Built-in S-typed array eddy current testing probe and method for detecting defects of tubular structure

2:

• The built-in S-typed array eddy current testing probe for detecting the defects of the tubular structure, as recited in claim 1, wherein:
• the bundle number of exciting coil wires (2) in the exciting coil part is six;
• on the cross section of the columnar coil former (3), the six bundles of exciting coil wires (2) are distributed with a same interval of 60°;
• two bundles of exciting coil wires (2) with the interval of 180° are connected at the end of the columnar coil former (3), actually being the same group of exciting coil wire bundles;
• that is to say, there are totally three groups of exciting coil wire bundles.

6:

• A method for detecting defects of a tubular structure with the built-in S-typed array eddy current testing probe as recited in claim 1, comprising steps of:
• firstly applying a steady-state sinusoidal excitation current (6) to the exciting coil part;
• generating an alternating magnetic field by the steady-state sinusoidal excitation current, inducing an eddy current inside the tubular structure (1) to be detected, and further inducing a secondary magnetic field by the eddy current;
• by a resultant magnetic field formed after superposing the two magnetic fields, enabling two ends of each pancake coil (5) to generate a voltage signal;
• under influences of different defect forms inside the tubular structure (1) to be detected, the induced secondary magnetic field correspondingly changing, and generating different voltage signals:
• wherein:
• an excitation process at each detection position includes three phases, that is to say that the steady-state sinusoidal excitation current (6) is successively applied to the N/2 groups of exciting coil wire bundles in the exciting coil part;
• during excitation of each phase, each differential eddy current testing pick-up unit (4) outside a corresponding bundle of exciting coil wires successively generates a differential detecting signal;
• during each time of working, the four pancake coils (5) in each differential eddy current testing pick-up unit (4) all generate detecting signals, wherein the pancake coils (5) not at two ends of each row continuously work for two times;
• through a difference calculation with additions between signals of opposite pancake coils (5) and subtractions between signals of adjacent pancake coils (5) in each differential eddy current testing pick-up unit (4), a detecting signal at a center of each differential eddy current testing pick-up unit (4) is obtained, wherein the detecting signal carries defect information and is able to simultaneously and effectively reduce interferences of an external environment of lift-off and probe inclination;
• finally, the columnar coil former (3) moving axially along the tubular structure (1) to be detected and driving the probe composed of the exciting coil part and the pick-up coil parts to axially scan the tubular structure (1) to be detected;
• through comparing the detecting signal with a detecting signal of a non-defect tube, judging whether a defect exists in a current scanning area;
• if a defect signal exists, repeatedly scanning the current scanning area, and determining a position of the defect.