Overfilling steel tanks

[UWSojourner]

Thanks for the info. I don't have a 50 plus year useful life so who cares about my tanks!

2640 psi is with the 10% overfill. So 3000 psi is really 600 psi over the 2400 psi service pressure which is a 25% overfill.

Given that steel tanks are normally tested to 5/3rds their service pressure (167% of the service pressure) the tank probably is not going to explode. But it does place more stress on the tank and frequent overfilling to that extent will substantially shorten it's useful life - from 50 plus years to maybe 10-15 years as the odds are pretty good the tank will fail it's 2nd or 3rd hydro.

 

[yknot]

I've got no problem with filling a LP steel tank to 2900-3000 psi and letting it cool off, it's the guys that come in and demand their tanks be filled to 3500 psi that I have a problem with.

What's the difference, besides your method does more long term harm, between a nice slow fill to 3000 and your hot fill to 3000, that cools off to 2200?

The facts are, in spite of what it says on the tanks about pressures, tank failures are EXCEPTIONALLY rare even though overfills and other abusive treatments are quite common. Besides, have the scuba tank police ever fined anyone in the US for this practice?

 

[Paul Evans]

2640 psi is with the 10% overfill. So 3000 psi is really 600 psi over the 2400 psi service pressure which is a 25% overfill.

Given that steel tanks are normally tested to 5/3rds their service pressure (167% of the service pressure) the tank probably is not going to explode. But it does place more stress on the tank and frequent overfilling to that extent will substantially shorten it's useful life - from 50 plus years to maybe 10-15 years as the odds are pretty good the tank will fail it's 2nd or 3rd hydro.

First of all, Cheers Freefloat

Second, if they are selling the same tanks in the US as the UK does this mean they know the tanks will fail much earlier in the UK........ It would seem so........ We have to Hydro tanks every two years, Is it longer in the US?

 

[OceanusDC]

US Hydro is every 5 years and Visual Inspection is every year.

 

[yknot]

US Hydro is every 5 years and Visual Inspection is every year.

Hydro's are a government requirement. They apply to even welding tanks and fire extinguishers. Visuals aren't. They are "suggested" and the interval is "suggested" to be shortened to 6 months max. for heavy use, like on a dive boat.

 

[dvrgaryc]

What's the difference, besides your method does more long term harm, between a nice slow fill to 3000 and your hot fill to 3000, that cools off to 2200?

Steel tanks get a little warm even if you fill them slowly unless you put them in a water vat. Unfortunately, ours is broken, so I do a slow fill on steel tanks.

The facts are, in spite of what it says on the tanks about pressures, tank failures are EXCEPTIONALLY rare even though overfills and other abusive treatments are quite common. Besides, have the scuba tank police ever fined anyone in the US for this practice?

No fines for overfills as far as I've heard, but they will getcha if you don't turn in a quarterly air sample.

 

[dvrgaryc]

oops, the quote in the middle of the last message is mine. I tried a two part response, but it didn't work.

 

[Arnaud]

This thread makes a good point for a self regulated dive industry...

Anyone cares to argue what "DOT" stands for and when they have jurisdiction?

 

[scubafool]

Department of Transportation. My GUESS is that they would only have jurisdiction when something is transported from one state to another, but that is just a guess on my part.

 

[Charlie99]

A common statement is "they rate the same tanks at higher pressure in Europe than in the US". Take a look at the weights of the various tanks vs pressure ratings. They don't look like the same tanks to me.