Oil well drilling derrick - with adjustable fast line sheave, dead line sheave and crown block mounted on horizontal crown beams

摘要

Oil well drilling derrick having parallel horizontal crown beams mounted in the upper part of the derrick. A fast line sheave and a dead line sheave are mounted on the beams near opposite sides of the derrick. A crown block is mounted on the beams between the sheaves. The sheaves and crown block are adjustable along the beams. The various sheaves can be moved readily to different locations for drilling wells in various locations within the base of the derrick without moving the derrick.