IDC Guide

Dive Theory –

More Equipment

PADI IDC Theory: Equipment – Regulators

The Basics

PADI IDC and IE Exam regulator questions often focus on either the first stage or the second stage

How it works

First Stage
The job of the first stage is to bring the high cylinder pressure down to intermediate pressure, which is the pressure that’s in all of the hoses, apart from the high pressure hose that leads to your submersible pressure gauge.

Second Stage
This the part that you breathe from. It’s job is to bring the intermediate pressure down to ambient pressure.

This might help

First Stage
Questions range from DIN valves to Environmental seals. There are also questions about the mechanism of the first stage that can confuse people, because sometimes, there’s a question about a diaphragm valve or a piston valve. These valves can only be found in the first stage, so be careful and not confuse a diaphragm valve with the large diaphragm in the second stage.

Second Stage
There are various questions about the second stage, ranging from a split mouthpiece causing water to creep in, through to where the second stage of an alternate air source should be. This brings me to the next area that sometimes causes confusion. The ONLY thing that’s important with alternate air source is that it’s in the triangle. It doesn’t matter what colour it is, nor which side it comes from.

PADI IDC Theory: Equipment – Cylinders

The Basics

Cylinders are different sizes and made of different materials. Steel or Aluminium. They need to be regularly tested according to local law.
This might help.

Steel cylinders
These cylinders require you to wear less weight that aluminium ones because they displace less water and feel “heavier” in the water.
Steel cylinders that bear a + sign from the last test can be overfilled by 10 per. cent.

Aluminium cylinders
Of course aluminium cylinders require you to wear more weight when you’re diving than you would with a steel cylinder.

Routine Tests
Local law requires cylinders to have a visual test and a hydrostatic test. Visual testing involves a technician removing the first stage and checking the walls for signs of damage. Hydrostatic testing involves immersing the cylinder and pressurising it with water. Providing measurements are within standards, the cylinder is then stamped and can be used for another period of time.

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