MINER WAS WORKING ON A CONVEYOR APPROXIMATELY 15' OFF THE GROUND REMOVING A ROLLER NEAR A WRAP PULLEY. A CHAIN SUPPORTING THE WRAP PULLEY STRUCTURE SLIPPED AND THE STRUCTURE WITH THE MINER ON IT DROPPED SEVERAL FEET. THE LEFT ARM WAS ON THE CONVEYOR FRAME AND WHEN HE DROPPED HIS ARM WAS FORCED UPWARD. INJURIES INCLUDE STRAIN TO THE LEFT SHOULDER.