Dye penetrant test evaluation should be reviewed in conjunction with liquid penetrant acceptance criteria.
The evaluation should be done by the qualified technician Level II or Level III and based on project approved test procedure. The technician should be familiar with product expected defects and discontinuities.
The technician should have experience and knowledge to differentiate between relevant indication and false indication. The false indication is caused by the poor washing of penetrant material in the washable water system.
What is the relevant Indication? The relevant indication represents the real discontinuities. As per ASME VIII Div 1 Appendix 8, a relevant indication is an indication that its major size is greater than 1.5 mm . The technician normally ignores any indication that is smaller than 1.5 mm
If the dye penetration testing technique is visible, then min light requirement is 1000 Lux or 100 ft candle. If the technique is fluorescent technique, then ultraviolet light intensity should not be less than 1000 microW/cm2