Dye penetrant test for plastics is done based on approved test procedure which indicates dye penetrant test technique, method and penetrant material should be used.
The crack can be found on the molded resins or plastic due to molding stresses, unequal cooling or assembly shock. The dye penetrant testing is done on electrical insulators, plastic pipes, plastic bearing and plastic gears, etc.
Both color contrast (dye) and fluorescent technique are used for plastics. Since the plastic dye penetration test is done on the production line, the water washable penetrant and post emulsification widely is used.
These plastic components can be placed in the cleaner bath and then dried and placed on dye penetrant bath and after elapsing dwell time can be subjected to rinsing with water or go to the post-emulsification depending on the procedure. Then subjected to the developer either with spraying or by immersing on the developer bath.
Then the plastic item is subjected to evaluation and interpretation by a qualified ASNT Level II or III dye penetrant testing specialist. The acceptance criteria that being indicated in approved procedure should be used for interpretation. Specific attention should be performed to not confuse with the false indication.
The standard penetrant material cannot be used for plastic material since might attack the plastic with chemical reaction, etc. The liquid penetrant material should be compatible with the tested objects. However, phenolic resin parts that are used in the electrical system might be tested by standard material since they are compatible with standard material.
Depends on sensitivity, the color contrast (dye) or fluorescent
penetrant test is selected. The fluorescent has higher sensitivity and
is typically used for aircraft plastic switch housing.
The glass bonded mica is (for insulated electronic instruments) another example that is subjected to dye penetrant test. The molding process is extremely important since a little change in the temperature or temperature fluctuation can cause a crack. After completion of the process, the defected item will be discarded.
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