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NDT Knowledge.Understand inspection. Make informed decisions.

Practical articles for quality, production and engineering teams, from defining an inspection task to implementing automation.

Technical articles

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12 articles

These articles provide technical orientation. The specific inspection task and applicable requirements must be assessed for each project.

Fundamentals

Inspection methods at a glance.

Ultrasonic testing – UT

Principle
Sound waves are introduced into the component. The received signals provide indications of material irregularities or component dimensions.
Typical tasks
Examination of internal regions, weld inspection and wall thickness measurement.
Points to consider
Material, geometry, acoustic coupling and the orientation of possible discontinuities influence the result.
Automation
Depending on the task, UT can be used manually, mechanised or automated. Phased array and TOFD are special ultrasonic techniques whose suitability must be assessed for each task.

Eddy current testing – ET

Principle
An electromagnetic field induces eddy currents in electrically conductive materials. Changes in the signal can indicate differing material or surface properties.
Typical tasks
Examination of near-surface regions and suitable inspection tasks on tubes, semi-finished products or series components.
Points to consider
Electrical conductivity, geometry and the distance between sensor and component are relevant influencing factors.
Automation
For suitable tasks, ET integrates well into recurring inspection sequences and material flows.

Magnetic particle testing – MT

Principle
A ferromagnetic test object is magnetised. Magnetic leakage fields at suitable discontinuities can be made visible with detection media.
Typical tasks
Detection of surface cracks and suitable near-surface discontinuities.
Points to consider
The method is limited to ferromagnetic materials; inspection direction and surface condition must be taken into account.

Penetrant testing – PT

Principle
A penetrant enters surface-breaking discontinuities and makes them visible in a defined inspection sequence.
Typical tasks
Surface inspection of suitable, non-porous materials.
Points to consider
Internal, closed discontinuities cannot be detected. Cleaning and surface condition are essential.

Radiographic testing and industrial CT – RT / CT

Principle
Radiography enables imaging of internal structures; industrial CT creates a three-dimensional representation from multiple projections.
Typical tasks
Examination of internal structures, for example in castings or welded components.
Points to consider
Geometry, material, flaw orientation and radiation protection influence its use. CT is a special imaging technique and not a general alternative for every inspection task.

Visual testing – VT

Principle
Accessible surfaces are examined directly or with suitable optical aids.
Typical tasks
Detection of visible irregularities, surface conditions and manufacturing-related features.
Points to consider
Accessibility, lighting and defined evaluation criteria are decisive for the result.

This overview explains methods. Which of them are used in the project and which scope of services NPB takes on is agreed on the basis of your inspection task.

The right method follows from the task.

Key starting points are material, component geometry, the discontinuities sought, accessibility and the required conclusion. Production conditions and evidence requirements also play a role. Several methods often complement each other. A general ranking of the “best inspection method” therefore makes no sense.

Distinguishing inspection extent, coverage and detectability.

Inspecting all components first of all describes the inspection extent. On its own, it does not state which regions of a component are covered and which discontinuities are detectable under the specific conditions. These points must be considered together in the inspection concept.

Traceability needs more than a result value.

An inspection status only becomes traceable with its context. This includes component or batch identity, inspection time, the associated inspection instruction and the program version used. Which raw and result data are stored is defined to suit the inspection task, customer requirement and system concept.

NPB NDT Consulting

Inspection data with traceable context

A result value becomes reliable evidence through its assignment.

  • Component identity

    Component or batch ID

    Unambiguous assignment

  • Inspection context

    Instruction and program version

    System and reference

  • Inspection data

    Time and agreed data

    Scope defined per project

  • Evaluation and roles

    Result status and criteria

    Responsibility and clarification steps

Digital inspection record

Link data and documents

Traceable records for quality and production.

Conceptual illustration. Data scope, interfaces and retention are defined for each project.

Qualification and operational responsibility.

EN ISO 9712 covers the qualification and certification of NDT personnel. The evidence required in each case depends, among other things, on method, sector and task. Personal qualification does not replace system-specific familiarisation and is not a general accreditation of a company.

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Technical sources

The articles and method descriptions provide general technical orientation. The organisations listed are technical sources, not customers or partners of NPB NDT Consulting. Sources may be in German or English.

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Whether it is a new inspection concept, an automated inspection system, a system ramp-up or support for an ongoing project: describe your starting point. Together we will clarify which support fits your needs.

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Sebastian.Kisters@npb-ndt.de+49 203 600 15 160