JFD Divex SLS Mk IV, Руководство по эксплуатации и обслуживанию

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OM131 19
P1939-OM-131 R11 Chapter 2
Fig 2.3 shows the principle components of the gas injection system. In operational mode, gas flows
from the cylinders (Fig 2.3, Item 1) to the two stage regulator (Fig 2.3, Item 3). The first stage of this
regulator reduces stored gas pressure to an interstage pressure of around 15 barg (217 psig). The
second stage reduces the pressure further to precisely 1 barg (14.5 psig). The gas is then supplied
into the SLS System via the injection orifice located within the lower penetrator. It then passes into
the breathing circuit at the bottom of the CO2 scrubber housing.
The spool valve between the first and second stages of the two stage regulator (Fig 2.3, Item 3) acts
as the gas injection shut-off valve, and is switched by the actuation cable release, which transfers
the SLS System into the operational mode.
A second feed from the H.P. manifold supplies gas to the demand regulator (Fig 2.3, Item 5) located
on top of the Backpack. This connection is tee’d at the regulator to provide a connection for the SLS
Systems H.P. contents gauge. This gauge provides the diver with a visual indication of the contents
of the HP cylinders.
In its stand-by mode the SLS System is kept at a positive pressure of 138 mbar (2 psi) by the single
stage regulator (Fig 2.3, Item 4). This is supplied with umbilical gas via a hose from a connection
from the Helmet side-block. This single stage regulator also supplies its gas to the SLS System
through the injection orifice.
Another connection, this time into the demand regulator body, is also provided to which the
overpressure indicator (Fig 2.3, Item 7) is connected. This indicator provides the diver with a visual
indication that everything is functioning correctly when the SLS System is in its stand-by mode.
2.3.1 Gas cylinders and manifold
SLS System enriched gas (heliox) is stored in three 1.18 litre cylinders, at 300 bar maximum
charging pressure. Each bottle is fitted internally with a sintered filter dip tube assembly. This is fitted
to prevent any internal corrosion within the cylinders from entering the pipework and potentially
blocking the gas flow. The three cylinders are connected together via a common manifold.
Incorporated within the manifold are connections for the cylinder charging point (Fig 2.3, Item 6) the
300 bar cylinder over-pressurisation protection burst disc and the supply line to the demand
regulator (Fig 2.3, Item 5).
2.3.2 Charging point / check valve
The cylinder charging point, 4 JIC, (Fig 2.3, Item 6) is installed in the left-hand cylinder fitting. This
has a built in check valve to allow easy filling and a sintered filter element to protect the check valve
seat from damage during charging.
2.3.3 Burst disc assembly
The burst disc is located on the inside face of the centre bottle fitting. This provides a safety valve in
the event of the gas cylinders being accidentally overcharged.
2.3.4 Two stage regulator
Fig 2.4 shows a cross-section through the two-stage regulator. Gas from the storage cylinders is
supplied via the banjo fitting (Fig 2.4, Item 9). This is retained by a circlip (Fig 2.4, Item 21) and
sealed by two O-rings (Fig 2.4, Item 27). The first stage piston (Fig 2.4, Item 4) provides regulation
of the interstage gas pressure to approximately 15 bar (217 psi). This piston is initially raised from its
seat by the spring (Fig 2.4, Item 20). Gas flows past the seat and then along the hole in centre of the
piston into the chamber to the left of the piston. The pressure in this chamber rises until it is
sufficient to overcome the force exerted by the spring. The piston then moves across to seal the
regulator port.