It says right on my tanks - DO NOT OVERPRESSURIZE

[Ted Judah]

A year ago, I bought tanks for my wife and I. In that year we have used them on 16 dives and had them filled at 5 different dive shops. The pressures after each fill seem to vary wildly and is often overfilled.

Here are the markings on the tanks:

FABER MADE IN ITALY M8303 21/0154/ 073 02•21+
TC - 3AAM - 184/DOT - 3AA2400 DO NOT OVERPRESSURIZE REE67 BS85S


Below are the start fill pressures for each dive:

2400 lbs.
3400 lbs.
2600 lbs.
2500 lbs.
2500 lbs.
2500 lbs.
2200 lbs.
2800 lbs.
2800 lbs.
2800 lbs.
2950 lbs.
2400 lbs.
3000 lbs.
2750 lbs.
3250 lbs.
3525 lbs.

Am I missing something? should I be concerned? Should I request a certain pressure from dive shops?

 

[Bearded Diver]

They are tanks from 1967 through 1980.
Probably?
I would have to look.

If you ever glance at them, love to know what the make is?

 

[Eric Sedletzky]

That's an interesting thought, but I believe the temp of the steel isn't really a factor like we would assume. Let's say you get a hot fill and the tank is 140°... is that really all that hot to steel? It could get up to the same temp sitting in a hot car. Just because it's "hot" to us doesn't mean it's hot.

I would think you're right just on a much smaller scale, like one that really probably doesn't matter (to steel).

I am not an engineer, but I have worked with a lot of "cold" and "hot" steel... I've never seen it do anything different at ambient temps. I could be totally wrong... I never claim to be right, that's just my thought process. I know you work with metal, what do you think?

I think it’s probably true on a micro scale, and since we’re here intellectualizing about it what the hell? More for the conversation.

 

[rob.mwpropane]

Depends on the mix and pressure, but 5-15%. Whether that’s relevant to you for your planning is a you question.

I understand the math isn't 100% accurate, but when I plan I use a SAC a good bit higher than average... in the grand scheme of things in the real world I'm not sure it matters.

So with the z factor what would an LP 85 filled to 3442 actually have?

 

[Rose Robinson]

Hi Rose,

You are right, following those instructions are a nearly foolproof way of ensuring that the fill station operator is not hurt or killed. I would liken it to the food service regulations, where anything between 40F and 140F (5C and 60C) is required to be discarded after two hours. There are plenty of commercial kitchens where this rule is followed (more or less), and it's true that I would worry about eating in one that routinely flouted it.

However, when folks are knowledgeable about when it is safe to break the rules, I also think the marginal risk is small. Sous vide steaks are cooked to a temperature in the "danger zone" and held there, for instance. My guess is an actuary and metallurgist who sat down would find that the fill station operator would be better off overall if they overfilled the tanks but drove 1 mph less getting to work. In any case, I appreciate your sensible perspective. I bet you sleep well at night.

Hi wnissen,

I do not believe, you can use the words safe, and break the rules in the same sentence.

I'm a little reluctant to compare an improperly cooked steak, which may end up giving you ''Montezuma's Revenge'', to an overfill explosion, that could level the building, and kill everyone in it.

I am a Funeral Director, owner/operator, overseeing the day to day activities of four separate locations.
The health and safety of all my employees, including contractors is paramount, I cannot emphasize that strongly enough. My employees are my ''family''

Breaking of industry standards, Legislative requirements, manufacturers instructions is not allowed/tolerated, under any circumstances.

What's the name and address of the restaurant you cook in, where tainted food is served?

By the way, very well, snug as a bug in a rug!

LOL,

Rose

 

[divad]

You should be concerned that they are under filling your tank. Those tanks should be at 3,700psi cold.

It really isn't that big of a deal for low pressure steels.

I can only get 3400 in my LP 85s.