Necessity and Precautions for Regular Maintenance of Diesel Generator Sets

Main Maintenance Items for Diesel Generator Sets
Daily Maintenance of Storage Battery
Starting‑battery failure is a common issue. Without regular maintenance, electrolyte water evaporates without timely replenishment. If no dedicated charger is equipped, the battery will gradually lose power due to self‑discharge. Some chargers require manual switching between equalizing charge and float charge. Insufficient battery capacity will result if such operation is neglected. To solve this problem, high‑quality chargers shall be equipped, and necessary inspection and maintenance shall be performed.
Timely Refill Cooling Water for Radiator
Temperature variation causes moisture in air to condense into water droplets adhering to inner fuel‑tank walls and mixing with diesel fuel. Excessive water content in diesel will corrode precision coupling parts such as plungers inside high‑pressure fuel pumps and may severely damage the unit. Regular maintenance can effectively prevent such failures.
Periodic Engine‑oil Replacement
Engine oil provides lubrication for mechanical components, yet it has a limited service life. Long‑term storage changes its physical and chemical properties, deteriorating lubrication during operation and potentially causing component damage. Therefore, lubricating oil shall be replaced on a regular basis.
Replacement of Four Filters (Diesel‑oil Filter, Engine‑oil Filter, Air Filter, Water Filter)
These filters block impurities from entering the unit. Contaminants inevitably exist in diesel fuel. During unit operation, filters trap dirt and impurities, which gradually build up on filter screens and reduce filtering capacity. Excessive deposits will block oil passages and cause unit shutdown under load due to fuel shortage, similar to human oxygen deprivation.
Recommendations for normal generator sets:
‑ For frequently‑run units: replace the four filters every 500 operating hours.
‑ For standby units: replace the four filters every two years.
Scheduled Cleaning of Cooling System
Long‑term neglect of water pumps, radiators and pipelines leads to poor water circulation and reduced cooling efficiency. Check pipe‑joint conditions and look for radiator or pipeline leakage. Cooling‑system faults may cause two major consequences:
‑ Overheating and unit shutdown due to poor heat dissipation.
‑ Insufficient water level caused by radiator leakage leading to unit malfunction.
A water heater is recommended for the cooling system to prevent pipeline freezing in winter.
Lubricant Supplement
Chemical properties of lubricants plus iron filings generated by mechanical wear degrade lubrication performance and accelerate component wear. Lubricants also corrode rubber sealing rings, and oil seals age over time, weakening sealing performance.
Regular Sediment Removal
Engine power output relies on fuel combustion inside cylinders. Fuel is injected via nozzles, and carbon deposits gradually accumulate on injector nozzles. Heavy carbon deposits distort fuel‑injection volume and timing, causing uneven fuel supply among cylinders and unstable engine operation. Regular cleaning of the fuel system, replacement of filter components for smooth fuel supply, and adjustment of gas distribution system guarantee uniform ignition.
Inspect Normal Operation of AVR Module
The control system is a vital maintenance point. Long‑term operation may loosen wire connectors. Verify that the AVR module works properly.
Ten Detailed Rules for Generator Set Maintenance & Overhaul
Perform level‑3 maintenance every half‑month, lasting 4 hours; run trial operation for 15 minutes and record relevant operating parameters.
Annual maintenance shall be submitted to superior company for approval.
Inspect according to specifications: ensure smooth smoke‑exhaust system; intact ventilation, exhaust and supply fans with unobstructed airflow; functional room lighting and emergency lights.
Check battery liquid level on schedule; add electrolyte if insufficient, measure specific gravity and charge as required, and keep records.
Remove air, oil and diesel filters periodically; clean with gasoline and remove dust. Replace engine oil if deteriorated or turbid.
Replace radiator cooling water on schedule and measure generator insulation resistance.
Keep generator‑room floor and walls clean; ensure no oil contamination or fluid leakage on units.
Implement corresponding emergency measures in case of typhoon, fire, rainstorm or earthquake.
Complete maintenance records shall be filed and preserved.
Assign professional technicians for unit operation and maintenance.
Daily and Weekly Maintenance Contents
Daily Maintenance
Review generator daily‑operation reports.
Check engine‑oil level and coolant level.
Inspect the unit for damage and leakage; check whether belts are loose or worn.
Weekly Maintenance
Repeat daily Grade‑A inspection items.
Inspect air filter; clean or replace filter cartridge.
Drain water and sediment from fuel tank and fuel filter.
Check water filter.
Inspect starting storage battery.
Start generator and check for abnormal conditions.
Clean heat‑dissipation fins on front and rear sides of cooler.
Maintenance Levels for Diesel Generator Sets
Grade‑B Maintenance
‑ Repeat Grade‑A daily and weekly inspections.
‑ Replace engine oil (every 250 operating hours or one month, whichever comes first).
‑ Replace engine‑oil filter (every 250 operating hours or one month).
‑ Replace fuel‑filter cartridge (every 250 operating hours or one month).
‑ Replace or inspect coolant; add DCA coolant additive when changing water‑filter cartridge (every 250‑300 hours).
‑ Clean or replace air filter (every 500‑600 operating hours).
Grade‑C Maintenance
‑ Replace diesel‑oil filter, engine‑oil filter and water filter; replace radiator water and engine oil.
‑ Adjust fan‑belt tension.
‑ Inspect turbocharger.
‑ Dismantle, inspect and clean PT pump and actuator.
‑ Remove rocker‑arm cover; inspect toggle plates, valve guides and intake/exhaust valves.
‑ Adjust injector lift and valve clearance.
‑ Inspect charging generator.
‑ Inspect and externally clean radiator; add radiator corrosion inhibitor and clean radiator interior.
‑ Inspect diesel‑engine sensors and connecting wires.
‑ Inspect diesel‑engine instrument cabinet.
Grade‑D Maintenance
‑ Replace engine‑oil filter, diesel‑oil filter, bypass filter and water filter; renew engine oil and circulating cooling water.
‑ Clean or replace air filter.
‑ Remove rocker‑arm cover; inspect valve guides and toggle plates.
‑ Inspect and adjust valve clearance.
‑ Replace upper and lower rocker‑arm cover gaskets.
‑ Inspect fan and bracket; adjust belt tension.
‑ Inspect turbocharger.
‑ Inspect diesel‑engine electrical circuits and generator‑excitation wiring.
‑ Inspect wiring connections inside instrument cabinet.
‑ Inspect radiator and perform external cleaning; repair or replace water pump if necessary.
‑ Dismantle and inspect wear of main‑shaft bearing and connecting‑rod bearing of one cylinder.
‑ Inspect or adjust electronic governor performance.
‑ Apply grease to generator lubrication points.
‑ Remove dust from generator‑excitation components.
‑ Measure turbo‑charger axial and radial clearances; repair if beyond tolerance.
‑ Clean and calibrate fuel injectors and fuel pump.
Conventional Routine Maintenance
1. Daily Maintenance Work
Review previous‑day operation reports.
Check for leakage of engine oil, cooling water and diesel fuel.
Check liquid levels of engine oil, cooling water and diesel fuel.
Inspect water heater.
Check selector‑switch position of automatic transfer switch (ATS).
Measure battery voltage and verify charger operation.
Fill in daily operation reports.
2. Contents of Daily Operation Report
‑ Inspection items, especially abnormal conditions, completed repairs and notes for follow‑up personnel.
‑ If unit is started: record three‑phase voltage, current, frequency, power, power factor, running hours, engine water temperature, engine‑oil pressure and DC battery voltage.
‑ Engine vibration, noise and exhaust‑smoke status.
3. Weekly (every 10‑day) Maintenance Work
Repeat all daily‑maintenance items.
Inspect air filter.
Inspect fuel‑tank bottom; drain sediment and water.
Drain sediment and water from diesel filter.
Run generator for 20‑30 minutes, inspect operating status and keep startup records.
4. Semi‑annual Maintenance (every 250 operating hours, whichever comes first)
Repeat daily and weekly maintenance.
Replace engine oil and engine‑oil filter.
Check coolant‑additive concentration; replace water filter.
Inspect fan‑belt condition.
Inspect charging‑generator belt condition.
Check radiator surface and clean when necessary.
Replace air filter.
Replace diesel‑oil filter.
Inspect integrity of water‑pipe connections.
Inspect diesel fuel transfer pump.
Clean crankcase breather.
Inspect tightness of high‑voltage and low‑voltage cable joints.
Simulate mains‑power failure to test automatic startup and transfer functions of ATS and generator‑set system.
5. Annual Maintenance (every 1500 operating hours, whichever comes first)
Repeat daily, weekly and semi‑annual maintenance items.
Inspect fuel injectors and intake‑exhaust valve clearance; adjust valve clearance.
Check and retighten turbocharger fastening bolts.
Inspect water heater.
Run unit under 50%‑80% rated load for 3 hours to evaluate overall performance.
Pre‑start‑up Inspection
Clear sundries in generator room, especially near engine fan.
Check liquid levels of engine oil, diesel fuel and cooling water.
Remove obstacles at air‑intake and exhaust passages; guarantee good ventilation.
Check tightness of battery‑cable connectors.
Confirm closing‑opening position of circuit breaker.
Verify on‑off status of diesel‑supply pipeline valves.
Review generator‑set operation reports.
Inspection After Startup
1. No‑load Inspection
Check abnormal noise and vibration.
Monitor engine‑oil pressure.
Close breaker for power supply only after voltage and frequency stabilize.
2. On‑load Inspection
Check noise and vibration.
Monitor engine‑oil pressure.
Monitor voltage and frequency.
Monitor power and power factor.
Check three‑phase‑current balance.
Estimate remaining diesel endurance according to real‑time power load.
Pre‑shutdown Inspection
Confirm all loads have been switched back to mains power supply.
Run unit under no‑load for 5 minutes in winter or 10 minutes in summer before shutdown.
Inspection Before Leaving Generator Room After Shutdown
Confirm AC‑220 V battery‑charger working status.
Confirm water‑heater working status.
Check ATS‑panel selector‑switch position and main‑switch status.
Confirm RUN/AUTO/OFF selector‑switch position of generator set.
Check diesel‑valve status and residual fuel volume inside fuel tank.
Complete generator‑set operation reports.
Supplementary Notes
1. Cooling Water
Fill water in 2‑3 batches. After first filling, wait 10‑20 minutes and top‑up again; confirm no water‑level drop within 10‑20 minutes.
Keep water level 20‑30 mm below radiator top.
Use soft water; add corrosion‑inhibitor and anti‑scaling agent per Perkins specifications; add antifreeze according to ambient‑temperature requirements.
Keep radiator exterior clean.
2. Diesel Fuel
Adopt 0# /‑10# diesel fuel; drain tank‑bottom sediment timely; pay attention to fuel storage period.
Guarantee qualified fuel source.
3. Storage Battery
Normal static voltage: single‑battery 12.5‑12.8 VDC; dual‑battery group 25.0‑25.6 VDC. Measure 30 minutes after charger is switched off.
Charging voltage: single‑battery 13.0‑13.5 VDC; dual‑battery group 26.0‑27.0 VDC; shall not exceed 14.0 VDC / 28.0 VDC.
General service life of storage battery: 1‑2 years.
Constant‑current chargers are prohibited.
4. Engine Oil
Use qualified products and replace oil when service life expires.
Strict implementation of above‑mentioned measures ensures reliable winter‑time operation and extends service life of generator sets and engines.