Category Archives: Environmental

Navigating Efficiency: The Role of Low-Resistance Rudders in EEXI Compliance

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In the ever-evolving world of maritime regulations, the Energy Efficiency Existing Ship Index (EEXI) stands as a guiding light toward a greener, more sustainable future. Among the innovative technologies employed to meet EEXI requirements, low-resistance rudders have emerged as a key component for enhancing a vessel’s energy efficiency.

Example of vessel rudder

In this article, we will explore the significance of low-resistance rudders, the challenges they pose, the available technology on the market, and what marine engineers must consider to sail smoothly in compliance with EEXI.

The Significance of Low-Resistance Rudders

Rudders are a vital part of a ship’s steering system, but they also play a crucial role in a vessel’s hydrodynamic performance.

One of the possible ways to improve the energy efficiency of a ship is to use a low resistance rudder. A low resistance rudder is a type of rudder that reduces the water resistance and drag of the ship, which can result in significant fuel savings and lower emissions. According to some studies, low resistance rudders can reduce fuel consumption by up to 5% and carbon dioxide emissions by up to 4.5%. Moreover, low resistance rudders can also improve the maneuverability and stability of the ship, as well as reduce the noise and vibration levels.

Low-resistance rudders are designed to minimize drag and water resistance, which, in turn, reduces the energy required to steer the ship. By implementing these rudders, marine engineers can enhance a vessel’s energy efficiency and reduce its environmental impact—both central objectives of EEXI compliance.

Challenges on the Horizon

However, designing and installing a low resistance rudder on a ship is not a simple task. It requires careful consideration of various factors and challenges, such as:

  • The rudder profile: The shape and thickness of the rudder plate affect the flow of water around it and the pressure distribution on it. A streamlined rudder profile can reduce the drag and increase the lift of the rudder, which can enhance its performance and efficiency.
  • The rudder parameters: The size, aspect ratio, sweep angle, and balance ratio of the rudder influence its hydrodynamic characteristics and forces. The optimal values of these parameters depend on the ship type, size, speed, propeller design, and operating conditions.
  • The rudder type: There are different types of rudders available for ships, such as spade, flap, twisted, fishtail, Schilling, Becker, etc. Each type has its own advantages and disadvantages in terms of resistance, lift, torque, cavitation, etc. The selection of the proper type of rudder should be based on the specific requirements and constraints of each ship.
  • The number and location of rudders: The number and location of rudders affect the interaction between the rudders themselves, as well as between the rudders and the hull and propeller. The spacing between rudders should be sufficient to avoid interference and ensure effective steering. The position of the rudders should be such that they are properly oriented within the propeller’s outflow, so as to maximize their effectiveness.

Technology on the Market

To address these challenges, several advanced technologies for low-resistance rudders are available:

  • Advanced Hydrodynamic Design: Innovative rudder designs, often computer-aided, reduce hydrodynamic drag and optimize efficiency.
  • Materials and Coatings: High-quality materials and specialized coatings reduce friction and fouling, contributing to lower resistance.
  • Rudder Bulb: Some rudder designs incorporate a bulb, similar to a ship’s bulbous bow, to further reduce drag.
  • Intelligent Control Systems: Smart rudder control systems adapt to various operational conditions, optimizing rudder angles for maximum efficiency.
  • Maintenance Technology: Anti-fouling systems and regular inspection technology help keep the rudder surfaces clean and efficient.

What Marine Engineers Need to Do

Marine engineers play a pivotal role in the successful implementation and maintenance of low-resistance rudders:

  • Hydrodynamic Assessment: Evaluate the vessel’s hydrodynamic characteristics and operational profile to determine the most suitable low-resistance rudder design.
  • Supplier Collaboration: Work closely with reputable rudder suppliers to select the most appropriate design and technology for the vessel’s specific needs.
  • Installation Oversight: Oversee the precise installation of the low-resistance rudder, ensuring it integrates seamlessly with the existing steering system.
  • Performance Monitoring: Implement a monitoring system to track the rudder’s performance over time. Regular inspections can help detect any wear or fouling that may affect efficiency.
  • Crew Training: Ensure that the vessel’s crew is trained to operate the low-resistance rudder effectively and adapt to its performance characteristics.
  • Maintenance Regimen: Develop a proactive maintenance plan to keep the rudder surfaces clean and free from fouling, optimizing energy efficiency.

In conclusion, low-resistance rudders are more than just a compliance tool; they represent a commitment to enhancing the sustainability and energy efficiency of the maritime industry. With the right technology, engineering expertise, and diligent oversight, marine engineers can steer vessels toward a future where efficiency and environmental responsibility coexist seamlessly, all while adhering to the EEXI regulations.

Therefore, designing and installing a low resistance rudder on a ship requires a lot of planning, coordination, and supervision from vessel marine engineers. They have to select the right rudder profile, parameters, type, number, and location for their ship’s needs and budget. They have to oversee the fabrication and installation of the rudder according to the relevant regulations and standards. They have to ensure that the rudder meets the specifications and requirements for EEXI compliance. And they have to evaluate the performance and benefits of the rudder after its installation.

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!

Source and References:

  • EEXI | Energy Efficiency Existing Ship Index – DNV
  • EEXI and CII – ship carbon intensity and rating system – IMO
  • Everything you need to know about the EEXI – SAFETY4SEA
  • Design and Evaluation of Ship Rudders | SpringerLink
  • OSK-ShipTech test a rudder bulb – OSK Design Youtube channel

Sailing Smoothly: The Role of Low-Friction Coatings in EEXI Compliance

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In the maritime world’s ongoing quest for sustainability, the Energy Efficiency Existing Ship Index (EEXI) regulation has become a guiding star. Among the technologies and strategies used to meet EEXI requirements, low-friction coatings stand out as a promising tool for enhancing energy efficiency. In this article, we’ll dive into the significance of low-friction coatings, the challenges they pose, the available technology on the market, and what marine engineers need to know to navigate these waters successfully.

The Power of Low-Friction Coatings

Low-friction coatings, often referred to as hull coatings, are specially designed to reduce the drag and resistance that vessels encounter as they move through the water.

Low resistance coating applied to the vessel hull during dry docking

Low friction coatings are types of industrial coatings that reduce friction, wear, and energy losses between two contacting surfaces. They have different properties and applications depending on the materials used, such as PTFE, molybdenum disulfide, tungsten disulfide, nickel teflon, and diamond-like carbon. They can improve the efficiency and performance of various components and machines in different operating environments, such as heat, chemicals, or clean room conditions.

By applying these coatings to a ship’s hull, marine engineers can enhance its hydrodynamic performance, thus increasing energy efficiency and reducing fuel consumption by helping reduce the drag and resistance of a ship in water—a pivotal goal of EEXI compliance.

According to some studies, low friction coatings can reduce fuel consumption by up to 10% and carbon dioxide emissions by up to 9%. Moreover, low friction coatings can also protect the hull and propeller from corrosion, fouling, and abrasion, which can extend their service life and reduce maintenance costs.

Challenges on the Horizon

However, applying low friction coatings on a ship is not a simple task. It requires careful selection of the coating material, method, and provider, as well as proper preparation of the surface and quality control of the coating process. Some of the challenges and considerations involved are:

  • Compatibility: Selecting the right coating and ensuring it’s compatible with the vessel’s hull material can be a complex process. The coating material should be compatible with the substrate material and the operating conditions of the ship. For example, some coatings may not adhere well to certain metals or plastics, or may degrade under high temperatures or pressures.
  • Application: The application of these coatings must be precise to achieve optimal results. Incorrect application can lead to performance issues and cost inefficiencies. The coating method should be suitable for the geometry and size of the surface to be coated. For example, some methods may require special equipment or facilities, or may not be able to coat complex shapes or large areas.

Low friction coating applied on the whole large surface of the hull

Moreover, the coating provider should have sufficient experience and expertise in applying low friction coatings on ships. For example, some providers may not have adequate certification or quality assurance systems, or may not follow the best practices or standards for coating application.

The surface preparation should ensure that the surface is clean, dry, smooth, and free of defects before applying the coating. For example, some surfaces may require sandblasting, degreasing, priming, or masking to achieve optimal adhesion and performance of the coating.

The quality control should monitor and verify that the coating process is done correctly and that the coating meets the specifications and requirements. For example, some quality control measures may include visual inspection, thickness measurement, adhesion test, hardness test, or friction test.

  • Maintenance: Maintaining the coating’s effectiveness over time requires proper care and periodic inspections.
  • Environmental Considerations: Some coating materials may have environmental implications, so it’s crucial to balance the benefits of reduced fuel consumption with potential environmental impacts.

Technology on the Market

To address these challenges, several types of low-friction coatings are available:

  • Silicone-Based Coatings: These coatings offer excellent hydrophobic properties, reducing friction with the water and improving fuel efficiency.
  • Fluoropolymer-Based Coatings: Known for their durability and low friction, these coatings provide long-term benefits.
  • Biocide-Free Coatings: To address environmental concerns, biocide-free coatings are emerging as a sustainable option.
  • Self-Polishing Coatings: These coatings gradually release a layer of bioactive material, maintaining low friction throughout the vessel’s operation.
  • Hybrid Coatings: Combining different technologies, hybrid coatings aim to provide an optimal balance of performance and environmental friendliness.

What Marine Engineers Need to Do

Marine engineers play a pivotal role in the successful implementation and maintenance of low-friction coatings:

  • Material Assessment: Evaluate the vessel’s hull material and operational conditions to determine the most suitable type of low-friction coating.
  • Supplier Selection: Collaborate with reputable coating suppliers to select the appropriate product, ensuring compatibility and environmental considerations are addressed.
  • Application Oversight: Oversee the precise application of the coating, ensuring it adheres to manufacturer guidelines for maximum effectiveness.
  • Performance Monitoring: Implement a monitoring system to track the coating’s performance over time. Regular inspections can help detect wear and tear, ensuring ongoing compliance with EEXI standards.
  • Environmental Responsibility: Consider the environmental impact of the chosen coating and implement measures to mitigate any potential harm.
  • Documentation: Maintain detailed records of the coating application, performance assessments, and any maintenance activities for compliance verification.

In conclusion, applying low friction coatings on a ship requires a lot of planning, coordination, and supervision from vessel marine engineers. They have to select the right coating material, method, and provider for their ship’s needs and budget. They have to oversee the surface preparation and quality control of the coating process. They have to ensure that the coating is applied in accordance with the relevant regulations and standards. And they have to evaluate the performance and benefits of the coating after its application.

Low-friction coatings are not just a means to EEXI compliance; they represent a commitment to reducing the environmental footprint of the maritime industry. Marine engineers, equipped with the right technology and knowledge, can help vessels sail more efficiently and sustainably. With careful planning, selection, and oversight, low-friction coatings can be a powerful tool in navigating the seas of energy efficiency and environmental responsibility.

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!

Source and Bibliography:

  • EEXI | Energy Efficiency Existing Ship Index – DNV

  • EEXI and CII – ship carbon intensity and rating system – IMO

  • An Introduction To Low Friction Coatings – Ws2coating:

  • Things About Low Friction Coatings That You Never Knew

Harnessing Engine Power Limiter (EPL) for EEXI Compliance: A Marine Engineer’s Guide

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In the ever-evolving seascape of maritime regulations, the Energy Efficiency Existing Ship Index (EEXI) stands as a guiding star towards a more sustainable future. One of the critical tools in achieving EEXI compliance is the Engine Power Limiter (EPL).  In this article, we’ll dive into the significance of EPL, the challenges it poses, the available technology, and what marine engineers need to do to navigate these waters successfully.

The Essence of EPL

The Engine Power Limiter (EPL) is an integral part of a vessel’s propulsion system, designed to regulate engine power to meet the EEXI requirements. Its primary function is to limit the maximum engine power output to ensure compliance with the defined energy efficiency thresholds, ultimately reducing greenhouse gas emissions.

What is EPL and how does it work?

EPL is a system that limits the maximum engine power output in normal operating conditions, by adjusting the fuel index (the ratio between fuel flow and engine speed) with the aid of a fuel index limiter, a simple device on the ship’s engine control system. The fuel index limiter can be either mechanical or electronic, depending on the type of engine and control system.

Engine Power Limiter Source and Credit: MAN Energy Solutions

The EPL system can be overridden in emergency situations that require the use of additional power (reserve power), such as avoiding collision, maneuvering in adverse weather or responding to distress signals. The override function is activated by a switch on the bridge or in the engine room, and it triggers an alarm and a log record for reporting purposes.

The EPL system can be designed to limit either the actual engine power output or the shaft power output. The former option is suitable for ships with direct drive propulsion systems, while the latter option is suitable for ships with shaft generators or other devices that affect the power transmission from the engine to the propeller.

The level of power limitation is determined by the EEXI reduction factor, which depends on the ship type, size and age. The reduction factor ranges from 5% to 30%, meaning that the ship’s engine power must be reduced by that percentage from its original maximum continuous rating (MCR). For example, a bulk carrier built in 2010 with an MCR of 10 MW must limit its engine power to 7 MW (30% reduction) to comply with the EEXI.

Challenges on the Horizon

The main benefit of EPL is that it is a simple and cost-effective solution to achieve EEXI compliance, without requiring major modifications to the ship’s hull or propulsion system. EPL can be easily installed and retrofitted on existing ships, and it does not affect the engine’s operation under normal conditions (unless the power limit is reached).

Another benefit of EPL is that it reduces the ship’s fuel consumption and GHG emissions proportionally to the power reduction. By limiting the engine power, the ship’s speed is also reduced, which leads to lower resistance and propulsive power demand. According to some studies, a 10% decrease in speed can result in almost 30% reduction in fuel consumption and emissions.

However, implementing EPL systems presents a unique set of challenges:

  • Engineering Complexity: Installing EPL systems can be technically complex, as they must be seamlessly integrated into the existing engine control systems.

  • Data Precision: Accurate measurement and control of engine power are critical. Any discrepancies or inaccuracies in measurement could lead to non-compliance.

  • Synchronization: Coordinating engine power with vessel speed and operational demands requires precise synchronization to avoid any adverse effects on vessel performance. EPL compromise the ship’s performance, safety and operability in certain situations that require high power or speed, such as heavy weather conditions, strong currents or tides, congested waterways or ports, or contractual obligations. Therefore, EPL should be used with caution and discretion, and always considering the prevailing circumstances and risks.

  • Regulatory Adherence: Ensuring that the EPL system meets EEXI regulatory standards is essential, and this may require constant monitoring and adjustments. EPL it may not be sufficient or optimal for all ships or routes. Depending on the ship’s design characteristics, operational profile and trade pattern, other solutions may be more effective or efficient to improve the ship’s energy efficiency and reduce its emissions. For example, some ships may benefit more from hull optimization, propeller retrofitting, waste heat recovery or alternative fuels.

Technology on the Market

Several manufacturers and suppliers have developed and offered different products and solutions for EPL implementation. Some examples are:

  • Kongsberg Maritime: The company provides a software functionality called EPL upgrade for its AutoChief 600 (and AutoChief C20) remote propulsion control systems with digital governor systems (DGS). The feature enables a vessel to limit its engine power when the pre-set value is reached.

    Engine Power Limiter by Wartsila

  • Lloyd’s Register: The company has issued guidance notes for class approval of EPL and shaft power limitation (SHaPoLi) equipment, which include the requirements and procedures for the design, installation, testing and certification of such systems.

    Engine Power Limiter by MAN

  • DNV: The company offers an advisory service called EEXI vibration pre-check, which assesses the potential impact of EPL on the engine’s vibration and torsional stress levels, and provides recommendations to avoid or mitigate any adverse effects.

What Marine Engineers Need to Do

Marine engineers play a crucial role in the implementation and operation of EPL systems. They are responsible for:

  • System Assessment: Conduct a comprehensive assessment of the vessel’s current engine and propulsion systems to determine compatibility with EPL technology.

  • Technology Selection: Collaborate with technology providers to select the most suitable EPL solution, ensuring it aligns with the vessel’s specific needs and EEXI compliance requirements.

  • Integration: Installing and testing the EPL system according to the manufacturer’s instructions and the class society’s rules and regulations, ensuring its proper functioning and integration with the existing engine control system.

  • Performance Monitoring: Operating and maintaining the EPL system in accordance with the operational manual and the best practices. Implement regular monitoring and data analysis to assess the system’s performance and make adjustments as needed to maintain compliance.

  • Training: Ensure that the vessel’s crew is trained in operating and troubleshooting the EPL system effectively.

  • Documentation: Overriding the EPL system when necessary, following the safety procedures and protocols, and documenting and justifying the reasons and duration of the override events. Maintain comprehensive records of all EPL-related activities, including installation, adjustments, and performance reports, for compliance verification.

In conclusion, EPL is a viable solution for EEXI compliance that can improve the ship’s energy efficiency and reduce its emissions by limiting its engine power. However, EPL also has some challenges and limitations that need to be carefully considered and addressed. Therefore, marine engineers should be well informed and prepared to deal with EPL systems, as they are key actors in their selection, installation, operation and maintenance. With the right measures in place, EPLs can be the key to navigating these new regulatory waters with confidence.

Navigating Green Waters: Propulsion and Engine Optimization for EEXI Compliance

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The maritime industry is at the helm of significant change as it sails toward a more sustainable future. With the Energy Efficiency Existing Ship Index (EEXI) regulation coming into effect in 2024, vessel owners and operators are tasked with optimizing propulsion systems and engines to reduce greenhouse gas emissions. If you want to read more about EEXI please follow THIS LINK.

In this article, we’ll dive into the challenges, available technology, and what marine engineers need to do to navigate this sea of change successfully.

Challenges on the Horizon

Complying with the EEXI regulation presents several challenges, primarily centered around improving energy efficiency while minimizing emissions. Some of the key challenges include:

  1. Evaluating Existing Systems: Vessel owners must assess their current propulsion and engine systems to determine their energy efficiency and EEXI compliance. This often requires complex calculations and data analysis.

  2. Investment Costs: Upgrading propulsion systems and engines can be a significant investment. Owners need to balance these costs with the long-term benefits of improved efficiency and compliance.

  3. Technology Integration: Implementing new technologies and optimizing engines can be a complex process. Ensuring these systems work seamlessly with existing onboard systems is crucial.

  4. Regulatory Compliance: Meeting EEXI requirements necessitates compliance with stringent emissions standards. Staying up to date with evolving regulations is an ongoing challenge.

Technology on the Market

To address these challenges, a range of innovative technologies and solutions are emerging in the maritime sector:

  1. Fuel-Efficient Engines: Modern, fuel-efficient engines with advanced combustion technologies and improved design are becoming more widely available.

  2. Exhaust Gas Cleaning Systems: Technologies like scrubbers and selective catalytic reduction (SCR) systems help reduce emissions from engines, aligning with EEXI standards. More about this if you follow THIS LINK.

  3. Alternative Fuels: The adoption of alternative fuels such as LNG, hydrogen, and ammonia can significantly reduce greenhouse gas emissions.

  4. Energy Recovery Systems: Systems that recover and reuse waste energy from the engine, such as waste heat recovery systems, contribute to greater efficiency.

  5. Propulsion Efficiency Solutions: Upgrading propulsion systems with modern propellers and thrusters designed for efficiency can reduce fuel consumption.

    Source and Credit: MOL

    One of the most common methods to improve the attained EEXI is to limit the engine power or shaft power of the ship. This can be done by re-setting the fuel index by limiting the fuel rack using either mechanical stop or setting the control system in combination with an approved override functionality as defined in the IMO guidelines. This method is called Engine Power Limitation (EPL) or Shaft Power Limitation (ShaPoLi). To read more about this, please follow THIS LINK.

    However, this method also poses some challenges and risks for the ship operation, such as reduced maneuverability, increased fuel consumption, increased maintenance costs, and potential safety issues.

    Therefore, ship operators need to consider other measures to optimize the propulsion and engine performance of their ships, such as installing energy saving devices, using alternative fuels, or upgrading the propulsion system. Some of the available technologies on the market that can help achieve this are:

    • FuelOpt: This is a propulsion optimization system developed by Yara Marine Technologies that provides an integrated ShaPoLi feature that complies with the EEXI framework. The system enhances vessel efficiency while minimizing the impact of engine or shaft power limitations on daily operations. FuelOpt can also reduce fuel consumption and emissions by controlling the propeller pitch and engine load in real time.
    • Rotating sails: These are vertical cylinders that rotate around their axis and use the Magnus effect to create a forward thrust. They can be installed on existing ships as an auxiliary propulsion system that can reduce fuel consumption and emissions by up to 20%. Some examples of rotating sails are Flettner rotors and Norsepower rotor sails .
    • Bulbous bow: This is a protruding bulb at the bow of a ship that modifies the water flow around the hull and reduces the drag. It can improve the hydrodynamic efficiency of a ship and reduce fuel consumption and emissions by up to 15%. However, it requires careful design and optimization for different ship types and speeds.
    • Propeller fins: These are appendages attached to the propeller blades that increase the thrust and efficiency of the propeller. They can reduce fuel consumption and emissions by up to 5%. Some examples of propeller fins are Becker Mewis Ducts and Propeller Boss Cap Fins .
    • Alternative fuels: These are fuels that have lower carbon intensity than conventional marine fuels, such as liquefied natural gas (LNG), biofuels, hydrogen, ammonia, or methanol. They can reduce greenhouse gas emissions from ships by up to 100%, depending on their production and use. However, they also require new infrastructure, storage, handling, and safety measures.
    • Propulsion systems: These are systems that convert energy into propulsive force, such as diesel engines, electric motors, gas turbines, or fuel cells. They can be upgraded or replaced with more efficient or low-carbon technologies that can reduce fuel consumption and emissions. Some examples of propulsion systems are hybrid propulsion, diesel-electric propulsion, or hydrogen fuel cell propulsion .

What Marine Engineers Need to Do

Marine engineers play a pivotal role in ensuring vessels comply with EEXI regulations and optimizing propulsion and engine systems. Here’s what they should consider:

  1. Data Analysis: Conduct detailed data analysis to determine the current energy efficiency of propulsion and engine systems. This forms the foundation for improvement strategies.

  2. Collaboration: Collaborate with naval architects, designers, and technology providers to select the most suitable propulsion and engine optimization solutions.

  3. Regular Maintenance: Implement a rigorous maintenance schedule to keep engines and propulsion systems in optimal working condition, reducing energy wastage.

  4. Training: Stay up to date with the latest technologies and best practices through continuous education and training programs.

  5. Monitoring and Reporting: Implement systems for real-time monitoring of engine and propulsion system performance. Regularly report on energy efficiency improvements and emissions reductions.

  6. Documentation: Maintain comprehensive records of all upgrades, modifications, and maintenance activities related to propulsion and engines for compliance verification.

The EEXI regulation is expected to have a significant impact on the shipping industry in 2024 and beyond. As the maritime industry charts a course towards greater sustainability, marine engineers are the navigators guiding vessels through these uncharted waters. By leveraging the available technology and adhering to best practices, marine engineers can help vessel owners and operators meet the challenges of EEXI compliance while contributing to a cleaner, greener future for the maritime world.

Ship’s Exhaust Scrubber System: An Essential Guide to Types, Operation, Maintenance, and Troubleshooting

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In the maritime industry, environmental regulations and sustainability have become critical concerns. To comply with these regulations and minimize its environmental impact, the shipping industry has turned to innovative technologies, one of which is the ship’s exhaust scrubber system. These systems help vessels reduce harmful emissions, especially sulfur oxides (SOx), and enhance air quality. In this comprehensive guide, we will dive into the different types of scrubbers, their operation modes, maintenance requirements, and troubleshooting tips.

Types of Scrubbers

    • Open Loop Scrubbers:

      These scrubbers use seawater as the scrubbing medium to remove pollutants from the exhaust gas before it is released into the atmosphere. Open loop scrubbers are one of the most common and cost-effective solutions for complying with environmental regulations, such as the International Maritime Organization’s (IMO) sulfur emissions limits.. The sulfur in the exhaust reacts with the alkaline seawater, forming sulfuric acid. The acidified seawater is then discharged back into the sea, subject to strict environmental regulations in certain regions.

    • Closed Loop Scrubbers:

      Closed loop scrubbers circulate a specific amount of water within a closed loop system. The process neutralizes the sulfuric acid formed during the scrubbing process using an alkaline substance, usually caustic soda (sodium hydroxide). This allows the scrubber to comply with stricter discharge regulations, as no acidified water is released into the ocean.

    • Hybrid Scrubbers: A hybrid scrubber system is an advanced exhaust gas cleaning system used in ships to reduce harmful emissions, particularly sulfur oxides (SOx), from the vessel’s exhaust gases. As the name suggests, a hybrid scrubber combines the features of both open loop and closed loop scrubbers, offering greater flexibility and adaptability to comply with varying environmental regulations in different regions.

Scrubber System Operation Mode

Open Loop System Operation

Here’s how open loop scrubbers work:

    • Seawater Intake: Open loop scrubbers draw in seawater from the ocean through an intake located on the ship’s hull (sea chest). This water is used as the scrubbing medium for cleaning the exhaust gases.

    • Scrubbing Process: The exhaust gas from the ship’s engines is directed through the scrubber tower. As the gases rise through the tower, they come into contact with the downward flow of seawater.

    • Acid-Base Reaction: In the scrubber tower, the sulfur dioxide (SO2) and other acidic components present in the exhaust gas react with the alkaline seawater. This reaction results in the formation of sulfuric acid (H2SO4), a water-soluble and less harmful compound compared to SO2.

    • Neutralization: As the sulfuric acid is formed, it dissolves in the seawater, causing the water to become acidified. However, the seawater’s alkaline nature naturally neutralizes the acid, reducing its overall impact on the marine environment.

    • Discharge: The now acidified seawater is discharged overboard, subject to strict environmental regulations in specific areas. The discharged water must comply with the applicable limits for pH levels and other pollutants, which are usually determined by local or international regulations.

Open loop scrubbers are popular due to their simplicity, lower installation costs, and ease of operation. However, their usage is subject to regional restrictions, as some countries and regions have banned the use of open loop scrubbers within their territorial waters due to concerns about the environmental impact of discharging acidified water into the ocean.

To address these concerns, some ship operators may opt for closed loop scrubbers or hybrid scrubber systems, which offer more flexibility and compliance with stringent regulations by treating and reusing the scrubbing water within a closed system, rather than discharging it directly into the sea.

Closed Loop System Operation

Here’s how closed loop scrubbers work:

    • Freshwater Intake: Unlike open loop scrubbers that use seawater, closed loop scrubbers use freshwater as the scrubbing medium. The freshwater is typically stored in onboard tanks.

    • Scrubbing Process: The exhaust gas from the ship’s engines is directed through the scrubber tower, where it comes into contact with the circulating freshwater.

    • Acid-Base Reaction: Similar to open loop scrubbers, the acidic components, including sulfur dioxide (SO2), in the exhaust gas react with the alkaline freshwater. This reaction results in the formation of sulfuric acid (H2SO4), just as in the open loop process.

    • Neutralization: After the scrubbing process, the acidified freshwater is collected and pumped to a neutralization unit. In this unit, an alkaline substance, usually caustic soda (sodium hydroxide – NaOH), is added to the acidified water. The alkaline substance neutralizes the sulfuric acid, transforming it into harmless salts, such as sodium sulfate (Na2SO4).

    • Recirculation: The neutralized freshwater is then re-circulated back into the scrubber tower to continue the scrubbing process. This closed-loop system ensures that no acidified water is discharged into the sea.

Closed loop scrubbers provide the advantage of reducing the environmental impact by avoiding the direct discharge of acidified water into marine ecosystems. However, they require additional infrastructure and chemical handling for the neutralization process, making them slightly more complex than open loop scrubbers.

Hybrid Scrubber System Operation

The hybrid scrubber system can operate in three different modes:

    • Open Loop Mode: In the open loop mode, the scrubber system uses seawater as the scrubbing medium, just like a traditional open loop scrubber. The exhaust gas comes into contact with the seawater, and the sulfur dioxide (SO2) in the gas reacts with the alkaline seawater to form sulfuric acid. The acidified seawater is then discharged overboard, subject to compliance with local regulations.
    • Closed Loop Mode: In the closed loop mode, the scrubber system uses freshwater as the scrubbing medium, similar to a closed loop scrubber. The exhaust gas is scrubbed with the freshwater, and the resulting acidified water is collected and pumped to a neutralization unit. In the neutralization unit, an alkaline substance, usually caustic soda (sodium hydroxide – NaOH), is added to neutralize the sulfuric acid, transforming it into harmless salts. The neutralized water is then recirculated back into the scrubber tower to continue the scrubbing process.
    • Hybrid Mode: In the hybrid mode, the scrubber system combines the features of both open loop and closed loop modes. The system can switch between using seawater and freshwater as the scrubbing medium, depending on the vessel’s location and the applicable environmental regulations.

The hybrid scrubber system provides several advantages:

    • Compliance Flexibility: The ability to operate in multiple modes allows ship operators to comply with different environmental regulations in various regions. When sailing in areas where open loop scrubbers are allowed, the system can use seawater, and when entering regions with stricter regulations, it can switch to closed loop mode.

    • Environmental Benefits: Like closed loop scrubbers, the hybrid system prevents the direct discharge of acidified water into the sea, reducing the potential environmental impact on marine ecosystems.

    • Cost-Efficiency: The hybrid scrubber system provides cost savings by enabling the use of seawater when permitted, which eliminates the need for additional infrastructure and chemicals for neutralization.

The hybrid scrubber system has gained popularity in the maritime industry as it strikes a balance between compliance with environmental regulations and cost-effective operations, making it a viable solution for shipowners aiming to reduce their environmental footprint.

Scrubber System Maintenance

    • Regular Inspections: Conduct routine inspections of the scrubber system, including the tower, nozzles, pumps, and pipes, to identify any signs of wear, corrosion, or blockages. This helps to prevent clogging, corrosion, erosion, leakage, and fouling that can affect the efficiency and reliability of the scrubber system.
    • Cleaning: Clean the nozzles and scrubber tower regularly to prevent the accumulation of deposits and ensure efficient operation. Inspection and cleaning intervals may vary depending on the type of scrubber, the quality of the scrubbing material, and the operational conditions of the vessel.
    • Replacing and replenishing the consumables and spare parts of the scrubber system, such as the scrubbing material, filters, seals, gaskets, electrodes, and catalysts. This helps to maintain the functionality and durability of the scrubber system. Replacing and replenishing intervals may depend on the availability, cost, and environmental impact of the consumables and spare parts.
    • Filter Replacement: Replace filters in closed-loop scrubbers as per the manufacturer’s recommendations to maintain water quality and optimal performance.

To optimize vessel scrubber system maintenance, it is advisable to follow the maintenance guidelines and recommendations provided by the scrubber manufacturer or supplier. Additionally, it is beneficial to adopt a proactive and preventive maintenance strategy that uses data-driven digital services to monitor, analyze, predict, and optimize the condition and performance of the scrubber system. This can help to reduce maintenance costs, increase operational efficiency, enhance environmental compliance, and extend the service life of the scrubber system.

Scrubber System Troubleshooting

The common issues and troubleshooting of the vessel scrubber system are:

    • Reduced Scrubbing Efficiency: Over time, vessel scrubber systems might experience reduced efficiency in removing pollutants. This can be due to factors such as fouling, corrosion, or malfunctioning components.
      • Solution: Regular maintenance and inspections are essential. Fouling and corrosion should be addressed promptly, and components should be cleaned or replaced as needed. Analyzing the scrubber’s performance data can also help identify underlying issues.
    • Corrosion and Leaks: Corrosion and leaks in the scrubber system can lead to environmental contamination and reduced efficiency. Inspect the system for visible leaks and pressure anomalies. Tighten connections and replace faulty components as necessary.
      • Solution: Utilize materials that are resistant to corrosion, and apply protective coatings where necessary. Regular inspection and maintenance can help catch corrosion early and prevent extensive damage.
    • Chemical Imbalance: In closed-loop scrubbers, monitor the chemical levels regularly and ensure they are within the recommended range to maintain the system’s effectiveness.
    • Alarm Indications and Error Codes: Familiarize the crew with the scrubber’s alarm system to quickly identify and address any operational issues. Scrubber systems are equipped with monitoring and control systems that generate alarms or error codes when anomalies are detected. These alarms can range from issues with pump flow rates to pH imbalances.
      • Solution: Consult the system manual and diagnostic tools to interpret error codes correctly. Address the root cause of the alarms, which might involve checking sensors, valves, or other system components.
    • Sludge Build Up: The scrubbing process generates sludge as a byproduct, which can accumulate in tanks and pipes, leading to clogs and reduced efficiency.
      • Solution: Implement a regular maintenance schedule for sludge removal. Ensuring proper waste disposal procedures and following manufacturer guidelines for sludge management are crucial.

In conclusion, the ship’s exhaust scrubber system plays a crucial role in mitigating the environmental impact of maritime operations by reducing harmful emissions. By understanding the different types of scrubbers, their operation modes, maintenance requirements, and troubleshooting techniques, shipowners and crews can ensure the efficient and compliant operation of these systems. As the industry continues to embrace sustainable practices, exhaust scrubbers will remain a vital tool in safeguarding our oceans and the environment for generations to come.

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What you need to know about Energy Efficiency Existing Ship Index (EEXI)

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In June of 2021, the IMO Marine Environmental Protection Committee (MEPC) held its 76th meeting, where they adopted resolution MEPC.328(76) containing amendments to MARPOL Annex VI concerning mandatory goal-based technical and operational measures to reduce carbon intensity of international shipping. Developed under the framework of the Initial IMO Strategy on Reduction of GHG Emissions from Ships agreed in 2018, these technical and operational amendments require ships to improve their energy efficiency in the short term and thereby reduce their greenhouse gas emissions.

From 1 January 2023 it is mandatory for all ships to calculate their attained Energy Efficiency Existing Ship Index (EEXI), to measure their energy efficiency and to initiate the collection of data for the reporting of their annual operational carbon intensity indicator (CII) and CII rating. The attained EEXI shall be calculated for each ship and for each ship which has undergone a major conversion.

The required EEXI value is determined by the ship type, the ship’s capacity and principle of propulsion and is the maximum acceptable attained EEXI value.

The amendments to MARPOL Annex VI are in force from 1 November 2022. The requirements for EEXI and CII certification came into effect on 1 January 2023. This means that the first annual reporting will be completed in 2023, with initial ratings given in 2024.

Vessels impacted by EEXI must demonstrate compliance by their next survey – annual, intermediate or renewal – for the International Air Pollution Prevention Certificate (IAPPC), or the initial survey before the ship enters service for the International Energy Efficiency Certificate (IEEC) to be issued, whichever is the first on or after 1 January 2023.

A ship’s attained EEXI indicates its energy efficiency compared to a baseline. Ships attained EEXI will then be compared to a required Energy Efficiency Existing Ship Index based on an applicable reduction factor expressed as a percentage relative to the Energy Efficiency Design Index (EEDI) baseline. It must be calculated for ships of 400 gt and above, in accordance with the different values set for ship types and size categories. The calculated attained EEXI value for each individual ship must be below the required EEXI, to ensure the ship meets a minimum energy efficiency standard.

The CII figures out the yearly reduction factor that is needed to make sure that a ship’s operational carbon intensity keeps getting better while staying within a certain rating level. The annual operational CII that was actually reached must be written down and checked against the minimum annual operational CII. This lets us figure out the operational carbon intensity grade.

The carbon intensity of a ship will be graded A, B, C, D, or E, with A being the highest. The rating indicates a performance level of major superior, minor superior, moderate, minor inferior, or inferior. The performance level will be documented in a “Statement of Compliance” that will be expanded upon in the ship’s Ship Energy Efficiency Management Plan (SEEMP).

A ship rated D for three consecutive years, or E for one year,  will have to submit a corrective action plan to show how the required index of C or above will be achieved. Administrations, port authorities and other stakeholders as appropriate, are encouraged to provide incentives to ships rated as A or B.  A ship can run on a low-carbon fuel clearly to get a higher rating than one running on fossil fuel, but there are many things a ship can do to improve its rating, for instance through measures, such as: hull cleaning to reduce drag, speed and routing optimization, installation of solar/wind auxiliary power for accommodation services, installing main engine power limiters etc.

The easiest way to get the energy efficiency index down is to reduce engine power, as vessels’ fuel consumption and emissions, respectively, increase as speed increases. The propulsion power, thus CO2 emissions, is approximately proportional to the cube of the speed. This means that reducing speed by 20% can drop the emitted CO2 by 50%. Slow steaming, therefore, is a more carbon-efficient way to transport goods. The engine power limitation systems can be bypassed, but only if required for the safe operation of the ship, for example, in harsh weather conditions.

Example of mechanical EPL developed by MAN

The Engine Power Limiter (EPL) must be overideable and will limit engine power by restricting the fuel index to a calculated set value. This restricts the total amount of fuel that can be injected into the engine and thereby limiting the power the engine can produce. For correct installation, the EPL must limit the fuel index to match the engine power for MCRlim.

The Engine Power Limitation (EPL) as such does not alter NOx critical settings or components of the engine.

The calculation of the EEXI follows the calculation of the well-known EEDI. It is based on the 2018 calculation guideline of the EEDI, with some adaptations for existing vessels. In principle, the EEXI describes the CO2 emissions per cargo ton and mile. It determines the standardized CO2 emissions related to installed engine power, transport capacity and ship speed. The EEXI is a design index, not an operational index. No measured values of past years are relevant and no on-board measurements are required; the index only refers to the design of the ship.

The emissions are calculated based on the installed power of the main engine, the corresponding specific fuel oil consumption of the main engine and of auxiliary engines (taken from the engine test bed), and a conversion factor between the fuel and the corresponding CO2 mass. The transport work is determined by capacity, which is usually the deadweight of a ship and the ship speed related to the installed power.

The calculation does not consider the maximum engine power, but for most ship types it is 75% of MCR or 83% of MCRlim (in case of an installed overideable power limitation). Specific fuel oil consumption of the main engine and ship speed are regarded for this specific power.

In conclusion, the EEXI is applied to almost all ocean going cargo and passenger ships above 400 gross tonnage. For different ship types, proper adjustments of the formula, through correction factors have been introduced to allow a suitable comparison. Several correction factors are defined to correct the installed power, such as for ice-classed ships, as well as to correct the capacity, for instance to consider structural enhancement. From a technical perspective, all ship owners and shipbuilding stakeholders must consider and assess how they will support compliance with EEXI. Depending on the vessel age and prospects, some owners and operators may even be scrapping vessels earlier than envisioned.

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