Docstoc

Rebreather Fundamentals

Document Sample
Rebreather Fundamentals Powered By Docstoc
					BSAC Rebreather Diving




   Rebreather
  Fundamentals
 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
   Try-dive
      Unit start-up & functional checks
      Try-dive (20 minutes)
      Shut down procedures
 Rebreather
Fundamentals   Aims


   Why Dive a Rebreather?
   Rebreathers in Practice
   Simple Rebreather
         Semi-Closed Rebreather
         Closed Circuit Rebreather
   Buddying a Rebreather Diver
   What If?
 Rebreather
Fundamentals   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
 Rebreather
Fundamentals    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
                     160
       Consum ption
                     140
         rate (l/m )
                     120
                     100
                      80                                                         CC
                      60
                                                                                 SCR
                      40
                                                                                 OC (25)
                      20
                       0
                           0 3 6
                                 9 12 15 18
                                            21   24 27 30
                                                          33 36 39
                                                                   42 45 48
                                                                            51
                                                                Depth (m )
 Rebreather
Fundamentals   PO2 Advantage

 Inspiration Maximises PO2
 SCR as per Nitrox


               PO2
                     1.60
                     1.40
                     1.20
                     1.00
                     0.80                                                 OC
                     0.60                                                 SCR
                     0.40
                                                                          CC
                     0.20
                     0.00
                            0 3 6
                                  9 12 15
                                          18 21 24
                                                   27 30 33
                                                            36 39 42
                                                                     45
                                                             Depth (m)
 Rebreather
Fundamentals    Decompression limits

 Longer decompression no stop limits

    No stop time 200
       (mins)
                 150


                 100                                                    Air
                                                                        Nitrox
                  50                                                    PO2


                   0
                    12 15 18
                             21 24 27
                                        30   33   36   39   42  45
                                                            Depth (m)
 Rebreather
Fundamentals   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
 Rebreather
Fundamentals   Simple Rebreather


                                Counterlung


                    Breathing
                      Loop




                                Dump
                                Valve




                    Scrubber            Oxygen
 Rebreather
Fundamentals   Simple Rebreather


                   Simple Rebreather



          Semi-closed               Closed Circuit
       Circuit Rebreather            Rebreather

   Difference is in the way that the addition of
   oxygen is effected
 Rebreather
Fundamentals   Semi-Closed Rebreather

  Metering flow orifice (jet)




                                Bypass




                                         Vent
                                         Valve



                 On-board                        Off-board
     Nitrox                                      Bail–out
                 Bail-out?
 Rebreather
Fundamentals     Closed Circuit Rebreather

                 On-
                board
               bail-out
                                      Handsets

                                      Buzzer




                 Optional
                  Auto                           Oxygen
                 Demand                           inject
                  Valve                           valve
                            Oxygen
                            sensors
       Diluent                (3)                          Oxygen
 Rebreather
Fundamentals   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
 Rebreather
Fundamentals   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
 Rebreather
Fundamentals    SCR Rebreather Diving
      Gas
      Gauge                                  Unit shut
      Gag                                     down


                Post entry &
               bubble checks

                                 Monitor
                                   Gas
                                 Supply &   Vent loop
                                   FO2

   Buoyancy                                 Buoyancy
                                  Swim
                               around not
                                  over
 Rebreather
Fundamentals    CCR Rebreather Diving
      Start-up
      & function                                        Unit shut
      checks                                             down


                Post entry &
               bubble checks                Set point
                                             change
                                  Monitor
                 Set point       handsets
                  change
      Add                                           Vent loop
     diluent
   Buoyancy                                         Buoyancy
                                  Swim
                               around not
                                  over
               What if………
 Rebreather
Fundamentals




  Something goes wrong with the
  unit……

       If in doubt…
       Close mouthpiece then Bail-out!
 Rebreather
Fundamentals   Summary


 Why Dive a Rebreather?
 Simple rebreather
  Semi-Closed Rebreather
  Closed Circuit
   Rebreather
 Buddying
 What If…
 Rebreather
Fundamentals   Questions?

				
DOCUMENT INFO