FATIGUE DIAGNOSIS

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