Research on Fracture Mechanism and Improvement Methods of Electric Submersible Pump Unit’s Joint Screw

Lijun Zhang*, 1, Hanxiang Wang1, Wenxian Xie2
1 College of Electromechanical Engineering, China University of Petroleum, Qingdao, 266580, China
2 Shengli Oil Production Plant of Shengli Oilfield Company, SINOPEC, Dongying, 257051, China

© 2014 Zhang et al

open-access license: This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 International Public License (CC-BY 4.0), a copy of which is available at: ( This license permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

* Address correspondence to this author at the College of Electromechanical Engineering, China University of Petroleum, Qingdao, 266580, China; Теl: 086-0532-86983500; E-mail:


According to the problem of screw fracture of electric submersible pump unit in Shengtuo oilfield, the reasons for the screw fracture have been analyzed from three aspects: material, strength and pre-tightening force. The preliminary result shows that the imbalanced pre-tightening force of screw is the main reason of screw fracture. By means of Ansys software, the static and modal analyses for the electric submersible pump adapter have been conducted respectively under consistent and inconsistent pre-tightening forces. The numerical simulation results show that when the pre-tightening force is inconsistent, sharp increase in maximum stress of the screw accelerates the screw fracture, and the dynamic performance of screw in the vicinity of 3809.7Hz is the worst. Based on this, the special torque wrench is developed and then the pre-tightening quality of screw is improved greatly by using this wrench.

Keywords: Electric submersible pump, modal analysis, pre-tightening force, screw fracture, torque wrench.