Bad Regulator Permanently OverCarb'd Beer?

When you were burping the keg did you shake it also? I understand that might be a stretch with a half. Usually you can get the over carb corrected with shakes and burps. Have you checked the beer line to see what it looks like - pockets of CO2 or solid beer? What is the temperature of your second beer, immediately poured into the same glass that you poured the first beer into (room temp glass, pour one, chug or pour out, pour second and take the temp with a calibrated thermometer in beer, not foam). Sounds to me like a balance problem and you may be a little too cold to support then12 psi.

 

Regulators begin to creep when they go bad and you were the recipient of just that. If all of your kegs poured fine prior to the creeping regulator, your keg fell victim to 'carbonation saturation' and your system balance should be just fine. The problem you have encountered is a result of having 50PSI on your beer until, "Days later, received a nicer replacement regulator." Had you released the pressure prior to ordering the new regulator, this operation would be a little easier.

To bring the CO² in the keg back down, dial your regulator back to 0-2PSI and pull the pressure relief valve on your tavern head to release the CO² pressure. [You can also just turn the one way valve 90° if your reg has one] Give the keg a good shake (or unhook it & roll it around) and release the pressure again.

If you perform this task hourly (or every two hours), you will notice the volume of CO² escaping will lessen and when you get to the point where virtually no gas escapes, you're good to go and may dial your pressure back up. Personally, I'd start at 10PSI and then bump the reg pressure up in 1/4 turn increments (every four hours or so) until you are satisfied with the quality of the pour.

You can speed the process up by allowing the keg to reach room temp during this operation, but then you will also be looking at a 24 hour cooling off process as well. [You won't hurt the beer by allowing it to warm up...Stella Artois is pasteurized and shipped here to the US in unrefrigerated containers]

 

No. It's against the Law to permanently over-carb your beer (Gas Laws). Beer (mostly water) and CO2 are soluble. That means the molecules of CO2 will absorb into your beer when under pressure and will escape when there is a path to a lesser pressure area. These molecules are always seeking equilibrium.

Iceace's recommendations will allow you to recover your 1/2 keg. Not sure how long this will take, but you could take the beer down to 0psi (flat) if you continued. If you had perfect pours before, expect the same after all the tweaking is completed.