Machine implemented analysis eddy current data

A method of machine implemented analysis of multifrequency eddy current test data recorded in quadrature at spaced data points as a probe is passed through the tubes of a heat exchanger, said method comprising the steps of:

• storing the multifrequency eddy current data for the spaced data points in a data array in a programmed digital computer;
• and
• operating the digital computer to examine the data in the data array point by point to identify as lobes sequential data points which exceed preselected threshold values, to group lobes within a predetermined number of data points of each other into signatures, and as to each signature, to calculate the number of data points which define the signature, for signatures defined by less than a preselected number of data points to apply predefined rules to classify the signatures as one of a defined group of structural features, tube defects and irrelevant signals;
• and for a signature defined by more than said preselected number of data points to apply additional predefined criteria to break the signature down into component signatures and to then apply predefined rules thereto to classify each of the component signatures as one of a selected group of structural features tube defects and irrelevant signals.

A method of eddy current testing for defects in tubes supported by support structures within a heat exchanger, comprising the steps of:

• passing a probe through a tube and recording eddy current data signals for successive time spaced data points along the tube;
• inputting the recorded eddy current data signals into a data file in a programmed digital computer;
• programming into the digital computer a set of rules for analysis of the eddy current data to identify structural features of the heat exchanger and defects in the tubing;
• operating the digital computer to analyze the eddy current data point by point and to apply said rules to identify structural features of the heat exchanger and defects in the tubes, if any;
• inputting into the digital computer signals representative of the actual physical location of the structural features of the heat exchanger;
• and
• operating the digital computer to compare the physical location signals for the structural features with the data points at which said structural features were identified, and to thus, as a function of data points between the identified structural features and defects, generate an output identifying the locations of said defects in relation to the actual physical location of the structural features.

A method of machine implemented analysis of eddy current test data recorded in quadrature at spaced data points, comprising the steps of:

• storing the eddy current data for the spaced data points in an array in a digital computer;
• operating the digital computer to establish a noise threshold as a function of selected quadrature components of the eddy current data;
• operating the digital computer to point by point compare the eddy current data with said noise threshold and identified lobes as consecutive data points for which the value of the data points exceeds said noise threshold;
• and
• operating the digital computer to group the lobes into signatures.

Apparatus for analyzing a tube of a heat exchanger comprising:

• a probe and means for passing the probe through a tube to generate multifrequency point by point eddy current data in quadrature;
• means for storing said point by point eddy current data;
• means for electrically comparing said eddy current data point by point with threshold values to generate lobes, to group said lobes into signatures and to apply selected rules to said signatures to classify each of said signatures as one of a group of structural features, tube defects and irrelevant signals;
• means for generating a graphical display simultaneously depicting tube length strip charts of a quadrature channel of selected frequencies of data, zoom strip charts of a selected portion of the data in selected quadrature components of selected frequencies, and X-Y plane lissajous patterns of the selected portion of the data for multiple designated frequencies;
• and
• means for selecting said frequencies and said portions of the data.

Apparatus for analyzing point by point eddy current data recorded in quadrature from the tubes of a heat exchanger comprising:

• means for storing said data point by point as electrical signals;
• means for comparing said electrical data signals point by point with threshold signals and identifying as lobes sequences of data signals which exceed said threshold signals;
• means for grouping said lobes into signatures;
• means for applying preselected rules to said signatures to classify the same as one of a selected group of structural features, tube defects, and irrelevant signals;
• and
• means for generating an output identifying said classification of each signature.