My Steel HP100's have surface rust, WTH?

[Scott L]

Tobin hit the nail on the head. Moisture in a tank comes from poor filtration.

Remember from your open water class that ambient pressure in psi underwater is roughly equal to half your depth in feet (0.43 psi per foot in sea water). For water to enter your tank when it has 500 psi in it would require you to be at about 1000 ft depth.

Some flash rust will not cause it to fail a visual inspection, although if you listen to some LDS's, any flash rust requires a tumble.

There are various ways to remove flash rust without tumbling, whipping or sandblasting.

When flash rust appears I beleive tumbling is the remedy although I am far from the authority. I defer to Tobin in these matters...

 

[cool_hardware52]

When flash rust appears I beleive tumbling is the remedy although I am far from the authority. I defer to Tobin in these matters...

I'd suggest listening to Leadking. He knows a thing or two 'bout tanks.

Tobin

 

[Gilldiver]

While filtration failures are a very common problem. Water breakthrough is somehting to be aware of when getting fills on boats or at shops where the humidity is high for long periods of tim, the islands, Southern US and Central America, or when a compressor has not been run for long periods of time.

But the major source of water into a tank that I have seen is either poor diver practice - draining a tank dry in the water, or poor fill practice. Poor filling is when the shop monkey does not make sure that the valve is dry before puting the fill whip on. DIN valves are especialy prone to this as the femail valve will hold a good amount of water compared to a Yoke valve. Good fill practice is even more important when doing wet fills as water can very easily get to the valve opening.

As for flash rust, the shops seem to have become totaly intollarent of any rust and tanks are being tumble when they don't need to or a quick whip would do the job.

 

[drbill]

A few boat fills are enough to get water in your tanks. I've had two PST HP120 tanks fail.

For the LDS to say that hot fills don't affect the integrity of the tank seems to be utter nonsense. My first PST tank failed due to over expansion believed to be caused by MANY hot fills at a certain LDS. Even the manager of that LDS said it was probably the cause.

 

[cool_hardware52]

A few boat fills are enough to get water in your tanks. I've had two PST HP120 tanks fail.

For the LDS to say that hot fills don't affect the integrity of the tank seems to be utter nonsense. My first PST tank failed due to over expansion believed to be caused by MANY hot fills at a certain LDS. Even the manager of that LDS said it was probably the cause.

The tempering temperature for CrMo Steel starts at about 750 degree F and range upto about 1050 degrees F. The tank neck Oring would cook off at temperatures well below this point.

It is my opinion that it is virtually impossible to affect the properties of a 3AA Scuba tank via "hot fills"

PST tanks have "special" hydro requirements, some would go so far as to say PST unfairly "games" the system with their recommended hydro protocol.

There are many reports of PST cylinders failing their first hydro.

For most hydro stations scuba tanks represent a tiny fraction of the bottles tested and often any special requirements are either unknown or ignored.

Tobin

 

[redacted]

But the major source of water into a tank that I have seen is either poor diver practice - draining a tank dry in the water, or....

While it is possible to get water in a tank in that manner, it seems that it would be pretty hard. The diver would not only have to empty the tank, but he would also have to pull a vacuum (or descend with the empty tank) to creat the opportunity for water to enter the system. Then there would also have to be an opening for the water to enter, either a failed seal, an activation of a purge button, or a 2nd stage with a seat saver feature. And it the opening is in a 2nd stage, that water would have to travel through hoses and the 1st stage to make it to the tank.

I tend to doubt that this is a common source of water in tanks.

 

[mustang_5l]

Tobin hit the nail on the head. Moisture in a tank comes from poor filtration.

+1 I totally agree

 

[NJDiver07866]

Pete hit the nail on the head....

I need to whip/mop every 3 years.. just the nature of the beast... If you have to get it done every VIS then something is up.....

From pete.....
Over what period were the 100 dives made? Over time most steel cylinders will develop some flash rust that can eventually be of concern to the inspector. Spinning a tank whip, blasting or tumbling are not all that uncommon with cylinders that actually get to go diving frequently. To some extent it's expected maintenance. If it were a yearly need I would raise a red flag.

 

[letterboy]

Quite true. Check out this resource for the argument for and against wet filling/dry filling. Fill Express in Ft Lauderdale, FL is an industry leader in technical scuba tank filling.


Fill Express -- FAQ About Filling SCUBA Cylinders

[offtopic]
Interesting snipette from FE's site

Will you fill my cylinder to more than its rated maximum pressure?
Fill Express does not overfill any aluminum cylinder. Overfilling shortens cylinder life, as well as increases risk of cylinder failure. Increased pressures also can cause burst disks, O-rings, and 1st stage regulator seats to unexpectedly fail prematurely. Willing to accept these risks in exchange for the increased gas volume, technical divers sometimes overfill their recently manufactured chrome-moly steel cylinders.

they say they won't over fill AL, but don't say they will or will not overfill steel . . .

[/offtopic]

 

[Reef]

Thanks for all the input. Wow. You guys/girls rock.

I dropped 2 more tanks off at lunch. One was clean, and the other had 2-3 spots in it. They said no big deal. Next year at this time I guess I'll get them tumbled.

Will tumbling affect hydro???