S1E7: How do Aqualung used by divers work?
What are Aqualungs and why do Divers use them?
What are Aqualungs? ”A container of air that a person carries on his or her back when swimming under the surface of the sea, a lake, etc. (diving) and which provides air through a tube for the person to breathe.”
But, why are they needed? Water pressure increases rapidly with depth; therefore, divers need to survive such conditions by maintaining the same pressure within their lungs. Imagine if we inhale air at atmospheric pressure underwater when the water body is at a higher pressure - then, the lungs should expand and withstand the high pressure (Not possible as lungs are not powerful). Hence we need aqualungs which supply air from a cylinder maintained at high pressure. This gadget makes the divers sustain underwater.
Working Mechanism
The cylinder worn by the diver has air at a pressure much higher than the water pressure, initially. The mouthpiece worn by the diver has an assembly that helps them breathe air that is regulated at the same pressure as the surrounding water. Let’s see how.
Inhalation
The valve (pink) is initially closed. As the diver (marked in brown) inhales air from the air chamber (white), the flexible diaphragm (red) expands downward due to pressure decrease inside the chamber (Lesser volume of air in the chamber due to some inhalation, so less pressure).
This diaphragm presses against the lever (yellow) in the chamber, causing it to open a valve (pink) to let in air from the cylinder carried by the diver.
The high-pressure air from the air cylinder drops to the surrounding water pressure right when it comes into the air chamber. This is achieved by having the water inlet on the other side of the diaphragm (dark blue). Water is drawn in through this opening automatically from the sea, lake, etc. (as seen in the figure) to balance the pressure.
Thus, we achieved the same pressure for the surrounding water and the air chamber using a flexible diaphragm in-between and a water inlet. The diver inhales the air that came in from the cylinder.
Exhalation
When the diver finishes inhaling, the increased volume of air (there is continuous air intake from the cylinder as long as the valve is open) in the air chamber pushes back the diaphragm which then pulls the lever to shut the valve, and thereby, cutting the airflow.
The air chamber has an exhaust valve through which the exhaled air by the diver is released into the waterbody (These are the trail of bubbles that we see typically in a documentary or a movie from a diver).
Conclusion
There is a button to clear the water from the flooded mouthpiece in such cases. This process then repeats again. This is how an Aqualung works making it possible for divers to do their job.
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