Tubing thread inspection by magnetic flux leakage

The failure of the oil well tubing thread is a very serious problem which may result in accidents and repairs during well servicing. Routine inspections on the threads are thus necessary. This paper proposes a local magnetic flux leakage testing method to inspect the end of the pieces and introduces a certain kind of tubing thread testing equipment based on the magnetic flux leakage theory. The equipment consists of four key components—magnetizer, magnetic field inducer, linear scanner and synchronous sampling controller. The equipment can inspect and prevent tubing thread failures occurring in practice, such as rupture, thread abrasion, crack in the thread root, variations of the taper angle in the thread area, etc. It can meet the testing requirements of the tubing thread and has very wide application perspective.