Raising the Monitor - Deco question

[bwerb]

I'm watching the National Geographic show on raising the turret from the Monitor. They show Navy divers using triox coming to the surface from 230 feet then rushing "within 4 minutes" to a decompression chamber. What's up with this? Do they do any underwater deco or is it all just done in the chamber

I wasn't shown how to do this in my PADI OW

 

[Aviatrr]

Navy dives often run abbreviated deco schedules in the water, and then surface and immediately get into a recompression chamber to "finish" their deco. They do, of course, have a very limited time to get into the chamber before bubbles start forming and causing problems. They run some pretty aggressive profiles in the chamber, too.....with deco on 100% Oxygen beginning at 50fsw(for a PPO2 of 2.5!). A friend of mine that used to do such diving said that CNS toxicity was not uncommon in the chamber.

Mike

 

[usil]

the surO2 (surface decompression on oxygen) provides for a much more thorough decompresion. It is also safer for the divers due to a controlled environment where if a problem arrises then a medic can be "pressed" down to help the diver.

 

[aue-mike]

they do some deco inwater and the remainder is done in the chamber under a controlled environment. Since they have hats on, are tethered, and with comms, they up the PO2s considerably. Toxing is not an issue of concern for them really since they won't drown. They started using 50/50 on those Monitor dives, though they start it at 90fsw. They go on 100% just prior to being pulled aboard. They then have five minutes to be stripped down and then walked to the chamber. They don't do any exertion to limit bubble formation. They are actually more or less carried to the chamber for the remainder of their decompression. The five minutes is based on the perceived safe window before bubble formation. However, I don't think I would subject myself to that abuse. There is some level of bubbling going on, and over time that catches up to you.
During one phase in 2000 they had a couple Type II hits and supposedly "numerous" unreported Type I hits.

 

[usil]

aue-mike

I have never heard of any commercial diving company using 100 inwater when there is a chamber ? Where did you aquire this information? I am very interested

 

[WreckWriter]

He was there. Mike was involved in the Monitor project.

WW

 

[rmediver2002]

During one phase in 2000 they had a couple Type II hits and supposedly "numerous" unreported Type I hits

Hits on TWA also, the only difference between surface decompression using O2 (if no symptom and you make your time) and having a hit or symptom is time in the chamber. It is not at all uncommon to encounter cases of DCS when your doing many decompression dives over the course of a project. That is why a chamber is required on site.

When your working on a project like this and you have a chamber on site you would be a fool not to report a hit. There is no reason not to...

"within 4 minutes"

The time starts from 30 Feet Sea Water 01 one minute from 30 FSW to the surface) then 3:30 on the surface to undress the diver and get him into the chamber, then a max decent rate of 80 feet per minute to 40 FSW in the chamber :30 for a total time of :05 from 30 FSW to 40 FSW in the chamber.

 

[rmediver2002]

I have never heard of any commercial diving company using 100 inwater when there is a chamber

On mixed gas dives the procedure is to switch to 100% O2 at 40 FSW

Jeff L

 

[aue-mike]

I am going by memory, but I believe the USN was initially using 100% upon entry with a stop at 40fsw to flush the hat with the helium-rich gas. Then, I am pretty sure they switched them to O2 at 40fsw on ascent. They did not do a switch and let them hang, just something to minimize bubble formation from 40-0fsw, until they could throw them in the can.
Many times we were put on standby when they were doing diver recovery and we watched them pull the guys up onto the barge. It was a real production. For those two divers you had about 15 guys on deck working in the immediate vicinity. That's a lot of support. Many times it seemed like it took quite a while for the stage to clear the water and get on deck, as they sometimes had to time it with the swells.
FWIW, I think I recall that each diver was using 500ft3 of bottom mix for a 20 minute excursion. Ouch, that's a lot of helium.

 

[usil]

never done any mixed gas bell runs but I thought that the hat was flooded with air, guess I'll have to take the corse, Second hand knowledge is a *****!!