Pieces of the wooden sills rested on top of the blocks and did not fall. When the Assistant Driller took over operating the drawworks, he failed to ask the driller if the CPD was working properly or check its operation himself.
Good communication is essential in avoiding hazards .
Company Management of Change procedures must be followed. Crown saver sills are in place to add a margin of safety when approaching the crown in a slow controlled manner with the blocks. With regard to this situation with the CPD, the driller, mechanic, floorhands and the rig manager shared in the responsibility to challenge the safety of this operation. This material is presented for information purposes only.