harmonic – What Is Piping

Harmonic analysis is the dynamic analysis used to predict the steady-state dynamic response of the piping system subjected to sinusoidally varying loads. All kinds of externally applied loads like nodal, elemental, gravity, and thermal loads can be included as load input. Accordingly, load cases are required to prepare and included in the solution. Load components in each load case use the same factor and phase angle. Different load cases may have different factors and phase angles, but the frequency for all loads is the same. The points that will be covered in this article are: IntroductionReviewing the Static Model Creating the Harmonic inputThe Harmonic AnalysisResult ReviewAcoustic vibration and resonance is caused by Positive displacement pumps Introduction to Harmonic Analysis The harmonic analysis considers the effect of a harmonic load being applied to the system. The load is usually applied as a sinusoidal function (Fig. 1), e.g. pressure pulsation from reciprocating equipment. Being of a cyclic nature, harmonic loading relates to the fatigue allowable of the design code and should be considered. Care should be taken when undertaking a harmonic analysis for the accuracy of input data. Information relating to existing field problems can be derived from the measurement of pressure pulsation, deflection, forces, etc. Reviewing the Caesar II Static Model for Harmonic Analysis Fig.1: Introduction to Harmonic Analysis Creating harmonic Input for Analysis in Caesar II Follow steps shown in Fig. 2 Fig. 2: Steps for creating harmonic input The effect of damping on the response Fig. 3: Effect of Damping The Frequency-phase Dialog Fig. 4: The frequency phase dialog Harmonic Analysis Results Review Results-Displacements: Fig. 5: Nodal Movements in Harmonic Analysis Results-Loads: Fig. 6: Loads in Harmonic Analysis Results-Stress: Fig.7: Stress Window of Harmonic Analysis in Caesar II Fig. 8: Occasional Stress Fig. 9: Fatigue Approach Fig. 10: Updated Stress Results Fig. 11: Caesar II Steps for adding Fatigue data Fig. 12: Updated Caesar II output result with Fatigue Data Author: This presentation is prepared by Mr. Deepak Sethia who is working in ImageGrafix Software FZCO, the Hexagon CAS Global Network Partner in the Middle East and Egypt. He has extensive experience in using Caesar II software and troubleshooting.