Rebreather flood.

[Kim]

Does anyone know how much weight swing (positive/neutral to negative), a Classic Inspiration RB would change if it flooded?

 

[L.A.Dave]

You have to figure out the gas volume of the loop, and then figure out the weight of an equivalent amount of water.

My guess is 10-15lbs.

 

[Diver0001]

I don't have any direct experience with rebreathers but when I asked this very question to a friend of mine who does he replied "tonne of bricks"

R..

 

[H2Andy]

whatever the change, if flooded, it would be almost impossible to keep at
the surface

the last incident in Europe illustrates this. the victim apparently could not undo his
light strap, and was dragged down by the unit.

 

[Halthron]

I've been told that loop volume on a classic Inspo is either 11.5 liters or 14 l depending. Assuming that's correct, it would seem it would swing 21-26 lbs. if completely flooded.

 

[Kim]

I've been told that loop volume on a classic Inspo is either 11.5 liters or 14 l depending. Assuming that's correct, it would seem it would swing 21-26 lbs. if completely flooded.

I believe that that is only the counterlung volume. It does't take into account the hoses and the scrubber volume AFAIK. Could be wrong though.

 

[caveseeker7]

I believe that that is only the counterlung volume. It does't take into account the hoses and the scrubber volume AFAIK. Could be wrong though.

That's correct, the medium counterlungs are 5,7 ltr and the large ones 7 ltr each.
Small and extra large are available as special oreder and their volume not given.
IIRC 'padiscubapro' has a formula to calculate the gas amount inside the scrubber.
He would also know the specific weight of gases which differs.
Leaves hoses, DSV, the tube on the scrubber, as well as the gas spaces below and
above (head) of the absorbant holder.

Diver0001's friend is probably pretty close. eyebrow

Andy, remember that in that Inspo fatality they used backplates and had cannisters
mounted to the harness, two rather negatively bouyant items that compounded
the problem.

 

[padiscubapro]

That's correct, the medium counterlungs are 5,7 ltr and the large ones 7 ltr each.
Small and extra large are available as special oreder and their volume not given.
IIRC 'padiscubapro' has a formula to calculate the gas amount inside the scrubber.
He would also know the specific weight of gases which differs.
Leaves hoses, DSV, the tube on the scrubber, as well as the gas spaces below and
above (head) of the absorbant holder.

Diver0001's friend is probably pretty close. eyebrow

Andy, remember that in that Inspo fatality they used backplates and had cannisters
mounted to the harness, two rather negatively bouyant items that compounded
the problem.

I looked for my measurements andc ouldn't find them all, what I did find was


approximate volume in cannister
(volume in 266.8390260143006) cu inch
approximate volume of area displayced by co2 cartridge
190.41002692894185 cu inc
approximate volume of inner of cartridge (sofnolime)
177.6345519075589 cu inc
1 inch pipe / 12 inches approx volume of exhale tube 9.424777960770001=0.1544444 liter


cannister base - outer dimensions of cart = 76.42899908535875 = 1.252446905 liter

approximate volume of base plus exhale tube less scrubber contents is about 1.4 liters

I cant find the measurements of the lid, but its not that significant most of it is filled with electronics and center tube.. my guess would be around .5l

I couldn't locate the hose,dsv and t piece numbers but a reasonable guess is between 1 and 2 liters of additional air space.

some most likely we have between 3 and 4l of dead space not including counterlungs
so my guestimate is between 6.8lbs (3l) to 9lbs (4l)


for 11 l MAXIMUM displacement (unlikely except on ascent) 24.9lbs (salt water)
for 14l Maximum 31.6lbs (salt water)

absolute worse case is ~40LBS!!!!

 

[Warren_L]

I believe that that is only the counterlung volume. It does't take into account the hoses and the scrubber volume AFAIK. Could be wrong though.

ONe thing to keep in mind is that you should not be basing this calculation on counterlung volume, but rather loop volume. When diving rebreathers in general, you want do dive with what we call minimum loop volume, which is essentially your lung volume (which is part of the loop), empty (or near empty during inhilation) counterlungs, and non-compressible air spaces (hoses, scubber canister, etc). So factoring full counterlung volume is not that really relevant.

Think of say an empty lift bag you might carry with you. At depth, if you fill it with water, will your buoyancy change? Same sort of thing.

 

[Halthron]

Yeah, I was given bad info it seems. Sorry about that, I did ask if it was total loop or just CL and was told loop.