- Any contamination such as oil, rust, scale, corrosion & different types of coatings and surface treatments cover the discontinuity opening and prevent entry of penetrant in to it.
- To detect the discontinuities, test surface shall be free from above mentioned contamination, otherwise indications will not appear.
post emulsifiable liquid penetration testing: It is divided in to two category:
- Method B: Post-Emulsifiable, Lipophilic
- Method D: Post-Emulsifiable, Hydrophilic
Water-Washable, is the most economical method & it has not replaceable for rough casting surface, threaded & key surfaces.
- Water-washable or self-emulsifiable penetrants contain an emulsifier as an integral part of the formulation.
- The excess penetrant is removed from the object surface with a simple water rinse.
- Penetrant materials have the property of forming relatively viscous gels upon contact with water, which results in the formation of gel-like plugs in surface openings.
- While they are completely soluble in water, given enough contact time, the plugs offer a brief period of protection against rapid wash removal. Thus, water-washable penetrant systems provide ease of use and a high level of sensitivity.
Inspection with visible dye penetrant with minimum whate light intensity 100 foot-candles or 1100 lux shall follow. Ultraviolet (UV-A) radiation of minimum intensity 1,000 micro-watts per centimeter squared is common, along with low ambient light levels (less than 2 foot-candles) for fluorescent penetrant examinations. Inspection of the test surface should take place after 10- to 30-minute development time, and is dependent on the penetrant and developer used. This time delay allows the blotting action to occur. The inspector may observe the sample for indication formation when using visible dye. It is also good practice to observe indications as they form because the characteristics of the bleed out are a significant part of interpretation characterization of flaws.
6. Post Cleaning:
The test surface is often cleaned after inspection and recording of defects, especially if post-inspection coating processes are recommended as per PT procedure.
Penetrant Classification System
Type 1 Fluorescent Dye
Type 2 Visible (Red) Dye
Method A Water Washable
Method B Post Emulsifiable, lipophilic (oil base)
Method C Solvent
Method D Post Emulsifiable, hydrophilic (water base)
Class 1 Halogenated (non-flammable)
Class 2 Nonhalogenated (flammable)
Class 3 Special Application
Form a Dry Powder
Form b Water Soluble
Form c Water Suspendable
Form d Nonaqueous Type 1 Fluorescent (solvent based)
Form e Nonaqueous Type 2 Visible (solvent based)
Form f Special Application
Level 1/2 Ultra Low
Level 1 Low
Level 2 Medium
Level 3 High
Level 4 Ultra High