I am sorry, but in reality this video only shows the cylinder being subjected to over-pressure, not hydro testing! I am no expert, but my understanding of a "hydro test" is to subject the pressure vessel to pressure to which the tank is certified (which he did in a way!) However, the part that he left off and didn't do is the part that tells you if the tank is good or not!! Basically, a tank is submerged in a liquid, filled to the rated capacity and the liquid surrounding the tank is what is measured. If you over pressure a tank to it's rated capacity, it is allowed to "swell", as metal is going to stretch (think of a balloon!) Once the pressure is released back to atmospheric pressure, the tank should return back to it's normal state. There is a certain allowance for just how far it will stretch and not return back which is measured by the displaced liquid OUTSIDE the tank!!
So if you blow up a balloon under water, say in a bathtub, you mark the water line before you start, and again when you reach full pressure, and then let the air back out of it. The amount that the water did not return to it's original level is the amount that concerns you (the amount is figured out by some formula). Everyone who has ever blown up a balloon can see that there is a difference in the appearance of a balloon before and after it is been blown up the first time. You can't see it with a steel pressure vessel, but that is basically what you are measuring. The elasticity of the metal and it's ability to stretch and then return to it's original shape (size) is the factor that keeps tanks from blowing up on you.
My hat is off to the poster for presenting a nice video, however it is VERY MISLEADING, because in reality what he did to his own tank did more harm than good.
I am also surprised at American Rotary for putting their stamp of approval on it!
David from jax
