Retorical question on rebreathers

[ghof]

I have been reading about rebreathers since the first Electrolung was a gleam in the eyes of the builder. Some, like the Kiss Sport have a depth rating of 150' but are compatable with Trimix. What, in the design is it, that places this seemingly arbitrary limit ? Let's assumb for the sake of argument that the diver(not me!) has all the skill sets to make much deeper dives. Also, just for the fun, of it let's assumb that there will not be a sudden catatrophic failure at 151'.
My experience with rebreathers 0
My chances of ever diving a rebreather 0

GHOF

 

[BigJetDriver]

I have been reading about rebreathers since the first Electrolung was a gleam in the eyes of the builder. Some, like the Kiss Sport have a depth rating of 150' but are compatable with Trimix. What, in the design is it, that places this seemingly arbitrary limit ? Let's assumb for the sake of argument that the diver(not me!) has all the skill sets to make much deeper dives. Also, just for the fun, of it let's assumb that there will not be a sudden catatrophic failure at 151'.
My experience with rebreathers 0
My chances of ever diving a rebreather 0

GHOF

SCR's reach a point where their ability to feed O2 at the required or given rate is compromised by the relationship between the inter-stage pressure and the ambient pressure.

 

[ghof]

Excellent! a nice simple answer. Thanks

 

[caveseeker7]

GHOF,

the SportKiss' depth rating has more to do with liability and scrubber rating than the units ability to deliver O2. BigJet is correct that constant mass flow valves being supplied through an unbalanced first stage will eventually be unable to supply gas. On the Sport and Classic KISSes that system is the same, though, and good to around 100 meters. But the SportKiss is designed and built for sport (read recreational) divers. The very compact scrubber design is for those limits rather than greater depth.

Or, directly from the source as posted here on Scubaboard

... The Classic KISS is rated for 250 feet, with proper training, gases and bailout. People have asked me about diving deeper than this, as they know divers who do. We do not recomend it. I believe that those who are going to deeper depths are doing so on modified units. Yes, Liability is an issue.

The Sport KISS is rated for 150 feet. At this depth the diver must have adequate training, gases and bailout. Why this depth? Liability is a huge issue. Also, this rebreather has been designed for the sport diving market. Gordon and I regularly dive this unit in the 150 foot range and use normoxic trimix, 20/40 on all dives, regardless of depth. ...

Regards,

Kim Smith
www.jetsam.ca

For other CCRs, like the Inspiration, the depth rating is dependent on the CE testing and certification protocol.

Semi-closed units with cmf valves are usually depth limited (ppO2 limited, really) by the gas they are using and certified with. For both the Dräger and OMG SCRs that's 40 meters with 32% nitrox (ppO2 = 1.6 ata).

Stefan

 

[ghof]

My dives in the Great Lakes (DIR style equipment configuration) have been self limited to 175' once, most of the best wrecks are deeper. I cannot handle the weight of my E-8 -130's anymore and I am toying with the idea of rebreathers. The SCR is just about perfect for the diving I like to do. If I sell my twins the cost would not be too bad. On OC I like to keep run times to 90 minutes due to the cold water should anything cause a suit failure. I would also like to hit a couple wrecks that are at about 200' though and this seems to be the outside of the SCR design. However, it might be just a liability issue more than a technical one.
GHOF

 

[caveseeker7]

With both ambient pressure and temperature influencing the scrubber duration I wouldn't want to push the SportKiss where you dive. The SportKiss' scrubber isn't insulated (no gas gap around it). From what I gather the Great Lakes are a bit on the nippy side.

Don't know E-8 130 specs, but I asume an empty weight around 45 lbs for the tank/valve ... that's about what the SportKiss weights, also without BC, but full 2ltr tanks and full scrubber.

You'll still need to add adequate bailout, depending on your SAC & profile.

 

[scubahubby]

Since this thread started with a mention of the Sport Kiss and several responses are mentioning SCR I just want to point out, for those that are new to rebreathers, that the Sport KISS is not an SCR it is a CCR.

 

[divemonster]

...........can't you come up with your own quote? ( that's mine!) .....................................................................

the SportKiss' depth rating has more to do with liability and scrubber rating than the units ability to deliver O2. BigJet is correct that constant mass flow valves being supplied through an unbalanced first stage will eventually be unable to supply gas. On the Sport and Classic KISSes that system is the same, though, and good to around 100 meters. But the SportKiss is designed and built for sport (read recreational) divers. The very compact scrubber design is for those limits rather than greater depth.

Or, directly from the source as posted here on Scubaboard


For other CCRs, like the Inspiration, the depth rating is dependent on the CE testing and certification protocol.

Semi-closed units with cmf valves are usually depth limited (ppO2 limited, really) by the gas they are using and certified with. For both the Dräger and OMG SCRs that's 40 meters with 32% nitrox (ppO2 = 1.6 ata).

Stefan[/QUOTE]

 

[caveseeker7]

[/QUOTE]

Post deleted....personal attacks not allowed by TOS
Notice posted by moderator

R. Davie

 

[divemonster]

Post deleted. Personal attacks are not allowed per TOS.