Analysis of Causes of Abnormal Vibration in Diesel Generator Set During Operation

Analysis of Causes of Abnormal Vibration in Diesel Generator Set During Operation

 

Note: When a running diesel generator set suddenly experiences abnormal shaking, it is necessary to immediately shut it down for inspection. It can only be restarted and used after the cause has been identified and properly addressed. Now, Xiao Huang has summarized years of industry experience and compiled this article for reference only. It is commonly encountered at the engine end, load end, and installation foundation parts.

 

Ⅰ. Uneven Work of Diesel Engine Cylinders (Most common, will cause noticeable shaking and fluctuating speed)

 

1. A cylinder misfires (does not work) / weak power

- Fuel injector stuck, clogged, or dripping: the cylinder does not inject fuel or has poor atomization, only half of the cylinder exerts force, causing severe vibration of the engine body.

- High-pressure oil pipe leaks, plunger wear, delivery valve damage: single-cylinder fuel supply is insufficient.

- Valve leakage, incorrect valve clearance, intake manifold blockage: cylinder compression pressure is insufficient.

- Piston ring breakage, cylinder liner scoring: cylinder pressure is insufficient, lacking power in a single cylinder.

 

2. Imbalanced air intake distribution

If one side of the intake pipe is blocked or half of the air filter is clogged, one side of the cylinder receives insufficient air, resulting in uneven output, causing the unit to shake to one side.

 

3. Fuel injection timing deviation

Fuel pump gear misalignment, coupling wear: some cylinders have incorrect injection advance angles, causing unsynchronized power strokes.

 

II. Mechanical Component Damage or Imbalance

1. Flywheel / crankshaft imbalance, single-side counterweight detachment

Crankshaft balance weight falls off, flywheel cracks, part of flywheel ring gear damaged: one side experiences large centrifugal force when rotating, causing the entire engine to shake.

2. Connecting rod failure (shaking accompanied by abnormal noise)

Single connecting rod bearing wear, bent connecting rod, loose or broken connecting rod bolts: severe vibration occurs on the corresponding cylinder side, accompanied by a "thump thump" impact sound.

3. Fan and pulley eccentricity

One cooling fan blade broken, pulley cracked: rotation is unbalanced, causing obvious shaking.

III. Uneven Forces on the Generator Side

1. Generator rotor eccentricity, bearing wear

Generator bearing clearance too large, partial rotor winding short circuit: shaking worsens under load.

2. Severe three-phase load imbalance

Using only one or two phases with high-power equipment, one phase is overloaded, causing electromagnetic force imbalance: generator end shakes violently, reduces when unloaded.

 

IV. Installation and Vibration Damping Foundation Problems

1. Damper failure

If the rubber pad on one side of the unit base is flattened, cracked, or leaking, support height is inconsistent, causing the unit to tilt and shake during operation.

2. Base/foundation deformation

Concrete foundation cracks or is uneven, base is partially suspended, causing resonance during operation.

3. Cracks on one side of the base beam

Frame welds broken, insufficient rigidity, uneven power transmission, causing abnormal shaking.

Quick and Simple Inspection Steps

1. Observe at no load: if it shakes at no load → engine mechanical/fuel injection fault; if stable at no load but shakes under partial load → three-phase load imbalance or generator fault.

2. Coupling position: maximum vibration at middle → elastic coupling damaged or misaligned.

3. Check vibration dampers: when shut down, see if the heights of all four foot pads are consistent and if there is any damage or collapse.

4. Measure three-phase current: if the difference between three-phase currents exceeds 20%, it indicates load imbalance; adjust electrical equipment accordingly.

 

Danger Reminder

Continuing operation with connecting rod, crankshaft, or coupling faults can easily cause crankshaft fracture or engine explosion, resulting in severe vibration accompanied by metallic abnormal sounds. Immediate shutdown for inspection and repair is required.