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 d. General Test Procedure. Whatever type or method of liquid penetrant inspection is to be used, and whether stationary units or portable equipment is available, six basic operations are required in liquid penetrant inspection. (1) Precleaning. In all liquid penetrant inspection processes, the cleaning of the part before processing is critical. Surface dirt, scale, paint, oil, grease, and other contamination must be removed. (a) Vapor degreasing is the preferred cleaning process whenever possible. Other cleaning methods (solvent, ultrasonic, etc.) may be used if necessary. (b) Abrasive cleaning, sand blast, shot blast, emery cloth, sandpaper, steel wire brush, or metal scrapers shall be used to clean metals only if the surface of the metal is not peened by the process or if surface defects are not sealed or contaminated with the abrasive materials. (c) Paint or coatings shall be removed by approved chemical removers. All removers must be neutralized and flushed from the surface, since these materials affect fluorescence of penetrants. (d) If the part has been in contact with water, extreme care must be taken to be sure that all traces of water are removed. Water can prevent penetrant from entering defects. CAUTION All cleaning materials must be completely evaporated and the part completely dry before application of penetrant. (2) Application of Penetrant. Penetrants may be applied by immersion, spraying, brushing, or any other method that completely covers the area to be inspected. (a) The part must be dry and at a temperature of from 50°F to 100°F (10-37°C). (Parts may be heated up to 150°F to increase the sensitivity of the penetrants). (b) After penetrant application, the part will be so positioned as to allow it to drain and to prevent accumulation of penetrant in pools. (c) The penetrant must be allowed to remain on the part for a period of time called the “dwell time”. This allows capillary action to draw the penetrant into the surface openings. The length of time varies with the process and technique used. (Refer to penetration time table in ASTM-E-1417). (d) The penetrant on the surface of the part shall not be allowed to dry completely during the dwell time. Should this occur, the penetrant should be rewetted before removal. 0005 00-18 Change 1