TWO EMPLOYEES WERE IN THE PROCESS OF ASSEMBLING THE FRAMEWORK OF A SCREEN TOWER. WHEN ONE SIDE FRAME WAS SET WITH A 15 TON BRIDGE CRANE IT WAS DETERMINED THAT SOME ALIGNMENT WAS NEEDED BEFORE THE SIDE FRAME COULD BE BOLTED INTO PLACE. HE ATTEMPTED TO RECONNECT THE SPREADER CHAINS TO ENBLE THE SIDE FRAME TO BE LIFTED. WHILE RAISING CRANE IT FELL ON THE INJURED IN THE BACK.