How long do we have before we fizz up?

[JT2]

After having watched several military and commercial diving programs on TV, and noticing that it appears as if they do not deco in the water, but instead are brought to the surface and undressed in a hurry and rushed to the chamber. Unless I am missing something here, that means there must be a certain amount of time we have to start decompressing once we hit the surface before any harm is done, right? Any time I read a book or someone's account of a deadly dive they are always talking about the diver being in instant pain an agony as soon as they hit the surface, if this is truly the case, then how can the military and commercial divers do it and not be injured? I know there is probably something I am missing here, and I know this is the place for the answer. Thanks in advance.

 

[rmediver2002]

There are two types of surface decompression for normal diving operations, surface decompression with air and surface decompression with oxygen.

I forgot to mention when I first posted this that Sur D O2 is the standard now and Sur D air is not used very much...

Depending on the depth and duration of the dive the diver may be obligated to perform some in water stops prior to reaching the surface.

If no in water stops are required then the diver will have a total of :05 minutes to get to depth (40' for sur D O2) in the chamber.

The time starts when the diver reaches 30 FSW in the water column so you burn about a minute on the ascent to the surface. The pressurizing the chamber will take another :30 minimum time (80 feet per minute decent rate is pretty fast, if time is available you go slower) So the answer to your question is the diver has about :03::30 three minute and thirty seconds on the surface to get undressed.

If the diver developes any symptoms at all during this time or for some reason you spend to much time on one phase and miss your :05 total time to get back under pressure you will be doing a treatment table instead of surface decompression. (TT-5 if the diver has no symptoms and TT-6 if they develope any symptom at all) this will take from 2.5 to 6 hours to complete.

This is the type of diving that was used on the salvage of the TWA flight 800, the monitor, and the Ehime Maru


Saturation diving is when the diver is compressed to a depth range he will be working at for an extended period of time usually, Days or weeks. The diver is transported to and from the worksite in a pressurized diving bell and then back to the chamber on the surface vessel...



Hope this helps some...

Jeff Lane

 

[AquaTec]

the reason they are in pain is bacause they have already started to bubble, generaly because they spent some time in deco so it slowed their time to the surface.

Military divers do not spend that time, the ascend directly to the surface and then enter the chamber.

ya got about 5 minutes

If you bubble then they get the next guy in line and try it in 4 minutes.

I think 5 minutes is the theory though

 

[JT2]

Thanks guys, thats kind of what I figured. I guess thats why they always look like they are doing a pit stop when they start undressing the divers huh?

 

[Dr Deco]

Dear JT2:

Surface Decompression

It brings a look of surprise to many to learn that commercial and military divers exit the water with considerable gas dissolved in their bodies and do not immediately get DCS. The process is referred to as “surface decompression” by divers and “decanting” by compressed air workers. What is done is to come to the surface in a diving bell (for divers) or in an air lock (compressed air workers), and then quickly go to another (usually more spacious) lock on the surface within five minutes. The rational for this is to get the divers out of the water as rapidly as possible and move them into a safer environment.

Quickly

It is obvious that the divers are very saturated with dissolved nitrogen when at a pressure of one atmosphere on the surface. For this reason, they must be repressurized with oxygen quickly; regulations state that this must be within five minutes. This has been found to be a reasonable time frame. Clearly, decompression sickness is not brought on within seconds. There are rules that govern the depth from which you can surface, and generally this is forty feet. When you hear about the divers in The Last Dive experiencing such grisly problems, it was because they came up from 200 feet.

Nuclei and Bubble Growth

We see in this procedure a definite demonstration that being supersaturated does not cause DCS. There are also question of micronuclei and the growth of these nuclei by inward diffusion of nitrogen. This growth process requires time, and that short duration for growth can be utilized to repressurized the divers in a deck decompression chamber. As the time before repress is extended, the situation can rapidly turn into a disaster.:boom:

US Navy Procedure

The US Navy will repressurize the diver to a depth somewhat below that from which the diver surfaced. They will then breathe oxygen at this pressure and finally depressurize to the surface.

Dr Deco :doctor:

 

[JT2]

Excellent information as always, Thanks!

 

[SPEEDSTER]

There are rules that govern the depth from which you can surface, and generally this is forty feet.

What do they do if the dive was deeper than 40'?

 

[Dr Deco]

It is sometimes necessary to perform some decompression in the water to get to 40 feet. If the times are too long, then some type of diving bell must be employed. The bell can then be mated to the DDC (= deck decompression chamber).

Dr Deco:doctor:

 

[SPEEDSTER]

So what about what aquatec said:

the reason they are in pain is bacause they have already started to bubble, generaly because they spent some time in deco so it slowed their time to the surface.

? Is this not completely accurate, or do they employ the bells exclusively below 40 feet?

mike

 

[Dr Deco]

Dear SPEEDSTER:

Surface Decompression

The divers involved in the SurD O2 as it is called, will have sufficient decompression to allow them to rise quickly to he surface and be repressurized (within the five minutes time frame). This is contrary to the Haldane hypothesis that indicates that when supersaturation is exceeded to a certain degree, DCS in quickly ensue. Clearly this does not occur and it one reason why people began to doubt the Haldane theory several decades ago.

The other divers

There is a considerable difference between (a) performing some decompression underwater and then completing you remaining deco in a decompression chamber and (b) missing a whole bunch of decompression on the surface and not doing much about it. That is why the later divers are in very bad straights with either pain or loss of consciousness. One is a controlled situation and the other is complete chaos.

Dr Deco :doctor: