NDT Glossary of Terms

Overview

Non-Destructive Testing has its own vocabulary. This glossary explains terms found in inspection reports and quotes in plain English, while noting where a term depends on the material, defect type, access or governing specification.

Common Terms

• NDT — Non-Destructive Testing; inspection without damaging the asset
• UT — Ultrasonic Testing; sound waves detect internal flaws
• ECT — Eddy Current Testing; electromagnetic surface crack detection
• MPI — Magnetic Particle Inspection; magnetic surface crack detection in steel
• PT — Penetrant Testing; dye reveals surface-breaking defects
• VT — Visual Testing; systematic visual examination
• SWL — Safe Working Load; maximum load an item may safely carry
• Fitness for Service — engineering assessment of continued safe use
• Major Inspection — detailed standards-mandated equipment assessment

How to Read a Method Description

A method name does not describe a complete inspection scope. Ask what material and geometry were examined, which areas were covered, what discontinuity was being sought, and what procedure or acceptance criteria were used. UT, ECT, MPI and PT are complementary; none is a universal substitute for the others.

• Surface-breaking — open to the test surface; PT and MPI are principally surface methods
• Near-surface — close enough to the surface for a method's sensitivity; depth capability varies
• Volumetric — through a material thickness or weld volume; UT may be suitable where geometry and access allow
• Indication — a test response requiring interpretation, not automatically a rejectable defect

Important Caveat

An NDT result describes the areas and method examined under the stated conditions. It does not by itself establish structural acceptance, remaining life or permission to return equipment to service. Those decisions depend on the applicable specification, defect evaluation and responsible engineering advice.