Demagnetization

TM-1-1520-265-23 H-60 Helicopter Series Manual
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TM 1-1520-265-23 4.5.3.2 Preparation of Helicopter. The helicopter shall be prepared for safe ground maintenance. A partial inspection for cause (visual indications, sites of mechanical damage, corrosion, etc.) may be performed on all exposed surfaces of the installed part using applicable positions of this procedure. If required, the vibration absorber shall be removed and disassembled in accordance with the applicable technical manuals listed in Table 1-1. 4.5.3.3 Access. Location of these parts varies considerably. Refer to Figure 1-4 and Table 1-2 to locate applicable access provisions. 4.5.3.4 Preparation of Part. The part shall be thoroughly cleaned. Refer to Preparation of Part or Area for NDI, paragraph 1.4.4. 4.5.3.5 NDI Equipment Settings. Refer to Magnetic Particle Method, paragraph 1.4.8. 4.5.3.6 4.5.3.6 Inspection Procedure. A magnetic field shall be applied to the part perpendicular to the orientation of possible cracks. Typical springs and positions required for this inspection are illustrated in Figure 4-5. a. Select AC on the AC/DC power switch. b. Place probe/yoke on part in position 1 as shown. c. Press the test switch and apply a light coat of magnetic particle media at the same time. Remove the media momentarily before removing the current. Current should be applied for no more than five seconds. d. Inspect for cracks using the black light. e. Demagnetize before moving to the next position. Refer to paragraph 4.5.3.8. f. Repeat steps a. through e. for positions 2 and 3. 4.5.3.7 Marking and Recording of Inspection Results. Mark and record inspection results as required by paragraph 1.3. 4.5.3.8 Demagnetization. With the switch remaining in the AC position, place the probe/yoke legs in the same position used for magnetizing. Press the test switch and withdraw the probe/yoke from the part for a distance of two feet before releasing the switch. 4.5.4 Backup Method. None required. 4.5.5 System Securing. Clean the spring thoroughly to remove all residual magnetic particle media. Refer to Post Cleaning and Restoration of Part or Area After NDI, paragraph 1.4.16. The vibration absorber, if removed, requires assembly and installation in accordance with the applicable technical manuals listed in Table 1-1. 4-14

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