What is NDE?

Owned by Former user (Deleted)
Dec 11, 2015
2 min read

Definition

Nondestructive Examination (NDE) is also known as Nondestructive Testing (NDT). NDE encompasses a number of methods and techniques used to analyze a material, component, or system for flaws or damage from manufacturing or use while keeping the subject itself unharmed. Because the subject of the testing remains intact during the analysis, NDE methods can save time and money without sacrificing safety.

Methods & Techniques

Common NDE methods include visual examination, electromagnetic testing, radiography, liquid penetrant examination, ultrasonic examination, and leak detection. Many of these methods have multiple techniques that can be applied. The different NDE methods and techniques provide diverse levels of results depending on the situation in which they are applied; the tests vary in degrees of thoroughness and cost, so selecting the correct method and technique for each analysis is an important aspect of the examination itself.

Visual Inspection: An examination using raw human senses (sight, hearing, touch, smell) and nonspecialized inspection equipment. Because of its low-tech nature, this test should only be performed by highly trained personnel such as an Authorized Inspector (AI).

Magnetic Particle Inspection (MPI): A type of electromagnetic test that detects surface and nearsurface defects in ferrous materials (i.e., materials that contain iron). A magnetic field is applied externally or via an electric current through the material. Magnetic particles in a carrier fluid are then applied and observed – the presence of a flaw will distort the magnetic field. MPI can be applied to raw material and machined parts before they are put into service; it is also often used to examine in-use structural parts for defects due to fatigue.

Radiographic Inspection: An examination using gamma or x-rays. The radiation that passes through the subject is measured to determine variations in density.

Liquid Penetrant Inspection (LPI): A test in which liquid is applied to the surface of a non-porous material. The flaws will become visible as the liquid gathers within them. LPI testing can be performed with visibly dyed liquids or those that fluoresce when ultraviolet light is applied.

Ultrasonic Inspection: This type of examination utilizes sound waves. The sound waves are applied to the subject and can be used to measure variations in density. Ultrasonic testing can often discover finer flaws than those revealed by radiography.

Hydrostatic and Pneumatic Inspection: Also referred to as pressure testing, these examinations involve filling a vessel with water (hydrostatic) or gas (pneumatic) under pressure to ensure there are no leaks or distortions. The test pressure is usually much higher than the operating pressure to ensure a margin of safety. The presence of a flaw can result in catastrophic failure, so pneumatic tests require extreme care and are generally only performed after multiple other NDE methods have been utilized.