2 Finnish divers dead, 3 injured in Plurdalen / Norway

[gianaameri]

Aren't the posted run times on the CIS based on using lithium hydroxide scrubber as well? Better hope the hydrophobic membrane works :O

On the CIS there are scrubber duration times quoted based on Sofnolime and Lithium Hydroxide.

With Lithium Hydroxide you get longer duration.

The problem is that the dive times quoted by the manufacturer of this now defunct rebreather which never took off and is irrelevant to this dive are not cross-referenced against temperature.

So to quote 6 - 10 hours on Lithium Hydroxide, but not quote at what temperature this is based is meaningless.

At 20C, sure I absolutely believe it. I have done it on Sofnolime with a Cis copy scrubber - shallow.

At 4C on lithium hydroxide, who knows. No clear test data available.

What is relevant here is not to talk about the Cis (a defunct unit), but the fact that no rebreather currently dived and available to the general public is suitable to a 129 meters planned dive at 4C temperature for 5 hours, hence it is not surprising what happened to these divers.

For those not familiar with rebreathers, scrubber duration and CO2 absorption is a function of temperature and depth (all other things being equal).

 

[Tigerman]

...
What is relevant here is not to talk about the Cis (a defunct unit), but the fact that no rebreather currently dived and available to the general public is suitable to 129 meters at 4C temperature for 5 hours, hence it is not surprising what happened to these divers.
...

Ummm... NO.

Whats relevant is what gear they actually used, how it was used and what their competence with it was.
What you can currently get from a shop is not neccesarily what people actually own and use.
If what is currently available in the shops sets the standard for whats in use, then nobody use windows XP..

 

[vincent54]

In no way am I saying they were diving the "defunct" rebreather, but it is an example of a unit that has gone deep, long and cold. The R model will last longer without even swapping the scrubber. Keep in mind the original designs were used in Antarctica waters. It is redundant and could handle the above dive plan. The team may have build up their own version. By the way, the units are still used and some even come up for sale. The battery is the only item that is difficult to find. I read Mr. Pile(sp) still dives his. So equipment for a dive like this is available to the "general" public, albeit at a price. Obviously it was a plan gone awry and the next try will end with better results.

Here is an example of deep cave with the mk5, http://www.usdct.org/wakulla2-technology-rebreathers.php They are saying 12 hour life support with their units.

 

[TONY CHANEY]

All around a very sad outcome. We may not know the exact gear that was used but we do know that diver 1 made the transverse to include the extra time spent trying to free Diver 2. We also have the following information, "Estimated time under water was five hours and deepest point at 129 metres (423 ft). Divers had gone through a bailout plan, i.e. a reserve gas plan if rebreathers were to fail during the dive. There were both spare rebreathers and also extra tanks for open circuit breathing."

 

[gianaameri]

In no way am I saying they were diving the "defunct" rebreather, but it is an example of a unit that has gone deep, long and cold. The R model will last longer without even swapping the scrubber. Keep in mind the original designs were used in Antarctica waters. It is redundant and could handle the above dive plan. The team may have build up their own version. By the way, the units are still used and some even come up for sale. The battery is the only item that is difficult to find. I read Mr. Pile(sp) still dives his. So equipment for a dive like this is available to the "general" public, albeit at a price. Obviously it was a plan gone awry and the next try will end with better results.

Here is an example of deep cave with the mk5, http://www.usdct.org/wakulla2-technology-rebreathers.php They are saying 12 hour life support with their units.

The temperature at Wakulla is 20C (so I read on the internet) - not the 4C of this dive.

At 20C the Meg 8 lbs. radial I believe will last as much as the Cis Radial: 6 - 12 hours.

At 4C we do not have data for the Cis Radial, but we have data for the Meg 8 lbs. Radial, and you don't get to 5 hours duration (and especially at 129 meters).

So, when you talk about scrubber duration you have to qualify the Time by the Water Temperature and by the Depth.

These divers - and the lesson to be learned here which is why I am typing on the keyboard as I feel it is important - is that they used equipment in all likelihood (hypothesis at this point, not fact) which was grossly unsuitable to the dive.

When we will know the make and model of the rebreathers and any mods. made, we can then look at more precise numbers - but because I am collating all these numbers I can tell you I do not know of any rebreather which these divers could have used which based on the available data was suitable for the dive which they did.

This is the spreadsheet which is work-in-progress and scrubber duration will be added when I have time:

http://www.rebreathermallorca.com/video/safety/ComparativeObjectiveWOBRebreatherDatabase.xlsx

WOB was also an important factor to consider on this dive insofar the effects of CO2 on the body are very much a function of WOB as well (so inadequate scrubber for the depth/temperature + poor WOB make the whole thing far more potentially dangerous).

It is relevant that the accident took place when the divers began to exert themselves more (greater WOB and greater CO2 production and possibly retention) to pass a restriction (i.e. equipment removal and physical effort).

 

[wedivebc]

As Gianaameri has stated and I agree. There is no rebreather now or ever that would be suitable for this dive. Scrubber performance is greatly affected by both temperature and depth and this dive is outside the tested parameters of any rebreather I am aware of.
Although the meg 8lb radial was tested by the US Navy under combat swimmer conditions for 12 hours that was in 72'F water. Performance in near freezing temps and 14ata depth would be greatly reduced. If the rebreather shown in the pic was used, that being a APD inspiration then I believe the scrubber is rated at 3 hrs.

 

[DevonDiver]

Link to the official report given by the Finnish Divers Federation on the double fatality in Plura.
It is based on the debrief given by the three divers who survived.

https://docs.google.com/file/d/0B-iDm0Pmt3MYU3hxb0tZS3llTGpWVnZ0RWlPeDY5NTJybFVF/view?pli=1&sle=true

 

[Thinkcat]

The names have been released:

The Norwegians have released the names. I could find no Finnish source for them.

 

[ianr33]

I can sure see why the scrubber design caused him to get stuck in a restriction. Makes complete sense.

Not.

 

[Subcooled]

In Finland ALL rebreather dives are done in +4 to +2 Celsius. Rebreathers are used for deep dives in cold water routinely. How deep... that I cannot tell as I am not a rebreather diver.

This dive had a deep part. It was not five hours at max depth. A lot of the planned time must have been deco time at shallow depth.