Transcript Manufacturers Slides

CCR Diver Course
Sentinel
Workbook Slides By:
Kevin Gurr & Phil Short
Sentinel Rebreather Layout
Sentinel CCR
•Protective case
•Back-mounted counterlung
•Primary Display
•Backup PO2 Display
•Forward and Rear HUD
•Oxygen and Diluent gas
blocks with isolators
•Expedition version with
CO2 monitor
Sentinel Key Features
•2.2 KG Canister.
•4.5 Liter counter lung volume.
•O2 solenoid valve with isolator.
•O2 manual bypass.
•Diluent ADV with isolator.
•Diluent manual bypass.
•Water removal system.
System Layout
Sentinel Safety Features
•Integral protected counter lung.
•Backup oxygen display.
•Manual gas addition.
•Off-board gas plug-in option.
•Visual and tactile alarms.
•No ‘lock outs’.
•Data-logging.
Sentinel Safety Features
• CDM (Canister duration monitor).
• CDM comprises TPM (Temperature Profile Meter)
and O2 injection counter.
• Auto-breathe breathing detection will turn unit on or;
– Auto turn on at 1.3 absolute pressure
– Manual turn on
• CO2 sensor option on Expedition Sentinel
Sentinel Technical Data
•Primary display, HUD and Rear HUD.
•Independent ‘Backup’ 3 sensor PO2 display.
•On-board decompression.
•Variable and Auto PO2 control while submerged.
•Dynamic HP alarms.
•Data logging system
Electrical Oxygen Sensors
• Critical components - redundancy
• Galvanic fuel cells
• Lead anode - gold plated cathode
- potassium hydroxide solution
• Lead is oxidized producing small
voltage between anode & cathode
• Individually calibrated
• Affected by humidity and temperature
Sentinel Oxygen Cells
•Oxygen sensor with moisture tolerant membrane
•Removable with no special tools
•Moisture tolerant
•Robust connection system
Sentinel Oxygen Controller
•3 sensor polling.
•Ability to isolate ‘rogue’ sensors.
•Ability to force manual Set-point tracking.
•Variable valve control for fast ascents.
•Extremely accurate Set-point tracking.
•Automatic/manual air calibration.
Sentinel
Power On Screen
Sentinel
Interpreting the PO2 Display
• The PO2’s from the 3 Oxygen Cells are the most
important data you have to monitor
Do It Regularly!
• Compare the PO2 displays to each other and to the
Set-point and the Backup Display
• Note the speed at which the PO2 changes
– a slow reacting cell probably indicates moisture on that
cell’s sensing face
• If in doubt confirm with Diluent flushes
Sentinel
Controlling Set-point
• Minimum Set-point
– System will maintain a minimum of 0.4 at all times with
the unit turned on even on an open circuit bailout
– Auto breathe ensures automatic turn on at less than 0.17
PO2
• Changing Set-point
– Set-point can be changed Automatically or manually
underwater
– Auto Set-point modes can be set for bottom and deco PO2’s
• Set-point range
– 0.4 to 1.6 is allowable
Sentinel
Primary Dive Screens
Sentinel Rebreather HUD
LED Mode
No flash-No Deco
Slow Flash – Deco ceiling above
Fast Flash – Violated ceiling/fast ascent
Solid Green
All good
Flashing Red/Buzzer
Dangerous Alarm Condition
Prepare to Bailout!
Monitor Displays
Flashing Green/Blue
Monitor Displays
PO2 Mode
Light
Status
Meaning
Solid
Green
At Setpoint
Slow Flash Below SetGreen
point
Fast Flash
Green
Above Setpoint
CCR Design and Functionality
Cylinder Considerations
• Diluent primarily used only during descents
• Oxygen is more likely to limit dive duration
• Larger cylinders can be added or off-board
cylinders attached
The Counter lungs
• Necessary for free breathing
– Empty bottle vs. paper bag
• Constant Buoyancy
– Exhale: lung volume decreased & bag volume increases
– Inhale: lung volume increases & bag volume decreases
– Compare to Open-Circuit Scuba
• Position to minimize pressure differential between
lungs and counter lung
Hydrostatic Effect
• Chest mounted bag - diver horizontal
– inhale less effort
– exhale more effort
Hydrostatic Effect
• Back mounted bag - diver horizontal
– inhale more effort
– exhale less effort
Hydrostatic Effect
• Shoulder mounted bags.
• Most positions: Inhale & exhale have a more
balanced effort.
Resistive Work of Breathing.
• Gas flow within a unit
• Size of hoses and orifices generate a resistance to
breathing
• Includes design of mouthpiece, mushroom valves,
hoses, counter lungs etc
• Gas density and depth dependent: deeper dives net
denser gas, net higher resistive WOB
• Workload also affects resistive WOB-more gas flow
equals more obstructions and turbulence
• CE Test data important to review
Breathing Loop
Absorbent canister for CO2 removal
– Exhaled gas passes through this and is filtered for CO2
– Efficiency and work of breathing is related to size / types of
granules
– Duration affected by temperature and gas density
– Design also affects the efficiency
Absorbent Canister Design
• Gas exposed to sufficient surface area of
absorbent to remove CO2
• Gas flow rate across absorbent allows sufficient
time (dwell time) for chemical removal of CO2
• Simple & correct packing to prevent ‘channeling’
of absorbent
• Prevents excess moisture from reaching absorbent
Absorbent Canister Types
Axial
Cross Flow
Radial
Axial Canister
Gas flows through a block of
absorbent in linear direction
Cross Flow Canister
Gas flows through a block of
absorbent with a direction change
Cross
Flow
Absorbent Canister
Radial Flow System - gas enters center of
‘doughnut’ cross section & radiates outwards
through the absorbent (or from the outside
inwards).
Absorbent Types
Barium Hydroxide - the earliest form of
absorbent used
Lithium Hydroxide - long lasting and efficient,
but must be carefully handled and is expensive
Soda Lime - a commonly used absorbent
available under trade names such as Sofnolime™
and Dräger Divesorb®
All Absorbents will produce a caustic
effect if mixed with water.
Carbon Dioxide Absorption
• Typical diving grade soda lime absorbent
– 94% Calcium Hydroxide [Ca(OH)2]
– 4% Sodium Hydroxide [NaOH]
– 1% Potassium Hydroxide [KOH]
– <1% Silica (binding agent)
• Some types change color with use
– Do not rely on this as an indicator of use
• Should be slightly hydrated to ensure production
of Carbonic Acid
Carbon Dioxide Absorption
• CO2 reacts with water (vapor) to form weak
Carbonic Acid
• Carbonic Acid reacts with base to produce salt
(chalk), water, & heat
• Resultant chemical reaction produces a strong
alkaline material
CO2 Absorbent
Duration Variables
• Chemical composition
• Canister volume
• Temperature
• Exertion level (CO2 generation)
• Moisture level
• Gas density/depth
• Rebreather design
CO2 Absorbent Testing
• The Sentinel was tested using:
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1 - 2.5 mm (797 Grade) Sofnolime granules
Water temp 4ºC
Depth of 15m and 40m on air and 100m on Heliox
CO2 production rate of 1.6l/m
40l/m breathing rate
Sentinel
CO2 Absorbent Duration
• At CE test rates on air at 40m, the canister will
last 180 minutes
• At 100m on Heliox it will last 160 minutes
Durations with other absorbents have not been
tested and cannot be guaranteed and may
vary considerably
Hypercapnia
PCO2
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0.02 ATA/Bar - doubles breathing rate (dyspnea)
0.06 ATA/Bar - distress, confusion, lack of coordination
0.10 ATA/Bar - severe mental impairment
0. 12 ATA/Bar - loss of consciousness, death
CE CO2 limits and alarms on the Sentinel
Expedition are at 5 milibar and 10 milibar
Sentinel Dive Procedures
Packing Sentinel
CO2 Absorbent Canister
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Empty used absorbent
Remove absorbent stuck to walls
Dispose of absorbent (use makers guidelines)
Inspect cartridge and canister for damage
Periodically flush canister with warm soapy water to
clean residue. Ensure base screen slides up and
down
• Repack canister exactly following instructions on
the attached label
Face Masks
• Rebreathers have limited gas supply
• Well fitting mask to prevent leaks
• Repeated mask clearing depletes gas supply
• Full face mask allows U/W communications
– full face must have a bite mouthpiece to prevent
CO2 build-up
Breathing Characteristics
• More natural breathing than Open Circuit
• Breathing resistance depends on location of
counter lung and diver’s body position
• Water in loop increases breathing resistance
• Humid gas reduces dehydration of diver
• Warm gas reduces heat loss from diver
– Both effects should reduce the risk of DCS
Sentinel Pre-Dive Checks
Turn on the unit by doing a short push of both
buttons on the Primary display.
Aborted Pre-dive checks will be
recorded in the Logbook.
An entry into the water without a complete Predive will record and abort in the logbook.
Sentinel Pre-Breathe Sequence
• Pre-breathe 5 minutes
– open mouthpiece and breathe normally WITH NOSE BLOCKED.
– Continue breathing for at least 1 minute if the graph is still red after
5 minutes, suspect flooding if yellow/green graph is not eventually
displayed
Basic Dive Procedures
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Initial in-water verification
Descent - manual diluent addition
Buoyancy control
Monitoring PO2
Minimum loop volume
Monitoring gas supplies
Ascents
Initial in-water verification
at 6 m
• Check for leaks
• Verify oxygen injection is working
• Verify ADV is operating
• Adjust buoyancy
Descents
• Counter lung collapses as ambient pressure increases
• Compensation by Automatic Diluent Valve (ADV)
gas addition or manual bypass
• Rapid descents cause PO2 spikes
• Select low PO2 Set-point for descent or AUTO mode
• Switch to high PO2 Set-point at target depth or check
AUTO switch has occurred.
Buoyancy Control
• No buoyancy changes during breathing cycle
• Buoyancy adjustments using lung volume therefore
not feasible
• Counter lung collapses during descent & expands
during ascent
• Buoyancy change from fully collapsed to fully
inflated is considerable. Use correct counter lung
counter-weighting (approx. 4kg) to ensure unit is
slightly negatively buoyant.
Sentinel
PO2 Monitoring
• Hypoxia & Hyperoxia are real dangers in all rebreathers
• Frequent cross checking of Primary and Backup
displays
Constant PO2 Monitoring
is Vital
Minimum Loop Volume
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Loop volume just enough for one normal breath
Extra volume is wasted gas and added buoyancy
PO2 stays closer to Set-point
Test loop volume with ADV disabled.
Monitoring Gas Supplies
• Gas supplies used at much slower rate
than OC, but monitoring is still necessary
• Small gas supply quickly used if there are
leaks in the loop, frequent mask clearing
or frequent ascents / descents
• O2 supply not diluent supply typically
limits the dive duration
Sentinel
Ascents
• Buoyancy changes due to expansion of the
counter lung, BCD, and dry suit
• PO2 should not be allowed to drop
• The Sentinel will maintain close to the Setpoint during a normal ascent due to its
dynamic control algorithm
• Oxygen can be manually added if necessary
Failure Modes
Emergency Scenarios
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Hypoxia
Hyperoxia
Hypercapnia
Solenoid/injection system failures
Complete electronics failure
Open circuit bailouts
In an emergency - it is the poorly learned
survival skills which are lost first
Sentinel CCR Skills
See the training video and skills list for skill detail
• Complete Pre-dive check sequence, including the 5
minute Pre-breathe (with CDM monitoring).
• Complete automatic and manual calibration of cells.
• In water leak and function checks.
• Open circuit bailout (including BOV use) and open
circuit bailout ascents.
• Manual control of PO2.
• CCR removal and replacement at surface.
• Set-point switching and automatic Set-point control.
Sentinel CCR Skills
See the training video and skills list for skill detail
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Delayed surface marker buoy use on CCR.
Diluent flush.
Oxygen volume drill.
Simulated Hypoxia drill.
Simulated Hyperoxia drill.
Metabolic rate drill.
Maintenance of PO2 between deco stops.
Partial flood recovery drill.
Cell disabling and manual PO2 control.
Sentinel CCR Skills
See the training video and skills list for skill detail
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HUD (Head Up Display) use.
Semi Closed (gas extender drill).
Electronics monitoring.
Gas sharing.
Various multi-part training scenarios.
Rebreather Maintenance
• Disinfecting & cleaning
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CO2 seal
O-rings
Canister
Hoses
Counter lungs
BCD
Testing
– If the unit fails the negative test and the fault is not easily
recognisable.
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Turn on all gases.
Make sure the solenoid and ADV sliders are open
Close the OPV
Close the mouthpiece (open circuit mode).
– Fully immerse the unit (hoses, mouthpiece etc.) with the
cover removed and look for leaks.
– If no leaks are visible but the OPV slowly vents gas, then
suspect either the ADV or the solenoid.
• To test the ADV for leaks, close the gas block shutoff and see if the
OPV stops leaking. Service as required.
• To test the solenoid for leaks, close the gas block shutoff and see if
the OPV stops leaking. Service as required.
Disinfecting & Cleaning
• Rebreather - warm, damp environment is ideal for
bacterial growth
• Breathing loop regularly disinfected & dried
thoroughly
• Safe disinfectants only – Virkon is recommended
• Incorrect cleaning agents may affect Orings/counterlungs/mushroom valves
• O2 compatible lubricants only on HP parts silicone
grease on all else
Disinfecting & Cleaning
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Full disinfect once a week
Use only recommended disinfectant for all parts
Stand part in solution for maximum of 10 minutes
Fresh water flush
Allow to dry
After Every Days Diving
• Flush hoses and mouthpiece with fresh water
• Re-pack absorbent, fill cylinders as necessary
• If using absorbent again, keep sealed in the
loop.
• If excessive moisture around the sensors,
remove and dry.
Post Dive & Storage
• Rinse exterior of unit
• Remove/dispose absorbent
• Clean absorbent canister
• Rinse/disinfect breathing bags & hoses
• For storage, leave cylinders partially filled
• Allow unit to dry, lubricate all O-rings
• Remove oxygen sensors
O-Rings
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Do not disturb O-rings unnecessarily
Carefully inspect prior to reassemble
Replace damaged O-rings
Excessive lubrication not required
Check O-ring grooves for damage
O2 compatible lubricants only on HP parts
Factory sealed compartments - don’t tamper
Hoses
• Check for visible damage after every dive
• Store in a carry case
• Do not carry unit by hoses
• Do not place heavy equipment on hoses
Counter lungs
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Keep dry (vented) when not in use.
Beware of bugs crawling into counterlungs
Check loop interface ports for damage to threads, etc.
Use loop end caps
BCD
• Vital for buoyancy control & safety
• Visual inspections regularly
• Fully inflate and check for leaks, pre-dive
Summary
• Advantages of CCR greatly outweigh
the disadvantages
• Correct training is obligatory
Always do all pre-dive checks
Always Pre-breathe the unit
Always know your PO2
Practice your skills
Be Sensible, Be Safe