TASK 70-32-00-200-002
1 . General.
Indirect inspection consists of a variety of methods of dis-closing defects that are invisible to the naked eye. These defects may be inclusions, voids or other subsurface defects, or they may be surface discontinuities too small to be distinguished from the adjacent material.
2 . Qualification of Inspectors.
Subtask 70-32-00-200-021
A.Indirect inspection methods require specialized training and knowledge of techniques, and experience in the interpretation of indications. It is essential that inspectors be able to distinguish between indications of defects and spurious or irrelevant indications in order to evaluate the flaw correctly. For that reason, only qualified inspectors shall be permitted to use these methods.
3 . Applications of Indirect Inspection.
Subtask 70-32-00-200-022
B.Appropriate methods of inspection must be chosen on the basis of the material from which the part is made, of the type of defect to be investigated, and whether it is a surface or sub-surface defect. Magnetic materials, such as iron and ferrous alloys, nickel and cobalt can be reliably inspected for surface defects by the magnetic-particle method. Nonmagnetic materials, such as aluminum, magnesium, brass, copper, bronze, most stainless steels, titanium, ceramics and nonmetallic materials must be inspected by the fluorescent-penetrant method for surface defects. Voids, inclusions, and subsurface discontinuities in any type of material can be disclosed by either ultrasonic or radiograph(X-ray) inspection. In magnetic material, some subsurface defects are indicated by the magnetic-particle method.