Miners and DCS

[kwesler]

Why didn't all the miners that were rescued get bent? I understand they were at the equivalent of 40 fsw for 77 hours! One has some minor (no pun intended) shoulder pain but that is it.

Granted they were virtually immobile, but they were also cold.

I understand they pumped 100% O2 to them (I assume the lack of an airtight environment prevented them breathing true 100% and toxing)

Thoughts...?

Ken

 

[srkdvr]

They were not on compressed air. The rescue team drilled a whole for a six inch pipe for them to get air from... so the were breathing just as you and I are right now.

Rich :mean:

 

[JimC]

Dousn't matter if the air is compressed or not. It matters what presure your body is under. There is enough nitrogen in one breath to bend you.

But, if they could breath air at atmospheric presure, then they must have been at the same, and not at the equivalent of 40fsw...

Not sure which one is right.

 

[kwesler]

They were at the equivalent pressue as 40 fsw...there was a Navy dive expert on site with hyperbaric chambers waiting for them. They were expected to be bent...

 

[kwesler]

Apparently, mines are pressurized to assist in the mining effort somehow...maybe that is why they were supposedly under that much pressure. It is hard to tell from the media how much info is concrete and how much is supposition.

Ken

 

[The Iceni]

Originally posted by srkdvr
They were not on compressed air. The rescue team drilled a whole for a six inch pipe for them to get air from... so the were breathing just as you and I are right now.

Rich :mean:

I am not so sure.

Although we have not been given as much information this side of the Atlantic it looks, to me, as though they were in a flooded section, which means that they had to be in a pressurised "capsule" in order to stop the ingress of water; - A typical caisson arrangement in which the gas had to be pumped down to them. (Sufficient quantities could not have got 240 feet down to them by simple diffussion.)

If this was the case and they were breathing 100% oxygen at the equivalent of 40 feet it would have had a partial pressure of 2.2 bar. Since their breathing medium would have contained little or no nitrogen there would have been very, very little inert gas to absorb to cause DCI. I suppose the rescuers considered the risks of a theoretical CNS hit were justified.

All in all, I have to say the rescue appeared to be VERY professional indeed.

I was suitably impressed.

 

[JimC]

Originally posted by kwesler
They were at the equivalent pressue as 40 fsw...there was a Navy dive expert on site with hyperbaric chambers waiting for them. They were expected to be bent...

If they were at "40 fsw" then the gas they were breathing would have had to be presurized. You can't inflate your lungs against much presure. Try takeing a 4 foot tube and breathing it 4 feet under water. Can't be done.

I think Dr Paul likely has the answer. But 100% O2 ~40 feet is begging for a toxic hit.

 

[Rockhound]

I was offshore over the weekend and missed most of the news, but I did catch a segment showing a rescued miner when I got back....I was also suprised that he seemed to have skipped a session in a decompression chamber.

I am a geologist/geophysicist, and before moving to the oil and gas side of things, I worked in coal.

MOST mines are not pressurized to a level that requires decompression. However, as some noted, once a mine floods, any trapped miners who find air pockets are now in a pressured caisson environment.

In addition, concerns over continued flooding (as the gas vents through fissures and pore spaces in the rock) requires that PRESSURIZED air be forced into air space. In fact, a slightly overpressured situation is probably desired, as it will drive any water out through any "U-tubes" (sumps) in the tunnels upstream of the break that is sourcing the water and reduce the water level.

The intention was to keep the guys under pressure, and that is why they had decompression chambers and hyperbaric stretchers available. Any release of pressure would have IMMEDIATELY flooded the chamber.

If you saw the tube they pulled out of the escape bore, that too, was designed to be pressurized.

(The amazing thing to me, however is the technology that allowed them to drill a 36" hole to 300' and yet, still retain a proper pressure seal. In drilling oil and gas wells, pressure is controlled by drilling fluids when necessary, but I have no idea how they did this without fluids....)


added......
Oops...I just talked to a co-worker who told me that one of the miners did get bent, but only slightly....but that doesn't explain why there weren't all chambered for a while as a precaution....unless pressure readings from the vent well showed significantly less than the 40-50' column of water that I heard they had faced.

 

[The Iceni]

Originally posted by Rockhound
I just talked to a co-worker who told me that one of the miners did get bent, but only slightly....but that doesn't explain why there weren't all chambered for a while as a precaution....unless pressure readings from the vent well showed significantly less than the 40-50' column of water that I heard they had faced.

That settles it for me. Thay cannot have been on 100% oxygen. With a diving expert on the surface I supect they were supplied with a suiatble Nitrox mix (Say 50%) in which case after 77 hours there could still be the need for some deco.

However, what about the risks of fire!

Impressed? You bet!

 

[srkdvr]

When I watched the report on Sunday, the man incharge was telling how they only had pockets of air they could put there nose into and that the water was up to there chin. They put the pipe down to them and then dug it out and pumped the water out. Everything I have been taught and heard since I have been diving was unless you breath compressed air you do not risk DCS. And a few months back on this board someone posted a question as to why whales don't get DCS because of the depths they go and the same answer was given by several others.

But then again it could all be because God took these men and protected them from DCS.

Rich :mean: