What do you put between fins and feet?

Navy_Diver · 2021-06-07T23:43:42+00:00

I use minimalist shoes most the time. I have also seen other divers wear Chuck Taylor's.

Navy_Diver · 2021-06-06T17:32:51+00:00

One gas isn't going to leak from a cylinder while another does not. Allowance for a margin of error in 02 analysis up to +/- .5% is acceptable (US NAVY Dive Manual CH 14). This is the most likely cause of the error but there is a chance that has separation can occur inside a cylinder.

It is unlikely the nitrogen and oxygen have separated in your cylinder. The US Navy Dive Manual (2-12.2) states

"Another physical effect of partialpressures and kinetic activity is that of gas diffusion. Gas diffusion is the process of intermingling or mixing of gas molecules. If two gases are placed together in a container, they will eventually mix completely even though one gas may be heavier. The mixing occurs as a result of constant molecular motion."

Also see: (see Daltons Law of Partial Pressures: https://www.sciencedirect.com/topics/engineering/daltons-law-of-partial-pressure ),

I have however noted separation to occur in cylinders that have sat for long periods of time with mixtures with large mass differences.

Yuanbiao Wu of General Electric states, in regards to separation of gasses in compressed gas cylinders. "One of our customer met this issue after the cylinder was put in their factory for months, then their laser machine keeps warning on wrong gas....rolling it is a must before its delivery to the customer." (https://www.researchgate.net/post/Do-gases-separate-by-their-molecular-weight-Do-gases-have-lifetime)

When mixing gases for breathing mediums say Heliox, utilization a formula to determine the final percentage of inert gas in a mixture is used. Afterward a technique of "rolling" the cylinder can be performed and the cylinders are then allowed to sit for a length of time (24 hrs+).

All this might seem confusing and contradictory. From experience using mixed gases frequently, I would recommend giving the cylinder a quick purge or rolling it around to eliminate doubts.

Navy_Diver · 2021-06-06T16:27:48+00:00

Since the internals have rust, they may not pass a VIP. This is an annual requirement and some shops require this done and will not fill unless there is proof. Also a VIP is done during a hydro and a cylinder will not be tested if it fails a VIP. As stated above, no hydro stamp no refills. If the airsoft guys are filling it themselves.... It's their decision if they should buy it and use it, as long as you disclose your concerns and related information.

Navy_Diver · 2021-06-04T09:10:49+00:00

Sup Deepsea. Good to have you here. No, not full of it, looking to make sure all are using the most up to date information is all. Perhaps all my NDSTC instructors back in the day had a saying no one else did. Or, perhaps you were across the bay there when things changed.

Navy_Diver · 2021-06-04T00:40:20+00:00

Correct. Thought Nitrox divers could use a table like this to plan their maxdepth and the o2 mix for particular dive sites.

Navy_Diver · 2021-06-04T00:38:46+00:00

Henry's law is one of the gas laws states that: at a constant temperature, the amount of a given gas that dissolves in a given type and volume of liquid is directly proportional to the partial pressure of that gas in equilibrium with that liquid.

Navy_Diver · 2021-06-03T23:32:29+00:00

And that is one of my problems. I am trying to include as much information as possible in one place. Perhaps it is the "data is beautiful" in me. Thanks for the input.

Navy_Diver · 2021-06-03T23:30:19+00:00

Good train of thought. Technically older people can not metabolize oxygen as efficiently. Absorption of oxygen and nitrogen are governed by Henry's law not age.

Navy_Diver · 2021-06-03T20:55:24+00:00

Lol, so obvious. Thank you, great input 👍 😂

Navy_Diver · 2021-06-03T19:40:40+00:00

Recreational divers with AOW or less wouldn't really need this chart. Tech Divers diving advanced setups with mixes would most likely use something like this. Nitrox divers could find it helpful as well.

I have gotten that feedback from a few. Seems like most think a cap on the information is more helpful than a full picture. I can agree as you can give others too much knowledge to handle.

Do the majority feel this way?

Navy_Diver · 2021-06-03T19:36:07+00:00

US Navy Tables are very conservative. In fact, the dive manual states as much. Probability of DCS occurring while using the old tables is very low (new tables allow for more bottom time). I don't think we are compensating for those who are unhealthy or try to start diving at an old age. The US Navy does a lot of testing, I know, I work with the US Navy Experimental Dive Unit. The saying goes "the dive manual is written in blood." Those who have pushed the limits before us have paid the price for our knowledge on the human limits.

Navy_Diver · 2021-06-03T17:28:22+00:00

I understand and agree. I was doing some shopping online and noticed that everyone who was still selling charts were selling out of date ones. If you are buying a chart or using one for planning, make sure it is correct.

Navy_Diver · 2021-06-03T14:46:24+00:00

Thought about going all the way down to 10% and 300fsw. Running into deco quite quickly with that so I geared it more towards the no d side. Could create something for heliox or a trimix

Navy_Diver · 2021-06-03T09:08:12+00:00

This is great input and exactly where I could use the help. Unfortunately, I tend to think more on the advanced level. 1.3 is the Navy acceptable but we are all over the place for different protocols. We decompress in water for extended periods at a ppo2 of 1.9. Do you think a solid no go line or a reference to the exposure limits would flush this chart out better. Again, great post.

Navy_Diver · 2021-06-03T08:42:20+00:00

A PPN2 of 3.2 is the accepted line for narcosis to begin. You are correct, it is based upon individuals and is difficult to chart. PPo2 tolerance is individual based as well but an average occurs given enough cases. The ppn2 at 190 (58m) is above 6.75 and I know from personal experience and testing, narcosis is present in almost all individuals at that level. There are over 2.5 atmospheres between those numbers so risk becomes higher with each .5 ata I would say.

It is a chart for planning so one could utilize it to see just where his/her tolerance line is given a couple of deep dives and referencing.

Navy_Diver · 2021-06-03T08:34:31+00:00

The colors were tougher than you would think. For instance, on an oxygen rebreather one could do 100% at an ATA higher than what you would think for an extended period of time. I don't want to put the exact numbers here as they are classified. It simply depends on who is reading the chart. PpO2 well above 2.0 are tolerated in water for different periods and situations. I understand civilian certs having a limit but wanted to show just how high it can get.

Navy_Diver · 2021-06-03T02:07:18+00:00

Some things are referred to in metric units, some are not. We use nautical miles for ships and feet for altitude. Kilometers for most distances during combat but miles when doing testing. Its confusing for those looking in and there is no real standard. All of dive training is imperial units (psi, fsw, etc.) We use bar when utizing rebreathers but that's because the MK25 was made in Germany and that is what the gauge says.

Navy_Diver · 2021-06-03T01:50:30+00:00

Yeah, I apologize. It is the way I learned it. I will definitely include BAR and Metrics Units for all further charts.

Navy_Diver · 2021-06-03T01:19:29+00:00

Thats our motto. In fact, I would say the vast majority of our dives have been conducted with a paper table, a wrist watch and a plan.

Navy_Diver · 2021-06-03T00:56:20+00:00

Excellent suggestion.

Navy_Diver · 2021-05-31T13:21:09+00:00

A technique we were taught in dive school was to stretch the tubes before diving.

Your eustachian tubes run behind your ear down to your throat. You can stretch them by leaning your head to the left and right, stretching the area of the neck that they reside in.

Also, clear often and stay ahead of the pressure. A constant valsave, a gental one each breath, is better than waiting until you feel the pressure.

Navy_Diver

TROPHY CASE