Question SCR Semi Closed Rebreather

[L13]

HP100's and LP72's are about the same volume so the ratio is about the same.
I'll refrain about commenting about the LP50 as a pony bottle, not worth opening that can of worms.

I'm with @Dann-Oh , I'd like to her your opinion too!

 

[flymolo]

Hey all I am looking for some basic information on SCR units. I am looking for extended bottom time within Recreational diving limits(my current depth limits are 130FSW and no decompression). I'm currently diving single back gas (AL62, LP72, HP100) and sidemount (I have a set of both LP72 and LP50 for side mount). I was talking with a tech in my LDS and he mentioned I may want to look into SCR units for extending my bottom time within Recreational limits. I do have desire to eventually get into tec for deeper wreck dives (one is the Infadel in 150FSW and a second is UB88 in 190 FSW), I do know I want to wait until my kid(s) is/are older.

I don't really have many friends that dive rebreather at the moment but I do know there is a local community but im not a part of them yet.

Thoughts on going with an SCR at this point in my dive career?

Just dive doubles...

 

[Dann-Oh]

Just dive doubles...

As I said in another post, I can't dive doubles due to limited range of motion in my right shoulder. I can't reach isolator valve with my right hand.

 

[flymolo]

As I said in another post, I can't dive doubles due to limited range of motion in my right shoulder. I can't reach isolator valve with my right hand.

Sorry. I didn't see that. If your limited range of motion is not related to injury and can be improved by stretching, I would say do that. If not, you already dive sidemount, so what would you hope to gain by moving to an SCR for recreational diving? Keep in mind the LDS is going to suggest you buy an expensive piece of gear if they are in the business of selling expensive pieces of gear...

 

[Marie13]

As I said in another post, I can't dive doubles due to limited range of motion in my right shoulder. I can't reach isolator valve with my right hand.

Then just go SM. You’ll have the valves right under your armpits, easy to reach. Much cheaper than SCR/CCR.

 

[Dann-Oh]

Sorry. I didn't see that. If your limited range of motion is not related to injury and can be improved by stretching, I would say do that. If not, you already dive sidemount, so what would you hope to gain by moving to an SCR for recreational diving? Keep in mind the LDS is going to suggest you buy an expensive piece of gear if they are in the business of selling expensive pieces of gear...

Unfortunately, the limited range of motion is a result of an old injury. too many mountain biking crashes in my younger years. The topic of SCR was not brought up by my local LDS sales team it was brought up by the service tech who I have been talking to about technical diving (he and a few others I know). I didn't know anything about SCRs and the info on the internet is a little scarce so that's what prompted me to post here.

Then just go SM. You’ll have the valves right under your armpits, easy to reach. Much cheaper than SCR/CCR.

I already dive side mount. This was stated in my original post and several other posts.

 

[Robert H. Diver]

Unfortunately, the limited range of motion is a result of an old injury. too many mountain biking crashes in my younger years. The topic of SCR was not brought up by my local LDS sales team it was brought up by the service tech who I have been talking to about technical diving (he and a few others I know). I didn't know anything about SCRs and the info on the internet is a little scarce so that's what prompted me to post here.


I already dive side mount. This was stated in my original post and several other posts.

So we’ve established that you already dive sidemount but are NOT nitrox certified. You should be signing up for a nitrox course TODAY….that will extend your NDL a bit, hopefully to your liking.

 

[Dann-Oh]

So we’ve established that you already dive sidemount but are NOT nitrox certified. You should be signing up for a nitrox course TODAY….that will extend your NDL a bit, hopefully to your liking.

Yes thats correct. I was mostly looking for more info on SCRs when I made my original post, I think in my mind I have shifted from the question "Is an SCR right for me" to "What is an SCR and what is it a tool for"

I don't know anything about SCRs and the info on the internet is a little scarce so that's what prompted me to post here.

From this thread I have gathered:
1) I should get into Nitrox
2) SCRs are more a "gas extender" than a CCR (Im sure I'm explaining this wrong).
3) SCRs are still limited by NDL, I'm not too sure what that means when compared to a CCR.


I hope this response doesn't come off as being a jerk or immature. I genuinely enjoy learning new stuff even if I don't use the skills.

 

[broncobowsher]

NDL on CCR is only slightly better than OC. Deco is a little better (depends on the dive).
CCR dive times are typically limited to having adequate bailout, not the rebreather itself.

 

[GiraffeMarineSalvage]

3) SCRs are still limited by NDL, I'm not too sure what that means when compared to a CCR.

I generally benefit a lot from hearing "Why" something is a certain way so I'll do my best to provide an extreme over-simplification as to why your no decompression limitations at recreational depths are directly impacted by a combination of your depth AND the amount of nitrogen in the gas you are breathing. Therefore if you reduce the percentage of nitrogen in the gas you are breathing by replacing some of the nitrogen with oxygen you will have less nitrogen on-gasing and therefore less nitrogen which needs to off-gas on ascent. BUT, as you will quickly learn in a nitrox course, too much of a good thing is a bad thing and the higher the oxygen percentage in the gas you are breathing the shallower your safe MOD (Maximum Operating Depth). Never dive below the MOD of a given mix, period. Also make sure you are certain of the percentage/MOD, and don't take anyone else's word for it (literally it is important enough no one will ever be offended, and if they had any issue with you confirming the mix yourself you should go somewhere else: wrong mix + wrong depth = potential death).

To extend into an over simplification of the SCR dives and NDL under 100 feet, with a CCR you are basically custom mixing your own nitrox for the precise depth you are at in any given moment (ie breathing the most oxygen possible without being toxic, and therefore the least nitrogen) so you enjoy a much longer NDL than if the percentage of oxygen you could breathe for the entire dive was limited to the amount of oxygen which was safe at the deepest portion of your dive. An SCR is going to be tailored a given maximum depth prior to the dive, just like OC using a given nitrox percentage, therefore SCR ends up reducing gas consumption but can't have much impact on NDL while still having most of the cost of increased complexity relative to an mCCR... Like many middle grounds under certain circumstances it might be perfect (especially as someone above said under a unique constraint like if you can't get pure oxygen locally...), but overall nowadays there are some really awesome CCRs that aren't much more complex than a SCR (such as my Triton or many form members Choptimas) while providing many dramatic benefits well above and beyond what an SCR can..
The best value, especially for intermittent diving before taking leap to CCR, is the combination of a nitrox course and a decompression procedures course with bigger tanks in my opinion.