HP80 needs tumbled. Should I worry?

Clanggedin · May 29, 2009

Last year I was gifted an older steel HP80 and before using it I had a vis and hydro done on it in which it passed. I just took it in for it's vis inspection this year and got a call this morning saying that there is rust flakes inside the tank and that it needs tumbled before it will pass vis.

Is tumbling steel tanks a common occurrence? How deep do the pits need to be before a tanks fails inspection.?

What would have caused all of the rust inside the tank? I only fill my tanks at one location? Could they have water vapor in their air that is causing the damage?

Should I worry that I may need to buy me a new tank?

Cave Diver · May 29, 2009

Tumbling tanks is fairly common. I'm not a tank inspector so I can't tell you how deep a pit can be and still be passable. It will really depend on how badly rusted the tank is.

As far as how it occurs, rust inside the tank means moisture has entered at some point. This could occur from storing the tank empty, or it may be getting moisture from the fill compressor. The filtration system should be providing clean dry air, but sometimes they're not up to par and moisture enters the tank.

I'd wait for the results before you start worrying and if I'd question the source of your fills and suggest they check other tanks that have been filled from there.

tfsails · May 29, 2009

Tumbling steel tanks isn't an everyday occurrence, but it's not rare, either. Oxidation (rust) can occur when air with a lot of moisture is introduced into your tank. A common way for this to happen is if your LDS has not serviced the moisture separators on its compressors.

Properly maintained steel tanks will last much longer than their owners, so I'd say get the thing tumbled and press on. Of course, if TOO much rust occurs inside the tank it can destroy the tank, but you'd probably have to leave salt water in it for several years for that to happen.

Bottom line--light surface rust that can be tumbled out is not a big deal.

Clanggedin · May 29, 2009

Thanks for the response guys. I always leave around 800-1000 psi in my tank before I store it. I guess I won't worry too much until I get the results back from the re-inspection after the tumble.

rstofer · May 29, 2009

The fill stations can get water in the tank if they have a water basin. The water can splash into the valve when the tank is placed in the basin or the operator can drop the whip in the water and not blow the water out before connecting to the tank.

If you have always stored the tank with pressure, there is no doubt where the moisture came from: your fill station.

Since it is not in my nature to trust people, I took the PSI Visual Inspection course so I can visual my own tanks. Not so much for the annual recertification but just to know what I am looking for. I have 14 tanks to worry about and 7 of them are steel. I would certainly hate to see my expensive HP 100s damaged by a fill station.

Richard

RJP · May 30, 2009

Possibly not your fill station. If the tank was O2 cleaned and then not dried properly flash rusting could have resulted.

SDAnderson · May 30, 2009

Is tumbling steel tanks a common occurrence?
Not common but not uncommon, either.
How deep do the pits need to be before a tanks fails inspection.?
Depends on a number of factors including location and number but they don't have to be very deep - we're talking hundredths of an inch in most areas.
What would have caused all of the rust inside the tank?
Water. Combine water with oxygen and iron and you get rust. The only factor you can control is the water.
I only fill my tanks at one location? Could they have water vapor in their air that is causing the damage?
The water could have come from any number of sources but there is only one way in the tank - through the valve.

The most common method for water to get inside the tank is when the filtration system on the compressor fails or is overwhelmed. Not much you can do about this other than to ask to see the lab results from their testing program - it will list the water content.

Secondarily, water can get inside the tank if the valve is wet. This would often happen in days of yore when tanks were filled while standing in a tub of water, otherwise it comes from a poorly dried valve. Easy to fix - blow out your valve religiously and don't get your cylinders filled by anyone who still uses a water bath.

Finally, assuming we're ruling out teleportation and curses, comes ambient air. If you let your cylinder run empty, humid ambient air can get inside. It doesn't seem like a lot of water but it doesn't take a lot of water, either. We all learned to avoid this during OW by keeping some positive pressure in the bottle.

Should I worry that I may need to buy me a new tank?
Any time you have to have a cylinder tumbled because of rust, you should be worried. Most of the time the tumbling works and you're good to go, however. By the way, this is an excellent opportunity to upgrade to an oxygen serviced tank, good for partial pressure blending nitrox. The tank will be clean, all you need to do is service (or replace) the valve and you're in business.

HP80 needs tumbled. Should I worry?

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Clanggedin

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Cave Diver

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