T9074-AS-GIB-010/271 Rev 1
4.3.1.6 Demagnetizing Apparatus. Demagnetizing equipment shall consist of units, such as the open coil or box-type demagnetizer, with sufficient capacity to demagnetize the item. 4.3.1.6.1 Demagnetization. All items shall be demagnetized at the following stages to obtain satisfactory indications of discontinuities: a. Prior to testing, if the material contains strong remnant fields from some previous operation or inspection. b. After all magnetic particle testing is completed, if the remnant field interferes with the removal of the magnetic particles in cleaning the part or when specified in the appropriate equipment specification. 4.3.1.7 Equipment Accuracy. Magnetic particle testing equipment shall be checked for accuracy at the time of purchase and at an interval not greater than 6 months and whenever electrical maintenance is performed which may affect the equipment accuracy. Yokes are exempt from the 6 month retest schedule. 4.3.1.7.1 DC Portable Prod and Stationary Magnetic Particle Equipment. To check the equipment ammeter, a suitable calibrated ammeter shall be connected in series with suitable shunts and the current through the electrodes measured. The amperage measured by the calibrated ammeter during the test shall simultaneously be compared to that indicated on the meter of the magnetic particle equipment. The equipment meter shall agree (within 5 percent of full scale) with the current measured by the calibration meter. 4.3.1.7.2 Yoke Equipment. Yokes shall be checked for adequacy of magnetization strength. With the pole spacing set to the maximum that the yoke will be used for, the lifting power, as applied to carbon or alloy steel, shall not be less than 10 pounds for AC electromagnetic yokes. Permanent magnet or DC yokes shall not be used. 4.3.1.8 Magnetizing Current. The magnetizing current shall be based on formulas provided herein or the current shall be determined by means of a segmented magnetic particle field indicator as shown on figure 4-1. Where examination is being performed on complex shapes, the field indicator shall be used to determine the adequacy of the field. The current or technique shall be modified as necessary to ensure that an adequate field is present on all surfaces to be examined. 4.3.1.9 Record Requirements. Records (see 1.8) of magnetic particle inspections shall contain the following: a. Description and unique identification of item inspected. b. Approved procedure identification. c. Instrument manufacturer and model number, or unique equipment identification (yokes excluded). d. Acceptance standard used. e. Date of inspection. f. Signature(s) of inspector(s). g. Disposition (accept/reject) of the item inspected.
4.3.2 Wet Method.
4.3.2.1 General Requirements. Finely divided magnetic particles shall be suspended in a liquid vehicle as the indicating material. The magnetic particles may be either fluorescent or nonfluorescent. All particles shall meet the requirements of SAE AMS 3041, 3042, 3043, 3044, 3045, or 3046 as applicable. 4.3.2.1.1 Equipment. The magnetizing apparatus shall be capable of inducing, in the item under test, a magnetic flux of suitable intensity in the desired direction by either the circular or the longitudinal method.
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