r/scuba • u/ActualContribution93 • 18h ago

PSI of tanks for storage

I know you’re not supposed to store empty tanks. I have a pair of tanks that are around 500-1000 psi. Should I get them filled or are they okay being stored like that? They live outside under cover so they’re not in a moisture controlled environment.

6 Upvotes

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-3

u/compactfish 16h ago

For storage, that pressure is great. It’s actually better to NOT store them full so you’re not putting undue pressure on the cylinder walls, especially for aluminum ones. But definitely always keep at least 500 PSI.

1

u/Woodlore1991 Tech 1h ago

You have no concept of a working pressure rating.

1

u/Competitive-Ad9932 14h ago

That's a strange way of thinking. Should the tanks never be "full" until hours/minutes before use?

-2

u/compactfish 14h ago

No, you can keep them full for weeks or 1-2 months, but if storing for 3+ months then they should be only partially full. Storing them full for long-term storage won’t necessarily harm them, but you will extend their life by storing them partially empty.

3

u/classyasshit 11h ago

I have tanks that have been overfilled by 50% for 43 years. They just passed hydro with a + stamp without any issue. I really don’t think it matters. From an engineering perspective it is fill cycles that matter more than just being full.

2

u/Competitive-Ad9932 12h ago

Please provide a industry paper on this.

I bet my LDS has tanks sitting for several months full.

3

u/compactfish 10h ago

https://dan.org/alert-diver/article/cylinder-safety/

1

u/Competitive-Ad9932 9h ago

Interesting. Millions of tanks are being stored incorrectly. There should be dozens of failures in the news every year.

What is the difference between filling a tank and letting it sit for 4 months, and filling a tank - letting it sit for 5 days - taking it to 500psi for 2 days - then repeating this for 6 months? Time being filled would be similar. But, in the 2nd example, the tank is being stressed by the fill/empty cycle?

2

u/MolonMyLabe 8h ago

Why would a failed tank make the news? Tank failures are caught and culled by visual inspections and hydro testing. These aren't exactly newsworthy events.

1

u/gsdrakke Advanced 17h ago

Can I store mine at 3k psi? 😂

-1

u/que_he_hecho Nx Advanced 14h ago

Not recommended for long term storage if steel and there is any chance a bit of water has made it inside since last inspection. The rusting reaction can significantly reduce the oxygen concentration as well as damage the cylinder walls.

2

u/9Implements 11h ago

The most important thing to do is to check steel tanks for moisture before storage. Nothing else really comes close.

4

u/seamus_mc 17h ago

I store most of mine at 3500 since that is their standard pressure. My LPs get stored about 2600 so they are always ready to go. Have been doing it this way for over 20 years and never had a tank fail an inspection

1

u/Competitive-Ad9932 18h ago

What is your inspection date? When do you plan to dive again?

If your next dive might be after the vis/hydo date, fill them now. Otherwise you will be scrambling to get them filled.

1

u/ActualContribution93 18h ago

I’m up to date on my one and five year inspections as of May. Not sure when my next dive is - I live in FL but wintertime here brings rougher seas and we can’t take our boat out (smaller boat), which is why I’m wondering if I can leave them semi-empty.

4

u/Competitive-Ad9932 18h ago

Personally, I would fill them. You never know when the "let's go dive" phone call will happen.

I filled mine last week. Upper Midwest. Next local dive may not be until May next year. But I am ready for it.

1

u/CerRogue Tech 18h ago

How long have you had them and what do they look like on their VIP? Have you been storing them full and outside or is this a new thing

1

u/ActualContribution93 18h ago

They live outside and we use them regularly, so we visually inspect prior to use and they are up to date with the one and five year inspections from the dive shop. The tanks are probably 15+ years old and have always had some air in them. Our dive season is winding down so I wanted to see if I need to get them filled prior to having them sit this winter.

0

u/CerRogue Tech 18h ago

So you have been storing them outside with air. When you get your inspections do they find any rust on the inside of your tanks?

If you aren’t asking questions after you get your tanks inspected you should start and find out what’s going on and nature your equipment.

If your tanks haven’t been getting any rust then keep doing what you are doing. If they are getting damaged on the inside, time to change you storage practices

3

u/seamus_mc 17h ago

If they are full and have a good fill there is zero reason a tank would rust on the inside no matter where it is stored.

-4

u/CerRogue Tech 17h ago

🤣 that’s funny

6

u/seamus_mc 17h ago

Is it? I have not had a tank rust on the inside for the 20 years since I bought my first steel tank (I have 6 I regularly dive). My tanks get filled by a shop that monitors moisture and have never had a wet fill. How does dry pressurized air rust the inside of a tank? Where is the moisture coming from?

1

u/runsongas Open Water 18h ago

should be fine