T9074-AS-GIB-010/271 Rev 1
CHAPTER 4 MAGNETIC PARTICLE TESTING
4.1 INTENDED USE. The inspection process is intended for the detection of surface or near surface discontinuities in ferromagnetic materials. 4.2 DEFINITIONS. The standard terminology for magnetic particle examination as described in ASTM E1316 shall apply to this section, except as noted below. 4.2.1 Relevant Indications. Accumulations of magnetic particles caused by discontinuities in the item tested which shall be evaluated to the applicable acceptance criteria.
4.2.2 Indication. Any magnetically held magnetic particle pattern on the surface of a part being tested.
4.2.3 Non-Relevant Indications. Accumulations of magnetic particles held to a particular area caused by conditions that have no bearing on the suitability of the part for service. Examples of such indications that could be considered non-relevant, when evaluated per 4.5, are as follows: a. Magnetic writing: Indication is fuzzy and will be destroyed by demagnetization. These indications are caused by contact with other steel or magnets while magnetized. b. Change in section: Indications are broad and fuzzy caused by concentration of magnetic field. c. Flow lines: These are large groups of parallel indications that occur in forgings under excessive currents. d. Change in permea bility: These are areas in the material where the magnetic “strength” changes. e. Surface roughness. f. Permanent marking: Scribe lines and vibro-etching.
4.3 MAGNETIC PARTICLE INSPECTION REQUIREMENTS.
4.3.1 General Requirements.
4.3.1.1 Method. Magnetic particle inspection may be performed by either the wet or dry method. Unless otherwise specified, the inspection zone for welds shall include the weld and ½ inch of adjacent base material on each side of the weld, where possible. 4.3.1.1.1 Lighting in Test Area. The test area shall be adequately illuminated for proper evaluation of indications revealed on the test surface. Due to the fact that some light-emitting diode (LED) lights have been found to impair color contrast of indications, specific use of these types of lighting sources and other light sources that impair contrast of indications or adversely impact test results shall be approved by the activity’s NDT Examiner, or the Examiner's designated representative. When fluorescent magnetic particle material is used, the inspection shall be accomplished in a darkened area using black light (ultraviolet light). The black light shall be capable of producing an intensity of 800 microwatts per square centimeter on the inspection surface. Intensity shall be measured daily when used, and after bulb replacement. For battery operated black lights, the NDT Examiner shall include a process in the procedure to ensure the depleting battery life does not result in an unacceptable black light intensity during inspections. Not less than 5 minutes shall be allowed for the black light lamp to obtain full brilliance before the lamp is used for any part of the inspection. For LED and other black light sources that do not require a 5-minute warm up, the NDT Examiner shall approve and document an alternative warm up time in the procedure.
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