A number of different liquid penetrant inspection systems are used in the non-destructive testing (NDT )industry today. Fluorescent penetrants are normally used when the maximum flaw sensitivity is needed. However, these penetrants must be viewed under darkened conditions using an ultraviolet light source (black light). This may not always be practical, so the more commonly used LPI systems used are solvent removable or water washable red dye systems (Visible Contrast). These systems typically are comprised of three components, being 1) a cleaning fluid, 2) the dye penetrant, and 3) the developer. These systems, regardless of type, are often used to check weld quality during fabrication.
Despite being one of the most popular NDT methods, liquid penetrant testing (examination) is often incorrectly conducted. Test surfaces are not cleaned adequately, the contact time (dwell times) between the penetrant and the test surfaces are too short, or the excess penetrant is removed carelessly (i.e. from the flaws and discontinuities as well as from the test surface). For these reasons, SEQ Inspections ensures that our technicians whom carry out liquid penetrant inspections are trained and certified.