METHOD FOR TIGHTENING COUPLING OF OIL WELL PIPE AND METHOD FOR JUDGING ABNORMALITY IN TIGHTENING

摘要

PURPOSE:To make it possible to tighten an oil well pipe in consideration of sealing torque and to make it possible to judge the abnormality in tightening from the viewpoint of the sealing torque by detecting the tightening torque, and finding the torque at a bending point where the tightening torque rises up suddenly. CONSTITUTION:Tightening torque 1 when a coupling is tightened is detected. Torque Tx at a bending point P where the tightening torque rises up suddenly is found. Predetermined minimum sealing torque is added to the torque Tx, and operating torque is obtained. Then, the operating torque is compared with the predetermined minimum torque. Tightening is completed when any of the values becomes the larger value. As a result, torque TF when the tightening is completed is dispersed with the magnitude of the torque Tx, but the predetermined minimum sealing torque is secured without fail. Meanwhile, when the operating torque obtained by adding the minimum sealing torque to the torque Tx is larger than the predetermined maximum torque, it is judged that the tightening is abnormal.