SELF CONTAINED UNDERWATER BREATHING APPARATUS (SCUBA) (PART 2)

Self Contained Underwater Breathing Apparatus (SCUBA) (Part 2)

So if you have read the post SELF CONTAINED UNDERWATER BREATHING APPARATUS (SCUBA) (PART 1) I am sure you will now be aware that it is all a matter of bubbles. We will concentrate on Open Circuit SCUBA, the one which vents bubbles every time you breathe out, and its fundamental components.

There are four components to Open Circuit SCUBA equipment:

High Pressure Breathing Gas Cylinder

Your breathing gas cylinder will normally be manufacture of either Steel or Aluminum. It will have an outlet valve that opens or closes the cylinder and permits the second component of SCUBA, the regulator, to be attached to the cylinder. The working pressure of the cylinder can vary from 200 bar to 300 bar and vary in size from 8 litre cylinders, suitable for junior divers up to 15 litre cylinders, great for air hogs.

The Regulator

The SCUBA regulator is a two stage pressure regulator which provides you with your breathing gas on demand from you cylinder when you inhale. The first stage regulator will reduce the gas pressure from your cylinder to an intermediate pressure (IP), typically 9 – 10 bar, which in turn will then be reduced by the second stage demand regulator to the ambient pressure for breathing.

Your first stage regulator would also have fitted an alternative air source regulator (AAS) or octopus for sharing breathing gas with your dive buddy in an emergency situation, an gas pressure gauge (SPG) that indicates your current cylinder gas pressure and a low pressure inflator (LPI) hose which supplies gas to your BCD at the IP to assist with you buoyancy control.

Buoyancy Control Device (BCD)

The majority of recreational divers use an inflatable jacket style BCD to control their buoyancy. Through the use of the LPI connected to your cylinder via the LPI hose gas can be added to or released from your BCD to assist you in attaining either neutral buoyancy whilst under the water or make you positively buoyant for resting at the surface or surface swimming.

Your BCD will also include a backpack to which your cylinder will be attached using bands thus holding you SCUBA system together in one integral unit. When we cover the BCD in more detail in a later post we can discuss the different styles.

Weight Systems

When diving, you use a weight system to just offset any buoyancy. It may be on a weight belt around your waist, a harness on integrated into your BCD.



Look out for the next more detailed posts on Open Circuit SCUBA equipment.

Please feel free to comment on any posts in this blog.

To find out more about SCUBA equipment available from Samui Dive Supply please contact us for more information.

SELF CONTAINED UNDERWATER BREATHING APPARATUS (SCUBA) (PART 1)

Self Contained Underwater Breathing Apparatus (SCUBA) (Part 1)

A month or so ago, doesn’t time fly when you’re having fun, we said we will introduce SCUBA equipment to you, attempt to explain what it is and what it does for you.

As an introduction there are three basic types of SCUBA equipment:

Open Circuit

When you breath in you use a two stage regulator that provides gas at the ambient pressure from a tank of compressed gas usually at 200 bar. When you breath out through your regulator second stage the exhaled air vents into the water as bubbles. Your SCUBA equipment would also consist of a Buoyancy Control Device (BCD) and weight system. This is the system we will focus on in more detail in the next post. An example of an Open Circuit Regulator would be the Scubapro Mk25 1st Stage witha S600 2nd Stage.

Semi-Closed Rebreathers (SCRs)

When you breathe in, you breathe from a counter lung in your SCR. When you breathe out your exhaled air passes through a scrubber that removes the excess carbon dioxide in the exhaled air. This air then passes into the counter lung where it mixes with oxygen that is flowing at a continuous set flow rate to produce your breathing gas. Any excess gas in the counter lung is vented off as a small stream of bubbles. An example of a SCR would be the Drager Dolphin.

Closed Circuit Rebreathers (CCR’s)

When you breathe in, you breathe from a counter lung in your CCR. When you breathe out your exhaled air passes through a system that removes the waste carbon dioxide in the exhaled air and replaces consumed oxygen then it returns to the counter lung. There are no bubbles. An Example of a CCR would be the Pelagian from RebreatherLab.

Look out for the next post on Open Circuit SCUBA equipment.

Please feel free to comment on any posts in this blog.

To find out more about SCUBA equipment available from Samui Dive Supply please contact us for more information.

BASIC EQUIPMENT FOR SCUBA DIVING AND SNORKELING (Part 4)

Basic Equipment for SCUBA Diving and Snorkeling (Part 4)

This week we have the second of two Blog posts covering the topic of the highly essential piece of diving/snorkeling equipment FINS.

Fins

To recap the basic function of a fin is to propel you the diver/snorkeler through the water with as little effort as possible for the most propulsion, to this end there are a multitude of designs now available on the market to suit everybody’s needs.

A fin consists of a foot pocket, either full foot “slipper fins” or open heel, and a blade which can be of many different designs.

In this Blog post we will cover the Open Heel adjustable design fins which are used predominantly by seasoned divers, dive professionals and in colder waters.


Open Heel Adjustable Fins

These fins are generally larger than full foot fins and provide more power which greatly assists the diver when wearing a full set of SCUBA diving equipment. We will introduce SCUBA equipment in the next Blog post, they have an Open Heel, hence the name, foot pocket with an adjustable strap to hold the foot in the foot pocket. The foot pockets come in a variety of sizes from extra small to extra large so they can encompass all foot sizes. The use of neoprene boots is also required.

The fin straps are generally made of rubber and are fixed to the fins using adjustable buckles some fin buckles also have a quick release mechanism to allow the diver to easily remove the fin strap and fin, especially useful when waiting to climb up the ladder of a boat. There is also the option to use spring heel straps such as the Saekodive Spring Strap with buckle. In place of the rubber strap a high powered spring is used to hold the foot in the foot pocket.

The blades are made from either rubber such as the Scubapro Jet Fin Classic or a mixture of rubber and techno polymers which encompasses the benefits on both materials.

The blades can incorporate channels to ease the flow of water across the fin but at the same time maximizing the thrust a good example of these would be the Seac Sub Propulsion fins and some fins have a split fin design which provides the diver/snorkeler with a propeller thrust effect, see diagram, such as the Scubapro Twin Jet fin or Max Twin Jet Fin.


You would normally find ribs down the edges of the blades, these tend to aid the flow of water down the length of the blade enhancing thrust and preventing the blade from twisting under stress.

To find out more about fins available form Dive Supply please contact us for more information.

Don’t miss the next Blog post an introduction to SCUBA by adding us to your RSS feed.


Own fins already? Why not take part in our poll to see which are the most popular brand fins used by our Blog readers.