Dry Fill?

[ScubaKris]

I've lived and dove the mid west,...and sorry,..it sucks. If I were to spend my life there I would find anohter sport

 

[rjack321]

could fill a tank about as fast as you would want. We used a steel tank surrounded by concrete filled with water and we could fill 8 tanks at a time. In terms of the amount of time it took to fill a tank it was a judgement call. I guess each set took about 5 minutes to fill. Standard practice at the shop was to overfill by about 200 psi. I had few complaints about underfills. I can't speak to what effect this had on the life of the tank.

200 psi over sounds fine to me.

But that steel tank with concrete would probably make matters worse not better in a tank explosion. There's got to be a safe place to disperse the energy. Blast cabinets have to be designed, otherwise you end up making explosions worse. In this case, you'd probably get a whole lot of shrapnel, which cylinders are themselves designed not to generate. If the sides didn't blow out, the force would instead be directed upwards - towards your torso when you were working.

 

[Thalassamania]

We ran some tests on heat transfer to the water bath, it just does not happen to any significant degree in the time it takes to fill a tank (e.g., 10 minutes).

As for painting tanks, this comes from two places. The first is the expoxy coating on steel tanks that was tried for some year, water would get under the coating and you could not see the rust. The second was the problem when some powder coated aluminum tanks (they were baked to get the finish smooth) blew while being filled in a shop. I don't remember, but I think that someone was killed in that one.

Anyway, the idea that you never paint a tank entered the scuba collective unconscious and has been there ever since. I’ve painted many tanks with a spray can of Rustoleum or Krylon, without ever having a problem.

 

[FredT]

A dry fill in a proper containment baffle is probably the safest way to fill tanks irrespective of speed. This is especially true if filling "unknown" tanks.

A proper baffle has enough opening to allow rapidly expanding gas to vent in a safe direction, while containing the fragments of a failed tank. Generally this will be constructed of A-36 mild steel plate, or M1020 hot rolled flat bar not thicker than about 5/16". The plate is generally softer than the tank material, so when impacted by tank parts the baffle deforms to absorb the energy from the schrapnel, not simply redirect the schrapnel to a new target as a thicker or higher strength baffle would do.

A wet fill tank simply effeciently transfers expanding gas energy to water, then the water and schrapnel damges the shop and those in it.

I do however see very few effective baffle systems, but a bunch of water tanks, at dive shops. Of course an old horse trough is a lot less expensive up front than a baffle.


As to the "don't paint Worthingtons" instructions I'm afraid that probably came from me. I did some consulting with the folks developing the coating and explained that the effectiveness of a galvanized finish is directly related to the relative exposed surface areas of zinc and other metals involved. If you need to mark your tank with paint simply do a lousy job of painting if. If the coating is very porus the galvanizing is still working. For example a standard spray paint often calls for a 10" distance between the can and the surface to be painted. Extend that to 16-20" and put just enough paint on the tank to give is a "gost" of the marking color. Shiney hard paint coatings over galvanizing is a bad thing.

For visibiliy issues get a roll of sefl adhering SOLAS tape from 3M and put a 1" band of it just above where your upper tank band circles the tank. Don't use more as it's not needed for visual reflectance, and the stuff is expensive. It will need to be removed every year for the visual anyway. OTOH a strip of it my save you if lost off the SE FL coast since the condo lighs will bounce off it several miles to sea. Better yet is to sew it onto your harness at the top of your shoulders.

FT

 

[tankboygreg]

As for painting tanks, this comes from two places. The first is the expoxy coating on steel tanks that was tried for some year, water would get under the coating and you could not see the rust. The second was the problem when some powder coated aluminum tanks (they were baked to get the finish smooth) blew while being filled in a shop. I don't remember, but I think that someone was killed in that one.
QUOTE]

I had forgotten about epoxy coated tanks.

What used to scare me is that some tanks would have, not a burst disc, but a lead plug! I felt like had a gun pointed at me. Then there were the burst discs that didn't have the side vents. I had one go off and start bouncing around the parking lot. Luckily, the valve didn't break.

 

[Dive-aholic]

...If I was a cave diver, I'd go there to get a lot of air, and screw the life of the tank...

You're opening up a whole new can of worms here. "Cave fills" may "screw the life of the tank", but none of us will get enough fills in our life times to see that effect.

 

[MrBill_FTL]

can you see the gps? its on.....

few nice bugs of ft lauderdale today. as sportsman season started at midnight.

there at least one big one still out there... and hes really fast! lol.


Oh, I could only get a 3000 fill at the beach dive shop... on the new HP 100.....
something about chaning the setting was a pain.....

 

[CompuDude]

That does it, I'm off to lunch... thanks for the reminder!

 

[Tagerisatroll]

200 psi over sounds fine to me.

But that steel tank with concrete would probably make matters worse not better in a tank explosion. There's got to be a safe place to disperse the energy. Blast cabinets have to be designed, otherwise you end up making explosions worse. In this case, you'd probably get a whole lot of shrapnel, which cylinders are themselves designed not to generate. If the sides didn't blow out, the force would instead be directed upwards - towards your torso when you were working.

Honestly I think most fill setups are flat wrong they require the operator to lean over the tanks to reach the valves that control the fills, a very dangorous situation. The dive shops should really take a hard learned lesson from the tire industry and take a step back when the tanks are being filled, not be right over them. The tanks should be to the side and the controls of the fill should be were the operator can reach them without ever having to lean directly over the tanks. Safety in desighning tank fill area's hasn't been thought out very well, in most shops. I tend to hang out on the other side of the shop while mine get filled.

 

[Thalassamania]

Some of us are bit older and haven't lost all our marbles (yet<G>).