TWO WORKERS WERE POSITIONING A CONVEYER USING AN HITACHI EXCAVATOR TO LIFT THE CONVEYER. THE CONVEYER WAS ATTACHED TO THE EXCAVATOR BUCKET USING TWO SETS OF CHAINS. ONE WORKER WAS ON THE GROUN D ATTEMPTING TO GUIDE THE LIFTED CONVEYER WHEN ALINK ON ONE SET OF CHAINS BROKE. THE CONVEYER FELL TO THE GROUND, APPROX 3 FT, AND STRUCK THE WORKER'S RIGHT UPPER LEG.