Long term issues with overfilling steel tanks?

[MaxE]

I have found some used tanks for sale, the seller claims they are LP steel, rated for 2400psi. They also claim they were filled to 3000psi and never touched for 7 years. I'll assume they were + rated so 2640 would be ok, I can further hope they were hot fills so not really filled to 3000psi. Are there any potential effects on the tanks being filled to 3000 and sitting for so long? They will need a hydro and I don't want to but them only to fail.

 

[2airishuman]

They should be fine.

While I don't necessarily endorse the practice, it is common for LP steels to be overfilled in some areas and among some dive communities. Actual problems are vanishingly rare.

 

[Lorenzoid]

I don't know to what extent this may be a factor in judging the condition of the tanks, but as I understand it, it's not so much the overfilling itself that stresses the metal as repeated cycles of overfilling and emptying.

And as 2airishuman mentioned, LP tanks are routinely filled to upwards of 4000 psi in places like N. FL cave country, and they somehow make it into their senior years, passing hydro multiple times.

 

[teknitroxdiver]

LPs in cave country get hundreds or thousands of fills to 3600+ and have no problem passing hydro for decades. I believe OMS used to advertise "10,000 fills to 4,000psi" for their LP tanks, and real-world usage has proven that to not be an overstatement.

 

[bamafan]

The only thing I would worry about is rusting and pitting. If they have boots look under them and if possible look inside the tanks. Most buyers will guarantee they will pass vip & hydro.

 

[tbone1004]

I have found some used tanks for sale, the seller claims they are LP steel, rated for 2400psi. They also claim they were filled to 3000psi and never touched for 7 years. I'll assume they were + rated so 2640 would be ok, I can further hope they were hot fills so not really filled to 3000psi. Are there any potential effects on the tanks being filled to 3000 and sitting for so long? They will need a hydro and I don't want to but them only to fail.

they're fine. Aluminum tanks are good for like 100k fills to their hydro pressure of 5000psi, and steel deals with overfilling much better than aluminum as well as long term storage at working pressure. Nothing negative will happen to those bottles from filling to those pressure, even daily filling to 4k for 20 years won't both LP steels. Ask some of the old timers in Florida....

what @bamafan is right, especially if they're Fabers and have boots on them as that's going to be the spot where damage is going to occur. If they aren't booted, just pop the valve off and have someone you trust do a VIP on them and you'll be good to go

 

[HalcyonDaze]

LPs in cave country get hundreds or thousands of fills to 3600+ and have no problem passing hydro for decades. I believe OMS used to advertise "10,000 fills to 4,000psi" for their LP tanks, and real-world usage has proven that to not be an overstatement.

Good to know - I have a pair of LP 120s that I picked up cheap (read: pay for hydro and viz) last year; once or twice I might have gotten a fill that went up to about 3k when hot but otherwise I haven't really pushed them past 2600. The other week I took them into a different shop for a VIP and O2 clean (last time they only gave me a 40% sticker, which was problematic at one shop where they did partial pressure blending), and they assumed the tanks were HPs. So right now I've got a pair of 2400 PSI-stamped tanks sitting in my living room that are reading 3500 psi at ambient temp.

 

[guruboy]

The other week I took them into a different shop for a VIP and O2 clean (last time they only gave me a 40% sticker, which was problematic at one shop where they did partial pressure blending), and they assumed the tanks were HPs.

Are you sure the first shop did the O2 cleaning? Banked 40% doesn't require any cleaning at all.

 

[northernone]

Good to know - I have a pair of LP 120s that I picked up cheap (read: pay for hydro and viz) last year; once or twice I might have gotten a fill that went up to about 3k when hot but otherwise I haven't really pushed them past 2600. The other week I took them into a different shop for a VIP and O2 clean (last time they only gave me a 40% sticker, which was problematic at one shop where they did partial pressure blending), and they assumed the tanks were HPs. So right now I've got a pair of 2400 PSI-stamped tanks sitting in my living room that are reading 3500 psi at ambient temp.

That's what I call a good fill. Enjoy.

Disclaimer: your attitude and assessment of the risks of a cave fill are up to you and the fill station.

It's possible the first time you didn't get an o2 clean. Some shops do a 'nitrox clean'. Another thought. Do you know if the burst disks are fairly new, an aging (rusted) disk can fail at lower than rated pressure.

Regards,
Cameron

 

[HalcyonDaze]

That's what I call a good fill. Enjoy.

Disclaimer: your attitude and assessment of the risks of a cave fill are up to you and the fill station.

It's possible the first time you didn't get an o2 clean. Some shops do a 'nitrox clean'. Another thought. Do you know if the burst disks are fairly new, an aging (rusted) disk can fail at lower than rated pressure.

Regards,
Cameron

The valves are less than a year old; the original ones on the tanks were yoke-only. I ended up getting a DIN reg, so I had them install new Sherwood DIN valves with inserts. I'm still a bit concerned as the burst disks are labeled 3000 PSI.

As far as the O2, what happened was the last shop put stickers on that said the cylinders could be filled with up to 40% O2. That wasn't an issue until I tried to get fills at Force-E up in Riviera Beach, which uses partial pressure blending rather than banked gas. They insisted on pulling off the valve and checking the lube/o-rings before every fill; apparently they were satisfied with what they found but it was a bit of a pain to deal with. I figured this time around it was best to get the proper labeling on the tanks so I could get them filled anywhere.