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 SystemsWhen 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.
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