PT · Conventional NDT
Liquid Penetrant Testing
The Method
How PT works.
A low-viscosity penetrant is applied to a clean surface and drawn into surface-breaking discontinuities by capillary action. After a controlled dwell, excess penetrant is removed and a developer draws the trapped penetrant back out to form a visible indication.
Penetrants are visible or fluorescent and are removed by solvent, water, or emulsifier, chosen for the sensitivity and surface condition the specification requires.
Applications
Where PT is used
- Welds in austenitic stainless steel, nickel alloys, and nonferrous materials
- Root, final pass, and repair excavation inspection
- Machined surfaces, castings, and forgings
- Components where MT cannot be applied
Detection capability
What PT can detect
- Surface-breaking cracks
- Surface porosity
- Laps, seams, and cold shuts
- Incomplete fusion open to the surface
Methods & Equipment
Typical equipment
- Visible and fluorescent penetrant systems
- Solvent removers, emulsifiers, and developers
- UV-A lamps and light meters for fluorescent work
- Comparator or test panels for process checks
Technical Considerations
Limits and requirements to plan for.
Open to the surface only
PT finds only discontinuities that break the surface.
Surface preparation
Oils and coatings block penetrant. Grinding can smear metal over a discontinuity, so cleaning methods are controlled.
Material compatibility
Many specifications require low sulfur and halogen penetrant materials for stainless steel, nickel alloys, and titanium.
Temperature and dwell
Procedures set surface temperature limits and dwell times.
In Practice
PT in industry.
Naval piping
Stainless and nickel-alloy welds where MT cannot be applied.
Aerospace components
Fluorescent penetrant inspection of nonferrous parts.
Process piping
Weld and repair inspection on stainless systems.
Industries that benefit
How TCI Supports You
What you get from TCI.
- PT performed to your procedures
- Material batch traceability where required
- Fast turnaround through the repair cycle
Let's discuss your inspection requirements.
Tell us about your project, schedule, and the specifications you work to. A member of our leadership team will respond directly.