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Main engine protection failure. Troubleshooting

Greetings! Today we have a problem with the main engine, all protections have failed, an alarm has appeared on the BMS-2000III panel - “EPS Power Failure”. In this article we will figure out what this alarm is and how to fix this problem.

Main engine protection failure. Troubleshooting

First of all, you need to understand what “EPS Power Failure” means, for this we refer to the instructions. EPS is the Engine Protecting System for the main engine. The power supply for this system has failed.

At the same time, it did not fail immediately, but briefly lost power and this alarm periodically went out. But after a short time it completely lost power.

EPS Power Failure alarm
EPS Power Failure alarm
EPS Power Failure alarm history

EPS Power Failure alarm history
EPS Power Failure alarm history
EPS Power Failure
EPS Power Failure

It can be seen that the EPS unit is de-energized, and there is no 5V DC output voltage on the power supply (the LEDs do not light up and this was checked using a tester).

EPS unit and its power supply (normal state)
EPS unit and its power supply (normal state)
EPS unit and its power supply (de-energized state)
EPS unit and its power supply (de-energized state)
EPS unit and its power supply (de-energized state)
EPS unit and its power supply (de-energized state)
EPS power supply (de-energized)
EPS power supply (de-energized)

From this we can conclude that the EPS unit’s power supply has failed and requires replacement.

It is temporarily necessary to put a watch in the engine room, because according to the instructions, if this system fails, all automatic protections of the main engine stop working (Auto Shut Down, Auto Slow Down and Manual Stop).

Main engine protections (Auto Shut Down, Auto Slow Down and Manual Stop) do not work
Main engine protections (Auto Shut Down, Auto Slow Down and Manual Stop) do not work

This means that, for example, when low oil pressure protection is activated, automatic Slow Down and Shut Down of the main engine will not occur. In this case, a low oil pressure alarm will be issued and if the automatic start of the standby pump does not work, the main engine will not stop and will operate with low lubricating oil pressure, which can lead to irreversible consequences and further damage.

Troubleshooting manualTroubleshooting manual
Troubleshooting manual

Therefore, engineers take over the watch and will make decisions instead of automatically protecting the main engine. In this case, the emergency manual stop of the main engine also does not work (the manual stop buttons do not work), this means that the operator in the above situation will have to use the telegraph handle to stop the main engine, having previously received control from the bridge, or will have to stop the main engine from the bridge (this will occur slowly according to the stop program).

Scheme of operation of the main engine automation modules

Scheme of operation of the main engine automation modules
Scheme of operation of the main engine automation modules

Thus, the main engine was left without an automatic protection system and emergency stop.

To eliminate this failure, it is necessary to replace the power supply of the EPS unit. Because this system is critical equipment, in the event of a failure of which the main engine may stop working, the power supply cannot be repaired and requires replacement.

After replacing the power supply, the protection system is restored and watch maintenance is no longer required.

As a result of disassembling the power supply of the EPS unit, multiple problems were discovered with the semiconductor components of the circuit.

Protection system of the main engine

Protecting the main engine on a merchant vessel is critical for ensuring safe and efficient operation. Various protective measures and systems are implemented to safeguard the engine from damage and ensure its reliable performance. Here are the primary protections for the main engine on a merchant vessel:

1. Alarm and Monitoring Systems

  • Engine Room Alarm System: Alerts the crew to any abnormalities or faults in the engine.
  • Remote Monitoring System: Allows continuous monitoring of engine parameters from the bridge or a centralized control room.

2. Temperature and Pressure Controls

  • Cooling Water Temperature: Monitors and controls the temperature of the cooling water to prevent overheating.
  • Lubricating Oil Pressure: Ensures adequate lubrication pressure to prevent engine wear.
  • Fuel Oil Pressure and Temperature: Maintains the correct pressure and temperature of the fuel oil for efficient combustion.
  • Exhaust Gas Temperature: Monitors the exhaust gas temperature to detect potential issues such as incomplete combustion or overheating.

3. Safety Devices

  • Safety Valves: Relieve excess pressure to prevent explosions or damage.
  • Crankcase Explosion Relief Valves: Prevent the build-up of explosive gases within the crankcase.
  • Scavenge Airbox Safety Valve: Releases excess pressure in the scavenge air system.

4. Shutdown Mechanisms

  • Emergency Shutdown System (ESD): Automatically shuts down the engine in case of severe faults or emergencies.
  • Overspeed Trip: Shuts down the engine if it exceeds its maximum safe operating speed.
  • Low Lubricating Oil Pressure Shutdown: Stops the engine if the lubricating oil pressure drops below a safe level.
  • High Water Temperature Shutdown: Shuts down the engine if the cooling water temperature exceeds safe limits.

5. Fire Detection and Extinguishing Systems

  • Engine Room Fire Detection System: Detects the presence of fire or smoke in the engine room.
  • Fixed Fire Extinguishing System: Uses CO2, foam, or other extinguishing agents to control fires in the engine room.

6. Mechanical Protections

  • Air Start System Protection: Ensures that the air starting system operates correctly and prevents damage during engine start-up.
  • Turbocharger Safety: Monitors the turbocharger performance and provides alarms or shutdown in case of malfunction.
  • Vibration Monitoring: Detects abnormal vibrations which could indicate misalignment or mechanical faults.

7. Fuel and Oil Management

  • Water-in-Fuel Detection: Identifies the presence of water in the fuel, which can cause engine damage.
  • Oil Mist Detector: Detects oil mist in the crankcase to prevent crankcase explosions.

8. Control Systems

  • Governor: Regulates the engine speed and maintains it at the desired level.
  • Automatic Control Systems: Manage various engine parameters automatically to ensure optimal performance.

9. Regular Maintenance and Inspections

  • Scheduled Maintenance: Routine checks and maintenance activities to keep the engine in good condition.
  • Condition Monitoring: Regular inspection and analysis of engine components to predict and prevent failures.

10. Training and Procedures

  • Crew Training: Ensures that the engine room personnel are well-trained to handle emergencies and routine operations.
  • Standard Operating Procedures (SOPs): Detailed procedures for normal and emergency operations of the main engine.

Implementing these protections helps to ensure the safe and efficient operation of the main engine on a merchant vessel, minimizing the risk of accidents and mechanical failures.


Main engine: MITSUI MAN B&W 6S50MC-C.

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