Keg Exploded!

[mendozer]

I came home last night and walked into the room where I have my kegerator. 4 kegs are inside and one was outside bc of space. It was pear/apple juice I had kegged to save fridge space. I purged it well with CO2 and it was waiting its turn to go inside the keezer. I heard a hissing so I walked closer. It was clear the apply juice keg was hissing. I leaned in just above the release valve to listen better and BOOOM!

The release valve shot up into the ceiling and a fountain of apple juice shot up hit the ceiling and spilled everywhere. This went on for about 10 seconds before the carbonation died.

How the hell did this thing blow? I purged it so no aerobic bacteria should have been able to ferment the juice into cider. And even if it did, aren't these kegs rated to very high pressures?

The threading on the release valve cracked as well. That's how strong it flew up. It was literally 2" from my left eye when it happened. Thank God my timing was the way it was. A split second later and I would have lost it since I was leaning into it.

Anyone every heard of this before?

 

[m00ps]

Ive had excessive foaming through the relief valve. But that was due to a hop bag floating at the top clogging the valve.

Only thing I can think of is an infection or severe overcarbonation due to a faulty regulator

 

[passedpawn]

Anaerobic bacteria? Lactobacillus is likely on your ceiling.

Ive had ... derp derp derp

Why is there a quote regarding integral calculus in your sig?

 

[ChefRex]

As they say, pictures or it didn't happen

 

[IslandLizard]

+1^ Nice story, but without pictures that's just what it is.

You were damn lucky, that valve could have seriously maimed or even killed you! We have to keep this in mind, vessels under pressure can be very dangerous. What surprises me is that the PRV didn't open up way before it was ejected. Relieving pressure is their only purpose, can't they just do their work when needed?

What made you think you can keep an unpasteurized vat of sugary juice from fermenting? Bugs are all around us. Unlike a PRV they do their job well each and every time. Life finds a way?

 

[Gameface]

Agreed, room temp juice is just begging wild yeast and other bacteria to throw a party.

 

[JonM]

I bet your PR valve was worn out. I recently had to replace one because it was leaking. It was plastic and the threads just wore out. I replaced it with a steel one.

The pressure just could have been the pressure you used to seal the keg up.

 

[September]

My mini Cornys are rated at 130 psi which is a HUGE amount of pressure that I can't foresee ever occuring unless sealing during primary fermentation or something. I'm just a beginner anyway but...

 

[mendozer]

I think it was a fairly new PRV, can't recall exactly. I figured that CO2 would preserve it without need for refrigeration. Doh!

 

[MrFoodScientist]

I have been told that the PRVs are supposed to release at around 60 or 70psi. I know the PRV on my regulator body releases around there, but I don't know about the PRV in the keg. The keg itself is rated to 130psi, but you shouldn't get anywhere close to that, hence the PRV. So yeah, it did its job, not well since it actually busted the threads out, but you don't have keg shrapnel in your chest, so that's a plus.

As far as it fermenting. Yeah, just because you purged it with CO2 doesn't mean you've eliminated any dissolved oxygen to stop anything aerobic or even that you've stopped any fermentation/spoilage. If that were the case, you'd be able to bottle something at any stage and be done with it and bottle bombs wouldn't be a thing.

How long was this sitting out at room temp?

 

[NathPowe]

Glad you're alright man.

I think it's good to remind each other once in awhile that some of these beer toys of ours have the potential to be dangerous. I dropped a CO2 tank the other day and it scared the $hi* out of me. No harm done (except to the tile it landed on), but it was a good reminder to just slow down a bit and be a little more careful.

Anyway - cheers and enjoy the brew.

 

[FloppyKnockers]

Good to hear you came out unscathed.

That said...THAT'S FRIGGIN' AWESOME! I wish I could've seen it when it blew. We do need some pictures if you took any.

And with that said.... It was obviously the deterioration of the plastic in the PRV that led to its demise. Plastic gets brittle with age. This effect is exponential when exposed to hot/cold cycles like cleaning the keg then chilling the contents.

Again, glad you're okay.

 

[william_shakes_beer]

1 would think that the PRV had not been cleaned recently and/or well, was stuck shut and allowed pressure to build.

Which reminds me: Gottal clean my PRVs

 

[mendozer]

Well I didn't take pics since it's just a keg without a PRV. It's not all that old based on the condition of the spring and O ring. I guess it fermented past the PSI tolerance of the PRV. I didn't know they made PRVs out of metal. I'll look into that.

edit: also just saw online Cornys hold up to 130 PSI

 

[doug293cz]

I don't think the PRV on a keg is a safety relief valve. Have you ever taken one apart? The poppet has about a 3/16" diameter, and thus an area of about 0.028 sq. in. I measured the pull force required to crack open the PRV on a new keg, and it was over 5 lbs. That means the pressure in the keg would have to be over 5 / 0.028 = 181 psi to push the PRV open. My kegs are only rated to 130 psi max.

Brew on
Edit: Diameter estimate above is too low, so estimated pressure to open is too high. See my other post below.

 

[doug293cz]

... I didn't know they made PRVs out of metal. I'll look into that.

edit: also just saw online Cornys hold up to 130 PSI

I'd much rather have the plastic PRV blow out, than for the keg rupture. I'll stick with the plastic PRV's, thank you very much.

Brew on

 

[mendozer]

I don't think the PRV on a keg is a safety relief valve. Have you ever taken one apart? The poppet has about a 3/16" diameter, and thus an area of about 0.028 sq. in. I measured the pull force required to crack open the PRV on a new keg, and it was over 5 lbs. That means the pressure in the keg would have to be over 5 / 0.028 = 181 psi to push the PRV open. My kegs are only rated to 130 psi max.

Brew on

hmm how bout that, didn't think about that.

 

[normonster]

I don't think the PRV on a keg is a safety relief valve. Have you ever taken one apart? The poppet has about a 3/16" diameter, and thus an area of about 0.028 sq. in. I measured the pull force required to crack open the PRV on a new keg, and it was over 5 lbs. That means the pressure in the keg would have to be over 5 / 0.028 = 181 psi to push the PRV open. My kegs are only rated to 130 psi max.



Brew on

Are you sure Doug? That seems fukkkin stupid as hell if true.

 

[slym2none]

 

[doug293cz]

Are you sure Doug? That seems fukkkin stupid as hell if true.

Feel free to verify on one of your kegs.

Brew on

 

[mendozer]

hah great meme

 

[joshesmusica]

quick google search, first link to show up:

http://www.cornykeg.com/resources/corny-keg-tips/manual-vs-static-relief-valves/

 

[mattd2]

Feel free to verify on one of your kegs.

Brew on

Wouldn't the first thing to verify be the assumptions you have made e.g. about 3/16, around 5 pounds. Get actual numbers then calculate

 

[doug293cz]

Wouldn't the first thing to verify be the assumptions you have made e.g. about 3/16, around 5 pounds. Get actual numbers then calculate

Well, the 5 lbs was measured (actually measured at 5 - 6 lbs due to some uncertainty about just when the poppet unseated), but the 3/16" was eyeballed, which was a mistake . The actual diameter of the poppet is 0.235", so it has an area of 0.0434 sq in. So, the poppet should unseat and vent at an internal pressure of 115 - 140 psi. Thus it should work as a safety relief valve.

I'd still rather have the plastic body valve as a failsafe backup. If the poppet gets stuck, it would take a lot more internal pressure to pop it open.

Brew on

 

[normonster]

Thank you Douggie.

 

[m00ps]

Anaerobic bacteria? Lactobacillus is likely on your ceiling.



Why is there a quote regarding integral calculus in your sig?

I guess cause I find it amusing when anyone actually understands what it means. Well, equal parts amusing and sympathetically sad...

 

[MrFoodScientist]

Doug,
I agree with you on the plastic threads. Seems safer should something go wrong.
I guess I hadn't thought of the PRV as anything other than a safety feature because these were originally built for soda, so there wouldn't be as much need to purge O2. If the PRV on a keg was never meant as a safety, then how do you explain the pin lock valves?

Though these were not originally intended to be used as fermenters, so any contingency for spontaneous increase in pressure would likely have been assumed to have been from failed equipment, which seems a lot more dangerous than pressure build up from fermentation.

Now I'm just rambling, and I'm not an engineer. So anyway, anyway...

Glad this didn't have a worse outcome at any rate.

 

[LandoLincoln]

Yes, I had a similar experience. I had 5g of an Irish Red that was sitting in a plastic sanke sixtel in my basement, sitting outside of my kegerator for about six months. One day I noticed that beer was leaking from the sanke tap seal. So I hooked up a sanke tap to it and...WHOOSH! The beer came out of the tap at fire hose pressure! Or so it seemed, anyway. It's a good thing that I had a good hold on the hose that was connected to the tap or I can't imagine the horrendous mess it would have made. I drained the entire 5g of beer into the mop sink without having to hook the keg up to any CO2. Jesus. That thing was a bomb waiting to go off. Good thing I noticed it when I did. I'm now very leery of using plastic sixtels for anything that's not going to stay refrigerated.