Electricity: measuring and testing – Magnetic – With means to create magnetic field to test material
Reexamination Certificate
1999-10-06
2001-06-19
Strecker, Gerard R. (Department: 2862)
Electricity: measuring and testing
Magnetic
With means to create magnetic field to test material
C324S227000, C324S229000, C324S232000, C324S233000
Reexamination Certificate
active
06249119
ABSTRACT:
FIELD
The present invention relates to non-destructive testing; more particularly, the present invention relates to non-destructive testing using electromagnetic inspection techniques of tubular goods made from ferromagnetic materials.
BACKGROUND
For many years there has been a need to inspect the tubular goods inserted into wells for defects. Such defects may manifest themselves as reductions or variations in the cross sectional area of the tubing walls, pitting, or longitudinal defects (sometimes called rod wear). Because of the long, slender shape of a section of tubular goods, it is extremely difficult to visually inspect the inside surface of tubular goods. Accordingly, the prior art evidences various non-destructive inspection techniques. Such non-destructive inspection techniques include the use of electromagnetic flux. One example of a system which uses electromagnetic inspection techniques to inspect tubular goods is described in U.S. Pat. Nos. 4,710,712; 4,492,115; 4,636,727; 4,704,580; and 4,792,756.
SUMMARY
The non-destructive defect detection system for the electromagnetic inspection of tubular goods of the present invention is based on the use of time varying electromagnetic fields. The time varying electromagnetic fields used in the instant invention include Eddy current techniques, and AC flux leakage methods. These Eddy current techniques and AC flux leakage methods are used in combination with a saturating DC electromagnetic field to overcome the effects of the permeability changes found in tubular goods made from ferromagnetic materials. Specifically, three-phase AC in the outer driven coils produces signals representative of defects in a plurality of inner pick-up coils. Since the disclosed inspection system for ferromagnetic tubular goods is based on the use of time varying electromagnetic fields, the methods used in the present invention are inherently independent of the travel speed of the tubular goods through the defect detection system and do not require the use of integrator or derivative circuitry.
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patent: 2467306 (1949-04-01), Habig
patent: 4263551 (1981-04-01), Gregory et al.
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Curtis, Jr. William W.
Grubbs Roy C.
ICO, Inc.
Jenkens & Gilchrist a Professional Corporation
Strecker Gerard R.
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