Reasons for Excessive Vibration of Silent Generator Sets

Vibration is an important indicator for measuring the working quality of an engine. Excessive vibration can accelerate the fatigue damage of machine parts and reduce the working lifespan of the engine. Excessive engine vibration will affect the accuracy and indication of instruments. Moreover, when a significant vibration occurs, vibration noise will be generated, which can seriously affect the daily work and life of nearby residents. So, what causes the excessive vibration of a silent diesel generator set? Generally speaking, the vibration fault of a diesel generator set is caused by unbalance of the rotating part, electromagnetic problems, or mechanical failures.

Unbalance of the rotating part of the silent generator

It is mainly caused by the unbalance of the rotor, coupling, shaft coupling, and driving wheel (brake wheel). The treatment method is to first balance the rotor. If there are large driving wheels, brake wheels, couplings, and shaft couplings, they should be balanced separately from the rotor. Another cause is the looseness of the mechanical parts of the rotating part. For example, the looseness of the iron core support, the failure and looseness of the inclined key and dowel pin, and the loose binding of the rotor can all cause the unbalance of the rotating part.

Electrical faults of the silent generator set

These are caused by electromagnetic reasons and mainly include: incorrect stator wiring of an AC diesel generator set, short circuit in the rotor winding of a wound asynchronous motor, inter-turn short circuit in the excitation winding of a synchronous diesel generator, incorrect connection of the excitation coil of a synchronous diesel generator, broken bars in the rotor of a squirrel-cage asynchronous motor, and the deformation of the rotor iron core, which causes uneven air gaps between the stator and the rotor, resulting in unbalanced air gap magnetic flux and thus vibration.

Mechanical faults of the silent diesel generator

1.Misalignment of the shaft system of the linked parts, non-coincidence of the centerlines, and incorrect centering: The main reason for this kind of fault is poor alignment and improper installation during the installation process. Another situation is that the centerlines of some linked parts coincide when cold, but after running for a period of time, due to the deformation of the rotor support points and the foundation, the centerlines are damaged again, thus generating vibration.

2.Problems with the gears and couplings connected to the generator: This kind of fault is mainly manifested as poor gear meshing, severe tooth wear, poor lubrication of the coupling, skewness and misalignment of the coupling, incorrect tooth shape and pitch of the toothed coupling, excessive clearance or severe wear, all of which can cause a certain degree of vibration.

3.Defects in the structure of the silent diesel generator itself and installation problems: This kind of fault is mainly manifested as an elliptical journal, a bent rotating shaft, too large or too small clearance between the shaft and the bearing bush, insufficient stiffness of some parts of the bearing seat, base plate, foundation, or even the entire generator installation foundation, poor fixation between the generator and the base plate, loose bottom bolts, and looseness between the bearing seat and the base plate. Moreover, too large or too small clearance between the shaft and the bearing bush can not only cause vibration but also cause abnormalities in the lubrication and temperature of the bearing bush.

4.Vibration transmitted from the load driven by the silent diesel generator: For example, the vibration of the steam turbine of a turbo generator, and the vibration of the fan and water pump driven by the generator can cause the generator to vibrate.

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