DECOMPRESSION THEORY

 

HISTORY : J.S. HALDEAN discover it in the 1900s

 

 

Henry’s law is applied to this theory (gas absorption)

 

Theoretical tissues :  tissue of the body (bones, blood, liver, heart, fat, lungs, etc…)

 

Half-live / half time : the time that a tissue absorb N2 until it’s half full

 

M-value : maximum amount of N2 in one tissue

 

 

Haldean works with 5 theoretical tissues and the biggest tissue is 75’

US. Navy table (SSI) with 7 theoretical tissues and the biggest tissue is 120’

Padi Tables with 14 theoretical tissues and the biggest tissue is 60’

 

The US Navy table have been tune-up with Doppler machine to count the silent bubbles in the body after a dive

 

The Doppler limit (or NDL) is the maximum time that we can stay underwater until the inside PPN2 equal the outside PPN2

 

Exemple:

 

            Meters             pressure in bar            percentage                  partial pressure

 

                                                                        21%02                                     0.21ppo2

            0                                  1                      +79&N2                                  +0.79ppn2

                                                                        ---------                                                ------------

                                                                        100%                                       1 bar

 

                                                                        21%o2                                     0.42ppo2

            10                                2                      79%n2                                     1.58ppn2

                                                                        ---------                                                ------------

                                                                        100%                                       2 bar

 

The NDL at 10m is 160 minutes , so after this amount of time, the body is saturated with N2 and we need to ascent otherwise we pass in decompression dive

 

 

DIVE COMPUTERS:

 

Dive computers gives more time underwater because they recalculate the NDL all the time

But on the 1^st dive, dive computer and dive table give the same amount for a given depth.

 

The same roles apply to dive computers and tables:

 

1. never share a computer
2. never plan to the NDL time
3. ascent max 9m/ minute
4. if computer fail during a dive, ascent to 5m and stay there as long as your air supply permit and don’t dive for 24hours
5. safety stop at 5m for min 3 minutes
6. always begin with the deepest dive and work shallower
7. don’t do up down up down dives
8. adjust if you dive in altitude (more that 300m)
9. wait 18-24 hours after a dive to ascent in altitude (more than 300m) or before taking a pressurized plane
10. 24 hours if taking non pressurized plane or ascending higher than 2’400m altitude

 

Computers allow multilevel diving.

 

ALTITUDE DIVING

 

1. Diving in altitude (more than 300m ) required special procedures since the atmospheric pressure is less than at the sea level and we dive in fresh water
2. when diving in altitude, you need to know your altitude to convert the real depth to theoretical depth, the capillary gauge do it automatically
3. at 5.500m the atmospheric pressure is ½ so 0.5 bar

 

THE TOTAL DIVING SYSTEM (EQUIPMENT)

 

 

1950 is consider to be the genesis age of the sport

 

Today, the equipment need :

 

1. simplicity
2. consistency
3. adaptability
4. reliability
5. redundancy

 

CYLINDERS:

 

2 METAL: STEEL  3aa MARKING AND ALUMINUM 3al MARKING

 

Steel:

• have tinner walls
• can hold more pressure if made for it
• have less impact on buoyancy
• but they rust in humid condition
• AA+ mean that it can be overfill by 10%

 

Aluminum:

• have ticker walls
• have more impact on buoyancy
• don’t rust

 

 

Valves:

• DIN (deutsche industry norm) regulator screw into the valve, can hold more pressure, for warm or cold water diving
• INT or YORK are use in warm water, simple on of valve
• J , was used when no pressure gauges existed , still in use today, to fill up , the valve need to be in down position

 

Inside the valve is the BURST DISK, if the cylinder is accidentally overfilled, the burst disk break a 160% of the cylinder working pressure. It needs to be changed annually during visual inspection due to metal fatigue

 

• Never empty completely the cylinder to be sure that no contaminants can enter it

 

 

TYPICAL MARKING:

 

VISUAL INSPECTION:

• Every year
• Check for outside for cracks
• Check the inside for contaminants
• Do valve service
• Change the burst disk

 

HDROSTATIC TEST

• EVERY 3 YEARS IN INDONESIA DIFFERENT IN EVERY COUNTRY CHECK THE LAW
• The cylinder is measured and place in water, filled with water and fill up to 5/3 of it’s working pressure (207/3*5)
• The pressure is release and the cylinder is measured again. If there is any difference, the cylinder cannot be use.

 

NITROX CYLNDERS

 

• The cylinder with nitrox content need to be clearly marked, to be sure that no other divers than the user will use them
• The cylinder need to be O2 clean to not explode when filled with pure O2 or O2 more than 40%
• They need to have MOD maximum operating depth
• They need to have the O2 clean service sticker
• They need to have the name of the diver
• They need to have the % from the Gas blender and the analyze from the diver

 

1^ST STAGE REGULATOR

 

4 DIFFERENT KINDS:

1.     PISTON, UNBALANCED

2.     PISTON , BALANCED

3.     DIAPHRAGM, UNBALANCED

4.     DIAPHRAGM, BALANCED

 

·       The piston reduce maintenance

·       Simpler mechanism with less part moving

 

·       The diaphragm is for environmental sealing(ice or dirty water diving)

 

·       Unbalanced means that it is more difficult to get air from the cylinder when low air, 2 divers breath on the same cylinder or deeper depth. Etc…

 

·       Balanced regulator give the same air flow even if low air , if 2 divers breath on the same cylinder or if deeper depth

 

DOWNSTEAM VALVES :

• The air flow within the same opening direction of the valve (going down river) with the river flow
• We find downstream valve in the 1^st and 2^nd stage to be sure that if something break, the air doesn’t stop ( FAIL SAFE SYSTEM)

 

UPSTREAM VALVES:

 

• The air flow against the opening of the valve (going up river) against the flow.
• We find upstream valves in BCD inflator, so if the valve break the air cannot continue to inflate

 

The job of the 1^st stage is to reduce from high pressure (cylinder) to intermediate constant pressure (around 10 bar) for the 2^nd stage who delivers air at ambient pressure.

 

DEPTH GAUGES:

 

• The capillary gauge is the most simple. It is a tube filled with air who compress when depth increases. It works with boyle’s law and it gives you the theoretical depth when diving in altitude. A B C

 

• The bourbon tube works with tube that bent in a coil which uncoiled when depth increases. This gauge is very accurate but need to be adjusted when diving in altitude. The gauge is filled with oil for longer durability

 

• The diaphragm gauge works the same way as the bourbon gauge, but the pressure change is transfer to the needle by the bent of the diaphragm. Be careful to not puncture the back of the diaphragm when opening

 

• The sealed is the most accurate depth gauge

 

COMPUTERS

 

• DIFFERENT ALGORITHM  (SPENCER WASHOUT, EE WASHOUT, BUHLMAN EE WASHOUT.)
• THEY MUST HAVE NITROX COMPABILITY OR JUST NITROX WHO CAN BE SET TO 21% NITROX WHO IS AIRJ
• CAN BE MULTI GAS DIVING FOR TECH DIVERS
• FREEDIVING MODE FOR FREEDIVER
• GAUGE MODE FOR CANCELING NITROGEN ABSORBTION
• HOSELESS CONNECTION TO ATTACHED TO YOU 1^ST STAGE

 

 

WET AND DRY SUITS

 

• WET SUIT CAN BE USE FOR WATER MORE THAN 16C
• Wetsuits works by letting water entering in the  suit an warm the water who cannot escape from the suit keeping the diver warm

 

• Dry suit are use for less than 16C
• Dry suit works by inflating the inside with ARGON who have double or twice the isolation than air. The body warm the argon and keep the diver warm.

 

KNIFES

 

• You must have a knife when you dive.
• Good for cutting fishing lines
• Good for hitting the cylinder to attract other attentions

 

 

SMB Surface marker buoy

 

• This is the cheapest item to buy and take with you. It can save your live if you are lost.

 

SLATES

• Slates are very helpful for complicate underwater communications
• Write on it with pencil and clear it with toothpaste.

 

REPAIR LIMITATION

• The best repair philosophy is prevention
• Never repair a 1^st or 2^nd stage is you are not authorize technician

 

 

SAVE-A-DIVE-KIT

• As a professional, you need to take with you some spare part when you go diving and need:
• Allen keys
• Dust cap
• Silicon
• Fin and mask strap
• Needle to open o rings
• O rind with various sizes
• A full regulator 1^st and 2^nd stage
• More weight
• More weight belt
• Screw driver
• Mask
• Fins

 Scuba Diving Physic

PHYSIC

 

 

PRESSURE IN SALT WATER

 

• AT 20M THE PRESSURE IS 3 BAR

 

FORMULA:

 

20M /     10                 +1                     = 3BAR

            SW      ATM PRESSURE

 

 

PRESSURE IN FRESH WATER

 

• AT 20M THE PRESSURE IS 2.94BAR

 

FORMULA

 

20M /   10.3                +1                    =2.94 BAR

            FW      ATM PRESSURE

 

 

GAUGE PRESSURE VS TOTAL/AMBIENT PRESSURE

 

• THE GAUGE PRESSURE IS THE AMBIENT PRESSURE WITHOUT THE SURFACE PRESSURE

 

FORMULA GAUGE PRESSURE

 

20M  / 10        = 2BAR

            SW

 

20M / 10.3      = 1.94BAR

            FW

 

• THE TOTAL OR AMBIENT PRESSURE IS THE SAME, WE COUNT THE PRESSURE FROM THE SURFACE

 

FORMULA

 

20M / 10         +1                                            = 3BAR

            SW      SURFACE PRESSURE

 

20M / 10.3      +1                                            = 2.94 BAR

            FW      SURFACE PRESSURE

 

TEMPERATURE CHANGES ( CHARLES’ LAW)

 

• IF TEMPERATURE INCREASE, THE PRESSURE INCREASE
• IF TEMPERATURE DECREASE, THE PRESSURE DECREASE
• THE PRESSURE INCREASE OR DECREASE FROM 0.6 BAR PER DEGRES

 

FORMULA

 

FILL TANK TO 200BAR TEMPERATURE OF THE TANK IS 40C WHEN FULL

THE NEXT MORNING THE TANK TEMPERATURE IS 30C

 

CALCULATON:

 

40C – 30C = 10C

 

10C X 0.6 = 6 BAR

 

200BAR – 6 BAR = 194 BAR

 

 

AIR COMSUPTION

 

• THE DEEPER YOU GO THE MORE AIR YOU USE
• SHE SHALLOWER YOU YO THE LESS AIR YOU USE

 

FORMULA

 

PUT ON PAPER LIKE THIS:

1. CHANGE THE METERS TO BAR (BE CAREFULL IF FRESH OR SALT WATER)
2. BRING YOUR COMSUPTION TO THE SURFACE ( LESS SO DIVIDE)
3. BRING YOUR COMSUPTION DOWN (MORE SO TIME)
4. FINISH
5. ALWAYS BRING IT TO THE SURFACE 1^ST

 

 

 

 

VOLUME CHANGES (BOYLE’S LAW)

 

• IF THE PRESSURE INCREASE, THE VOLUME DECREASE
• IF THE PRESSURE DECREASE, THE VOLUME INCREASE

 

FORMULA:

 

PUT ON PAPER LIKE THIS:

1. CHANGE THE METERS IN BAR (BE CAREFULL OF FRESH OR SALT WATER)
2. BRING YOUR VOLUME TO THE SURFACE ( MORE SO TIME)
3. BRING YOUR VOLUME DOWN ( LESS SO DIVIDE)
4. FINISH
5. ALWAYS BRING TO THE SURFACE 1^ST

 

FRESH WATER:

ANSWER

WEIGHT OF WATER

 

• 1LT OF FRESH WATER WEIGHTS 1.0 KG
• 1LT OF SALT WATER WEIGHTS 1.03 KG

 

FORMULA

 

10LT FW X 1 = 1KG

10LT SW X 1.03 = 1.03KG

 

ARCHIMEDE’S PRINCIPLE

 

• IF YOU PLACE AN OBJECT IN THE WATER, THIS OBJECT WILL DISPLACE WATER.

1. IF THE WEIGHT OF THE WATER DISPLACED IS LESS THAN THE WEIGHT OF THE OBJECT, THE OBJECT WILL SINK (COIN IN WATER)
2. IF THE WEIGHT OF THE WATER DISPLACED IS MORE THE THE WEIGHT OF THE OBJECT, THE OBJECT WILL FLOAT
3. IF THE WEIGHT OF THE WATER DISPLACES IS THE SAME WEIGHT AS THE OBJECT, THE OBJECT WILL BE NEUTRAL

 

• BE CAREFULL IF THE OBJECT IS IN FRESH OR SALT WATER
• YOU NEED TO KNOW: THE WEIGHT OF THE OBJECT (KG), THE VOLUME OF WATER DISPLACED (LT) AND IF IN FRESH OR SALT WATER
• IF YOU DON’T HAVE THESE NUMBERS, YOU CANNOT CALCULATE!!!

 

 

FORMULA:

• ALWAYS PUT ON PAPER AND WRITE IF KG OR LITERS
• YOU CANNOT DIVIDE KG BY LT
1. CHANGE THE WATER(LT) IN KG
2. MINUS YOUR RESULT TO THE WEIGHT OF THE OBJECT
3. IF YOU FIND – IN FRONT OF THE NUMBER, THE OBJECT SINK(NEGATIVE BUOYANCY)
4. TO FIND HOW MUCH AIR YOU NEED TO ADD IN LIFTING BAG, CHANGE THE KG IN LITER AGAIN AND YOU GET YOUR ANSWER
5. BE AWARE OF FRESH OR SALT WATER

 

ANSWER:

PARTIAL PRESSURE ( DALTON’S LAW)

 

• IN A MIXTURE OF GASES, THE TOTAL PRESSURE OF THE MIXTURE IS EQUAL TO THE SUM OF THE 2 GASES

 

FORMULA:

 

IN AIR WE HAVE O2 AND N2 OR SOME OTHER GASES WHO ARE TO SMALL TO BE COUNTED

 

O2 AROUND 21%

N2 AROUND 79%

 

AT THE SURFACE , THE PRESSURE IS 1 BAR

 

THE TOTAL OF O2 AND N2 HASE TO BE EQUAL TO 1

 

TO FIND THE PARTIAL PRESSURE, DIVIDE THE % BY 100

 

SURFACE WITH AIR 1 BAR TOTAL PRESSURE

 

EXEMPLE:        21% 02 / 100 =  0.21 PPO2

                        +79% N2/ 100 = +0.79 PPN2

                        -------               -------------

TOTAL           100%                1 BAR

 

 

 

10M WITH AIR SW 2 BAR TOTAL PRESSURE

 

EXEMPLE:        21% 02 / 100 =  0.21 PPO2 X2 =    0.42 PP02

                        +79% N2/ 100 = +0.79 PPN2 X2 = +1.58 PP02

                        -------               -------------                ------------

TOTAL           100%                1 BAR                        2BAR

 

• WHY WE NEED TO KNOW THE PARTIAL PRESSURE
• O2 IS TOXIC AT 1.4 PPO2 à CONVULTIONS
• N2 IS TOXIC AT 2.23PPN2 (18.3M) à NITROGEN NARCOSIS

 

 

HOW TO CALCULATE THE MAX DEPTH WITH PPO2:

 

MAX DEPTH =  14                            EMERGENCY DEPTH                     16

                            ----    -10                 CONTENGENCY DEPTH                ---    - 10

                            FO2                                                                                     FO2

 

EXEMPLE:    DIVING WITH AIR 21%O2

 

                        14                                                                                16

                        ---        -10 = 56.6M                                                    ---   -10 = 66.19M                          0.21                                                                             0.21

 

EXEMPLE: DIVING WITH NITROX 32%

 

14                                                                                16

                        ---        -10 = 33.75M                                                  ---   -10 = 40M                               0.32                                                                             0.32

 

 

 

 

 

 

 

 

 

 

 

 

HENRY’S LAW

 

• HENRY’S LAW STATE THAT WE ABSORB NITROGEN TO TRY TO EQUILIZE THE AMBIENT PRESSURE WITH OUR INSIDE BODY PRESSURE
• THE DEEPER WE GO THE MORE DENSE THE AIR IS SO WE ABSORB NITROGEN FASTER
• WE ABSORB NITROGEN UNTIL OUR BODY IS SATURATED WITH N2 (NON DECOMPRESSION LIMIT)
• WHEN WE COME UP TO THE SURFACE, OUR N2 PRESSURE INSIDE OUR BODY IS HIGHER THEN THE AMBIENT PRESSURE SO WE RELEASE N2
• WE ABSORB N2 MUCH FASTER THEN WE RELEASE IT.

 

 

LIGHT

 

• LIGHT IS REFLECTED ON THE SURFACE OF THE WATER
• THAN IT IS DIFFUSE AND ABSORB IN THE WATER
• BECAUSE OF THAT, WE LOOSE COLORS
• 1^ST IS RED, THAN ORANGE, THAN YELLOW, THAN GREEN, THAN BLUE
• OUR BLOOD AT 3M IS GREEN AND DARK BROWN AT 10M
• WE NEED LIGHT OF FLASHES TO SEE THE REAL COLOR UNDERWATER

 

LIGHT à REFRACTION

 

• UNDERWATER, OBJECTS LOOKS BIGGER BY 33% AND CLOSER BY 25%
• THIS IS CAUSE BY WATER AND LIGHT WHO TRAVEL SLOWER IN THE WATER.

 

LIGHT à TURBIDITY

 

• TURBIDITY CAUSES OBJECT TO LOOK FARTHER AWAY THAN THEY REALLY ARE.

 

SOUND

 

• SOUND TRAVEL ABOUT 4X FASTER IN THE WATER
• IT IS DIFFICULT TO KNOW WHERE THE SOUND COME FROM
• OUR BRAIN THINK THAT THE SOUND COME FROM OVERHEAD BECAUSE THE SOUND ARRIVES IN BOTH EARS AT THE SAME TIME

 

HEAT

 

• WE LOOSE HEAT 25X FASTER IN WATER
• THE BIGGEST LOOSE IS BY CONDUCTION( THE WATER TOUCH THE SKIN AND DICIPATE THE HEAT)
• USE A WETSUIT TO PROTECT AGAINST IT.
• 75% OF THIS HEAT GOES AWAY BY THE HEAD, SO IF YOU FEEL COLD PUT A HOOD.