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Hi

Myself and a group of others in my club have been talking for a while about sorting out a rebreather try-a-dive, either in the pool or shallow open water (preferably). We have never really got round to sorting it out, as was wondering if anyone had any suggestions or knows of centres that run them?

Personally I'd like to try the Dolphin and Inspiration, but I'm not too fussed.

Cheers

Matt
 

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Turn up to the next dive show?

I know BSAC run a course that gets you familar with and allows you to dive with a CCR and a SCR, so the other agencies probably do as well.

All else failing, call APD and ask them about it.
 

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You can apparently do this at Fort Bill, details on their website.

HTH,

Hobby.
 

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Only the SCR Draeger Atlantis Hobby, unless things have changed since March
 

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Jeff Keep at New Frontier Diving does try dives on the Inspiration. I think the cost is £15 each with a minimum of 4 people. Must be done in a pool. Phone him on 07813666796. He also teaches all tech courses from basic nitrox to full trimix and also the Inspiration course. He is Stockport based but will travel.
 

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Hi,

We have many try dives over in the U.S and found that the pool is the best place to start. Originally started in open water but it cost us in flooded sensors and down time.

If any one would like a quick trip to LA, you could try A Prism, Mk16, Mk15/5, CCR100 sorry we moved from the Uk many years ago :) .....Warmer water...

When we ran the try dives in the UK (Now here) the most important operation was to clean the units between each diver BETADINE an iodine solution worked best thoroughly rinse out before use though.

Good luck.

Pete
 

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To anyone who hasn't yet been check out Pete's home site... awesome stuff.... Hey Pete is that you riding that cruise missile thingumebob?
 

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Andy Hayhurst is in the process of taking recipt of some Inspirations - he's an instructor for most rebreathers (inspiration to come I believe) and he was talking about providing try-dives when we were at Capenwray last Saturday. Andy - if and when you read this can you post some more details?

Regards
 

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Hi Dave,

No it's not me on the missile, it's a United States Gov Survey diver in Alaska.

Also I must add that the web site isn't a 'Home site', it's our official company site as we build systems for the US Gov as you can see from the pics.

I used to build systems in Warrington before emigrating here. Hobby asked me to post something as I used to dive with his father. The systems were initially tested in Dorothea, Vivian, Hodge Close, Eccy-Delph and many dives off Anglesey.

Never thought then I would be building stuff here in the U.S.A
 

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Pete - welcome to YD. Its a pleasure to have a man of your knowledge and experience frequenting the boards. I (and I'm sure quite a few others) look forward to your future posts, especially on rebreathers. Aaron told me a little about you when we spoke yesterday but perhaps, if you have the time, you could tell the others a little bit about yourself?

Cheers
 

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And more about the 'Prism' RB unit too please Pete!

Where are you working with the SEALs?? Off Long Beach?? Catalina Island? I used to live in RPV, so know the area well. Take care mate and looking forward to your postings.

Cheers,
 

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Hi Bren,

The training and testing was done at NEDU Navy Experimental Dive Unit in Panama City Florida. As I'm sure you know, living here on the beach without the rain and cold is really tough...but hey, someone's got to do it. :)

I miss good Fish and Chips and a proper dive site like Scapa Flow though......

Jay: Trained as a Marine Engineer in the UK, set up a company in Warrington. Rebuilt Vintage cars and Classic cars, raced a Laverda and later a Bimota (purchased, smashed, then rebuilt it)

Learnt how to dive with BSAC - specificaly North West Divers including Hobby's Dad Brian. Started on Air moved over to Nitrox then Trimix. I think we were among the first to run courses in the UK for mixed gas recreationally. Used to dive with Rob Palmer, Stuart Clough, Kevin Gurr etc.

I bought a CCR 155 from Carmellan Research in the early 90's and went sponge collecting for Smith Kline Beecham, did some work with Rob P for LLoyds of London using a computer controlled Kraken unit (Modified BIOMARINE 15/155) to survey a wreck in the Baltic "DAMM COLD!!".

Worked as a consultant engineer to Drager Germany on the SMS2000 project, got to run test dives in Jamaica to 300ft "NICE AND WARM!!"

Went around the world, after I sold the engineering company, running introductary dives with the first PRISM's, also used Prisms for the show with Martha Holmes BBC2 'Beach Watch' in the Farne Islands, She lived...Then Anglia Television in the Red Sea, 'Sail Away' was the series.

There was more stuff, magazine articles like DIVER and front pages in Scuba World but hey enough...... I got to talk at the Diving Officers Conference on mixed gas diving and rebreathers in '94.

Oh! Rob Palmer and myself were the first to get a dispensation to dive mixed gass CCRs from the HSE to work commercialy with companys like the BBC. I had to get an HSE part 4 from Fort Bovisand.

Also we recieved the Royal Mail inovation award for the PRISM - great food at the banquet, but sadly not much dosh so off to pastures new and find some cash and sunshine.

Jay you did ask @#&#36%%% If you want more let me know this is just UK stuff.

Pete
 

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What I want to know Pete, is have you ever had current limited O2 cells and what causes this?  

On a recent dive, returning from 81m, I had a strange feeling at my 15m stop and a bit of visual disturbance (bright lights at the side of my field of vision).

The cells were reading 1.3.  Since ultraviolet visual disturbance is an immediate precursor to ox tox, I immediately suspected that the cells were reading the wrong PO2 in the loop and bailed out off loop onto 10/50 mix OC. I felt better instantly.

Eventually that ran out and I went back on the loop. Same feeling again.  Once again I bailed out to my off board air bottle and began extended deco.  At 6m I was almost out of the offboard air so I went back on the loop and attempted to rack the PO2 up to 1.6 manually.  

The cells seem to be having great difficulty responding to high PO2s over 1.3. The cells are brand new but the supplier has recently advised a friend that there are a faulty batch of cells on the go right now.  

When the cells are measured on a multimeter the output is well within the acceptable range.  However, I understand that the output is not a valid indicator of the cell performance and a cell nearing the end of it's life may well still display an acceptable output range.

As an O2 cells generates more current at higher PO2, it would be a logical conclusion that if cells cannot respond to high PO2s then they have become current limited.  This would mean that in all theory I could have more O2 in the loop that the handsets are telling me.

The other theory is that CO2 retention makes a diver more susceptible to O2 and this may be the reason but I am ruling it out at present on the basis that I NEVER push my scrubber, there was no water ingress to the scrubber and it was correctly packed.  

Bearing in mind that depth and cold reduce scrubber life I factored this into the dive.  I also had no headache.  I am ruling out CO2 for the moment and tending towards the O2 theory.

My unit is an Inspiration and it passed all the pre dive checks. I calibrate both my handsets independently as there is a buffer which stores the readings and independent calibration clears the buffer and gives a better overall calibration.  

On all my previous dives, I racked up the PO2 before 6m to test the cell's responsiveness to PO2's past 1.3 and it's always been fine.

I also carry PO2 air diluent and mix PO2 tables with me in incremental depths of 5 so that I can flush the lungs and verify the cell readings against the known PO2 for the particular depth I am flushing at.  

I did perform a flush at 15 when I first began to feel strange as I first suspected that 2 cells had gone down and the voting logic was reading the one incorrect cell.  The flush confirmed that the cells were reading the correct PO2 for the depth.

I have discussed this with a few extremely experienced users and they have reported that they have also had times of feeling just a bit strange and unable to quantify why.  

I am sure it is not CNS or hypercapnia. If the problem is not related to cells then I suspect oxygen intolerance and would consider dropping my default low setpoint to 1.0 or 1.1 for the deep part of the dives then rack it up on deco.

I also had a cell warning at 6m!!!   The Inspiration list is absolutely full of posts from users reporting cell warnings and cell errors, it is very common. But I am having difficulty tracking down info about current limiting within cells. I would like to be able to confirm or rule this out as I am building up to a much deeper dive and I have to completely post pone it until this problem is resolved.

Your comments please? Oh, I am intrigued to hear of your dives with RP, they weren't in Stargate et al were they?

Rgds
 

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Hi AnneMarrie,

I have to be very careful what I post as I represent a competing manufacturer. So here are the facts as I have found them.

Yes, sensors plataeu out sometimes with no warning - the only sure test with the R17, R22 and the K1's we used to use was to run them in a pressure pot at elevated pressure to make sure we could maintain a PO2 two tenths above set point ie. Test @1.6 for 1.4 set point. Many cells are non-linear above 1.4 PO2.

As you correctly state in your Email, galvanic sensors are current devices so on some occasions the cell is unable to meet the current load for the elevated PO2 and so plateau's out at say 1.3 PO2, but it should read 1.4 PO2 or higher. We used to use sensors of different ages to limit the possibility of them dying around the same time but other factors showed up on extensive testing to be more important.

1. Water vapour on the sensing membrane causes major grief with output. Were they wet?

2. Diving with Helium on some cells affects output as it appeared on-gassing and off-gassing was not the same. Varies with different manufacturers.

3. Temperature compensation is a very much neglected field as this has to stablise output over a wide temp range and HAS to be matched to the electronics because if the load on the sensor changes from say 10K to 8-12 on the dive, this changes the output. This was an issue with corrosion on the pins on some rigs I dived.

4. Both sides of the sensor have to be open to ambient pressure so if the back of the sensor is sealed and the front open more wierdness will occur.

Most manufactures convert the current to a Mv output and use this to give them a Mv output directly proportional to the PO2. The temp compensation takes most of the power. The tapping for Mv O2 sensing the least.

We changed in the late 90's to a diffent sensor which is manufactured for us under licence here in the states as we run a much higher output in air (18-24 Mv) than those listed above but more importantly we run an analog meter which requires no battery, so when everything dies we can get home on it 24-7.

I would suggest another set of cells to see if it's that particular batch but most Cell manufactures have very stringent Q/A. The last test we do with the Prism's is response time to 90% full scale deflection, if one lags behind the others it's on its way out. This is the main test we run as output in Air doesn't help much.

The first Prism's we dived had an axial flow non insulated scrubber but we found long deep dives in cold water on this type of design reduced scrubbing time enormously. So we changed to an insulated radial flow, take a look at the early Navy test data on our web page to see how long 6lbs of 8-12 sofnolime will give you.

If you need more please email me privately.

Hope this helps

Pete
 

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Hi Pete

Great info many thanks.  I am currently trying to source different cells. I will write to you privately and explain what I am using exactly.  The non linearity you describe is definitely a problem.

Water vapour - I have already experienced the effects of this.  I had a series of dives a few weeks ago where I had a cell warning on the middle cell at the high setpoint around 40 metres.  I flushed the lungs and verified that the middle cell was the one reading incorrectly.  This is not an instantaneous error, I had noticed for a while that the middle cell was beginning to lag.  It then got to around .40 behind the other two before the cell warning bleeps kicked in.  I aborted the dive, no sense in taking the risk of another cell dying and then having to fly the unit manually.  I noticed that upon reaching the shallow stops, back at the low setpoint, the middle cell somehow caught back up into range and was fine.  I inspected the cells immediately after the dive and noted condensation on the middle cell.  The same thing happened the next day despite air drying the lid.  The position of the middle cell inside the lid provides optimum conditions for condensation to reach the cell face and impede O2 sensing.   I believe the new hammerhead electronics mitigate against this but are still in production.  

Helium - can you expand on this please.

Corrosion - the molex connections can become corroded over time and affect the cells but I have checked that this is not the case. What I have not checked is the internal wiring as this requires cutting right down the junction box and is quite involved.

Sensor sealing - there have been a batch of cells which have no holes, if you look inside, there should be a little hole on each side of the board, I understand that without these holes being punched the cell will not respond properly.  I always inspect new cells for this before fitting them into the lid.

The output is definitely not an accurate indicative as to the cell's health .  What I generally find to be of more value is to conduct the negative pressure test on the loop first and then after the loop is basically empty, I calibrate, which gives the cells a big range in which to watch the response rate of each cell and actually compare them.   I always flush the loop with diluent at the end of dives and make sure I get the O2 out as that will shorten the life dramatically if they are stored in O2.

Your comments about the reduced scrubber life certainly ring true.  At depths of 60m and above and cold long duration dives I am noticing a slight chalk taste. I never notice this on shorter shallower dives.   I never push my scrubber but I know others who do.  I believe that until there is a tangible method of visibly measuring CO2 this is one of the potentially fatal aspects of the unit.  I am actually changing my scrubber material more often than I should.   CO2 uptake is dynamic which means that if it finds a path through the material it will keep taking that route until it breaks through.  The Inspiration manual describes a certain method of packing the scrubber which I believe to be flawed.  Too tight and it will cause resistance and too loose and it will channel.  This is the bit of the unit preparation that cannot be rushed.  Sometimes it can take me up to half an hour to get a good pack!!

I have only owned the Inspiration a short while and I have pushed it quite hard.  I am already beginning to see fundamental design flaws.  The KISS is of interest to me particularly because there is no software or electronics and the O2 displays are passive - basically real time and completely independent, no voting logic.   The two types of voting logic I have heard of both seem to have the same characteristic in that a dual cell failure will result in the 1 correct cell being omitted from the loop.  I don't like this. Of coures, the KISS does not have the alarms and relies on the user to be aware of O2 metabolism. Ho hum. Horses for courses I guess. Good chatting.

Did you ever dive on the CIS LUNAR?
 
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