Internal tank lining?

[MisterEd437]

I’m building a hookah system (no oil compressors) but was wondering if there was any product that can be used to coat the inside of the three tanks I’m using to store air. There are two 3 gallon tanks that are steel and store the initial air coming out of the 12v compressors. The third tank is 4 gallons, made of aluminum and floats in the water to cool the incoming air from the two compressors, this tank feeds the diver. I know they make a ceramic liquid used to coat the inside of motorcycle gas tanks but can find nothing about the breathability of this coating. Wondering if anyone knows of a safe product to use?

The air intake for the compressors is run through carbon filters followed up by each having their own moisture filer which is rated at 5 micron for particulates. There is another 5 micron filter 3’ from the regulator for addition protection from any debris in the breathable approved hose.

 

[tmassey]

I’m not familiar with the products you’re talking about, but I can say this: in the 1970s, scuba tank manufacturers experimented with liners. They were singularly bad ideas, they quit using them, and today tanks that have the linings are pretty much reviled (hated). If people don’t just straight-up scrap them, they spend a lot of time and effort grinding out the lining to get back to the raw steel.

Basically, you need to make sure the air going into those tanks is clean and dry. Not because of the tanks, but because as a SCUBA Diver, you need to be diving and breathing clean and dry air.

So, if you put the work into supplying clean and dry air to the diver, the tanks get clean and dry air for free. Do yourself a favor: fix your air supply, not the tanks.

ETA: if the air going into your tanks is so bad as to require a lining for the tanks, do you really want to be breathing that air?

 

[tursiops]

Why do you need to coat the tanks on the inside? Steel tanks are commonly used today for scuba with no coating.

 

[MisterEd437]

Why do you need to coat the tanks on the inside? Steel tanks are commonly used today for scuba with no coating.

Scuba tanks are of a higher quality than air compressor tanks. Even after cleaning, I though a nice coating would help eliminate any issues.

 

[tursiops]

Scuba tanks are of a higher quality than air compressor tanks. Even after cleaning, I though a nice coating would help eliminate any issues.

That's what scuba tank manufacturers thought many years ago, too. They don't do it any more. Caused more problems than it might have solved.

 

[Invader]

It used to trap corrosion beneath any tiny issue in the coating, preventing the air from drying it out. I just cleaned out 7 LP72s of liners. What was underneath was mildly concerning if it was left alone.

 

[MisterEd437]

That's what scuba tank manufacturers thought many years ago, too. They don't do it any more. Caused more problems than it might have solved.

Thanks for that information. I got a hold of an air technician (another occupation I never heard of!) who does all the testing and maintenance of hospitals air systems. He was in agreement, the linings often pealed of the tank surfaces. I showed him my intake carbon filters plus the other in-line particle filters and he thought it might be over kill. He recommended a bigger water separator instead of two small water filters since, according to him, larger water separators filters perform better than smaller ones.

 

[rjack321]

There should be drains in the tanks for you to drain/evacuate the (liquid) moisture at the end of each dive day. Those little moisture separators won't do a whole lot.

 

[MisterEd437]

There should be drains in the tanks for you to drain/evacuate the (liquid) moisture at the end of each dive day. Those little moisture separators won't do a whole lot.

Yes, each of the three tanks have relief valves as well drains. We let the compressor go to about 30 pounds and open the drain values in turn. On the next use, we plan on capturing some of the air and have it tested - just for safety and knowledge sakes.

 

[Eric Sedletzky]

There is an epoxy mastic material 1:1 true epoxy similar to something like liquid JB weld that is fluid and they pour it into tanks and slosh it around hoping that it coats every square millimeter. But the problem is residual amines for breathing. For gasoline who cares, but for breathing gas no way.
You would have to vent it and run clean air through during the entire catalyzing process and make sure it's 100% gassed out. Not worth it.
Just go with clean steel, less is more.
It also might help if you can mount your steel tanks upside down somehow, valve or manifold down that way any moisture doesn't puddle up on the bottom of the tanks, if there is any?
Breathing a little moisture won't hurt as long as it doesn't have any vaporized hydrocarbons from oil, but you're using an oil-less diaphragm compressor so you should be fine.