Overpressurizing / Overfilling steel tanks

[Boogie711]

There you go again...

"Problem is that some divers fill their tanks past the 300 Bar service rating of the reg and the hydro fill test pressure, usually at better than 5/3 the rated working pressure. And you think there is no danger here... "

NO! No one claimed there wasn't any danger. And I have NEVER not once seen a guy fill a LP tank to 4,500 psi. I routinely fill a LP tank to 3,000 psi. I've had them filled to 3,400 by shop monkeys but I don't worry about it. The highest I've ever HEARD of is 4,100 psi. But I've never, ever seen anyone fill a tank to "past the 300 Bar service rating." That's 4,400 psi!! What do you think we're doing around here - hooking these things up the the compressor and waiting until the engine blows out or something????

And again - the offer is on the table. Please provide a single documented example of a diver injury from an over-pressurized tank whilst in the water.

 

[d33ps1x]

Anyone see any trouble with filling this "OMS" tank to 3k?

 

[DeepScuba]

So what you're saying then GDI, is that me O/filling my LP104's to, say 3300 PSI is OK. Since it's "only" a bit over, and my regs are OK with it too. (Which is 25% over the 10% overfill?)

Sounds like we're talking personal preference vs. any real facts at this point. (Which in fact is how I believe it to be (personal preference, to a point)).

 

[GDI]

HeY I tried And like I said If I can't explain it correctly I can't prove my point have a good laugh on me, I don't overfill my tanks. And you are right the risk will become less for the reg when the pressure is reduced in the tank but the damage may have been done.
Also go look for a article which a diver from Calgary Alberta, A dive shop owner when diving in one of the few lakes in south Alberta, the one with a wreck in it was killed as a result of an exploding tank, a steel 104 tank. It occured in the early 90's, The tank ruptured at the valve neck area.

 

[DeepScuba]

Genesis.......we're Canadian!! We aren't sue happy. Besides, do you REALLY think I'd leave my scuba gear in a burning house???

Not on MY life.

You know how much that stuff costs!!!

Hehehheh

I guess if that's the REAL reason, we have a lot of uneducated tank fillers........cause I've heard some doosies!!

 

[GDI]

:doctor:
As Canadians we are far more conservative than our American brothers. Sometimes I think our favorite past time is showing and telling the world "We are not American" I may live in Florida but I am a proud Canadian and I love my American Wife and the American People

Cave Divers in Florida do have a habit, some not all, of pumping their tanks up to 4000 psi +, They will double the O/P burst Discs. This is called a cave fill Many of cave divers who fill tanks like this need to service their reg more than once annually, not because of the environment they dive but because of decreased performance. It is from this extreme to which I address this issue.
And it is a personal preference to overfill or not to overfill

But I still can't prove my point Great post guys

 

[FredT]

There is a very simple, though not cheap, method of determining the maximum pressure of a lot of tanks.

Step 1 Buy all 200 of one lot's run
Step 2 Randomly pick 20 tanks and remove 5 test coupons from each of the tanks, which will make the tanks scrap.
Step 4 Measure each coupon and destructively test them to determine thickness, yield strength and ultimate strength.
Step 5 The coupon with the LOWEST yield strength defines the characteristics of the lot.
Step 6 Pick another 5 tanks and affix rosette strain gauges to the critical points on the tank.
Step 7 Pressurize the 5 tanks to failure, recording the stress/strain relationship of each rosette along the way to determine minimum yield point of the assemblies.
Step 8 Determine from the data collected in Steps 4 and 7 the lowest pressure the tank passes into yield.
Step 9 Set your maximum fill point for the remaining 175 tanks to not more than 90% of the pressure determined in Step 8, recognizing that at no point may those cylinders be used in commerce or transported by a business owned vehicle if the fill point is higher than the working pressure stamped on the tank.

Note that this will not increase the safety of the "overfill" operation, but it will provide for some defense in court that you did exercise due diligence on determing your fill point if one of the tanks lets go. The argument then will focus on if you had sufficient safety factor in the calculations. There is some justification in narrowing the factor as you have limited the "universe of appication" subject to your determination to one batch of tanks made at one time on one set of tooling from one heat of steel. The extent of that justification is what will be in contention. Manufacturing variables being what they are an entire class of tanks will need to have a much higher safety factor than what a single heat's run can have.

The long and short of it is there are two choices. Choice one is to follow the law as written and applied in your location. Choice two is to do your own thing, and be fully accountable for the results. Just be aware that choice two can be right expen$ive...

FT

 

[Lead_carrier]

I wasn't trying to start a major argument on here. My apologies if this thread caused any more bad feelings than there obviously already are. We'll settle those arguments with split fins at 30 yards tomorrow morning.

 

[FredT]

I'm still waiting for the REAL difference, wall thickness etc between the PST LP104 and E8-130's.

Anyone have those specs?

Those specs are avialable from DOT. 3AA specification is released as part of 49 CFR section 178. The exemption certificate details the general manufacturing specificatons of the E-series tanks and is public domain.

happy reading.
FT

http://www.access.gpo.gov/nara/cfr/waisidx_02/49cfr173_02.html
http://www.access.gpo.gov/nara/cfr/waisidx_02/49cfr178_02.html
http://www.access.gpo.gov/nara/cfr/waisidx_02/49cfr180_02.html

 

[DeepScuba]

That's NOT what I want. I want the DIFF between the two tanks, NOT the DOT general specs., procedures blah blah blah. That don't tell me squat.

If you can find what I need in that pile of Gummint waste, you're a better man than me. (Wouldn't take much).

Oh yeah, if you CAN find it, just post it.