Loop floods?

abowie · 2nd October 2005, 04:07

Quote: (Originally Posted by JimC)

A conservative estimate for me is that take one Aluminum 80 for every 2000' of cave I have to swim out of at 100 feet depth. I plan less distance per bottle if the cave is low flow.

How did you decide on this figure for bailout?

Just doing some rough maths on this, with an RMV of 20l/min you're relying on being able to swim at a speed of 0.9mph to get out of the cave in time. With a functioning scooter this would be a doddle, but without it it might be a big ask particularly if the cave was tight.

I'm not being critical. I'm genuinely interested in how people go about making the decision about what is adequate bailout with a CCR.

***EBT*** · 2nd October 2005, 10:52

For me, I swim reliably at 15m/min with the CCR and up to 3 stages and with an RMV of typically 11-14LPM. My calculations are based on an RMV of 20 LPM (a little reserve doesnt hurt).

My bailout is planned around this.

JimC, I had the very same O2 issue, you can reliably fly the unit on the tank valve, I did for 90 minutes

AD_ward9 · 2nd October 2005, 16:23

I´ve had 3 complete floods over the years:
1. YBOD, hose fitting on top of scrubber canister was screwed down tight, with O ring in place, but not keyed properly. The keying is very shallow. When screwed down it passes + and - pressure tests indefinitely. When knocked, it skids sideways and opens up the top of the scrubber to a lot of water. Caused a CO2 hit and a cocktail.

2. Breathing hose popped off a fitting. It had been "borrowed" for an experiment on another rebreather, cable ties removed and not put back. It does pass pressure tests that way, but does not stand a pull.

3. Hole in hose for no obvious reason. It circled around fast (a moulded hose).

Plus a few partial floods.

Learnt early on that gurgle gurgle, means bail out now, pump, then test it out carefully before going back on the loop. Do that as soon as there is a gurgle, and carry loads of bail out, then loop floods are no big deal. On first flood, I paused to think about the gurgle, and CO2 rocketed, so pause got longer ...

One of most interesting ways of getting a leak I discovered over the years is rubber loving sea stars. There were lots of them on a boulder and sea bed: looked really pretty. Put my hand on the boulder, and it was like the whole surface of the boulder scampered fast onto my hand and my arm, then started biting lumps out the neoprene. I rose up a couple of yards and was pulling them off, but even if the head only has one leg, they keep on biting. Sea stars are quite resilient. Cost me a pair of gloves. Could be quite interesting when they get to inhabit the wreck alongside, when a diver goes inside. This was nowhere exotic, and only 140ft: a certain popular wreck in Scapa Flow (only one wreck at 140ft in Scapa). Odd response: the giant octopus off British Colombia hate neoprene - when you want them to go away, just peel back a seal, touch them and off they go. Wonder where the sea stars got a taste for neoprene and rubber? Also, where they learnt to move so fast? How do they talk to each other?

Alex
NB: Just to be clear, the stars did not cause me a flood, but quite a few holes. Touch them with a hose, and I am sure it would leak quite fast.

silent running · 6th October 2005, 04:04

Hello Mike, here's my flood list:
-Flooded Dolphin scrubber resulting from false positive mf'n p-connector. Happened in the first 10 minutes of a shallow night dive. Aborted and stayed in heads up position on the gurgling loop. No cocktail
-Flooded exhale CL on Prism. Old style fitting at top of bag came loose. No water made it to the scrubber. Didn't even know I had 3 cups of water in the bottom of the lung until the end of a 3hr dive and still breathed great. Could have blown it out of the drains, but by then it didn't seem worth the bother.
-Small leak on Prism scrubber seals discovered on descent. Water stayed on the bottom of the scrubber under the canister. Aborted dive, stayed on the loop. Replaced pinched O ring got back in water.

As you can see, all mine were minor and only the Dolphin would have turned into a total flood if I had not caught it. Reading the other posts, it seems a true total loop flood is very rare. Still, I think it's essential to be able to drain the loop as it seems most floods are the kind you could recover from, where drains are useful. I think the biggest threat of TLF would be from hoses being cut by obstacles, which is why I plan to get some of those niffty nomex hoses for the head-CL part of the loop. I guess another would be the mouth pc slipping out due to an O2 hit. With this in mind, I tried the Manta Bite on my Prism this last trip. The rebreather size fit the DSV very well, but the wings of the thing really push out against your cheeks, which is not comfortable and feels similar to having the dreaded chipmonk cheeks. Could not get used to it. Hey what happened to your pre-pubescent, slack jawed girl avatar? I couldn't stop laughing everytime I saw it. Bring her back!-Andy

2nd October 2005, 04:07	#11 (permalink)
abowie Fighting Girl Current Rebreather/s: Sport Kiss Other Rebreather/s: Join Date: May 2005 Location: Land of Oz Posts: 574	Quote: (Originally Posted by JimC) A conservative estimate for me is that take one Aluminum 80 for every 2000' of cave I have to swim out of at 100 feet depth. I plan less distance per bottle if the cave is low flow. How did you decide on this figure for bailout? Just doing some rough maths on this, with an RMV of 20l/min you're relying on being able to swim at a speed of 0.9mph to get out of the cave in time. With a functioning scooter this would be a doddle, but without it it might be a big ask particularly if the cave was tight. I'm not being critical. I'm genuinely interested in how people go about making the decision about what is adequate bailout with a CCR. __________________ Andrew Bowie Rebreather-friendly Buddy
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2nd October 2005, 10:52	#12 (permalink)
*EBT* Apprentice Luddite Current Rebreather/s: Classic Kiss Other Rebreather/s: Inspiration Classic Join Date: Feb 2005 Location: UK, Brighton Posts: 2,147	For me, I swim reliably at 15m/min with the CCR and up to 3 stages and with an RMV of typically 11-14LPM. My calculations are based on an RMV of 20 LPM (a little reserve doesnt hurt). My bailout is planned around this. JimC, I had the very same O2 issue, you can reliably fly the unit on the tank valve, I did for 90 minutes __________________ Eagles May Soar, but weasels don't get sucked into jet engines! RBW Terms of service
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2nd October 2005, 16:23	#13 (permalink)
AD_ward9 RBW Member Current Rebreather/s: Other CCR Other Rebreather/s: Other CCR Join Date: Jun 2005 Location: Scotland Posts: 2,080	I´ve had 3 complete floods over the years: 1. YBOD, hose fitting on top of scrubber canister was screwed down tight, with O ring in place, but not keyed properly. The keying is very shallow. When screwed down it passes + and - pressure tests indefinitely. When knocked, it skids sideways and opens up the top of the scrubber to a lot of water. Caused a CO2 hit and a cocktail. 2. Breathing hose popped off a fitting. It had been "borrowed" for an experiment on another rebreather, cable ties removed and not put back. It does pass pressure tests that way, but does not stand a pull. 3. Hole in hose for no obvious reason. It circled around fast (a moulded hose). Plus a few partial floods. Learnt early on that gurgle gurgle, means bail out now, pump, then test it out carefully before going back on the loop. Do that as soon as there is a gurgle, and carry loads of bail out, then loop floods are no big deal. On first flood, I paused to think about the gurgle, and CO2 rocketed, so pause got longer ... One of most interesting ways of getting a leak I discovered over the years is rubber loving sea stars. There were lots of them on a boulder and sea bed: looked really pretty. Put my hand on the boulder, and it was like the whole surface of the boulder scampered fast onto my hand and my arm, then started biting lumps out the neoprene. I rose up a couple of yards and was pulling them off, but even if the head only has one leg, they keep on biting. Sea stars are quite resilient. Cost me a pair of gloves. Could be quite interesting when they get to inhabit the wreck alongside, when a diver goes inside. This was nowhere exotic, and only 140ft: a certain popular wreck in Scapa Flow (only one wreck at 140ft in Scapa). Odd response: the giant octopus off British Colombia hate neoprene - when you want them to go away, just peel back a seal, touch them and off they go. Wonder where the sea stars got a taste for neoprene and rubber? Also, where they learnt to move so fast? How do they talk to each other? Alex NB: Just to be clear, the stars did not cause me a flood, but quite a few holes. Touch them with a hose, and I am sure it would leak quite fast.
(Offline)

6th October 2005, 04:04	#14 (permalink)
silent running Mature mouth breather Current Rebreather/s: Prism Topaz Other Rebreather/s: Join Date: Jun 2005 Location: U.S.A. Brooklyn, New York Posts: 1,881	Hello Mike, here's my flood list: -Flooded Dolphin scrubber resulting from false positive mf'n p-connector. Happened in the first 10 minutes of a shallow night dive. Aborted and stayed in heads up position on the gurgling loop. No cocktail -Flooded exhale CL on Prism. Old style fitting at top of bag came loose. No water made it to the scrubber. Didn't even know I had 3 cups of water in the bottom of the lung until the end of a 3hr dive and still breathed great. Could have blown it out of the drains, but by then it didn't seem worth the bother. -Small leak on Prism scrubber seals discovered on descent. Water stayed on the bottom of the scrubber under the canister. Aborted dive, stayed on the loop. Replaced pinched O ring got back in water. As you can see, all mine were minor and only the Dolphin would have turned into a total flood if I had not caught it. Reading the other posts, it seems a true total loop flood is very rare. Still, I think it's essential to be able to drain the loop as it seems most floods are the kind you could recover from, where drains are useful. I think the biggest threat of TLF would be from hoses being cut by obstacles, which is why I plan to get some of those niffty nomex hoses for the head-CL part of the loop. I guess another would be the mouth pc slipping out due to an O2 hit. With this in mind, I tried the Manta Bite on my Prism this last trip. The rebreather size fit the DSV very well, but the wings of the thing really push out against your cheeks, which is not comfortable and feels similar to having the dreaded chipmonk cheeks. Could not get used to it. Hey what happened to your pre-pubescent, slack jawed girl avatar? I couldn't stop laughing everytime I saw it. Bring her back!-Andy
(Offline)

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