Inspection method · PT
Liquid penetrant testing (PT)
A simple, versatile method that reveals surface breaking discontinuities in almost any non-porous material.
01How it works
A liquid penetrant is applied to the cleaned surface and drawn into surface breaking discontinuities by capillary action. After a dwell time, excess penetrant is removed and a developer is applied, which draws the penetrant out and forms a visible (colour contrast) or fluorescent indication.
Pre-cleaning, dwell time, removal and development times and temperature limits are controlled by the procedure.
02Typical industrial applications
- Stainless steel and nickel alloy welds
- Aluminium and copper alloy castings
- Machined surfaces
- Weld root and repair excavations
- Non-ferromagnetic components
03Benefits and what it detects
- Works on most non-porous materials
- Simple and portable
- Clear indications
- Low equipment cost
04Limitations
- Only surface breaking flaws
- Surface must be clean and not porous
- Contaminated or smeared surfaces mask indications
- Temperature limits
- Slower than MT on steel
05Specifying and reviewing the method
Specify the penetrant system and sensitivity, procedure standard and acceptance levels. ISO 3452-1 for the method and ISO 23277 for acceptance levels of welds are common.
Other references: ISO 3452-1, ISO 23277, ASTM E165