Experimental modal analysis of electrical submersible pumps

The dynamic behaviour of an electrical submersible pump (ESP) under operational conditions installed in a test well is investigated by identification of its natural frequency and damping parameters. The study is conducted using an experimental modal analysis technique, the Least Square Complex Exponential (LSCE) method. The excitation was generated at one single point, because of the boundary conditions, by an impact hammer (i.e., single-input, multiple-output, or SIMO, analysis was performed), and the response signals were acquired by accelerometers fixed over the pump housing, thereby characterizing output-only processes. To evaluate the complex exponential function to fit the autoregressive function used to model the impact response function (IRF), auxiliary criteria, the averaged normalised power spectrum density (ANPSD) were used. Results have shown that the ESPs would have natural frequencies within the operational frequency range, from 30 to 62 Hz, leading to the operation in resonance conditions.