Oxygen tank cleaning, how to do it...

[wreck-tekkie]

Hi all,

My first post.... :doh2:

I just cleaned some (steel) tanks, after reading some books (i.e Vance Harlow's Oxygen Hacker's Companion). What I did was the following:

- demounting valves
- fill tank with 1/3 with Simple Green Chrystel (1:10)
- Shake, roll and tumbled the tank for 15 minutes
- Rins out with hot water (60 degr Celsius) for 10 minutes
- Use an hairdryer with hose to blow warm air into tank until it's dry (aprox 10 min)

After finishing I checked the inside with a small lamp and I noticed that the steel had a orange glow from rust, verry superficial. I also checked it before I started and then the steel was clean but i just recieved it back from hydrostatic testing and they probably thumbled in there.

My question is:
- is this a big problem especially when doing partial pressure mixing or is this normal ?
- how can I prevent this in the future?
- what is the difference between my approach and from a diveshop

Thank you all for your help.

Best Regards,
Duncan
The Netherlands

 

[DA Aquamaster]

It is not an issue in terms of further rust occurring. However it could theoretically be an issue from a particle entrainment standpoint - I prefer my steel tanks to be rust free, not flash rusted when using them for O2 service.

Global makes an O2 compatible rust inhibitor (Compound O) that does a good job of preventing flash rust.

Without it, following a hot water rinse - long enough to heat the tank up - I have had much better luck blowing the tank dry initially with regular air from a scuba tank using a regulator and an LP hose. Invert the tank while you do it and put enough air through it at a high enough flow rate to thoroughly and rapidly dry the tank of any visible moisture. The latent heat of the tank will take care of vaporizng any non visible moisture and then blow the tank out again after 5-10 minutes with scuba air to flush any humidity.

In my opinion, the hair drier thing just keeps the tank warm and moist long enough for flash rust to occur before it significantly dries the tank as there is not enough flow to quickly remove most of the water.

----

Before you rinse the tank with simple green, be sure to clean the threads thoroughly with a toothbrush and simple green to ensure you remove any silicone or other hydro carbons that may be there.

 

[Rick Inman]

...i just recieved it back from hydrostatic testing and they probably thumbled in there.

This I doubt. I've never heard of a hydro place tumbling a tank unless that is something they do and you request it. Otherwise, that is usually a dive shop job.

Some people say that a little flash rust is ignorable and they don't worry about it. It kinda bugs me, so my goal is zero rust, but I won't let a bit of it ruin my day.

I just did a tank Friday and got zero rust, without a rust inhibitor. I rinse with the hottest water I can (I have turned up my water heater). My water goes through a water softener (I read that this helps, but I don't remember why). I keep the hot water going into the tank until the tank is too hot to even touch (got a burn right now on my forearm from accidentally rubbing against the tank during rinsing).

I don't use a hair drier. I use clean air blowing into the tank at high pressure (well, actually I mean I use an LP port from a reg and blast it fast). The moment I stop the rinse, I start blasting that compressed air into the tank, fast.

This seems to work for me.

I also use simple green. Some people also like the rust inhibitor from Global, But I've never tried it.

Also, if I O2 clean the tank, I O2 clean/rebuild the valve. No use having a clean tank and a dirty valve. Of course, then you start filling the tank from sources you can't prove are perfectly clean anyway, but o2 cleaning is a place to start. So I clean my tanks the best I can, and then I fill as if they are always dirty (meaning slooooow).

 

[skdvr]

I see that the OP says he uses Simple Green at 10:1 does anyone else use that ratio? I had always heard 500:1... Just curious what you guys are using???

Thanks
Phil

 

[The Kraken]

What DA said . . .

the K

 

[willembad]

... until the tank is too hot to even touch (got a burn right now on my forearm...

I thought this was a bad thing. Please explain.

Willem

 

[Rick Inman]

I thought this was a bad thing. Please explain.

Willem

Hot water evaporates quickly. The quicker the evaporation, the less rust.

 

[Luis H]

To dry a tank I just use HP air with a 3/8” copper tube at the end of a hose. I put it all together with a yoke adapter some hose fittings and hose clamps. Except for the yoke adapter, everything else is from the hardware store.

The copper tubing gets so cold I have to use a glove to hold it. I also have to be careful with the very cold hose because it can get cold enough to crack.

I will totally dry a tank in about 15 seconds. I started doing that in 1971 at my LDS in Puerto Rico after we hydro tanks. I never understood why other people get flash rust…I have never seen it happen with this method. I thought everyone just air blasted the tanks dry in the same fashion, but I guess it is not common practice.

When I do it, the tank opening points down, but my LDS (and hydro station) here in Maine is now doing it with the tank on its side. The water is just blasted out so quickly that it doesn’t matter if you use hot or cold water.

The temperature of the tank doesn’t really change, but the copper tube gets so cold that any moisture left freezes to it.

I manually move the copper tube around to air blast most of the inside surfaces to help it work faster.

The tanks come out perfectly dry.

I control the flow with the tank valve and I end up using a few 100’s psi, but I don’t need to use a full tank either… I prefer one with 1000 psi or more.

 

[Luis H]

I thought this was a bad thing. Please explain.

Willem

Even boiling water (212 F) is not hot enough to harm a tank…specially a steel tank (aluminum tanks don’t like to see anything above 300F), but you can get burned with temperatures as low as around 150 F.