JFD Divex SLS Mk IV, Operation And Maintenance Manual

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OM131 5
P1939-OM-131 R11 Chapter 1
1.3 P
ERFORMANCE AND
L
IMITATIONS
The SLS System has been proven in extensive unmanned and manned testing. A selection of
unmanned test data is presented below.
1.3.1 Work of breathing
Fig 1.3 shows the work of breathing in Joules per Litre as a function of breathing rate in lpm RMV at
a depth of 400 msw using heliox gas. The W.O.B. performance is even better at shallower depths.
The dashed line indicates the maximum W.O.B. permitted within the HSE/NPD Guidelines at >180
msw, the dotted line showing W.O.B. maximum <180 msw.
Fig 1.3 Work of breathing
1.3.2 Oxygen partial pressure / endurance
The duration of the bailout which the SLS System provides depends on one of two factors; the time
taken to fully deplete its stored gas or the life of the CO
2
scrubber canister. The oxygen partial
pressure within the System will vary depending on diver breathing rate. This is illustrated in Fig 1.4
to Fig 1.12 for depths from 50 msw to 500 msw. The System’s cylinder duration can also be seen
from these graphs but it should be noted that at shallow depths duration is limited by the life of the
CO
2
scrubber canister.
With the diver at rest, the oxygen partial pressure rises from its initial value (corresponding to the
umbilical gas) towards 2 bar (pp) At increasing workloads, the oxygen partial pressure is lower, but
at no time falls below 0.2 bar. The System injects gas until such time as the cylinders become
depleted. Following this, the diver will progressively breathe down the oxygen content in the
System. However, it should be noted that the gas remains breathable for some considerable time
beyond exhaustion of the stored gas.