SECTION VII INSPECTION AND INTERPRETATION

Table 2-5. Developer Forms and Application Methods in Decreasing Order of Sensitivity

Figure 2-26. Electromagnetic Spectrum Shows the Relatively Narrow Band of Black Light

TM-1-1500-335-23 Nondestructive Inspection Methods Manual
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T.O. 33B-1-1 2-73 SECTION VII INSPECTION AND INTERPRETATION 2.7 INSPECTION AND INTERPRETATION. 2.7.1 Summary. Detection of flaws by the penetrant inspection method depends upon many factors, chiefly, among which are the selection of the appropriate materials and process, the proper application of the chosen process, the quality of lighting during the examination and the ability of a technician to detect flaw indications. This section provides basic, intermediate, and advanced information on the requirements for a reliable inspection and describes the appearance of indications from various types of flaws. The section covers four topics: general requirements, personnel requirements, lighting requirements and guidance on flaw interpretation. 2.7.2 General. a. The purpose of the penetrant inspection process is to detect flaws that will affect the integrity of a part. Many of these flaws may be very small. All of the penetrant materials, procedures, and process controls are oriented to producing valid indications from surface discontinuities. The inspection or examination step is one of the most important and frequently the least controlled of all the process steps. Marginally controlled inspection or examination conditions will degrade the entire penetrant process. Maximum benefits can only be obtained when all aspects of the process (e.g., personnel training and qualification, lighting and inspection environment) receive equal management emphasis. b. The apparent simplicity of the penetrant process is misleading. While the penetrant process is relatively straightforward, the testing depends upon following very carefully prepared processes. Modern penetrant systems are the result of very modern chemical technology. The penetrant inspection process requires diligent care from the initial step to the process completion. An improper or marginal process step may not be recognizable in the inspection booth. As a result, a serious flaw may not be indicated. Many times, the first indicator of process degradation occurs during an individual process step. For example, an excessive emulsification time or an improper water-spray pattern can be identified at the time of the respective process steps, but the consequent removal of penetrant from a defect would go unnoticed. 2.7.3 Personnel. a. Personnel, who are responsible for processing of parts through one or more of the penetrant process steps, even though they do not inspect or interpret indications, SHALL have a basic knowledge of the process theory, practical aspects, and equipment operation. They SHALL be aware of the process control requirements and of the effects of improper procedures or degraded materials on the formation of indications. b. Personnel responsible for inspecting processing parts though one or more of the penetrant process steps and for interpreting and evaluating penetrant indications SHALL have a detailed knowledge of the theory, practical aspects, and application procedures for the major penetrant processes. They SHALL be capable of performing all of the process steps, performing materials and process control tests, and providing technical guidance to operators and trainees. In addition, they SHALL have knowledge of the potential types of discontinuities peculiar to the part being inspected, be familiar with the appearance of penetrant indications of those discontinuities, and have experience in interpretation and evaluation of indications. It is essential for an inspector to gain experience by working with other individuals who possess the required skill before being assigned interpretation responsibilities.

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