I had a very interesting experience yesterday, which I would like to share.
I have a typical routine for starting up the power hammer (LG) which includes wiping down the hammer dies from the oil and scale which builds up over night from dripping out of the ways. My routine was interrupted yesterday, and I hadn't cleaned the dies when I pulled a 2"x 3/16" flat which had some minor cupping in the end out of the fire. I saw the mess, but I didn't want to waste the heat, and I didn't think too much about the messy dies. My intent was to take a couple of gentle hits to make it flat, so I continued and put the piece on the die cup down, and made a firm blow - boom!
I was completely surprised to have an explosion occur at impact! It was like someone popped a large balloon, complete with a shower of oil and scale sprayed across the room. It took me a moment to figure out what happened, not relating the explosion to a routine power hammer strike, something that otherwise should have been a crisp wack.
In the end I figure that the oil was trapped in the cupped area getting super heated/boiling, when I brought the head down the compression of the cup caused the oil to flash and it blew up.
It was one of those times that you know your safety glasses were a good investment.
don