Dräger LAR 8000

Instructions for use | LAR 8000 41
Description | en
3.2.3 Mixed gas operation mode feature description
In mixed gas operation, the diver can switch the rebreather from mixed gas to
oxygen operation or vice versa using the rotary switch of the switch device during
use. For this purpose, the rebreather is equipped with a compressed gas cylinder
for oxygen, which is mounted directly underneath the rebreather, as well as a
mixed-gas cylinder with pressure reducer and pressure gauge, which is connected
via the external supply line. The mixed-gas cylinder is carried on the back of the
diver, for example.
In mixed gas operation mode, the rebreather works with a semi-closed breathing
circuit. The dosage of the respiratory gas is constant over time and independent of
the diving depth. Dosage for the mixed gas is switched on by connecting the Nitrox
supply and setting the rotary knob to mixed gas operating mode. In case of an
increased gas demand, the breathing circuit is filled via a lung demand bypass
valve. The carbon dioxide (CO
2) exhaled by the diver is absorbed in the soda lime
of the CO
2 absorber.
Due to the semi-closed circuit principle and the thus permanently set fresh gas
dosages, the O
2 content in the breathing circuit is almost always lower than the O2
content in the added fresh gas. The reduction of the O
2 content in the breathing
circuit is proportional to the O
2 consumption and thus to the physical exertion of the
diver.
The higher the diver's physical exertion, the lower the O
2 content he or she inhales.
During low physical exertion, the oxygen content of the breathing gas in the
breathing bag approaches that of the gas supply in the mixed-gas cylinder.
It is therefore important to always calculate the maximum possible diving depth with
the oxygen content in the mixed-gas cylinder.
When proceeding as described, a certain safety margin is always included at the
maximum possible diving depth as well as at the decompression levels and
decompression depths.
3.2.4 Mixed gas operation functional diagram
The supply of mixed gas is possible if the mixed-gas cylinder is connected to the
rebreather via the pressure reducer.
45285
O 2
NX
Cylinder valve
Cylinder valve
Pressure reducer
Pressure reducer
NX coupling
NX switch
LDV
Dosage
Non-return valve
Breathing
circuit
Pressure gauge O
2
Pressure gauge NX