Using an out of service fire extinguisher as an air tank 4

[waskillywabbit]

I'm trying to discourage someone doing such as a "bad idea" and would like to hear your thoughts.

1. Typical red 3 gallon fire extinguisher is one that has been taken out of service due to time limits
2. Top nozzle has been replaced by a welding in a coupling
3. Mounting tabs welded onto shell
4. Operating the fire extinguisher at 100 psi and using it as an on board air system on an off-road vehicle

Thanks.



Brian

 

[metengr]

My only advice to the owner of the off-road vehicle is that I personally would not go near it!

 

[stookeyfpe]

Dangerous. Your using a vessel that is not code certified for something that it was never intended for. The fact that it has been heated by welding concerns me. This extinguisher shell has only one proper place -- a recycling bin.

 

[waskillywabbit]

Believe me guys, I agree 150%!!!

This is NOT me using this, but someone well-respected on an off-roading public forum, so it is in essence encouraging others to be extremely foolish.

Most folks have never heard of the "code" or have a clue about such things, yet I've already pointed out the code issue(s), the fact that it is being used in a way it was not intended to be used, and the modifications by welding...falling on deaf ears.

Thus I'm looking for a more convincing argument other than it is a "bad idea". They just aren't "getting it" and what is worse, others are chiming in saying they don't see anything wrong with it cause they've never had a "problem" with it.

Thanks.

Brian

 

[MadMango]

Suggest that they have the cylinder hydrotested to be safe. Once it fails, they won't be able to use it.

[green]"Art without engineering is dreaming; Engineering without art is calculating."[/green]
Steven K. Roberts, Technomad
Have you read faq731-376 to make the best use of Eng-Tips Forums?

 

[metengr]

waskillywabbit;
It seems to me that you covered the essentials in your second post. You provided the necessary warning. If people still choose to follow someone else’s idea or recommendation, there is nothing more you can say or do. Don't waste your time with this...

 

[3lilaggies]

To error is human, to be far away from that human is wise.

 

[EdStainless]

Using an old, clean, undamaged fire ext. as an air tank is not the most stupid thing that you could do. I would not be supprized to see fatigue failure at the welds.
Welding on any pressure containing device is stupid. The original properties are a function of alloy composition, mechaical forming and heat treatment.
Would these same people buy high quality after-market suspention springs and then weld on them? Would they weld on rotating engine componants?

You could also suggest that they hydro test a unit to see what pressure it will hold. A saftey factor of less than 4:1 would be risky. I have done home-made-hydro. It isn't too hard.

= = = = = = = = = = = = = = = = = = = =
Rust never sleeps
Neither should your protection

http://www.trent-tube.com/contact/Tech_Assist.cfm

 

[arto]

were the welds code welds?
Are the "tabs" designed to not be stress raisers & not cause high local stresses?

The National Board has a nice write up on "air receivers":

http://www.nationalboard.org/Nation...nspectorGuides/CInsp_Guide_Air_Receivers.aspx

look under par. #3 "problems"

 

[waskillywabbit]

Code welds? Code tabs? This is booty fab at its best from what I can tell.

Thanks for the link.

Brian

 

[MJCronin]

waskilly....

Sometimes God must thin the herd..... Darwin developed a theory on this very concept

God often uses boilers and pressure vessels in mysterious ways.....

Warn others.....

-MJC

 

[JohnBreen]

First of all, we are not discussing a "tank" here; rather we are discussing a pressure vessel. Pressure vessels by definition contain pressure of 15 psig and greater. Most states and provinces have Pressure Vessel Laws. If you "convert" anything to contain pressures above 15 psig and expose the public to the hazard you are violating the law (check the National Board site to see if your State/Province has a law). If it bursts, you are responsible for the civil and criminal consequences. The initial pressurization of such devices will reduce the number of guilty parties and the gradual fatigue (and resulting bursts) will get a few more. Sadly, some innocent people will also be hurt. In the case of the subject fire extinguisher, why do you think it was "taken out of service due to time limits"? After a certain number of recharges, it is near the cyclic fatigue life limit. Does the "conversion" add new fatigue life? Quite to the contrary - the shoemaker with the welding torch will likely embrittle the metal.

Auto parts stores in a certain very large state once sold kits to convert propane tanks (used for gas grills) to compressed air receivers. That state did not have a pressure vessel law. In one Summer, two people lost arms to bursting "converted" propane tanks. The auto parts stores that sold the kits were found to be liable for the financial consequences. That state now has a pressure vessel law.

The problem is that most people are not pressure technology engineers and there are blissfully ignorant of the hazards implicit in operating such equipment. If the kit is sold, or if it shows you how on the internet........

http://www.off-road.com/jeep/cherokee/2001/06_jun/airtank/

http://www.nationalwholesaletools.com/index.asp?PageAction=VIEWPROD&ProdID=66

http://www.pelicanparts.com/catalog/ShopCart/TOOL/POR_TOOL_CAT290_pg1.htm

http://wolfstone.halloweenhost.com/HalloweenTech/pnupro_PropaneAirTank.html

.............then it MUST be OK, right? Hey, this is great stuff, you can run your paintball gun from these tanks all season - or until you only have one arm left! See, it seem like there is always somebody who want to ruin your fun.

 

[waskillywabbit]

Most excellent post...that has some teeth to it. You get a star.



Brian

 

[panduru]

@waskillywabbit:

While it must be appreciated that you have brought your concerns out into the open technical forum, I guess the "someone well-respected" must also be alerted immediately to the potential hazards of his improvization.

Every knowledgeable person must take the initiative to bring together the user and the area inspector or other authorized person when there is a potential hazard.

I am sure you will actually be doing a favor to your friend, who incidentally is only ignorant of certain issues and not necessarily stupid, (see "Using an old, clean, undamaged fire ext. as an air tank is not the most stupid thing that you could do."-EdStainless, above).

 

[fireguy519345]

Dry chemical, halon, and halotron extinguisher tanks are to be pressure tested every 12 years, as per NFPA 10, CGA standards and DOT. Water, foam, and other stainless steel cylinders are to be tested every 5 years. Hi pressure tanks such as CO2, O2 and N are to be tested every 5 or 10 years. When we remove a fire extinguisher from service, we drill a hole in the shell. The shell and the valve assembly are discarded separatly. I have had people come and ask for "free" extinguishers for use as air tanks. My answer is short and understandable. I may question their desire to be a member of the Darwin Club. These "tanks" are not desiged to have moisture laden air pumped into them. Fire extinguishers are charged w/dry air or nitrogen. Any other gas will lead to rust and corrosion, and then a possible rupture. When pressure tested, the tester uses a liqued, usually water. Should a cylinder explode while testing, the water filled tank ruptures. Should a cylinder rupture while under pressure of a gas, there is an explosion. Liqued is non-compressable, while a gas is compressable. there have been occasions of people serverly injured while filling tanks w/air. One such case is the person who held a tank between the legs, just before the rupture. He did live, but never to reproduce again.

Next class on used fire equipment will cover those who ask for a used fire \ extinguisher because they are only going to have a small fire, and those who want a used fire sprinkler head to mount over the wood stove.

 

[SnTMan]

I may have told this story in a previous thread, but a friend had a portable air tank blow up while filling a couple of years ago. It was not a conversion, but a commercial product. Fortunately other than some bruises and a garage door no real harm was done. It could easily have taken his head off.

I promptly took my conversion tank (what can I say, I was young when I made it) stripped it, drilled some holes in it and set it out by the curb. I am now somewhat leery about even filling tires.

It's better to be lucky than good.

Mike

 

[waskillywabbit]

Just curious about the story...how big a portable air tank and what commercial product?

Brian

 

[unclesyd]

There have been quite a few incidents of commercial air compressor tank failures where the compressor was hard mounted to the tanks. There was a notice published about this from one of the government agencies which caused our site to issue a project to uncouple the two.

In the ensuing years we gave some employees the direction and materials to check their individual shop and farm compressors. A good percentage reported back that they found cracks when they checked their tanks.

The worst ones were the larger service station size 2 stage compressors. I have seen 3 catastrophic failures of the vertical 2 stage type and 1 of the large horizontal type. I've seen two of the 3-5 gal home style with long seam ruptures and numerous ones cracking and leaking.

 

[SnTMan]

waskillywabbit, don't know all the details, but it was maybe a 5 gal, like are sold everywhere. Fine when new, I guess, but you can't drain the moisture, they get used over a period of years no problem, then one day...

Mike

 

[waskillywabbit]

I have a Craftsman 33 gal vertical compressor/tank (less than 2 years old). I don't see it as being an issue as it is drained when not in use and vented. Stored in my garage.

Brian