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Enhancing Marine Engine Efficiency: A Solution for Low-Speed Operation

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Author: Daniel G. Teleoaca – Marine Chief Engineer

Marine engines are the unsung heroes of the shipping industry, tirelessly powering vessels across vast oceans and seas.

However, these workhorses face a unique challenge when it comes to low-speed operation. Low speed operation can cause various problems for marine engines, such as increased fuel consumption, reduced power output, higher emissions, and more wear and tear. The inefficiency of marine engines at lower speeds can have significant economic and environmental implications.

Preceding the implementation of emission-limiting regulations, some of the ships, especially containers, were generally engineered to achieve maximum cruising velocities of 30 knots. Presently, operators are obligated to comply with regulatory frameworks such as the carbon intensity indicator (CII) and the energy efficiency existing ship index (EEXI).

As a consequence, cruising veers off at approximately 18 knots, which is roughly two-thirds the speed for which the engines were originally designed. As a result, engines operate extremely inefficiently at low loads, consuming significantly more fuel and emitting significantly more CO2 than is required.

Without intervention, Wartsila predicted in 2022 that by 2023, over one-third of container ships would be non-compliant, based on an analysis of the global fleet. Moreover, in the absence of intervention, 80% of container ships will be classified under the lowest CII category by 2030.

In this article, we’ll explore the reasons behind this inefficiency and the options available to improve marine engine performance when running at low speeds.

Understanding the Inefficiency

Marine engines are designed to operate at a certain range of speed and load, depending on the type and size of the engine, the ship’s hull form, the propeller characteristics, and the operating conditions. When the engine operates outside this range, it can suffer from inefficiency and performance loss. There are several key reasons for this inefficiency:

  • Reduced Combustion Efficiency: A cause of marine engine inefficiency at low speed is the incomplete combustion of fuel in the cylinders. The combustion process in a marine engine depends on many factors, such as the fuel quality, the air-fuel ratio, the injection timing, the compression pressure, the ignition temperature, and the combustion duration. When the engine operates at low speed and load, some of these factors can be adversely affected, resulting in incomplete combustion of fuel. Incomplete combustion can lead to lower power output, higher fuel consumption, higher emissions of carbon monoxide (CO), hydrocarbons (HC), particulate matter (PM), and smoke, and more carbon deposits in the cylinders and turbocharger.

  • Mechanical Losses: At low speeds, the engine’s mechanical components, such as pistons, bearings, and crankshafts, experience higher frictional losses. This additional resistance leads to decreased engine efficiency. Moreover, the turbocharger is a device that uses the exhaust gas from the engine to drive a compressor that increases the air pressure and density in the intake manifold. The turbocharger improves the engine performance by allowing more air and fuel to be burned in each cylinder. The turbocharger efficiency depends on the pressure ratio between the exhaust gas and the intake air, which is called the boost pressure. The boost pressure is highest at high engine speed and load, when there is more exhaust gas available to drive the turbocharger. When the engine operates at low speed and load, there is less exhaust gas available, and the boost pressure drops. This means that less air is supplied to the cylinders, resulting in lower power output, higher fuel consumption, higher emissions of nitrogen oxides (NOx), and more turbo lag.

  • Propeller Inefficiency: One of the main causes of marine engine inefficiency at low speed is the mismatch between the engine and the propeller. The propeller is a device that converts the rotational energy of the engine into thrust force for propulsion. The propeller efficiency depends on the ratio of the propeller speed to the ship speed, which is called the advance ratio. The propeller efficiency is highest at a certain advance ratio, which corresponds to a certain engine speed and load. When the ship operates at low speed, the advance ratio increases, and the propeller efficiency decreases. This means that more engine power is wasted as friction and turbulence in the water, rather than converted into useful thrust.

Therefore, the effects of marine engine inefficiency at low speed can be summarized as follows:

  • Lower power output: The engine produces less power than it is capable of, resulting in lower ship speed or lower reserve power for maneuvering or emergency situations.
  • Higher fuel consumption: The engine consumes more fuel than it needs to produce a given amount of power, resulting in higher operating costs and lower profitability.
  • Higher emissions: The engine emits more pollutants than it should, resulting in environmental damage and potential non-compliance with emission regulations.
  • More wear and tear: The engine suffers from more stress and damage due to friction, corrosion, erosion, vibration, overheating, fouling, etc., resulting in higher maintenance costs and lower reliability.

Options to improve marine engine efficiency and performance at low speed

The inefficiency of marine engines at low speeds is a persistent challenge, but there are several innovative solutions available to mitigate this issue. Some of these options are:

  • Variable Geometry Turbochargers (VGTs): VGTs are turbochargers that can adjust their geometry to optimize airflow at different engine speeds. They help maintain higher combustion efficiency, even at low speeds, reducing fuel consumption and emissions.

  • Slow Steaming Strategies: Slow steaming involves deliberately operating a vessel at reduced speeds to conserve fuel. It has become a popular strategy in the shipping industry, allowing ships to run more efficiently at lower RPMs, thus saving fuel.

  • Dual-Fuel Engines: Dual-fuel engines are designed to run on a combination of natural gas and diesel fuel. These engines offer improved combustion efficiency and emissions control, making them an attractive option for low-speed operation.

  • Waste Heat Recovery Systems: Waste heat recovery systems capture and reuse the heat generated by the engine’s exhaust. They can be used to produce additional power or drive other ship systems, enhancing overall energy efficiency.

  • Upgraded Propellers: Shipowners can consider investing in more efficient propeller designs, specifically tailored to their vessels’ operating profiles. Modern propeller designs are more adaptable to a wide range of ship speeds.

  • Improved Hull Design: The vessel’s hull design can also impact its performance at lower speeds. Optimized hull shapes can reduce hydrodynamic resistance and improve overall efficiency.

  • Hybrid Power Systems: Some vessels employ hybrid power systems that combine traditional diesel engines with electric propulsion. This setup allows for efficient power delivery at various speeds, including low-speed operation.

  • Engine derating: Engine derating is a method of reducing the maximum power output of an engine by adjusting its settings or components. Engine derating can improve the engine efficiency at low speed by reducing the mismatch between the engine and the propeller, and by optimizing the combustion process and the turbocharger operation. Engine derating can also reduce the emissions of NOx, CO, HC, and PM. However, engine derating can also reduce the reserve power of the engine, and may require the approval of the engine manufacturer and the classification society.
  • Turbocharger cut-out: Turbocharger cut-out is a method of disconnecting one or more turbochargers from an engine by closing a valve or opening a bypass. Turbocharger cut-out can improve the engine efficiency at low speed by increasing the boost pressure and the air supply to the cylinders. Turbocharger cut-out can also reduce the emissions of CO, HC, and smoke. However, turbocharger cut-out can also increase the emissions of NOx, and may cause the turbocharger to overheat or surge.

In conclusion, addressing the inefficiency of marine engines at low speeds is critical for both economic and environmental reasons. The shipping industry has made significant strides in developing technologies and strategies to improve engine efficiency during slow steaming and low-speed operation. These solutions not only reduce fuel consumption but also contribute to lower emissions and a more sustainable maritime industry. As technology continues to advance, marine engines are likely to become more versatile, making them more efficient across a broader range of operating speeds, ultimately benefiting the entire global shipping industry.

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Revolutionary Ammonia-Powered Engine by MAN B&W Paves the Way for Sustainable Shipping

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Author: Daniel G. Teleoaca – Marine Chief Engineer

MAN Energy Solutions (MAN ES) has announced a breakthrough in its research and development of a two-stroke engine that can run on ammonia, a carbon-free and sulphur-free fuel. The company successfully completed the first test of its MAN B&W engine operating on ammonia at its Research Center Copenhagen (RCC) in July 2023.

Ammonia is considered one of the most promising candidates for the future of green shipping, as it can be produced from renewable energy sources and does not emit any greenhouse gases or air pollutants when burned in an engine. According to the International Maritime Organization (IMO), maritime shipping is responsible for around 2.5 percent of global greenhouse gas emissions and needs to reduce them by 70 percent by 2050.

Source and credit: maritimemag.com

MAN ES started working on a B&W two-stroke engine operating on ammonia back in 2019 with a pre-study of the fuel supply and injection concept combined with several hazard and hazard and operability studies (hazid/hazop) together with classification societies, shipowners, yards, and system suppliers. The following year, a second test engine arrived in Copenhagen, enabling a parallel-test engine setup with different fuels at RCC.

The first test of the ammonia engine was conducted on a 50 percent load at RCC’s testbed no. 5, which is equipped with a newly developed ammonia injection system and a newly designed combustion chamber. The test showed that the engine can run stably and efficiently on ammonia with low NOx emissions. The test also demonstrated that the engine can switch seamlessly between ammonia and conventional fuels such as diesel or liquefied natural gas (LNG).

Brian Østergaard Sørensen, Head of Two-Stroke Research and Development at MAN ES, said: “This is obviously an ambitious undertaking, but we can meet it. The industry is already on board and working intensively with us towards greener maritime shipping.” He added that the company aims to have a commercially available two-stroke ammonia engine by as early as 2024, followed by a retrofit package for the gradual rebuild of existing maritime vessels by 2025.

The development of the ammonia engine is part of MAN ES’s strategy to offer a fuel-flexible portfolio of two-stroke engines that can run on almost any fuel or fuel quality. The company has already developed engines that can run on methanol, ethanol, liquefied petroleum gas (LPG), and hydrogen. The final goal for two-stroke engines is to run them entirely on carbon-neutral and carbon-free fuels.

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Demystifying Marine Engine Crankshaft Deflection Measurements: A Comprehensive Guide

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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.

The Importance of Air Seals on Main Engine Exhaust Valves

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In the world of engineering and machinery, precision and reliability are paramount. One critical component that plays a vital role in ensuring the efficiency and performance of a combustion engine is the exhaust valve. To optimize the functioning of this crucial part, engineers have developed air seals that help maintain a secure and efficient seal. In this blog post, we will explore the significance of air seals on main engine exhaust valves, the types of air seals used, and their role in enhancing engine performance.

The Main Engine Exhaust Valve: A Crucial Component

Before diving into the intricacies of air seals, it’s essential to understand the importance of the main engine exhaust valve in a combustion engine. In an internal combustion engine, whether it’s found in a car, a ship, or an industrial machine, the exhaust valve serves a fundamental purpose. The main engine exhaust valve is a vital component of a marine diesel engine that controls the timing and duration of the exhaust gas flow from the cylinder to the turbocharger. The exhaust valve consists of several parts, such as the spindle, the housing, the seat, the hydraulic cylinder, and the air cylinder. The air cylinder is a device that uses compressed air to close the exhaust valve against the hydraulic pressure that opens it. The air cylinder has a piston that moves up and down along with the spindle, creating an air spring effect that ensures a smooth and reliable operation of the exhaust valve.

The Challenge: Gas Leakage

One of the primary challenges in designing exhaust valves is preventing gas leakage. Inefficient sealing can lead to several adverse consequences, including:

  • Reduced Efficiency: Gas leakage results in a loss of engine efficiency, as the engine must work harder to compensate for the escaping exhaust gases.
  • Environmental Impact: Incomplete combustion due to gas leakage can lead to increased emissions, contributing to air pollution and environmental degradation.
  • Increased Fuel Consumption: Gas leakage forces the engine to burn more fuel to maintain power output, leading to higher operational costs.

Types of Air Seals

To address the issue of gas leakage, engineers have developed various types of air seals, each with its own unique characteristics and applications. The air seal is a device that prevents air leakage from the air cylinder to the exhaust valve housing. It is made of a metallic outer ring and a rubber seal that contacts the spindle. The seal can have different shapes depending on the type of valve. The air seal is important for maintaining the proper air pressure and spring force in the air cylinder, as well as for protecting the spindle from corrosion and fouling by the exhaust gas. A faulty or worn-out air seal can cause air loss, reduced performance, increased fuel consumption, and higher emissions.

Exhaust valve air piston seal ring overhaul. Source and Credit: Rheinstinitz Karl Caler

Here are some common types of air seals used in main engine exhaust valves:

  • Floating Ring Seals: Floating ring seals consist of two concentric rings, with the outer ring rotating along with the valve. This design helps create a dynamic seal, minimizing gas leakage.
  • Poppet Valve Seals: Poppet valves are commonly used in internal combustion engines. They employ a cylindrical plug to control gas flow. Air seals in poppet valves help ensure a tight fit between the valve and the valve seat, preventing gas leakage.
  • Rotary Valve Seals: Rotary valves, found in some engines like rotary engines and two-stroke engines, use rotary seals to maintain a seal as the valve rotates. These seals play a crucial role in preventing gas leakage.
  • Labyrinth Seals: Labyrinth seals consist of intricate channels and ridges that create a tortuous path for gas to escape. This design effectively reduces gas leakage by increasing the distance exhaust gases must travel before exiting.

The Role of Air Seals in Enhancing Engine Performance

Air seals on main engine exhaust valves are vital for several reasons:

  • Gas Tightness: The primary function of air seals is to maintain gas tightness within the combustion chamber. This ensures that exhaust gases exit through the designated path, optimizing engine efficiency.
  • Reduced Emissions: By minimizing gas leakage, air seals contribute to lower emissions. This is especially critical in modern engines to meet stringent environmental regulations.
  • Improved Fuel Efficiency: A well-sealed exhaust valve reduces the engine’s workload, leading to improved fuel efficiency and reduced operational costs.
  • Enhanced Engine Longevity: Air seals help protect the engine from excessive wear and tear, prolonging its operational life.

The air seal on the main engine exhaust valve is a simple but important device that ensures efficient and safe operation of the engine. Therefore, it is essential to inspect and replace the air seal regularly as per the maker’s recommendations.

Example of exhaust valve overhauling. Source and Credit: DG E LEARING ADU ACADEMY

In conclusion, in the intricate world of internal combustion engines, even the smallest components play a critical role in ensuring performance and efficiency. Air seals on main engine exhaust valves are a testament to the precision and engineering prowess required to design and maintain these complex machines. By preventing gas leakage, these seals contribute to reduced emissions, improved fuel efficiency, and increased engine longevity. As technology continues to advance, we can expect further innovations in air seal designs, driving the continuous improvement of combustion engines in various applications.

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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The Necessity of Cutting Out One of the Vessel’s Main Engine Unit: A Comprehensive Guide for Marine Engineers

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Maintaining the efficient and safe operation of a vessel’s main engine units is crucial for smooth sailing and ensuring the safety of all onboard. In certain circumstances, it becomes necessary to cut out the combustion on or to isolate one of the main engine units. This article will delve into the process of cutting out combustion and isolating the unit, discuss when it is necessary, highlight the factors marine engineers need to consider, and outline the essential precautions and measures to be taken. The extent of the work to be carried out depends, of course, on the nature of the trouble.

Understanding the Process of Cutting Out Combustion

When a marine engineer decides to cut out the combustion on a main engine unit, it means intentionally stopping the fuel injection into that particular unit. By doing so, the engine’s power output is reduced, and it ceases to contribute to the propulsion of the vessel. This process involves a systematic and controlled approach to ensure the safety and functionality of the remaining operational units.

When is it Necessary to Cut Out Injection on a Main Engine Unit?

There are several scenarios in which cutting out the injection on a main engine unit becomes necessary:

    • Technical Malfunctions: In the event of a malfunction or breakdown in one of the main engine units, cutting out the combustion allows the crew to isolate the faulty unit and prevent further damage. This ensures the vessel can continue its operations with the remaining functional engines. The technical malfunctions can be, for instance but not reduced to:
      • blow-by at piston rings or exhaust valve
      • bearing failures which necessitate reduction of bearing load
      • faults in the injection system.
    • Maintenance and Repairs: Routine maintenance and repair activities may require cutting out the combustion on a main engine unit. This allows the marine engineer to safely conduct necessary maintenance procedures, such as inspections, replacements, or repairs, without endangering the crew or vessel.
    • Fuel Economy and Efficiency: During periods of reduced power demand, such as when sailing at lower speeds or in calm waters, cutting out the combustion on one or more engine units can optimize fuel consumption and increase overall efficiency. This strategy helps minimize operating costs and extend the lifespan of the engines.

Process of Cutting Out Combustion on a Main Engine Unit

    • Initial Assessment: The marine engineer must conduct a thorough assessment of the engine to identify the specific unit requiring combustion cut-out. This includes analyzing performance data, monitoring alarm systems, and conducting visual inspections.

    • Preparing the Engine: Prior to cutting out combustion, the engineer needs to ensure the vessel is at a safe operating condition. This involves reducing the load on the affected unit and synchronizing the remaining engines, if required, for optimal performance.

    • Shutting Down Injection: Once the engine is prepared, the marine engineer can proceed with cutting out the injection on the designated unit. This is typically achieved by isolating the fuel supply, closing relevant valves, and activating the engine control system to cease fuel injection.

In case of camshaft type engine the injection can be cut out by lifting and securing the fuel pump roller guide. The entire procedure for cutting out the injection on one of the units is fully described in the engine manual.

Should the engine be kept running with the injection cut out for an extended period, the lubricating oil feed rate for the respective cylinder must be reduced to the minimum. If the piston and exhaust valve gear are still operational, do not shut down the piston cooling oil and cylinder cooling water on that particular unit.

In case of electronic controlled engines, cutting out the injection is more simpler as everything is done from the Engine Control Panel Unit.

You must be aware that with an injection pump cut out the engine can no longer be run at its full power.

Process of Combustion and Compression cut out. Piston still working in cylinder.

This measure is permitted in the event of, for instance, water is leaking into the cylinder from the cooling jacket/liner or cylinder cover.

The procedure is as follow:

    • Cut out the fuel pump by lifting and securing the roller guide.
    • Put the exhaust valve out of action and lock it in open position.
    • Shut-off the air supply to the exhaust valve, and stop the lube oil pumps. Dismantle and block the actuator oil pipe. Restart the lube oil pumps.
    • Close the cooling water inlet and outlet valves for the cylinder. If necessary, drain the cooling water spaces completely.
    • Dismantle the starting air pipe, and blank off the main pipe and the control air pipe for the pertaining cylinder.
    • When operating in this manner, the speed should not exceed 55% of MCR speed.

Note: The joints in the crosshead and crankpin bearings have a strength that, for a short time, will accept the loads at full speed without compression in the cylinder. However, to avoid unnecessary wear and pitting at the joint faces, it is recommended that, when running a unit continuously with the compression cut-out, the engine speed is reduced to 55% of MCR speed, which is normally sufficient to maneuver the vessel.
During maneuvers, if found necessary, the engine speed can be raised to 80% of MCR speed for a short period, for example 15 minutes.
Under these circumstances, in order to ensure that the engine speed is kept within a safe upper limit, the overspeed level of the engine must be lowered to 83 % of MCR speed.

Process of Combustion Cut Out. Exhaust Valve closed. Piston still working in cylinder.

This measure may be used if, for instance, the exhaust valve or the actuating gear is defective.

The procedure is as follow:

    • Cut out the fuel pump by lifting and securing the roller guide.
    • Put the exhaust valve out of action so that the valve remains closed (lift the guide or stop the oil supply and remove the hydraulic pipe).

Please note that, the cylinder cooling water and piston cooling oil must not be cut out.

Process of piston, piston rod, and crosshead suspended in the engine. Connecting rod out

This measure may be used if, for instance, serious defects in piston, piston rod, connecting rod, cylinder cover, cylinder liner and crosshead.

The procedure is as follow:

    • Cut out the fuel pump by lifting and fixing the roller guide.
    • Put the exhaust valve out of action so that the valve remains closed.
    • Dismantle the starting air pipe. Blank off the main pipe and the control air pipe for the pertaining cylinder.
    • Suspend the piston, piston rod and crosshead, and take the connecting rod out of the  crankcase.
    • Blank off the oil inlet to the crosshead.
    • Set the cylinder lubricator for the pertaining cylinder, to ‘ ‘zero’’ delivery.

Please note that, in this case the blanking-off of the starting air supply is particularly important, as otherwise the supply of starting air will blow down the suspended engine components.

Precautions and Measures for Cutting Out a Main Engine Unit

    • Safety Protocols: The utmost priority when cutting out a main engine unit is ensuring the safety of the vessel, crew, and engineers involved. Marine engineers must follow established safety protocols, wear appropriate personal protective equipment (PPE), and coordinate with the ship’s personnel to minimize risks during the procedure.

    • Communication and Coordination: Effective communication between the marine engineer, engine room crew, and bridge team is crucial. The bridge team must be aware of any changes in engine configuration to adjust vessel operations accordingly and maintain situational awareness.

    • Monitoring and Alarms: While cutting out combustion, continuous monitoring of engine parameters, alarms, and performance indicators is essential. Any unusual readings or abnormalities should be promptly reported and addressed to prevent further complications.

    • Documentation: It is vital to maintain comprehensive documentation throughout the process, including detailed reports of the engine condition, actions taken, and any observations made during the combustion cut-out. This information assists in analyzing the cause of the malfunction and aids in future maintenance planning.

In conclusion, cutting out the combustion on a main engine unit is a critical procedure that marine engineers may need to undertake to safeguard vessel operations and prevent further damage. Whether due to engine malfunction, contamination, or maintenance requirements, this process requires careful assessment, preparation, and adherence to safety protocols. By following the necessary precautions and measures, marine engineers can effectively isolate and address the issues affecting the main engine unit, ensuring the safety, efficiency, and reliability of the vessel’s propulsion system.

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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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Marine Fuel Injector Valves – Ensuring Optimal Performance

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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)

    2. 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.

    3. 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.

    4. 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.
    5. 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.

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    6. 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!

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!

What you need to know about Sulzer RT-Flex engine

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The Sulzer RT-flex engine is essentially a standard Sulzer RTA slow-speed two-stroke marine diesel engine except that, instead of the usual camshaft and its gear drive, fuel injection pumps, exhaust valve actuator pumps, reversing servomotors, and all their related mechanical control gear, the engine is equipped with a common-rail system for fuel injection and exhaust valve actuation and full electronic (computer) control of engine functions. Two control oil pumps are provided near the engine local control stand, and one of these must always be operational to ensure that the common rail fuel and exhaust valve operation systems can function. The control pump starts automatically once one of the crosshead lubricating oil pumps is started.

The engine is monitored and controlled by a WECS (Wartsila Engine Control System) unit. This is a modular electronic system with separate microprocessor control units for each cylinder. Overall control and supervision is by means of separate, duplicate microprocessor control units.

The cylinder microprocessor control units are mounted on the front of the engine at the common rail in the hot-box, which is located below the top engine platform.

The engine is a single-acting, two-stroke, reversible, diesel engine of crosshead design with exhaust gas turbocharging and uniflow scavenging. Tie rods bind the bedplate, columns and cylinder jacket together. Crankcase and cylinder jackets are separated from each other by a partition, which incorporates the sealing gland boxes for the piston rods. The cylinders and cylinder heads are fresh water cooled.

The exhaust gases flow from the cylinders through the hydraulically operated exhaust valves into a manifold and then on to the exhaust gas turbochargers which work on the constant pressure charging principle.
The charge air delivered by each turbocharger flows through an air cooler and water separator into the common air receiver. Air enters the cylinders through the scavenge ports, via valve groups, when the pistons are nearly at their bottom dead centre (BDC) positions. At low loads two electrically-driven auxiliary blowers supply additional air to the scavenging air space.

The pistons are cooled by bearing lubricating oil supplied to the crossheads by means of articulated lever pipes. The thrust bearing and turning gear are situated at the engine driving end. The fuel and servo oil pumps for the common rail fuel system and exhaust valve actuation are driven by gearwheels from the crankshaft.

The engine is started by compressed air, which is controlled by the electronic starting air system. In case of failure of the engine remote control system (from the bridge or the engine room telegraph) the engine can be controlled from a local (emergency) control stand located on the port side of the engine on the middle platform. There is an ECR back-up control system which is linked with the local (emergency) control system.

The engine lubrication system, with the exception of turbocharger and cylinder lubrication, is supplied by one of two main pumps, which take suction from the main engine lubricating oil sump tank and supply the main bearings. The engine main bearings and thrust block are supplied with lubricating oil by the duty main lubricating oil circulation pump. There are two pumps fitted and these are located at the aft end of the engine with one working and the other switched to automatic standby. The oil is cooled before supply to the engine. Oil from the main bearing system is also supplied, via articulated lever pipes, to cool the working piston crowns. The main bearing and crosshead oil systems are interconnected as the crosshead pumps take their suction from the main bearing LO supply line to the engine.
Two crosshead LO pumps, one working and one on standby, take their suction from the main LO supply to the engine, after the automatic backflush filter and supplies oil at increased pressure to the crosshead bearings and to the servo oil pumps. The bottom end bearings are also supplied with LO from the associated crosshead with the oil flowing down a bore in the connecting rod. The lubrication of crossheads and connecting rod bottom end bearings is made through articulated lever pipes.

The turbochargers are supplied with lubricating oil from the turbocharger LO system. There are, usually two or three turbocharger LO pumps (depending of the engine size and design), one/two operating and one on automatic standby. These pumps supply oil to the turbocharger bearings from the turbocharger LO sump tank via a cooler. The pumps have suction filters and there is also an automatic backflushing filter unit with a back-up bypass filter.

With regard to cylinder lubrication more information can be found on this link.

The fuel oil is supplied to a common rail by the fuel supply pumps which are driven from the crankshaft by a gear system. The fuel pumps are arranged in a V form with four pumps in each bank. The pumps deliver pressurised fuel oil to a collector which then supplies the common fuel rail which is maintained at a pressure of about 1,000 bar at full load (the actual pressure varies with engine load). Recently, for safety and operational reasons the pressure has been reduced to 600 bars. All parts of the high pressure fuel system are sheathed to prevent high pressure fuel leakage from entering the engine room spaces. The fuel supply pumps are driven by a camshaft via three-lobed cams. The lobed cams and the speed of the camshaft means that each pump makes several strokes during a crankshaft revolution. There are six or eight fuel supply pumps (depending on the engine size) and the output of the pumps is such that seven pumps have the capacity to meet the full load requirements of the engine. With only six pumps operational, the engine load must be reduced below maximum. The common fuel rail is divided into two equal sections, one serving the forward six cylinders and the other serving the six aft cylinders. The common rail volume is such that the fuel pressure is constant throughout the operation of the engine.

There are three fuel injectors fitted in each cylinder cover and high pressure fuel oil is supplied to these from the common rail. Each cylinder has its own injection control unit which controls the fuel supply to the injectors from the common fuel rail. Each injection control unit has three rail valves and three injection control valves, one of each for each injector. The rail valve is an electrically operated spool valve which can be moved to each end of its casing by electrical signals from the WECS. The spool valve acts as an open or closed valve and when in the open position it directs control oil to the injection control valve. The injection control valve opens and allows high pressure fuel from the common rail to pass to the fuel injector so beginning fuel injection at that injector. When the WECS signals the spool valve to close, the injection control valve is closed and hence fuel injection stops. Control oil is supplied by the servo and control oil manifold at a pressure of 200 bar. The rail valves are bi-stable solenoid valves with a fast actuation time; the valve is not energised for more than 4ms at any time.

The WECS controls the fuel injection system via the Flex Control Module (FCM-20) which not only regulates the start and end of injection but also monitors the quantity of fuel injected. The fuel quantity sensor measures the actual amount of fuel injected and this information is relayed to the control system. The control system then calculates any change in fuel timing required from the engine operating conditions and the actual fuel quantity injected. The functioning of the fuel injection system is monitored at each cycle and changes are made for the next cycle if necessary.
Operation of the rail valves is under the control of the WECS, which can adjust the timing and quantity of fuel injection to suit operating conditions.
Normally all three cylinder fuel injectors, which are of the hydraulically actuated type, operate together but as they are independently controlled it is possible for them to be programmed to operate separately. In the event of one of the fuel injectors or its actuation system failing, the engine may continue to operate with the remaining two injectors. At low engine speeds one or two of the fuel injectors can be cut out for each cylinder to minimise exhaust smoke.
The remaining operational fuel injector(s) operate at longer injection periods with the high fuel pressure maintained by the common rail. With injector(s) cut out the operating injector(s) are changed over every 20 minutes to prevent overheating of the cut out injector(s) and to ensure that all of the injectors have equal running.
The fuel quantity delivered to the engine by the fuel preparation unit is considerably greater than is actually required by the engine with the excess flowing back to the mixing unit of the main fuel preparation unit. The mixing unit is located at the FO circulating pump suction and also takes a FO feed from the low pressure FO supply pump which draws HFO from the duty HFO service tank. From the circulating pumps the HFO flows through the steam heaters and then to the supply manifold for the high pressure common rail supply pumps. A pressure regulating valve, set at 10kg/cm² is fitted between the engine FO inlet and outlet lines and this allows the correct fuel oil supply pressure to be maintained at the engine inlet.
The main engine is designed to operate on HFO during manoeuvring. All pipes are provided with trace heating and are insulated. For reasons of safety, all high-pressure pipes are encased by a metallic hose. Any leakage is contained and led to an alarmed fuel oil leakage tank. The engine may be operated on MDO if necessary.

The starting air system of the RT-flex engine is similar to that of a standard RTA engine except for the control of the cylinder starting air valves which is incorporated in the WECS rather than a starting air distributor. Starting air is supplied to the engine starting air manifold from the starting air receivers via the starting air shut-off valve. The individual cylinders are then supplied with starting air via branch pipes which have flame arresters fitted.
The cylinder starting valve is operated by pilot air and the pilot air valve is controlled electrically by the cylinder control module. The starting pilot air valve is opened and closed directly by the Flex control module (FCM-20) once every revolution at defined crank angles during the starting period. When the engine has started the starting system is shut down.

Each cylinder has a single exhaust valve centrally located in the cylinder cover which is hydraulically opened, but closed by air pressure acting on the piston located below the hydraulic actuating cylinder. When hydraulic pressure is applied to the actuating piston to open the exhaust valve, the air trapped below the air piston is compressed. When the hydraulic opening pressure is removed the air pressure acts on the piston to close the exhaust valve and this is known as the ‘air spring’. The space above the air piston is vented and make-up air is supplied to the space below the piston from the control air system via a non-return valve to replace any leakage that may have occurred.
The exhaust valve is fitted with a series of vanes on the stem known as a spinner. When the exhaust valve is opened, exhaust gas escaping from the cylinder acts on the spinner and causes the valve to rotate. Rotation of the valve evens out the temperature of the valve, and as the valve is still rotating when it reseats it creates a light grinding effect which removes deposits from the valve seat and valve face.
The FCM-20 controls the exhaust valve opening and closing. Hydraulic pressure for opening the valve comes from the servo oil common rail. This is pressurised to 200 bar by the servo oil pumps which are driven by the same gear drive system as the fuel common rail pumps. The FCM-20 controls an exhaust rail valve which then activates the exhaust hydraulic control slide valve and this directs hydraulic oil to and from the exhaust valve actuator unit. The servo oil acts on the lower face of the free-moving exhaust valve actuator piston and as the piston moves upwards, when servo oil pressure is applied, it exerts an hydraulic force on the exhaust valve piston and opens the exhaust valve.
The hydraulic system connecting the upper face of the exhaust valve actuator piston with the exhaust valve piston (the hydraulic pushrod) is filled with engine bearing oil and a connection with the bearing circulation system ensures that the space is always fully charged. This arrangement provides a complete separation of servo hydraulic system and valve actuation/bearing lubricating oil systems, and enables the exhaust valves to be serviced without disturbing the servo oil system.

The RT-flex engine control is shared between the WECS internal engine control and the external propulsion control systems which comprise the remote control system, the safety system, the electronic governor and the alarm monitoring system.

The WECS is the core engine control. It processes all actuation, regulation and control systems directly linked to the engine:

      • Common rail monitoring and pressure regulation
      • Fuel injection, exhaust valve and starting air valve control and monitoring
      • Interfacing with the external systems via the CAN-open or MOD-bus
      • Engine performance tuning, IMO setting and monitoring

The WECS modules are mounted directly on the engine and communicate via an internal CAN-bus. Operator access to the WECS-9520 is integrated in the user interface of the propulsion control system. The manual control panels and the flexView system allow for additional communication with the WECS. The flexView software allows the operator to communicate with the WECS and enables the operator to see operating parameters as required.
Each engine cylinder has its own module for all cylinder related functions; all common functions are shared between the cylinder modules.

If you have any questions regarding above, please feel free to use our existing forum Seafarer’s World 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!

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  • YouTube video credit: Brian Johannesen; Marine Tech Hub; Marine Engineer (PARAMI);

What you need to know about Main Engine Manoeuvring and Control systems

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The remote control system for the main engine is intended for use in the wheelhouse, the engine control room (ECR), and on the bridge wings for the purpose of controlling the engine by means of a combined telegraph and manoeuvring lever.

Example of bridge main engine telegraph

The Engine Manoeuvring System (EMS), which is interfaced to the Engine Control System (ECS), is what makes it possible to control the engine remotely from a distance (ECS). Every main engine has its own control system, complete with a telegraph lever of its own. When you move the active telegraph lever, the ECS will take over and automatically start, stop, and reverse the engine as well as control the speed setting.

Example of main engine control system

The ECS is responsible for controlling the various functions of the engine’s operation based on the input signals that it receives from either the bridge or the local operation panels. The ECS is responsible for starting the engine in the correct direction and for controlling its operational functions, including the fuel injection and exhaust valve actuation, in order to ensure that the engine maintains the desired speed throughout its operation. The ECS is also responsible for providing safety features, which protect the engine in the event that any of the operational parameters exceed the limitations that have been set.

In most cases, the telegraph transmitter in the wheelhouse is used in conjunction with the engine management system (EMS) and the engine control system (ECS) to accomplish automatic maneuvering, which includes stopping, starting, and reversing the main engine.
The speed of the engine is automatically controlled, and the set point is transmitted from the telegraph transmitter located in the wheelhouse (or active station). The speed set point is communicated to the ECS, which, in turn, communicates with the ECUs to manage the engine speed.
For the purpose of determining the speed of the main engine, the Engine Control System (ECS) makes use of a Tacho Adapter Module to establish a connection between the tacho pick-ups that are attached to the engine and one of the CPUs that are located on the serial interface board.

The ECS works in conjunction with the independent main engine safety system (ESS) for main engine emergency stop, overspeed and shutdown protection.

Example of Main Engine Safety System

In the engine control room the main engine safety system has its own panel, which displays the relevant information for each shutdown input channel, actual main engine rpm etc; it is also possible to make adjustments and cutouts on the shutdown input channels. Pushbuttons with LED indication on the ESS panel are used for Shutdown indication, Shutdown Cancel function and Shutdown Reset function. At the bridge, the shutdown and shutdown cancel functions are shown on two pushbuttons on the EMS panel.

Example of engine management system panel

The overspeed, shutdown and slowdown functions are carried out by the engine protection system in response to signals from sensors on the main engine and the ancillary systems. A wrong way alarm is also incorporated in the alarm system. Manual emergency stops are operated from pushbuttons on the bridge, bridge wings, engine control room console and LOP.

The bridge main operation station is equipped with a telegraph transmitter; the transmitter is equipped with a set point potentiometer and is located in the bridge centre console. The bridge telegraph transmitter is connected with the port and starboard bridge wing control panels. The ECR is equipped with a similar telegraph receiver. The bridge and ECR telegraph levers are equipped with potentiometers with hardware connections to the EMS system.

View of main engine telegraph

The electrical shaft system which interconnects the bridge telegraph with the bridge wing control telegraphs is a synchronising system, in which non-activated
control levers follow the active control lever. For example, when the bridge control is master, the two bridge wing levers automatically follow the master lever in the wheelhouse.

For back-up communication of telegraph orders from the bridge to the engine side local control stand, during local control, the system is fitted with a separate emergency telegraph system which is completely independent from the EMS. By means of a dial indicator and lamps for each telegraph order, the communication telegraph indicates the requested order. On the bridge the dial is moved to the position for the new order and the indicator lamp for that direction and speed will start flashing. At the engine side control station a bell will start sounding and the engine side emergency telegraph will start flashing for the desired speed and direction position.

Example of engine local manoeuvring post

To accept the new order the dial at the engine side control station telegraph must be turned to correspond with the desired engine speed and direction. The lamp will change to a steady light and the bell will stop.

Transfer to a control stand (target takes control) with higher priority  is always possible without pre-selection (proposal/request) at an active control stand with lower priority. This transfer cannot be prevented at the control stand with lower priority. The local (engine side) control stand is the operating station with the highest priority. The engine control room has the next highest priority and the bridge control station the lowest priority.

A change from local control directly to automatic bridge control is not possible. There is only one exception: if an ECR telegraph potentiometer fault is present at the time of change request, the proposal to change to automatic bridge control is automatically given and has to be acknowledged.

When Bridge Control is selected and the system is not in FWE mode, starting, stopping and control of the main engine speed is controlled by the position of the bridge telegraph handle. Moving the telegraph handle from stop to ahead or astern will cause the starting sequence to be activated, ie, the ECS will be instructed to supply starting air until the main engine rpm has reached starting level. At this point starting air is removed and fuel is supplied and the engine speed is controlled as required.

If the main engine start attempt failed, a new repeated start will automatically be executed immediately. After three failed start attempts a start blocking occurs, and the bridge has to move the telegraph handle to the stop position before a new start can be performed.

If the main engine is ordered to move in the opposite direction whilst still rotating, starting air will not be supplied until the engine’s speed has decreased below the reversing level. The ECS controls braking air application to the engine and the engine can be brought to the reversing speed quickly as it is possible to regulate the braking air supply timing.

When ECR Control is selected the starting, stopping, reversing and speed control of the main engine is handled from the ECR telegraph handle located in the engine control room control console.

When the bridge requests a speed change the main engine direction and speed is altered by moving the bridge telegraph control handle to the desired position and this will initiate the telegraph alarm. An engineer in the ECR moves the ECR telegraph handle to the same position as that of the bridge telegraph. This performs the necessary speed and direction change and at the same time acknowledges the telegraph alarm.

If the engine is not ready for start, e.g, it is start blocked, the Start Block LED on the manoeuvring panel is illuminated. Starting interlock (blocking) is activated by the following:

      • Main engine local control on
      • Main engine safety system shutdown or emergency stop (control air pressure low, safety air pressure low, main start valve blocked, sain start valve blocked)
      • Start failure (start air time-out or maximum number of failed start attempts)
      • Turning gear engaged
      • Start air pressure low
      • Auxiliary blowers not in automatic
      • Engine running
      • Safety system off
      • EMS malfunction

Slow turning of the main engine is normally used before the engine is started after a prolonged period of standstill and is done by turning the engine for 1-2 revolutions on reduced starting air. If the engine has been stopped for more than 30 minutes the system indicates that a slow turning should be initiated. The ECS activates the starting air system to supply starting air to the cylinders in reduced quantities so that the engine turns over slowly on a reduced starting air pressure. If the slow turning is not completed within the preset time the ECS signals a failure and blocks a further start until the cause of the failure has been rectified. If slow turning failure occurs the engine must not be started until the cause of the failure has been determined and corrected. In an emergency situation the start interlock can be cancelled by the CANCEL LIMITS at the bridge panel and the engine can be started.

A facility exists for prolonged turning over of the engine on air and this is known as Air Run. This facility is normally used after engine maintenance in order to check that the engine will turn readily or after prolonged stop in port.
The cylinder indicator cocks should be open when operating the air run facility. During air run the fuel command is automatically set to zero so there is no risk of the engine starting. The air run facility functions at engine standstill only and the engine turns on air whilst the AIR RUN pushbutton in the Manual Control panel is pressed.

If the start attempt is unsuccessful a second start attempt is initiated and REP. START is indicated in the display and a repeated start alarm is released. When the engine speed drops down below the firing speed the ECS will shut down the fuel supply to the engine fuel injectors and will initiate another start procedure.
If the engine stops again after the maximum number of start attempts (normally three), the start sequence is terminated with an alarm for three start attempts and a start blocking, which must be reset by putting the telegraph lever to the stop position before any further start attempts can be made.

The EMS hardware and peripherals are constantly monitored by the EMS in order to identify any faults which might develop. Supervision is usually carried out for:

      • The bridge telegraph and ECR telegraph
      • The speed sensing circuit
      • The electronic governor
      • The auxiliary voltages
      • The solenoid valves
      • The internal analogue/digital and digital/analogue converters
      • The memory check
      • The computer cycle

If a fault becomes active it is sensed by the EMS and this triggers audible and visual alarms; these are indicated at the operating panels on the bridge and in the ECR. The audible alarm is only activated at the station in control.

To comply with classification society rules, the system freezes the momentary operating conditions as far as possible. In a frozen condition the operator has to transfer control to manual mode in the ECR or at the engine local station. A reset can only be done in manual mode.

If you have any questions regarding above, please feel free to use our existing forum Seafarer’s World 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!

What you need to know about crankcase relief valves

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When the engine is operating under normal conditions, the atmosphere in the crankcase typically has a significant quantity of relatively large oil droplets, of around 150 – 200 microns, floating around in the existing warm environment. The chance of the droplets being ignited by a heat source is extremely rare due to the small surface area relative to the total volume of the droplets.

When a hotspot is generated due an overheating event, for example the failure of a bearing or a bearing’s lubrication failure, the temperature will generally exceed 300 ºC (as per laboratory tests oil mist is formed at a temperature of about 350 ºC). In this case the lubricating oil that spills onto the heated surface will turn to vapour, oil mists generated by being boiled off can produce particles between 3 to 10 microns. This mist is visible and is known as a blue smoke. Temperature and area of surface contact affect the rate of oil mist generation. At this stage, a temperature as low as 150°C could result in ignition. Ignition by a hotspot, which may be that which triggered the initial vaporization, is now a possibility. This results in the combustible gasses igniting, as the ignition temperature for this type of oil mist can be extremely low depending on the type of oil being atomized which in turn ignites the fine droplets that are present in the mist. For this reason, regulations require that the engine must be equipped with an oil mist detection system that will detect an oil mist before it can reach levels where it saturates the atmosphere to such an extent that there is a risk of fire. For more information about oil mist detector follow this link.

The blue smoke will continue to grow in size and density until the lower flammability limit is exceeded. The explosion that occurs as a direct consequence can range from being relatively mild, with explosion speeds of a few millimeters per second and little rise in heat and pressure, to being severe, with shock wave and detonation velocities of 2 to 3.3 kilometers per second and pressures of 30 atmospheres produced.

Example of typical blast pressure-time curve

It is clear that after the initial explosion, there is a drop in pressure; however, if the explosion is not dealt with in a safe manner and there is damage to the crankcase closure, it is possible that air could be drawn into the crankcase, thereby creating the environment for a secondary explosion that could be more violent. This can be seen by looking at how the pressure drops after the initial explosion. The availability of fuel and oxygen are the key elements that control the size of explosions of this type; however, it is possible that air will be pulled in due to the minor vacuum that is generated by the primary explosion. It’s possible that the passage of the shockwave may break the bigger oil droplets into smaller sizes that are more easily combustible, which will result in the creation of a supply of fuel.

Example of an engine after crankcase explosion

For this reason, all organizations involved set a set of rules in this regard. The most important is that crankcases are required to have lightweight spring-loaded valves or other quick-acting and self-closing devices installed so that pressure can be released from the crankcases in the event of an internal explosion while also preventing any subsequent inrush of air. The valves are required to have a design and construction that allows them to open rapidly and be fully open at a pressure that is not greater than 0.2 bar.

Structure of a crankcase relief valve

The number of relief valves varies with the engine size. For example, in engines having cylinders not exceeding 200 mm bore and having a crankcase gross volume not exceeding 0,6 m3, relief valves may be omitted. In engines having cylinders exceeding 200 mm but not exceeding 250 mm bore, at least two relief valves are to be fitted; each valve is to be located at or near the ends of the crankcase. Where the engine has more than eight crank throws an additional valve is to be fitted near the centre of the engine. In engines having cylinders exceeding 250 mm but not exceeding 300 mm bore, at least one relief valve is to be fitted in way of each alternate crank throw with a minimum of two valve. In engines having cylinders exceeding 300 mm bore at least one valve is to be fitted in way of each main crank throw.

Example of main engine crankcase relief valves arrangement

The combined free area of the crankcase relief valves fitted on an engine is to be not less than 115 cm2/m3 based on the volume of the crankcase. The free area of the relief valve is the minimum flow area at any section through the valve when the valve is fully open.

As part of their maintenance, during running of the engine, check if there are any leaks. If a leak occurs, replace the O-ring inside the relief valve. If work involving risks of mechanical damage to the flame arrester has taken place, a visual inspection of the flame arrester should always be performed before starting the engine.

Check on the whole circumference that all the plates in the flame arrester are evenly distributed and that no local openings exist.
If one or more plates in the flame arrester are damaged, the relief valve must be disassembled and the flame arrester replaced. The complete flame arrester has to be replaced after a crankcase explosion.

The video below is self explanatory  regarding onboard relief valve maintenance.

These relief valves can’t be tested and calibrated onboard due lack of means and testing equipment. The calibration is done in the manufacturing facility and test of these valves require specialized equipment as can be seen in below training video.

If you have any questions regarding above, please feel free to use our existing forum Seafarer’s World 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!

Source and Bibliography:

  • YouTube video training credit – Anold Kim; Informative clips; Schaller Automation
  • DNV and Lloyd Register rules and regulations
  • Photo credit: researchgate.net and chiefengineerlog.com

What you need to know about cylinder liner temperature monitoring

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I believe that most of you have noticed that most of the new and large engine models are equipped with temperature monitoring sensors on the cylinder liners. The systems are known under different names and layouts (e.g. Mapex) and are developed by different marine engineering companies (e.g. Wartsila, Kongsberg, etc.) but all serves the same purpose.

Example of cylinder liner temperature sensors

The cylinder liner temperature monitoring system is comprised of temperature sensors that are installed within the cylinder liners.

Example of cylinder liner temperature sensors arrangement

These temperature sensors monitor the temperature of the liner and are interfaced to the alarm system of the ship. In the event that the liner temperature goes over the predetermined thresholds, an alert will be triggered.

Example of a liner with sensor position

The system’s objective is to identify instances of thermal instability on the running surfaces of the cylinder liners, which can be caused by:

    • Oil film break down between liner and piston rings and subsequent seizure.
      Early action can stabilize the situation and prevent scuffing.
    • Loss of cooling. This will affect both fuel pumps and exhaust side sensors simultaneously on the affected units.
    • Broken or collapsed piston rings. The temperature level will increase over time. Piston ring failure can be detected during scavenge port inspection.

Two temperature sensors are installed in each cylinder liner, one on the fuel pump side and one on the exhaust side. These sensors are part of the cylinder liner temperature monitoring system.

Example of cylinder line sensor installation area

The alarm set points need to be continuously optimized in the manner that will be detailed in the following paragraphs in order to ensure the quickest possible reaction time in the event of temperature instability and to avoid false alerts.:

If the parameters are set too low, false alarms will be triggered during any regular service load, such as 75% of MCR, hence it is imperative that Tmax and Tmaxdev are not allowed to do so. False alarms will occur if the values are not high enough. Whenever there is a variation in the level of engine load, Tmax needs to be recalibrated so that it corresponds to the new level.
It is imperative that Tmax and Tmaxdev be modified and set to values that are both as low and as close to the temperature band of each sensor as is technically possible in order to guarantee an adequate level of sensitivity. In the event that there is an abnormal temperature variation while the machine is operating at part load, this will ensure the quickest possible reaction time.

If many excessive temperature warnings are being raised by single cylinder units, it is of the utmost importance to inspect the condition of the cylinders on the units in question. Scavenge port inspection is performed at the next available opportunity in order to accomplish this objective. The purpose of this is to guarantee that the piston rings and cylinder liners remain in satisfactory working condition at all times.

Units that have just undergone maintenance will invariably exhibit temperature instability for the first few days of operation. In light of the fact that the overhauled unit is anticipated to stand out from the rest, the engineers should become accustomed with the typical temperature differences that occur after overhauls.

The same goes for when the load is increased after prolonged periods of steady (low) load operation; you should anticipate some light instability as a result of the abrupt change in ring geometry. This is quite natural, although the severity and pattern of it cannot be predicted. Therefore, one must have patience and provide enough time for the geometry to adapt.

In the event of scuffing, the temperatures of the liner will oscillate dramatically, and the peak temperatures will be higher than the average temperature measured by all sensors. However, when the load is lower, it may be essential to monitor more closely since the maximum temperature deviation from the average will be lower than when the load is higher; hence, the value of Tmaxdev must be adjusted downwards accordingly.

Scuffing example. Two units are indicating scuffing. This is difficult to detect but may be detected manually or by AMS by a ΔTmaxdev set to 25°C or lower and a Tmax set to 175°C.

Example of wall temperature diagrams

Above one unit is indicating scuffing, detected by AMS by a ΔTmaxdev set to 30°C or lower and a Tmax set to 170°C.

In the event of scuffing, increase cylinder lubrication and reduce the load and the Pmax on the cylinder unit in question.

Above two units are indicating scuffing, detected by AMS by a ΔTmaxdev set to 25°C or lower and a Tmax set to 150°C.

On the image above, one unit is indicating scuffing. This is difficult to detect but may be detected manually or by AMS by a ΔTmaxdev set to 15°C or lower and a Tmax set to 140°C.

If you have any questions regarding above, please feel free to use our existing forum Seafarer’s World and will try to answer to all your queries.

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!

Source and Bibliography:

  • MAN B&W –  Circular letter 2245-0150-0001