How often do you have to send your tank for a tumble?

[dytis-sm]

I have a Farber steel 117cf which I purchased new a year ago. This is my first VIP since purchase and my LDS discovered some rust on the bottom. The tank has to go for a tumble but I am a bit surprised because my other tank which is older, had to also go for a tumble at the last VIP. Which makes me wonder how often does a tank have to go for a tumble? Is that something common?

I was told that some of these rust marks are because of "wet" boat fills but I rarely get boat fills as I typically bring Nitrox on board. Which leads to the second question whether filling nitrox to non O2 tanks promotes rusting in the tanks.

I do live a block away from the ocean and our air is nice and moist but I find it hard to believe that this is an issue. Any suggestions in preventing rust inside the tank?

 

[parzdiver]

I have never had to have my tanks tumbled. I have four HP100's, one set is doubled, that I have had five years. Rust is only caused by moisture, so filling Nitrox into a non-O2 tank won't contribute to rust. If your fill station puts the tanks in water to fill them, there is a good chance moisture will get in. Ambient air humidity shouldn't be able to get into a tank unless you empty the thank. Watch where you get you fills, that is the most likely source of the moisture getting into your tank.

 

[OkByMe]

Have you seen this yourself? There is nothing wrong with you pulling the valve just before taking them for a fill and taking a look-see. I do my own tank maintenance and have a compressor, so I can keep a minimum pressure in the tanks. As far as you local humidity goes - the tank valve should be closed and have a positive pressure in it, so that is a non issue. When you fill the tank, the fill air or mix is always dry, very dry! A little flash rust never hurt a tank and even if you use heated air <125deg. to dry after cleaning, you can never put the valve in quick enough to prevent some humid air from entering the tank, but when the tank is filled - right away is best, the air is DRY.

You can make your inspection light by using any old 12v charging transformer from a cell phone or laptop, buy a socket and led light from Autozome, crimp the leads and wrap some stiff tape around the first 2 inches (so you can bend it and it holds shape) tape the cable to a stiff wire or fiberglass rod and there you go. An inspection mirror small enough to fit into the neck on a swivel will allow you to see inside the curve of the shoulder. If all you see is what appears to be a light dust and no spots - the tank does not need a tumble. Do not expect the inside of the tank to shine... it is drawn into shape and the inner die will not make a shiny surface. If you ever buy a tank, always pull the valve an inspect it new or not.

 

[scubastingray]

If your fill station puts the tanks in water to fill them, there is a good chance moisture will get in.

Wait, what?

 

[parzdiver]

Having water anywhere near the fill station increases the chance that water will get on the valve or the fill whip and get into the tank. And the water bath has minimal affect on the fill.

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[Namreg 58]

Having water anywhere near the fill station increases the chance that water will get on the valve or the fill whip and get into the tank. And the water bath has minimal affect on the fill.

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You are speaking from experience of course............I can tell.

Any fill monkey worth his salt will blow out the fill whip and tank valve before connecting them.
This leaves only sloppy filter maintenance for ingress of moisture.

 

[Doc Harry]

How often do you have to send your tank for a tumble?

Whenever a tank needs it.

If the valve is wet when the cylinders are filled, some of that mositure will be blown into the tank. Blow-dry your valve with the fill whip before hooking up for a fill. Problem solved.

I have my own tumbler, so this year I ran all of my cylinders for a quick 15-minute tumble before oxygen-cleaning them.

 

[Kharon]

I'd find someplace else to get fills.

 

[Wookie]

You are speaking from experience of course............I can tell.

Any fill monkey worth his salt will blow out the fill whip and tank valve before connecting them.
This leaves only sloppy filter maintenance for ingress of moisture.

If fill monkeys were worth their "salt", they would be regulator techs. They aren't, that's why they are fill monkeys. The peter principal works better in a dive shop than anywhere else. When a customer comes in, get all his money. When he hangs out long enough to be in the way all the time, make him a tank monkey. When he gets that down, make him a regulator tech. Follow that up with sales associate, weekend manager, manager, and eventually store owner. You'll find the place where he is no longer competent. Keep him in that position until the store goes out of business, or he no longer dives.

 

[halocline]

How do you know your tanks need to be tumbled? Is it the dive shop telling you? Is this the same shop that fills your tanks?

The humidity in the air has no effect on the inside of the tanks, unless the shop's compressor is not filtering out all the water. This does happen occasionally. All it takes is one wet fill and your tanks will get some rust.

But, a bit of flash rust is nothing to worry about and can easily be brushed out with a light wire brush on a long stick. Tumbling is a bit more aggressive.