TM 1-1520-265-231-30 Change 2CAUTIONDo not operate magnetic particle equipment within 36 inches of aircraft instruments.1.4.9 DemagnetizationofInspectionParts. Following magnetic particle inspection of a part, theresidual magnetic field in the part shall be reduced to the lowest possible level. This must be doneprior to returning the part to service or rejecting it as a defective part. Unless this is done properly,the residual magnetism may cause adverse influence on instruments, unnecessary wear on parts,or attract ferrous metal chips and dust into bearing surfaces. After demagnetization, a magnetic fieldstrength meter shall be used to measure residual fields. Readings in excess of three units are notacceptable.1.4.9.1 Demagnetization Using AC. If AC demagnetization is selected, hold the part about 12inches in front of the coil. Move it slowly and steadily through the coil to at least 36 inches beyondthe end of the coil while current is still flowing. Repeat process as necessary. Rotate and tumble partsof complex configuration while passing through the coil field. All parts can be demagnetized usinga contour probe in the AC mode. Place the probe against the magnetized part with the switch in ACposition. Turn probe on and withdraw it from the part, or the part from the probe/yoke, about 24inches before turning the probe off.1.4.9.2 Demagnetization Using DC. If DC demagnetization is selected, the initial demagnetizingfield shall be higher than, and in nearly the same direction as, the field reached during inspection.The field shall then be reversed and decreased in magnitude, and the process repeated (cycled)until an acceptable low value of residual field is reached. Whenever possible, parts that have beencircularly magnetized shall be magnetized in the longitudinal direction before being demagnetized.This procedure is limited to stationary equipment.1.4.10 Radiographic(RT)Method.NOTERadiographic inspection shall be performed in accordance with the generalapplication and techniques in TM 1-1500-335-23 (Nondestructive Inspection Methodsmanual) and the specific requirements of this technical manual.Radiographic inspection is used to detect internal and external structural details of all types of partsand materials. This method is used for the inspection of airframe structure for damage, detectionof moisture entrapment, structure alignment, and foreign object intrusion. It can sometimes be usedin areas otherwise inaccessible to other nondestructive inspections and to verify indicationsobserved by other methods.Radiographic inspections are accomplished by passing the X-ray beam through the part orassembly to expose a radiographic film emulsion or other sensitized medium. The processed filmshows the structural details of the part by variations in film density. Requirements for film density,image quality indicator, identification, and other factors are specified in MIL-STD-453.
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