BSAC Sports Diver Training and Breathing Gas Planning
Discover the essential strategies for safe diving with the BSAC Sports Diver Training and Breathing Gas Planning systems. Learn about gas reserve, equipment configurations, gas requirements, and cylinder sizing to ensure a successful dive. Proper planning is critical for a rewarding underwater experience.
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Presentation Transcript
BSAC Sports Diver Training Breathing Gas Planning & Systems
Sport Diver | ST5 Breathing Gas Planning & Systems Breathing Gas Planning & Systems Deeper, decompression stop or more challenging dives? Failure of gas supply - life- threatening!! ! Divers need sufficient gas to carry out planned dives ! Have a sufficient reserve for emergencies ! Carry an alternative gas supply Depending on the type of diving being undertaken ! Equipment configurations
Sport Diver | ST5 Breathing Gas Planning & Systems Sufficient Gas for the Dive Rule of Thirds ! One Third Gas supply for descent, to half way or turn around point. 1/3 ! One Third Gas supply for second half of dive or return including surfacing 1/3 1/3 ! One Third Gas supply for reserve How much gas is required for the Dive? What size cylinder is needed?
Sport Diver | ST5 Breathing Gas Planning & Systems Gas required for the Dive Amount of gas required depends on ! Personal breathing rate # Fitness # Energy output # Temperature # Nervousness # Safe Rule of Thumb - 25 litres/minute ! Depth of Dive # Use more gas at depth ! Duration of dive (minutes) Amount of gas =25 l/min x Abs. Pressure (bar) x Time (mins.)
Sport Diver | ST5 Breathing Gas Planning & Systems Cylinder Size for the Dive Cylinder capacity ! Size of cylinder in litres x bar pressure ! E.g. 10L cylinder at 230bar = 2300 litres air Dive to 20m for 20 mins. - 10L Cylinder OK? Breathing rate x absolute pressure x dive time (mins) 25 l/min x 3 bar (20m) x 20 mins = 1500 litres This represents two thirds (750 litres = 1/3) Reserve third (750 litres) needs to be added Total Air required = 2250 litres 10L Cylinder will be suitable for this dive = 750 litres
Sport Diver | ST5 Breathing Gas Planning & Systems Calculating Reserve Gas Dive to 20m for 20 mins Breathing rate x absolute pressure x dive time !25 l/min x 3 bar (20m) x 20 mins !This represents gas for dive (Two Thirds) !Add reserve third - 1500 x 1.5 = 1500 litres = 2250 litres Total !Reserve judged against type of diving undertaken
Sport Diver | ST5 Breathing Gas Planning & Systems Gas Calculation Example Dive Plan 25m for 20mins. = 2200 litres = 2640 litres 10L cylinder at 220bar 12L cylinder at 220bar ! Breathing rate x absolute pressure x dive time 25 l/min x 3.5 (25m) bar x 20mins = 1750 litres One third reserve (875 litres) = 875 litres Total required = 2625 litres OR Reserve = 1750 litres x 1.5 = 2625 litres 12L Cylinder needed for this dive
Sport Diver | ST5 Breathing Gas Planning & Systems Emergency Gas Planning Gas Consumption - a Function of: Depth Time to ascend (and settle time) Any decompression stops required Stress under water End of dive to first stop/check depth Out of gas - sharing single system Accelerated breathing rates > 25l/min
Sport Diver | ST5 Breathing Gas Planning & Systems Alternative Supply - AS Why have an AS? Gas supply loss - life threatening Urgent need to re-establish air supply Alternative supply carried by diver Alternative supply carried by buddy Sharing techniques stressful and have poor record of success All divers should carry an AS!
Sport Diver | ST5 Breathing Gas Planning & Systems AS Configurations No one configuration of AS suitable for all circumstances Configuration must be appropriate to diving conditions Types of Configuration ! Advantages ! Disadvantages ! Practicalities
Sport Diver | ST5 Breathing Gas Planning & Systems BC Demand Valve Advantage Minimises number of hoses Disadvantages No protection against first stage failure Cannot be used by buddy Restricts diver s head movement Divers must remain very close together Both divers consume gas from the same cylinder (1st stage)
Sport Diver | ST5 Breathing Gas Planning & Systems Octopus demand valve Should be visible & easily accessible Advantages ! Easy access for buddy ! Diver retains own regulator ! Long hose # Buddy use easier # Can also be used by wearer Disadvantages ! No protection against first stage failure ! Both divers breathing from same cylinder ! Both divers breathing from the same 1st stage ! 1st stage performance not assured
Sport Diver | ST5 Breathing Gas Planning & Systems Two Independent Regulators Pillar valve with two independent outlets Advantages All the advantages of an octopus Can protect against some primary first stage failures Disadvantages No protection against massive leak or free-flow Both divers breathing gas from the same cylinder
Sport Diver | ST5 Breathing Gas Planning & Systems Pony Cylinder & Regulator Comprises Additional cylinder, usually of 3 litre capacity ! Dedicated second regulator Advantages ! True emergency back-up to diver s own gas supply ! Additional gas capacity ! Fairly light Disadvantage ! Capacity inadequate for deeper dives involving decompression stops
Sport Diver | ST5 Breathing Gas Planning & Systems Twin Cylinders with Independent Regulators Advantages Same as pony cylinder Greater gas capacity Balanced trim underwater Considerations Monitoring two supplies Regulator switching Disadvantages Regulator failure loses access to gas in that cylinder Requires extra buoyancy
Sport Diver | ST5 Breathing Gas Planning & Systems Twin Cylinders with Isolation Manifold Isolation valve closes connection between cylinders Advantages ! No need for regulator switching ! Monitoring one supply Considerations ! Isolator must be accessible to wearer Disadvantages ! Additional O rings ! Requires extra buoyancy
Sport Diver | ST5 Breathing Gas Planning & Systems AS is a Back-up System Gas consumption must be planned with any kit configuration Gas back up/reserve should : ! Always be kept for emergency use (Emergency Gas Consumption) ! Not used to extend dive duration ! Be adequate for dive depth or conditions ! Be adequate for self and buddy at most critical point in the dive
Sport Diver | ST5 Breathing Gas Planning & Systems Maintenance Equipment is your lifeline Ensure ! All equipment is washed in fresh water after use # To remove dirt # Prevent build up of salt crystals Equipment is regularly serviced by competent technician Equipment treated with respect
Sport Diver | ST5 Breathing Gas Planning & Systems Updating or Buying New Equipment Is the system right for you? ! For the diving you are beginning to do? ! For the diving you intend doing in the future? ! Can you upgrade gradually? Consider complete system ! Overall weight of equipment ! Check buoyancy changes ! Shallow water check out dive Skills Practice - Practice - Practice!
Sport Diver | ST5 Breathing Gas Planning & Systems Summary Gas Planning ! Adequate size of cylinder for dive ! Calculating reserves Alternative Supply ! All divers should carry an AS ! Have suitable equipment configuration for planned dive ! Maintenance and care New Equipment ! Updating or new - implications ! Become familiar in safe, confined conditions Practice - Practice - Practice
Sport Diver | ST5 Breathing Gas Planning & Systems ST5.21 08/02
