In order to facilitate the analysis and judgment of the causes of foundation vibration, the vibration of the cylinder, fuselage, bearings, etc. of the air compressor was measured using a vibration meter, and its amplitude and vibration speed were measured. Reason 2: The air compressor design data provided by the manufacturer. Since the center of gravity of the foundation of this unit and the center of gravity of the compressor did not coincide, the first-order reciprocating inertia force in the horizontal direction was transferred to a part in the vertical direction, which aggravated the vibration of the foundation. This is the second reason for the excessive vibration of the foundation.
Treatment measures and effects There are two remedial measures for the above reasons, one of which is to widen the foundation so that the center of gravity of the widened foundation coincides with the center of gravity of the air compressor. This requires the destruction of the existing cement floor. Due to the intricate pipelines, cables, optical cables, etc. under the ground, excavation is difficult, and the main project of the 400,000 t/a diesel hydrotreating unit is imminent. It takes a long time to widen the foundation again, so it is not suitable.
According to the analysis of the second reason, it can be known that the rotational inertia force generated by the crankshaft rotational weight only needs to be balanced and offset in the machine, and the first-order reciprocating inertia force does not require any balancing method, so it is only necessary to change the mass of the balancing weight from the original 68kg to 40kg. After the modification of the balancing weight, the foundation vibration condition has been greatly improved. After measurement by the vibration meter, the amplitude and vibration velocity values in the three directions of X, Y, and Z are in line with the provisions of GB7777-87/Mechanical Vibration Measurement and Evaluation Standard for Reciprocating Piston Compressors 0, which ensures the successful commissioning of this device, provides support for the smooth commissioning of the main project, and creates considerable economic benefits for the refinery.
Conclusion When the center of gravity of the foundation and the center of gravity of the air compressor fail to coincide for some reason, resulting in excessive vibration of the foundation, the setting of the balancing weight only needs to balance the rotational inertia force generated by the crankshaft rotational weight, and no balancing measures are required for the first-order reciprocating inertia force. When the center of gravity of the foundation coincides with the center of gravity of the compressor, the best practice is to balance the rotational inertia force generated by the rotating mass of the crankshaft, and then transfer the first-order reciprocating inertia force in the horizontal direction (30%-50%) to the vertical direction by adding a balancing weight to reduce horizontal vibration.