Tube material resistivity (µ Ώ *cm)
Tube material resistivity (µ Ώ *cm)

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A specific operating range, optimized phase spread, called Frequency prime (f90), occurring where there's a phase difference from the shallow I.D. to shallow O.D. defects of 90° (aka base frequency). Additional frequencies are selected for mixing, landmarking (supports), flux density considerations, etc. Minimum base frequency = 4.8. Maximum base frequency 2.1 x f90 = 10. f90 = The frequency which generates a 90° phase separation between a shallow inside and a shallow outside originated defect.

POW Policy of the week "f90"
POW Policy of the week "f90"

The ASME Section V - Article VIII - Mandatory Appendix VIII, states that the operating frequency has to be between the minimum and maximum base frequency as determined by the equations noted on slide 1.

Tube material resistivity (µ Ώ *cm)
Tube material resistivity (µ Ώ *cm)

PDF Version link provided

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