Mechanical reliability of a transformer

Underground train


  • Wall mounting brackets for heavy (40 Kg and 60Kg) transformers located within the train tunnels of a metropolitan underground railway system


  • Failures of the bracket at installation causes concern over the long term reliability and raises safety issues


  • To establish the root cause of the initial failures
  • To propose redesign in the event that the root cause is found to be the design / installation of the bracket


  • Establish manufacturing processes and all loading conditions
  • Establish all orientations in which the transformers can be located
  • Determine the operating stresses from installation and normal operation
  • Metallographic examination of the weld


  • Stress analysis concludes that all stresses are well below the limits imposed by good design practice
  • Examination of weld show that it is of poor quality and the root cause of the failure


  • Identification of the source of the cause of the failures
  • Existing design acceptable, new design not required
  • Inadequate quality procedures for welding identified as reason for poor welds

Plant Integrity