How much rust after hydro is acceptable?

[Gilldiver]

Why doesn't your hydro shop just use the rust inhibitor and save all the unnecessary trouble?! Besides, I thought a tank had to be rehydroed after tumbling.

SCUBA tanks are less than 1% of a hydro shops flow through, fire extinguishers, industrial gas cylinders (welding gas bottles), and CO2 bottles have way more volume. You cater to your volume which don't care about flash rust.

They could use hot water as a final rise and dry quickly, but that is an extra rinse and the cost to heat the water. Same goes for a rust inhibitor - extra time and costs and no one is requesting it - or paying for it.

There are no regulations or industry practices requireing hydro after tumbling - just Dive Shop hear-say which has become fact over time, just as the reasons for tumbling in the first place. 99.99% of all tanks that are tumbled could have been cleaned with a whip faster, easier, and at a lower cost than being tumbled.

 

[halocline]

I am a certified tech at my dive shop and I service all of our customer tanks. Steel tanks become flash rusted after hydro, so we tumble them lightly with a week acid and ceramic chips to get rid of the rust. Then we completely rinse them out with water and a second rinse with a rust inhibitor and then dry the tanks on a warm air tank drier. This proper care ensures that our customer tanks will be in great condition for the life of it's use. I hope this helps you.

If I showed up at a dive shop and someone told me they used acid and rust inhibitor in my breathing air tank I'd be REALLY pissed.

This is so simple, just dry out the damn tank after hydro. If the hydro place can't get that right find another one.

 

[moinaman]

"If I showed up at a dive shop and someone told me they used acid and rust inhibitor in my breathing air tank I'd be REALLY pissed."

I guess you have no experience reconditioning scuba tanks. This isn't something we just made up. These are items specifically designed for reconditioning scuba tanks.

 

[moinaman]

Why doesn't your hydro shop just use the rust inhibitor and save all the unnecessary trouble?! Besides, I thought a tank had to be rehydroed after tumbling.

I agree. I wish they would just provide this service. I hate tumbling tanks. It's a pain

 

[moinaman]

If I showed up at a dive shop and someone told me they used acid and rust inhibitor in my breathing air tank I'd be REALLY pissed.

This is so simple, just dry out the damn tank after hydro. If the hydro place can't get that right find another one.

Here's a link so you can be educated about proper tumbling methods
http://www.gmcscuba.com/pdf/tank cleaning & tumbling tips.pdf

 

[halocline]

I guess you have no experience reconditioning scuba tanks. This isn't something we just made up. These are items specifically designed for reconditioning scuba tanks.

What is this "reconditioning" nonsense? We're talking about a hydrotest. Steel tanks with rust from wet fills or other water intrusion need to be tumbled. Tanks that are tested and dried correctly don't. Further, if there is a layer of flash rust in an otherwise 'healthy' steel tank from a lazy hydrotester, using acid to remove it is nuts. In fact, tumbling shouldn't be necessary, just a good brushing.

 

[duckbill]

There are no regulations or industry practices requireing hydro after tumbling - just Dive Shop hear-say which has become fact over time,....

Yeah, you guys are right. I'm starting to forget stuff. My bad. Thanks.

 

[JKPAO]

You should know Simple Green is on the acid side of the scale! IJS
My shop follows the same process as moinaman.
See you topside! John

 

[moinaman]

What is this "reconditioning" nonsense? We're talking about a hydrotest. Steel tanks with rust from wet fills or other water intrusion need to be tumbled. Tanks that are tested and dried correctly don't. Further, if there is a layer of flash rust in an otherwise 'healthy' steel tank from a lazy hydrotester, using acid to remove it is nuts. In fact, tumbling shouldn't be necessary, just a good brushing.

again, it's clear you don't have experience servicing tanks. I posted a link for scuba tank service for anyone that would like the knowledge of reasons for tumbling tanks and it's process. Ideally, I would love to have our tanks come back from the hydro test facility without flash rust, but they do not provide service to prevent it. That's where we come in. The next hydro facility is over 50 miles away, and they are just the same way anyway, so we just deal with it fix it.

 

[Hatul]

It is an alternative to tumbling.

You put the whip on the end of a drill and as it spins it removes light rust particles:

Tools - Tank Cleaning - Whips and Brushes - Northeast Scuba Supply

Afterwards blowing it out with clean dry air.

I'd be concerned that even after blowing out the tank, fine steel or rust particles will remain to be breathed into the lungs. I'd rather have some rust in a tank than have steel dust in my lungs.

Adam