Diesel generator sets play an indispensable role in industrial production, construction, and emergency backup power supply. However, like all mechanical equipment, diesel generator sets may encounter various problems during long-term operation, with abnormal noises being a common and easily noticeable phenomenon. These noises not only affect the normal operation of the equipment but may also indicate potential failure risks. This article will provide a detailed introduction to the types, causes, and solutions of common abnormal noises in diesel generator sets, helping users better maintain and manage their generator sets.
When a diesel generator set suddenly decelerates from high speed to low speed, a "clang, clang, clang" impact sound can be heard from the upper part of the diesel engine cylinder. This sound is usually caused by excessive clearance between the piston pin and the connecting rod bushing. Under sudden speed changes, the piston pin can experience lateral dynamic imbalance. This means that the piston pin not only rotates within the connecting rod bushing but also swings from side to side, colliding with the bushing and producing noise.
If this abnormal noise is not addressed promptly, it may lead to more serious failures, causing unnecessary waste and economic losses. Therefore, once this noise is detected, the piston pin and connecting rod bushing should be replaced immediately to ensure the normal operation of the diesel generator set. Replacing these components can not only eliminate the noise but also prevent more complex problems caused by excessive wear of the parts.
During the operation of a diesel generator set, especially under high load conditions, a heavy, dull knocking sound may be heard from the lower part of the diesel engine block. This sound is usually caused by abnormal friction between the main bearing and the crankshaft journal. The main reason is the excessive clearance between the crankshaft journal and the main bearing, leading to uneven wear and thus producing this abnormal friction and knocking sound.
Once this sound is heard, the operation of the diesel generator set should be stopped immediately. If it continues to run without inspection and repair, serious accidents such as "bearing seizure" or "shaft burning" may occur. To avoid this situation, the main bearing bolts should be checked immediately for looseness. If the bolts are not loose, the crankshaft and main bearings or main bearing shells should be removed and measured by professionals. By comparing the measured clearance values with the specified data and checking the wear conditions of the crankshaft and bearing shells, repairs or replacements should be carried out if necessary.
During low-speed (idle) operation of the diesel engine in a diesel generator set, a "click, click" metallic knocking sound may be heard near the valve cover. This sound is caused by the impact between the valve and the rocker arm, mainly due to excessive valve clearance. Valve clearance is a major technical parameter of the diesel engine, and both excessive and insufficient clearance can affect its normal operation.
When the valve clearance is too large, the displacement between the rocker arm and the valve is greater, and the impact force generated during contact is also larger, resulting in a metallic knocking sound. This sound often occurs after the engine has been running for a long time. To avoid this situation, the valve clearance should be readjusted every 300 hours of engine operation. Correct valve clearance can ensure the normal opening and closing of the valves, thereby guaranteeing the performance and efficiency of the diesel engine.
During the operation of a diesel generator set, a crisp knocking sound of the piston hitting the cylinder wall, known as "knocking cylinder," can be clearly heard from the upper part of the cylinder. The root cause of this fault is the insufficient fuel injection advance angle of the diesel engine. The fuel injection advance angle is a major technical parameter of the diesel engine, which directly affects its normal operation and power output.
When the fuel injection advance angle is too small, the combustible gas formed by the fuel injected into the cylinder burns unstably. During the upward stroke of the piston, the gas produced by combustion may cause the piston to shift laterally and collide with the cylinder wall, resulting in the knocking cylinder sound. To avoid this fault, the fuel injection advance angle needs to be adjusted to ensure the normal formation and combustion of the air-fuel mixture. The correct fuel injection advance angle can improve the efficiency and performance of the engine and reduce the occurrence of faults.
When the load of a diesel generator set suddenly changes, a dull knocking sound may be heard near the engine block. This sound mainly originates from abnormal friction between the crankshaft connecting rod journal and the connecting rod bearing, mainly due to the excessive clearance between them, causing local jumping. The mechanism of this abnormal noise and the maintenance and inspection methods are exactly the same as those for the main shaft and main bearing.
To avoid this fault, the clearance between the crankshaft connecting rod journal and the connecting rod bearing should be checked regularly. If the clearance is found to be too large, repairs or replacements should be carried out promptly. The correct clearance can ensure the normal operation of the crankshaft and connecting rod, reduce wear, and extend the service life of the equipment.
A "howling" sound may be heard at the front cover of the diesel engine in a diesel generator set. This sound comes from the meshing gears inside the front cover. When the gears of the meshing gears are excessively worn, the clearance between the gears becomes too large, causing the gears to fail to mesh normally and thus producing this noise.
To eliminate this abnormal noise, the front cover should be opened, and the meshing condition of the gears should be checked with lead sheets or paint and adjusted. If the gear clearance is too large, new gears should be replaced promptly. Correct gear meshing can ensure the normal operation of the transmission system, reduce noise and vibration, and improve the operating efficiency of the equipment.
In addition to the above common noises, diesel generator sets may also exhibit other unusual sounds that require attention and prompt troubleshooting. Some of the more common ones include:
High-frequency "ticking" or irregular knocking from the valve area or upper engine body
Dull "clunking" inside the engine body
"Clicking" gear noise at the front cover
Squeaking or "thumping" at the diesel-generator coupling
"Piston knock" inside the cylinder
Continuous noise inside the generator after shutdown
Piston crown hitting the cylinder head
Piston ring-related noise
Although the abnormal noise problems of diesel generator sets are complex and diverse, most problems can be solved by careful observation and analysis. Regular maintenance and inspection are the keys to preventing abnormal noises and failures. Users should develop a reasonable maintenance plan based on the usage and operating time of the equipment, and promptly identify and deal with potential problems. At the same time, when abnormal noises occur, the machine should be stopped immediately for inspection to avoid continued operation of the equipment in a faulty state, which could cause greater losses. Through proper maintenance and timely repairs, the service life of diesel generator sets can be effectively extended, ensuring their stable and efficient operation in various application scenarios.
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