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.
