Michael Thornton
Rebreather Enthusiast
A lot of rebreathers can be set up as mCCR it's just a matter of adding an orfice or needle valve.
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Redundancy- Waste of time?
- Thread starter Ben Field
- Start date
A lot of rebreathers can be set up as mCCR it's just a matter of adding an orfice or needle valve.
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How do you monitor your PP02 doing a touch contact blind exit? do you let go the line or the other diver every 3 mins?
I am a massive fan of MCCR but i wouldn't dive one without a HUD because I know hand set diciplin is a variable and the incident pit loves a variable
CCR full cave course blind (eyes closed ) exit drill on a KISS MCCR Air dill PP02 droped to 0.15 due to task loading. Patrick spotted my flashing HUD
Mark i thing that once you know your set point at the begining, it is quite easy to mantein a safe ppo2
Mainly in a KISS. (At constant depth how i can see in the graph, just try to be focused on the loop volume)
Joaquín
Michael Thornton
Rebreather Enthusiast
True but most cave exits are not a constant depth so it would not be wise to just try and feel the counterlung volume depleting and making up that volume with O2 if you were unable to verify your PO2
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garethingham
New Member
You guys cannot be serious? Are you saying that you are happy to guess your PP02 when diving blind in a cave (regardless of the profile)? Michael, your response implies that is a no no on variable cave profile but OK on a fixed profile. You are blind, how do you know what the exact profile of the cave is? In shallow caves like Mexico, this sounds like a fantastic way to top yourself really quickly.
PeterN
Active Member
Mark was a victim of a foolish skills test. He should never have been expected to run his unit without PO 2 feedback. As has been already mentioned, always know your po2 is the rule. Loose that.... Bail out. Loop volume as PO2 feedback.... not for me!
Peter
garethingham
New Member
Agree, Mark was not at fault...his instructor should have known better. I am more worried about the other comments discussing how this "could be done".
Michael Thornton
Rebreather Enthusiast
I am not implying it is ok. Read the entire thread I said I dive exclusively with a HUD, I also stated that always knowing your po2 is the number one rule, and I accused Mark's instructor on not performing this skill in a safe, controlled manner.
I was just giving a specific reason as to why I do not think it would be wise to stay on the loop without a means of monitoring your PO2. I was agreeing that one way to tell when you need to add O2 is when you feel the lung volume diminishing but this should be confirmed by a PO2 display of some sorts.
Michael Thornton
Rebreather Enthusiast
"Could be done" and it "being wise to do" are very different. It COULD be done but it shouldn't. It is simple physics that it COULD be done but on a blind exit it is a terrible idea and should not be attempted, if by blind it means you have no way of monitoring your PO2 which I have not experienced. My HUD can be pushed against the glass of my mask so I can see it.
garethingham
New Member
Hi Michael,
Sorry, I am going to have to disagree with you again: "I was agreeing that one way to tell when you need to add O2 is when you feel the lung volume diminishing".
This assumes 100% integrity of the loop. How many times have you seen small leaks from around the top of peoples masks that they are unaware of. Trapped hair, face muscle movement etc. That small leak is diminishing loop volume.
"...this should be confirmed by a PO2 display of some sorts.". Agree with this but disagree with the start of the statement as humans always look for shortcuts in a process, saying you could...but shouldn't will have people only reading the piece that say's "it can be done".
I would prefer a statement which say's: Validating loop PP02 should only be done with a PP02 display and cross checked regularly with a diluent flush or rebreather cell validation mechanism.
Sorry, I am going to have to disagree with you again: "I was agreeing that one way to tell when you need to add O2 is when you feel the lung volume diminishing".
This assumes 100% integrity of the loop. How many times have you seen small leaks from around the top of peoples masks that they are unaware of. Trapped hair, face muscle movement etc. That small leak is diminishing loop volume.
"...this should be confirmed by a PO2 display of some sorts.". Agree with this but disagree with the start of the statement as humans always look for shortcuts in a process, saying you could...but shouldn't will have people only reading the piece that say's "it can be done".
I would prefer a statement which say's: Validating loop PP02 should only be done with a PP02 display and cross checked regularly with a diluent flush or rebreather cell validation mechanism.
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dspe
New Member
This post is going a bit of toppic ,i know you can run any ccr as a m by adding a needle valve but then you should remove all the eccr bits just cells hud primery no bells as ben said a hilux that can be repaired with a hammer!!
Ben Field
All IMVHO obviously...
Its Off Topic and far from my ideal but currently I have an Inspiration loop with bespoke MCCR head, BMCL and hydrogom valve. (A European KISS if you like!) I am not totally averse to ECCR just never found one sufficiently rudimentary to suit diving IMO!
Yes, although there is alot more work to do removing the ECCR parts to make a true MCCR
However the primary issue is that you are then diving a modified unit- no possibility to do training, get certifications which are required for insurance and to satisfy some holiday companies, fine for bashing about in the UK on individual trips but a nightmare if you are in a club with regards liability. These things don't matter if you're a dive bum but as a father, husband and company director I have responsibilities, IMO I am doing the "right" thing in diving the best, safest unit that I can... but it means I am off the grid and untouchable to services that people diving some off-the-shelf death box can access! Its a retarded situation we seem to have made for ourselves.
Back on topic- wrt blind cave exit, I did mention in the original post that I considered cave diving outside the scope of my redundancy question- clearly with no clear route to surface and enforced exit course a higher level of redundancy would be sensible because staying on the loop is that much more beneficial.
Its not a type of diving I do but I think a mask mounted HUD would be the solution, preferably a NERD with full PPO2, deco and depth info (I still don't really like the fact its DSV mounted to be honest)
For the diving I do, other than small amount of wreck penetration, I always have the option of bailout to OC, bag up and ascend directly, as such redundancy is a minor concern compared to a reliable unit in terms of its primary systems. In my mind the main rebreather should be sufficiently reliable that the only event to take it off-line will be one that would force me to OC bailout anyway, therefore mutiple redundant layers are redundant!
dspe
New Member
Its Off Topic and far from my ideal but currently I have an Inspiration loop with bespoke MCCR head, BMCL and hydrogom valve. (A European KISS if you like!) I am not totally averse to ECCR just never found one sufficiently rudimentary to suit diving IMO!
Yes, although there is alot more work to do removing the ECCR parts to make a true MCCR
However the primary issue is that you are then diving a modified unit- no possibility to do training, get certifications which are required for insurance and to satisfy some holiday companies, fine for bashing about in the UK on individual trips but a nightmare if you are in a club with regards liability. These things don't matter if you're a dive bum but as a father, husband and company director I have responsibilities, IMO I am doing the "right" thing in diving the best, safest unit that I can... but it means I am off the grid and untouchable to services that people diving some off-the-shelf death box can access! Its a retarded situation we seem to have made for ourselves.
Back on topic- wrt blind cave exit, I did mention in the original post that I considered cave diving outside the scope of my redundancy question- clearly with no clear route to surface and enforced exit course a higher level of redundancy would be sensible because staying on the loop is that much more beneficial.
Its not a type of diving I do but I think a mask mounted HUD would be the solution, preferably a NERD with full PPO2, deco and depth info (I still don't really like the fact its DSV mounted to be honest)
For the diving I do, other than small amount of wreck penetration, I always have the option of bailout to OC, bag up and ascend directly, as such redundancy is a minor concern compared to a reliable unit in terms of its primary systems. In my mind the main rebreather should be sufficiently reliable that the only event to take it off-line will be one that would force me to OC bailout anyway, therefore mutiple redundant layers are redundant!
So not alot to chose from and as being in europe i like things close to home i dont like sending things to the US the best out there so far although not mccr was the deep pursuit shame they no longer get made.
Ben is your head any empty one from narked what computer and hudare you using?
Ben Field
All IMVHO obviously...
Yes, although it could be argued the JJ head has some common elements
I used a blank head, it came to me second hand, could be N@90.
I use a Shearwater GF, no HUD- most stock HUD's take too much effort to read with me being colour blind
When I win the lottery might jump straight to a NERD if they consent to do a Hardwired one. Not an option yet as they cost more than my whole rebreather!
Uwe Sieg
UweS
Hi Johnnyh / Very jealous of your Sentinel. This is probably the unit I should have bought in the first place.
The O2ptima's original configuration were 2 independent HH Rev-C Handsets. One of the main reason that I bought the unit was the good reputation of HH electronics. (According to my Instructor who dives a double Rev-C configuration. After all, this is not an Ipod but a life sustaining device)
When HH announced the new Rev-D Handset and Xtreme DIVA option I was stoked. (as you mentioned, Deco on the HUD rocks). The rest is history. In about 50 hrs of diving, one flooded DIVA,(bought the sealed upgrade), numerous Primary re-boots due to power issues on the unit, one Rev-C motherboard failure. (Upgraded both units to the bigger Battery Exp case).
The reason I am mentioning this is not to point out the problems with the HH electronics but that during the Handset upgrade I was offered the option of the Shearwater Primary controller & HUD. I have opted to give the HH Exp cases a last try mainly due to cost considerations. (The USD trades 1:11 in our country)
However this I promise for everyone to read, let there be one problem with the upgraded HH electronics and I will go over to the Shearwater option without a second thought, maybe even sell the O2ptima and buy a Sentinel. (The Pound trades 1:16 at the moment but what the heck)
Johnnyh
Dude
Just speaking personally, for my desires, mindset, and style of diving, a perfect world setup would be the Aurora Blue with NERD running off the second set of three cells. (and this is hypothetical of course, as the AB is not available yet).
Ben, I'm sure you already know this, but the new Shearwater DiveCAN HUD has a colorblind mode (I'm colorblind too).
Analog signals and the marine env don't make good bedfellows, so DiveCAN or the like is very high on my list.
John Hanzl
Author, Out of Hell's Kitchen
www.outofhellskitchen.com
Ben, I'm sure you already know this, but the new Shearwater DiveCAN HUD has a colorblind mode (I'm colorblind too).
Analog signals and the marine env don't make good bedfellows, so DiveCAN or the like is very high on my list.
John Hanzl
Author, Out of Hell's Kitchen
www.outofhellskitchen.com
Ben Field
All IMVHO obviously...
Yes, thanks. I have spoken to Bruce about colour blindness since the first colour Shearwaters. I wish they had done a Red-Blue HUD.
I have been watching the spread of DiveCAN, its nice and clever but I wouldn't dive it with plugable cables as its always shown, when they do a hard wire connection from sensor module to handset (or better still NERD) I'll become interested, until then its just a bling toy IMO and the touted redundant features are largely irrelevant to 99% of users who will bailout when in doubt as they where taught.
In what (diving) scenario are monitor and control components you can remove necessary?
Its the introduction of potential issues for the sake of being clever and occasional maintenance ease at the detriment of diving safety I find must distasteful about many of the "redundant" features that manufacturers seem to like adding and advertising as features.
Johnnyh
Dude
Can't agree with you more regarding what is marketed to you vs what you actually need. As a DSO with 110 divers to worry about, I have a strong KISS mantra, and certainly the amount of crap marketed to the general recreational diving market is nothing short of astounding. However us "adults" who have pursued the outer fringes of non-commercial diving are, I certainly hope anyway, more buttoned up as divers and therefore are at least slightly less prone to being bowled over by needless "conveniences". It's more of a matter of understanding, in today's slightly more mature rebreather technology, what truly is a convenience and what is an evolution.
Case in point - I don't think it's the best idea to have a Fisher connection on an analog signal line. These connectors were not developed for this intended use, and analog is far too susceptible to impedance changes and the like. However, a digital signal on a cable with a connector designed for the ROV market that's gas tight - well, that's an entirely different issue. Keep in mind - even if the DiveCAN bus connector from your wrist computer to the rebreather head pops apart due to a snag, for instance, the setpoint controller in the head could care less - it'll continue to monitor the O2 and fire the solenoid at the given setpoint. Same with the HUD. And since these connectors are wet-matable, the diver can reconnect (or have buddy do it) and the system is okay (though the connector contacts will need a good cleaning after the fact). Or not - go to OC and use the wrist computer in OC mode - it's not been compromised.
I use the same connector technology in my divers' comms systems for presentations and for aquarist work - it's a very different beast than the Fisher.
In the boating industry back around 2004 or so people were up in arms at the new EPA Tier II standards that were basically making electronically controlled diesels mandatory. They said that the computers were not to be relied on, that the common rail technology was too finicky, and that it was putting boaters at risk (ignoring the fact that truckers had been using electronically controlled diesels for many years already). This fear was wrong - and the electronically controlled diesel has really revolutionized the boating industry. (I may be slightly biased though, as I'm flying down to Stuart FL this weekend for a marine survey on a 38' 2006 Sabreline Hardtop Express that I hope to buy. She has twin 380hp Cummins QSB 5.6 electronically controlled diesels, so it's on my mind right now And oh, what a great dive platform!).
So my point is this - just like the advent of the electronically controlled diesel engine, I think the adoption of DiveCAN-like digital comms bus with wet-matable connectors is an evolution rather than a convenience.
John
Ben Field
All IMVHO obviously...
I agree about Fischer, utter sh*te.
I totally understand the DiveCAN system but why plug able? There is no s*dding point at all that I can see...
If you went into Hospital would you choose the bed with the monitors plugged in or where they are wired into a fused spur?
Safety over Convenience every time please
lizardland
Active Member
Have you looked at Colkan's controllers? They did a digital version of the Mk15 analogue pod. Very simple, holds a constant SP. No bloat, no other crap on it, just a SP controller and simple light display driver.
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