You don't know what you don't know about tanks

[Highmarker]

It makes my stomach turn every time I see a used CNG tank for sale on ebay or craigslist, especially the ones that have expired. These tanks are NOT gas tanks, they are storage vessels of natural gas under high pressure. You don't know what you don't know about these kinds of tanks. People think that 3,600 psi means 3,600 pounds - it means 3,600 pounds per every square inch on the internal surface of the vessel. Take for example Lincoln Composites 9.2 GGE tank that measures 15.7 in diameter and is 49 inches long. This tank (at 3,600 psi) has an axial force of over 600,000 pounds on each dome and a cumulative radial force of nearly 3 million pounds! (see picture attached) These tanks are not to be underestimated. As a design engineer of pressure vessels, I have seen what happens when these tanks fail. Hopefully you understand why these tanks go through such a rigorous test schedule before they are certified and why they are required to be visually inspected every 3 years or 36,000 miles or following an accident or fire. If you do come across a used CNG tank for sale, please have it inspected by a certified CNG cylinder inspector prior to installing and using it. These are not your typical tanks that you fill up with gasoline.

[younkin]

Re: You don't know what you don't know about tanks

High, How often does a CNG Cylinder need to be inspected? Is there an inspector in this area and how much does it cost? Also what are some of the brands that are for sale and which ones do you feel are the best? Jim

[philbert]

Re: You don't know what you don't know about tanks

do you have a picture of one that has failed? or a news story?

[Lakewood90712]

Re: You don't know what you don't know about tanks

do you have a picture of one that has failed? or a news story?

I know of 4 explosive failures. 1 in 1995 that prompted GM to breifly terminate it's cng vehicle sales and attempt to buy back the vehicles at the time (IIRC).

2 of the failures were during re-fueling of damaged tanks , one causing loss of life . (the news story has some in-accurate info. - a real surprise) . The photo in the news story shows the damaged van.

http://cbs2.com/local/Carson.Gas.Tank.2.531822.html

2 causing explosive tank failure , and ejection from the vehicle, both due to heat from fire in the passenger area . One a Crown Vic, one was a GX , both prompting a recall and retrofit. I have not seen the CV , But the GX fire was in Washington state last year. Most of the vehicle was destroyed , tank ejected and landed 100 ft away , just as the fire dept. was rolling up to the fire . By sheer luck of timing , the firefighters did not get killed. I can't find a link , but the photo was one with a caption " uh , was that a car ?"

This is why I will not park in my home garage , does not violate any codes, just is not a good idea IMHO.

[BiggJohn]

Re: You don't know what you don't know about tanks

Here are a few of the most illustrative pictures and a copy of the draft incident report from last year's Seattle GX explosion. It was arson.

[philbert]

Re: You don't know what you don't know about tanks

i understand that prolonged heat, and a malfunction of the relief device can make it go boom, but the refuelling mishap.....what was wrong with the tank. was it expired yet? was it damamged?

[philbert]

Re: You don't know what you don't know about tanks

never mind. i looked at the story. his van was rear ended and the tank was damaged. so.......dont use a tank with a dent would be my guess?

[DannyCNG]

Re: You don't know what you don't know about tanks

So it says the 2 people were ejected from explosion due to heat/fire in the passenger area? what were they doing, smoking? or what?

[Lakewood90712]

Re: You don't know what you don't know about tanks

The damage you see to the van in the news was from the tank explosion , not the preceeding auto accident.

Most shuttle drivers are owner / operators.

I fuel at that station , The following was told to me by another shuttle driver:

"The van was repaired , except for the tank , as it was damaged and red tagged. The driver could not afford a new tank so he tried the bad one"


Taxi and shuttle operators pay a lot for insurrance with a large deductable, and get hit by un-insured often. Guess who pays to get his cab or shuttle back on the road when that happens ?

Cab and shuttle drivers , are a large and silent part of the cng community. They work long hours often with no profit . Financial pressure sometimes makes people take risks , just to feed the family .

[Lakewood90712]

Re: You don't know what you don't know about tanks

So it says the 2 people were ejected from explosion due to heat/fire in the passenger area? what were they doing, smoking? or what?

NO , in the fire cases , THE TANKS WERE EJECTED from the vechicles by explosive force !. Both fire incidents were with vacant vechicles.

The furry looking thing is the remains of the composite tank , found about 100 feet from the car. The fire did not acctivate the pressure releif system . A tank failed in a small area , and presto , instant rocket ! breaking the straps and" NASA , we have liftoff! " simular to a propane "Bleve" , without the liquid. ( Firefighters, feel free to correct my spelling of Bleve if needed )

Both fires were interior fires , spreading to the trunk.

[philbert]

Re: You don't know what you don't know about tanks

so as far as actual tank failures, (not due to fires) we have maybe one....and that one was obviously damaged, and he continued to use it. im guessing that since he got his van back the night before, this was his first fill on his damaged tank. i think i would have been 100yds away with headphones on waiting to see if it blew. im still going to use a used tank, but ill make sure there are no bystanders, and put my glasses on. i just dont think im scared of used tanks yet. you got any more news stories that could maybe scare me into a change of heart?

[Curtis]

Re: You don't know what you don't know about tanks

I think that covers the horror stories... Just get it inspected prior to putting it into service. The tank in the van had been damaged by battery acid that had come in contact with the over wrap. Damage to the wrap is the thing the inspectors are looking for, it's a visual inspection, rather than a hydrostatic or pressure test. Be safe. The shuttle van driver was trying to save a few bucks so he could feed his family... can't do that from where he is now. We don't want you seeing him anytime soon.

[DannyCNG]

Re: You don't know what you don't know about tanks

I recall seeing a couple ? of other CNG stories using google..
but it might be possibly, fire related, THEN spreading to the tank..
and nto really "because ti was cng" being the problem.

So note to self, if a cng vehicle is on fire, get the heck out of dodge lol

I think i might like providing an airport shuttle service..

i guess i need to look up my local laws..

I think the only way i'd buy used is if I see the vehicle intact
and watch them be dismounted carefully. Otherwise i'll pass.

If i'm in a cng vehicle that gets hit... i'll make sure the tank is replaced with
new by the insurance.

The bad part about that is, if the guy was rear ended, the OTHER guys insurance should have paid for it. IF a no-ins neccessary state, he should
have sued the guy for the money. I guess that doens't put him back on the road in the mean time if he's strapped for cash.. but come on if you can
afford the vehicle you can afford a replacement tank can't you?

[Highmarker]

Re: You don't know what you don't know about tanks

Don't forget about what happened in Thailand a few months ago. See link below:

http://www.cngchat.com/forum/showthread.php?t=1288

Those tanks were supposed to go to a scrap yard, but ended up being sold to the public. Now some of you are going to argue that nothing like that "could" ever happen here in the USA, but it wouldn't suprise me one bit if it does. Most of the pictures of tanks for sale on ebay show the tanks in a scrap yard environment with twisted metal all around. A certified CNG cylinder inspector knows what to look for during a visual inspection.

My purpose of this thread is just to make you aware of the force that we are dealing with. The stored energy in the 9.2 GGE Lincoln Tank (mentioned above) at 3,600 psi is equivalent to 2.5 pounds of TNT. Please just be careful and make sure you know what you are doing.

[rkcarguy]

Re: You don't know what you don't know about tanks

Probably some big-oil cronies who torched the GX......