Remote optical methods for vibration monitoring of liquid pipelines

This paper discusses the application of the photomodulation method based on thin holographic films and the laser speckle correlation method for remote optical vibration monitoring of various parts of liquid pumping systems. The paper considers the microstructure of the surface relief of the holographic films used for the photomodulation method and the optical diffraction phenomenon of multi-component light on a refractive cross-grating. The results of monitoring the vibration of the pipeline, pillar, and pump housing of the water pumping system and the pipeline of the technical oil pumping system in various operation modes using the proposed methods are given. The results of experiments aimed at determining the resolution of the oscillation frequency for the photomodulation method are also presented. The achieved maximum difference in the readings of both methods for determining the first harmonic of oscillations was 0.103 Hz. The results obtained by the photomodulation method demonstrated high convergence with similar results obtained by the laser speckle correlation method. A conclusion is made about the possibility of applying the photomodulation method based on thin holographic films as a vibration visualization technique for technological equipment monitoring.