SECTION V PT PROCESS CONTROL

T.O. 33B-1-1 1-20 SECTION V PT PROCESS CONTROL 1.5 PENETRANT PROCESS CONTROL. This section provides basic, operating and advanced level information on the procedures necessary to assure a high quality performance from the penetrant inspection system. The first part of the section discusses the reasons for process and materials control. The second part describes procedures to verify materials quality. The third part outlines review functions of the process. 1.5.1 Need For Process Quality. NOTE Materials and process deficiencies are not always obvious. It is not easily determined that a penetrant has lost its ability to penetrate into a given flaw. Thus, it is necessary to periodically test the materials and to inspect the equipment and process to be sure they are functioning. Penetrant inspection, as well as all other nondestructive inspection processes, is not a perfect process. The presence of indications confirms the existence of discontinuities in the part. However, the absence of indications does not guarantee the absence of discontinuities. Flaws can be present and not be indicated for a number of reasons. The two main reasons for discrepancies in inspection results are: a. Substandard inspection materials due to either receipt of bad material from the manufacturer or degradation in storage or service. b. Process deviations either in equipment, procedures, or conditions. 1.5.1.1 New Materials. Penetrant materials are subjected to extensive testing during their formulation to assure their proper composition. However, materials that do not perform satisfactorily can still be received. Many times, the discrepancies in performance have not been detected until a number of parts have been processed. Considerable effort must then be expended to locate and reinspect the suspect parts. Unsatisfactory materials can result from a number of causes. The penetrant supplier may inadvertently omit an ingredient or a process. An ingredient with similar characteristics may be substituted if the original material is unavailable. The substitution of ingredients may occur at the penetrant formulator’s supplier. Experience has shown that all newly received penetrant materials must be tested to verify performance characteristics. 1.5.1.2 In-Use Materials. Some inspection processes use the penetrant materials one time with no attempt to recover the excess. The materials are usually applied by spraying, and only enough material is applied to perform the test. The materials are stored in closed containers until they are used. These processes minimize the possibility of material contamination or degradation during use. More often, however, the materials are used in open tanks or open containers. When the immersion method is used, the surplus materials are allowed to drain from the part back into the tank. When the materials are applied by brushing, the brush is alternately stroking the part surface and being immersed in the container. Both methods provide numerous opportunities for contamination and deterioration. Materials handled in this manner must be checked periodically to be sure they are functioning acceptably.