Changing Gas in a Tank

[garyw90]

Thanks for all the good comments.

The issue of draining the tank and then filling with EAN comes up because this is California after all, and thanks to OSHA, EAN is considered a flammable risk, hence not all dive shops can fill EAN. When I told the dive shop, which does not do EAN, that the tank currently had a 28% blend, they said they don't do blending, take it somewhere else. Knowing that the tank as not pure air, that was why I asked them to drain it and then fill it, to which the guy told me they would have to viz the thing. Maybe I just bring the tank down to 500PSI, then bring it in for a fill, and not tell them the 500 PSI is EAN28. By the way, the EAN 28 is only because the tank previously had EAN 32 in it for a dive, then the next dive as in shallow water (20 ft), so I didn't think it warranted EAN. 28% is what the analyzer told me.

 

[aquaregia]

Does he put the valve back on using a vacuum pump after doing the vis? Otherwise, the risk of getting water in while draining the tank (in the presumably dry shop) will be the same as the risk of getting water in during the vis.

Requiring a vis on their tanks if you return them at a pressure that could allow water to intrude makes sense. I'm already getting a vis a year on my tanks; any additional inspections should be based on my assessment of risk, not theirs.

I'd find a new shop. My dive buddy had our LDS drain a tank of 36% and fill with air just last week (planned depth > MOD) and there was no drama at all.

 

[halocline]

Thanks for all the good comments.

The issue of draining the tank and then filling with EAN comes up because this is California after all, and thanks to OSHA, EAN is considered a flammable risk, hence not all dive shops can fill EAN. When I told the dive shop, which does not do EAN, that the tank currently had a 28% blend, they said they don't do blending, take it somewhere else. Knowing that the tank as not pure air, that was why I asked them to drain it and then fill it, to which the guy told me they would have to viz the thing. Maybe I just bring the tank down to 500PSI, then bring it in for a fill, and not tell them the 500 PSI is EAN28. By the way, the EAN 28 is only because the tank previously had EAN 32 in it for a dive, then the next dive as in shallow water (20 ft), so I didn't think it warranted EAN. 28% is what the analyzer told me.

Whatever. Any shop that says you need to VIS a tank because it drops below 500 PSI is totally full of it. It has nothing to do with OSHA, but it's a nice touch to blame it on the government.

Dive shops and the "rules" of handling compressed gas; it's a humorous combination.