A rotary bolt hole eddy current inspection scanner using a differential eddy current probe, the circuitry of the scanner is embodied with a filtering circuit with three filters: FIR (Finite Impulse Response), a low pass filter, and a phase control filter (by means of a Hilbert transform). The result from a scan of a bolt hole is an output signal on an impedance plane exhibiting a “backwards 6” shape of stable size when the scanner changes its rotating rate significantly.

Some embodiments of the invention may include an eddy current nondestructive evaluation device. The eddy current nondestructive evaluation device may include a rotating body; a motor coupled with the rotating body such that the motor rotates the rotating body; a permanent magnet coupled with the rotating body; a pickup coil coupled with the rotating body; and an integrator circuit electrically coupled with the pickup coil that integrates a voltage from the pickup coil to produce integrated voltage data.

Some embodiments of the invention may include an eddy current nondestructive evaluation device. The eddy current nondestructive evaluation device may include a rotating body; a motor coupled with the rotating body such that the motor rotates the rotating body; a permanent magnet coupled with the rotating body; a pickup coil coupled with the rotating body; and an integrator circuit electrically coupled with the pickup coil that integrates a voltage from the pickup coil to produce integrated voltage data.

A method of employing an eddy current sensor to perform an inspection of a tube of a steam generator involves accelerating and decelerating the eddy current sensor in a predetermined fashion that substantially reduces the likelihood of damage to the eddy current sensor. The reduction of probe stresses reduces radiological waste and reduces radiation exposure to workers involved in changing damaged probes The recording of an eddy current signal at each of a plurality of equally spaced apart locations along the tube permits the velocity of the eddy current sensor to be varied without compromising the validity of the data that has been recorded. The inspection system employs an encoder that outputs a series of signals as the probe is advanced incremental distances within the tube of the steam generator, and eddy current sensor signals are recorded responsive to at least some of the signals from the encoder.

Apparatus and methods to investigate a multiple nested conductive pipe structure can be implemented in a variety of applications. An electromagnetic pulsed tool disposed in the multiple nested conductive pipe structure in a wellbore can make a set of log measurements and provide a measured log at different depths in the multiple nested conductive pipe structure. The total thickness of the multiple nested conductive pipes can be determined at each depth in the measured log using a remote field eddy current look-up curve. The remote field eddy current look-up curve can be correlated to a remote field eddy current regime in time-domain associated with time decay response. Additional apparatus, systems, and methods are disclosed.

Some implementations include a method for estimating a first pipe thickness of a first pipe within multiple nested conductive pipes, the method comprising: forming a measured log including a set of log measurements at different depths using an electromagnetic pulsed tool disposed in multiple nested conductive pipes in a wellbore; generating a plurality of remote-field eddy current (RFEC) look-up curves based on measurements of normalized signal level responses for the multiple nested conductive pipes at one or more points in a time decay response; and selecting an RFEC look-up curve from the plurality of RFEC look-up curves at a point in the time decay response that indicates the first pipe thickness of the first pipe.

Some embodiments of the invention may include an eddy current nondestructive evaluation device. The eddy current nondestructive evaluation device may include a rotating body; a motor coupled with the rotating body such that the motor rotates the rotating body; a permanent magnet coupled with the rotating body; a pickup coil coupled with the rotating body; and an integrator circuit electrically coupled with the pickup coil that integrates a voltage from the pickup coil to produce integrated voltage data.

Apparatus and methods to investigate a multiple nested conductive pipe structure can be implemented in a variety of applications. An electromagnetic pulsed tool disposed in the multiple nested conductive pipe structure in a wellbore can make a set of log measurements and provide a measured log at different depths in the multiple nested conductive pipe structure. The total thickness of the multiple nested conductive pipes can be determined at each depth in the measured log using a remote field eddy current look-up curve. The remote field eddy current look-up curve can be correlated to a remote field eddy current regime in time-domain associated with time decay response. Additional apparatus, systems, and methods are disclosed.

A method of employing an eddy current sensor to perform an inspection of a tube of a steam generator involves accelerating and decelerating the eddy current sensor in a predetermined fashion that substantially reduces the likelihood of damage to the eddy current sensor. The reduction of probe stresses reduces radiological waste and reduces radiation exposure to workers involved in changing damaged probes The recording of an eddy current signal at each of a plurality of equally spaced apart locations along the tube permits the velocity of the eddy current sensor to be varied without compromising the validity of the data that has been recorded. The inspection system employs an encoder that outputs a series of signals as the probe is advanced incremental distances within the tube of the steam generator, and eddy current sensor signals are recorded responsive to at least some of the signals from the encoder.

An apparatus and method detect defects in a metal surface. The apparatus is configured to move an eddy coil relative to an underlying metallic surface along a plurality of generally parallel and adjacent scan paths, and to receive from the eddy coil an oscillating signal induced at said coil as it is moved along each path. A representation of the received oscillating signal in relation to each one of a plurality of adjacent scan areas within each path is recorded, and a two-dimensional grid-like map showing the signal representations relative to each scan area is displayed. Defect location is facilitated by a further function of the apparatus and method, by which user input to an interface causes a light source to illuminate a selected part of the metallic surface.