Manual Version 19 / 01-2019 II Page 7 of 44
SF2 ECCR OPERATION MANUAL
Chapter 1 - How the SF2 works
The SF2 belongs to the CCR rebreather category: Closed Circuit Rebreather This
describes a completely closed loop system in which only the metabolized oxygen
used (consumed) is added, this can be done manually (described as MCCR) or
electronically as with the SF2 ECCR.
The SF2 is an ECCR Electronic Closed Circuit Rebreather. The basic principle is
actually relatively simple and has been tried and tested for decades. The O2 content
in the breathing gas is measured via oxygen sensors - more on this later. If this
proportion falls below a pre-set value, oxygen flows into the system via an
electronically controlled solenoid valve (solenoid) until it again corresponds to the set
value.
What sounds simple in theory is influenced by various factors in practice, for
example increasing or decreasing pressure when descending or ascending.
In contrast to the open circuit system, the diver does not release any gas into the
environment when diving, so he breathes in a closed loop circuit which explains the
name. (If there is overpressure in the system, for example when surfacing, gas is
released into the environment even with a closed rebreather.)
Maintaining this circuit is important and must be checked before every dive. With the
SF2, the flutter valves, also called directional membranes, are located in the
mouthpiece. From the diver's point of view, i.e. with the device on his back, gas flows
from right to left.
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