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Operation and Maintenance of Diesel Generators – Part 3: Understanding Starting system and Lubrication system of Diesel Generators

  Part 3: Understanding Starting system and Lubrication system of Diesel Generators

A diesel generator (DG) set consists of multiple subsystems that work together to ensure reliable and efficient power generation. Among these, the starting system and lubrication system are critical for initiating engine operation and maintaining smooth performance. A well functioning starting system ensures that the generator cranks up efficiently, while an optimized lubrication system reduces friction, dissipates heat, and extends engine life.

In this third part of the Operation and Maintenance of Diesel Generators Series, we will focus on the starting system and lubrication system, their key components, functions, and maintenance best practices. If you haven’t read the previous parts, check them out here:

Part 1: Operation and Maintenance of Diesel Generators – Part 1: Understanding Diesel Engine, Its Working Principle and Key Components

Part 2: Operation and Maintenance of Diesel Generators – Part 2: Understanding Alternator, Its Components, and Working Principle

Subsystems of a DG Set

The engine process in a DG set is categorized into five major subsystems:

  1. Starting System – Powers the initial cranking of the engine.
  2. Lubrication System – Ensures smooth operation by reducing friction and cooling engine components.
  3. Fuel Injection System – Supplies and injects diesel fuel for combustion.
  4. Cooling System – Maintains optimal engine temperature and prevents overheating.
  5. Air Inlet and Exhaust System – Manages the intake of clean air and expulsion of exhaust gases.

Each of these systems is critical for the generator’s performance and must be maintained properly to ensure optimal efficiency, fuel economy, and engine life.

Starting System

The starting system is responsible for initiating the engine’s operation by cranking it into motion. It comprises the battery system and starter motor, which work together to provide the necessary energy to turn the crankshaft and start the engine.

Battery System

The battery supplies direct current (DC) power to crank the engine and is also used for powering control circuits. The capacity of the battery required depends on the generator’s size:

  • Below 500 kVA: 24V DC, 180AH battery.
  • Above 500 kVA: 24V DC, 360AH battery.

Battery Condition and Maintenance
  • A healthy battery should provide 24V at no load.
  • 25V to 27V indicates an optimal charge level, ensuring reliable cranking.
  • Battery voltage should be monitored regularly using a multimeter to prevent failures.
Specific Gravity (S.G.) of Battery Electrolyte

The specific gravity (S.G.) of the battery electrolyte determines its charge status. A hydrometer is used for measurement, and the ideal S.G. range is 1.22 to 1.25 (1220 to 1250).

Water Level Maintenance
  • Distilled water must be used to prevent contamination.
  • The water level should be between the minimum and maximum markers in lead-acid maintenance batteries to prevent drying out or overfilling.
Starter Motor

The starter motor is an electromechanical device that converts electrical energy from the battery into mechanical energy, enabling the engine to start.
  • When the starter solenoid switch is energized, the pinion gear engages with the flywheel ring gear and rotates it to initiate the engine cycle.
  • The starter motor’s efficiency depends on the battery charge level and voltage stability. If the battery is weak or terminals are corroded, the starter motor will fail to crank the engine effectively.
Maintenance of the Starting System
  • Regular battery voltage checks and electrolyte level monitoring help avoid starting failures.
  • Terminal connections should be kept clean and corrosion free to ensure optimal current flow.
  • Starter motor performance should be tested periodically to detect any signs of malfunction.
Lubrication System

The lubrication system plays a crucial role in reducing friction, heat buildup, and wear and tear in engine components. Proper lubrication ensures the long life and efficiency of a DG set.

Purpose of the Lubrication System
  • Reduces friction between moving parts, minimizing power losses.
  • Prevents excessive wear and tear, prolonging engine life.
  • Acts as an oil seal, preventing unwanted blow by gases from escaping.
  • Dissipates heat, helping maintain the engine’s temperature.
  • Removes contaminants, preventing sludge and carbon deposits.
  • Absorbs shocks and vibrations, cushioning engine components.
Types of Lubrication Used in Diesel Engines
  • Pressure Lubrication – Uses an engine-mounted oil pump to distribute oil to essential components such as the crankshaft, bearings, camshaft, rocker assembly, and turbocharger.
  • Splash Lubrication – Oil is thrown by high speed rotating components, such as the crankshaft, to lubricate pistons, liners, and gear trains.
  • Mist Lubrication – Forms oil droplets (mist) that lubricate valve rockers and small single cylinder engines.
Key Components of the Lubrication System

Oil Pan (Sump)
The oil pan is the storage reservoir for engine oil. It ensures a steady supply of oil to the lubrication system.

Oil Pump
The oil pump is responsible for drawing oil from the oil pan and distributing it throughout the engine via suction tubes and pressure lines.

Pressure Regulating Valve
This valve controls oil pressure within the lubrication system, ensuring a consistent and controlled flow of oil. It is preset by the manufacturer and is usually non-adjustable.

Lubricating Oil Filter
The oil filter plays a crucial role in removing impurities and contaminants from engine oil.
  • Paper element filters are used to trap dirt and foreign particles.
  • Over time, filters become clogged and must be replaced to maintain oil flow.
  • If the filter gets blocked, a bypass valve ensures unfiltered oil is still supplied to critical components to prevent engine damage.
Oil Coolers
Oil coolers prevent excessive heat buildup in lubricating oil, ensuring that it remains effective in reducing friction.

Piston Cooling Nozzles
  • Used primarily in turbocharged engines to reduce piston temperatures.
  • These nozzles spray cool oil under the piston, helping regulate heat and prevent overheating.
  • A separate oil gallery is provided in the engine block to supply oil to these nozzles.
Oil Pressure Gauge & Dipstick
  • The oil pressure gauge monitors the oil circulation and pressure within the engine.
  • The dipstick allows operators to check oil levels manually. It has low and high markings to indicate whether oil needs to be topped up.
Caution for Lubrication System Maintenance
  • Oil levels should always be checked when the engine is cold to ensure accurate readings.
  • Only manufacturer recommended lubricating oil should be used to prevent damage. The SAE number (e.g., 15W-40 CI4) represents the viscosity grade and should be selected according to engine specifications.
  • Regular oil changes and filter replacements are necessary to keep the lubrication system functioning effectively.
Final Thoughts

The starting system and lubrication system are the backbone of a diesel generator’s reliability. A well-maintained battery and starter motor ensure the engine starts efficiently, while a robust lubrication system prevents excessive friction, overheating, and wear of critical moving parts. By regularly monitoring and servicing these systems, operators can enhance performance, minimize breakdowns, and extend the lifespan of their DG set.

In the next part of our Operation and Maintenance of Diesel Generators Series, we will discuss the Fuel System, covering how diesel fuel is delivered and burned efficiently for power generation.

Got any questions or insights? Drop a comment below! If you found this article helpful, share it with others in the industry. Stay tuned for the next part!

Disclaimer
This article is for educational purposes only and has been compiled from various online sources. While every effort has been made to ensure accuracy, readers should refer to manufacturer manuals and industry experts for specific operational and maintenance guidelines. The image in this post is AI generated.

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