Principle and Practice of Basic SCUBA Diving By Dr. Yusheng M. Huang.

Principle and Practice of Basic SCUBA Diving

By Dr. Yusheng M. Huang

Introduction

• Scuba diving is the most unique adventure sport on earth.

• Swimming with marine creatures such as fishes, sea turtles, whales, or manta rays, etc…

• Underwater photography (e.g. pictures and video)• History beneath the surface: treasure hunting,

underwater archeology.• More than 70% of the earth surface is covered by water.• Different and diverse experience: shipwreck, tropical

reef, kelp forest, rocky coast, and polar ice diving.

• The requirements of being a basic scuba diver:- Good health- Proper equipments- Solid training

• What is SCUBA diving?

“Self Contained Underwater Breathing Apparatus”

You scuba dive with a compressed air cylinder or tank that you wear on your back.

Cylinder (HP) 1st Regulator (LP) 2nd Regulator (surrounding pressure)

• What is scuba certification?- No laws governing recreational scuba diving in most

countries.- You must meet these standards to receive a certification

card (C card; recreational).- Once you have completed the course and your open

water certification dives, you will be qualified to dive in conditions similar to those in which you did your open water certification dives.

- What can you do with the C card? Renting a cylinder, enjoying a day of diving on a dive boat…

• What is NAUI?- National Association of Underwater Instructor

- Courses: Basic Scuba Diver, Advanced Scuba Diver, Master Scuba Diver

- Specialty Courses: Rescue diving, Wreck diving, Deep diving, Underwater photography and video, Ice diving, Cavern and cave diving, Underwater hunting and collecting, Night diving, Technical diving….

- Instruction Courses: Assistant Instructor, Instructor, Course Director

• What are the risks of SCUBA?- Scuba diving , as a sport, has some risk and you must

understand this before you become a diver.- Energy consuming: especially in cold water, strong

currents, or make beach entries through surf…- Being injured or killed- As a diver, you must be willing to accept this risk and

take responsibility for your own actions.- A little apprehension is normal.- Misconceptions about diving: How long can I stay in the

water? How do I monitor my air pressure? (submersible pressure gauge (SPG))

- Most divers carry either an additional regulator or a totally independent backup air supply.

• What are your obligations?- Attendance: you have obligation to attend, participate in,

and satisfactorily complete every classroom and water session.

- Health: physically and mentally

Have a sound heart and healthy lungs.

Have clear ears and sinuses

Be free of any limiting disease or serious ailment.

Be free of any condition that can cause unconsciousness.

DO NOT DIVE!!: asthma, diabetes, epilepsy, pregnancy,…

- Fitness: is the ability to meet the physical demands of a particular activity.

- Use of Drugs and Alcohol

Substances such as alcohol, marijuana, and cocaine, which alter your physiology and affect your ability to think clearly, should never be used before diving.

Complete your treatment before diving.

If you are ill and do not feel well enough to dive without taking a drug, you should not dive, even if you feel fine with medication. The effects of drugs can be changed by pressure in unpredictable ways.

Ch – 2 Diving Equipment

• Basic personal equipment: Mask, fins, snorkel, wetsuit, boots, and weight belt.

• Scuba Diving Equipment:- Cylinders- Regulators- Buoyancy Compensator (BC)- Accessory Equipment

Cylinders

• Scuba cylinders (bottles or tanks) allow you to store large amounts of air in a small space.

• The air in a scuba cylinder is highly compressed. (120 to 310 bar; 1 bar = 1 atm = 14.7 psi (pounds per square inch))

• Cylinders are made of aluminum or steel- Aluminum: do not rust, easily damaged- Steel: rust, but more resistant to exterior damage• Sizes: from 10 – 18 liters cylinder or 63 – 95 cubic feet

• Markings:

Regulatory Agency

Type

Working Pressure

Serial Number

Manufacturer Test date

Test dateSize

• Accessories: boot, plastic net, etc…

• Valves: “K” valves, “J” valves, “DIN” valves- K: most popular, working pressure about 200 bar, O-ring

between the regulator and valve.- J: were popular before SPGs.- DIN: originated in Europe, working pressure more than

200 bar- Safety design: burst disks- Maintenance: visual inspection and hydrostatic testing- Storage: you should store cylinders for any long term

with some pressure in the cylinder. ** Never leave a cylinder standing by itself when you are not holding it.**

Regulators

• The scuba regulator is a mechanical device that delivers air to you on demand. One function of the regulator is to reduce the high pressure of the air in the cylinder to the ambient pressure, or the pressure surrounding your body, so you can breathe it.

• Parts: First stage, second stage, additional regulator second stages, gauges, computers.

• First Stage: - in the first stage, the high-pressure air from the cylinder

is reduced to approximately 10 bar (150 psi) above the pressure surrounding the cylinder.

- Number of outlets or ports to which hoses and pieces of equipment are attached.

High Pressure outlet/port: connect to SPG

Low Pressure outlet/port: A power-inflator hose for BC, an alternate second stage or octopus regulator, a dry suit power-inflator hose (if used)

• Second Stage- The second stage has a mouthpiece- Further reduce the air pressure from about 10 bar to

whatever the ambient pressure is.- Flow/breath resistance- If you plan to learn to do deep, wreck, cave , or ice diving

or do underwater hunting, you will want a high-performance regulator.

- Alternate air sources: Octopus regulators, Air-2 (a combination regulator and power-inflator for the BC), contingency Scuba (totally independent regulator and air supply) – 1. pony bottle 2. smaller cylinder with regulators

• Gauges: Divers must rely on gauges and instruments to tell them depth, bottom time, direction, and air supply.

- Dive console: an enclosure molded with slots to hold a SPG, depth gauge, and compass.

1. SPG displays the amount of air pressure remaining in your scuba tank. SPGs can also be integrated in dive computers and measure pressure electronically. Some air-integrated dive computers can also monitor your breathing rate and predict how long the air in your cylinder will last based on your breathing rate.

2. Depth gauge: your depth and the duration of your dive at any particular depth are limited by a number of factors, so you need to monitor your depth when diving.

Depth gauge (continue)4 types: Capillary tube, bourdon tube, diaphragm

mechanism, and electronic gauge.

CompassWhen you are swimming under water and visibility is poor,

a compass is an important reference instrument, if not essential.

A diving compass must:1. Be filled with liquid to withstand pressure and dampen

needle movement under water2. Have a reference line, called a lubber line, used as the

direction of travel3. Have a means, such as a rotating bezel, to show a

selected bearing or direction

Additional diving instruments

1. Timing devices: diving watches or timer- Water and pressure resistant (100M)- To measure elapsed time: rotating bezel around the

dial or stopwatch feature

1. Dive computers- Most convenient method of keeping track of your

bottom time as well as your depth- A typical dive computer records or displays: maximum

depth, current depth, actual dive time, remaining allowable dive time

1. Backup instrumentation

Buoyancy Compensator (BC)

• BCs enable you to control whether you float on the surface of the water, hover in the water, or sink to the bottom. How?

• All BCs are made of durable material that can hold air and are designed for rugged use.

• Equipped with : overpressure relief valve, inflator/deflator hose, power-inflator mechanism, and deflator/oral inflator valve with mouthpeice.

Inflator/deflator hose

Low pressure hose

LP hose and powered-

inflator connector

Inflating bottom

deflating bottom

Oral Inflating mouthpiece

Different types of BCs: back flotation, Jackets, and Horse collars.

- Back flotation: entire air bladder is behind the diver; popular for underwater photography; difficult to swim on the surface.

- Jackets: most popular BCs; comfortable to wear; provide good trim under water; float you upright on the surface.

- Horse collars: - Integrated weight systems: Pros and cons?

Pros: no need to wear weight belt, the weights cannot slide around your body, the weight is not supported solely by your lower back

Cons: too heavy to be handled.

Selection: try it on and make sure it’s comfortable.

Maintenance: you should rinse your BC internally and externally after each diving day. How?

Accessory Equipment- Attachment devices- Knives- Gear bags- Dive flags and Floats- Logbooks- First aid kits- Other accessories