Sentinel CCR Diver Course Kevin Gurr & Phil Short Workbook Slides By: Copyright IANTD/IAND, Inc. 2000

Sentinel Rebreather Layout Copyright IANTD/IAND, Inc. 2000

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 Copyright IANTD/IAND, Inc. 2000

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. Copyright IANTD/IAND, Inc. 2000

System Layout Copyright IANTD/IAND, Inc. 2000

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. Copyright IANTD/IAND, Inc. 2000

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 Copyright IANTD/IAND, Inc. 2000

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 Copyright IANTD/IAND, Inc. 2000

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 Copyright IANTD/IAND, Inc. 2000

Sentinel Oxygen Cells Oxygen sensor with moisture tolerant membrane Removable with no special tools Moisture tolerant Robust connection system Copyright IANTD/IAND, Inc. 2000

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. Copyright IANTD/IAND, Inc. 2000

Sentinel Power On Screen Copyright IANTD/IAND, Inc. 2000

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 Copyright IANTD/IAND, Inc. 2000

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 Copyright IANTD/IAND, Inc. 2000

Sentinel Primary Dive Screens Copyright IANTD/IAND, Inc. 2000

Sentinel Rebreather HUD 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 LED Mode PO2 Mode Light Status Meaning Solid Green At Set-point Slow Flash Green Below Set-point Fast Flash Green Above Set-point Copyright IANTD/IAND, Inc. 2000

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 Copyright IANTD/IAND, Inc. 2000

The Counter lungs Necessary for free breathing Constant Buoyancy 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 Copyright IANTD/IAND, Inc. 2000

Hydrostatic Effect Chest mounted bag - diver horizontal inhale less effort exhale more effort Copyright IANTD/IAND, Inc. 2000

Hydrostatic Effect Back mounted bag - diver horizontal inhale more effort exhale less effort Copyright IANTD/IAND, Inc. 2000

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 Copyright IANTD/IAND, Inc. 2000

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 Copyright IANTD/IAND, Inc. 2000

Absorbent Canister Types Axial Cross Flow Radial Copyright IANTD/IAND, Inc. 2000

Gas flows through a block of absorbent in linear direction Axial Canister Gas flows through a block of absorbent in linear direction Copyright IANTD/IAND, Inc. 2000

Gas flows through a block of absorbent with a direction change Cross Flow Canister Gas flows through a block of absorbent with a direction change Cross Flow Copyright IANTD/IAND, Inc. 2000

Absorbent Canister Radial Flow System - gas enters center of ‘doughnut’ cross section & radiates outwards through the absorbent (or from the outside inwards). Copyright IANTD/IAND, Inc. 2000

All Absorbents will produce a caustic effect if mixed with water. 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. Copyright IANTD/IAND, Inc. 2000

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 Copyright IANTD/IAND, Inc. 2000

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 Copyright IANTD/IAND, Inc. 2000

CO2 Absorbent Duration Variables Chemical composition Canister volume Temperature Exertion level (CO2 generation) Moisture level Gas density/depth Rebreather design Copyright IANTD/IAND, Inc. 2000

CO2 Absorbent Testing The Sentinel was tested using: 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 Copyright IANTD/IAND, Inc. 2000

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 Copyright IANTD/IAND, Inc. 2000

Hypercapnia PCO2 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 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 Copyright IANTD/IAND, Inc. 2000

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 Copyright IANTD/IAND, Inc. 2000

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 Copyright IANTD/IAND, Inc. 2000

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 Pre-dive will record and abort in the logbook. Copyright IANTD/IAND, Inc. 2000

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 Copyright IANTD/IAND, Inc. 2000

Basic Dive Procedures Initial in-water verification Descent - manual diluent addition Buoyancy control Monitoring PO2 Minimum loop volume Monitoring gas supplies Ascents Copyright IANTD/IAND, Inc. 2000

Initial in-water verification at 6 m Check for leaks Verify oxygen injection is working Verify ADV is operating Adjust buoyancy Copyright IANTD/IAND, Inc. 2000

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. Copyright IANTD/IAND, Inc. 2000

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. Copyright IANTD/IAND, Inc. 2000

Sentinel PO2 Monitoring Hypoxia & Hyperoxia are real dangers in all rebreathers Frequent cross checking of Primary and Backup displays Constant PO2 Monitoring is Vital Copyright IANTD/IAND, Inc. 2000

Minimum Loop Volume 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. Copyright IANTD/IAND, Inc. 2000

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 Copyright IANTD/IAND, Inc. 2000

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 Set-point during a normal ascent due to its dynamic control algorithm Oxygen can be manually added if necessary Copyright IANTD/IAND, Inc. 2000

Failure Modes Emergency Scenarios 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 Copyright IANTD/IAND, Inc. 2000

See the training video and skills list for skill detail 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. Copyright IANTD/IAND, Inc. 2000

Sentinel CCR Skills See the training video and skills list for skill detail 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. Copyright IANTD/IAND, Inc. 2000

Sentinel CCR Skills See the training video and skills list for skill detail HUD (Head Up Display) use. Semi Closed (gas extender drill). Electronics monitoring. Gas sharing. Various multi-part training scenarios. Copyright IANTD/IAND, Inc. 2000

Rebreather Maintenance Disinfecting & cleaning CO2 seal O-rings Canister Hoses Counter lungs BCD Copyright IANTD/IAND, Inc. 2000

Testing If the unit fails the negative test and the fault is not easily recognisable. 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. Copyright IANTD/IAND, Inc. 2000

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 O-rings/counterlungs/mushroom valves O2 compatible lubricants only on HP parts silicone grease on all else Copyright IANTD/IAND, Inc. 2000

Disinfecting & Cleaning 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 Copyright IANTD/IAND, Inc. 2000

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. Copyright IANTD/IAND, Inc. 2000

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 Copyright IANTD/IAND, Inc. 2000

O-Rings 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 Copyright IANTD/IAND, Inc. 2000

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 Copyright IANTD/IAND, Inc. 2000

Counter lungs 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 Copyright IANTD/IAND, Inc. 2000

BCD Vital for buoyancy control & safety Visual inspections regularly Fully inflate and check for leaks, pre-dive Copyright IANTD/IAND, Inc. 2000

Always do all pre-dive checks Always Pre-breathe the unit 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 Copyright IANTD/IAND, Inc. 2000