Having learned to dive late in life I made up for it in my first year by clocking up 120+ open water dives in places from the UK to Australia. I went from a non diver to a technical deco diver in 9 months and loved every second of it. Since having kids not been able to travel as much so spend my time watching videos and reminiscing, hope you enjoy my site as much as I have making it.
All metals produce diferent voltages when put together in salt water. Thus the only compatible metal valve would be that made out of the same material typicaly T6061 Aluminium Alloy. However, in practice, compatible aluminium alloy valves were found to be not tough enough to survive the harsh work environment endured by scuba tanks, and thus the modern chrome plated brass valves have prevailed, at the expenses of sometimes extreme corrosion in the cylinder next face region adjacent to the valve
The DOT commissioned an extensive investigation into SLC cracks in Aluminium SCUBA tanks and the best way to detect them. The 200 page report identified magenetic eddy current NDT testing as the most cost effective method. Advanced Inspection Technology Co in the USA makes SCUBA cylinder NDT testing equipment – A Google search should find them
What is the acceptable NDT of scuba tanks? x-ray, dye penetrant or mag-particle? All of these are good but all open to interpretation of of what someone thinks for a set of results and still have room for failure.
Good point – would I be correct in assuming that's a form of magnetic field testing – internal flaws causing variations in the surface flux pattern?
Used it for steel cranks, rods, etc.
@GordonWG1 Intuitively, increasing the periodicity of Hydrostatic tests should help remove these potentialy hazardous tanks suffering from sustained-load-cracking (SLC). However, in practice this is not the case. Cylinders with SLC can and do explode soon after a successful hydro test. The solution is to carry out Eddy current NDT testing of the critical neck area. NDT testing can sucessfullly identify SCL well in advance of mechanical fauilure and is the preferred method to detect this anomaly.
Aluminium (aluminum to the US lads) alloys are susceptible to fatigue cracks and catastrophic failure. The fatigue is from the strain from the loading and unloading of the material with the air pressure – more the tank is used, the sooner the fatigue will be an issue.
if they are frequentlty refilled – several times a day, I'd be tempted to up the pressure testing to every two years, or even more frequently, as a failure in use can result in serious, even fatal, injury!
@braslfakr (Top Secret)…
The 80 cubic foot of air (at 1 atm pressure) is compressed by 3,000psi of pressure into a conveniently portable volume, and voila, you have a scuba tank.
I am very interested in the problem that affected your aluminium cylinders – what happened? Was it a manufacturing defect? How old were they?
All cylinder manufacturers are keen to weed out the occasional rogue cylinder – So let’s have some info, and if you have a genuine rogue cylinder, I can help you with the refund process.
@frithwks
To remain independent, we neither sell nor promote steel, aluminium or fiber cylinders – or any one manufacturer. Our job is to instruct new technicians how to impartially inspect and repair diver’s life support equipment including high pressure cylinders.
All modern scuba cylinders be they NCM Steel or T6061 Aluminium types have a long design life if used according to the manufactures instructions.
@frithwks Both steel & aluminium scuba cylinders are safe if filled with clean dry air to EN12021, handled accorded to the manufacturer’s instructions and inspected periodically.
If you mean rupture, its due to people overfilling them (For an Aluminum 80 3000psi is the maximum fill). So people put more in for more bottom time. Another common reason is when they get old they start to pit and get small cracks that can eventually make the rupture. You are required to have them visually inspected every year and hydro statically tested every 5 years.
Amazing that all of this can be done and they sell for $150 with valve. Must make millions of them to make a profit.
good video
Why can't you take a light grit sandpaper and sand your tank ?
All metals produce diferent voltages when put together in salt water. Thus the only compatible metal valve would be that made out of the same material typicaly T6061 Aluminium Alloy. However, in practice, compatible aluminium alloy valves were found to be not tough enough to survive the harsh work environment endured by scuba tanks, and thus the modern chrome plated brass valves have prevailed, at the expenses of sometimes extreme corrosion in the cylinder next face region adjacent to the valve
What's the valve made of? If you're going to immerse it in salt water, it should be galvanically compatible with aluminum.
The DOT commissioned an extensive investigation into SLC cracks in Aluminium SCUBA tanks and the best way to detect them. The 200 page report identified magenetic eddy current NDT testing as the most cost effective method. Advanced Inspection Technology Co in the USA makes SCUBA cylinder NDT testing equipment – A Google search should find them
What is the acceptable NDT of scuba tanks? x-ray, dye penetrant or mag-particle? All of these are good but all open to interpretation of of what someone thinks for a set of results and still have room for failure.
Good point – would I be correct in assuming that's a form of magnetic field testing – internal flaws causing variations in the surface flux pattern?
Used it for steel cranks, rods, etc.
@GordonWG1 Intuitively, increasing the periodicity of Hydrostatic tests should help remove these potentialy hazardous tanks suffering from sustained-load-cracking (SLC). However, in practice this is not the case. Cylinders with SLC can and do explode soon after a successful hydro test. The solution is to carry out Eddy current NDT testing of the critical neck area. NDT testing can sucessfullly identify SCL well in advance of mechanical fauilure and is the preferred method to detect this anomaly.
Aluminium (aluminum to the US lads) alloys are susceptible to fatigue cracks and catastrophic failure. The fatigue is from the strain from the loading and unloading of the material with the air pressure – more the tank is used, the sooner the fatigue will be an issue.
if they are frequentlty refilled – several times a day, I'd be tempted to up the pressure testing to every two years, or even more frequently, as a failure in use can result in serious, even fatal, injury!
@braslfakr (Top Secret)…
The 80 cubic foot of air (at 1 atm pressure) is compressed by 3,000psi of pressure into a conveniently portable volume, and voila, you have a scuba tank.
I am very interested in the problem that affected your aluminium cylinders – what happened? Was it a manufacturing defect? How old were they?
All cylinder manufacturers are keen to weed out the occasional rogue cylinder – So let’s have some info, and if you have a genuine rogue cylinder, I can help you with the refund process.
@frithwks
To remain independent, we neither sell nor promote steel, aluminium or fiber cylinders – or any one manufacturer. Our job is to instruct new technicians how to impartially inspect and repair diver’s life support equipment including high pressure cylinders.
All modern scuba cylinders be they NCM Steel or T6061 Aluminium types have a long design life if used according to the manufactures instructions.
@frithwks Both steel & aluminium scuba cylinders are safe if filled with clean dry air to EN12021, handled accorded to the manufacturer’s instructions and inspected periodically.
If you mean rupture, its due to people overfilling them (For an Aluminum 80 3000psi is the maximum fill). So people put more in for more bottom time. Another common reason is when they get old they start to pit and get small cracks that can eventually make the rupture. You are required to have them visually inspected every year and hydro statically tested every 5 years.
Nice…….Great video!
beauty