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BSAC Rebreather Diving

BSAC Rebreather Diving. Rebreather Fundamentals. Try-dive outline. Theory Rebreather Fundamentals Marshalling Rebreather Divers (optional) Dry Session Unit configuration & operation 2 students per instructor Own mask & fins Tee-shirt / pool suit recommended Be ready on pool side

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BSAC Rebreather Diving

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  1. BSAC Rebreather Diving Rebreather Fundamentals

  2. Try-dive outline • Theory • Rebreather Fundamentals • Marshalling Rebreather Divers (optional) • Dry Session • Unit configuration & operation • 2 students per instructor • Own mask & fins • Tee-shirt / pool suit recommended • Be ready on pool side • Try-dive • Unit start-up & functional checks • Try-dive (20 minutes) • Shut down procedures

  3. Aims • Why Dive a Rebreather? • Rebreathers in Practice • Simple Rebreather • Semi-Closed Rebreather • Closed Circuit Rebreather • Buddying a Rebreather Diver • What If?

  4. Why Dive a Rebreather? • Gas extender • Breathing rate independent • Decreased gas usage • Easier Logistics in remote locations • Nitrox benefits • Longer bottom times, i.e., increased no stop times • Reduce potential for DCI • Warm, moist breathing media • Reduced chilling • No dry throat • Less dehydrated • Reduced breathing effort • Reduced effect on the environment • Reduced bubbles • Reduced noise • Get closer to marine life

  5. Longer Gas Duration Metabolic Consumption 1 litre of oxygen / minute • CCR 20 bar oxygen per hour (3 litre cylinder) • SCR <= 10 l/min supply gas independent of depth • OC depth & workload dependent

  6. PO2 Advantage Inspiration Maximises PO2 SCR as per Nitrox

  7. Decompression limits Longer decompression no stop limits

  8. Rebreathers in Practice • Meticulous attention required to: • Unit maintenance & preparation • Personal dive skills • Additional procedures • Initially daunting • Become normal diving practice • Non-rebreather buddies • Need to know what to expect • Need to understand implications

  9. Simple Rebreather Counterlung Breathing Loop Dump Valve Oxygen Scrubber

  10. Semi-closed Circuit Rebreather Closed Circuit Rebreather Simple Rebreather Simple Rebreather Difference is in the way that the addition of oxygen is effected

  11. Semi-Closed Rebreather Metering flow orifice (jet) Bypass Vent Valve Off-board Bail–out On-board Bail-out? Nitrox

  12. Closed Circuit Rebreather On-board bail-out Handsets Buzzer OptionalAuto Demand Valve Oxygen inject valve Oxygen sensors (3) Diluent Oxygen

  13. Static Lung Loading • Definition: • Pressure imbalance between the counterlungs and diver’s lungs in different body positions • Counterlung position higher • Easier to exhale • Harder to inhale, e.g., Dräger Dolphin Compromise is over the shoulder! • Example, APD Inspiration Counterlung position lower • Easier to inhale • Harder to exhale

  14. Buddying a Rebreather Diver • Redundant gas supply • DSMB / surface detection aids • Both divers conduct most conservative dive profile • Must be familiar with how to rescue a rebreather diver: • CBL of rebreather diver • Rebreather mouthpiece implications

  15. SCR Rebreather Diving Gas GaugeGag Unit shut down Post entry & bubble checks Monitor Gas Supply & FO2 Vent loop Buoyancy Buoyancy Swim around not over

  16. CCR Rebreather Diving Start-up & function checks Unit shut down Post entry & bubble checks Set point change Monitor handsets Set point change Add diluent Vent loop Buoyancy Buoyancy Swim around not over

  17. What if……… • If in doubt… • Close mouthpiece then Bail-out! Something goes wrong with the unit……

  18. Summary • Why Dive a Rebreather? • Simple rebreather • Semi-Closed Rebreather • Closed Circuit Rebreather • Buddying • What If…

  19. Questions?

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