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Reasons and Solutions for Diesel Generator Set Vibration

Nov. 05, 2018

The structure of the generator contains both electrical and mechanical parts, which can also be said to be a combination of mechanical and electrical. Therefore, its failure is divided into two analysis. The cause of the vibration fault of the generator is also divided into two parts. In general, generator vibration is caused unbalanced, electromagnetic or mechanical failure of the rotating part.

 


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1. The unbalance of the rotating part is mainly caused by the imbalance of the rotor, the coupler, the coupling, and the transmission wheel (brake wheel). the treatment method is to find the rotor balance first. If there are large drive wheels, brake wheels, couplers, and couplings, separate the balance from the rotor. If there are large transmission wheels, brake wheels, couplings, separate and separate from the rotor to find a good balance. Then there is the mechanical looseness of the rotating part. For example, the iron core bracket is loose, the oblique key and the pin are loose, and the rotor is not tied tightly, which will cause the rotating part to be unbalanced.

 

The main problems of mechanical parts are as follows:

 

1. The linkage part of the shaft system is misaligned, the center line does no coincide, and the centering is incorrect. The cause of this failure is mainly caused by poor alignment and improper installation during the installation process. There is also a case where some of the center lines of the interlocking parts are coincident in the cold state, but after a period of operation, the center line is broken due to the deformation of the rotor fulcrum and the foundation, thereby generating vibration.

 

2. Gears and couplings associated with generators are faulty. This kind of failure mainly manifests as poor gear occlusion, serious tooth wear, poor lubrication of the wheel, skewing and misalignment of the coupling, tooth profiles of the gear coupling, incorrect tooth pitch, excessive clearance or serious wear, which will cause certain vibration.

 

3. The load dragged by the generator conducts vibration. For example, the turbine vibration of a steam turbine generator, the fan driven by then motor, and the vibration of the water pump cause vibration of the motor.

 

4. Defects in the structure of the generator itself and installation problems. This kind of failure mainly manifests as the ellipse of the journal, the bending of the shaft, the gap between the shaft and the bearing bush is too large or too small, and the rigidity of the bearing seat, the foundation plate, a part of the foundation and even the entire generator installation foundation insufficient, and generator and the base plate are insufficient. The fixing is not strong, the foot bolts are loose, and the bearing seat and the base plate are loose. The excessive or too small gap between the shaft and the bearing bush can not only cause vibration but also cause abnormal lubrication and temperature of the bearing bush.

 

The failure of the electrical part is caused by electromagnetic causes

 

1. Mainly include short-circuit of rotor winding of winding type asynchronous motor, stator wiring error of AC motor, turn-to-turn short circuit of synchronous motor excitation winding, misalignment of excitation coil of synchronous motor, rotor broken strip of cage asynchronous motor, rotor core deformation caused by stator and rotor air gap unevenness causes the air gap flux to be unbalanced and cause abnormal vibration.

 

When using the diesel generator set, the user will encounter abnormal noise and excessive vibration during the operation of the diesel engine. The following is the answer to the reasons and troubleshooting methods.

 


Fault Characteristics


Possible Reason


Method of Exclusion


 

A rhythmic crisp metal knock in the cylinder

 

 

Fuel pump static oil supply timing is too early

 

Adjust the static fuel supply advance angle of the fuel injection pump

 

A low, unclear knocking sound in the cylinder

 

 

Fuel injection pump static oil supply timing is too late

 

 

Adjust the static fuel supply advance angle of the fuel injection pump

 

Slight and sharp sound during operation, especially at idle speed

 

The piston pin and the connecting rod small head bushing hole are too large

 

Check the inner hole of the connecting rod bushing for wear, if any, replace the connecting rod

 

Heard the impact on the outer wall of the cylinder during operation

Sound, decreasing as the temperature of the diesel engine increases

 

Excessive clearance between piston and cylinder liner

 

Replace the piston or replace the cylinder liner depending on the wear condition

 

During operation, a crash sound is heard in the crankcase.

When the diesel engine suddenly drops from 1000 r/min

Hear heavy and powerful crashes at speed

 

The wear of the connecting rod bushing makes the matching clearance too large

 

Check the axial clearance and the degree of wear of the thrust bearing and replace the thrust bearing if necessary

 

A rhythmic slight knock on the cylinder head

 

The valve spring is broken, or the tappet is bent, or

Putter sleeve wear or valve damage

 

Replace damaged parts and adjust valve clearance

 

Heavy duty at the cylinder head during operation of the diesel engine

Even, rhythmic percussion, with your hands

Means that the nut that gently grips the cylinder head cover has

Collision feeling

 

Valve touch piston

 

Remove the cylinder head cover, check the cause of the collision, and adjust the valve clearance. Check if the piston model is correct if necessary

 

An abnormal sound is emitted at the front cover, and a crash can be heard when the speed is suddenly reduced.

 

Drive gear wear and excessive backlash

 

Check the backlash and replace the gear depending on the wear

 

Hearing dry friction at the cylinder head

 

Rocker adjustment screw and spherical seat of the push rod

Inorganic oil

 

Remove the cylinder head cover and check the cause of the oil cut

 

heard a loud rhythm at the cylinder head

 

Inlet and exhaust valve clearance is too large

 

Check and adjust valve clearance.

 

A loud, rhythmic noise was heard at the cylinder head

 

Intake, exhaust valve clearance is too large.

 

Check and adjust valve clearance.

 

The turbine has an abnormal rubbing sound while it is running.

 

 

Oil path clogging, poor lubrication, resulting i bearing wear, resulting in impeller blade bending.

 

 

Let professional maintainers check bearing wear, impeller blade bending, and replace supercharge if necessary. Clean the supercharger in and out of the pipeline to ensure the smooth flow of lubricating oil channels.

 

The combustion noise is too great

 

(1) Poor fuel quality

(2) Injection pump failure

 

Remove fuel from the tank and replace the fuel filter. High quality clean fuel is injected into the fuel tank to make the diesel engine operate under the condition of maximum combustion noise, and then unscrew the nozzle nuts of each cylinder of the fuel injection pump one at a time. If the pipe nut is loosened and the combustion noise disappears, the piston pair of the cylinder injection pump is inspected and new parts are replaced if necessary.

 

Diesel engine severe vibration

(1) A single or multi-cylinder injection or fuel injection pump plunger does not work.

 

(2) Loosening of fixed bolt of diesel engine and seat.

 

Repair or replacement of injectors, fuel injection plunger or fuel injection pump.

Tighten the fastening nut of the diesel engine and the seat.

 

 

 

 


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