Fixing a pinhole in a corny

A friend gave me an old pin lock keg with an identified pinhole leak. I was wondering if a little JB Weld would be an acceptable way to do that?

 

Subbing for the same situation
Mine is where the dip tube meets the bottom
Small rust spot turned into a pinhole after an oxy wash

 

Are you fermenting in it, or pressurizing it? If the latter, I'd be a wee bit concerned with the weakening of the area. A pressurized vessel with a known weak point is a scary thought.

 

Well, my intention was to pressurize it, but I've never done any kegging before. If it's a serious concern I can always use it as a fermenter or hopback.

 

I personally wouldn't try jb weld. I doubt it is food grade, and I would hate to see the mess if it leaks out overnight. Silver solder would be your best bet for diy, but it may not be sanitary, which could cause problems. I don't know what a local shop would charge to weld it, but it still may not be very sanitary depending on who welds it.

 

Maybe use a small aluminum rivet, food grade silicone and cover it with JB Weld. May be a little exessive but cheaper than another keg... especially when you buy the rivet stuff from harbor freight.

 

Where is the leak located? This may help you decide whether to solder it with special flux and solder, have a welder hit it with SS weld, or retire it.

I highly advise against JB weld. It's not food grade.

 

Conservatively a keg is a pressure vessel typically shouldn't be repaired. I'd repair then retire this one to holding sanitizer, ect.

 

I admit, not much. But I'd still recommend a solder or weld repair if possible.

Or, as has been mentioned, relegate it to fermenting in, or pushing sanitizer or line cleaner. Anything that requires a very low pressure.

 

I would retire it. I have one that will not hold pressure and its my trub keg for keg fermenting. It works well as would it for holding sanitizers etc.

 

If you decide to repair it, depending on where the leak is, I'd get someone to put a bead of welding over the whole area.

 

Even a very skilled welder is going to blow through the metal, pin holes are nothing more than a warning that the base metal is exhausted. Don't bother.

 

The only thing I'd really trust is a weld or silver solder, and I wouldn't trust it to hold pressure again.

Even if it wasn't a burst hazard, it really sucks to come home and find beer at the bottom of your fridge and an empty CO2 tank.

 

I have no concern at all that it is pressurized. Even if you have 40 psi the worst that will happen is that the pinhole will enlarge and you will have a kegerator full of beer outside the keg.

I would consider soldering, though I have no experience in that area.

Best would be welding. But, unless you have a friend or you can do it yourself, it will probably cost more than the price of a new keg.

 

The issue is still that you have a compromised pressure vessel. 20PSI may sound low, but there is a lot of surface area inside a keg. 8.5" diameter, and ~24" tall is ~1360sqin, even ignoring the surface area of the top and bottom that's 27,237lbs of total force on the vessel. The point of this is that it will be looking for a weak spot. The pinhole has given you one. If there is that hole, the metal around it is weakened too. Is the keg going to catastrophically explode? Probably not. Worst case you're looking at a larger hole or tear opening before pressure is released, but that's still not fun.

My only point is I wouldn't use that keg for anything pressurized after a repair. Holding starsan, fermenting, dry hop keg, anything that doesn't need more than a PSI or two.

 

I am no physicist but I think the math you are using is wrong. The pressure relief valve would come no where near to resisting 27,237 pounds. If you opened it and it had that pressure it would blast your fingers off..... not to mention the force the beer would come out of the tap with.

 

Nope, math is correct. I'm listing total cumulative force over the total surface area of the inside of the keg. You have to relate pressure, which is a force per area, to total force over that area. The pressure relief is set to a certain psi (pounds per square inch), and is then sized to have the appropriate surface area to meet that.

Same with the beer coming out. If you have a 1/4" ID line, the "push" area is .049sqin. At 20 psi that's .98lbs pushing. At serve pressure (6psi) it's .29lbs pushing.

 

That's not how it works though. All that force, pressure, whatever you want to think of it as, is pushing out on the container. It's creating internal stresses trying to pull it apart. It's not simply pushing down on that one area. It's a complicated subject. That hole means the surrounding metal is weakened too, you've created places for failures to start.

All you need is a point around that hole that has weakened to the point that it can't withstand sustained high loading, and now you have a new failure.

Stress analysis is part of what I do for a living...

 

http://www.engineersedge.com/material_science/hoop-stress.htm

 

Ok, but with a pinhole the beer coming out would just fill the bottom of the kegerator. No explosion....

 

Right, which I actually said. As quoted from above:

I said that it wouldn't blow up, but there is a real chance of it tearing again, even after a repair. Why risk dumping 5 gallons of liquid? Just use it for non pressurized tasks.

 

But lets be fair, do all the math. What is the differential pressure drop once that hole opens up and the pressure releases? Is it even feasible to expect the keg to open at all, tear or shatter?

Have you ever seem a low pressure stainless tear? Cant happen.

 

Regardless of all this, if you use an Epoxy, make sure it is food safe, and if you do repair it, be prepared for the possibility of running your CO2 dry and/or losing beer.

It's really about risk management.

It's about $40 for a banged up used (but pressure tested) keg, plus shipping, and this one is free, decide if it's worth it to you given the possible downsides and costs of the fix.

 

http://www.mcmaster.com/#66525a21/=11ytmeo food grade exposy .... 1/2 the price of a used keg 1/3 of the price of a new keg (which includes all new hardware and gaskets).........

 

More drama here than most PBS shows.
I would silver solder that pin hole in five minutes and use it like any other keg...

Cheers!

 

Wow, I've never even seen a Peanut Butter Sandwich show!

Aw hell, a stainless steel roofing screw and neoprene bonded stainless washer would do. May as well get redneck.

 

Whatever happened to this keg?

 

I took it into work and had it welded. I've decided to use it as a secondary fermenter!

 

awesome, that's actually a really cool use for it. perfect to cold crash in as well.