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 j. Application of Magnetic Particles. The wet fluorescent continuous method shall be used when inspecting machined surfaces. (1) The suspension shall be applied to the pieces by hosing or immersion so that all surfaces to be examined are thoroughly covered. (2) The magnetizing circuit shall be closed just before the suspension is diverted from the part. Three shots of current, each 1/2 second long, shall be applied (ASTM-E-1444). NOTE At least one of the shots must be applied after the suspension has stopped flowing. (3) The dry particle continuous method may be used on rough surfaces, welds, etc. (4) The residual method will be used only to recheck to determine if indications on faults are irrelevant. k. Interpretation of Indications. (1) An indication is an accumulation of magnetic particles being held by a magnetic leakage at the surface of the part when magnetic particle inspection is applied. (2) A fault is an actual void, crack, inclusion, break, or other flaw in the metal. (3) An irrelevant (false) indication occurs when particles adhere to the surface of keyways, holes, abrupt changes in sections, metal hardness, etc. (4) It is important that the magnetic particle inspector know why and how the indications occur. He must be careful in deciding to accept or reject a part. l. Demagnetization and Cleaning. (1) Parts shall be demagnetized after all magnetic particle testing had been completed. (2) The demagnetizing equipment shall be capable of demagnetizing all inspected parts to a satisfactory level. The level of demagnetization shall be determined with a field indicator which gives approximate quantitative readings of 1.5 oersteds per division. Demagnetized parts shall not produce indications exceeding two units or about 3 oersteds (ASTM-E-1444). (3) Following demagnetization, the parts shall be thoroughly cleaned. All magnetic particles shall be removed from the parts. All plugs and masking shall be removed from holes and cavities. m. Marking. Parts which have met the magnetic particle inspection requirements shall be marked in accordance with ASTM-E-1444 by etching, impression-stamping, dyeing, or other specified means, using approved symbols for inspected parts. 0005 00-16 Change 1