title = "Dye Penetrant Testing (PT): Procedure and Interpretation"

content = """
Dye Penetrant Testing (PT) is an NDT method for detecting surface-breaking discontinuities in any solid, non-porous material — both ferrous and non-ferrous metals, ceramics, and plastics. At Ridgecrest Metalworks, PT is used on stainless steel, aluminum, and non-ferrous castings where MT cannot be applied because the material is non-ferromagnetic.

The principle of PT relies on capillary action. A liquid penetrant with very low surface tension and viscosity is applied to the cleaned surface and allowed to dwell. During dwell time, penetrant wicks into any surface-breaking cracks or porosity. Excess surface penetrant is removed, and a developer is applied. The developer acts as a blotting agent, drawing the penetrant back out of defects and into a visible indication on the surface. The indication is larger than the actual defect, enhancing detectability.

Standard PT process sequence (per ASTM E165 / ISO 3452):
1. Pre-cleaning: Remove all contamination (oil, paint, scale, coatings) from the area to be inspected. Solvent cleaning is standard; surface must be dry before penetrant application.
2. Penetrant application: Apply penetrant by spray, brush, or immersion. Ensure the surface is fully wetted.
3. Dwell time: Allow the penetrant to dwell for the period specified in the procedure — typically 5–30 minutes at surface temperature 10–50 °C. Longer dwell for tight cracks and lower-sensitivity materials.
4. Excess removal: For solvent-removable penetrant, wipe with dry cloth then lightly damp (solvent) cloth. Do not flood the surface with solvent; over-removal strips penetrant from defects.
5. Drying: Allow surface to dry completely before applying developer.
6. Developer application: Spray a thin, even coat of non-aqueous developer. Allow development time (typically 7–30 minutes).
7. Interpretation: Examine under adequate lighting. Red (visible) indications on white developer background are assessed by size, shape, and distribution. Linear indications (length > 3× width) are generally more critical than rounded.
8. Post-cleaning: Remove developer and residual penetrant by washing or wiping.

Fluorescent PT uses UV-fluorescent penetrant and is examined under UV-A light in a darkened booth; it is more sensitive than visible dye PT.

Acceptance criteria for PT on welds are per ISO 23277 or the applicable customer/product standard. All relevant (non-false) indications exceeding acceptance limits are rejected and require repair or concession disposition.
"""

version = "0.0.1"
