INFLUENCE OF FREQUENCY REGULATION ON MAIN PUMP PIPING VIBRATION LEVEL

Issues of reliability and operational efficiency of main pumping units are among the most important in the pipeline transport of oil and petroleum products. In most cases, the failure of the unit is preceded by a sharp increase in the vibration level. With a long service life of pumping equipment, the frequency components of vibration increase linearly and rather slowly over time, and then a strong increase in oscillations begins, which ends in failure. In this case, it is necessary to take into account the influence of a number of external influences that lead to an increase in vibration of pumping equipment - induced vibrations from other equipment, vibration of the pipeline system, including hydrodynamic origin, etc. In practice, vibration of process pipelines piping pumping units can often reach significant values and cause destruction of elements of the associated pumping equipment. A common type of failure in such installations is the shutdown of the pumping unit due to the vibration level, or, in the worst case, depressurization of flow paths due to fatigue failure of pipelines. In this case, determining the frequencies of free vibrations of the elements of the pipeline system should be the first stage of studying its dynamics, which is often neglected both at the design stage and during operation. The article is devoted to the analysis of the causes of high vibration levels of the piping of the main pumping unit with frequency regulation. A classical calculation of the natural vibration frequencies of pump piping pipelines revealed their closeness to the reverse frequency of the pump unit in a number of modes. Under the condition of using frequency regulation of the operating modes of the pumping unit, the rotor speed in a sufficiently wide range can approach or coincide with the natural frequency of piping vibrations. As a result of the conducted analysis of the frequency spectrum when changing the number of revolutions of the rotor of the main pumping unit, their unacceptable range was revealed from the point of view of the known conditions for the occurrence of resonance and an increase in the amplitude of vibration displacement of the piping above the permissible level.