T9074-AS-GIB-010/271 Rev 1
4.3.2.2 Vehicles. The liquid used as a vehicle for both nonfluorescent and fluorescent magnetic particles shall comply with the following: a. Petroleum distillate conforming to the following specifications shall be used:
(1) MIL-PRF-680 (2) ASTM D3699
(3) SAE AMS 3161 (4) SAE AMS 2641 (5) A-A-59230 b. Tap water with suitable rust inhibitors and wetting and antifoaming agents may be substituted for the petroleum distillate. c. Liquid vehicles used with fluorescent magnetic particles shall be nonfluorescent. 4.3.2.2.1 Cleaning and Drying. Prior to the application of the suspension, all oil, grease, or other foreign matter shall be thoroughly removed from the surface to be tested. Following the removal of the suspension, the piece shall be thoroughly cleaned and dried. 4.3.2.3 Magnetic Particles. Magnetic particles shall be nontoxic and shall exhibit good visual contrast. Fluorescent magnetic particles shall be readily visible when exposed to a filtered black light, as specified in 4.3.1.1.1. 4.3.2.4 Suspensions. Suspensions shall consist of the liquid vehicle and either fluorescent or nonfluorescent magnetic particles, but both types of particles shall not be used simultaneously. Concentration of the suspensions shall be maintained as specified in 4.3.2.6.1. 4.3.2.5 Procedure. Suspensions shall be applied to items being tested by spraying or immersion to ensure thorough coverage of areas requiring tests. 4.3.2.5.1 Continuous Method. For the continuous method, the magnetizing circuit shall be energized just before diverting the stream of suspension from the item being tested, or just before removing the item from the suspension if testing is by immersion, and allowed to remain energized for not less than 1 ⁄ 5 second, with the result that the magnetizing current is applied while the item is still covered with a film of suspension sufficient to give satisfactory indications. 4.3.2.5.2 Residual Method. For the residual method, the item shall be magnetized by the application of direct current (DC) for not less than 1 ⁄ 5 second, after which the magnetizing current shall be turned off and the suspension shall be applied either by spraying or by immersion in the suspension. For application by immersion, the item shall be removed carefully from the suspension to avoid washing off the indications. The residual method shall be used only for inspection of small parts, such as nuts, bolts, pins, gears, and others. 4.3.2.5.3 Circular Magnetization; Central Conductor (Indirect Method). A central conductor shall be used in all cases where testing of internal surfaces of enclosed or cylindrically shaped items of small diameter are required. A central conductor may also be used for circular magnetization of other shapes, when applicable. The conductors shall be as near the inside diameter as practicable. Items shall be spaced to avoid contact, and if warranted by the quantity of work involved, suitable fixtures shall be used for proper orientation. 4.3.2.5.4 Circular Magnetization; Item as Conductor (Direct Method). Where it is necessary to pass current through the item, care shall be exercised to prevent arcing or overheating at the electrode contact areas. Contact areas shall be clean, items shall be mounted horizontally between contact plates, and suitable head pressure exerted to ensure uniform magnetization. When practicable, large and heavy items shall be mounted in suitable fixtures to ensure proper orientation. When protective coatings would interfere with the flow of current, they shall be removed at the area of contact. After tests, the coating shall be repaired.
4-4
Made with FlippingBook - Share PDF online