PT is one of the original and most widely utilized non-destructive testing (NDT) methods. PT detects surface breaking discontinuities by relying on the capillary action of a liquid to flow into narrow spaces without the need of assistance by external forces. After an appropriate dwell time, the penetrating liquid is wiped from the test surface and a developer applied to draw the liquid out from any discontinuity. The size and rate of “bleed-out” can then be evaluated against applicable acceptance criteria.
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