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OPEN WATER DIVE TRAINING ADVANCED

OPEN WATER DIVE TRAINING ADVANCED. DIVING PHYSICS. STAN JACKSON UICC 5303. REVIEW. Sound travels about 5000 feet per second in salt water or about four times faster in water than air. Underwater, objects appear 25% closer and 33% larger.

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OPEN WATER DIVE TRAINING ADVANCED

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  1. OPEN WATER DIVE TRAININGADVANCED DIVING PHYSICS STAN JACKSON UICC 5303

  2. REVIEW • Sound travels about 5000 feet per second in salt water or about four times faster in water than air. • Underwater, objects appear 25% closer and 33% larger. • Water conducts heat more than 20 times faster than air. • Atmosphere or Air At sea level, atmospheric pressure is equal to 14.7 psi. or one atmosphere (ATA) or (ATMA). Air contains 21% Oxygen, 78% Nitrogen and 1% other gasses.

  3. PRESSURE • Atmospheric – The pressure exerted by the earth’s atmosphere. (14.7 psi) 18,000 feet = 7.35 psi • Hydrostatic – Pressure due to the weight of water. .445 psi per foot of seawater or 14.7 psi per 33 feet. .432 psi per foot of freshwater or 14.7 psi per 34 feet. • Absolute Pressure – The sum of atmospheric and hydrostatic pressure. (ATA or ATMA) • Gauge Pressure – The difference between atmospheric pressure and the pressure being measured.

  4. PRESSURE • Hydrostatic Pressure – How did we get .445 psi per foot of seawater and .432 psi per foot of freshwater? • What is the absolute pressure at 62 fsw? • What is the absolute pressure at 112 ffw? .445 psi x 62 fsw = 27.59 psi + 14.7 psi = 42.29 psia .432 psi x 112 fsw = 48.38 psi + 14.7 psi = 63.08 psia

  5. PRESSURE • Hydrostatic Atmospheres (working with) • What is the absolute pressure (ATA) at 62 fsw? • What is the absolute pressure (ATA) at 112 ffw? 2.88 ATA 4.29 ATA

  6. Gas Gas Depth Pressure Volume Density PRESSURE CHART Sea Level 14.7 psia 1 ata 1 cu ft 1x 33 feet 29.4 psia 2 ata 1/2 cu. ft. 2x 66 feet 44.1 psia 3 ata 1/3 cu. ft. 3x 99 feet 58.8 psia 4 ata 1/4 cu. ft. 4x 132 feet 73.5 psia 5 ata 1/5 cu. ft. 5x 165 feet 88.2 psia 6 ata 1/6 cu. ft. 6x

  7. DENSITY • Density – weight per unit volume. (pounds per cubic foot) - Density = Weight / Volume or D = W / V • Seawater – one cubic foot equals 64 lbs. (fsw) • Freshwater – one cubic foot equals 62.4 lbs. (ffw) • Density (Gas) – is related to absolute pressure. As depth increases, the density of the breathing gas increases and becomes heavier per unit volume.

  8. DENSITY • Density – weight per unit volume. • D = W / V Multiply both sides by volume Divide both sides by density D = Density of water W = Total weight of diver V = Water displaced (volume)

  9. DENSITY • If we have a diver in saltwater and he wants to dive in freshwater, how much weight will he need to remove? • First we need to know the volume of the diver in saltwater. Total weight of diver. Density of saltwater. Now we know the volume of the diver. Next we can find out how much freshwater he will displace. W = V x D 3.875 cu. ft. x 62.4 lbs. = 241.8 lbs. 248 lbs. – 241.8 lbs. = 6.2 lbs. Remove! 180 lbs. Diver 50 lbs. Equipment 18 lbs. Weight belt 248 lbs. Total weight

  10. DENSITY • A dive team wants to recover (lift) a 432 pound (dry weight) anchor from the bottom of the ocean. The anchor displaces 3.5 cu. ft. of sea water. The bottom is flat and firm. How many 50 pound lift bags will it take to recover (lift) the anchor to the surface? W = V x D 3.5 cu. ft. x 64 lbs. = 224 lbs. 224 lbs. - 432 = 208 ÷ 50 = 4.16 bags

  11. TEMPERATURE • Temperatures must be converted to absolute when the gas laws are used. • Rankine – Based on Fahrenheit scale. R = F + 460 • Kelvin – Based on Celsius scale. K = C + 273 • F = (9/5 x C) + 32 • C = 5/9 x (F – 32)

  12. GAS LAWS • Boyle’s Law of Pressure and Volume – If the temperature is kept constant, the volume of a gas will vary Inversely with the absolute pressure. A sealed flexible container at the surface has a volume of 10 liters. The container is submerged to a depth of 79 feet in the ocean. What is the volume of the container at 79 fsw? Divide both sides by

  13. GAS LAWS • Boyle’s Law of Pressure and Volume – If the temperature is kept constant, the volume of a gas will vary Inversely with the absolute pressure. A sealed flexible container at the surface has a volume of 10 liters. The container is submerged to a depth of 79 feet in the ocean. What is the volume of the container at 79 fsw?

  14. Ratio or Percentage • If a cylinder contains 80 cu. ft. of air at 3000 psig, how many cubic feet of air remains if the cylinder pressure is reduced to 2200 psig? (temperature remains constant) • Percentage

  15. GAS LAWS • Charles Law of Temperature and Volume – If the pressure is kept constant, the volume of the gas will vary directly with the absolute temperature. • If a balloon at the surface has 12 cu. ft. of air at 86ºF, what would the balloons volume be at 55°F? • First determine absolute temperatures. = 86°F + 460° = 546°R = 55°F + 460° = 515°R

  16. GAS LAWS • Gay-Lussac’s Law of Pressure and Temperature – With a constant volume, the pressure of a gas will vary directly with the absolute temperature. • A scuba cylinder contains 3000 psi. at 64°F. It is left on the boat deck, on a hot summer day. What will the cylinder pressure be if the temperature of the air inside reaches 102°F? = 64°F + 460° = 524°R = 3000 psi. + 14.7 psi. =102°F + 460° = 562°R = 3014.7 psia.

  17. GAS LAWS • Dalton’s Law of Partial Pressures – The total pressure exerted by a mixture of gases is equal to the sum of the pressures of each of the different gases making up the mixture. • The partial pressure of oxygen in air at a depth of 128 fsw is: • Henry’s Law of Dissolved Gases –The amount of any given gas that will dissolve in a liquid at a given temperature is proportional to the partial pressure of that gas.

  18. GAS LAWS • General Gas Law or Ideal Gas Law – is a combination of Boyles and Charles Law. An open diving bell of 24 cu. ft. capacity is lowered to 99 fsw. Surface temperature is 80°F and the depth temperature is 45°F. What is the volume in the bell at depth? • The volume was reduced, due to the drop in temperature and the increase in outside pressure.

  19. GAS LAWS • Archimedes Principle of Buoyancy – Any object wholly or partly immersed in a fluid is buoyed up by a force equal to the weight of the fluid displaced by the object. • You have an object that weighs 300 lbs. and displaces 4.5 cubic feet of saltwater. Will the object float or sink? 300 lbs. W = D x V 64 lbs. x 4.5 cu. ft. = 288 lbs. 12 lbs. (sink)

  20. SURFACE AIR CONSUMPTION • SAC Rate – At the surface, note the beginning pressure on your gauge. Swim at the surface for 10 minutes (moderate work load) then note your ending pressure. • Aluminum 80 @ 3000 psi Start 3000 psi – ending 2500 psi = 500 psi used. 500 psi ÷ 10 minutes = 50 psi per minute, at the surface. 50 psi per minute x ata= Depth Air Consumption. • Problem: A diver has a SAC of 40 psi per minute. The diver wants to know how long their air will last at a depth of 62 feet in sea water. Assume aluminum 80 @ 3000 psi.

  21. SURFACE AIR CONSUMPTION First – Assume, Aluminum 80 @ 3000 psi. 3000 psi – 500 psi (reserve) = 2500 psi. 2500 psi ÷ 40 psi = 62.5 minutes at the surface. ata= (SACR) 40 psi x (Depth in ata) 2.88 ata= DACR DACR = 40 psi x 2.88 ata= 115.2 psi per minute. 2500 psi ÷ 115.2 psi = 21.7 minutes at depth.

  22. KEY POINTS • Sound travels 4 times faster in water. • Objects appear 25% closer and 33% larger underwater. • Atmospheric Pressure – Air column. • Hydrostatic Pressure – Water. • Absolute Pressure – Atmospheric plus Hydrostatic. • Gauge Pressure – minus Atmospheric Pressure. • Density – weight per unit volume. • Fahrenheit to Rankine + 460° = R • Boyle’s Law of Pressure and Volume. • Charles Law of Temperature and Volume. • Gay-Lussac’s Law of Pressure and Temperature. • Dalton's Law of Partial Pressures.

  23. KEY POINTS • Henry’s Law of Dissolved Gases. • General Gas Law or Ideal Gas Law. • Archimedes Principle of Buoyancy. • Surface Air Consumption, in psi per minute.

  24. QUIZ 4 faster • Sound travels _____ times ______ in water than in air. 2. Objects appear _____% closer and _____% larger underwater. 3. What is the atmospheric pressure at sea level? 14.7 psi. • What is absolute pressure? __________ + __________ = Atma • Density is defined as _________ per unit volume. • One cubic foot of fresh water is equal to ______ lbs. ffw. • If a diver descends to 92 feet in seawater what is their absolute pressure? _________________________ 25 33 Atmospheric Hydrostatic Weight 62.4 55.64 psi or 3.79 ata

  25. QUIZ • A diver has a SAC Rate of 30 psi. per minute. How long will their air last at 72 feet in seawater? (show all work). First – Assume, Aluminum 80 @ 3000 psi. 3000 psi – 500 psi (reserve) = 2500 psi. 2500 psi ÷ 30 psi = 83.33 minutes at the surface. Atma = (SACR) 30 psi x (Depth in Atma) 3.18 Atma = DACR DACR = 30 psi x 3.18 Atma = 95.4 psi per minute. 2500 psi ÷ 95.4 psi = 26.2 minutes at depth.

  26. OPEN WATER DIVE TRAINING LBFD Stan Jackson UICC 5303

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