How Clean Should an Air Tank Be

[chrpai]

I have an LP95 that I just sent off for a hydro to get a + rating. When I took the valve off, I stuck my finger inside the opening and took a swipe. My finger came out fairly dirty.

How clean should the inside of a tank be if it's not going to be used for anything other then air?

 

[bletso]

It sounds like they dried the cylinder with air and you have a load of flash rust. (if your finger was rusty colored) Even for air it could be a problem if it clogs the regulator sintered filter. (Some flash is acceptable. Get your LDS to look inside.)

Dale

 

[Dr. Lecter]

Depends on what you want to breathe into your first stage filter and lungs, no? If the inside isn't shiny and clean, I'd personally want the tank lightly whipped/tumbled with some dawn or simple green, rinsed thoroughly with fresh hot water, and then properly dried. But I doubt some dust stuck on the interior of the tank is doing much harm to you or the reg.

 

[chrpai]

Sorry if my writing wasn't clear... I've just sent it off for hydro and this was a pretest check. My finger was a sooty grey. I probably won't get the tank bank from hydro until some time next week.

 

[bletso]

sooty grey is not good. It may or may not come back any cleaner unless you ask them to clean it.

Dale

 

[halocline]

I bet it's old grease from the threads of the valve; people over-lube those occasionally. Whatever it is, I'd clean it pretty thoroughly when you get it back, rinse with hot water if you can, and blow dry with scuba air from another tank. Just take a full tank, put a first stage on it, attach a LP hose with no 2nd stage, insert the hose in the wet tank and blast away.

 

[ajduplessis]

Cylinder neck opening sometimes have lubrication that can dirty them up. Do a quick visual yourself. IMO cyclinder gas ends up in your lungs, thus the cylinders must be spotless.

 

[bletso]

I had forgot about lube on a steel tank. I never lube the threads on my steel cylinders. Yes, the lube will migrate down a little as the cylinder heats up at fills. Yes, it is also my experience that most shops place way too much lube on valve threads. All it takes is a pea size drop, if any at all. I don't know where the custom of using it on SCUBA originated, but we use none at all on industrial and medical cylinders. In theory it is to prevent galvanic corrosion between the plated brass valve and the aluminum cylinder. However to have galvanic corrosion take place you must have moisture. SCUBA air is supposed to be dry and the cylinder is to always have positive pressure, so....

As mentioned get some simple green or dawn, hot water and a tooth brush. I prefer N2 as it will prevent flash rust. To dry the cylinder fast, it is the best way to use hot water to heat it up.

Dale

 

[rjack321]

As others have said, its probably silicon or cristolube on the neck threads. The best thing to remove the excess is a couple of paper towels swiped through the threads. You'll see grey goop on the first couple swipes then progressively cleaner. Repeat on the valve threads. You don't need much lube on those threads and its frequently over-applied. The threads don't need to be spotless (and they rarely are). "Too much lube" is rather subjective though.

 

[KD8NPB]

Compound B, an anti-flash rusting liquid applied after tumbling or hydro, tends to leave a residue.

It could also be dirt/particulate leftover from the hydrostatic testing water.