Posted by MHK on October 31, 2000 at 13:30:43:
Given the Nitrox discussions going about I thought I post this that I just received from Bruce.. Ken Kurtis I hope you read this because I want your reaction to Bruce's comment that NAUI is moving to make ALL classes Nitrox based... I also look at NAUI's stats as compared to D.A.N.'s..
>=
>
>
> NAUI Nitrox And Technical Diving Statistics
>
> B.R. Wienke, T.R. O'Leary, J.D. Livingstone
> NAUI Technical Diving Operations
> Tampa, Florida 33619
>
>
> NAUI began training and certifying nitrox divers/instructors in 1992.
> In 1998, NAUI Technical Diving Operations formed to establish standards
> and procedures for recreational and technical nitrox diving, as well as
> mixed gases such as heliox, trimix, helitrox, and to formally certify
> divers/instructors in recreational, extended range, decompression, and
> mixed gas diving activities. Across programs, maximum oxygen partial
> pressure, pO2, is 1.4 atm, except at decompression stages where 1.6 atm
> is permitted. NAUI has traditionally employed an EAD approach to nitrox
> tables, but will be switching to phase RGBM tables soon, to smoothly
> transition recreational and decompression nitrox diving. For trimix,
> heliox, and helitrox, NAUI already uses, and has released, RGBM tables
> usually coupled to pure O2 at 20 fsw. Nitrox computers are an integral
> part of NAUI nitrox training, as necessary component of sensible dive
> planning, and diver staging. Diveware (ABYSS, Decoplanner, Proplanner,
> etc.) is also an integral part of mixed gas dive planning and profile
> assessment. NAUI encourages "nitrox add on" to all of its course
> curriculum by making an additional 2 nitrox dives beyond core
> requirements. Plans are also in the works to make all courses nitrox
> based, with air the usual (default or EAN21) case. NAUI uses a mixed
> gas blending and oxygen service procedure (Manual developed by NAUI
> Technical Diving Operations) in technical training activities.
> The Manual is also the basis of a gas blending course.
>
> To date, NAUI has trained 4412 recreational nitrox divers, 784
> technical nitrox (staged deco) divers, and 317 trimix (staged deco)
> divers without single incidence of DCI. Some 878 recreational nitrox
> instructors, 322 technical nitrox instructors, and 35 trimix instructors
> have similarly been certified without single training incidence of DCI.
> For all of these training dives, some 32,198 tanks have been filled
> with mixtures up to 100% oxygen without mishap. Just for
> recreational nitrox, the tank total for training is 17,604 fills.
> EAN32 and EAN36 are standard NAUI training mixtures. The yearly
> breakdown follows.
>
> Year Recreational Nitrox Tech Nitrox Tech Trimix
>
> 92-97 1552 divers
> 256 instructors
> 5664 fills
> 0 DCI
> 0 explosion
>
> 98 921 divers 213 divers 62 divers
> 214 instructors 99 instructors 5 instructors
> 3982 fills 2268 fills 1120 fills
> O DCI 0 DCI 0 DCI
> 0 explosion 0 explosion 0 explosion
>
> 99 969 divers 267 divers 120 divers
> 240 instructors 122 instructors 19 instructors
> 4338 fills 2832 fills 3100 fills
> 0 DCI 0 DCI 0 DCI
> 0 explosion 0 explosion 0 explosion
>
> 00 970 divers 304 divers 135 divers
> 165 instructors 101 instructors 11 instructors
> 3620 fills 2824 fills 2450 fills
> 0 DCI 0 DCI 0 DCI
> 0 explosion 0 explosion 0 explosion
>____________________________________________________________________
>
> 0 DCI/17604 dive 0 DCI/7924 dive 0 DCI/6670 dive
> 0 exp/17604 dive 0 exp/7924 dive 0 DCI/6670 dive
>
>
> NAUI Technical Diving Operations shows zero DCI and O2 mishaps. And
> aross all diving, NAUI statistics suggest a training DCI incidence rate
> below 1/100,000 for the past 10 years, no tank/regulator O2 explosions.
> These statistics are for NAUI training activities, only. NAUI has
officially adopted the RGBM for all recreational and technical dive
training, having already released trimix, helitrox, and high altitude
air (see next issue of Advanced Diver) tables. Nitrox and air RGBM tables
will shortly replace older Haldane based tables for recreational diving.
Over the past three years or so, a few 1000s of technical and rereational
RGBM dives have been logged without incidence of DCI.
> High Pressure Combustive Oxygen Flow Simulations
>
> B.R. Wienke
> Los Alamos National Laboratory
> Los Alamos, N.M. 875454
>
>
> Using 3D hydrodynamic codes with oxygen combustion chemistry imbedded,
> we have simulated expolsion scenarios under high pressure pneumatic
> impacts. Mixed gas flows (variable oxygen fractions) down a stopped
> short tube were analyzed for variable volatile and non-volatile particle
> densities in the impact region. Drive pressures were varied from 50 psi
> up to 5000 psi, and particle densities ranged 5 mg/ft^2 to 300 mg/ft^2.
> Oxygen fractions ranged from .20 up to 1.00 (air to pure oxygen).
>
> The flow schemes are typical of impacted pneumatic gas hydrodynamics.
> At the stopped orifice, a slug of compressed gas is heated by both
> shock formation and inertial implosion (both compressive and
> non-adiabatic). The dust was assumed to be metal, plastic, glass,
> and grit, with particle sizes in the 25 micron to 100 micron range.
> Combinations of plastic and metals (aluminum, titanium) are combustive.
> Reaction oxygen chemistry is assigned to the dust, and rapid heat
> conduction from the slug ignites assembly constituents when
> approprate. Obviously, the process is very complicated, but some
> simple results are suggested by simulations.
>
> For drive pressures in the 3000 psi and above range, and across
> all dust densities supporting combustion, oxygen mixtures below
> 70% (oxygen content) did not ignite in these simple simulations.
> Above 70%, impurity densities in 200 mg/ft^2 were requisite to
> support combustion in the 3000 psi range. Below 3000 psi, ignition
> was only sustained with high oxygen fractions (90%).
>
> Results will be published.
>