Opinions on 2 year old cylinder failed visual for pitting

[Spg01]

Wet fill bath: Yes

Boat fills: No
Any of the boats when I dove doubles I either borrowed a set of doubles and or brought stages. I was mostly shore diving.

 

[underH2Oman]

The only way for water to get into a cylinder if it does not run empty is during the filling process when more air is added.
It could come from the compressor as mentioned above. It could also be that there was a little water sitting in the valve prior to being filled.
This can occur if;
-tanks sit in the bed of a pickup or outside and get rained on
-sit in the same open truck or outside over night and the temperature drops causing water to condense on them as the air warms
and get filled before they dry.

I think I would have been concerned the first year if they needed tumbled. I have had cylinders not needing tumbled for well over 10 years.
You have not had any problems with other tanks filled at this location. That would make me ask why?

In regards to running away or not, I would have a face to face talk (not argument) with the owner and see if he is willing to help you out in some way.
Keep in mind we all like to find the root cause and associate blame but that is not likely to happen here.
Like you he may not feel responsible. If you are the only person with this issue he may see it as happening outside of his store. After all he does not follow you around and even though you know that that is the only spot you get fills how does he? One bad fill elsewhere could have been all it takes.

I hope you can reach a mutual understanding and fix the issue. I would also contact Worthington directly. they do not make scuba cylinders but they are still in business and may help you out?

 

[cool_hardware52]

The only way for water to get into a cylinder if it does not run empty is during the filling process when more air is added.
It could come from the compressor as mentioned above. It could also be that there was a little water sitting in the valve prior to being filled.
This can occur if;
-tanks sit in the bed of a pickup or outside and get rained on
-sit in the same open truck or outside over night and the temperature drops causing water to condense on them as the air warms
and get filled before they dry.

I think I would have been concerned the first year if they needed tumbled. I have had cylinders not needing tumbled for well over 10 years.
You have not had any problems with other tanks filled at this location. That would make me ask why?

In regards to running away or not, I would have a face to face talk (not argument) with the owner and see if he is willing to help you out in some way.
Keep in mind we all like to find the root cause and associate blame but that is not likely to happen here.
Like you he may not feel responsible. If you are the only person with this issue he may see it as happening outside of his store. After all he does not follow you around and even though you know that that is the only spot you get fills how does he? One bad fill elsewhere could have been all it takes.

I hope you can reach a mutual understanding and fix the issue. I would also contact Worthington directly. they do not make scuba cylinders but they are still in business and may help you out?

So let's we have a couple drops of water in the valve, can't ve much more than that as the orifice to valve seat passage ways are pretty small.

Now lets say we force those "couple drops" into the cylinder with ~80-100 cuft of air dryer than the most arid desert on the face of the planet.

What now happens to these "couple" drops of moisture? They instantly flash into vapor and increase the moisture content of the tank almost not at all......

Do I blow out my valves before I fill? Of course, but the chances that not doing so will contribute enough water to rust a tank to the point of pitting failure is pretty damn remote IMO.

Tobin

 

[Wookie]

Had a boat divemaster come to me to have his cylinder replaced. This guy was in my crew. He was diving a steel 95, I was using my HP100. He had been trained by my lead DM how to fill tanks, which includes blowing out the face of the cylinder every fill, and blowing out the whip EVERY FILL.

Fella came to me with a failed steel 95. Completely rusted out with pitting rust. I asked him who filled his tank, he replied that it was only ever used on my boat, and I must have a failed air system. He always filled his own cylinder. I replied that my wife always filled my cylinder, and that I dove far more than he did, would he like to compare mine to his. Why yes, he replied.

The inside of my cylinder looked brand new. His was pitted out. It has to do with who is doing the fills, and how they treat your cylinder. That's why I asked if it was filled in a water bath. I don't care if the whole thing is underwater once the whip is pressurized, but if the face has one droplet on it, or the whip has one droplet in it, and that drop atomizes when it enters a tank, it will destroy a steel in a very short time.

A water bath is unnecessary. I don't care how fast you jam a tank, you can't get it above 300 degrees, so you aren't going to stress the tank. I also don't care how cool you keep the tank when you fill, it's the air that heats up and then the pressure contracts as the air in the tank cools. Keeping the cylinder cool while filling does nothing to ensure a full cylinder, but you can't tell anyone that, it flies in the face of "common sense". The only way to get a full fill is to fill slowly. Filling in a water bath only serves to get water in a cylinder, as I suspect happened here.

7 years later, my cylinder still looks brand new. I am always amazed how good a steel cylinder can last with a small amount of care.

 

[cool_hardware52]

One eyedropper (1/20cc) of water in a typical HP 100 is 4.1 x 10-6th or .0000041 of the volume of the cylinder, or .00041%

ANDI oxygen compatible air allows 128ppmv or .0128%

Kinda hard to see how a drop is going to pit a tank.

Tobin

 

[Wookie]

One eyedropper (1/20cc) of water in a typical HP 100 is 4.1 x 10-6th or .0000041 of the volume of the cylinder, or .00041%

ANDI oxygen compatible air allows 128ppmv or .0128%

Kinda hard to see how a drop is going to pit a tank.

Tobin

Fill it 60 or 100 times. It will, however, make the most amazing pattern of flash rust, that one drop.

And, the OCA spec is based on water entrained in the air. Blowing a drop of water in does not usually entrain the water, but smears it on the wall of the cylinder. Then the water does entrain in the gas, assuming the relative humidity of the gas is far less than the dewpoint, which I would hope at 128 PPM it is. Still, the tank starts to rust from the top down as more and more water is introduced, and on a boat, the salt crystals (usually it would be salt water introduced during filling) plate out on the walls of the cylinder.

You are much more of a materials engineer than I am, but salt in a high oxygen environment would yield lots of rust regardless of the presence of water, no?

 

[cool_hardware52]

Fill it 60 or 100 times. It will, however, make the most amazing pattern of flash rust, that one drop.

Flash rust maybe, but pitting implies free water, not a tiny percentage of vapor. As I stated the moisture will immediately flash into vapor.

Tobin

 

[kwinter]

The OP can't possibly be the only guy with steel tanks getting fills at that shop. This kind of thing doesn't happen from a single bad fill. So either every other steel tank they fill is facing the same fate, or something is wrong with the "facts" presented. And since he probably would have heard about other people suffering the same fate, then there is something else wrong.

Or maybe I'm just too cynical.

 

[cool_hardware52]

The OP can't possibly be the only guy with steel tanks getting fills at that shop. This kind of thing doesn't happen from a single bad fill. So either every other steel tank they fill is facing the same fate, or something is wrong with the "facts" presented. And since he probably would have heard about other people suffering the same fate, then there is something else wrong.

Or maybe I'm just too cynical.

Maybe, but it could also be a bit of bad luck. The tanks filled when the desiccant has not failed would be ok, and the guys that dive 4 times a year may not be having tanks condemned.

The frequent diver runs the greatest chance of getting fills when the desiccant is spent.

Tobin

 

[underH2Oman]

So let's we have a couple drops of water in the valve, can't ve much more than that as the orifice to valve seat passage ways are pretty small.

Now lets say we force those "couple drops" into the cylinder with ~80-100 cuft of air dryer than the most arid desert on the face of the planet.

What now happens to these "couple" drops of moisture? They instantly flash into vapor and increase the moisture content of the tank almost not at all......

Do I blow out my valves before I fill? Of course, but the chances that not doing so will contribute enough water to rust a tank to the point of pitting failure is pretty damn remote IMO.

Tobin

A little water can make a difference. here is an article from Moisture In SCUBA & SCBA
It talks about moisture in a scuba tank. When we are talking PPM a drop represents a lot of moisture.

Understanding Dew Point & ppm moisture​

This topic is very complex; we will discuss just the basic parts. The term Dew Point is the temperature at which the gas can no longer hold the moisture in the evaporated state, but causes it to spontaneously condense onto surfaces or remains suspended as micro droplets. Moisture is expressed in three ways: Dew point (in degrees Fahrenheit or Celsius), parts per million by volume (ppmv) and mg/cubic liter.
If you have air that has a dew point of -65ºF at one atmosphere pressure, the water content will be 24ppmv, and the air is considered dry. If you then charge a SCUBA tank to 3100psig with that same air, the moisture content will still be 24 ppmv, but because the water and air molecules are now compressed together, it is easier for the water molecules to "stick" together and condense onto the cylinder walls. If you measure the dew point of the air in that cylinder at the 3100 psi pressure, you would discover that the dew point inside the cylinder is now +28 ºF (that dew point is called the Pressure Dew Point). That means that if the outside temperature becomes colder than +28ºF, the compressed air in the cylinder will condense onto the SCUBA flasks interior walls.