O2 for suit inflation on deep Rebreather cave dives

Drmike

I know he used O2 for wing inflation - not sure if he did for suit too

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Cave diving is a sport
Wreck diving is a sport
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silent running

Are there any instances of O2 igniting from static electricity at normal surface pressure? Are blankets forbidden with patients using O2?

Marc T

Why not a "middle way" by using a NX 40 for usual drysuit inflation AND as an emergency solution to feed your solenoïd?

Mdemon

I think you'd find the massive increase in buoyancy needed to raise the PO2 would be difficult if not impossible. It would also add lots of nitrogen to the loop which might not be what you wanted!

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Drmike

Why would you carry a NX40 on a deep cave dive when you cant breathe it??

It would be better staged

__________________
Cave diving is a sport
Wreck diving is a sport
Diving in general is a sport

'Rebreather diving' is not a sport
its the delusional obsession with a highly dangerous and often inappropriate piece of equipment

Marc T

I think there is some computation to do (also on the dilent choice ) but it could be a way in depth part of a dive where the increased volume is not so high, the dil choice had to be done including the idea you perhaps had to increase the N2 content.
Later you can go back on staged O2 and air tanks on shallow part, but many work and though for few thing I agree.

johnv

adding my 2p worth, I would not be brave enough to put O2 in my suit at 15 bar, if (and only if) there was a problem then it is going to hurt. I also tend to wear a heated jacket for deep dives which makes the problem worse.

The other way to go is to put tri-mix in your suit (go on flame me but read on first)

I have done this and got away with it when the number of cylinders is critical. This tends to be in one of 2 situations:

1. I inflate my suit with an air cylinder until I get to a restriction, then I dump the cylinder and switch to tri-mix for the suit until I get back through the restriction, then flush out the mix.

2. on multi sump caves where I don't want to carry more than one cylinder between sumps at the farthest points of the cave I'll use air whilst I can, then when I dump the air I'll use TX in the suit until I get back to the air cylinder where I'll flush the tx out.

I don't do this often but it works well for minimising gear when it's critical and it's great when you get to flush the TX out of your suit. Neither of these are done as a matter of course and require pre planning and care.

YMMV


John

Drmike

Our experience has been even just adding a few squirts of mix into a suit previously inflated with air caused minor skin bends when over 19bar ambient

__________________
Cave diving is a sport
Wreck diving is a sport
Diving in general is a sport

'Rebreather diving' is not a sport
its the delusional obsession with a highly dangerous and often inappropriate piece of equipment

Dutchy

Wouldn't recommend smoking during the dive either...
But seriously spontaneous combustion could be an real issue. High pPO2 and certain materials don't mix well. Especially considering the garments may contain dirt and grease from expore to something in the car o on the boat. A simple thing like static electricity is enough to ignite the thing. I've seen it with syntetic materials out of the diving context. What has saved divers so far I guess is high humidity in drysuits (from perspiration) which has a negative effect on building up static electricity prior to a discharge (sparc)...

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iain-hsm

There was a reported case Royal Navy of a CD in 1980 inadvertently used oxygen in his suit inflation bottle. Dry suit was a rubber Avon neck entry, bottle 0.4 L alu HP flow to dry suit via restrictor. Of critical importance was the nylon fleece undersuit “Wooly bear”. Problem on surface while smoking he eased open the latex neck seal and ignited the oxygen saturated fleece.

NFPA have disclosed of the 100 or so oxygen related fires in hospitals each year that around 10 are fatal due to oxygen saturation of coverings drapes clothing or ignition.

No hyperbaric air chamber will allow (or should allow) a percentage of oxygen greater that 23% regardless of depth. (monoplace oxygen chambers 3bar ATA are exception and have been the cause of 6 fatalities in last 10 years)

In our chambers we will not compress deeper with air than 80MSW with occupants due to the PP02 in air under pressure in the chamber for fear of static ignition. Although the occupants are breathing a separate mix via CCR or BIBS breathing system.
Also we would only pressure test with air to 90MSW over that with inert gas. In a full depth dry compression test say to 250 MSW we would compress to 90MSW on air then balance to 250MSW on N2 to full pressure.

My concerns mechanically would be (apart from the skin bend, electrical, chemical, and ignition source issues) the singular lack of oxygen inflation information at depths greater than 3bar ATA, the possibility of static build up in the undersuit and if a static discharge could be made possible due to sonic flow, impact ignition, through the inflator etc. The dark won’t make a difference however the increase in relative humidity will almost certainly reduce a dry fire ignition. In the chambers we use a fire deluge system in diving I suppose you have no problem in that area. I would suggest a self donning dry suit so in the event of a fire…..open zip.