Combined eddy current and leakage field detector for well bore piping using a unique magnetizer core structure
US3940689A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | May 14, 1974 |
| Grant date | Feb 24, 1976 |
| Priority date | — |
| Expiry date | May 14, 1994 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01N27/904
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
In the representative embodiment of the present invention disclosed herein, new and improved pipe-inspection apparatus for examining oilfield piping includes, along with other flaw-inspection devices, a flux-leakage inspection device uniquely arranged for detecting minute magnetic-flux anomalies which are indicative of metal defects such as cracks, pits, holes and the like. In contrast, however, to the prior-art high-intensity electromagnetizers typically having cores of minimum magnetic reluctance, the unique pipe-inspection apparatus of the present invention instead employs an electromagnetizer having a core of a substantial length and minimum cross-sectional area to specifically make its reluctance relatively large in relation to the combined magnetic reluctances of the magnetized piping wall and the annular clearances between the piping wall and the magnetizer pole pieces. In this manner, changes in either the surface conditions of the piping wall or in the internal diameter of the well bore piping will have little or no influence on the resulting flux-leakage measurements. Moreover, as a further significant aspect of the present invention, since the magnetic field produced by …
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.