Daily Maintenance of Diesel Generator Sets

A diesel generator set mainly consists of three major parts: diesel engine assembly, generator, and control system.

The diesel engine assembly serves as the power unit of the generating set. It converts chemical energy into mechanical energy, and is composed of mounting system, cooling system, air intake & exhaust system and electrical system, driven by diesel fuel.

The generator comprises bearings, end covers, stator and rotor.

The control system of the diesel generator set is relatively precise and complex, performing precise control, pressure regulation and power distribution.

(1) Multiple single‑unit capacity grades. Its single‑unit capacity covers from tens of kilowatts to tens of thousands of kilowatts with wide selection range, which can satisfy power‑consuming loads of different capacities.

(2) Compact supporting structure. Compared with other power‑generating equipment with complicated auxiliary facilities, diesel generator sets feature small footprint and light weight. Simple auxiliary structures reduce land occupation and cut investment costs.

(3) Good energy‑saving performance and low fuel consumption. The thermal efficiency of its diesel engine reaches around 40 %, which brings low fuel consumption and realizes energy conservation and cost reduction.

(4) Fast start‑up response. Under normal conditions, the unit can start within several seconds. Under emergency‑response mode, full‑load output can be achieved within 1 minute; under normal non‑emergency conditions, full‑load operation is realized within 5‑30 minutes. Its shutdown time is also very short, generally within 30 seconds.

(5) Simple operation and maintenance. It can be operated by one single person. Maintenance shall be carried out in accordance with specifications in the operation manual, requiring little special training for operators.

Starting failure is one of the most frequent faults, divided into manual start failure and electric start failure.

Manual start failure is mostly caused by worn or broken pull‑ropes. Operators shall inspect and repair according to inspection results.

Electric start involves more components including start switch, storage battery, fuel solenoid valve, etc., leading to more complex faults, mainly categorized as four types:

(1) Storage‑battery failure. Battery voltage shortage will reduce cranking speed of the starting motor and hinder unit start‑up. Real‑time battery charging is essential. Most modern diesel engines support automatic battery charging; however, loose wiring caused by vibration may disable charging and shall be checked.

(2) Solenoid switch fault. When battery voltage remains sufficient yet the solenoid switch fails to pull‑in despite power supply, the solenoid switch is likely damaged. Professional personnel shall inspect for mechanical wear and replace defective components to avoid secondary losses.

(3) Starting module fault. Defective starting module causes unstable voltage and abnormal power supply for fuel solenoid valve. The motor may still run, yet long‑term operation will severely shorten generator service life. Replace the faulty starting module to restore normal operation.

(4) Fuel solenoid‑valve fault. As a critical control component, fuel solenoid‑valve failure triggers low and fluctuating voltage and disrupts fuel supply. For this structurally simple component, repair shall be prioritized over replacement principle in maintenance.

Three frequent faults for generator control box:

(1) Stator demagnetization, which disrupts power generation. Re‑magnetize the stator with dry‑cell batteries.

(2) Damaged or bent rotor shaft, resulting in generator start‑up failure. Repair or replace relevant components.

(3) Unstable output voltage, which is generally induced by excitation faults or single‑phase earthing faults. Troubleshoot root causes before conducting maintenance.

Three types of alarm lamps: shutdown lamp, fault‑warning lamp and maintenance‑reminder lamp. Immediate response shall be taken once any lamp lights up.

Red alarm indicates level‑one emergency status, such as extremely low oil pressure or excessive water temperature. Shut down the unit immediately and arrange professional repair.

Yellow alarm usually points to sensor fault, moderately low oil pressure or slightly over‑range coolant temperature. Operators shall unload the unit and send it for repair before resuming operation.

White lamp signals required maintenance, e.g. over‑limit water accumulation inside water‑oil separator. Never ignore white alarms. Neglect may lead to engine damage and even personal injury accidents.

[1] Zeng Chunxiang. Maintenance and Management of Diesel Generator Sets[J]. Engineering Technology, 2016(5):219.

[2] Xu Guangjing. Research on Fault Repair and Maintenance of Diesel Generator Sets[J]. Internal Combustion Engines & Parts, 2018(7):28.

[3] Wang Peng. Common‑fault Diagnosis and Maintenance for Diesel Generator Sets[J]. Engineering Technology: Citation Version, 2016(3):201.