BSAC Rebreather Diving

BSAC Rebreather Diving

Rebreather Rebreather FundamentalsFundamentals

Rebreather Rebreather FundamentalsFundamentals

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

0 3 6 9 12 15 18 21 24 27 30 33 36 39 42 45 48 51

0

20

40

60

80

100

120

140

160Consumption

rate (l/m)

Depth (m)

CC

SCR

OC (25)

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


Rebreather Fundamentals PO2 Advantage

0 3 6 9 12 15 18 21 24 27 30 33 36 39 42 45

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

1.60PO2

Depth (m)

OC

SCR

CC

Inspiration Maximises PO2

SCR as per Nitrox


Rebreather Fundamentals Decompression limits

Longer decompression no stop limits

12 15 18 21 24 27 30 33 36 39 42 45

0

50

100

150

200No stop time (mins)

Depth (m)

Air

Nitrox

PO2



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

Rebreathers in Practice


Rebreather Fundamentals Simple Rebreather

Counterlung

OxygenScrubber

Dump Valve

Breathing Loop


Rebreather Fundamentals Simple Rebreather

Simple RebreatherSimple RebreatherSimple RebreatherSimple Rebreather

Semi-closed Semi-closed Circuit RebreatherCircuit Rebreather

Semi-closed Semi-closed Circuit RebreatherCircuit Rebreather

Closed Circuit Closed Circuit RebreatherRebreather

Closed Circuit Closed Circuit RebreatherRebreather

Difference is in the way that the addition of oxygen is effected


Rebreather Fundamentals Semi-Closed Rebreather

Nitrox

Metering flow orifice (jet)

Bypass

Vent Valve

Off-board Bail–out

On-board Bail-out?


Rebreather Fundamentals Closed Circuit Rebreather

OxygenDiluent

Handsets

Buzzer

Oxygen sensors

(3)

Oxygen inject valve

On-board

bail-out

OptionalAuto

Demand Valve



Definition: Pressure imbalance between the

counterlungs and diver’s lungs in different body positions

Counterlung position higher

Compromise is over the shoulder! Example, APD Inspiration

Easier to exhale Harder to inhale, e.g., Dräger Dolphin

Easier to inhale Harder to exhale

Counterlung position lower

Static Lung Loading



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

Buddying a Rebreather Diver



GasGaugeGag

Post entry & bubble checks

Swim around not

over

Vent loop

Buoyancy Buoyancy

Unit shut down

Monitor Gas

Supply & FO2

SCR Rebreather Diving



Start-up& function checks

Post entry & bubble checks

Set point change

Add diluent

Swim around not

over

Vent loop

Buoyancy Buoyancy

Set point change

Unit shut down

Monitor handsets

CCR Rebreather Diving


Rebreather Fundamentals What if………

If in doubt… Close mouthpiece then Bail-out!

Something goes wrong with the unit……


Rebreather Fundamentals Summary

Why Dive a Rebreather?

Simple rebreather Semi-Closed Rebreather Closed Circuit

RebreatherBuddying

What If…


Rebreather Fundamentals Questions?

BSAC Rebreather Diving

Documents

Transcript of BSAC Rebreather Diving