"Overfilling" faber lp 85,95

[-hh]

What I didn't see was some one posting proven facts,which is not to much to ask for.

The facts are that there are ASME and DOT standards and regulations for how the manufacturers should design, test and certify their pressure vessels. As part of this process, these pressure vessels get certain standards as to how they should be used and periodically inspected.

The ASME has existed for 125 years and part of its history has been to figure out why pressure vessels failures occur, and to establish the standards that would put an end to that: at one time (ie, before ASME & DOT), pressure vessel explosions were killing an average of 2 people/day in the USA.

Since you have an Engineering Background, then you also know that when a P.E. puts his Seal on an engineering design, he's effectively betting his career that its right.

Overall, there's tons of hard engineering data behind all of this. None of us have done the homework to dig through it to find specifics. Here's a place to start:

http://www.asme.org/bpvc/

Section VIII is for Pressure Vessels; ISBN 0-7918-2891-3. It costs $495.


On the other side of the fence, we have the "go aheads". They have anecdotal stories and claims, which generally are of the same catagory as the man who fell off of a 50 story building: as he passed the 5th floor, he was heard to say "So far, so good".


Personally, I have yet to meet or hear of anyone who's put 5,000 overfills on a single tank. Yeah, there's people out there with 5,000 dives, but it is _never_ that they've done all those dives on a single tank. As such, the anecdotalists are still ankle deep in the shallow end of the Engineering design pool, thinking that their experience somehow makes them qualified professionals on the subject matter.


-hh

 

[Leadking]

Quotes from PSI's website

A total of 15 SCUBA and fire fighter SCBA cylinders have ruptured explosively in the US from sustained load cracking with an additional 4 at international locations. Although small in numbers, these ruptures caused property damage and personal injury.
Several of the recent aluminum cylinder ruptures have attracted considerable industry attention while the more than 24 steel cylinder ruptures over the years are forgotten. The prudent dive industry professional should be very cognizant that ALL high-pressure cylinders contain phenomenal energy and ALL should be given great care. Every ruptured cylinder had obvious damage whether it was a crack in the threads, damage from excessive heat, extensive corrosion or other abuses.

 

[jonnythan]

Several of the recent aluminum cylinder ruptures have attracted considerable industry attention while the more than 24 steel cylinder ruptures over the years are forgotten.

Very interesting. I wonder why we don't hear about this sort of thing?

Understand that I'm not condoning the practice of overfilling, but..

Those cylinders could be anything. Do we know any of them are relatively recent (last 10 years) overfilled LP tanks? That quote obviously doesn't say so. I'm very curious.. I'd expect news of an overfilled Faber blowing up to spread quite rapidly.

That kind of story would certainly help put an end to threads like this...

 

[pdoege]

Everybody has an opinion

I'll say. Do you have any statistics to back up your opinion? Are you going to stay on your high horse and chew people out when you don't have the stats to back it up?

Let's have some numbers for steel scuba tanks that have failed from overfilling before you keep spouting off.

Peter

 

[wedivebc]

Very interesting. I wonder why we don't hear about this sort of thing?

Understand that I'm not condoning the practice of overfilling, but..

Those cylinders could be anything. Do we know any of them are relatively recent (last 10 years) overfilled LP tanks? That quote obviously doesn't say so. I'm very curious.. I'd expect news of an overfilled Faber blowing up to spread quite rapidly.

That kind of story would certainly help put an end to threads like this...

I think the scuba industry is a small fraction of the compressed gas cylinder usage worldwide.
The tanks we are talking about are the faber steel tanks which are made in Europe, imported to North America with a substantially lower rating than they carry in Europe, but they ARE the same tanks that are filled to 232 bar in Europe. There are millions of these tanks being filled to these pressures legaly and safely and I have never heard of a catastrophic failure. It is however illegal for a business to overfill a customers tanks but what someone does to their own tank is their own business until you transport it on public roads then DOT has something to say about it.

 

[jonnythan]

The tanks we are talking about are the faber steel tanks which are made in Europe, imported to North America with a substantially lower rating than they carry in Europe, but they ARE the same tanks that are filled to 232 bar in Europe.

I've heard that, and I've heard that they're different tanks.

I'd like to see some evidence one way or the other before I believe either side.

 

[mempilot]

Wow!

The service pressure for an OMS 98 is 2400 psi, not 2640 psi. 2640 psi represents a 10% overfill. So a 3000 psi fill is a 25% overfill, not a 13.5% overfill and divers who are considering or suggesting 3500 psi are considering a 46% overfill.

The hydro test pressure is 5/3rds of the service pressure, or a 60% "overfill" at 4000 psi. The critical difference being that the "fill" is done with water with no heating involved and the pressure is only maintained for a few seconds.

Asked and answered but to reinterate, we are talking about a 25% overfill not a 13.5% overfill. I guess it bothers me that you are pushing an argument that may be read by other divers and taken as fact when you don't even have the basic facts straight to begin with.

Burst disc assemblies are commonly available with ratings up to 5000psi, but that does not mean it's ok to use a burst disc with the wrong capacity in your valve. It's common, or at least used to be common in the pre-cave fill era, to use a burst disc capacity of approx 133% of the service pressure to ensure the tank would vent before exploding in a fire and to ensure things vented well before the hydro test pressure. Now it is all too common to use a burst disc with an excessive capacity or to stack two burst discs. Neither practice is safe nor legal.

Everybody has an opinion, but it is a logical fallacy to assume that an opinion is right just because everyone has one or because that opinion is commonly held. At the risk of again offending someone who may think I am talking specifically about them when I'm not, if you came from a certain training orientation and had a dive buddy with unsafe practices or equipment, the conventional wisdom would be to avoid them as they present a safety hazard by violating commonly accepted standards.

The same argument can and should be made about divers with illegal overfills. Those overfills violate not only the law but the accepted industry standards and are perceived to pose a threat of elevated risk to everyone with in range of the exploding tank (ie: everyone on the boat or in the dive shop.)

You can have and express any opinion you want, but your right to put that opinion into action stops the moment your action potentially infringes on the rights of others. The burden of proof is consequently not on adherants to accepted standards to prove that a threat exists if those standards are violated, but rather on the person violating those standards to show that an increase in risk to others does not exist. Adhering to rules and respecting the rights of others is just a matter of social contract - if you want to live in and be accepted by a society, it's just part of the deal.

 

[mempilot]

My OMS tanks are stamped 2640. Here's the specs:
http://www.omsdive.com/cyl_spec.html

Aqua, I'm not arguing, but you sure seem to be.

 

[DA Aquamaster]

I'll be the devils advocate here.

Aqua, I'm not arguing, but you sure seem to be.

Ok....I''' admit, I'm a bit confused with those two statements.

But hey, you be the devils advocate, and I'll just state the legal and social responsibility side of the argument.

Truth be told, I am bothered very little by an informed and knowledgeable diver making a fully informed and carefully considered decision to push the limits a bit. I am inclined to push various established limits a bit myself as long as I am the only one at risk as that is one of the attractions of the sport for me. But I am conerned with discussions that could lead relatively new and uniformed divers to push the same limits without really knowing what they are doing on their little journey into the unknown. As it used to say on the unknown portions of maps "There be dragons there."

 

[jonnythan]

It still seems like no one can point to a single instance of a PST or Faber LP tank exploding, ever, period.

Hm.