then it moves through the radial scrubber, outward to the bucket, up through the head with the sensors. Most of the condensation occurs after the scrubber and before returning to the head, when the gas hits the bucket wall. As with the Inspiration, excess moisture is collected in the pad at the bottom of the scrubber, after running downthe bucket wall (the gas having lost that excess moisture causes significantly less condensation around the sensors). The higher gas temperature and moisture contend when entering the scrubber is one reason of the Prism's scrubber efficiency.

Unfortunately there is no single standard by which rebreathers are tested. They are set for NAVY and CE (differntly of course), or can be chosen by the manufacturer. So the results (or claims) can often not be compared very well, and due to the differences in design of the units can't be accurately inferred either. All very frustrating ...

 

[fins wake]

Unfortunately there is no single standard by which rebreathers are tested. They are set for NAVY and CE (differntly of course), or can be chosen by the manufacturer.

US Navy or CE doesn't worry me too much, they're still independent 3rd party testing. And the parameters aren't that different. Actually, they're reasonably similar. I know there's been much writing on this subject on this board, but it would be good for Steam Machines and for APD alike, and for supporters of both rigs to realize that they both have very strong products. One or another may be preferred, but both have passed independent testing with flying colours. And when the PRISM gets CE-certified, both carry the same exact label too, just that one of them has that additional badge of honour ...

Now, claims by some manufacturers may have some grounding in lab and field testing or just the latter. They may be very conservative and thus feel instinctively trustworthy (but perhaps overly conservative) or they may be more hyperbolic. Claims by users of the unit may give a useful pointer, or it might be totally valueless tosh.

Personally I really like the way PRISM publishes its results, but the Inspiration also has a set of very clearly defined parameters.

 

[caveseeker7]

US Navy or CE doesn't worry me too much, they're still independent 3rd party testing. ... Actually, they're reasonably similar. ... it would be good for Steam Machines and for APD alike, and for supporters of both rigs to realize that they both have very strong products. One or another may be preferred, but both have passed independent testing with flying colours. And when the PRISM gets CE-certified, both carry the same exact label too, just that one of them has that additional badge of honour ...

You're right, of course. While I prefer much of the Prism's design, either one will do just fine as far as testing is concerned. It is largely the other units that haven't been tested to either standard that bother me. I'd like to know how the Meg and KISS did in those tests, ...

Personally I really like the way PRISM publishes its results, but the Inspiration also has a set of very clearly defined parameters.

... preferably with published results rather than "just" a mark.
As I said above, the CE mark will do just fine, but the actual numbers are so much more fun. Kudos for SMI for publishing them.

 

[ronccr]

CE rated question? please I'm asking becasue I really don't know the 100% true fact and for personal knowkedge I'd like to know, and since PRISM will most likely be CE rated , I would like to know the facts:

What is the specifications of a CCR CE Testing? does CE out line test criteria such as:
- WOB(s)
- water temp(s)
- scrubber type / efficency / absorbant used
- man testing verses machine testing
- electrinic's ? what standard do they test to, what torolance / deviations is expected.
- how compairable is a CE test verse a US NAVY test?
Do they have 1 set testing rule set or tested under multiabe conditions.
- is there written doc's outlining a CCR CE test?

I am not looking for any specific rig data, I'm only interested in doc's defining a CCR CE test.

Cheers
Ron

 

[caveseeker7]

Ron,

do you still have the e-mail adress posted on SMI's website?
I send some CE info to that mailbox.

Stefan

 

[ronccr]

yes - thanks....

Ron,

do you still have the e-mail adress posted on SMI's website?
I send some CE info to that mailbox.

Stefan

 

[Rickoz]

Hmm ok so warmer water gives longer scrubber life on average

 

[caveseeker7]

Hmm ok so warmer water gives longer scrubber life on average

Yes, to some extend, Rick.

As to the disparity of scrubber ratings and diver reports, I'm sure that the high metabolic rate during testing is the culprint.
For Prism testing, the Navy went with a CO2 production rate of 1.5 lpm.
CE requires 1.6 lpm CO2 injection during testing. Those are the two numbers published. If memory serves me right, the UT240 was supposed to last 240 minutes at 1.8 lpm ... though I don't know who actually did the testing.
Anyway, you'll be hard pressed to sustain either 1.5 or 1.6 lpm for 3 or more hours.