NMWR-9-2815-220 Overhaul Manual for M60 M88 Engine AVDS-1790-2CA, AVDS-1790-2DA, AVDS-1790-2DR Download
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NMWR 9-2815-220 GENERAL MAINTENANCE, OVERHAUL, AND REPAIR PROCEDURES—Continued 0005 00 DIAGNOSTIC AND AUTOMATED TEST EQUIPMENT - Continued e. Surface Condition. (1) It is preferable to disassemble parts before inspection for better visibility, easier handling, and elimination of indications which will confuse inspection. (2) Parts to be inspected by magnetic particle inspection will be cleaned. It is important that all dirt, grease oil, scale and rust be removed. (3) Plating on the parts will not interfere with magnetic particle inspection if the plating is less than 0.004 inch thick. (4) Parts that have been zinc-phosphate coated cannot be reliably magnetized using contact plates or prods. A central conductor or coil should be used. (5) Small openings and oil holes leading to obscure passages or cavities will be plugged with a substantial nonabrasive material which is readily removable. (6) Where a possibility exists, the vehicle used in the wet method may harm nonmetallic areas of a particular part, suitable masking or other protective measures shall be employed to prevent contact of those components with the vehicle. f. Direction of Magnetic Field. The most critical factor in magnetic particle inspection is the direction of the magnetic field. For reliable results, the magnetic lines of force must be at right angles to the defect to be detected. g. Magnetic Fields. Magnetic fields shall be induced in such a manner as to ensure detection of discontinuities having axes in any direction. (1) Circular magnetization consists of inducing a circular field in the part and is applicable for detection of flaws which run parallel to the length of the part. (a) The part is clamped between the contact plates of the magnetic particle inspection unit and current is passed through the part. CAUTION Care must be exercised to prevent burning at contact points. (b) Hollow parts can be magnetized circularly by passing current through a central conductor inserted through the hole in the part. (c) Clamps or prods may be used on parts which are too large to be placed in the magnetic particle inspection unit. 0005 00-14 Change 1