When a pressurised pipe breaks, the escaping fluid exerts a thrust force on the pipe. Under certain circumstances the continuing thrust may induce and plastic hinge in the broken pipe, which in turn generates a rapidly accelerating rotational displacement of the section on the break side of the plastic hinge, the phenomenon called pipe whip. The whipping pipe has the potential to damage objects within the hazard zone and, therefore, must be assessed. Currently a 20 bar threshold is used in nuclear power plant design to delineate high energy lines (HEL) and moderate energy lines (MEL). The threshold is used as a process for establish the requirement for additional pipe whip assessments to be performed as part of HEL guillotine break analysis.  It is currently argued that no such studies are required for MEL. The work presented here provides details of the finite element (FE) analyses undertaken to substantiate the 20 bar threshold used for the differentiation of HEL and MEL. Using the FE analysis method, a range of pipe characteristics, and pressures in the range of 10-50 bar have been studied to determine whether a plastic hinge will occur, and whether pipe whip effects will be seen for that case. The FE results have also been used to assess the suitability of a 5% equivalent plastic strain criteria generally used to define the formation of a plastic hinge and the initiation of pipe whip.


Using Pipe Whip Analysis via the Finite Element Method to Underpin the Delineation Between High and Moderate Energy Lines

Division / Sponsors: 
Power Division & Nuclear Engineering Division (NED)

Power Conference
Paper Proceedings: https://asmedigitalcollection.asme.org/POWER/POWER2020/volume/83747

International Conference on Nuclear Engineering
Paper Proceedings: https://asmedigitalcollection.asme.org/ICONE/ICONE2020/volume/83761

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