JFD Divex SLS Mk IV, Operation And Maintenance Manual

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2 OM131
Chapter 1 P1939-OM-131 R11
1.1 P
URPOSE OF EQUIPMENT
The Secondary Life Support (SLS) System is an emergency breathing apparatus designed for use
by professional saturation divers, operating from a diving bell. It is intended for use in the event of a
fundamental failure of a diver’s primary life support system (e.g. loss of primary breathing gas, loss
of hot water, etc). The System operates using semi-closed circuit breathing apparatus principles and
provides complete independence from the diver’s primary systems. The SLS System meets the
Norwegian Petroleum Directorate (NPD) Regulations 1995, Section 38, which requires that whilst
breathing at a rate of 62.5 lpm (litres per minute) RMV (respiratory minute volume), the diver should
be provided with a minimum of 10 minutes of breathing gas in order to return to the safety of the
diving bell.
1.2 G
ENERAL DESCRIPTION
The SLS System comprises a Backpack (Fig 1.1, Item 1) and a Helmet (Fig 1.1, Item 2). The
operational principle of the System is basically that of a conventional semi-closed circuit breathing
apparatus, in which exhaled gas is captured in the counterlungs and is then re-breathed by the
wearer, after removal of the carbon dioxide (CO
2
) and replacement of the oxygen.
The SLS System layout is shown in Fig 1.2 with the Helmet (See separate Manual Ref: OM112) in
plan view. The Backpack consists of a main housing containing a gas injection system, a CO
2
scrubber canister and a thermal regenerator. The main harness also contains the system
counterlungs.
The gas injection system has three (3) heliox cylinders manifolded together with a charging point,
burst disc, two stage regulator, injection orifice, single stage regulator, demand regulator and a
overpressure indicator.
The CO
2
scrubber canister provides a chemical absorbent bed for the removal of the carbon
dioxide. A thermal regenerator temporarily stores the heat within the breathing gas in order to avoid
losing it to the water as the breathing gas passes into flexible bags (the counterlungs). The SLS
Backpack harness has the counterlungs fitted to its shoulder straps.
The mixture of breathing gas required depends on diving depth, and complete details are given in
the operating information within the 'Preparation for Use' procedures (section 3.1.1).
During normal diving operations the SLS System is worn in stand-by mode with the mouthpiece
retracted into the helmet interface assembly. The counterlungs are mounted on each of the diver’s
shoulders and are stored packed in strong fabric enclosures to protect them from damage.
Two actions are required to activate the SLS System:
1. The interface valve on the right hand side of the Helmet has to be rotated through 180
o
, to
push the mouthpiece into the oral / nasal where the diver can bite onto it.
2. An actuation handle on the harness has to be pulled to deploy the counterlungs and pull a
spool valve which switches on the gas bleed for make-up gas.
N
OTE
If the actuation handle is not pulled the diver will run out of breathing gas as the system has now
become open circuit.