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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 Dwell

The dwell step involves allowing the test component to sit for a sufficient period of time for the penetrant to fill any surface breaking defects that happen to be present. There are basically two dwell modes, immersion-dwell and drain-dwell. The drain-dwell mode has been shown to produce the most sensitive results. The only real quality control required in the dwell step of the process is to ensure that a minimum dwell time is reached. Dwell times are usually recommended by the penetrant producer or required by the specification being followed. There is no harm in allowing a penetrant to dwell longer than the minimum time as long as the penetrant is not allowed to dry on the part.