Had a crucible crack during a pour at the old Johnson plant. Metal went everywhere.

It was a Tuesday morning. We were pouring 300 lbs of bronze for a marine fitting. Heard a sound like ice cracking. Looked down and saw a hairline fracture spreading up the side. Shouted 'clear the floor' and backed off fast. Lost about a third of the batch. Had to shut down for two hours to clean the pit and reset. Boss said it was a thermal shock from a cold spot. Now I always do a longer pre-heat, even if we're behind. Anyone have a better way to check for those weak spots before a pour?

2 comments

2 Comments

pipera5013h ago

That "sound like ice cracking" is the worst. We started tapping our crucibles with a brass rod before the pre-heat, listen for a dull ring versus a clear one. It's not perfect but it catches some flaws. A longer pre-heat is smart, but checking for the weak spot first is better. Sucks about the lost batch, that cleanup is a nightmare.

grant_palmer12h ago

Man, that brass rod trick is clever. It reminds me of when we used to thump the kiln shelves with a wooden mallet before a glaze firing. You'd get this weird dead thud if there was a hidden crack, saved us from a few disasters. Different material, same basic idea of listening for trouble. Sometimes the old school methods just work.