Proper Tank Storage \ Painting....

[Damselfish]

I wouldn't worry too much about painting your tank as long as you dont have it painted by an auto shop. Spray paint is fine but no heat cured paint according to PSI standards. I also store my tanks at full pressure because I use them regularly and also don't want to miss a dive b/c my tank was at 25, 50, or 100 psi.

the trouble with spray painting a tank is, even if you know it was just spray painted and not heated, an inspector won't and may well assume the worst.

 

[spt29970]

I was talking to my LDS the other day, and one of the guys recommended that I not leave a full tank in my car in the Chicago summer heat for any extended period of time. Better safe than sorry.

I think the reason they were recommending that you not leave a full tank in a hot car, is not so much that you are going to somehow damage the metal, but that the pressure in the tank will increase as it heats up. If you have a good fill and the pressure increases because your car got up to 150F, you could potentially blow the burst disk. It isn't likely, but it is possible.

 

[JSharp13]

I think the reason they were recommending that you not leave a full tank in a hot car, is not so much that you are going to somehow damage the metal, but that the pressure in the tank will increase as it heats up. If you have a good fill and the pressure increases because your car got up to 150F, you could potentially blow the burst disk. It isn't likely, but it is possible.

That is pretty much what they explained. My concern was that my garage may get too hot as well. If it requires 150 degrees or more to be in danger, I think they should be pretty safe there though.

 

[cummings66]

Isn't it something like 7 psi per degree above normal. In this case rough numbers would say that's a 75 degree increase in temp or 525 psi more for 3535 psi in a 3000 psi cylinder. That's under the burst disk pressure. I'd say even 175 degree's would be safe, but to be honest I wouldn't leave mine in those temps for an extended duration with a full fill.

 

[vicdiver656]

Ok I have two questions in one here....

I just bought a brand new Luxfer Aluminum 80 tank... (my first tank ever ) and have been reading some stuff online about proper care and such... Anyway, I read a big article about exploding tanks (which I know it talked about a different type of aluminum that is no longer use) but to say the least it was scary... So its made me want to do everything in my power to properly care for my tank. I understand the inspections, and leaving it with about 50psi when storing it in a cool space in an upright position.

Where my question comes into play is what are the recommendations for how long (maximum) I should keep a tank full. For example, would it be ok to get an air fill a week before I am diving? two weeks? I'm assuming the closest to the dive date would be the best but what is pretty standard out there as I'm new to diving.


My second question is regarding painting. I bought a shiny blue tank and was interested in painting a few fish on there to make mine unique with some of that Scuba Goop paint that i've seen online. I've read some articles about not painting because because of rust being hidden but from what I understand that is refering to fully repainting a tank, not just drawing a few fish and my name on it.

Thanks for the input!

Congrats! I just bought 2 HP 108s, and I was told not to store them at full pressure for a long time, but that it was ok to store them for a month at full, and then maybe just to chuck the air and bleed off half of the PSI, that way there is no danger of explosion.

 

[SlowRain]

I live Georgia...and needless to say it can get warm here as well. My tanks are kept in the garage mainly because one set is 119's and the other 130's both doubles. Needless to say I don't love hauling them any further than I have to! Usually they are both filled at 4000 psi and I have never had a problem. I keep the deco tanks out there as well...again...no problems.

Being that trimix is as expensive as it is...I don't think I would be prone to draining them down. Besides...I dive enough where they aren't sitting full for long anyway.

 

[captain]

The volumn and working pressure of a tank is based on a standard temerature of 70 degrees F. An AL 80 contains 80 cu/ft ( actually closer to 77 cu/ft) at 3000 psi @70 F and is considered to be full. If the temperature is raised to 150 F then the pressure would be 3448 psi but the tank still contains 80(77) cu/ft and it is not considered over filled. Let's say your LSD fills your tank to 3000 psi on a 90 degree day and a cold front passes the next day and now the temperature is 70 F. Your tank pressure is now 2891 and it is under filled by 109 psi and you have 77.1 cu/ft of gas. Actually closer to 74 cu/ft because an AL 80 will actually hold only about 77 cu/ft at 3000 psi @ 70 F. The lesson is the closer the tank is kept to 70 F during filling the closser to full it will be. By the same token it is OK to pressure a tank (notice I didn't say overfill ) to 3100 psi or 3150 psi if it is being filled at a temperature of 90 F or 100 F.

 

[Bratface]

I wouldn't bother painting the tanks. All the painted tanks that I have seen have chips in them. Unfortunately, my steel 80 is painted, so I suppose eventually I will have to deal with chipped paint myelf.

 

[spectrum]

No good can come from painting a cylinder. The exception is a cold galvanizing finish to patch a galvanized finish blemish.

Anything you put on there will eventually be scuffed or scrapped and water and all that it brings will work its way under the finish where it's nearly impossible to rinse off and will result in corrosion to a cylinder of any material. Besides if you actually dive home painted cylinders they will soon look like crap.

My understanding of cylinder storage preferences is either full or hear empty (500 PSI or less) In the event of a fire a full cylinder will probably trip the burst plug before catastrophic failure. An near empty one will probably have a more benign failure, if it fails at all. However a mid fill is very unpredictable. All of this is of course based on a multitude of variables so take it with a grain of salt.

Aluminum cylinders can suffer from sustained load cracking and for this reason a low pressure off season or layup storage method is preferred. Most of this is based on then old 6351 cylinders and is a minor consideration otherwise.

As far as intervals I wouldn't think of anything in weeks. Opinions are all over the board but I don't think twice about diving a fill from 6 months ago.

Pete

 

[Doc Harry]

Isn't it something like 7 psi per degree above normal. In this case rough numbers would say that's a 75 degree increase in temp or 525 psi more for 3535 psi in a 3000 psi cylinder. That's under the burst disk pressure. I'd say even 175 degree's would be safe, but to be honest I wouldn't leave mine in those temps for an extended duration with a full fill.

I don't have my references available, but doesn't exposure to a temp of 180 degrees F condemn an aluminum cylinder?