This time we will address a speech that might seem unimportant, instead it is one of those few concepts that a good diver should know well.
Mastering this concept, it helps us first to dive with greater awareness of the risks that run when you want to challenge a Physical Law and the consequences that derive from it to the detriment of our health, in some cases even very serious. But apart from what has just been expressed, the concept of pressures it is also very useful for all those divers who want to acquire particular specialties such as Nitrox or diving with mixtures.
Whenever a force acts on a surface we can talk about pressure, which is measured in Pascal. This means that a same force can generate pressures very different by changing the area of the surface on which it acts. Wanting to apply the “Pascal Principle” in the case of a diver, the force exerted, given by the weight of the pressure on a diver’s body, It acts in all directions and with equal intensity. So this concept makes us understand that the diver the deeper it goes, the greater the weight and therefore the crushing to which it is subjected.
The thing that always fascinated me about this issue of Physics is that it made me reflect on the fact that really Mother Nature has thought of everything.
In fact it is possible to practice scuba diving because our body has a large amount of liquids and liquids by physical principle they can have great elasticity but remain incompressible.
Now we see more details and how to measure these pressures.
The ambient pressure of a liquid contained in an open container (in our case: Seas, Lakes, etc. etc.) is derived from two values.
The atmospheric pressure above the liquid which would be the weight of the air column, equal to 1ATM / BAR above sea level
The hydrostatic pressure that it would be the weight of the water column and which increases with a constant rate of 1 BAR / ATM every 10 mt. of depth.
From the result of these two values, we obtain a data called “Absolute Pressure”. To summarize with a few practical examples, let’s start from the pressure on the sea level that remains unchanged and is 1 BAR / ATM. In a future article I will talk about when and why also the pressure on sea level changes.
While the hydrostatic pressure, as already explained above, will undergo a directly proportional variation based on the depth.
If we wanted to obtain the absolute pressure at a specific depth, for example -18mt, the calculation to do is the following:
1,8 ATM/BAR (Ambient pressure at -18mt) +
1 ATM/BAR (Atmospheric pressure) =
The data that we get from the two values above, is the absolute pressure at -18mt.
2,8 ATM/BAR (Absolute pressure at -18mt)
Pressure in scuba diving with and apnea, they are a fundamental element, since their influence on our body is noticeable. Later we will also see how to learn to compensate correctly and what techniques are used to counteract the variation of pressures.
Author Francesco Cordone