EXPLOSION! On National Homebrew Day - Converted Keg

Safety notice:
While brewing in the public parking lot of Hopman's Homebrew Supply in Waterford Michigan for National Homebrew day one of the homebrewer's brew kettles (converted sankey keg) expoded with such a bang my ears are still ringing! It is my luck that I happened to be visiting his brewery when the bomb went off. The burner frame was destroyed and the keg tipped spilling 10 gallons of boiling wort onto the pavement. Luckily no one was burned by the wort. Here's what we know:
This keg was manufactured differently than every other keg we examined, the rolled steel lip at the top and bottom was welded solid with no holes drilled in it. No other keg was welded solid and all of them had 4 holes drilled in the keg rim. This is the rim that contacts the ground when the keg is in upright position.
The keg built up pressure in the rim until the rim exploded
We don't know what caused the explosion inside the enclosed rim - air expansion, moisture, maybe some unburned propane (not quite sealed in that case). It exploded after boil was well underway.
What we do know is it is dangerous and you should check your kegs! If there are no holes - drill some! Here's some pictures


http://picasaweb.google.com/wskellenger/BigBrew2007

YIKES. It seems that the keg is still usable though, unless there is more damage than the photos show. At least there's a vent in the rim now

Incredible! If it blew with enough force to knock the keg over, and even damage the stand, I hate to think what kind of injury could have happened.

A serious thanks for the heads up.

Ken

HIGH powered Michigan beer !! Thankfully, no one was injured.

It looks like it created a pressure grenade from the heated air inside the sealed rim. One definition of "homebrew" is to make something (boil kettle) out of scraps, or things not normally intended to be used as such (keg). That opens up the possiblility for this kind of accident to happen.

Good advice to drill vent holes. Even if this case was due to metal fatigue, and other kegs haven't done this YET, it is a potential for this keg design. If it happened once, it'll happen again.

I've heard of bottle bombs but keg bombs takes it to a whole 'nother level. Good to see no one was hurt.

Hey BBRock, Mike Christopher from our club was there and informed us. We were over in Shelby Twp at CRAFT.

My theory on this is that the seam allowed water in during cleaning, but during heating the metal expanded and tightened the seam up. The resulting steam pressure found the weakest point to burst in the rolled section, which was highly stressed in the forming process.

I've put this one out on Tastybrew as well to inform as many people as possible to make sure they put relief holes in the bottom lip of their keggles. I use one as well and it did indeed have holes.

Thanks for posting this. This could save somebody some serious harm.....or worse.

TimO

BBrocker

I checked my HLT (converted keg) and it has the vent holes in the rim.

Maybe one of us engineers on the forum could do some quick calculations to see hwat kind of forces are required to do that kind of damage to the burner. Looks pretty wicked. Very fortunate that nobody got seriously hurt (other than eardrums and a burnt hand).

Glad I went to Cap'n'Cork that day and not Hopman's.

I could model that up and do and FEA on it Greg. Problem is I don't know the exact material but I could get close.

I could model that up and do and FEA on it Greg. Problem is I don't know the exact material but I could get close.

I think kegs are 304SS and there would have to be some assumptions too. I believe there had to be some trapped water / steam pressure involved.

The rupture point probably had a crack that was made worse with each use. I'd guess we're talking about ~200-500 psi pressure in the rim or the damage would have been much worse. The burner stand, having been nearly red hot, would bend pretty easily I'd think.

will be checking my AB keggle tonight.

What? I can't hear you guys. I can't hear anything lately.

One shouldn't have to wear hearing protection when brewing.

What? I can't hear you guys. I can't hear anything lately.

One shouldn't have to wear hearing protection when brewing.

Or at a concert either. I can definitely relate to ringing in the ears and temporary loss of hearing. The Motor City Madman himself at the new years eve whiplash Bash back around '89 at Cobo Hall. It was so loud you couldn't understand a word he was singing if you didn't know the words to the songs. It was the ONLY concert that I experienced ringing in my ears and temporary loss of hearing when I left the arena. In fact, I think I can feel it now just talking about it. Time for a homebrew......

Glad to hear that no one was injured! I posted this over on my homebrew club site. Also, I will bring it up at the meeting this evening. The more people who know the better. Thanks for sharing!