ACFM

Rail Applications

Introduction

The rail industry has many inspection areas for which ACFM has been used. These cover all aspects of the industry including rolling-stock components (such as axles and bogies), bridges and track.

ACFM has been proved beneficial for detecting external cracking on solid axles where ultrasonics are less sensitive. Following trials in which ACFM proved more reliable than MPI, ACFM was approved and accredited for use on axles and wheelsets. Special probes have also been developed to deploy the technique on parts of an axle while still fitted to the train.

Overview

A requirement to inspect bogies without removing paint, led to the development of a special ACFM system for Bombardier Transportation UK. This development included semi-automated detection and sizing, improved reporting and collation of results, as well as several other improvements to the standard equipment.

 

ACFM is also used for detecting and sizing surface-breaking cracking (particularly gauge-corner cracking or head checking) on rails. This type of cracking is often difficult to quantify with ultrasonic probes because the cracks occur in clusters and shallow cracks can mask deeper cracks behind. It is important to know the depth of the deepest crack in a cluster because this determines whether or not the rail can be repaired by grinding.

 

For rail inspection a specially shaped array probe is deployed along the rail using a Walking Stick.

Projects and Applications

Rail track inspection

Project Equipment used

Guage corner cracking

 

 

 

 

ACFM Walking Stick

U19 AMIGO instrument

40mm 8 channel flat array probe 5KHz

Standard weld probe 5KHz

Mini pencil probe 5KHz

Encoder weld probe 5KHz

 

 

The ACFM Walking Stick instrument provides a thorough analysis of surface breaking rail-head defects. Defect pocket-depth analysis is automated and can discriminate between gauge corner cracking and other defect types.

The system utilises advanced windows software, developed by TSC, which automatically analyses the data on-site and can produce yard-by-yard inspection summary reports.

In addition to the ACFM Walking Stick work, TSC have worked closely with a major national rail maintenance company on general track related inspection and point and crossover inspection. In the limited time available to work on railways, ACFM provided rapid, valid results and allowed engineering decisions to be made on the spot.

Train bogie inspection

Project

 Equipment used

Train bogie inspection

 

 

Custom built AMIGO instrument

U19 AMIGO instrument

Long nose 3Bx custom built pencil pobe 5KHz

40mm 8 channel flat array probe 5KHz

Standard weld probe 5KHz

Mini pencil probe 5KHz

Encoder weld probe 5KHz

 

 

Restricted access welds inside the frame ‘swan-neck', on type 91 bogies, were inspected using ACFM.

A dedicated probe was developed by TSC for this highly specialised, limited access inspection.

London Underground

Project Equipment used

 

Dedicated StressProbe instrument

Specialised stress probes

 

 

The tunnel liner stress measurement, commissioned by a London Underground operator, project uses TSC's StressProbe to measure residual & additional induced stresses in tubular sections throughout the tunnel network.

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