What is Liquid Penetrant Testing (PT)?

Liquid penetrant testing is a non-destructive testing (NDT) method used to detect surface cracks and defects in non-porous materials such as metals, plastics, or ceramics.

How is it done? (Briefly)

1. Surface cleaning

o The surface to be tested is cleaned of oil, dirt, and rust.

2. Penetrant application

o A special colored or fluorescent liquid is applied to the surface.

o It is allowed to penetrate into the defects.

3. Cleaning

o Excess penetrant is wiped off the surface.

4. Developer application

o The penetrant inside the defect is brought back to the surface.

o Cracks become visible.

5. Evaluation

o The resulting marks are examined and interpreted.

Where is it used?

• Weld seams

• Cast and forged parts

• Pressure vessels and pipes

Advantages

• Simple and economical

• Shows very small surface cracks

• Does not damage the material

Who should perform it?

• Trained and certified NDT personnel