SurfLung wrote: ↑Tue Jan 08, 2019 2:33 pm
Thanks Luis... That makes perfect sense but it isn't what some Dive Professionals are leading sport divers to believe. I was just visiting with Rich (50,001 Questions) and he has had a dive professional tell him he's carrying a "bomb" on his back in reference to a tank that had just passed hydro but had some rust inside. The hydro operator had simply advised him he had some rust he should take care of ... Either looking for and removing the cause or just getting the tank tumbled to clean it up. Suggesting it was a
"bomb" tells me the local professional maybe was not as knowledgeable about the cylinder re-qualification process as you would expect him to be.
The training required to be a hydro station operator is not very extensive. They don’t have to be highly qualified technicians to perform the job.
But, on the other hand calling a pressure cylinder a “bomb” it is actually not that inaccurate from an energy point of view. I totally understand the point (and I agree) that there is no real need to make it sound dramatic. Just like I hate calling Scuba gear "life support System".
But a pressurized cylinder does contain the energy of a small bomb.
If you are referring to cylinder in good condition, with no rust or corrosion, and no other types of defects, a pressurized cylinder could be loosely equated to a “bomb” without any kind of a fuse.
If you are talking about a cylinder with rust, then it depends on how much rust. Very mild surface rust it would still be a “bomb” without a fuse.
If the rust is heavier and is holding some moisture then it could be loosely equated to a “bomb” with a slow fuse (or similar). Heavy rust or even medium rust (but how do you define that??) can hold moisture, which in turn is a catalyst for more rust and potential pitting.
These analogies are just loosely equivalents based on the potential energy stored in a pressurized cylinder.
BTW, on the subject of internal cylinder rust. I use a wire brush/ whip driven with an electric drill to remove any rust and I try to polish the inside of my cylinders with it. A clean polished steel surface provides less surface area to hold moisture and also less area exposed for rusting.
There is an easy test called a “hammer test” that is always supposed to be performed on all steel cylinders just before they are filled (but many fill operators are not aware of it). The test will give you an idea if there is excessive internal rust without actually looking inside.
All the test involved is lightly hitting the side of a steel cylinder with a small hammer or similar metal. A cylinder in good condition (with minimal or no rust) will sound clear as a bell.
If the cylinder doesn’t sound clear as a bell (it sounds dull), it is likely due to excessive rust and should not be filled without further investigation. I would not fill it.
Internal rust will dampen the typical sharp bell sound. I am sure everyone is familiar with the clear bell sound of a steel cylinder.
Note: this is only an extra indicator of the presence of rust and I have only notice the dull sound on a cylinder with a lot of rust.