Effective replica testing and creep life assessment by use of stress analysis

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Effective replica testing and creep life assessment by use of stress analysis

Components in high temperature piping systems with increased stress levels often experience increased sensitivity for creep (i.e. time dependent deformation) and creep damage development. Finally creep damage results in creep crack formation and failure.

To help you keep track of the creep damage development, replica testing is usually used. In areas of stress concentrations replica testing can be carried out where small spots of the microstructure are examined to assess the amount of creep.

The results from a well prepared stress analysis of your high temperature piping systems, loaded by thermal expansion, dead weight and internal pressure may be used to pinpoint the critical positions for replica testing. Inspecta offers you a complete service so you can be sure your systems are checked and monitored, thus avoiding stoppages and expensive repairs.

Our present service involves significantly improved feasibility for pipe system stress analyses:

  • Guidelines for efficient pipe modelling:
    Efficient analyses can now be carried out without any substantial influence on the results. In addition, pitfalls that may appear in compiling input data, programme settings and modelling have been investigated. Our results have been compiled in a guideline for elastic analyses.

  • Elastic pipe analyses:
    For steam systems operating just below the limit temperature for creep design, creep cracking is evidently common after 25 years in operation. Replica test positioning can be pinpointed by elastic pipe analysis for such steam pipe systems.

  • Pipe analysis with creep effects included in the material model:
    For steam systems operating above or below the limit temperature for creep design, creep relaxation and creep deformation must be considered when performing pipe system stress analyses. It is necessary to consider possible strain accumulation due to starts and stops in your operations as well as being able to pinpoint the critical pipe positions for replica testing.

  • Component analysis to pinpoint local areas for replica test:
    We are now also able to model and analyse the true stress and strain distribution over time in components such as T-joints in your steam pipe system. In this way, replica testing can be reduced to the critical positions at component level.

  • Assessing the remaining creep life:
    This can be assessed explicitly by analysing creep strain development at critical positions in critical components in service. The results can be verified by replica testing. This concept enables qualified lifetime predictions with far better accuracy than previously. 

Benefits

  • Inspecta’s replica testing will be more attractive to you by reducing the test positions to those which really are critical. The pipe stress analysis pinpoints which components in a pipeline system should be replica tested.

  • Such efficiency is crucial in testing pipe systems within any process industry because stoppages are much shorter. 

  • Your safety levels will be higher since the risk of leaving critical positions untested will be reduced to a minimum.

  • The possibility of reducing potentially significant pipe system stresses at an early stage is another benefit from the system stress analysis.

  • Critical positions at component level are determined by the component stress analysis that also considers system stresses form the system analysis.

  • Increased possibilities for residual lifetime assessments with respect to creep. Residual life assessments of steam pipe line components and systems can be analysed with an accuracy that previously was almost impossible to achieve.