Buoyancy

1. Buoyancy

2. We will cover • What is Buoyancy • Buoyancy loss and compensation • Dangers • Importance of Buoyancy control • Precautions • Summary

3. What is Buoyancy? Ability to Float • Positive Buoyancy - Rises • Negative Buoyancy - Sinks • Neutral Buoyancy - Does Neither

4. Archimedes Principle “Any object wholly or partially immersed in a liquid experiences an up-thrust (apparent loss of weight) equal to the weight of the liquid displaced”

5. Positive Diver Rises Neutral Negative Diver Sinks 3 States of Buoyancy

6. Archimedes Principle • Compare Density of object with Density of displaced liquid, to determine state of Buoyancy • Fresh Water Density = 1000kg/m3 • Sea Water Density = 1027kg/m3

7. Buoyancy Loss • Ideal state – Neutral Buoyancy • Loss of buoyancy • Positive or negative • Buoyancy compensation • Easier to manoeuvre

8. Buoyancy Loss Loss of Neutral Buoyancy • Neoprene wetsuit • Buoyancy in suit • Compresses on descent • Regained on ascent

9. Buoyancy Loss Loss of Neutral Buoyancy • Neoprene dry suit • Buoyancy in suit material • Buoyancy of air inside suit • Compresses on descent • Regained on ascent

10. Buoyancy Loss Loss of Neutral Buoyancy • Membrane dry suit • Little buoyancy in suit material • Buoyancy of air inside suit • Compresses on descent

11. Buoyancy Loss Loss of Neutral Buoyancy • Diving cylinder • Air has weight • Decreases as air is consumed during dive • Dive profile • Diving deeper or shallower after achieving neutral buoyancy

12. Dangers of Buoyancy Loss • Uncontrolled descent • Excessive negative buoyancy • Impact with bottom • Burst eardrum • Nitrogen narcosis • Rapid air consumption • O2 Toxicity if diving on EAN

13. Dangers of Buoyancy Loss • Uncontrolled Ascent • Loss of Buoyancy control or panic • Rapid response • Burst lung • Unconsciousness • Drowning • Decompression sickness

14. Buoyancy Compensation • Weight belt to counteract diving suit buoyancy • Insert air into buoyancy device • Insert air into dry suit • to prevent suit squeeze • If buoyancy is excessive • Vent air from buoyancy device • Vent air from dry suit

15. Importance of Buoyancy Control • Neutrally buoyant • Dive with ease, comfort, minimal effort • Check weight needed from dive to dive • Weight of cylinders differ • Neoprene loses buoyancy • Fresh/Sea water • Neutral buoyancy for safety stop

16. Precautions • Weight • Equipment • Location • Dry suit • Repair holes

17. Precautions • Buoyancy device • Check for leaks • Direct feed and mini cylinder fittings • Weight belt • Good condition • Secured to buckle • Fit snugly on surface • Check fit during dive

18. Precautions • Never use the Buoyancy Device as a lifting bag • All SCUBA divers must wear a Buoyancy Device

19. Procedure for Ditching of Weight Belt Always wear your weight belt the same way i.e. with the buckle opening either to the left or the right. • Ditching procedure: • Open the quick release buckle, maintaining a firm grip on the strap • Hold the belt out to one side, away from your body • Release your hold on the belt • Integrated Weights

20. Summary • What is Buoyancy • Buoyancy loss and compensation • Dangers • Importance of Buoyancy control • Precautions • Summary

21. Questions

22. What state of Buoyancy does the diver normally strive for? • Positive Buoyancy • Neutral Buoyancy • Negative Buoyancy

23. What state of Buoyancy does the diver normally strive for? • Positive Buoyancy • Neutral Buoyancy • Negative Buoyancy

24. What law of physics relates directly to buoyancy? • Dalton's Law • Boyle's Law • Archimedes Principle

25. What law of physics relates directly to buoyancy? • Dalton's Law • Boyle's Law • Archimedes Principle

26. What factors influence Buoyancy? • The diving suit • The diving cylinder • The weight belt • All of the above

27. What factors influence Buoyancy? • The diving suit • The diving cylinder • The weight belt • All of the above

28. The average neoprene wetsuit has a buoyancy of how many litres on surface: • 12 Litres • 9 Litres • 3 Litres

29. The average neoprene wetsuit has a buoyancy of how many litres on surface: • 12 Litres • 9 Litres • 3 Litres

30. Buoyancy loss is normally compensated for by: • Inflating the buoyancy device • Dropping weight belt • Holding your breath

31. Buoyancy loss is normally compensated for by: • Inflating the buoyancy device • Dropping weight belt • Holding your breath

32. By how much does a 12 litre cylinder weigh extra when filled to 200 Bar? • 7 Kilograms • 5 Kilograms • 3 Kilograms

33. By how much does a 12 litre cylinder weigh extra when filled to 200 Bar? • 7 Kilograms • 5 Kilograms • 3 Kilograms

34. Dangers of buoyancy loss can lead to: • Impact with bottom • Burst eardrum • Nitrogen Narcosis • All of the above

35. Dangers of buoyancy loss can lead to: • Impact with bottom • Burst eardrum • Nitrogen Narcosis • All of the above

36. A dive in freshwater will cause us to: • Reduce the amount of lead on our weight belts • Increase the amount of lead on out weight belts • Use the same weight as used in a sea dive

37. A dive in freshwater will cause us to: • Reduce the amount of lead on our weight belts • Increase the amount of lead on out weight belts • Use the same weight as used in a sea dive

38. Too much buoyancy on ascent can lead to: • A rapid, uncontrolled ascent leading to burst lung • A rapid, uncontrolled ascent leading to Nitrogen Narcosis • A comfortable dive ending

39. Too much buoyancy on ascent can lead to: • A rapid, uncontrolled ascent leading to burst lung • A rapid, uncontrolled ascent leading to Nitrogen Narcosis • A comfortable dive ending

40. Is the importance of buoyancy control necessary to? • Complete a dive with ease, comfort and minimal physical effort • Make the dive more exciting • Look as if you know what you are about

41. Is the importance of buoyancy control necessary to? • Complete a dive with ease, comfort and minimal physical effort • Make the dive more exciting • Look as if you know what you are about