CHAPTER 10 — Nitrogen-Oxygen Diving Operations
Change A 10-9
normally burn in air may burn at these higher O2 levels. Normally combustible
materials require less energy to ignite and will burn faster. The energy required for
ignition can come from different sources, for example adiabatic compression or
particle impact/spark. Another concern is that if improper cleaning agents or
processes are used, the agents themselves can become fire or toxic hazards. It is
therefore important to adhere to MIL-STD-1330 to reduce the risk of damage or
loss of equipment and injury or death of personnel.
10-10
BREATHING GAS PURITY
It is essential that all gases used in producing a NITROX mixture meet the
breathing gas purity standards for oxygen (Table 4-3) and nitrogen (Table 4-5). If
air is to be used to produce a mixture, it must be compressed using an oil free
NITROX approved compressor or meet the purity requirements of oil free air
(Table 10-2). Prior to diving, all NITROX gases shall be analyzed using an ANU
approved O2 analyzer accurate to within ± 0.5 percent.
10-11
NITROX MIXING
NITROX mixing can be accomplished by a variety of techniques to produce a
final predetermined nitrogen-oxygen mixture. The techniques for mixing
NITROX are listed as follows:
1.
Continuous Flow Mixing. There are two techniques for continuous flow
mixing:
a.
Mix-maker. A mix-maker uses a precalibrated mixing system that pro-
portions the amount of each gas in the mixture as it is delivered to a
common mixing chamber. A mix-maker performs a series of functions
that ensures accurate mixtures. The gases are regulated to the same
temperature and pressure before they are sent through precision meter-
ing valves. The valves are precalibrated to provide the desired mixing
pressure. The final mixture can be provided directly to the divers or be
compressed using an oil-free compressor into storage banks.
b. Oxygen Induction. Oxygen induction uses a system where low pressure
oxygen is delivered to the intake header of an oil-free compressor,
where it is mixed with the air being drawn into the compressor. Oxygen
flow is adjusted and the compressor output is monitored for oxygen
content. When the desired NITROX mixture is attained the gas is
diverted to the storage banks for diver use while being continually
monitored for oxygen content (Figure 10-3).
2.
Mixing by Partial Pressure. Partial pressure mixing techniques are similar to
those used in helium-oxygen mixed gas diving and are discussed in Chapter
16.
