T.O. 33B-1-14-834.7.7 InspectionProcedures.4.7.7.1 ConductivityProcedureRequirements.Procedures for conductivity measurement should take into account the varieties of environments and test partconditions which might be encountered. In preparing for conductivity measurement, the following steps should beconsidered:a. Background and objectives of the inspection.b. Equipment requirements.c. Part preparation.d. Instrument calibration.e. Conductivity measurement procedures.f. Acceptance/rejection criteria.4.7.7.2 BackgroundAndObjectives.An understanding of the problem that initiates a conductivity measurement requirement enables the inspector to betterinterpret inspection results and handle unexpected test conditions. The purpose of the test can be separation of mixedor improper alloy, determination of improper heat treatment, and detection of heat or fire damaged material. The typesof material involved and the location of the inspection should be specifically established. Heat and/or fire damage maybe confined to a portion of a part and may vary in the degree of damage. These variables must be considered duringconductivity measurement.4.7.7.3 PartPreparation.As with all types of eddy current inspection, areas on which conductivity measurement is to be performed must be freeof any sharp slivers or foreign material that could damage a probe or cause lift-off changes. Such conditions can beremoved with fine emery paper or other approved means. Conductivity measurements can be performed throughnonconductive coatings that have thicknesses equal to or less than the amount of lift-off adjustment on meter typeequipment. Both the thickness and uniformity of the coating thickness and the amount of lift-off adjustment providedshould be checked prior to measuring conductivity through nonconductive coatings. If lift-off adjustment cannot beobtained, correction factors can be determined for uniform coatings by establishing the change in conductivity readingscaused by the coating and adding this change to each of the measured values. Nonuniform coatings in excess of lift-offadjustment must be removed prior to measuring conductivity. Excessively rough surfaces should be smoothed withemery paper to provide a surface finish 250 RMS or better before performing conductivity measurements.4.7.7.4 CalibrationForMeasuringConductivityValues.NOTEUS Navy - PD-214 Follow instructions in the: instruments’ conductivity program.To calibrate a general purpose instrument for measuring conductivity directly, the following procedures should befollowed:a. Select a sufficient number of standards to obtain a smooth continuous curve over the range ofconductivity to be measured. The actual number of samples will depend on the expected range to bemeasured and the accuracy required.b. Adjust the instrument for lift-off, if applicable, and a standard representing approximately mid-range ofthe conductivities to be measured.
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