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Inspecting Bolts for Cracks and Corrosion Using the Mentor UT (PAUT)

 

Waygate Technologies Mentor UT Phased Array Flaw Detector
                                        Waygate Technologies Mentor UT Phased Array Flaw Detector

 

Bolt integrity is critical across UK industries such as power generation, oil & gas, infrastructure, aerospace, and rail. Fasteners experience continuous cyclic loading, vibration, and temperature variation. Over time, these conditions can generate fatigue cracking at the shank, thread roots, or under-head fillet, as well as corrosion within the bolt body. These defects often develop internally long before any change is visible.

The Waygate Technologies, Krautkrämer Mentor UT is a Phased Array Ultrasonic Testing (PAUT) system that gives inspectors a reliable method to assess bolt condition in situ. The built-in Bolt Inspection App standardises the scan and removes operator variability, making it suitable for routine maintenance and asset-integrity programmes

Equipment Configuration

 

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  • Mentor UT tablet (32-element PAUT base kit)

  • GE0600417 probe — 4 MHz, 16 elements, 1.5 mm pitch, 24 mm aperture

  • Standard ultrasonic couplant

  • Optional bolt-rotation fixture for repeatable scans

The Mentor UT Bolt Inspection App is built in with customisable and guided workflow that allows operators to scan the entire bolt in place, capturing a 360° volumetric view of its condition. Within seconds, it can identify internal cracks, corrosion, or mechanical deformation without removing the bolt.

 

Understanding the Mentor UT PAUT Results

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1. Sectorial Scan (S-scan)

  • Shows the full refracted angle sweep used to interrogate the bolt.

  • The central high-amplitude vertical response represents the bolt axis/backwall.

  • Colour shading (blue to red) indicates amplitude.

  • Cracks typically present as interruptions or discrete reflectors that break the symmetry of the S-scan.

2. A-scan (Depth-based amplitude)

  • Used for depth confirmation and sizing.

  • A clean bolt shows a stable backwall echo with minimal intermediate reflections.

  • A repeatable mid-path indication may suggest a fatigue crack or corrosion pit.

3. Linear / Time-of-Flight View

  • Displays amplitude vs probe rotation.

  • A continuous horizontal band indicates uniform material.

  • Localised spikes or colour breaks flag corrosion, thread-root cracking, or deformation.

Interpreting the Scan

  • The image shows a consistent central backwall response with no obvious reflector cutting through the sound path.

  • Blue attenuation bands on each side match expected bolt geometry.

  • Evaluation gates appear positioned for thread zone and mid-shank monitoring.

  • The bottom linear display shows a continuous red backwall with no isolated high-amplitude spikes.

This pattern is typical of a bolt without significant internal cracking or corrosion. A technical report would document this as a clean scan. Results can be exported as a PDF report or shared live with your team directly from the field.

Applications

  • Oil & Gas: flange bolts, pressure-retaining fasteners

  • Power Generation: turbine casing bolts, couplings, high-load structural connections

  • Aerospace & Defence: landing gear bolts, engine mounts

  • Rail & Infrastructure: bridge bolts, anchor bolts, track fasteners

  • Marine: deck fittings, exposed structural fasteners

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