TDI%20Inner%20Space%20Sytsems%20Megalodon%20Closed%20Circuit%20Rebreather%20Course

1
TDI Inner Space SytsemsMegalodonClosed Circuit
Rebreather Course
2
Overview of Course Structure
TDI Megalodon Closed Circuit Rebreather Diver
Course

• 1 - Introduction and Welcome
• 2 - The History and Development of Rebreathers
• 3 - Mechanics of the Megalodon
• 4 - Electronics
• 5 - Physiology - A Reflection for the CCR Diver

3
Overview of Course Structure continued
TDI Megalodon Closed Circuit Rebreather Diver
Course

• 6 - Lets Go Diving the Rebreather - Preparation
• 7 - Lets Go Diving the Rebreather - In the Water
• 8 - Avoiding Rebreather Incidents - Safe Diving
• 9 - Mod 2 Extension (Optional extra course)
• 10 - Mod 3 Extension (Optional extra course)

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TDI ISC Megalodon Rebreathers Diver Course

• Section 1
• Introduction and Welcome

5
Introduction and Welcome

• Welcome to a new way of thinking about diving
• Understand that you are ALL novices again
• You will develop new skills for CCR diving
  including
• Attitudes
• Disciplines
• Awareness

6
Introduction and Welcome

• Who the course is for and what you can expect to
  get out of it.
• COURSE PREREQUISITES
• 18 years of age
• Logged 100 dives
• Nitrox and Advanced Nitrox training
• COURSE CREDENTIALS
• To become qualified to dive the Inner Space
  Systems Megalodon on Air Diluent up to 40m/132ft
  with safety stops and 5 minutes max deco at 6m/
  20ft

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Introduction and Welcome

• Why CCR Diving
• Longer dive durations possible with very little
  equipment
• Almost silent and bubble free unless ascending
• Extremely efficient use of breathing gas
• Optional Nitrox mix for all depths according to
  user-selectable PPO2 setpoint
• Warm and moist comfortable breathing gas reducing
  risk of hypothermic tendencies

8
Introduction and Welcome

• What else can you expect to experience on this
  course?
• Many new terms for CCR not used in OC or SCR
  diving
• Change from a constant percentage Nitrox mix in
  OC to a variable percentage Nitrox mix with
  constant partial pressure in CCR mode
• Computer controlled gas injection system on
  ascent causes accelerating bouyancy
  characteristics
• We need to think differently
• Jump a billion years of evolutionary development
• An opportunity to almost evolve into a sea-going
  mammal with hours of sub-surface capability, and
  be back on land again for another fun filled
  experience

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TDI ISC Megalodon Rebreather Divers Course

• Section 2
• The History and
• Development of Rebreathers

10
The History and Development of Rebreathers

• Rebreathers in basic form have been around for
  over a century underwater, and longer for mine
  rescue work
• The earliest makes were pure oxygen devices
• The Englishman Henry Fleuss achieves a major
  milestone covering over 300 meters (1000 feet)
  underwater in the construction of the Severn
  railway tunnel a century ago
• Military rebreathers developed and used-Stealth

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The History and Development of Rebreathers

• The advent of readily available Nitrox to the
  recreational market fuelled the development of
  recreational nitrox SCR rebreathers
• Progress and need in the military theater saw the
  development of a number of electronic controlled
  CCR machines over the last two decades
• Some cave divers opted for passive mechanical SCR
  with
• no electronics
• Makes include the Electrolung Cis Lunar Drager
  Atlantis, Dolphin and Ray and Inspiration/Evolutio
  n.
• We see the advent of recreational CCRs with the
  Inspiration in 1997, followed by Prism,
  Megalodon,Ouroboros, Optima and Kiss, and in 2005
  the Evolution

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The History and Development of Rebreathers

• CONCEPTUAL REBREATHER DESIGN
• All need a scrubber for CO2 removal
• Pure Oxygen rebreather no need for electronics
  in basic form just keep manually adding gas when
  loop volume falls
• Semi Closed SCR uses a known nitrox for loop
  addition
• Mechanical rebreathers use a fractional volume
  technique to refresh gas
• Either Passive by sucking in fresh gas when
  oxygen in the loop volume is depleted and a
  diaphragm regulator re-injects to bring loop
  volume back up, or
• Active Constant flow rate of Nitrox to
  loop-vent excess

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The History and Development of Rebreathers

• Megalodon Rebreather
• Closed Circuit rebreathers (CCR)
• State of the art electronic controls
• Onboard sources of air and oxygen, scrubber,
  computer controlled variable Nitrox mixing
• Everything the recreational and technical diver
  needs

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TDI ISC MegalodonRebreather Diver Course

• Section 3
• Mechanics and basic functioning of the Megalodon
  rebreather

15
Mechanics and basic functioning of the ISC
Megalodon

• Divers Lungs
• DSV and Hoses
• Exhalation Counterlung
• Manual Inject Buttons
• Over Pressure Release Valve
• The Scrubber
• The Scrubber Cartridge
• The Head and handsets

Three Independent Oxygen Sensors The Handsets
and Gas Control Battery Compartments Cell
Connectors The Oxygen Supply Inhalation
Counterlung Diluent Gas Supply Heads Up
Display
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Mechanics and basic functioning of the ISC
Megalodon

• Including Optional System Components
• Auto-Diluent Additional Valve (ADV) and inline LP
  Flow Stop control device
• Tiger Gear Mounting System
• Mixed Gas Bypass
• Radial scrubber
• Neoprene Counter Lungs
• Choice of Different Back plates and wing Sytems

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Mechanics and basic functioning of the ISC
Megalodon

• DIVERS LUNGS
• The motor that powers the gas around the
  rebreather gas loop
• The point of exchange for O2 rich gas to the body
  and CO2 rich gas from the body
• When we inhale, clean O2 rich gas comes in from
  the Right.
• The flow is from the divers lungs through the
  mouthpiece to the Left

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Mechanics and basic functioning of the ISC
Megalodon

• MOUTHPIECE and HOSES
• Mouthpiece and one-way mushroom valves control
  direction of gas flow
• Timing of gas flow is in sympathy with divers
  breathing pattern.
• Hoses are large bore. This reduces the work of
  breathing (WOB)
• (Always close the mouthpiece to prevent fluding)

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Mechanics and basic functioning of the ISC
Megalodon

• EXHALATION COUNTERLUNG
• Counterlungs come from the factory as standard
  5.5 ltr lungs made from highly durable cordura.
  (Neoprene Counter lungs can be order from ISC)
• Flexible breathing bag to contain gas from body
• Contains both the ADV, Mixed Gas By-pass
  (Additional Extra) and the Gas Loop Over Pressure
  Release Valve

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Mechanics and basic functioning of the ISC
Megalodon

• THE CO2 SCRUBBER (or Stack)
• Gas path is from the exhalation counterlung,
  through the T-piece down to the bottom of the CO2
  scrubber
• It fans out to a large bore axial flow through
  the scrubber to reduce gas velocity and increase
  Dwell Time for CO2 removal
• The scrubber can is clear allowing the diver to
  see the Internal Dive Sorb.

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Mechanics and basic functioning of the ISC
Megalodon

• THE SCRUBBER CARTRIDGE
• Designed to remove CO2 from the gas loop.
• Situated on a spacer fitted with moisture pads to
  maintain air gap at bottom and soak up an
  moisture from the canister

22
Mechanics and basic functioning of the ISC
Megalodon

• The Scrubber Cartridge continued
• Different scrubber makes can give different
  duration times due to different granule sizes
• Only designed to remove CO2, not any other toxic
  compounds or contaminants in the breathing gas

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Mechanics and basic functioning of the ISC
Megalodon

• SCRUBBER MATERIALS
• Have a defined shelf life time and in use up to 3
  hours
• Effectiveness altered by time, temperature and
  moisture
• Sofnolime 797 grade recommended ( Other makes
  include Dragersorb and Sodasorb)
• Sofnolime is primarily a Sodium Hydroxide
  compound
• Needs proper packing to prevent CO2 channeling
• Efficiency is reduced by high gas flow rates
  (fast or skip breathing) or focused channeling
  characteristics
• In a properly assembled and properly functioning
  CCR system the CO2 scrubber is the Achilles
  Heel

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Mechanics and basic functioning of the ISC
Megalodon

• SCRUBBER MANAGEMENT
• No partial filling of the scrubber. New full
  canister every time
• Do not empty scrubber into a bag and re-pack the
  scrubber later- new and used granules are then
  mixed
• Do not store partly used scrubber for more than a
  few days. The material absorbs CO2 and grows mold

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Mechanics and basic functioning of the ISC
Megalodon

• CONTROLLERS
• GENERAL
• Power On
• Primary and Secondary Electronics
• Switch on manually
• Self testing electronics.
• (hear solenoid firing, HUD Flashing)
• 2 control buttons.
• Sleep mode to conserve power

ELECTRONIC WORKSHOP
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Mechanics and basic functioning of the ISC
Megalodon

• HANDSET CONTROLLER GENERALITIES
• Handset controllers are electronic handle
  carefully
• There are two independent handset controllers
  on the ISC Megalodon and a HUD
• The main function of the primary controller is to
  control oxygen injections and display real time
  information to the diver
• The main function of the secondary controller is
  to provide the diver with a totally independant
  PO2 reading.
• Can be switched on and off separately

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Mechanics and basic functioning of the ISC
Megalodon

• CONTROLLER FEATURES
• User Selectable Setpoints
• Built in System Monitor (Mv, Battery output,
  Temperature)
• Back light feature
• User Selectable Oxygen Injection Time
• Metric - Imperial / Fresh - Salt water
• User selectable O2 for Calibration.

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Mechanics and basic functioning of the ISC
Megalodon

• THE PRIMARY HANDSET
• Redundant controller PPO2 readings displayed to
  the diver
• Responsible for driving the Solinoid
• Requires independant Calibration.
• Primary Handset has a SSI (System Status
  Indicator - )
• Must be switched on to have a chance to drive the
  oxygen solenoid
• Will give indications of battery health (load /
  no load), Cell health, Loop Temp, Outside Temp.
• Redundancy so that 1 controller can fail while
  the other allows you to safely exit the water
• Need to constantly be checking PPO2 on the
  handset No Audio Alarm.

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Mechanics and basic functioning of the ISC
Megalodon

• THE SECONDARY HANDSET
• Redundant controller PPO2 readings displayed to
  the diver
• Passive Heads UP Display (All HUD functions are
  controlled by the secondary Handset)
• Requires independant Calibration.
• Will give indications of Battery health, Cell
  health, Loop Temp, Outside Temp.
• Need to constantly be checking PPO2 on the
  handset No Audio Alarm.

30
Mechanics and basic functioning of the ISC
Megalodon

• HEADS UP DISPLAY (HUD)
• Three Colour Indicator powered by the secondary
  handset
• Can be disabled by the diver
• Adjustable Brightness control
• The HUD works by benchmarking setpoint 1.0 in
  ORANGE
• Cell Readings Higher than 1.0 are indicated by
  blinking GREEN
• Cell Readings Lower than 1.0 are indicated by
  blinking RED
• Each Cell will blink seperately with a short
  pause between each announcement.

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Mechanics and basic functioning of the ISC
Megalodon

• THE CANNISTER LID
• The electronic brains of the device
• Consisting of two indipendant Battery packs,
  wiring for the handsets and HUD, Oxygen Sensor
  Pod Solinoid
• Great care should be taken when handling them
• For transport fully assemble rebreather or carry
  lid and handsets separately in a padded bag
• Treat it with the same care as a laptop

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Mechanics and basic functioning of the ISC
Megalodon

• 3 INDEPENDENT OXYGEN SENSORS
• 3 galvanic fuel cells each with a milli-volt
  output proportional to the oxygen exposure across
  their outer faces (breathing gas)
• The computers oxygen control averages all three
  Cells togethor to provide the PPO2
• This information is displayed to the diver both
  handsets
• Delicate pin connections
• Should never smell of toxic or other vapors

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Mechanics and basic functioning of the ISC
Megalodon

• CONSTANT PPO2 GAS CONTROL
• Remember Daltons Law from Advanced Nitrox
  Pressure gas FO2 x Pressure
• At different depths (gas pressures) for a
  constant PPO2 controller setting we will have a
  Nitrox mix that changes proportionally to
  pressure
• At any given depth we can calculate the Nitrox
  mix for any given PPO2 setting

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Mechanics and basic functioning of the ISC
Megalodon
35
Mechanics and basic functioning of the ISC
Megalodon

• BATTERY COMPARTMENT
• Two independant battery compartments
• Sealed to atmospheric pressure
• Battery packs consist of either 2 x 3.6v Lithium
  cells or 5 Alkaline batterys supplied by ISC

WARNING! YOUR ELECTRONICS REQUIRE BATTERY POWER
FOR OPERATION, ENSURE YOU HAVE ENOUGH POWER PRIOR
TO EACH DIVE. CELLS READING 5.0V OR LESS SHOULD
BE REPLACED
36
Mechanics and basic functioning of the ISC
Megalodon

• CELL CONNECTORS
• These are delicate and covered with red or blue
  moisture caps with holes for pressure
  equalization
• Take great care not to damage wires or connectors
  if changing cells
• Check Mv output from cells before each dive
• Repalce your cells when Mv output falls below 9mv

Your Instructor will run through the correct
procedure for calibrating the handsets and
conducting the required linearity checks
37
Mechanics and basic functioning of the ISC
Megalodon

• THE OXYGEN SUPPLY
• Dive tank switched on
• HP to SPG on front of Inhilation lung gives O2
  pressure
• LP hose feeds O2 to the LID for the solenoid
  from the first stage regulator
• First stage regulator I/P is usually 10 bar with
  a range of between 9.0 - 10.4 bar being
  acceptable
• You can choose dive tank size to suit your
  requirements
• Remember- Rich mix Right, Lean mix Left

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Mechanics and basic functioning of the ISC
Megalodon

• DILUENT GAS SUPPLY
• Need to use diluent below 6msw (20fsw)
• Manually add diluent on descent depressing the
  ADV to equalize the loop volume with pressure
  changes
• LP feeds to both the wing BCD and ADV
• Tank pressure is displayed on the SPG via HP hose
  over left shoulder
• Do not use for Drysuit inflation use off board
  gas
• IP normally set to 10 Bar

WARNING The Megalodon CCR does not have on-board
bailout, surficient bail out gas must be carried
at all times.
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TDI ISC Megalodn Rebreather Divers Course

• Section 6 Physiology
• A Reflection for the CCR Diver

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Physiology A Reflection for the CCR Diver

• BASIC PREMISE
• We need to breathe clean (CO2 and toxic gas
  free), appropriately oxygenated gas at all depths
  at all times to sustain life and to minimise DCS
  risk
• Appropriate nitrox mixes are delivered to the
  diver under software control according to the
  PPO2 selected by the diver

41
Physiology A Reflection for the CCR Diver

• ADDITIONAL CONCEPTS
• Ascent must be controlled at less than 9m per
  minute as per normal diving practice. DSC and DCI
  risks still apply
• Dangers of hypoxia, hyperoxia, asphyxia and the
  insidious CCR carbon dioxide poisoning
  (hypercapnia) need examination
• Lets review sources of contamination of breathing
  loop
• NOAA toxicity guidelines apply for Whole Body and
  Pulmonary Toxicity

42
Physiology A Reflection for the CCR Diver

• CO2 and HYPERCAPNIA
• Humans consume O2 at a cellular level and
  generate CO2 as a waste product
• Blood transports O2 to the cells and removes CO2
• Blood exchanges CO2 for O2 at the lung Alveoli
• The urge to breathe is driven by the level of CO2
  retained in the body (blood and cells)
• With hypercapnia and elevated CO2 levels, the
  breathing rate is increased (panting dypsnea)
  to try to vent the lungs and alveoli

43
Physiology A Reflection for the CCR Diver

• HYPERCANPNIA SYMPTOMS
• Mild Symptoms
• Headache
• Anxiety and dizziness
• Shortness of breath
• Severe Symptoms
• Strong anxiety bordering on panic
• Muscular difficulty and loss of dexterity in
  closing mouthpiece to bail out to OC
• Diluent flush doesnt seem to have any effect at
  first so divers often stop flushing when in fact
  they should continue flushing non-stop

44
Physiology A Reflection for the CCR Diver

• RE-INHALATION OF CO2
• CO2 normally removed by Sofnolime scrubber
• Conditions when this doesnt occur properly
• Scrubber expired or ignoring 3 hour duration rule
• Strenuous activity on rebreather
• Incorrect assembly of rebreather
• Wet or flooded scrubber
• Damaged mushroom valves gas goes backwards
• Skip breathing or breath holding creates
  pockets of very high CO2 content in the
  breathing loop
• Incorrect scrubber packing

45
Physiology A Reflection for the CCR Diver

• DEPTH VERSUS CO2
• As depth increases, work of breathing increases
  to push more gas molecules around the breathing
  loop. More CO2 is generated as a result.
• As gas density of molecules increases the
  efficacy of the scrubber granules to absorb CO2
  across its surface decreases

46
Physiology A Reflection for the CCR Diver

• HYPEROXIA
• Too much oxygen results in O2 toxicity risk
• Track O2 toxicity per NOAA tables (see manual)
• At a default setpoint of 1.3, NOAA limit 180
  minutes - But 80 of that is 144 minutes
• Do not exceed 80 of CNS and OTU tables
• Need to monitor CNS and OTUs carefully on
  multi-dive days or multiple repeat dive days

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Physiology A Reflection for the CCR Diver

• SYMPTOMS OF HYPEROXIA
• CONVENTID
• CON Convulsions
• V Visual disturbances/Tunnel vision
• E Ears ringing (Tinnitus)
• N Nausea
• T Tingling or twitching (facial)
• I Irritability
• D Dizziness or vertigo

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Physiology A Reflection for the CCR Diver

• PULMONARY TOXICITY
• O2 causes the alveoli surfaces in the lung to dry
  out thus slowly reducing lung efficiency
• OTUs 1 minute of 100 oxygen breathing at the
  surface
• Happens above a PPO2 of 0.5 thus very real danger
  for CCR Divers

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Physiology A Reflection for the CCR Diver

• HYPOXIA
• Occurs if the PPO2 drops below 0.16 at any time
• Real danger on ascent if solenoid fails
• Real danger if Oxygen tank is off or empty
• Symptoms can typically be breathlessness and
  panting, and lack of co-ordination
• Unconsciousness resulting in drowning can be
  sudden and without warning

50
Physiology A Reflection for the CCR Diver

• CNS TOXICITY AND OTUs
• Real danger of convulsing and drowning if your
  CNS is not monitored properly
• Always know the PPO2 in the loop and do a
  diluent flush to check any odd readings
• Track your CNS and OTUs on the NOAA tables in
  your manuals

51
Physiology A Reflection for the CCR Diver

• ASPHYXIA
• Like strangulation it is caused by a shortage of
  oxygen and buildup of CO2
• Restrictions in the breathing loop like a kinked
  mouthpiece hose can cause it
• Easily noticed early in a dive
• Ineffective or exhausted scrubber also can cause
  asphyxia
• Eventually results in unconsciousness

52
TDI ISC Megalodon Rebreather Divers Course

• Section 7
• Lets Go Dive the Rebreather - Preparation

53
Lets Go Diving the Rebreather - Preparation

• EQUIPMENT ASSEMBLY and INSPECTION
• Preparation
• Assemble the rebreather according to a checklist
  (refer to manual), initially under Instructor
  guidance
• Be meticulous and do not get distracted

54
Pay particular attention to the following during
assembly and inspection
Lets Go Diving the Rebreather - Preparation

• Positive negative pressure tests
• Cylinder contents analysis
• Cylinder pressure on SPGs

HUD LEDs functioning (if HUD used) Listen
for solenoid firing when handsets switched
on Switches on handsets working
normally Mushroom valve checks on the
mouthpiece assembly
Wing and Auto-Air checks Scrubber
packing Hose O-ring lubrication Battery
power levels
55
Lets Go Diving the Rebreather - Preparation

• WEIGHTING AND TRIM
• Ensure the unit is well weighted at the top.
• Add to the sides on the waistband to trim
• More weight needed if diving in a drysuit

56
Lets Go Diving the Rebreather - Preparation

• MACHINE CALIBRATION
• Absolutely critical part of the preparation
  process
• Always put in of oxygen in the lid at 98 - all
  the air cannot be displaced from the lid
• Is the Mbar reading on the Megalodn handset are
  Automatically sensed
• Mbar readings are critical for altitude diving
• Watch the cell readings rise during calibration
  and check for any slow or limited cells

Your Instructor will demonstrate correct
calibration procedures
57
Lets Go Diving the Rebreather - Preparation

• GETTING THE FEEL OF THE MACHINE ON LAND
• Putting on the machine for a dry dive
• Adjust straps to fit body correctly and tuck away
  loose ends
• Power up and sequence handset control through to
  dive mode under guidance of Instructor
• Select your Setpoint
• Put on mask to prevent breathing through nose
• Breathe on the machine while watching PPO2
  readings on handsets listen for solenoid firing

58
Lets Go Diving the Rebreather - Preparation

• Dry dive simulations (approx 30 minutes)
• These provide useful simulations in a safe
  environment for learning and troubleshooting

59
Lets Go Diving the Rebreather - Preparation

• OVERFILLED BREATHING LOOP
• Allow loop volume to increase by injecting a
  little diluent.
• Get the feel of over pressurized loop
  inhibiting the exhale cycle
• Release excess gas repeat again

60
Lets Go Diving the Rebreather - Preparation

• UNDERFILLED BREATHING LOOP
• Exhale fully through the nose, twice
• Feel the effect of too little pressure in the
  loop, difficulty inhaling properly
• Add gas using the ADV, for volume adjustment

61
Lets Go Diving the Rebreather - Preparation

• NORMAL LOOP VOLUME
• Continue normal breathing mode while seated or
  stationary
• Observe PPO2 readings and how closely they follow
  the setpoint
• Listen to solenoid firing and ensure you are
  feeling fine on machine

62
Lets Go Diving the Rebreather - Preparation

• GENTLE EXERCISE
• Walk about with the rebreather on
• Simulate moderate exercise
• Notice breathing, rate increases, and solenoid
  firing more often than when at rest.

63
Lets Go Diving the Rebreather - Preparation

• INCREASED WORK LEVEL
• Jog in place for a couple of minutes, or do a few
  squats with the machine on to raise heart and
  respiratory rates
• Observe PPO2 tracking, hear solenoid firing and
  notice little or no change in loop volume
• The student should still feel fine and have no
  CO2 problems

64
Lets Go Diving the Rebreather - Preparation

• SETPOINT CHANGES
• Switch Setpoint when the PPO2 rises observe PPO2
  on handset to ensure fuctionality
• Test how long it takes to breathe the loop back
  down to a PPO2 of 0.4 at rest

REMEMBER! There or no audio alarms for High or
Low Oxygen on the Megalodon the diver should be
monitoring the handsets at all times.
65
Lets Go Diving the Rebreather - Preparation

• OPEN CIRCUIT BAIL-OUT
• Close mouthpiece and come off the loop
• Switch to OC bailout take 3 breaths, return to
  the loop and open mouthpiece
• Observe loop volume increase as O2 is injected to
  bring PPO2 back up to setpoint because of the air
  you introduce to the loop

66
Lets Go Diving the Rebreather - Preparation

• DILUENT FLUSH
• Inject diluent using the ADV
• Vent gas through by exhaling
• Repeat three times and observe reduction in PPO2.
  Listen to solenoid firing.

67
Lets Go Diving the Rebreather - Preparation

• MANUAL GAS ADDITION
• Give a small squirt of O2 with the manual
  addition button and observe the PPO2 reading
• Repeat the exercise with diluent
• Repeat to get a feel for the addition buttons

68
TDI ISC Megalodon Rebreather Divers Course

• Section 8
• Lets Go Dive the Rebreather
• In the Water

69
Lets Go Diving the Rebreather In the Water

• Rule No 1
• If in doubt bail out!
• Rule no 2
• If something feels wrong it is!

70
Lets Go Diving the Rebreather In the Water

• DIVE PLANNING
• Select depth and time for a safe no-deco time
• Scrubber monitoring and planning (2.5 3 hour
  rule)
• Gas volume planning enough for a bail-out
• Oxygen planning CNS and OTUs
• Is this a repetitive dive?
• Thermal protection appropriate for conditions and
  duration of dive
• Brief team, do ABCs and enter the water under
• guidance of your Instructor

71
Lets Go Diving the Rebreather In the Water

• FIRST IMPRESSIONS IN THE WATER
• Silence
• Bubble-free
• Listen for the solenoid firing
• Check PPO2 on the handsets every minute
• Dynamic bouyancy change caused by
  computer-controlled oxygen
• Unit is bouyant at shoulder level due to air
  volume in counterlungs and hoses
• Add weight at the top for trim
• Remember no matter how experienced you are on
  OC, you are now a beginner again

72
Lets Go Diving the Rebreather In the Water

• EARLY TECHNIQUE POINTERS
• Do not expect to get it right first time
• Try to keep the loop volume at a minimum for
  comfort
• Keep a steady depth level
• Try to maintain a horizontal, neutral bouyancy,
  attitude while swimming
• Use vertical attitude only when testing skills
  under instructor guidance
• Be generous with weighting (1 or 2kg over)

73
Lets Go Diving the Rebreather In the Water

• BASIC WATER SKILLS DEVELOPMENT
• Mouthpiece opening and closing techniques
• Open Circuit bail-out
• Diluent flushes and checking PPO2 drop
• Check diluent flush predictions
• Bouyancy normalisation while swimming
• Constant checking of PPO2 on handsets
• Understanding and reacting to alarm conditions
  (mostly simulated while on course)
• Loop volume control

74
Lets Go Diving the Rebreather In the Water

• BAD DAS DRILLS
• In the event of in-water problems, rely on
• BAD-DAS drills
• B Bail-out to open circuit
• A Anxiety breaths (3)
• D Decide what to do
• If returning to the loop, then
• D Diluent flush breathe fresh gas
• A Always know your PPO2 check handsets
• S Skills. Apply appropriate skills gained during
  training to overcome the problem

75
Lets Go Diving the Rebreather In the Water

• LOW O2 DRILLS
• Manual flight
• 1 Using O2 inflator
• 2 Adding oxygen using O2 tank valve
• 3 Using machine in semi-closed circuit mode
• Low oxygen danger
• 1 Solenoid stuck closed
• 2 O2 tank empty or switched off
• Handset failure or switched off
• If both are blank, go open circuit or if gas
  volumes dictate, switch to semi-closed
• circuit mode

76
Lets Go Diving the Rebreather In the Water

• HIGH OXYGEN DRILLS
• Open circuit bailout
• Use of diluent flush to drop PPO2
• Closing oxygen tank if solenoid fails open

77
Lets Go Diving the Rebreather In the Water

• MENU MODE DRILLS
• Sequencing through menu commands in water to
  become familiar with functionality
• Changing Setpoints
• Observe System Monitor
• Observe SSI indicator

78
Lets Go Diving the Rebreather In the Water

• HYPERCAPNIA DRILLS
• Open Circuit Bailout
• Diluent flushes
• Practice/Practice/Practice

79
Lets Go Diving the Rebreather In the Water

• ELECTRONICS MALFUNCTIONS
• Handset and controller problems
• Cell errors or missing cells
• Poor PPO2 tracking to setpoint
• Possible Loop Floods

80
TDI ISC Megalodon Rebreather Divers Course

• Section 9
• Avoiding Rebreather Incidents
• Safe Diving

81
Avoiding Rebreather incidents Safe Diving

• All the training in the world is useless if you
  do not adopt the following as your personal
  mantra for CCR Diving
• Safe Attitude
• Safe and enhanced Awareness
• Safe and structured Discipline

82
Avoiding Rebreather incidents Safe Diving

• OPERATIONAL MAINTENANCE
• Check battery connections are clean and dry
• Ensure handsets are cleaned in fresh water,
• Keep O-rings well cleaned and lubricated to
  prevent abrasion and other damage

83
Avoiding Rebreather incidents Safe Diving
REMEMBER DURING PRE-DIVE PREPARATION

• Properly assemble and check according to a check
  list
• Do not get distracted during calibration
• Do all the pre-dive checks and then go live for
  a short dry-dive to pre-breathe prior to
  entering water in order to ensure dynamic
  functionality of the machine

84
Avoiding Rebreather incidents Safe Diving

• DIVE PLANNING
• Break dive into logical waypoints to do checks
  and flushes for safety
• Usual waypoints
• _ 6msw (20fsw) bubble leak check
• On descent - switch to high setpoints
• On reaching bottom - diluent flush and check
  guages and handsets
• After pre-set time or leaving bottom - diluent
  flush
• On ascent (10msw or less) - gas venting to
  control bouyancy

85
Avoiding Rebreather incidents Safe Diving

• REMEMBER ON THE DESCENT
• Do a shallow (6msw/20fsw) bubble check
• Descend slowly to control breathing loop volume
• Watch the PPO2
• Switch to high setpoint according to plan

86
Avoiding Rebreather incidents Safe Diving

• REMEMBER ON THE ASCENT
• PPO2 will drop, solenoid should fire, and oxygen
  should come into the loop quickly rapid
  bouyancy increase
• Check PPO2 closely on ascent to reduce Hypoxic
  risk if there is insufficient O2 in the loop
• Carefully control ascent rate
• 3 potential bouyancy devices drysuit, wing and
  loop counterlungs

87
Avoiding Rebreather incidents Safe Diving

• REMEMBER AT THE SURFACE
• NEVER switch off the handsets or tanks at the
  surface above deep water
• Only shut down after equipment has been taken off
• You still need to watch your PPO2 if you breathe
  on the loop at the surface
• Its the best snorkel you ever bought!!!

88
Avoiding Rebreather incidents Safe Diving

• REMEMBER AFTER THE DIVE
• Gas up again for the following dive
• Check and replace batteries/scrubber
• as necessary
• Disinfect and clean as necessary
• Conduct all other system checks to ensure correct
  functionality of cells and handsets
• Log your dives

89
Avoiding Rebreather incidents Safe Diving

• TDI Training and Manufacturers Manuals
• Errors and troubleshooting are well documented
  for reference
• Maintain your own service log for
  batteries/scrubber and other service needs
• Document your rebreather experiences