Category Archives: Electrical and Automation

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

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

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

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

Example of generator’s synchronizing equipment

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

Causes of Incorrect Phase Sequence in Marine Diesel Generators

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

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

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

Precautions and Measures to Prevent Incorrect Phase Sequence

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

Troubleshooting Incorrect Phase Sequence

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

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

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

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

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

Example of generator’s synchronizing panel

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

What is Reverse Power? 

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

Preventive Measures and Precautions

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

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

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

      Example of frequency matching

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

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

Example of a reverse power protective relay

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

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

Troubleshooting Reverse Power

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

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

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

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

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

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

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

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

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

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

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

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

Vessels’ Bridge Instrumentation: Operation, Maintenance, and Functionality Briefly Explained

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The nerve center where navigational decisions are made is the ship’s bridge. It is outfitted with a variety of sophisticated instruments that assist in the ship’s safe navigation. Understanding the operation, maintenance, and functionality of bridge instrumentation is essential for safe navigation and personnel protection. In this in-depth blog post, we will discuss the various instruments found on the bridge of a ship, their operation and maintenance, and the significance of each instrument in the navigational process.

Radars

Vessel radars are vital navigational tools that provide critical information about the surrounding environment to ensure safe navigation at sea. Radars emit radio waves and receive their reflections to provide information about the surrounding environment, including the presence of other vessels, landmasses, and navigation hazards.

Maintenance of ship’s radars is crucial for their reliable performance. Regular tasks include:

    • Cleaning the radar antenna, dome, and connections to ensure clear signal transmission and reception.
    • Verifying the power supply and connections for any faults or loose connections.
    • Calibrating the radar settings, such as gain, sea clutter, and range, to optimize target detection and reduce false echoes.

By utilizing ship’s radars effectively and maintaining them properly, seafarers can enhance situational awareness, improve navigation safety, and ensure efficient vessel operations.

Gyrocompass

A vessel gyrocompass is a navigational instrument used on ships to determine the true north reference direction. Unlike a magnetic compass, which relies on Earth’s magnetic field, a gyrocompass uses the principles of gyroscopic stability to provide accurate heading information.

The gyrocompass consists of a gyroscope, which is a spinning wheel or rotor, mounted in a gimbal system that allows it to rotate freely in all directions. The gyroscopic effect, caused by the rotor’s high-speed rotation, creates a stable axis of rotation aligned with Earth’s rotational axis.

When the vessel is stationary, the gyrocompass aligns itself with true north, indicating the vessel’s heading. As the ship moves, the gyrocompass remains unaffected by magnetic disturbances, such as variations in the Earth’s magnetic field or nearby magnetic objects, providing accurate and reliable heading information.

Routine maintenance includes:

    • checking and adjusting the gyrocompass’s sensitivity
    • inspecting the power supply, and verifying the alignment of the gyro repeaters.

Voice Data Recorder (VDR)

A vessel’s Voice Data Recorder (VDR), also known as a Voyage Data Recorder, is a crucial piece of equipment installed on ships to record and store important audio and data signals from various bridge instruments and sensors. It is designed to provide valuable information for accident investigation, analysis, and improving safety measures in the maritime industry.

As  part of maintenance:

    • Regular checks for proper recording, ensuring sufficient storage capacity, and verifying the functionality of playback systems are essential for the VDR’s effectiveness.

The data recorded by the VDR is typically stored in a protected and secure manner, and its retrieval is possible even in the event of an accident or sinking. The recorded data is often retained for a specified period, depending on regulatory requirements.

Overall, the Voice Data Recorder is a vital tool that contributes to the safety and accountability of maritime operations. It serves as a valuable source of information for accident investigations, promotes safety awareness, and helps in continuous improvement in the shipping industry.

SAT C (Satellite Communication)

Vessel SAT C, also known as SATCOM C, refers to a satellite communication system used on ships for various purposes, including ship-to-shore communication, vessel tracking, weather updates, and emergency communications. It utilizes satellites in the C-band frequency to establish reliable and global communication links.

SAT C enables communication with shore-based authorities and other vessels via satellite, providing a vital link for important messages, weather updates, and emergency communication.

As part of maintenance:

    • Regular checks of antenna integrity and alignment to ensure optimal signal reception.
    • Verification of signal strength and quality for reliable communication.
    • Configuration and updating of system parameters and software as required.

It is important to note that vessel SAT C systems operate within a regulated framework governed by international maritime satellite communication standards, ensuring interoperability and reliability across different maritime service providers.

GMDSS Console

Vessel GMDSS stands for Global Maritime Distress and Safety System. It is an internationally recognized communication system that ensures the safety and security of ships and mariners worldwide. GMDSS is regulated by the International Maritime Organization (IMO) and is mandatory for most commercial vessels and certain types of non-commercial vessels.

The Global Maritime Distress and Safety System (GMDSS) console is a central hub for communication and distress signaling, allowing seafarers to send and receive distress messages and navigational safety information.

Maintenance of vessel GMDSS equipment involves:

    • Regular checks and testing of GMDSS equipment to ensure operational readiness.
    • Updating and verifying radio licenses, certificates, and required documentation.
    • Proper training of crew members to operate GMDSS equipment effectively.
    • Regular checks for proper functioning of distress alert systems, battery capacity, and backup power sources are crucial for the GMDSS console’s reliability.

Compliance with GMDSS regulations is essential for vessels to meet safety standards and ensure effective communication during emergencies. By implementing and maintaining GMDSS equipment, vessels can significantly enhance their safety, security, and ability to respond to distress situations at sea.

GPS (Global Positioning System)

A vessel GPS (Global Positioning System) refers to the navigational system used on ships to determine their precise position, speed, and course using signals received from a network of satellites orbiting the Earth. GPS technology has revolutionized maritime navigation by providing accurate and reliable positioning information in real-time.

Maintenance of vessel GPS systems includes:

    • Regular checks for proper functioning of the GPS receiver, antenna, and associated cabling.
    • Updating GPS software and firmware to ensure compatibility with satellite systems and accuracy of position calculations.
    • Verifying the integrity of the GPS signal reception and monitoring for any signal interference or degradation.

Overall, vessel GPS plays a vital role in modern maritime navigation, providing accurate positioning, speed, and course information to seafarers.

AIS (Automatic Identification System)

Vessel AIS (Automatic Identification System) is a tracking and information system used in the maritime industry to enhance vessel safety, improve situational awareness, and facilitate efficient vessel traffic management. It is a global standard for automatic, real-time exchange of vessel information between ships and shore-based authorities.

Maintenance of vessel AIS systems includes:

    • Regular checks for proper functioning of the AIS transponder, including power supply, antenna, and connections.
    • Ensuring the accuracy and integrity of the AIS data transmitted, including vessel identification and position information.
    • Updating AIS software and firmware to ensure compliance with the latest standards and regulations.

It is important to note that vessel AIS operates on specific frequencies and has defined transmission intervals and power levels to ensure efficient and reliable data exchange

Engine Telegraph, Steering Gear, Main Engine, Thrusters Controls

The steering gear control system allows seafarers to control the vessel’s rudder, ensuring precise steering and course corrections.

The main engine control system regulates the propulsion system’s speed and direction, while the telegraph relays the commands from the bridge to the engine room.

Thrusters provide additional maneuvering capabilities to the vessel, enabling precise movements in confined areas, such as ports and narrow waterways.

Maintenance of these systems, includes but not limited to:

    • Routine checks for proper hydraulic pressure, mechanical integrity, and responsiveness of the steering gear system are essential for safe navigation.
    • Regular checks for smooth engine control operation, proper communication between the bridge and engine room, and calibration of telegraph instruments are necessary for efficient propulsion control.
    • Regular inspection and maintenance of thruster control systems, including hydraulic systems, electrical connections, and propeller condition, are crucial for optimal thruster performance.

ECDIS (Electronic Chart Display and Information System)

Vessel ECDIS (Electronic Chart Display and Information System) is an advanced electronic navigational system used on ships for chart display, route planning, and navigation assistance. ECDIS replaces traditional paper charts by providing digital chart data that is displayed on a monitor or display unit. It is designed to enhance navigational safety, improve efficiency, and aid in voyage planning and execution.

ECDIS displays electronic navigational charts, providing real-time vessel position, route planning, and information on nearby navigational hazards.

Maintenance of vessel ECDIS systems includes:

    • Regular updates of electronic chart data to ensure the most current and accurate information is available.
    • Verifying the integrity of the ECDIS equipment, including the display unit, sensors, and connectivity.
    • Training crew members on ECDIS operation, functions, and interpretation of electronic charts.

Vessel ECDIS has become a vital tool in modern maritime navigation, providing mariners with a powerful tool for safe and efficient passage planning and execution.

In conclusion, the bridge instrumentation on vessels plays a critical role in safe and efficient navigation. Understanding the operation, maintenance, and functionality of each instrument is vital for seafarers to make informed decisions and ensure the safety of the vessel, crew, and cargo. Regular maintenance, calibration checks, and adherence to best practices are necessary to optimize the performance and reliability of bridge instrumentation, allowing for smooth and secure passage at sea.

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

If you wish to learn about “Marine Electronics – Electric Circuits and Components”, please follow THIS LINK.

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

If you like my posts, please don’t forget to press Like and Share. You can also Subscribe to this blog and you will be informed every time when a new article is published. Also you can buy me a coffee by donating to this website, so I will have the fuel I need to keep producing great content! Thank you!

How the autonomous ships will affect the future of seafarers and what they can do to mitigate the impact of such development?

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The feasibility of autonomous vessels in the maritime environment is a topic of ongoing discussion and evaluation and the widespread deployment of autonomous vessels across the oceans is a complex process that depends on several factors. While autonomous ships are already being tested and implemented in various pilot projects and short-distance operations, achieving large-scale deployment will require overcoming significant challenges. Here are some key factors that influence the timeline for the deployment of autonomous vessels:

    • Technological Advancements: Autonomous vessels must navigate complex maritime environments, including varying weather conditions, congested shipping lanes, and unpredictable obstacles such as floating debris. Advanced sensor systems, including radar, lidar, and cameras, combined with robust collision avoidance algorithms, are being developed to ensure safe navigation. However, the development and refinement of autonomous ship technologies are ongoing. Continued advancements in areas such as artificial intelligence, sensor systems, communication infrastructure, and cybersecurity are crucial for ensuring the safety, reliability, and efficiency of autonomous operations. As these technologies mature, the timeline for large-scale deployment becomes more attainable.

      Technology development. Source and credit: kassproject.org

    • Regulatory Framework: In emergency situations, the absence of human presence onboard autonomous vessels raises concerns about the effectiveness of emergency response and search and rescue operations. Developing protocols for remote assistance, coordination with rescue services, and the integration of emergency systems are essential to ensure the safety of autonomous ships and their crewless operations. Establishing comprehensive regulatory frameworks specific to autonomous ships is essential before large-scale deployment can occur. These frameworks will address safety standards, cybersecurity protocols, collision avoidance, communication requirements, and the interaction between autonomous and crewed vessels. Regulatory bodies, such as the International Maritime Organization (IMO), are actively working on guidelines and regulations to ensure safe and responsible implementation.
    • Public Acceptance: The maritime environment can present challenging weather conditions, including storms, rough seas, and extreme temperatures. Autonomous vessels need to be equipped with the capability to withstand and adapt to these conditions. Design considerations, such as hull strength, stability systems, and weather forecasting capabilities, play a crucial role in ensuring the safe operation of autonomous ships. Widespread acceptance and trust from the public, shipping companies, and maritime stakeholders are critical for the large-scale deployment of autonomous vessels. Demonstrating the safety, efficiency, and environmental benefits of autonomous ships through successful pilot projects and clear communication of their advantages will help build public confidence in this technology.
    • Infrastructure and Support Services: Ensuring redundancy and fail-safe mechanisms are critical for autonomous vessels operating in harsh maritime environments. Backup systems, redundant sensors, power supply redundancy, and robust communication networks are essential to maintain the vessel’s operation and respond effectively to emergencies or system failures. The necessary infrastructure and support services, including ports, communication networks, remote monitoring systems, and maintenance facilities, need to be in place to support the deployment of autonomous ships. Upgrading existing infrastructure and developing new infrastructure to cater to the specific needs of autonomous operations will take time and investment.

      Infrastructure development. Source and credit: Port Technology International

    • Collaboration and Industry Engagement: Collaboration between industry stakeholders, technology developers, shipbuilders, regulatory bodies, and research institutions is crucial for driving the large-scale deployment of autonomous vessels. The collective efforts of these parties will shape the future of autonomous shipping, including the development of standards, protocols, and best practices.

Considering these factors, it is difficult to provide an exact timeline for large-scale deployment of autonomous vessels. However, industry experts anticipate that it could take several more years to overcome technological, regulatory, and operational challenges and achieve widespread adoption. The pace of deployment will likely vary across different regions and sectors of the maritime industry, with short-distance operations and specialized applications being early adopters, followed by longer and more complex voyages. Also, the timeline for large-scale deployment will be influenced by the successful resolution of technical, regulatory, and societal challenges, as well as the collective efforts and collaboration of industry stakeholders to ensure safe, efficient, and sustainable autonomous operations.

The rise of autonomous ships undoubtedly brings significant implications for seafarers, raising concerns about the future of their employment and roles within the maritime industry. While it is likely that the adoption of autonomous ships will reduce the demand for traditional crewed vessels, seafarers can take proactive steps to mitigate the impact of this development. Here are some considerations:

    • Adaptation and Reskilling: Seafarers should be open to acquiring new skills and adapting to emerging technologies. Upskilling and reskilling programs can help seafarers transition into roles that complement autonomous systems, such as operating and maintaining the advanced technologies onboard autonomous ships. This could involve learning about robotics, data analysis, remote monitoring, or other fields that align with the evolving needs of the industry.
    • Embrace Technological Literacy: Seafarers can benefit from gaining a strong understanding of the technologies driving autonomous ships. This includes learning about artificial intelligence, sensor systems, data analytics, and other relevant technological domains. By becoming technologically literate, seafarers can position themselves as valuable assets who can bridge the gap between the human and autonomous aspects of future maritime operations.
    • Focus on Specialized Roles: While the number of traditional seafaring positions may decline with the introduction of autonomous ships, there will still be a need for specialized roles that require human expertise. Seafarers can consider focusing on areas that complement autonomous systems, such as vessel maintenance, cybersecurity, emergency response, or supervisory roles overseeing autonomous operations. Specializing in these domains can provide seafarers with unique career opportunities in the evolving maritime landscape.
    • Diversify Skill Sets: Seafarers can explore opportunities to diversify their skill sets beyond the traditional maritime roles. They can consider careers in related fields such as maritime logistics, port operations, marine consultancy, or even transitioning to shore-based positions in maritime technology companies. Diversifying skill sets can broaden employment prospects and offer alternative pathways within the maritime sector.
    • Collaborate and Advocate: Seafarers can collaborate with industry organizations, unions, and policymakers to ensure their voices are heard during the transition to autonomous ships. By actively participating in discussions and negotiations, seafarers can advocate for fair employment practices, retraining programs, and adequate support during the industry’s transformation. Building strong networks and staying informed about industry developments is crucial to effectively navigate these changes.
    • Emphasize Soft Skills: While technology plays an integral role in the maritime industry’s future, human skills remain valuable. Seafarers can focus on developing and highlighting their soft skills, such as leadership, communication, problem-solving, and adaptability. These skills are difficult to replicate with automation and can position seafarers for roles that require human interaction, decision-making, and collaboration.

In conclusion, seafarers can take proactive steps to mitigate the impact of autonomous ships on their future employment. By adapting their skill sets, embracing technology, focusing on specialized roles, diversifying their expertise, collaborating with stakeholders, and emphasizing soft skills, seafarers can position themselves for success in the evolving maritime industry. It is crucial for industry stakeholders to support seafarers’ transition and ensure a fair and inclusive approach to the integration of autonomous ships.

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

If you wish to learn about “Electronic Circuits in Maritime Communication Systems”, please follow THIS LINK.

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

If you like my posts, please don’t forget to press Like and Share. You can also Subscribe to this blog and you will be informed every time when a new article is published. Also you can buy me a coffee by donating to this website, so I will have the fuel I need to keep producing great content! Thank you!

What do you need to know about “Visatron” oil mist detector

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Oil mist detectors are devices that are meant to protect large diesel engines of all applications against serious damage originating from crank-drive bearings or piston components overheating.

 

 

In case of “Visatron” oil mist detector, the atmosphere of the crankcase compartment is continuously drawn out by means of header pipes sampling system from each crankcase compartment and directed through an optical opacity measuring track.

The suction vacuum required is generated through a wear-free air jet pump in the device, fed with the compressed air (drive air), usually from engine control air system.

The sample flow, consisting of the drawn in atmosphere of the crankcase compartment, is guided through an optical channel for measuring turbidity (opacity). The sample flow is measured by absorption of infrared light.

Opacity percentage is used as the dimensional unit of the turbidity:

    • 100 % opacity means total absorption
    • 0% opacity means no absorption

Oil mist becomes explosive from a concentration of approx. 50 mg of atomized oil in 1 liter of air and up, which correspond to an opacity of approx. 40 %. To learn more about this, please follow this link.

The alarm level sensitivity for different models of “Visatron” oil mist detectors are as per below table:

These devices are very reliable and require minimum maintenance from the crew side.

However, there are some periodical performance test and calibration that are required in order to ensure that the device is working as intended and to ensure the best protection for your engine.

The performance test and calibration must be done when the engine is stopped and vessel is at anchor or safely moored in port.

You must be aware that during the performance test the engine is not monitored by the oil mist detector.

The performance test is done following the below steps (here there is an example for Visatron VN 93 model):

    • Open the control cover for the measuring head

    • Wait until the READY-LED is switched off (approx. 10 sec)

    • As above the following display appears.
    • Blind the light beam of the measuring track with a wooden vane or a similar object.

    • At devices VN 116/93 and VN 215/93 the damage check starts on the display damage compartment as can be seen in the above picture.
    • When the alarm level is reached the TEST-LED lights up (TEST-ALARM). To set back the TEST-ALARM touch the ENTER-RESET button for more than 1 second and TEST-LED goes off.
    • Close the control cover of the measuring head.
    • After approx. 15 seconds the device is back in the normal operation.

A live test with test vapour can be carried out at the engine stand still when vessel is at anchor or safely moored in port.

The test is done as follow:

    • Open the crankcase or, more convenient, disconnect one of the sampling pipes which leads to the oil mist detector.
    • By using a smoke detector test spray, spray a short burst of vapour into the pipe or inside crankcase collecting funnel.
    • Allow the oil mist detector to draw the vapours for minimum 20 seconds.
    • Depending of the vapour density and suction time, whether an oil mist alarm is triggered or an oil mist alarm is triggered and a search run starts on the display damage compartment (VN 215/93 model).

As a maintenance, the requirements are as follow:

  • Monthly maintenance: check the negative pressure in the measuring head (range 60 – 80 mm H2O).
      • The negative (suction) pressure must be calibrated by adjusting the pressure regulator when the engine is at a standstill.
      • Make sure engine room ventilation is in operation (pressure difference in engine room)
      • Pour water inside the U-tube manometer utilizing the bottle from the service box. Both tubes shall be filled equally to the half of the scale of the manometer and must be on the same level when the manometer is not connected to the oil mist detector.
      • Loosen nut (1) and turn setscrew (2) in clockwise direction slowly up to the stop.

      • Open safety cover (3) at the throttle (5) and manually turn the setscrew (4) in clockwise direction slowly up to the stop.
      • Make sure that compressed air is open (7 bar)
      • Connect the U-tube manometer to the oil mist detector quick connection as below and it should show 0 pressure.

      • Turn setscrew (4) in counterclockwise direction until the U-tube manometer indicates a negative pressure of 80 mm H2O
      • Close safety cover
      • Turn setscrew (2) in counterclockwise direction until the negative pressure is only 60 mm H2O

      • Tight counter nut (1)
      • Disconnect U-tube manometer.
  • Quarterly maintenance:
      • replace the sintered bronze filters in the measuring head. The filters must be replaced and not cleaned.

        • clean the infrared filter glasses in the measuring head. Use only cotton buds to clean these filter glasses as there is a risk of scratching those.

  • Six monthly maintenance ( only on devices equipped with optional siphon block): remove siphon block plug and blow clean with compressed air (max. 7 bar).
  • Annually maintenance: replace sintered bronze filter in the pressure reducer.

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:

  • Source and credit:  Schaller Automation

What you need to know about High Voltage onboard vessel

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As the size of vessels continues to grow, so does their demand for power, which means that more powerful engines and other pieces of equipment will need to be installed. The larger size and increasing need for power necessitate the use of higher voltages on board, which enables the energy to be distributed throughout the vessel in a manner that is both efficient and effective.

In marine industry, voltages below 1000 Vac (1kV) are considered low voltages, while above that are considered high voltages. Usually, onboard vessels, the typical high voltage system is of 3.3 kV; 6.6 kV and 11 kV.

Example of a main electrical network

For example, on a modern container vessel with high reefer load, the power distribution system onboard vessel consists of a main 6.6kV switchboard, main 440V switchboard and the 440V emergency switchboard. The normal operating condition of the network is as follows:

    • Both halves of the main 6.6kV switchboards will be linked, ie, the bus tie breakers will be closed, effectively forming one 6.6kV switchboard so that any of the diesel generators can feed the network.
    • The main 440V LV switchboard is fed via the No.1, No.2 and No.3 High Voltage (HV) 6,600/450V transformers. Both halves of the switchboard are again  connected via the bus tie for normal operation.
    • The circuit-breakers in the 220V feeder panel will be closed, connecting the feeder panel to the 440/225V transformers supplying 220V to the ship’s mains.

The bus tie lines provide both redundancy and supply continuity in the event of any system failures and arc detectors are provided in the circuit-breaker, cable entry and bus compartments.

Generally, the HV main switchboards are of the air insulated type and the metal clad switchboard cubicles house withdrawal type vacuum circuit-breakers. Each cubicle is divided into various compartments for power equipment (circuit breaker, bus bar and feeder) and for auxiliaries (instrumentation). The circuit-breakers are of the vacuum type with automatic shutters, same as the bus tie breaker. The operating characteristics and specifications of both breakers are the same apart from the current rating. Circuit breakers are, usually, rated at lower current and bus tie breakers are rated at higher current (usually double). All incoming and outgoing sections have facilities for earthing and short-circuiting for maintenance purposes.

Normally, the bus bars in the HV and LV switchboards are arranged as follows:

Example of bus bar arrangement

The main 6.6kV switchboard consists of several sections mounted in the starboard switchboard room:

    • Bow thruster ATR panel
    • Bow thruster starter panel
    • Feeders to 450V reefer transformers in case of containers vessels
    • Main transformers’ feeder panels
    • Main diesel generators’ panels
    • Earthed voltage transformers’ (EVT) panels
    • Bus tie and synchronising panel

The main 6.6kV generator panels are equipped with an ammeter, voltmeter, wattmeter and power factor meter.

The main 440V LV switchboard is mounted in the engine control room and consists of the following panels:

      • 440V feeder panels
      • 6,600/440V transformers’ incomer panels
      • Bus tie panel
      • 220V feeder panels
      • Group starter panels

The main 440V switchboards have a 220V feeder section which is fed from the 440V switchboard via air circuit-breakers and transformers.

The 6,600V at the 6.6kV main switchboards is transformed down to 440V via main HV transformers to feed the 440V switchboards. The transformers are located in the transformers’ rooms on the engine room or in some cases, depending on vessel configuration in one of the cargo holds. The transformers are configured in such that one is working and other one or two are on standby.

High voltage circuits are potentially more dangerous than low or medium voltage circuits. This is not only due to the increased voltage, but also the explosion risk and because, under certain circumstances, high voltage circuits can retain a lethal charge even when switched off. In addition, dangerous potentials exist some distance from the actual live high voltage conductors, the distance being determined by the conductor voltage and the dielectric strength of the insulating materials (including air) surrounding the conductor.

Example of High Voltage warning safety label

It is therefore essential that all persons who may be required to work on or operate high voltage apparatus are fully aware of the hazards and how to avoid the associated danger. Personnel carrying out high voltage isolation, earthing, maintenance and inspection should have attended a recognised high voltage safety training course. High voltage apparatus is classified as any apparatus, equipment and conductors which are normally operated at a voltage exceeding 1,000 volts.

Interlocks are arranged to prevent configurations that are not allowed which may result in damage or a safety hazard. The key interlocking system allows for safe access to high voltage equipment for maintenance and repair. It ensures that the access to high voltage parts is prohibited in all cases, where the correct switch off/down and earthing procedure of the main breaker is not performed completely or in the wrong order. A specific step by step procedure is required to gain access to the keys for the converter cubicles and filter rooms.

Earthing of the 6.6kV main switchboard’s bus bars is carried out by means of a bus bar earthing switch located on each of the measuring panels. In order to prevent closing of the earthing switch while the bus bar is still live, a key interlock system is employed which ensures that the circuit-breakers for all incoming circuits that can supply power to the bus bar must be opened and withdrawn to the test position before the bus bar earthing switch on the measuring panel can be closed.

Each of these incoming circuits are controlled by a circuit-breaker and contain a fixed earthing switch. An electrical and mechanical interlock ensures that the circuit-breaker must be opened and withdrawn to the test position before the respective earthing switch can be closed. When the earthing switch is closed, an interlock prevents that particular breaker from being moved from the withdrawn to the inserted position.

The earthing switches are fitted with key interlocks which prevent the earthing switch from being used with the breaker in position.

The circuit-breakers are also provided with key interlocks. When the breakers are opened and withdrawn, they can be locked in order to prevent the breaker being inserted and the key can be removed. The keys for the different circuit breakers are not interchangeable.

Before commencing a working procedure for disconnecting and reconnecting of a high voltage system , you must ensure that proper tools are available for the job and a Permit to Work is available, issued and signed.

Example of a HV tool kit panel arrangement

The correct working procedure of Earthing a Line and Draw Out of a HV circuit breaker is as follow:

    • Open the Circuit Breaker and turn it out to isolated position. It is not advisable to open the front door when racking in or out the circuit breaker. It is wise to keep the door closed.

    • Check for Earthing lever. Mark shows Earthing switch open. Only when circuit breaker is in isolated position it is possible to operated the Earthing switch

    • To close the Earthing switch, the lever to be turned clock wise. See yellow mark on earth switch.

    • The earth switch is closed and there is now a mechanical interlock, which prevents the circuit breaker to move back into service position.

    • As an extra security a padlock can be used to shut the earthling slot.

    • Behind the door to the LV compartment the safety key for interlock is located. With the Earthing Switch closed it is possible to push the plug down and remove the key. Before the Earthing Switch can be operated back to open position the key shall be back in position and the plug shall be lifted up.

    • The key is now released, and the nominated person in control of work activity and others, can go to Transformer Room.

    • With the circuit breaker in isolated/test position open the door to the circuit breaker. Take out the plug between the breaker and the switchboard.

    • Move and adjust the trolley to correct position in line with breaker compartment The two locking pins on the trolley shall catch the corresponding holes in the HVS and the trolley will be blocked to the switchboard.

    • Move the circuit breaker out on the the trolley.

    • Unlock the trolley and remove the trolley and breaker from the HVS

In case that for any reason, the circuit breaker can’t be removed as described above, an emergency procedure must be available onboard vessel for removing the HV circuit breaker. In this case a HV protecting equipment must be worn by the person involved in the work.

Example of high voltage protective equipment.

After the job is finished the high voltage system shall be operated back to service position, the involved engineer should make sure that the zone / room / panel are clean and free from tools and any foreign object.

The following procedure can apply:

    • Disconnect the portable earthing kit using the isolating rod.
    • Start at the work location and move towards the earthing switch in the high voltage system.
    • All signs used for work to be removed.
    • Open the earth switch in the HV system panel.
    • Depending of activity carried out, the isolating level of the HV system circuit shall be controlled.
    • The circuit breaker to be drawn in to service position.
    • The nominated person in control of work sign the permit and return it to the nominated person in control of the installation (Chief Engineer).
    • Ready for service

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!

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  • Caverion

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!

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What you need to know about steam boiler’s water level control onboard vessels

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It is imperative that the water level in a steam boiler be carefully managed in order to guarantee the production of high-quality steam in a manner that is risk-free, resource-friendly, and at the appropriate pressure.
Heat is produced by the combustion of fuel in a furnace, while waste heat from the main engine can also be used to produce steam. The heat is transferred to the water that is contained within the shell of the boiler, which subsequently evaporates to produce steam that is subjected to pressure.
In order to properly discharge steam from a boiler, there must be a particular amount of water surface area available. A certain height should also be allowed above the normal working level in order to allow the water level to rise with increasing load while still allowing sufficient area for the steam to be released without any carryover of water taking place. This should be done by allowing a certain height above the normal working level.

Example of water level sight glass arrangement. Source: chiefengineerlog.com

Because it is obvious that when steam is produced, the water in the boiler evaporates, and in order to keep the level consistent, the boiler has to receive a supply of water and it is imperative that the water be kept at the appropriate level at all times.
If the boiler is allowed to function with insufficient water, there is a possibility that severe damage may occur, and finally there is a chance of explosion.

For this reason, means of controls are required which will monitor and control the water level and detect if a low water level point is reached, and take appropriate action, like sounding an alarm, shutting down the feed water supply and shutting down the burner.

Example of boiler control panel. Source: chiefengineerlog.com

There are numerous standards that mandate the availability of two separated water gauges, which are made from a screen of tempered glass, which is typically attached to the front and sides of the water gauge glass that is attached to the steam or water drum or the boiler shell. Normally the high-pressure boilers will need water gauge glass that is made up of either flat or prismatic glass. The gauge glass device, which has withstood the test of time, is utilized on the overwhelming majority of boilers. This device is often designed to provide a visible range of water level that is both above and below the normal water level.

Example of water level gauge (sight glass) on auxiliary boiler. Source: chiefengineerlog.com

It is absolutely necessary to have a solid comprehension of what may be observed in a boiler gauge glass. Because the water surface in a steaming boiler is made up of a dense population of bubbles and has a robust horizontal circulation, it is not possible to precisely determine the height of the water within the drum. So, the gauge glass is filled with water, which does not experience current or agitation because of its location, does not have any steam bubbles within it and has a temperature that is lower than the actual water in the boiler. This indicates that the water found in the gauge glass (together with the water found in other external fittings) is of a higher density than the water found inside the boiler drum and as a consequence of this, the level gauge glass will display a level that is lower than the typical water surface level in the boiler drum.

When a boiler is operating at a high load, the vigorous circulation of the water within the boiler will generate differences in the water level at various points along the length of the boiler. There is also the chance that waves will form inside the boiler whenever there is a sudden change in the load and these waves, which can frequently be seen in the level gauge glass, are usually ignored by the water level controls.

There are three obvious applications for level monitoring sensors on a steam raising boiler, and they are as follows:

      • The purpose of the level control is to make sure that the boiler receives the appropriate quantity of water at the appropriate moment.
      • Alarm for low water level. If the water level in the boiler has decreased to or below a predetermined level, the alarm for low water level will sound, preventing the burning of fuel and ensuring that the boiler continues to function in a safe manner. In order to guarantee the user’s safety, rules and regulations require two separate low level alarms to be installed in steam boilers that are automatically controlled. In marine boilers, the burner will be “shut down and blocked” if the two low level alarms (low level and low low level) goes off, and it will be necessary to reset it manually in order to get the boiler back online.
      • Alarm for high water level. This alarm goes off if the water level gets too high, signaling to the boiler operator that they need to turn off the feed water supply.

There are different methods used to detect the water level in the marine steam boilers and these usually are:

      • floating sensors – This is a straightforward method of determining the level, where the boiler is equipped with a float of some kind, which might be in a chamber located outside the boiler, or it could be directly inside the boiler drum. As the water level in the boiler fluctuates, the float will move in an upward and downward motion.

Example of float control. Source: MirMarine

The buoyancy of the float causes it to move up and down in response to changes in the water level. The opposite end of the float rod has a magnet that rotates inside of a stainless steel cap. This magnet is located at the opposite end of the rod. The fact that the cap is made of stainless steel makes it (almost) non-magnetic and enables the lines of magnetism to travel through it without being disrupted. In its most basic manifestation, the magnetic force is responsible for the operation of the magnetic switches in the following manner:

        • The feed pump can be activated by using the switch located at the bottom.
        • The feed pump can be turned off using the switch on the top.

However, in most situations, a single switch will be sufficient to regulate the on/off status of the pump, and the second switch will be used for an alarm. Alarms for different levels can be generated with the help of the same setup. A more advanced method of providing modulating control will make use of a coil that is coiled around a yoke that is located inside the cap. As the magnet is moved up and down, there will be a change in the inductance of the coil. This change in inductance is then used to produce an analog signal to a controller, which is subsequently sent to the feed water level control valve.

      • differential pressure cells – on one side of the differential pressure cell there is always going to be a certain amount of water pressure. On the opposite side, there is a head that is adjustable in accordance with the amount of water in the boiler.

Example of differential pressure cells arrangement. Source: Fierce Electronics

An electrical level signal is generated by the measurement of a diaphragm’s deflection using one of three methods: variable capacitance, strain gauge, or inductive. These methods measure the deflection of the diaphragm in different ways.

The differential pressure cells are used in systems with water of a high quality that has been demineralized, where the conductivity of the water is extremely low, which may indicate that the conductivity and capacitance probes will not function in a dependable manner.

      • conductivity probes control – a point measurement can be obtained through the use of the conductivity principle. When the water level reaches the tip of the probe, it will cause an action to be taken by a controller that is associated with it.

Example of conductivity probe arrangement. Source: keepital.com

It’s possible that this action is to turn on or turn off a pump, open or close a valve, raise the alarm level and switch on or turn off a relay.
However, a single tip can only offer a single action, often known as a point action. Therefore, in order to turn on and off a pump at specific levels, a conductivity probe needs to have two tips attached to it. As soon as the water level drops and the tip at point “pump on” becomes visible, the pump will start operating. When the water level reaches the second tip close to point HW, the pump will be turned off because it has reached its maximum capacity.

      • capacitance probes – they consists of a conducting, cylindrical probe, which acts as the first capacitor plate. This probe is covered by a suitable dielectric material, typically PTFE. The second capacitor plate is formed by the chamber wall (in the case of a boiler, the boiler shell) together with the water contained in the chamber. Therefore, by changing the water level, the area of the second capacitor plate changes, which affects the overall capacitance of the system.

Example of capacitance probe. Source: Intempco

Onboard vessels, usually the boiler water level control is a modulating system which uses PID controllers (you can find and learn more about PID controllers, if you follow this link) .

In some cases, for measuring and control of the water level, the boiler is equipped with a differential pressure (DP) water level transmitter unit. The unit comprises a level electrode, mounted in a protection tube, and the level transmitter. The unit works by a capacitance measurement, with the electrode and protection tube forming a capacitor. If the level of the boiler water located between the two capacitor plates changes, the current flowing through the plates changes. The level transmitter produces a standard analogue output of 4-20mA, which is sent to the control system. The control system processes the signal from the DP transmitter and provides level alarms/shutdowns, and the control of the regulating feed water valve.

The boiler normally operates with two different set points for normal water level. This increases the volume available for shrink and swell during start and stop of the exhaust gas economizers. When the main engine is running and the exhaust gas economizer is in operation, the highest set point for normal water level will be active (NW2). When the main engine is stopped, then there will be a shrink in the auxiliary boiler water level, and the set point for the normal water level will switch to be at NW1.
A second independent safety device is fitted for the ‘too low water level’ shutdown function. The safety device consists of an electrode and level switch; when activated, the switch will cause the control system to shut down the burner. The electrode operates on the conductive measuring principle using the electrical conductivity of the boiler water for level signaling. When the electrode tip is submerged in the water, the imbalance of the level switch bridge circuit is positive. If the water level falls below the electrode tip, the electrode produces a negative imbalance of the bridge circuit. This causes a ‘too low water level’ shutdown signal to be generated and consequent shutdown of the burner.

The feed water is normally supplied to the boiler through the feed water automatic regulating valve, but it can also be supplied using a separate auxiliary line. The regulating valve is controlled by the level of water in the boiler, and will open and close to adjust the feed rate to maintain the correct level in the boiler. The auxiliary feed line is used if the automatic level control system is inoperative. The auxiliary feed water system requires manual control of the boiler inlet valves to maintain the correct level.

The automatic feed water valve operates on the boiler’s main feed line. The valve has a plug of parabolic form and the fluid flow direction is against the closing direction. The valve is operated by a pneumatic actuator which is mounted above the valve; the actuator (read more about this by following this link)  is controlled by a signal from the water level transmitter.

On other cases feed water supply to the boiler is handled by a single element control system, which is designed to maintain the boiler water level and provide an alarm and safety shutdown should the level not stay within set limits. A transmitter is mounted on the boiler, which sends a signal to the controller, which in turn regulates the opening of the feed water control valve.
The feed water control valve has a valve positioner for automatic operation, with
a handwheel for manual operation. The duty feed pump operates continuously and the feed control valve regulates the amount of water directed to the boiler, depending upon the current water level.

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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What you need to know about pneumatic actuators and control valves onboard vessels

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Onboard vessels the most used types of valve actuators are the pneumatic ones and they are use for a numerous numbers of applications like: feed water valves, steam valves for tank heating, steam valves for different heaters, purifier’s 3-way valve etc.

Example of steam valve pneumatic actuator. Source: chiefengineerlog.com

These are actuators are fairly cheap compared with other types, easy to adjust and easy to maintain, troubleshoot and repair. Compressed air is quite abundant, cheap and easy to obtain onboard vessel compared with hydraulic oil. Moreover, experience shown that in case of the steam valves in particular, the valve itself tend to fail before the actuator. Often, steam valve seizure due scale deposits lead to actuator failure due overload.

The working principle of the pneumatic actuator is quite simple and is adapted to the system and/or application that is used for. The below explanatory video is a very useful tool for actuator’s working principle understanding (Source: RealPars).

As you have seen above, the working principle is very simple and pneumatic force required to overcome the spring tension can enter either from above or below membrane, depending on the system fail safe requirement.  Actuated or automatic valves that revert to a pre-determined position after the actuating force is removed are referred to as “fail-safe” valves. The fail-safe mode of a pneumatic/spring valve is a function of both the actuator’s action and the valve body’s action. If the fail-safe actuator is set to fail closed then when pneumatic power is removed the actuator’s spring will push the valve to the closed position. If an actuator is set to fail open then when pneumatic power is removed the actuator’s spring will push the valve to the open position.

For example, in case boiler’s feed water system, where the actuator’s fail safe mode should be valve in open position, the pneumatic pressure should come from top of the membrane to close the valve and spring tension will open it. Thus in case of pneumatic failure, the spring will keep the valve open and there will be no starvation in the drum water pipes, which may cause serious damage to drum internal.

Another type of pneumatic actuator often used onboard vessels are the pneumatic torque actuators designed to handle most quarter turn valves.

Exploded view of an air torque actuator. Source: sbakelas.gr

The units are designed from aluminum and can be fitted either as a spring return or double acting and are used for butterfly valves.

These type of pneumatic actuators are mainly used for remote control of the heeling and ballast valves as these actuators are on/off types.

One more type of pneumatic actuator used onboard vessel is the piston type actuator. A piston actuator, like all actuators, is a device that transforms raw energy into motion. In general, the actuator is connected to a piston which is contained inside an enclosure and is mainly used onboard for safety features like ventilation fire flaps, funnel flaps, galley fire flaps etc. These actuators are on/off types and are not usually used for process control.

These are also typically mounted to the upper master and wing valve for sequenced closure during shutdown operations.

Because the pneumatic actuators are operating valves used to control flow of different fluids, these valves are known as Control Valves. So, a control valve is a valve used to control fluid flow by varying the size of the flow passage as directed by a signal from a PID controller. If you want to read and learn more about valve’s PID controller follow this link.

The below explanatory video is a very useful tool for control valve’s working principle understanding (Source: RealPars).

The control valve adjusts the flow of a fluid, which might be gas, steam, water, or chemical compounds, in order to compensate for the load disturbance and maintain the regulated process variable at a position that is as close as feasible to the point that was wanted. The control valves are perhaps the most essential component of a control loop; nonetheless, they are frequently the element that receives the least amount of attention. The control valve serves as the “muscle” of the system that regulates the process. If the eyes represent the sensors of the process variables and the brain represents the controller, then the hands represent the final element of control in the control loop. Because of this, it is the most crucial component of an automatic control system, despite the fact that it is sometimes also the least understood.

Every control valve has something called an inherent flow characteristic, which describes the connection between the “valve opening” and the flowrate under conditions of constant pressure. Please take into consideration that the term “valve opening” used in this scenario refers to the location of the valve plug in comparison to its closed position against the valve seat. It is not talking about the orifice pass region at all. The orifice pass region is also referred to as the ‘valve throat,’ and it is the point at which the passage of fluid through the valve is at its most restricted and is located between the valve stopper and the seat. There is never an exception to the rule that the relationship between flowrate and orifice pass area is always directly proportional, regardless of the characteristics of the valve. If you want to learn more about control valves characteristics, please follow this link.

Control is typically accomplished by the use of globe valves. The movement of a valve plug in respect to the port(s) placed within the valve body is how the valve controls the amount of flow that passes through it. The valve plug is connected to a valve stem, and the valve stem is linked to the actuator.
The flow rate in a line can be controlled with the use of a control valve, as demonstrated in the following image.

Example of control valve arrangement. Source: http://www.steamline.com

The “controller” is responsible for receiving the pressure signals, comparing them with the pressure drop for the desired flow, and adjusting the control valve to either increase or reduce the flow based on whether or not the actual flow matches the desired flow.
Controlling any one of the multiple process variables can be accomplished through the use of comparable arrangements and the four most typical types of regulated variables are temperature, pressure, level, and flow rate.

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 source and credit – RealPars; Engineering Concepts; TecknoMechanics

What you need to know about PID Temperature Control Valve onboard vessel

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I believe that many of you have heard about PID, Temperature Control Valve (TCV), valve controller, step up controller etc. onboard vessel during your career. I know from my experience that many of the young engineers  encounter problems to understand what exactly are those machinery items and how did they work.

So, in this post we will discuss about these equipment from operational point of view and I hope that after reading this post you will be able to understand  what exactly are those machinery items and how did they work. I am not going to go into deep calculation formulas as this kind of theory you can find it into specialized engineering manuals or through a simple internet search.

A control loop feedback mechanism is referred to as a proportional-integral-derivative controller, or PID controller for short. The PID algorithm, as its name suggests, is comprised of three fundamental coefficients: proportional, integral, and derivative, all of which can be adjusted to achieve the best possible response.

Example of PID schematic

Regarding the operation of the PID, the key concept behind this algorithm is one of “manipulating the error,” and this idea underpins the entire thing.

Example of PID schematic as the Control System

It should be obvious that the difference between the Process Variable and the Setpoint is the source of the error.

These 3 modes are used in different combinations:

      • P – Sometimes used
      • PI – Most often used
      • PID – Sometimes used
      • PD – Very rare, useful for controlling servomotors.

The proportional corrects individual occurrences of error, the integral corrects the accumulation of error over time, and the derivative corrects the difference between the error that is currently occurring and the error that occurred the last time it was examined.
The derivative will have the effect of reducing the overshoot that is produced as a result of P and I.
When there is a significant amount of error, the P and the I will cause the controller output to be pushed. Because of this controller’s responsiveness, the error can vary very quickly, which in turn causes the derivative to more aggressively counteract the P and the I.

The mode of how your PID controller controls the valve involved it is best described in the controller manual, and therefore you need to read the manual carefully before any intervention or tuning attempt of the controller.

Adjusting the control parameters of a control loop to their optimal values in order to get a desired response is what is meant by “tuning” a control loop. These control parameters include the gain/proportional band, integral gain/reset, and derivative gain/rate.

When the Proportional Gain (KP) is set too high, it will cause values to oscillate and will have a tendency to induce an offset. The Integral Gain, often known as KI, will work to cancel out the offset. A higher value of KI indicates that the Setpoint will approach the PV too quickly, and if this event occurs very quickly, it increases the likelihood that the process variable will be unstable. This situation is kept under control by the Derivative Gain KD.

Manual PID tuning is done by setting the reset time to its maximum value and the rate to zero and increasing the gain until the loop oscillates at a constant amplitude. (When the response to an error correction occurs quickly a larger gain can be used. If response is slow a relatively small gain is desirable). Then set the gain of the PID controller to half of that value and adjust the reset time so it corrects for any offset within an acceptable period. Finally, increase the rate of the PID loop until overshoot is minimized.

Onboard vessels the PID controllers are mostly used for Temperature Control Valves (TCV) in cooling and heating systems (water cooling, purifiers’ heaters, FO heaters and LO coolers etc.).

Example of a LO cooler’s PID controlled temperature control valve

These valves are suited for use in vessel’s applications and process control situations in which fluids need to be mixed or redirected in order to obtain the desired temperatures. They can also be utilized in cogeneration systems to regulate temperatures within the heat recovery loop, so ensuring that the engine is cooled appropriately and making the most of the heat recovery process.
In most cases, the actuated control valve is a component of a comprehensive system that monitors changes in temperature with the assistance of an external probe.

Example of temperature probe

The valve ports are either opened or closed by an external power source after receiving a signal from the probe, which is sent to a control panel.

Example of control panels

Common sorts of systems include those that are electric, pneumatic, or a combination of the two.

Example of electric and pneumatic actuated valves

This kind of valve requires more components in order to function properly, but it does provide a number of advantages over other kinds. To begin, they are typically far more accurate, and because of this, they are the best choice when the application in question calls for extremely exact temperature control. Second, in contrast to thermostatic valves, these systems make it possible to make a flexible adjustment to the temperature range in the event that the working conditions shift.

As mentioned above actuated valves both work equally well for applications that require mixing fluids of two different temperatures or for diverting fluids to a cooler, heat exchanger, or radiator. They can can operate in any position, allowing you to mount the valves based on what works best with the existing pipework.

It is imperative that the temperature of the engine fluids be kept under control in order to guarantee the efficiency and performance of the equipment. Failure to maintain temperature constancy can, depending on the application, contribute to poor fuel consumption, high emission output, and smoke.

The temperature of the charge air inlet has a significant impact on the performance of the engine. For the combustion process to work properly, various grades and kinds of fuel need for varying temperatures at the air input. In addition, regulating the dew point helps cut down on corrosion and improve fuel economy.

The temperature of the jacket water can have an effect on the amount of NOx emissions, the efficiency of the engine, the amount of fuel consumed, and smoke. In this application, keeping the temperature at a high enough level is essential to load acceptance; on the other hand, keeping the temperature too low might result in cold corrosion, particularly during “slow steaming.” It is possible to recover waste heat from the HT system using technology known as smart valves, which can then be used to make the system more efficient as a whole. This is an additional benefit.

When valves are used for mixing service (e.g. Auxiliary Engine’s cooling system), Port C is the cold fluid inlet port from the cooler, Port B is the hot by-pass fluid inlet, and Port A the common outlet. Port A is the temperature sensing port and will mix the hot and cold fluids in the correct proportion to produce the desired outlet temperature leaving Port A.

When valves are used for diverting services, the inlet is Port A (temperature sensing port), with Port C being connected to the cooler, and Port B connected to the cooler by-pass line.

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 – RealPars
  • Amot
  • Photo credit: Amot and chiefengineerlog.com