title: A Lift-Off-Tolerant Magnetic Flux Leakage Testing Method for Drill Pipes at Wellhead.
abstract: To meet the great needs for MFL (magnetic flux leakage) inspection of drill pipes at wellheads, a lift-off-tolerant MFL testing method is proposed and investigated in this paper. Firstly, a Helmholtz coil magnetization method and the whole MFL testing scheme are proposed. Then, based on the magnetic field focusing effect of ferrite cores, a lift-off-tolerant MFL sensor is developed and tested. It shows high sensitivity at a lift-off distance of 5.0 mm. Further, the follow-up high repeatability MFL probing system is designed and manufactured, which was embedded with the developed sensors. It can track the swing movement of drill pipes and allow the pipe ends to pass smoothly. Finally, the developed system is employed in a drilling field for drill pipe inspection. Test results show that the proposed method can fulfill the requirements for drill pipe inspection at wellheads, which is of great importance in drill pipe safety.
authors.affiliation: School of Manufacturing Science and Engineering, Sichuan University, Chengdu 610065, China. wujianbo@scu.edu.cn.
authors.forename: Jianbo
authors.initials: J
authors.lastname: Wu
authors.affiliation: School of Manufacturing Science and Engineering, Sichuan University, Chengdu 610065, China. jfh@scu.edu.cn.
authors.forename: Hui
authors.initials: H
authors.lastname: Fang
authors.affiliation: School of Mechanical Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074, China. gm@chindt.com.
authors.forename: Long
authors.initials: L
authors.lastname: Li
authors.affiliation: School of Manufacturing Science and Engineering, Sichuan University, Chengdu 610065, China. wangjie@scu.edu.cn.
authors.forename: Jie
authors.initials: J
authors.lastname: Wang
authors.affiliation: School of Manufacturing Science and Engineering, Sichuan University, Chengdu 610065, China. 2016223020024@stu.scu.edu.cn.
authors.forename: Xiaoming
authors.initials: X
authors.lastname: Huang
authors.affiliation: School of Mechanical Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074, China. yihuakang@hust.edu.cn.
authors.forename: Yihua
authors.initials: Y
authors.lastname: Kang
authors.affiliation: School of Mechanical Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074, China. yhsun@hust.edu.cn.
authors.forename: Yanhua
authors.initials: Y
authors.lastname: Sun
authors.affiliation: School of Electrical and Electronic Engineering, Newcastle University, Newcastle upon Tyne NE1 7RU, UK. c.tang2@newcastle.ac.uk.
authors.forename: Chaoqing
authors.initials: C
authors.lastname: Tang
keywords: MFL (magnetic flux leakage); drill pipe; lift-off distance; magnetic field focusing