Frequency band preservation: pipe design strategy away from resonance

Abstract

In this paper, a design strategy to keep a pipe away from resonance by adjusting retaining clips is presented. The pipe natural frequency is within the band of vibration frequencies generated by mechanical operation, which can cause the resonance phenomenon. The resonance of pipes could bring serious disaster to the mechanical operation. Therefore, the band of vibration frequencies generated by the mechanical operation is defined as the preserved frequency band (PFB). The pipe in engineering has been simplified to a multispan pipe conveying fluid. An integral pipe model of a multispan pipe conveying fluid is established by simplifying the retaining clips. The natural frequencies of a pipe with clips are obtained. The resonance range and safety range of pipe length are defined as the natural frequencies inside and outside the PFB, respectively. The absolute safety length and the absolute resonance length with respect to clip number are derived. Moreover, the influence of the clip stiffness and location on the safety range is determined. The results show that the safety range is significantly changed by adjusting the vertical stiffness, torsional stiffness, and location of the clips. Based on the results, a pipe design strategy is proposed to stay away from resonance and make for a smaller number of clips. Subsequently, a design for an aircraft pipe is carried out as an example. As a result of the design, the natural frequencies of the aircraft pipe are kept away from the PFB. In summary, a design strategy is obtained to avoid resonance for pipes by adjusting the clip stiffness and/or location.