Understanding Engine Hydrostatic Locking: Causes, Prevention, and the Role of Marine Engineers

In the world of marine engineering, hydrostatic locking is a term that sends shivers down the spine of every professional. It’s a potentially catastrophic problem that can lead to severe damage to engines and, in some cases, endanger the entire vessel. In this article, we will delve into the causes of engine hydrostatic locking, how it can be prevented, and the crucial role marine engineers play in ensuring it doesn’t reoccur.

What is engine hydrostatic locking?

Engine hydrostatic locking, also known as hydrolock, occurs when a liquid, usually water, enters the combustion chamber or cylinders of an engine, preventing the engine from turning over. This unwanted intrusion of liquid disrupts the engine’s internal workings, and in the case of a marine engine, it can spell disaster for the entire vessel.

Example of oil present into engine intake manifold. Source and credit: dieselmarineinsights.blogspot.com

For example, hydrolock happens when a volume of liquid greater than the volume of the cylinder at its minimum (end of the piston’s stroke) enters the cylinder. Since liquids are nearly incompressible, the piston cannot complete its travel; either the engine must stop rotating or a mechanical failure must occur.

Causes of Engine Hydrostatic Locking

The most common cause of hydrolocking in marine engines is water ingress through the exhaust system. This can happen if the exhaust outlet is submerged due to waves, trim, or loading conditions. Water can also enter the engine through the air intake, fuel system, or cooling system due to leaks, flooding, or condensation.

Depending on how much water is in the cylinders and how fast the engine is running, hydrolocking can have different effects on the engine. If the engine is stopped or idling, hydrolocking may cause the engine to stall or refuse to start. If the engine is running at high speed, hydrolocking may cause a loud noise and a sudden stop of the engine. The sudden expansion of gases can also cause gaskets to blow or cylinders to crack. The most common damage caused by hydrolocking is bent or broken connecting rods, which connect the pistons to the crankshaft.

Bent connecting rod. Source and credit: dieselmarineinsights.blogspot.com

Bent connecting rod. Source and credit: dieselmarineinsights.blogspot.com

Apart from water, when the engine is off, and there’s an intake leak, other fluids (oil, fuel) can easily enter the cylinders.

Prevention of Engine Hydrostatic Locking

  • Regular Maintenance: The most crucial step in preventing engine hydrolock is regular maintenance. This includes:
    • Checking and changing air filters, inspecting seals and valves for leaks, and ensuring that the engine is in optimal working condition.
    • Check and maintain the exhaust system regularly. Install anti-siphon devices or water traps to prevent water from flowing back into the engine.
    • Check and maintain the air intake system regularly. Make sure that the air filter is clean and dry and that there are no obstructions or leaks in the ducts or hoses. Avoid operating the engine in areas with high humidity or spray.
    • Check and maintain the fuel system regularly. Make sure that the fuel tank is vented properly and that there are no leaks or contamination in the lines or injectors. Use fuel additives to prevent water from accumulating in the fuel.
    • Check and maintain the cooling system regularly. Make sure that the coolant level is adequate and that there are no leaks or corrosion in the radiator, hoses, or pump. Use antifreeze to prevent freezing and boiling of the coolant.
  • Proper Ventilation: Adequate ventilation in the engine room can help reduce condensation and the risk of hydrolock. Proper ventilation systems can also help keep the engine room dry.
  • Water-Tight Integrity: Ensuring that the vessel is properly sealed and that water cannot enter the engine room in the event of flooding is essential. Make sure that the exhaust outlet is above the waterline and that there are no leaks or cracks in the pipes or valves. Regular inspections for potential breaches are crucial. Avoid operating the engine in extreme weather conditions or rough seas. Reduce speed and load when encountering waves or wakes. Monitor the engine temperature and pressure gauges and listen for any unusual sounds or vibrations.
  • Proper Shutdown Procedures: When shutting down the engine, it’s important to follow the manufacturer’s recommended procedures. This may include turning off the fuel supply before stopping the engine, preventing the intake of water during the cooling down process.

The Role of Marine Engineers

Marine engineers are responsible for designing, installing, operating, and maintaining marine engines and related systems. They play a vital role in preventing hydrostatic locking by ensuring that the engines are suitable for marine applications and that they meet safety and performance standards. Their responsibilities include:

  • Regular Inspections: Marine engineers should conduct regular inspections to identify and address potential issues that may lead to hydrolock. This includes inspecting intake systems, seals, and valves.
  • Maintenance: They are responsible for the routine maintenance of the engine, ensuring that air filters are changed, seals are in good condition, and the engine is functioning optimally.
  • Emergency Response: In the event of flooding or water intrusion, marine engineers must act swiftly to prevent or mitigate hydrolock. This may involve sealing off the affected area, pumping out water, and assessing and repairing any damage. They use their knowledge and skills to troubleshoot and resolve any issues related to hydrostatic locking or other engine malfunctions.

    Broken liner. Source and credit: dieselmarineinsights.blogspot.com

  • Training: Owners must ensure that the vessel’s engineering crew is trained to follow proper shutdown procedures and respond effectively in emergency situations. Marine engineers also educate and train other crew members on how to operate and maintain marine engines properly. They provide guidance and instructions on how to prevent hydrostatic locking and what to do in case it happens. They also follow emergency procedures and protocols to minimize damage and ensure safety in case of hydrostatic locking or other engine failures.

In conclusion, engine hydrostatic locking is a serious concern in the world of marine engineering. By understanding its causes and taking proactive steps to prevent it, marine engineers can safeguard the vessel and its crew. Their vigilance in regular maintenance, proper shutdown procedures, and rapid response to emergencies can make all the difference in ensuring the smooth operation of marine engines and the safety of everyone on board.

You can read a very interesting case study related to engine failure due hydrolocking if you follow THIS LINK.

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Demystifying Marine Engine Crankshaft Deflection Measurements: A Comprehensive Guide

Marine engines are the heart of any seafaring vessel, powering them through the vast expanse of the ocean. Ensuring their optimal performance is crucial for the safety and efficiency of maritime operations. One vital aspect of marine engine maintenance is monitoring and interpreting crankshaft deflection measurements.

What is crankshaft deflection?

Crankshaft deflection refers to the measurement of the deviation or displacement in the centerline of the engine’s crankshaft from its ideal position during operation. It is a critical parameter that reflects the mechanical health and alignment of the engine components, particularly in large marine engines. Excessive crankshaft deflection can lead to fatigue, fracture, wear, and damage of the crankshaft and other engine components. Accurate interpretation of crankshaft deflection measurements helps prevent catastrophic failures and costly repairs, ultimately ensuring vessel safety.

If you want to learn more about crankshaft deflection please follow THIS LINK.

How to Measure Crankshaft Deflection

If you follow the above mentioned link, you will find an explanation with regard to deflection measurement.

Importance of Crankshaft Deflection Measurements

  • Early Problem Detection: Monitoring crankshaft deflection allows for early detection of mechanical issues or misalignments in the engine, preventing them from escalating into major problems that could lead to engine failure.

  • Safety Assurance: A properly aligned crankshaft is essential for the safety of the vessel and its crew. Correct alignment reduces the risk of catastrophic engine failures that could result in accidents at sea.

  • Enhanced Engine Efficiency: Correcting misalignments revealed by deflection measurements can significantly improve engine efficiency, reducing fuel consumption and environmental impact.

  • Cost Savings: Identifying and rectifying issues early on can save substantial repair and replacement costs in the long run, making crankshaft deflection measurements a cost-effective maintenance practice.

How to Interpret Marine Engine Crankshaft Deflection Measurements

Crankshaft deflection measurements are usually expressed as a table or a graph showing the values of deflection at different angular positions of the crankshaft for each unit.

Source and Credit: marineengineersknowledge.com

The values are compared with the manufacturer’s specifications and limits to assess the condition of the crankshaft.

Interpreting crankshaft deflection measurements requires a combination of technical knowledge and practical experience. Follow these steps to ensure accurate interpretation:

  • Understand the Measurement Units: Crankshaft deflection measurements are typically expressed in micrometers (µm) or millimeters (mm). Familiarize yourself with these units and their conversion to ensure precision in your interpretations. Moreover, the dial indicator should be calibrated and checked regularly for any errors or defects. A faulty dial indicator can give false readings and lead to incorrect interpretation of deflection measurements.

For example, in the table below, U1 means unit 1, T means top position, B means bottom position, F means fuel pump side position, and E means exhaust side position. The values are in mm.

Unit T B F E
U1 0 0 0 0
U2 -0.02 +0.02 -0.01 +0.01
U3 -0.04 +0.04 -0.02 +0.02
U4 -0.06 +0.06 -0.03 +0.03
U5 -0.08 +0.08 -0.04 +0.04
U6 -0.10 +0.10 -0.05 +0.05

Plot the deflection values on a graph for each unit, using a different color or symbol for each angular position. 

Source and Credit: Marineinbox

  • Establish Baseline Measurements: Before interpreting any measurements, it’s essential to establish baseline readings for the engine when it’s in perfect condition. These baseline measurements act as a reference for identifying deviations and can be found in the engine Technical File, under Shop Trial Measurements.

  • Examine Measurement Patterns: Crankshaft deflection measurements are usually taken at multiple points along the crankshaft’s length. Analyze these measurements to identify any recurring patterns or trends. Irregularities may indicate misalignments or mechanical issues.

    • Uniformity: This is when all units show similar values of deflection within acceptable limits. This indicates that the crankshaft is in good condition and aligned properly.
    • Sagging: This is when one or more units show higher values of deflection at either top or bottom positions, indicating that the crankshaft is bending downwards due to gravity or load.
    • Hogging: This is when one or more units show higher values of deflection at either top or bottom positions, indicating that the crankshaft is bending upwards due to gravity or load.
    • Twisting: This is when one or more units show higher values of deflection at either fuel pump side or exhaust side positions, indicating that the crankshaft is twisting along its axis due to torsional forces.
    • Ovality: This is when one or more units show higher values of deflection at all positions, indicating that the crankpin or journal has become oval-shaped due to excessive wear or damage.
  • Consider Operational Conditions: It’s vital to take into account the engine’s operational conditions during measurements. Factors like load, temperature, and RPM can influence deflection readings. Comparing measurements under different conditions can provide valuable insights.

For example, the crankshaft expands and contracts with changes in temperature, which can affect the deflection values. Therefore, it is recommended to measure the deflection at a consistent temperature, preferably when the engine is cold or after a short warm-up period.

Moreover, the draught of the vessel can cause bending or twisting of the hull, which can affect the alignment of the engine and the crankshaft. Therefore, it is recommended to measure the deflection at a consistent draught, preferably when the vessel is fully loaded or unloaded.

  • Consult Manufacturer Guidelines: Manufacturers of marine engines often provide guidelines for interpreting crankshaft deflection measurements specific to their engine models. These guidelines should be consulted and followed diligently.

    • If they are within tolerance, then no action is required.
    • If they are out of tolerance, then corrective action is needed.

For example, in the table below, the manufacturer’s specifications and limits are given as:

    • Maximum permissible difference between top and bottom positions: 0.12 mm.
    • Maximum permissible difference between fuel pump side and exhaust side positions: 0.08 mm.
    • Maximum permissible difference between adjacent units: 0.04 mm.
Unit T-B Difference (mm) F-E Difference (mm) Adjacent Unit Difference (mm)
U1 0 0 N/A
U2 0.04 0.02 0.02
U3 0.08 0.04 0.02
U4 0.12 0.06 0.02
U5 0.16 0.08 0.02
U6 0.20 0.10 0.02

In this example, units U1, U2, and U3 are within tolerance, while units U4, U5, and U6 are out of tolerance. Therefore, corrective action is needed for units U4, U5, and U6.

  • Seek Expert Advice: If you’re unsure about the interpretation of deflection measurements or suspect a significant issue, it’s advisable to consult with experienced marine engineers or specialists. Their expertise can help pinpoint problems accurately.

  • Regularly Monitor and Document: Maintain a comprehensive record of all deflection measurements and their interpretations. Regular monitoring allows you to track the engine’s health over time and detect any changes or deterioration.

    Identify the possible causes and solutions for the crankshaft deflection problems, based on the shape and pattern of the graph and the manufacturer’s recommendations.

    • If the graph shows sagging or hogging, it could be caused by uneven wear of main bearings, misalignment of engine foundation, or distortion of hull structure. The possible solutions are adjusting or replacing main bearings, aligning engine foundation, or correcting hull deformation.
    • If the graph shows twisting, it could be caused by uneven firing pressures, faulty fuel injection system, or misalignment of driven unit. The possible solutions are repairing fuel injection system, adjusting firing pressures, or aligning driven unit.
    • If the graph shows ovality, it could be caused by improper lubrication, journal bearing failure, overspeeding or overloading of engine, excessive crankshaft deflection and misalignment of parts. The possible solutions are replacing crankpin or journal, improving lubrication system, reducing engine speed or load, or correcting crankshaft deflection and alignment.

In conclusion, interpreting marine engine crankshaft deflection measurements is a critical aspect of engine maintenance, ensuring vessel safety, efficiency, and cost-effectiveness. By understanding the importance of these measurements and following the steps outlined in this guide, marine engineers and ship operators can effectively monitor and maintain their engines, ensuring smooth and trouble-free voyages on the high seas.

Incorrect Phase Sequence in Marine Diesel Generators: Causes, Precautions, and Troubleshooting

Diesel generators are one of the most important machineries onboard vessel, as they are designed to provide all the necessary electrical power for all the other machineries onboard vessel. Having and keeping them in good working order is of the utmost importance and every engineer working onboard vessel must be able to operate, maintain and troubleshoot these engines.

We have discussed along this blog, about different topics with regard to diesel generators and will try to cover all the aspects regarding their proper operation, maintenance and troubleshooting in the next future posts.

Proper synchronization and phase sequence are essential for the reliable and efficient operation of marine diesel generators. If you want to read more about generator’s synchronization please follow THIS LINK.

Example of generator’s synchronizing equipment

An incorrect phase sequence can lead to severe electrical problems, potential equipment damage, and operational hazards. In this article, we will delve into the causes of an incorrect phase sequence, discuss measures and precautions to prevent it, and outline troubleshooting steps to rectify the issue.

Causes of Incorrect Phase Sequence in Marine Diesel Generators

    • Engine Rotation Direction: Marine diesel engines can be designed to rotate either clockwise (CW) or counterclockwise (CCW). If the engine’s rotation direction does not match the electrical system’s requirements, it can result in an incorrect phase sequence.
    • Reversed Engine Connections: Incorrect wiring connections within the engine system, such as misaligned or faulty wiring, can lead to an incorrect phase sequence. These errors can occur during installation, maintenance, or repair work.
    • Faulty Engine Control System: Malfunctions or incorrect configurations of the engine’s control system, including the governor and speed control mechanisms, can disrupt the phase sequence and synchronization process.

      Here’s how malfunctions or incorrect configurations of the control system can cause phase sequence and synchronization issues:

      • Speed Control Instability: The governor in an engine regulates its speed to maintain a constant and stable rotational speed. If the governor malfunctions or is incorrectly set, the engine’s speed may fluctuate or become unstable. This can lead to variations in the frequency of the generated electrical output, causing a mismatch in phase sequence when synchronizing with the grid.
      • Phase Shift due to Speed Variation: The phase sequence of a synchronous generator is determined by the mechanical angle between the rotor and the stator windings. If the engine’s speed control system causes variations in rotational speed, it can induce a phase shift between the rotor and the stator, leading to incorrect phase sequence during synchronization.
      • Improper Excitation Control: Synchronous generators require excitation to produce a magnetic field that allows them to synchronize with the grid. If the excitation control system is faulty or improperly configured, the generator may not reach the required level of magnetic field strength, leading to synchronization issues and incorrect phase sequence.
      • Electrical and Mechanical Load Imbalance: The governor and speed control mechanisms play a crucial role in adjusting the engine’s output power to match the electrical load demand. If there is an imbalance between the mechanical load on the engine and the electrical load on the generator, it can affect the engine’s speed and result in a mismatch of the phase sequence during synchronization.
      • Control System Response Time: The response time of the engine’s control system is critical during load changes and transient conditions. If the control system response is slow or inaccurate, it may not be able to maintain the correct phase sequence during sudden load fluctuations. To read more about governor’s adjustment please follow THIS LINK.
      • Control System Interference: In some cases, malfunctions or incorrect configurations of the control system can create electromagnetic interference, affecting the performance of sensors and feedback mechanisms used for synchronization.
    • Engine Modification or Retrofitting: Modifications or retrofitting of the engine system without considering the phase sequence requirements can introduce changes leading to an incorrect phase sequence. For example:
      • During the modification process, if the wiring connections are not done accurately or if there are mistakes in connecting the phases, it can result in an incorrect phase sequence. For instance, if phases A and C are accidentally swapped, the phase sequence would be incorrect.
      • Certain engine components, such as three-phase motors or alternators, have specific phase connections that need to be adhered to for proper operation. If these components are installed or retrofitted incorrectly, the phase sequence can be disrupted.
      • Engines and generators may have terminals for connecting external electrical devices. If these devices are connected to the wrong terminals, it can affect the phase sequence.
      • When retrofitting an engine system, it is crucial to ensure that all the components and equipment are compatible and designed to work together. If there is a mismatch between the components, it could cause a phase sequence issue.
    • Manufacturing Defects: Although rare, manufacturing defects in the engine or associated components can result in an incorrect phase sequence. These defects can manifest as wiring errors, misaligned connections, or faulty internal components.

Precautions and Measures to Prevent Incorrect Phase Sequence

    • Proper Installation: Ensure that the engine is installed correctly, aligning it with the generator and electrical system requirements. Follow the engine manufacturer’s guidelines for wiring connections and rotation direction.
    • Thorough Inspection: Conduct regular inspections and maintenance of the engine system, including the control system, wiring connections, and associated components. Identify and rectify any issues or wiring errors promptly.
    • Verification and Testing: Prior to commissioning or during any modifications, verify the phase sequence of the engine using phase sequence meters or phase rotation indicators. Confirm that it matches the electrical system’s requirements.
    • Documentation and Labeling: Clearly label and document the correct phase sequence during installation or any modifications. This helps prevent confusion and ensures future maintenance and troubleshooting procedures are accurate.
    • Engine Crew Training: Train engine crew in proper synchronization procedures and emphasize the importance of phase sequence verification. Ensure they are aware of the risks associated with incorrect phase sequence and the steps to prevent it.

Troubleshooting Incorrect Phase Sequence

    • Identification: If an incorrect phase sequence is suspected, verify the phase sequence using phase sequence meters or phase rotation indicators. Compare the observed sequence with the required sequence.
    • Wiring Inspection: Conduct a thorough inspection of the engine’s wiring connections, looking for any misalignments, loose connections, or faulty wiring. Rectify any identified issues according to the manufacturer’s guidelines.
    • Control System Examination: Inspect the engine’s control system, including the governor and speed control mechanisms, for malfunctions or misconfigurations. Rectify any identified issues or consult a qualified technician for assistance.
    • Engine Rotation Direction: Ensure that the engine’s rotation direction matches the electrical system’s requirements. If necessary, consult the engine manufacturer or a professional technician to rectify any rotation direction discrepancies.
    • Synchronization Retry: After rectifying the identified issues, retry the synchronization process while closely monitoring the phase sequence. Confirm that the correct phase sequence has been restored.

In conclusion, maintaining the correct phase sequence is crucial for the safe and reliable operation of marine diesel generators. By understanding the causes of incorrect phase sequence, implementing precautionary measures during installation and maintenance, and conducting proper troubleshooting procedures, operators can minimize the risks associated with an incorrect phase sequence. Adhering to these best practices ensures the efficient functioning of marine diesel generators while safeguarding the vessel’s electrical system and equipment.

If you have any questions regarding above, please feel free to use our existing forum Seafarer’s World, Telegram Chief Engineer’s Log Chat or Instagram and will try to answer to all your queries. You can use the feedback button as well!

If you like my posts, please don’t forget to press Like and Share. You can also Subscribe to this blog and you will be informed every time when a new article is published.

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Reverse Power on Vessel’s Diesel Generators: Measures, Precautions, and Troubleshooting

In the marine environment, it is essential to have a reliable source of power. Diesel generators are mainly used to provide power to ships and other marine vessels. During a vessel voyage, depending on power requirement (during maneuverings, canal transit, shallow waters, using bow/stern thrusters etc.) the engine crew need to run more than one generator. To run two or more generators in parallel, they need to be safely synchronized. To read and learn more about generator synchronizing, please follow THIS LINK.

Example of generator’s synchronizing panel

However, if not properly synchronized, these generators can create a dangerous condition known as reverse power. Reverse power on vessel diesel generators can pose significant risks to the overall electrical system and equipment onboard. Synchronization is crucial to ensure the smooth operation of generators, and taking appropriate measures and precautions can prevent reverse power situations. Further below, we will explore the concept of reverse power, discuss preventive measures, and outline the troubleshooting process to mitigate this issue effectively.

What is Reverse Power? 

Reverse power is a condition that occurs when a generator is operating at a higher frequency than the electrical system it is connected to. Reverse power occurs when the power flows from the bus bar or electrical network back into the generator. This situation arises during synchronization when the generator’s rotational speed, voltage, or phase sequence does not match the electrical network. Reverse power can cause damage to the generator, increase fuel consumption, and disrupt the operation of other connected generators.

Preventive Measures and Precautions

To avoid reverse power during synchronization, it is vital to implement the following measures and precautions:

    • Generator Preparation: Ensure that the generator is in good condition and properly maintained. Regular inspections and maintenance routines help identify potential issues beforehand.

    • Voltage and Frequency Matching: Prior to synchronization, verify that the generator’s voltage and frequency match the electrical network’s requirements. Use precision instruments to measure and adjust the generator’s parameters accordingly.

      Example of frequency matching

    • Phase Sequence Alignment: Confirm that the generator’s phase sequence matches that of the electrical network. Phase sequence meters or phase rotation indicators can be utilized for this purpose.

    • Protective Relays and Circuit Breakers: Install appropriate protective relays and circuit breakers to detect reverse power situations. These devices will trip and isolate the generator from the network if reverse power occurs.

Example of a reverse power protective relay

    • Synchronization Panel: Employ a synchronization panel equipped with synchroscopes, meters, and alarms. This panel provides visual and audible indications of synchronization status and alerts operators to potential reverse power conditions.

    • Engineer Training: Ensure that the engineers are well-trained in synchronization procedures and the potential risks associated with reverse power. Regular training sessions and refresher courses help enhance their understanding and vigilance.

Troubleshooting Reverse Power

In the event of reverse power occurring despite preventive measures, the following troubleshooting steps can be undertaken:

    • Immediate Isolation: When reverse power is detected, engineer should immediately disconnect the generator from the network by tripping the circuit breaker or activating protective relays

    • Fault Analysis: Examine the generator’s settings, synchronization panel readings, and any recorded alarms or indicators. Identify any potential causes such as incorrect phase sequence, voltage mismatch, or frequency deviation.

    • Corrective Actions: Depending on the fault analysis, take appropriate corrective actions. This may involve adjusting the generator’s voltage, frequency, or phase sequence to match the network requirements. Additionally, inspect and rectify any faulty relays, circuit breakers, or synchronization panel components.

    • Synchronization Retry: Once the corrective actions are completed, retry the synchronization process while closely monitoring the generator’s behavior and synchronization panel readings. Confirm that the reverse power condition has been resolved.

    • Post-Troubleshooting Inspection: Conduct a thorough inspection of the generator and associated equipment to ensure there are no hidden issues that could lead to future reverse power occurrences.

In conclusion, reverse power on vessel diesel generators can result in severe consequences, impacting both equipment and operational safety. By implementing preventive measures and precautions, vessel operators can significantly reduce the likelihood of reverse power incidents during synchronization. In cases where reverse power does occur, a systematic troubleshooting approach helps identify the root cause and rectify the issue promptly. Adhering to these best practices ensures reliable and efficient generator operation while safeguarding the vessel’s electrical system.

If you want to learn and get an “Introduction to Four Stroke and Auxiliary Engines”, please follow THIS LINK on Alison platform. The course is free and all you need to do is just to subscribe to their platform using the link above. This will be of a great help to me as well, as I will earn small commission. You can consider this as a reward for my effort to provide guidance and advices with regard to complex, challenging and rewarding marine engineering. 

If you wish to learn about “Power Protection Schemes”, please follow THIS LINK.

If you have any questions regarding above, please feel free to use our existing forum Seafarer’s World, Telegram Chief Engineer’s Log Chat or Instagram and will try to answer to all your queries. You can use the feedback button as well!

If you like my posts, please don’t forget to press Like and Share. You can also Subscribe to this blog and you will be informed every time when a new article is published.

Also you can buy me a coffee by donating to this website, so I will have the fuel I need to keep producing great content! Thank you!

Marine Fuel Injector Valves – Ensuring Optimal Performance

Marine fuel injectors are critical components of an engine’s fuel delivery system, responsible for precisely atomizing fuel and delivering it to the combustion chamber. Over time, these injectors can become clogged, worn, or develop leaks, resulting in decreased engine performance, reduced fuel efficiency, and potential engine damage. In this blog article, we will explore the importance of overhauling and maintaining marine fuel injectors to ensure their optimal performance and prolong the life of your marine engines.

Before diving into the overhaul and maintenance process, it’s crucial to be aware of common signs indicating potential fuel injector problems. These signs include: reduced engine power and acceleration, rough idling or stalling, increased fuel consumption, misfires or engine hesitation, smoke emissions from the exhaust, difficulty starting the engine etc. If you want to learn more about “How to check fuel injector valve condition”, please follow THIS LINK.

Marine engines are subject to strict emissions regulations aimed at minimizing their environmental impact. Maintaining the peak performance and efficiency of marine engines is crucial for a smooth sailing experience. Among the various components that play a pivotal role in engine function, fuel injectors stand out as critical elements. These small but mighty devices atomize fuel and deliver it to the engine’s combustion chamber, directly impacting its power, fuel economy, and emissions.

Fuel injectors must deliver fuel in a precise spray pattern and at the right pressure for efficient combustion. Over time, fuel injectors can develop leaks or clogs that disrupt this delicate balance, leading to suboptimal combustion. By conducting regular leak and pressure tests, marine engineers can identify and rectify any issues promptly. Maintaining the integrity of fuel injectors ensures that the engine receives the right amount of fuel, enhancing combustion efficiency, power output, and reducing fuel consumption.

Leaking fuel injectors can result in serious consequences for marine engines. When fuel leaks occur, excess fuel can infiltrate the engine’s oil system, diluting the lubricating properties of the oil and causing accelerated wear and tear on internal components. In extreme cases, uncontrolled fuel leaks can even lead to engine fires, posing a significant risk to the vessel and its crew. By performing regular leak tests, potential issues can be detected early, preventing costly engine damage and ensuring safe operation on the water.

When fuel injectors leak or malfunction, the combustion process is compromised, leading to incomplete fuel burn and increased emissions of pollutants such as hydrocarbons and nitrogen oxides. Regular leak and pressure tests help maintain optimal injector performance, ensuring cleaner combustion, and reducing the vessel’s environmental footprint.

Fuel injectors that are functioning optimally contribute to overall engine performance and reliability. A leak or malfunctioning injector can result in reduced engine power, rough idling, decreased throttle response, and even engine misfires. Through leak and pressure testing, any injector-related issues can be promptly identified and resolved, allowing the engine to operate at its full potential. A well-maintained fuel injection system ensures smooth operation, enhances engine reliability, and minimizes the risk of unexpected breakdowns.

Overhauling fuel injectors involves a thorough cleaning and restoration process to remove deposits, restore proper fuel flow, and optimize performance.

Here’s a step-by-step guide to overhauling marine fuel injectors:

    • Carefully remove the fuel injectors from the engine, following the manufacturer’s instructions.
    • Examine the injectors for any signs of damage, such as cracked or broken components. Check the injector tips for carbon buildup or clogging, which can impede fuel flow.
    • Utilize a specialized injector cleaning kit or professional cleaning service to remove deposits, varnish, and carbon buildup. Follow the specific instructions provided with the cleaning kit or consult manufacturer or a professional technician.
    • Replace worn or damaged injector components, such as O-rings, seals, and nozzles, to ensure a proper seal and prevent leaks. Use high-quality replacement parts recommended by the manufacturer.
    • After cleaning, perform a comprehensive fuel injector test to evaluate their performance. This test may include flow rate measurement, spray pattern examination, and leak detection. Replace any injectors that fail the test or show significant performance deviations.

    • Carefully reinstall the fuel injectors, ensuring proper alignment and connection. Follow torque specifications provided by the manufacturer to avoid overtightening or undertightening.

Regular maintenance and testing of marine fuel injectors are essential to ensure optimal engine performance and prevent potential issues. One crucial test that should be performed is the fuel injector leak test.

In the next paragraph, I will provide you with a step-by-step guide on how to perform a marine fuel injector leak test, enabling you to identify and address any leaks promptly and maintain the reliability and efficiency of your marine engine.

    1. To perform a fuel injector leak test, you will need the following items:
      • Fuel injector tester or kit
      • Appropriate safety equipment (gloves, eye protection)
      • Fuel pressure gauge
      • Fuel system cleaning solution (optional)
      • Manufacturer’s service manual (for specific instructions and specifications)
    1. Before beginning the test, it is crucial to ensure the safety of the testing environment. Follow these steps:

      • Make sure the engine is turned off and has had enough time to cool down.
      • Locate the fuel injectors on your marine engine. They are usually mounted on the cylinder head.

      • Review the manufacturer’s service manual for any specific instructions or precautions related to your engine model.

    2. To prevent fuel flow during the test, you need to disconnect the fuel supply. Follow these steps:

      • Locate the fuel supply line connected to the fuel rail or fuel distributor.
      • Carefully disconnect the fuel line using the appropriate tools, ensuring that any residual pressure is relieved safely.

      • Use a suitable plug or cap to seal the open end of the fuel line to prevent any fuel leakage.

    3. The fuel injector tester allows you to apply pressure and detect potential leaks. Follow these steps:

      • Connect the fuel injector to the fuel injector test bench according to the manufacturer’s instructions.

      • Ensure a secure and proper connection between the tester and the fuel injectors.

      • Make sure all connections are tight and leak-free to maintain accurate testing results.
    4. Now it’s time to apply pressure to the fuel injectors and observe for any leaks. Proceed as follows:
      • Refer to the manufacturer’s instructions to determine the recommended pressure for your specific engine model.
      • Connect a fuel pressure gauge to the fuel system to monitor the pressure during the test.

      • Gradually increase the pressure to the specified level while monitoring the gauge for any sudden drops or fluctuations, indicating potential leaks.


    5. During the pressure test, carefully inspect each fuel injector for signs of leaks. Perform the following:

      • Visually inspect around each fuel injector for any fuel drips, seepage, or signs of wetness.

      • Use a flashlight if necessary to better observe the injector area and connections.

      • Pay attention to the injector O-rings, connectors, and fuel lines for any signs of deterioration or damage.

If you identify any leaks during the test, it is crucial to address them promptly. Replace any faulty O-rings or damaged injector components. Clean the fuel injectors using a suitable fuel system cleaning solution, following the manufacturer’s instructions. Re-test the fuel injectors after repairs or cleaning to ensure the leaks have been resolved.

Performing a fuel injector leak test is a crucial aspect of maintaining the performance and reliability of marine engines. By following this step-by-step guide, you can identify potential leaks early on, address them promptly, and ensure the optimal operation of your marine fuel injectors.

To maintain the optimal performance of marine fuel injectors between overhauls, consider implementing simple routine maintenance practices, like:

    • proper purifier operation and maintenance, to ensure clean and high-quality fuel, minimizing the risk of injector clogging and deposits.
    • periodically use fuel additives designed to clean and lubricate the fuel system. These additives can help remove deposits and improve injector performance.
    • conduct visual inspections of the fuel injectors during routine maintenance checks. Look for signs of leaks, damaged components, or buildup that may require immediate attention.

In conclusion, marine fuel injectors play a vital role in the performance, efficiency, and longevity of marine engines. Overhauling and maintaining these injectors ensure proper fuel delivery, optimal combustion, and reliable engine operation. By following the steps outlined in this blog post and implementing routine maintenance practices, you can maximize the performance and lifespan of your marine fuel injectors. Remember, a well-maintained fuel injector system translates into a smoother, more efficient, and trouble-free vessel operation experience.

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If you have any questions regarding above, please feel free to use our existing forum Seafarer’s World, Telegram Chief Engineer’s Log Chat or Instagram and will try to answer to all your queries. You can use the feedback button as well!

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How to check fuel injector valve condition

A fuel injector valve is a device which receives pressurized fuel as a liquid and sprays it into engine cylinder as a fine mist. It consists of a nozzle and nozzle holder and a  body. The nozzle has a series of small orifices around its tip used for atomizing the injected fuel. So, the purpose of injection valves is to precisely inject the fuel quantity calculated by the control unit in all engine operating states. To ensure the fuel is atomized effectively while minimizing condensation losses, a certain engine-specific distance and injection angle need to be observed.

Example of fuel injector valves

Fuel injector valves, like any other machinery or devices that are under continuous load and stress, tend to malfunction and ultimately to fail while in service if maintenance plan is not properly followed.

Accelerated wear/damage to nozzle tips are in most cases caused by poor fuel oil
quality, fuel contamination and this will cause poor combustion which in turn will result in poor engine performance and eventually may result in major damage to the engine.

Based on experience accumulated over years, has been observed the following issues regarding fuel injection valves:

      • Premature inspection of fuel valves, before scheduled inspection according to the Planned Maintenance Program causing maintenance induced failures and extra costs;
      • Short lifetime of fuel nozzles;
      • Broken fuel nozzle springs as a result of excessive pre-tensioning by repeatedly readjusting the opening pressure to new value causing dynamic overloading of the spring;
      • Repair/Re-condition of fuel injection valves (which is not recommended by engine makers as through recondition of fuel valve nozzles the engine SFOC dramatically increases due unsuitable fuel atomization);
      • Incorrect cleaning of nozzle tips causing damage to the injection nozzle.

As per MAN Diesel & Turbo the fuel injection valve should be operated for 8000 hrs. without removal and as per Wartsila for 6000 hrs. , unless a specific reason dictates so. To ensure safe operation, the heavy fuel oil operating instructions and treatment, including correct filtration must be strictly observed.

In case of MAN engines equipped with the latest requirement of filters, common 10μm abs. automatic back flush filter for the auxiliary engines and a 25μm abs. fuel safety filter fitted to each generator, a maintenance interval of at least 8000 hours for fuel valves can be normally expected.

Opening pressure must be adjusted according to the manufacturer’s guide lines, in order to prevent breakage of the spring.

In the above image there is no need to remove any fuel injection valves for pressure testing, adjustments or overhaul. Fuel valves should remain in engine unless other indications dictate so.

However, at the below stated indications, inspection of the fuel valves are mandatory.

      • Deviation of more than 40°C of exhaust gas outlet temperature measured at cylinder head among cylinders.
    • In the above image low exhaust gas temperature at cylinder no. 4. If the temperature decrease is related to the fuel injection valve the cause is most likely sticking needle in fuel nozzle. In this case, fuel injection valve should be removed for checking.
    • In the above image High exhaust gas temperature at cylinder no. 4. If the temperature increase is related to the fuel injection valve the cause is most likely leaking or worn fuel nozzle. In this case fuel injection valve should be removed for checking.
      • Exhaust gas temperature inlet turbocharger has increased to 10°C below alarm limit.
      • Black smoke is observed during normal static load.

Therefore performance check is strongly recommended at least once a week.

The fuel injection valve should be cleaned from the outside without dismantling the fuel valve, check should be done in fully assembled condition. Correct cleaning procedure of the nozzle is necessary to ensure proper atomisation of the fuel in the combustion chamber.

Steel brush including rotating steel brush will destroy the nozzle spray holes and a new nozzle element is required.Consequence by using rotating steel brushes

Example of a nozzle tip cleaned by a rotating steel brush causing edges in the nozzle bores which destroy the atomisation. Complete and clean combustion is a function of fuel atomisation.

Nozzle condition before cleaning & after cleaning with a nylon sponge.

For judgment of the fuel nozzle condition, only opening pressure and leakage should be used as criteria for acceptance or rejection. Spray pattern test should not be used as a criteria, as the test bench injection capacity is too small to produce the same condition as exits is in the engine.

Drop in opening pressure is typically caused by wear in the needle seat in the fuel injection valve or setting of the spring.
Setting of the spring cannot be avoided, however wear in the seat area is the result of wear from abrasive particles and can be reduced by proper treatment of the fuel.

In case of leakage or low opening pressure, the valve should be opened for internal check of parts. If leakage is the reason for opening the fuel valve, typically the nozzle will have to be replaced as a minimum, while a low opening pressure normally dictates a replacement of the spring. In both situations replacement of other parts may be required based on condition.

On some injector valves there is a requirement to replace the thrust piece as it tends to wear down after certain operating hours.

Fuel valve sectional view

Measuring gap on thrust piece








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Source and Bibliography:

  • MAN Diesel video training
  • MAN Diesel & Turbo Service letter SL2016-628

What you need to know about 4-stroke engine turbocharger wet and dry cleaning

Operational experience has shown that 4 stroke engines operating heavy fuels being bunkered from various ports globally and low load operation of the engine tend to cause fouling of the turbocharger.

The condition and cleanness of the turbine of an exhaust -gas turbocharger have a decisive influence on the efficiency, the performance of the combustion process and hence on the service data of the engine which will be negatively affected.

Possible consequences can be, but not limited to:

      • overspeed of the turbine
      • vibration excitation of the turbine caused by deposits
      • reduced engine efficiency
      • increased fuel consumption

Fouling of the turbine side of the turbocharger will, in its first phase, manifest itself in increasing turbocharger revolutions on account of increased gas velocity through the narrowed nozzle ring area. In the long run, the charging air quantity will decrease on account of the greater flow resistance through the nozzle ring, resulting in higher wall temperatures in the combustion chambers.

Example of turbocharger nozzle ring fouling

A high contamination level with deposits will cause an offset to the normal gas flow resulting in increase in temperature level before the turbine or in extreme case cause surging. This can lead to significant increase in unfavorable excitation orders of vibration which could advance a severe damage of the turbocharger by causing fatigue on the turbine rotor vanes.

Service experience has shown that the turbine side is exposed to increased  fouling when operating on HFO.

The rate of fouling and thereby the influence on the operation of the engine is greatest for small turbochargers where the flow openings between the guide vanes of the nozzle ring are relatively small. Deposits occur especially on the guide vanes of the nozzle ring and on the rotor blades.

In accordance with the operating conditions of the engine, it is sometimes necessary to free both nozzle ring and the blading of the turbine from deposits and other adhesive particles from the combustion process.
This mechanical cleaning is normally carried out in the course of the specified maintenance intervals (general turbocharger overhaul). The turbine rotor and nozzle ring of the turbocharger have to be dismantled for the cleaning process.

Example of turbocharger impeller opened for overhaul

Turbine side of the turbocharger can be cleaned effectively by combination of wet water washing and dry nut shell cleaning, hence it is recommended to carry out wet as well as dry cleaning of turbochargers.

Wet cleaning of the turbines during low-load engine operation has been used for a long time in order to achieve the specified time intervals between the turbocharger inspections and to protract the time-consuming manual cleaning of turbine and nozzle ring.
Wet cleaning is normally carried out about every 250 hours, but it can be executed in shorter or longer intervals depending on the operating conditions. Regular performance observations will show the trend in charge air pressure and exhaust gas temperatures, and define the cleaning intervals for the turbine.
To carry out the wet cleaning process, the engine load has to be significantly reduced and the exhaust gas temperatures have to be put into steady-state condition. The preparation and execution of the wet cleaning process easily adds up to approx. 1 hour during which the full engine load is not available.

The wet cleaning tool would be connected to the same connection as dry cleaning, through a snap coupling.

Example of TC washing connection arrangement

As all injected water is not evaporated, turbochargers need to be fitted with a drain from the exhaust gas outlet. The necessary water flow is dependent on exhaust gas flow and temperature and must be so high that all water does not evaporate, also the water flow must not be so high that the turbine wheel is drowned and stops rotating. The washing sequence should be in accordance with turbocharger manual and the engine load, exhaust gas temperature before turbine and the turbine speed must be as per same manual.

Example of T/C wet and dry cleaning tools

The wet washing kit comes with different nozzle orifice which should be choose as per engine size. If you want and are interested for more in depth information regarding nozzle selection and water flow adjustment  you need to subscribe to Seafarer’s World Forum (powered by chiefengineerlog.com).

The dry cleaning of the turbine is carried out by blowing in granulate (nutshells or activated charcoal) of a specified particle size and volume – the volume depends on the turbocharger type – into the exhaust pipe before turbine under operating load by means of compressed air and permanently attached nozzles. The high kinetic energy produced during the impact of the granulate onto the nozzle ring and turbine blading causes the deposits to flake off. It is not necessary to reduce the engine load for the cleaning process. If you want and are interested for more in depth information regarding procedure and flow adjustment you need to subscribe to Seafarer’s World Forum (powered by chiefengineerlog.com).

Practical experiences gained over the years have shown that the intervals of wet cleaning can be extended when using the dry cleaning system.
It also became apparent that the increase of the cleaning interval for dry cleaning – from once a day to twice a day – results in a significant improvement of the cleaning result when using highly coating -forming heavy oil fuels.

Example of TC before and after cleaning

Benefits of dry cleaning compared with wet cleaning:

      • turbine can be cleaned at full load – thus no losses at all in the operational readiness of the engine;
      • short execution time of the cleaning procedure (approx. 20 min);
      • frequent use of the cleaning process effectively prevents deposits at nozzle ring and turbine blades

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Diesel engine troubleshooting and diagnostic

Every ship’s engine room is equipped with some kind of diesel engine and most big ships nowadays are powered by two-stroke diesel engines, although the usage of four-stroke engines for propulsion is increasing due to the flexibility in where they may be installed and the enhanced redundancy that a larger number of smaller engines can give. Four stroke diesel engines are commonly utilized to generate electricity.
Diesel engine troubleshooting or diagnosis is a tool that should help ensure the diesel engine’s dependability as well as its maximum efficiency, to prevent severe problems at sea and to have condition-based maintenance and be possible to assess the technical state of the engine sections without disassembling the engine.
Engine monitoring can be thought of as a simpler diagnosis that follows this simple rule: as long as the vital engine parameters are within a particular range, we can conclude that a critical defect is not imminent. However, such basic monitoring does not help striving for optimal engine efficiency or maintenance optimization and as a result, a more complete troubleshooting can be extremely beneficial.

The values of the engine parameters are affected by both the engine’s condition and the operating conditions (e.g. ambient elements such as draught, sea water status, air pressure, and temperatures, as well as selectable criteria such as demanded ship speed or specified electrical load). As a result, we must compare the values of diagnostic parameters not merely with their prior values, but also with the reference values obtained from the sea trial data, also known as model diagrams.

Because we can use different settings to analyze different engine components, different conditions should be used as independent variables for distinct troubleshooting and diagnostic metrics and model diagrams are typically based on the findings of sea trials or test beds.

The best troubleshooting and diagnosis parameters to use are measured engine values that meet the following criteria:

    • their value is dependent not only on operating conditions but also, to a large extent, on the technical state of the engine;
    • they assist us in avoiding the most serious faults;
    • they assist us in optimizing the maintenance process;
    • they can be measured using the engine equipment that is available.

Load index, engine torque, engine rpm and power and fuel specific consumption, calculated over a long enough period of time, are the troubleshooting and diagnostic measures most typically used for evaluating engine performance.

Engine overload is commonly produced by attempting to sail the ship through severe seas while setting the requested engine rpm to a high value. Usually, engine overload is frequently detected by the engine monitoring system, however regular monitoring of the operating point position is required to avoid such a problem.

Because fuel consumption varies with engine load, we must first compare the actual value with the model diagram value for the same engine power to develop a trend in Specific Fuel Consumption (SFOC). We can then display the deviation over time, most likely weeks, because some external influences, such as tide or weather conditions, may affect individual observations in the long run. If the SFOC is higher, it indicates that the total engine efficiency is worse, which should prompt more troubleshooting to determine the problem.

Engine vibrations are common, especially when starting the engine or sailing in rough waves. The majority of engine issues fall into two categories: combustion faults and mechanical faults.

The combustion defects, vibration-based condition monitoring may be further classified into two types: one is based on translational acceleration signals detected on the engine block or cylinder tightening bolts, and the other is based on torsional vibration signals produced from the torque meter. It is normally important to have data analysis software in order to use these signals. Even still, problems cannot always be detected automatically based on the studied vibration signals. As a result, any divergence should prompt a new search to pinpoint the specific cause of the issue.

Example of engine vibration diagram

At its most basic, the frequency vibrations are usually the most telling indicator of where the flaws are located, as the vibrations will have the same frequency or components with frequencies multiples of the frequency of the faulty portion. For example, very high frequency vibrations are most often caused by high speed components such as those found in turbochargers. The shafting system is commonly linked with very low vibrations.

Indicator diagrams, mean indicated pressure, exhaust gas temperature after each cylinder, compression pressure in each cylinder and maximum pressure in each cylinder are the troubleshooting and diagnostic metrics used to evaluate combustion.

The most common engine combustion symptoms include:

    • Dark smoke from the funnel
  • Dark smoke from the funnel usually indicates a lack of combustion air and it can appear when the engine starts, during a sudden load increase (e.g. during maneuvering and in rough seas due to abnormal engine loads). A failure in the turbocharging system might create dark smoke under constant engine loads.

    • An increase in the positive deviation of the mean exhaust gas temperature
  • The first stage in analyzing exhaust gas temperatures is to compare the actual value of the average exhaust temperature with the average value from the model diagram for the same engine power. The following issues can cause an increasing positive deviation of the average exhaust gas temperature:
        • high inlet temperature of the cylinder cooling water;
        • low inlet pressure of the cylinder cooling water;
        • high inlet temperature of the oil cooling the pistons;
        • low inlet pressure of the oil cooling the pistons;
        • insufficient combustion air.
    • An increase in the deviation of the exhaust gas temperature after a single cylinder
  • The first stage in analyzing exhaust gas temperatures after each cylinder is to compare the actual value to the average exhaust temperature after all cylinders at the same time.  Some variances in exhaust temperatures between units may be normal, but increases in detected deviations indicate that something has occurred and can be used to troubleshoot engine conditions. The following issues can cause an increasing positive variance in exhaust gas temperature after a single cylinder:
        • late combustion, caused by the wrong injection timing or by worn fuel injector valve, which can be identified using an indicator diagram;
        • a leaking exhaust valve, which can be identified by an increasing negative deviation of the compression pressure.
    • An increase in the negative deviation of the compression pressure in a single cylinder
  • When evaluating the compression pressure in a cylinder, compare the actual value of the compression pressure with the value from the model diagram for the same scavenge air pressure.
    The following issues, which are normally visible during a scavenging port examination, might cause a growing negative deviation of the compression pressure in a cylinder:

        • blocked cylinder inlet ports;
        • wear of the piston rings or the cylinder;
        • clogged or burned out piston rings.
    • An increase in the negative deviation of the maximum combustion pressure in a single cylinder
  • Compare the actual maximum combustion pressure in each cylinder to the average maximum combustion pressure in all cylinders at the same time when evaluating the maximum combustion pressure in each cylinder. Some variation in maximum combustion pressure between units is usual.
    An increasing negative deviation of the cylinder maximum combustion pressure can be caused by the following issues:

        • a low compression pressure, which should be eliminated first as previously described;
      • Example of low combustion pressure due low compression pressure

        • delayed combustion, which can be caused by incorrect injection timing or worn injection nozzles (this problem can be observed on the indicator diagram);
      • Example of low combustion due wrong timing

        • a decreased quantity of fuel injected, which can be caused by a worn plunger in the fuel pump (this can be confirmed by checking the Mean Indicated Pressure ) and if this is the cause the pump should be overhauled.
    • An increase in the negative deviation of the Mean Indicated Pressure, M.I.P. in a single cylinder or group of cylinders

The following diagnostic parameters are used to evaluate a turbocharger:  turbocharger rpm, exhaust temperature before and after the turbocharger, scavenge air pressure, air pressure drop at the air filter, air pressure drop at the air cooler, exhaust pressure after the turbocharger (also known as the counter-pressure) and the cooling water temperature difference at the air cooler.

The typical symptoms of turbocharging problems are:

    • Increased negative deviation of the scavenge air pressure

The following issues can cause an increasing negative divergence in scavenging air pressure:

        • a clogged air filter (which should be replaced first);
        • a malfunctioning or dirty turbocharger;
        • a clogged exhaust duct after the engine, which can be found by measuring the exhaust pressure after the turbocharger.
    • Increasing deviation of the turbocharger speed (positive or negative)

A corroded turbocharger nozzle ring or turbine blades, an excessive clearance between the turbine blades and the shroud or cover can all cause an increase in negative turbocharger speed deviation. As a result, on the model diagram, turbocharger speed should be referred to the scavenging air pressure.
The following issues can cause an increasing positive divergence in turbocharger speed:

        • a dirty air filter;
        • a dirty air cooler;
        • a dirty turbocharger, either air or gas side, which should be removed by washing both sides according to the manufacturer’s instructions.
    • Increasing positive deviation of the air pressure drop at the air filter

When assessing the air pressure decrease at the air filter, start by comparing the actual value to the value from the model diagram for the same scavenging air pressure. A dirty air filter, which should be cleaned according to the manufacturer’s instructions, might produce a rising positive deviation of the air pressure drop at the air filter.

View of turbocharger air filter

    • Increasing positive deviation of the air pressure drop at the air cooler

When assessing the air pressure drop at the air cooler, start by comparing the actual value to the value from the model diagram for the same scavenging air pressure. A dirty air side of the air cooler, which should be cleaned according to the engine manual, can cause an increasing positive deviation of the air pressure drop at the air cooler.

    • Increasing negative deviation of the cooling water temperature at the air cooler
  • A dirty water side of the air cooler, which should be cleaned according to the engine handbook, can create a growing negative deviation of the cooling water temperature differential.
    • Increasing cylinder block temperature near the scavenge box

The temperature of the cylinder block surface near the scavenge box should be assessed using an infrared camera or measured by placing the palm of the hand close to, but without touching, the cylinder block and comparing it to other cylinders. A rising cylinder block temperature near the scavenge box, particularly when accompanied with rising exhaust gas and cooling water temperatures, can be a sign of a scavenge box fire. This type of fire is frequently caused by worn piston rings or an overabundance of cylinder oil. When a scavenge box fire is detected, the engine load should be quickly reduced and a fire extinguishing method (CO2, steam, etc.) should be used in accordance with the engine manual.

The following diagnostic metrics are used to evaluate engine cooling: cooling water temperature after each cylinder, cooling water temperature at the engine’s inlet and piston cooling oil temperature at the engine’s inlet.

An rising positive deviation of the cooling water temperature difference at the cylinder is a common indicator of an engine problem.

When assessing the cooling water temperature differential at the cylinder, start by comparing the actual value to the value from the model diagram for the same engine power. Several problems can cause an increasing positive deviation of the cooling water temperature difference at a cylinder:

      • a crack in the cylinder liner (which can be accompanied by bubbles in the cooling water expansion tank);
      • a crack in the cylinder head (which can be accompanied by bubbles in the cooling water expansion tank);
      • an obstacle in the cylinder liner or the cylinder head cooling space (in this case there are no bubbles in the cooling water expansion tank).

Piece of rag found inside cooling pipe


The diagnostic parameters utilized for engine lubrication evaluation are: main bearing temperatures (if available), lubricating oil temperature before the engine, lubricating oil water content, lubricating oil pH and lubricating oil viscosity.

The typical signs of an engine lubrication problem are:

  • Increased positive deviation of the main bearing temperatures

The temperature of each main bearing should be compared to the limiting value, and an alert should be generated when it reaches the limit, which depends on both the main bearing material and the placement of the temperature sensor.

All possible causes of an increased positive deviation of the main bearing temperature are:

        • A seizure process in the bearing, which can be caused by material failure, a sudden load increase, or obstructed oil flow;
        • An obstructed flow in the crankshaft drilling caused by lubrication oil impurities;
        • A cylinder mechanical overload caused by an excessively high maximum combustion pressure;
        • Bearing corrosion

A main bearing seizure can result in the bearing’s disintegration and a main engine emergency stop.

Example of main bearing failure

  • High water content in the lubricating oil

The water content can be measured on-board with special equipment, but it can also be monitored continuously by a sensor fitted in the lubricating oil inlet line.

Example of water in oil tester

A rising water content in the lubricating oil can be caused by a number of issues, including:

        • insufficient or faulty operation of the lubricating oil separator;
        • a cooling water leak into the cylinder due to a crack in the cylinder liner or cylinder head;
      • Exampled of cracked cylinder liner

        Crank in cylinder head







        • excessive water condensation in the charge air after the cooler (this usually occurs when humidity is high and the scavenge air temperature is low, allowing the dew point to be reached). This can be verified by opening the scavenge box’s drain valve); a worn or broken stuffing box can allow water to seep from the scavenge box into the engine crankcase.

Lubricating oil with a high water concentration can cause bearing corrosion, inadequate lubrication, and bearing seizures.

  • Low pH of the lubricating oil

The pH of the lubricant oil can be measured aboard using pH test strips.

Example of pH test strips

A low pH of the lubricating oil can be caused by a number of issues, including an increased amount of acidic combustion products due to a high sulphur content in the fuel or a low TBN of the cylinder oil and a worn or broken stuffing box, which allows combustion products to enter the engine crankcase.

Low lubricating oil pH is a severe issue since it can cause bearing corrosion.

  • Low viscosity of the lubricating oil

Onboard, the viscosity of lubrication oil is determined by comparing the oil flow speed with a flow stick.

Example of a viscosity testing flow stick

A low viscosity of the lubricating oil can be caused by several issues, including:

        • unburned fuel oil leaking past the piston rings to the stuffing box and further into the crankcase through an untighten stuffing box;
        • contamination with fuel oil from fuel pump lubrication;
        • a high water content in the lubricating oil;
        • oil deterioration due to age or contamination.

Lubricating oil with a low viscosity can cause significant engine damage.

  • High contamination, or low dispersancy, of the lubricating oil

A spot test can be used to check for contamination and dispersancy in lubricating oil.

Example of a spot test used onboard

A drop of oil is placed on blotter paper and dried for a few hours in this test. The dry spot is then compared to the available example spots, allowing the insoluble components in the oil to be determined.
Lubricating oil contamination is typically caused by poor oil filtering or insufficient cleaning in the lubrication oil separator and oil contaminants can clog oil flow in small clearances and disrupt hydrodynamic lubrication.
The ageing of the oil usually causes low dispersancy of the lubricating oil. Lubricating oil dispersancy is required to separate larger size deposits into microscopic particles that may then be transported uniformly throughout the majority of the oil and afterwards removed by filtering.

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Diesel injection system explained…

At all engine loads, the purpose of the diesel engine fuel system is to deliver the correct amount of fuel, at the correct time, to the correct cylinder in the required condition and as a result, the system must be capable of controlling the quantity, timing, period, and sequence of delivery. There must also be control functions to ensure that the fuel is in good condition and that the delivery is appropriate for the actual load.
Systems range from the most basic mechanical hydraulic types to those that use load dependent, electronic controls to adjust quantity and timing and distribute to individual cylinders, but the basic requirements must be met regardless of how simple or sophisticated the system is.

Diesel engine basic fuel system

Fuel is drawn from the service tank by gravity or by an electrically or engine-powered supply pump and delivered to the high pressure fuel pump inlet rail, but to ensure proper injection viscosity, residual fuels must be heated after leaving the service tank.

Example of an electrically driven fuel supply pump

The high pressure pump in a basic direct fuel injection system usually delivers fuel directly to the fuel injection valves. The high pressure fuel pump can be used to control the amount of fuel entering the engine cylinder, as well as the timing of the fuel delivery, in conjunction with the fuel injection valve setting.

Sectional view of an high pressure fuel pump

The hydraulic pressure within the fuel injection valve causes the valve to open, allowing fuel to enter the cylinder combustion chamber directly.

Example of fuel injector sectional view

Example of fuel injector









The high pressure fuel pump and the fuel injection valve are typically regarded as the primary components of any diesel engine fuel system and the pump driving mechanism, as well as the features of these two components, can provide timing and quantity control.

A cam mounted on the engine camshaft is frequently used as the driving mechanism, but new modern engines are designed without a camshaft and rely on electronic fuel timing and quantity control (about common rail system you can read in here).

When using residual fuels, the fuel system necessitates a heating system with a viscosity control function and to avoid gassing, heated fuel is typically delivered under pressure to the high pressure fuel pump suction rail.

The load signal for any changes in fuel timing and quantity during engine operation is typically provided by an input from the engine governor (information about engine governor can be found in here).

The vast majority of high pressure fuel pumps used in diesel engines are jerk type, where jerk refers to the sudden, sharp movement of the pump plunger during fuel delivery. This results in a very rapid, almost instantaneous rise in fuel pressure in the supply to the fuel injection valve and in order to achieve this type of motion, the pumps must be driven by cams rather than cranks, as the fuel cam profile can be shaped to produce the desired delivery rate from the pump.

High pressure pumps on larger diesel engines are typically single units located near the cylinder cover for the unit they supply and the main camshaft controls the pumps. This means that the lengths of high pressure fuel pipes can be kept to a minimum.

Example of Main Engine with individual fuel pumps

Inline multi-cylinder pump blocks are commonly used for smaller engines. All of the high pressure pump cylinders for the entire engine are housed in these blocks. All of the fuel pump plungers are controlled by a single control rack.

Example of a fuel pump’s block

On some small engines, within the pump housing, a small sub-camshaft is used.

To ensure that piping losses are comparable, some engines position the pump block near the center of the engine, with equal length high pressure pipes to each fuel injector valve.

A high pressure fuel pump can be controlled in a variety of ways, including the quantity and timing of delivery, but the most common method is to use a helical profile machined into the pump plunger element to control the injection start and spill point by covering and uncovering the suction and spill ports in the pump barrel.

Example of different helix cut on plunger trailing edge

The start or end of injection, or both, can be varied depending on how the helix is positioned and variations include:

  • constant start and variable end
  • variable start and variable end
  • variable start and end. This one is a type of variable injection timing.

Instead of having helix cut into the plunger, another common method is to use suction and spill valves to control the start and end of delivery. The term spill refers to the point at which delivery is terminated and fuel is spilled back to the pump suction or return line.

Both of these methods of control achieve fuel distribution to the various cylinders by having a separate pump element for each cylinder unit of the engine. In addition these two main methods described, there are other ways to gain control. For example, electronically controlled fuel injection systems have been introduced in some recent engine designs.

Common rail electronically controlled injection

Constant delivery pumps are used in this type of system to deliver high pressure fuel to the manifold, which is also known as a common rail. This fuels each cylinder through electronically controlled timing valves that control the admission of high pressure fuel to the injection valves (about common rail system you can read in here).

Some engines make use of distributor-style fuel pumps.

Unlike the previous control methods, this type of fuel pump controls not only the timing and quantity of fuel delivered, but also the cylinder unit to which the fuel is delivered. Smaller engines are more likely to use it.

It has been demonstrated that the thermal efficiency of a diesel engine is proportional to the ratio of maximum cylinder pressure, Pmax, to compression pressure, Pcomp (Pmax/Pcomp). The higher the ratio, the higher the efficiency and the lower the specific fuel consumption (SFOC).
The value of Pmax varies with load as a linear or straight line characteristic when the fuel injection timing is fixed.

The maximum value of Pmax is constrained by the strength of the combustion chamber components, whereas the minimum value of Pcomp is constrained by the need to achieve sufficient compression temperature to ignite the fuel.

The value of Pmax can be changed by adjusting the timing of the fuel injection and is normally increased by advancing the fuel injection timing and decreased by retarding it.

If we advance the fuel timing as the load decreases, the value of Pmax can be kept at its maximum, though this is only practical over a portion of the load range. This increases the ration Pmax/Pcomp, and thus the thermal efficiency, over a portion of the load range while decreasing SFOC. This is why variable injection timing (VIT) was developed and implemented (you can read about VIT in here).

From what we’ve already said about helix control, you should be able to deduce that changing the vertical position of the spill port relative to the leading edge of the pump plunger changes the point at which injection begins. Raising the spill port in relation to the plunger will cause the injection timing to be delayed, while lowering it will cause the injection timing to be advanced. This shift in relative position can be accomplished by raising or lowering the pump barrel or plunger.

As previously stated, the spill valve is used to vary the end of injection on a valve control type high pressure fuel pump, with later opening increasing the delivered fuel quantity. We also need to vary the point at which the suction valve closes, in the VIT control of this type of pump. Later closing advances the injection timing, while earlier closing retards it. When the governor output lever moves in response to a change in engine load, the linkage moves to rotate the suction and spill valve eccentrics on the pump with valve control.

Example of VIT for valve control type

Other than changing the valve timing or repositioning the barrel, there are several other ways to achieve VIT. This usually necessitates a change in the position of the cam follower or the camshaft. If the cam follower is attached to a pivoted horizontal lever on an eccentric shaft, rotating the shaft causes the follower to move horizontally relative to the vertical center line of the fuel pump and cam.

Internal and external leakage caused by erosion of pump elements and valve seats, as well as damage caused by fuel contaminants, are the most common fuel pump faults. Severe internal or external leakage can have an impact on the timing and amount of fuel delivered to the cylinder and can be caused by general wear or cavitation erosion. Cavitation happens when there is a sudden drop in pressure, causing vapour bubbles to form, which then collapse, resulting in excessive impact forces as the liquid fills the vapour space. Moreover, the high flow speed across control edges and valve seats can cause erosion as well.

Fuel contaminants can cause abrasive and corrosive damage.

Overheating of the pump elements caused by either high temperature or low fuel lubricity can cause plungers to stuck inside barrels or, in extreme cases, to seizure.

Seized plunger inside barrel due overheating

Some engines have fuel pump lubrication facilities to prevent this from happening.

Due to the extremely fine clearances of the operating parts, fuel pump maintenance is usually limited to the replacement of seals, valves, and the pump element. Typically, adjustments are limited to pump timing and the initial setting of the VIT mechanism.

Pump timing testing and adjustment methods differ depending on the type of pump.
The following are some of the more common methods for checking pump timing:

  • measurements of plunger height relative to barrel;
  • measurements of suction and delivery valve lift at a given crank position;
  • matching a reference mark on the pump element or tappet to one on the casing; checking the point of spill cut-off

The majority of fuel injection fuel pumps are cam driven, positive displacement types. The rate at which fuel is delivered to the engine cylinders is determined by engine speed and the cam’s operating profile. The fuel cam shape is divided into several sections.

These are the base circle, the peak (also known as the dwell), the rising flank, and the falling flank. Most reversible fuel cams have identical rising and falling flanks.

When the cam follower is on the base circle and the peak of the cam, the fuel pump plunger is stationary; when it is on the flanks, it is moving. The rising flank of the cam can be thought of as the operating profile, with three distinct sections: acceleration, controlled speed, and deceleration and the rate of fuel delivery is governed by the cam profile’s controlled speed section.

Fuel pump cams can be separate components or integrated into the camshaft and only those that are separate components can be individually adjusted.

Split cams are used by some manufacturers to make replacing damaged cams easier. Although some engines still use bolt on or spline mounted cams, the majority use hydraulic tapered sleeve couplings, also known as muff couplings, to mount the cams on the camshaft.

Example of tapered sleeve coupling camshaft

The shaft is fitted with a tapered sleeve with a threaded end, and the cam, which has an internal tapered bore to match the sleeve, is mounted on it. The assembly is held together by a locknut. The cam has an oil hole that runs from the outer surface to the inner bore. This is usually blocked with a screwed plug.

The fuel injection valve’s function is to allow fuel into the cylinder while also acting as a non-return valve to prevent air and combustion gas from returning to the fuel system. Although there are numerous fuel injector designs, the majority are similar and operate on the same principle.

Example of fuel injector valve

The valve is made up of two parts: a body and a fuel nozzle that houses the needle valve. The injection spring provides positive seating for the needle valve via a thrust piece. The spring compression screw can be adjusted to change the needle valve lift pressure. As the fuel pressure acting on the needle valve rises, the generated hydraulic force overcomes the spring force, and the needle valve lifts off the seat, allowing fuel to flow to the injector nozzle and into the cylinder through the nozzle holes. The pressure drop across the nozzle hole accelerates the fuel, and as it passes through the high pressure dense air, the high velocity fuel stream breaks up into fine droplets. When the pressure in the fuel injector falls, the needle valve reseats due to spring force, and the injection stops.

When a standard type of fuel injection valve is open, fuel flows through the valve. When using hot heavy fuel oil, there is a risk that the fuel will cool down sufficiently to block the injector due to its high viscosity. To reduce this risk, it was common practice to switch to diesel fuel before shutting down the engine. Nowadays, on new modern engines, many fuel injectors have the fuel recirculating continuously, when the injector is closed.
On new engines, recirculation is accomplished by incorporating a slide valve within the main needle valve.

The main needle valve and the slide valve are seated when the fuel pressure in the valve is at normal supply pressure. Fuel is flowing through the valve body because the recirculation port is open. As the high pressure fuel pump begins to deliver fuel, the fuel pressure rises enough to lift the slide valve, closing the recirculation port. The fuel pressure is now rapidly rising, and the needle valve opens to allow fuel into the cylinder. As the failing pressure causes the needle valve to seat, ending injection, and then the slide valve to seat, allowing recirculation to resume. With these configurations, the engine can be stopped on heavy fuel oil for indefinite periods of time as long as the supply pump is operational and heating is available.
Using recirculating type fuel injection valves eliminates the need for fuel valve cooling systems because the continuous through flow of fuel removes enough residual heat to prevent the fuel injector from overheating.

The most common faults found with modern fuel injection valves are:

  • Damaged or fouled needle valve seating surfaces leading to dribble or leakage;
  • Scored or burnt needle valve and housing leading to seizure or internal leakage;
  • Damaged or blocked nozzle holes;
  • Breakage or weakening of injector spring;
  • Leakage at mating surfaces;
  • Carbon deposits due to overheating

The majority of modern fuel injectors are maintained through periodic testing in a test rig. Any operational flaw is normally corrected by general cleaning, replacement of the needle valve and nozzle assemblies, replacement of the injector spring, and replacement of the entire injection valve. Some injection valves may have renewable seals, while others may require mating surface reconditioning. Some recirculation types have service exchange cartridges that include the needle valve, slide valve, and thrust assembly. These types typically have separate nozzle tips that can be replaced if they become damaged.

One of the most serious risks when operating a diesel engine is the risk of a high-pressure fuel leak spraying fuel mist onto hot engine surfaces, potentially resulting in a serious fire.

Example of generator fire due fuel leak

SOLAS requires double-skinned pipes to be installed to protect against high-pressure sprays.

Example of double skinned fuel pipe

The inner pipe is typically made of solid drawn steel pipe, while the outer skin is typically made of a flexible metal sheath with a drain provision, which is usually connected to a collecting pot and equipped with a leak detection device. Some systems include a cut out for the affected unit’s high pressure fuel pump.

Some smaller engines, as an alternative to this arrangement, have all of the high pressure pipes contained within a steel enclosure that drains to an alarmed collection pot.

Furthermore, precautions must be taken to reduce the possibility of any fuel leaks reaching the heated surfaces. Any surfaces that may be impacted by fuel system leaks and are above 220 degrees Celsius, the self ignition temperature of a typical fuel, must be insulated.

Example of identified hot spot in auxiliary engine using a thermal camera

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Auxiliary engines (4-stroke) lubrication explained…

This is another on-demand post and its purpose is to explain the 4-stroke lubrication system from operational point of view.

All running gear of the 4-stroke engine is forced lubricated by an engine-driven gear type pump which takes the oil from the engine sump tank. The same oil from engine sump tank is also provided to the engine pistons as a cooling medium.
An electrically-driven pre-lubricating oil pump is fitted to feed oil to the bearings and other operating gear before the engine starts, as this decreases wear on the engine in the period between the engine starting and the engine-driven pump building up lubricating oil pressure. After the engine has started and the engine-driven lube oil pump is supplying oil at the correct pressure, the pre-lubrication pump is stopped. The LO pre-lubricating pump is normally operated from its local control panel and will run constantly whilst the engine is on automatic standby; the pump switch should be set to AUTO, however it can be changed to the MANUAL position for manual control.

Example of pre-lubricating LO pump

The engine-driven pump and the electrically-driven LO pre-lubricating pump both take suction from the engine sump then discharge through a duplex filter to the engine oil supply rail. A pressure control valve at the oil entry maintains a steady pressure independent of the engine rpm and oil temperature, same as the electrically-driven LO pump features a relief valve back to the pump suction.

The temperature of the lubricating oil is maintained at 65°C by the LO cooler, which has a three-way temperature controlled bypass valve.
The LO cooler is a plate heat exchanger with oil circulating through the flow channels and water circulating through parallel channels in a counter-flow design from the central fresh water cooling system.

Auxiliary engine LO cooler opened for cleaning and maintenance

The flow of oil through the cooler is regulated by the three-way valve which allow some or all of the circulating lubrication oil to by-pass the cooler in order to maintain the correct LO temperature.

A centrifugal bypass filter, especially on big engines, mounted on the engine base frame supplements the main LO filter. A portion of the LO supplied by the engine-driven LO pump enters the centrifugal filter and returns to the oil sump in the base frame during operation. The filter uses centrifugal force to remove high-density sub-micron particles and it is powered by the oil supply.

Centrifugal oil filter arrangement on auxiliary engine

The engine main bearings, crankpin bearings, top end bearings, camshaft system, valve rocker units and turbocharger bearings are lubricating from the system. Normally, the turbocharger receives lubrication oil from the main circuit via a branch pipe. A flow of cooling oil is also directed to the piston and cylinder liner running surface lubrication is primarily supplied by splash oil and oil vapour from the crankcase.

Basic principle of wet sump lubrication. Source and credit: Thomas Schwenke


The entire lubrication system is part of the engine construction and there are no valves which need to be operated within the engine lubricating system.

On some of engine types lubrication of the piston rings is from below, through bores in the lower part of the cylinder liner. This separate cylinder lubrication is supplied by a separate lubrication system via a cylinder lubrication pump which takes suction from the main LO supply to the engine bearings. Lubricating oil is taken from the crankcase system and supplied to each cylinder liner via a block-type distributor which is controlled by pulses from the engine monitoring system. Oil is directed into the cylinder liner through a number of radial holes located around the liner, and opposite the piston rings when the piston is at bottom dead canter. This ensures that there is a small quantity of oil between the piston rings, and the piston rings spread this oil over the liner surface when the piston moves up and down the cylinder. Usually, the cylinder lubrication pump may be selected for OFF or AUTO (ON) at its local control panel. When selected for AUTO, the cylinder lubrication pump operates in accordance with the preset mode which is either as follows:

      • Manual/OFF
      • Automatic (normal setting, the cylinder lubrication operates when the engine load is higher than 50%)
      • Run-in (cylinder lubrication operates continuously irrespective of the load when the engine is started.

Only lubricating oil of an approved grade and quality must be used in the generator engine system. The engine sump tank is replenished with fresh oil from on of vessel’s LO storage tanks and LO in the engine sump must be cleaned in a LO separator on a regular basis, and ideally, the
oil should be continuously centrifuged when the engine is running. Usually, a LO separator is kept running on the generator engine that is in use. If more than one generator engine is running, the separator is to be run on each diesel generator sump on a daily basis. It is most important that the correct valves are lined-up for separation to prevent the pumping out of the sump on one running engine to another running engine.

The generator engine LO separators operate on the same principle as the main engine LO separator. LO from the generator engine sump flows from the sump to the suction side of the relevant separator feed pump, via a suction filter. The LO feed pump circulates the LO through the heater and then supplies it to the separator. From the separator, the cleaned oil returns to the generator engine sump. Sludge from the generator engine LO separators flows to the LO sludge tank.

Generator engine LO should be sampled and tested at intervals recommended by the LO supplier. The results of the testing provide an indication as to engine operation and the need for LO replacement.

Please follow the link if you are interested on learning and understand more about Maritime Bearings and Lubrication. The courses are provide by Alison, are free and you need only to subscribe to their platform via this link.

If you have any questions regarding above, please feel free to use our existing forum Seafarer’s World, Telegram Chief Engineer’s Log Chat or Instagram and will try to answer to all your queries. You can use the feedback button as well!

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