Fatigue Diagnosis and Special Assessments

We have worked for more than 20 years on the matters of fatigue and risks of break-up during operations.

Based on the CETMEF recommendation and ISO 12482-1 method, we have used our knowledge over more than 300 machines, in ports and in the industry.

You will find hereafter the complete timing of a fatigue assesment, that can be adapted to each case specificities.

You can also see our references on this kind of project here

History rebuilding - equipment inspection

Goal : assess with the best accuracy the cycles of work withstanded by the equipment, using :

  • Recovery of history elements

  • Discussions with maintenance and exploitation staff

  • Technical inspection of the equipment

Assessment of the overall fatigue index

Step objective : determine the overall fatigue index, i.e. the one of the complete equipment. this index calculation is based on:

  • Original equipment classification
  • Comparison with the real activity performed
  • Calculation of the fatigue parameters (fatigue index, residual lifespan) of the complete equipment and kinematic chains
  • Load cases definition

Computer modeling and stress calculations

Goal : assess by a modern and accurate computer modeling (shell and plate FE model), the stresses in the various assemblies of the equipments, for the different load cases:

  • Adapted modeling from drawing and/or from onsite survey
  • Application of various load cases depending on standard case or on the real activity performed
  • Stress calculations

Identification of critical assemblies

Goal : identify the critical areas of the equipment, based on 3 parameters : stress in resistance, level of stress in fatigue and our know-how on similar assemblies which have been problematic in the past.

To achieve this, we go threw :

  • Rebuilding of stress spectrum and fatigue cycles withstood by the assemblies
  • Notch case identification of the assembly (and onsite verification)
  • Ageing factor and remaining number of cycles available (fatigue cycles and lifting cycles)
  • Determination of critical assemblies by :
    • Maximum stress value,
    • Ageing factor
    • Experience
  • Development of an inspection list for next step 3

Inspection of critical areas

Goal : perform adapted inspection (visual, NDT's) of the various areas identified as critical during the previous steps, in order to chek their integrity :

  • Based on the results of step 2, inspections on assemblies and bodies by : NDT, thermography, vibration analysis, oil analysis, etc

Action definition

Goal : perform a summary of all elements gathered during the assessment and make adapted recommendations:

  • Proposal of control plan
    • Definition of inspection type (visual, magnetoscopy, ultrasonic, liquid penetrant, ACFM, …)
    • Frequency definition
  • Determination of « operational safety » period
  • Recommendations in order to guarantee continuity and security of operations

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