Nondestructive inspection method for a heat exchanger employing adaptive noise thresholding
View Patent ↗A method of eddy current testing for flaws in a tube is provided that includes passing an eddy current probe through the tube and obtaining eddy current data for a number of positions along the tube, analyzing the eddy current data to generate background noise data for a number of positions along the tube, analyzing the eddy current data to generate extracted data for a number of positions along the tube, and determining whether a flaw of a particular category is present in the tube based on a set of one or more of rules applied to at least a portion of the extracted data, wherein at least one of the rules uses a particular part of the extracted data and employs a threshold that is a function a particular part of the background noise data that is associated with the particular part of the extracted data.
1. A method of eddy current testing for flaws in a tube, comprising:
passing an eddy current probe through the tube and obtaining eddy current data for a first number of positions along the tube;
analyzing the eddy current data to generate background noise data for a second number of positions along the tube, the background noise data comprising a plurality of noise data values wherein each of the noise data values is associated with a respective one of the second number of positions;
analyzing the eddy current data to generate extracted data for a third number of positions along the tube; and
determining whether a flaw of a particular category is present in the tube based on a set of one or more of rules applied to at least a portion of the extracted data, wherein at least one of the rules uses a particular part of the extracted data and employs a changing threshold that changes with position along the tube and that, for any selected position along the tube, is a function of a particular one of the noise data values that is associated with the selected position along the tube.
2. The method according to claim 1 , wherein the analyzing the eddy current data to generate extracted data comprises using the eddy current data and the background noise data to generate the extracted data.
3. The method according to claim 2 , wherein the background noise data is used to create one or more extraction thresholds for generating the extracted data from the eddy current data.
4. The method according to claim 3 , wherein the generating the extracted data from the eddy current data comprises comparing each piece of the eddy current data to one of the extraction thresholds to determine whether the piece of eddy current date should be considered to be extracted data.
5. The method according to claim 1 , wherein the particular part of the extracted data and each of the particular ones of the noise data values are each a voltage.
6. The method according to claim 1 , wherein the particular part of the extracted data and each of the particular ones of the noise data values are each a phase angle.
7. The method according to claim 1 , wherein at least one of the particular ones of the noise data values is a localized noise value associated with a predetermined local portion of the tube.
8. The method according to claim 1 , wherein at least one of the particular ones of the noise data values is a regional noise value associated with a particular region of the tube.
9. A system for eddy current testing for flaws in a tube, comprising:
an eddy current probe mechanism structured to obtain eddy current data for a first number of positions along the tube; and
a computer system having a processing unit comprising a processor and a memory device, wherein the memory device stores one or more routines executable by the processor, the one or more routines including instructions for:
analyzing the eddy current data to generate background noise data for a second number of positions along the tube, the background noise data comprising a plurality of noise data values wherein each of the noise data values is associated with a respective one of the second number of positions;
analyzing the eddy current data to generate extracted data for a third number of positions along the tube; and
determining whether a flaw of a particular category is present in the tube based on a set of one or more of rules applied to at least a portion of the extracted data, wherein at least one of the rules uses a particular part of the extracted data and employs a changing threshold that changes with position along the tube and that, for any selected position along the tube, is a function of a particular one of the noise data values that is associated with the selected position along the tube.
10. The system according to claim 9 , wherein the instructions for analyzing the eddy current data to generate extracted data include instructions for using the eddy current data and the background noise data to generate the extracted data.
11. The system according to claim 10 , wherein the background noise data is used to create one or more extraction thresholds for generating the extracted data from the eddy current data.
12. The system according to claim 11 , wherein the generating the extracted data from the eddy current data comprises instructions for comparing each piece of the eddy current data to one of the extraction thresholds to determine whether the piece of eddy current date should be considered to be extracted data.
13. The system according to claim 9 , wherein the particular part of the extracted data and each of the particular ones of the noise data values are each a voltage.
14. The system according to claim 9 , wherein the particular part of the extracted data and each of the particular ones of the noise data values are each a phase angle.
15. The system according to claim 9 , wherein at least one of the particular ones of the noise data values is a localized noise value associated with a predetermined local portion of the tube.
16. The system according to claim 9 , wherein at least one of the particular ones of the noise data values is a regional noise value associated with a particular region of the tube.
17. The system according to claim 9 , wherein the eddy current probe mechanism comprises and eddy current probe ( 31 ) having a pair of differential coils ( 33 , 350 coupled to testing instrumentation ( 43 ) adapted to digitize a signal generated by the eddy current probe.
18. A method of eddy current testing for flaws in a tube, comprising:
passing an eddy current probe through the tube and obtaining eddy current data for a number of positions along the tube;
analyzing the eddy current data to generate extracted data for a number of positions along the tube; and
determining whether a flaw of a particular category is present in the tube based on a set of one or more of rules applied to at least a portion of the extracted data, wherein at least one of the rules employs a changing threshold, wherein a value of the threshold is adjusted according to a repeating pattern based on a position along the tube.