Development of an ultrasonic technique, sensors and systems for the volumetric examination of aluminothermic rail welds

RAILECT is a collaboration  between  EU  companies  and  research  organisations  with  the objective to
develop and produce a novel  “clamp-on”  ultrasonic testing  device  for the volumetric examination of
alumino-thermic rail welds.  The system will ultrasonically inspect the weld, and classify it according
to pre-determined quality criteria.

There are an estimated  11  million site  alumino-thermic welds on the European rail network with
thousands  of   new   welds  (estimated at  300,000  to  400,000  annually)  being  made  daily
throughout Europe.  These  welds  form  the basis of ‘continuous welded rail’ (CWR) that is a
common  feature  of  the  European  rail  system.  Although  the  alumino-thermic  welding
technique is well proven,  it  is  none-the-less,  a  critical  safety  component  of the rail
infrastructure.  An increase in rail speeds, density of rail traffic and freight train weights
can now cause an  increasing  number of rail breaks across the European rail network.

The types of volumetric defects  found in  alumino-thermic welds are those normally
associated with gravity feed castings. They include  shrinkage,  hot tears, ‘lack of
fusion’ slag inclusions  and porosity.  The  main  two  types of weld failure are a
vertical  fracture  associated  with  centre  line  shrinkage  and  split web or S
fracture resulting from the cyclic nature of torsional stress in the rail web on
curves in the track. The consequences of a single failure could result in the
derailment causes lost of life and millions of Euros of cost.

Yet  these  welds  are  not  volumetrically  examined  in  any  of  the
countries in the European Union as there is  currently no suitable  NDT
technique due to the complex structure, geometry and thickness of
the alumino-thermic welds. The need for  this  project  arises from
the fact that breakages at  rail  welded  joints occur when there
are flaws in the weld. Hence,  the RAILECT project is designed
to deliver solutions for volumetric inspection of alumino-
thermic welds.