BadWolfOregon
Well-Known Member
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?
I highly advise against JB weld. It's not food grade.
How much can leech from a pinhole? Now it could get bigger over time, which may cause more concern.
I'd say the best is to stick a patch of silver solder on top of it.
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.
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.
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.
Big numbers always look more impressive...
If the weakened area is 0.2 inch in diameter (that's almost a 1/4 inch), the surface area of that weak spot is 0.031 square inch. At 20 psi the force exerted on that spot is 0.031 x 20 = 0.63 pounds or 10 oz. To test, you could take a large nail set tool and push 2 pounds of force on it (3x that of 20 psi). Repeat with 4 pounds or any larger testing force you feel comfortable with, if you want.
Big numbers always look more impressive...
If the weakened area is 0.2 inch in diameter (that's almost a 1/4 inch), the surface area of that weak spot is 0.031 square inch. At 20 psi the force exerted on that spot is 0.031 x 20 = 0.63 pounds or 10 oz. To test, you could take a large nail set tool and push 2 pounds of force on it (3x that of 20 psi). Repeat with 4 pounds or any larger testing force you feel comfortable with, if you want.
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.
Ok, but with a pinhole the beer coming out would just fill the bottom of the kegerator. No explosion....
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.
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...
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!
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