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Introduction to Penetrant Testing

Introduction
History
Improving Detection
—Visual Acuity
—Contrast Sensitivity
—Eye's Response to Light

Principles
Steps for Liquid PI
Common Uses for PI
Pros and Cons of PI

PT Materials
Penetrant Testing Matl's
Penetrants
—Surface Energy
—Specific Gravity
—Viscosity
—Color and Fluorescence
   —Why things Fluoresce
—Dimensional Threshold
—Stability of Penetrants
—Removability
Emulsifiers
Developers

Methods & Techniques
Preparation
—Cleaning Methods
—Metal Smear
Technique Selection
Application Technique
Penetrant Removal
Selecting Developer

Quality & Process Control
Temperature
Penetrant
Dwell
Emulsifier
Wash
Drying
Developer
Lighting
System Performance Check

Other Considerations
Defect Nature
Health & Safety

References

Quizzes
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Quality Control of Drying Process

The temperature used to dry parts after the application of an aqueous wet developer or prior to the application of a dry powder or a nonaqueous wet developer, must be controlled to prevent "cooking" of the penetrant in the defect. High drying temperature can affect penetrants in a couple of ways. First, some penetrants can fade at high temperatures due to dye vaporization or sublimation. Second, high temperatures can cause the penetrant to dry in the the flaw, preventing it from migrating to the surface to produce an indication. To prevent harming the penetrant material, drying temperature should be kept to under 71oC.

The drying should be limited to the minimum length of time necessary to thoroughly dry the component being inspected.