Impressed when scrubber disconnected.

[Neil McLeod]

Now, I am reporting this experience for two reasons: firstly because I was complacent and checked my unit before I loaded it on to a boat and not immediately predive (something I will not be repeating); and secondly because I feel it demonstrates what excellent units these are. I presently dive a Dolphin with an Oxy2 which relays PPO2 to an Aladin Oxy X.

Yesterday I assembled the unit, checked flow from dosage unit and did pressure tests. All was well. The unit was then placed on the RHIB and secured with bungie to the bottlerack. The seas were fairly calm but the unit was still moving back and forward a little with each wave.

At the dive site we tied off to the permanent bouy at slack water and I and the others got into our gear - everyone else was on open circuit. "Gas, gauge, gag" and a three minute prebreath. All seemed fine. Rolled in when told to and went to the line. Everyone happy so down we went. As we descended two things struck me as abnormal. There was a slightly increased inspiratory effort and as I descended the unit continued to sound noisy. It was still breathing easily enough and I was adding air normally to maintain neutral bouyancy. The FiO2 in the loop was higher than I would have expected. I checked my gauge and I had used 40 bar on the descent! I was now at 25 meters. I checked the valve was clicked down and nothing changed, still noisy exhalations. Reckoned I had a serious leak. I briefly considered going to bale out, but still had plently of O2 rich gas and was still able to breath it easily. As was effectively on open circuit signaled to buddy and started slow accent, relaxed 3 minute stop at 5m then slowly to surface with over 100 bar left (4 litre bottle).

Back in the boat opened the unit and found that the p-connector between the expiratory bag and the scrubber had come loose. The scrubber was mostly flooded. Now this I found strangely reassuring and a testiment to the design of these units. With such a major leak the bags cannot be distended instead they are flattened and depend on the lengths of spiral wrap to maintain a channel. The bags then work as flap valves and the second stage demand valve kicks in. Expired air is directed to the expiratory limb and then exhausted via the leak. The construction of the housing is such that you cannot fully slide the outer collar of the p-connector off the scrubber and this again limits the ingress of water.

Points:

Up to now have checked unit prior to loading and assumed that nothing came adrift on journey out to dive sites - will not assume this in future.

If something just doesn't seem quite right then the dive is over. Sort it out on the surface.

Noise (bubbles), gas consumption and too high an FiO2 equals major leak.

Can stay on "loop" as open circuit in these conditions in the sameway as if a sonic valve problem.

A flooded scrubber does not have major effect on bouyancy.

These are very clever units. ( many features which add to safety ).
--------------------------------------------------------------------

Was able to drain the scubber and bags while others completed their dive. During their surface interval did a ten minute spell on the loop to check the scrubber was still functioning. (So long as gas pathway restored and using a virtually insoluble materal will work as needs to be damp/wet to work anyway). Was then able to change to a full cylinder and drop in for the second dive (60 minutes).

Several lessons learnt and greater confidence in these units,

Neil

[Odin]

I had a flooded scrubber on my Dolphin.
Connection from exhale to scubber had come loose!
I was in 5m water practicing drills for that dive and thought it was bloody loud and a lot of bubbles.
Afterwards I remember thinking that the thing was still working (albeit Open Circuit) even when screwed!

yes nice little units but alway check the gauges!

Glad you like it!
Paul
now on the Yellow side...

[narked at 90]

hi Neil well done on surviving, dreagers are great little units to bolt and build
this scrubber connection is a bit of a known problem with p-ports, i think you where lucky, they have caused massive flooding and cocktails with out warning.
the scrubber in the dolphin dose not resist settling very well if assembled and in the unit if it is standing upright for long gurneys as well as water getting in. depending on which side of the scrubber has been compromised can be a big problem if you have a little bit of settling already.
kind regards john routley
Welcome Page

[froglee]

Originally Posted by Neil McLeod

Now, I am reporting this experience for two reasons: firstly because I was complacent and checked my unit before I loaded it on to a boat and not immediately predive (something I will not be repeating); and secondly because I feel it demonstrates what excellent units these are. I presently dive a Dolphin with an Oxy2 which relays PPO2 to an Aladin Oxy X.

Yesterday I assembled the unit, checked flow from dosage unit and did pressure tests. All was well. The unit was then placed on the RHIB and secured with bungie to the bottlerack. The seas were fairly calm but the unit was still moving back and forward a little with each wave.

At the dive site we tied off to the permanent bouy at slack water and I and the others got into our gear - everyone else was on open circuit. "Gas, gauge, gag" and a three minute prebreath. All seemed fine. Rolled in when told to and went to the line. Everyone happy so down we went. As we descended two things struck me as abnormal. There was a slightly increased inspiratory effort and as I descended the unit continued to sound noisy. It was still breathing easily enough and I was adding air normally to maintain neutral bouyancy. The FiO2 in the loop was higher than I would have expected. I checked my gauge and I had used 40 bar on the descent! I was now at 25 meters. I checked the valve was clicked down and nothing changed, still noisy exhalations. Reckoned I had a serious leak. I briefly considered going to bale out, but still had plently of O2 rich gas and was still able to breath it easily. As was effectively on open circuit signaled to buddy and started slow accent, relaxed 3 minute stop at 5m then slowly to surface with over 100 bar left (4 litre bottle).

Back in the boat opened the unit and found that the p-connector between the expiratory bag and the scrubber had come loose. The scrubber was mostly flooded. Now this I found strangely reassuring and a testiment to the design of these units. With such a major leak the bags cannot be distended instead they are flattened and depend on the lengths of spiral wrap to maintain a channel. The bags then work as flap valves and the second stage demand valve kicks in. Expired air is directed to the expiratory limb and then exhausted via the leak. The construction of the housing is such that you cannot fully slide the outer collar of the p-connector off the scrubber and this again limits the ingress of water.

Points:

Up to now have checked unit prior to loading and assumed that nothing came adrift on journey out to dive sites - will not assume this in future.

If something just doesn't seem quite right then the dive is over. Sort it out on the surface.

Noise (bubbles), gas consumption and too high an FiO2 equals major leak.

Can stay on "loop" as open circuit in these conditions in the sameway as if a sonic valve problem.

A flooded scrubber does not have major effect on bouyancy.

These are very clever units. ( many features which add to safety ).
--------------------------------------------------------------------

Was able to drain the scubber and bags while others completed their dive. During their surface interval did a ten minute spell on the loop to check the scrubber was still functioning. (So long as gas pathway restored and using a virtually insoluble materal will work as needs to be damp/wet to work anyway). Was then able to change to a full cylinder and drop in for the second dive (60 minutes).

Several lessons learnt and greater confidence in these units,

Neil

Thanks for sharing this,it is an interesting post.

I must say I read this with horror and amazement that you got away with it so easily and was unaware that it was still possible to even breathe the unit in such circumstances.I would have bailed out,as you say,at the first sign there was something not right and sorted it out on the surface.But I have also learnt something from this as well.I was unaware that the scrubber would function when or after being completely flooded...I know it gets a bit damp sometimes and even a bit solid but I thought when water was added it no longer functioned,surely the kitty litter is at least porous and the whole scrubbing reaction would be greatly retarded if there was water coating everything...what about the 'caustic cocktail' effect?I thought you would get a mouthful of sodalime solution through the inhalation hose? With all due respects,I'll think I'll leave trying that one myself.

I think about the worst I ever experienced was in my first year with the unit when I got a lot of water in the exhalation hose as a result of getting hit by a wave on the surface starting a dive....this was my early days with the unit and I did not like the feeling of breathing through a bubbly straw which seemed to get worse... so at 25m I baled out onto the 3l and very glad I was that I had a stage 3l as well.It gave me a fright but was probably me being over cautious .Really nothing compared to this though.

[narked at 90]

sorry for the cut and post but this is from Ron Micjan's web site and is a sobering reminder that shit happens even when you may think you kit is great....

The caustic cocktail, a personal experience.

Many of us have heard the term used in rebreather diving called the “caustic cocktail”. From stories of just a bad taste in the mouth all the way to a lung full of nastiness. Until yesterday I had just experienced the bad taste in the mouth variety and then only once. Yesterday I was doing a dive with my friend Kent, we hadn’t made any formal buddy arrangements (I think divers in the PNW invented the term “same ocean buddies”) but just happened to run into each other a couple minutes into the dive. We were poking around the bottom of a wall at about 145 fsw, looking at very large urchin shells that were no longer occupied. I had about a minute of NDL left and began to move up the wall, Kent was about 20 feet away and 10 feet deeper than me. Its Interesting how fast things can change. With absolutely no warning, one breath of gas changed into a breath of liquid. I instantly had a mouth and throat full of sodalime dissolved in sea water. My trachea spasmed (that probably kept me from drowning) and blocked the mixture from my lungs but sent some into my stomach. Pulling the mouth piece out and closing the DSV took a couple seconds and I was holding my breath and spitting up into the water while the panic was rising in my brain. Fighting that off I knew I needed to breathe soon and took hold of my Air 2 that was plumbed to my air diluent cylinder and put that into my mouth, cleared it of water and took a tentative breath. Air is good. I looked over at Kent and waved my light at him a few times, no response, he was looking the other way. With only a 13 cf diluent cylinder, that was not full when I started this dive (mistake one) I knew that I only had a few breaths at the 135 foot depth I was at. I had neglected to bring along a larger bailout cylinder (mistake two) as I was not expecting to do any deco diving this trip. I headed for the surface, keeping my airway open and exhaling any time I was not inhaling off my very limited gas supply. At that point I wasn’t sure if I had the gas to make it to the surface, but I decided that I was going to make it, no ifs, ands or buts about it. I ascended the 135 feet in about 90 seconds, not the safest ascent rate in the world but the options were, as you might guess, limited. I hit the surface and waved to the skiff, not the usual diver OK but the two hands crossing above the head distress wave. Al wasted no time getting the skiff over to me and I climbed aboard all the while coughing, spitting and vomiting my lunch out, and gasping for breath. I washed my mouth out repeatedly with fresh water and asked for the onboard oxygen bottle, which Al handed down quickly. I cranked it up to 15lpm and started sucking it down. I was not feeling any symptoms of DCI but wanted to nip it in the bud if I could. The length of my bottom time, 17min, the fact I didn’t enter deco, 18 hours since my last dive and the relatively controlled ascent was evidence that I probably wasn’t going to get bent, hard. I wasn’t taking any chances, I used the whole cylinder. Then swapped my dil reg over to my O2 cylinder and started using that. By that time most of the divers were up, but some had not heard the recall and were still diving. I had this horrible burning sensation in my throat and mouth, swallowing was near to impossible and coughing hurt like hell. This was not fun. Still no DCI symptoms, Colby, the divemaster was coming by to check on my frequently and when Donny, the other divemaster, returned to the boat from his dive, he took over my looking after. He holds up three fingers and says, “how many?” I crossed my eyes and held up one finger back at him. His reply, “you’re back”. Donny knows my sense of humor.

A boat ride back to the Nautilus, off with the dry suit, plenty of water, some medical attention from Kim, a nurse who was a guest on the boat and a very sweet lady, (thanks Kim) and things gradually headed back to normal. My throat was still sore, everything, including water, tasted like crap, but with no signs of DCI, I figured the worst was over.

Its now the next day and my throat is still sore, my voice is mostly gone, similar to a case of laryngitis, and I am sitting out the morning dive and writing this article.

I took the unit apart last night and found that my scrubber lid was leaking. Either from not being tight enough, or something caught under the seal. The unit had passed the positive and negative pressure checks, but I'm thinking that when it hit the cold water it may have shrunk the rubber seal enough to allow water to trickle in, slowly filling up the canister until it overflowed into the inhale loop. I felt no increase in work of breathing, heard no gurgling, and tasted no difference in the loop, until I had a mouthful.

My lessons learned: Either fill the dil bottle before every dive, or carry a bailout cylinder with enough gas to ascend at a slower rate. (This is of course only for recreational, no deco, diving, I still carry 2 sling bottles on deco, deep, trimix dives).

In the end, the only thing that saved me was my training and just plain stubborn determination to not die. I thank my original drager instructor, Alan Studley, for the training that put me on this course of discovery into rebreathers and provided me the tools to stay alive when the shit hit the fan. Thanks Alan.

My advice to my fellow RB divers, previous performance is no guarantee of continued results. I told someone the day before this happened that I had never had a flood of my loop. I should have added the word, yet. My mistake was not in having a loop flood, but in not being prepared for that eventuality, yes I had some onboard dil accessible from OC, but not near enough. If I had been delayed in my ascent for any reason, I probably would not be here today to tell this story. The absolute number two thing in RB diving is HAVE A BAILOUT PLAN. Number one is of course know your PPO2. Don’t just assume you will never have a flood. I HAD BECOME COMPLACENT!!!!! Don’t let this happen to you. I was lucky, and I had a survival mindset, its what brought me back. Don’t depend on luck, have a plan that you know will work. How will you know it will work? Test it, see how long it takes you to bailout, you can do this shallow and have a buddy time you, then do the math for the same thing at depth, calc your OC bailout gas and then double that number, carry it every dive, even when you are feeling lazy.
It is said that what does not kill you makes you stronger.

Thanks to Mike Lever and the crew of the Nautilus Explorer for their timely help, care and professionalism.

Ron Micjan
4 June 2004
Port Hardy, Canada

[froglee]

The BSAC rebreather team recommend that for 30m+ diving with the SCR Dolphin,you carry at least 5l of baleout.The 3l baleout is just not enough for a proper ascent with the stop[especially if you are a bit unnerved when having to go over to baleout.]As the standard unit is not really geared up for anything larger than a 3l baleout in the side cylinder pouch,I would suggest a further 3l stage cylinder with air slung either under the shoulder or across the front.I have also seen another 3l cylinder mounted on the other side of the case,which seems sensible.Alternatively you could go for a 10l main nitrox cylinder with an H valve,but even so,I personally would still feel happier with a complete alternate air supply.
Interested to see what others think.

[Freeflow]

For no deco dives at less than 25m I tend to stick to the 3L pony...a full 3L pony. Having used about 30 bar per dive for suit/wing inflation and pre dive checks to these depths, on a second dive 170 bar isn't a lot to get you out of trouble.

For deco dives I run the "trimix" set up with a 7L stage mounted on the left [to counterbalance the 3L on the right].

Suit and deco/bailout gas comes from the stage with reserve suit and wing from the 3.

To comfortably mount a stage you need soem extra D rings, which are easy enough to attach. Pic of the 7L is below, excuse the shirt! The tank sits better underwater, I'll have to get a piccy of it when I'm next diving that configuration.