Abstract: THREE EMPLOYEES WERE WORKING NEAR THE CRANE DURING RIGGING UP OPERATIONS. A 136 FOOT DERRICK WAS BEING LIFTED FROM A TRUCK BED WHEN A TAIL CHAIN BROKE, CAUSING THE LOAD (DERRICK) TO SHIFT. THE BOOM TWISTED ABOUT 90% AND COLLAPSED TO THE GROUND, STRIKING EMPLOYEE #1 ON THE HEAD AND KNOCKING THE OTHER TWO EMPLOYEES TO THE GROUND. EMPLOYEE #1, A DRILLING SUPERINTENDENT, WAS OVERSEEING THE OPERATION. HE DID NOT HAVE A HARD HAT ON AT THE TIME OF THE ACCIDENT. EMPLOYEE #2, A TOOL PUSHER FOR THE DRILLING COMPANY, WAS ALSO PERFORMING HIS NORMAL DUTIES AS SUPERVISOR DURING THE RIGGING-UP OPERATION. EMPLOYEE #3, A TRUCK SWAMPER, WAS SIGNALING THE TRUCK DRIVER AS THE TRUCK WAS BEING REMOVED FROM UNDER THE DERRICK. THE TAILCHAIN WAS MANUFACTURED BY LEBUS. IT WAS A 7/8 INCH STANDARD ALL ALLOY CHAIN USED WITH A STYLE "B" HOOK CHAIN. THE CHAIN AND HOOK WERE RATED AT 28,600 POUNDS. THE CHAIN SEPARATED AT THE WELDED JOINTS. THE WEIGHT OF THE LOAD AT THE TIME OF THE ACCIDENT WAS UNKNOWN.