Hydro after tumbling?

[halocline]

Is it a DOT regulation that tanks are re-hydroed after tumbling, or is that just a policy of some hydro facilities? I'm getting my 72 doubles tumbled and the place doing it wants to re-hydro the tanks, even though there are four years left on the hydro.

thanks!

 

[JKPAO]

no you do not have to have them re hydroed! I just asked the same question to a PSI trainer!
Professional Scuba Inspector
See you topside! John

 

[paddler3d]

The only thing I've read about getting a tank 're-hydroed' is if it gets too hot, something like 180F for AL and I can't remember AA.

Why do the want to get in re-hydroed?

Tumbling can remove nothing to a little. Oxygen Hacker's guide had a whole diatribe on tumbling and how it would take A LOT of tumbling before one would begin to compromise the structure of the tank. It was something like 20 years of tumbling.

I guess my question is how wet is your guys air if you had in VIP in Hydroed last year that it needs a tumbling and hydro this year?

 

[halocline]

The reason for the question is that I am choosing to get them tumbled, and the hydro place told me that it's a regulation that they re-hydro after tumbling. I thought I explained that, but I guess I didn't make it clear.

So, just to be crystal clear, it's not a regulation?

 

[paddler3d]

The only DOT regulation I know of, and can find, is that they need to be hydroed every 5 years.

Also DOT regulation only apply to cylinders used in commerce. So technically you don't even have to have your personal SCUBA tanks hydroed every 5 years.

Send Oxyhacker a PM. He knows the DOT laws involving compressed gas tanks like the back of his hand.

 

[DCBC]

The reason for the question is that I am choosing to get them tumbled, and the hydro place told me that it's a regulation that they re-hydro after tumbling. I thought I explained that, but I guess I didn't make it clear.

So, just to be crystal clear, it's not a regulation?

To the best of my knowledge, there is no regulation that states that a hydro is required after tumbling, as long as the cylinder's hydro is current. If the facility wishes this to be done, I'd tell them that you don't believe it's a requirement, but if they show you the regulation, you'll be happy to pay them to do it.

 

[muddiver]

Also tell them that they will be responsable for removing all flash rust inside the cylinder, at their expense, after the hydro test. That should help.

 

[oxyhacker]

Ask them to show you the regulation.

We like to refer to this as the "hydro trap", where you take the tank in for a visual, and the shop tells you it needs tumbling, then insists it needs rehydro. Your $12 visual is now a $50+ major service. The ironic thing is, the shops that insist on hydro after tumbling are often the shops that insist on tumbling for minor flash rust, which is also unecessary and not required by the DOT.

All a good argument for doing your own pre-inspection before you bring a tank in for a visual, and having your own whip so you can do a minor touchup yourself.

The DOT regulations, which can be found in 49 CFR 180.205 speciifies several conditions that may require immediate retesting rather than waiting for the next calender hydro, Tumbling is not one of them.

Nor does the CGA or PSI literature say anything about it. I've also discussed this issue with PSI's Bill High, who said that tumbling just doesn't remove enough material to matter.

Steel tanks typically have enough "extra" metal to withstand a lot of tumbling. For example, the DOT limit for wall thickness on a steel 72 is .164" at manufacturer, and a minimum of .155" in service, but in real life they run closer to .185". Aggressive tumbling removes about .0005 a day So it would take several months of continuous tumbling before the wall thickness approached the DOT minimum!

You could argue that a really old tank which had been repeatedly tumbled over the years might be getting near the danger point. But there is no statuatory requirement to do so, and to insist on hydroing a relatively new tank, as some shops do (in one case we heard about, the tank was only one year old!) just because it has been tumbled just doesn't make sense.

 

[paddler3d]

Send Oxyhacker a PM. He knows the DOT laws involving compressed gas tanks like the back of his hand.

Ask them to show you the regulation.

We like to refer to this as the "hydro trap", where you take the tank in for a visual, and the shop tells you it needs tumbling, then insists it needs rehydro. Your $12 visual is now a $50+ major service. The ironic thing is, the shops that insist on hydro after tumbling are often the shops that insist on tumbling for minor flash rust, which is also unecessary and not required by the DOT.

All a good argument for doing your own pre-inspection before you bring a tank in for a visual, and having your own whip so you can do a minor touchup yourself.

The DOT regulations, which can be found in 49 CFR 180.205 speciifies several conditions that may require immediate retesting rather than waiting for the next calender hydro, Tumbling is not one of them.

Nor does the CGA or PSI literature say anything about it. I've also discussed this issue with PSI's Bill High, who said that tumbling just doesn't remove enough material to matter.

Steel tanks typically have enough "extra" metal to withstand a lot of tumbling. For example, the DOT limit for wall thickness on a steel 72 is .164" at manufacturer, and a minimum of .155" in service, but in real life they run closer to .185". Aggressive tumbling removes about .0005 a day So it would take several months of continuous tumbling before the wall thickness approached the DOT minimum!

You could argue that a really old tank which had been repeatedly tumbled over the years might be getting near the danger point. But there is no statuatory requirement to do so, and to insist on hydroing a relatively new tank, as some shops do (in one case we heard about, the tank was only one year old!) just because it has been tumbled just doesn't make sense.

Told you he'd know!

 

[redacted]

The reason for the question is that I am choosing to get them tumbled, and the hydro place told me that it's a regulation that they re-hydro after tumbling. I thought I explained that, but I guess I didn't make it clear.

So, just to be crystal clear, it's not a regulation?

The key to this question is have you already turned the tanks over to the facility for tumbling? If yes, you may want to apply christolube to dynamic specs before you try to pick them up.