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Corrosion Monitoring & Inspection Glossary - N

  • Narrow Axial External Corrosion (NAEC): Narrow, deep, axially oriented corrosion, often along a longitudinal seam weld.

  • Nondestructive Evaluation (NDE): The evaluation of results from nondestructive testing methods or nondestructive testing techniques in order to detect, locate, measure, and evaluate anomalies.

  • Nondestructive Testing (NDT): The actual application of a nondestructive testing method or a nondestructive testing technique.

  • Nondestructive Testing Method (NDT Method): A particular method of nondestructive testing, such as radiography, ultrasonic, magnetic testing, liquid penetrant, visual, leak testing, eddy current, and acoustic emission.

  • Nondestructive Testing Technique (NDT Technique): A specific way of utilizing a particular nondestructive testing method that distinguishes it from other ways of applying the same nondestructive testing method. For example, magnetic testing is a nondestructive testing method while magnetic flux leakage and magnetic particle inspection are nondestructive testing techniques. Similarly, ultrasonics is a nondestructive testing method, while contact shear-wave ultrasonic and contact compression-wave ultrasonic are nondestructive testing techniques.

  • Nonintrusive Monitoring: Monitoring from the outside of the pipe or vessel wall without having to gain access to the interior of the equipment.

  • Nonmetallic Inclusion: A particle of foreign material in a metallic matrix. Usually the foreign material is an oxide, sulfide, or silicate, but may be of any substance foreign to the matrix.

  • Non-Relevant Indication: A response recorded on a chart, data display, or record that comes from a source outside the pipeline, such as foreign objects in the ditch.

  • Nucleate: Initiate the growth of a crack.

Corrosion Inspection and Monitoring