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Marine Hydrophore Systems Onboard Vessels: Operation, Maintenance, and Troubleshooting

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Marine hydrophore systems are essential components of a vessel’s infrastructure, responsible for maintaining the necessary water pressure for various onboard applications. These systems play a critical role in ensuring the availability of freshwater for domestic and operational use.

Example of marine hydrophore in engine room. Source and credit: Marine Insights

It consists of a hydrophore tank, one or more pumps, pressure switches, valves, gauges, and other accessories. The hydrophore tank is a pressurized reservoir that stores water and compressed air, which acts as a spring to maintain a constant pressure in the water supply system. The pumps are used to fill the tank with water and to deliver water to the user points when needed. The pressure switches are used to control the start and stop of the pumps according to the pressure in the tank. The valves are used to regulate the flow of water and air in the system. The gauges are used to monitor the pressure and level of water and air in the tank.

To ensure their correct operation, longevity, and reliability, it is crucial for marine engineers and crew members to understand how to operate, maintain, and troubleshoot marine hydrophore systems effectively.

Operation of Marine Hydrophore Systems

Marine hydrophore systems are designed to maintain consistent water pressure on vessels, ensuring a reliable supply of freshwater for various purposes. The correct operation of these systems is vital for the vessel’s functionality.

Here’s how marine hydrophore systems work:

Pump Operation

  • Marine hydrophore systems typically consist of one or more pumps, a pressure tank, and a control system.
  • The pumps draw water from the ship’s freshwater tanks and pressurize it into the pressure tank.
  • The pressure tank stores water under pressure, ready for distribution.

Pressure Regulation

  • A pressure switch controls the pumps, maintaining the desired pressure level within the pressure tank.
  • When water pressure drops below the set level (due to water consumption), the pump activates to replenish the pressure tank.

Distribution

  • The pressurized water from the tank is distributed throughout the vessel via a network of pipes and valves.
  • The system ensures a steady supply of freshwater for drinking, sanitation, firefighting, and other operational needs.

Marine engineers are responsible for operating marine hydrophore systems according to the standard procedures and regulations. They must ensure that the system is functioning properly and efficiently during voyages. Some of the tasks involved in operating marine hydrophore systems are:

  • Charging: This is the process of filling the hydrophore tank with water and compressed air to achieve the desired pressure range. To charge the system, marine engineers must follow these steps:
    • Close the outlet valve of the hydrophore tank.
    • Start the pump in manual mode and watch the level gauge on the tank.
    • Once the water level reaches about 70% of the tank capacity (some tanks have markings on the level gauge), charge the tank with compressed air using an air compressor or an air bottle.
    • Stop charging when the pressure gauge on the tank reaches about 5 bar (some tanks have markings on the pressure gauge).
    • Put the pump in auto mode and open the outlet valve of the tank.
    • Monitor and check the pump cut-in and cut-out pressures on the pressure switch.
  • Watchkeeping: This is the process of monitoring and controlling the system during operation. Marine engineers must keep a continuous watch over the system’s parameters, such as pressure, level, flow, temperature, and power consumption. They must also check for any leaks, noises, vibrations, or abnormalities in the system. They must record all relevant data and report any issues or incidents to their superiors.
  • Adjusting: This is the process of modifying or regulating some aspects of the system to optimize its performance or to adapt to changing conditions or demands. Marine engineers may need to adjust some variables in the system, such as pressure range, pump speed, valve opening, or air supply. They must use appropriate tools and methods to make these adjustments safely and accurately.

Maintenance of Marine Hydrophore Systems

Marine engineers are responsible for maintaining marine hydrophore systems according to the manufacturer’s instructions and recommendations. They must perform regular maintenance activities to prevent breakdowns or malfunctions in the system.

Some of the tasks involved in maintaining marine hydrophore systems are:

  • Cleaning: This is the process of removing dirt, dust, oil, grease, rust, or corrosion from the system’s components, such as the tank, the pump, the valves, and the pipes. Marine engineers must use suitable cleaning agents and tools to clean the system thoroughly and carefully.
  • Inspecting: This is the process of examining the system’s components for any defects, faults, or damages that may affect their function or performance. Marine engineers must use visual inspection, as well as instruments such as multimeters, calipers, or pressure testers, to check the condition and functionality of the components. They must also check the alignment, balance, and lubrication of the moving parts.
  • Lubrication and Pump Maintenance
    • Lubricate pump components as per the manufacturer’s recommendations.
    • Check the condition of pump seals and gaskets and replace them if they show signs of wear.
  • Control System Testing
    • Test the control system to ensure it functions correctly.
    • Verify that pressure switches are set to the appropriate pressure levels.
  • Alarms and Safety Measures
      • Ensure that any alarm systems associated with the hydrophore are functioning correctly.
      • Test emergency shutdown procedures in case of system malfunctions.
  • Repairing: This is the process of fixing or replacing any faulty or damaged components in the system. Marine engineers must use appropriate tools and techniques to repair the components safely and effectively. They must also test the repaired components before reinstalling them in the system.

Troubleshooting Marine Hydrophore Systems

Despite regular maintenance, issues can still arise in marine hydrophore systems. Marine engineers play a crucial role in identifying and resolving problems. Here are common troubleshooting steps:

  • Low Water Pressure
    • Check for leaks or damaged pipes in the distribution network.
    • Inspect the pressure switch settings and adjust if needed.
    • Examine the pump’s performance, looking for blockages or wear.
  • Excessive Pump Cycling
    • Ensure the pressure tank is not waterlogged, which can cause frequent pump activation.
    • Check for water hammer, a sudden surge of pressure caused by rapidly closing valves.
  • Noisy Operation
    • Investigate unusual noises, which can be a sign of loose or damaged components.
    • Inspect the pump’s impeller and bearings for damage or wear.
  • Alarm Activation
    • Address alarms promptly, such as low pressure or pump failure alarms.
    • Investigate the cause of the alarm and take appropriate action.

Role of Marine Engineers

Marine engineers play a vital role in ensuring the safe and efficient operation of marine hydrophore onboard vessels. They are involved in every stage of the system’s life cycle, from design and development to installation and commissioning, from operation and maintenance to troubleshooting and improvement. They apply their engineering knowledge and technical skills to a variety of tasks related to marine hydrophore, such as designing, developing, operating, inspecting, repairing, and improving the system. They also collaborate with other engineers, officers, and crew members to achieve their goals. In this field, marine engineers must have strong analytical, technical, and problem-solving skills, as well as excellent communication skills, as they often work in interdisciplinary teams with other professionals to ensure the smooth functioning of the system. Marine engineers’ dedication to maintaining high standards of quality and safety is fundamental to the maritime industry’s success, enabling vessels to traverse the world’s waters reliably and securely.

In conclusion, marine hydrophore systems are vital onboard vessels, providing a steady supply of freshwater for various purposes. Correct operation, regular maintenance, and effective troubleshooting are essential to ensure the system’s reliability and longevity. Marine engineers and crew members play a crucial role in ensuring the smooth functioning of these systems, contributing to the overall safety and efficiency of the vessel. By adhering to the operation and maintenance guidelines and promptly addressing any issues, the marine hydrophore system can provide a reliable source of freshwater, meeting the needs of the crew and vessel operations.

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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Source and References:

  • YouTube video 1: Virtual Guru
  • YouTube video 2: Marine engineering basics by sailor basha

Marine Fresh Water Generator Feed Water Regulating Valve: Operation, Maintenance, and Troubleshooting

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Onboard a marine vessel, one of the most critical systems is the fresh water generator, responsible for converting seawater into potable water for the crew’s daily needs. At the heart of this system lies the feed water regulating valve, an essential component that controls the flow of seawater into the fresh water generator.

Feed water regulating valve. Source and Credit: Alfa Laval

In this article, we will explore the operation, maintenance, and troubleshooting of the feed water spring-loaded regulating valve, as well as the role of onboard marine engineers in ensuring its proper functioning.

Feed water regulating valve operation

The feed water regulating valve is a crucial component of the marine fresh water generator system. Its primary function is to control the flow of feed water, which typically comes from seawater, into the evaporator.

Spring load diaphragm valve working animation. Source and credit: Chem media

The operation of this valve is finely tuned to maintain the desired pressure and flow rate, ensuring optimal conditions for the evaporator to produce fresh water through the process of distillation. The valve operates based on a preset loaded spring that monitors the system’s conditions, adjusting the flow of feed water as needed to maintain stable performance.

Its primary functions include:

  1. Regulating Flow: The valve regulates the flow of seawater, ensuring it doesn’t exceed the system’s capacity or drop below the required feed rate for optimal performance.

  2. Pressure Control: The spring-loaded mechanism allows the valve to adjust according to changes in system pressure, maintaining a steady flow regardless of variations in seawater pressure.

  3. Preventing Overload: In the event of a sudden increase in seawater pressure, the valve can close partially to prevent overloading the fresh water generator.

Feed water regulating valve maintenance

Maintenance of the feed water regulating valve is essential to ensure the longevity and efficiency of the marine fresh water generator system. Marine engineers play a pivotal role in this aspect.

Spring loaded regulating feed water valve maintenance. Source and credit: Alfa Laval

Here are some key maintenance tasks:

  • Regular Inspection: Marine engineers should conduct routine inspections of the valve to check for signs of wear, corrosion, or damage. Any issues should be addressed promptly.
  • Lubrication: Lubricating the valve components, such as the spindle and seat, ensures smooth operation and reduces friction that can lead to wear.
  • Cleaning: Over time, the valve may accumulate marine fouling or deposits. Periodic cleaning is necessary to maintain its efficiency.
  • Calibration: Calibration of the valve is essential to ensure it operates within the specified parameters. This may involve adjusting the pressure settings or flow rates as needed.
  • Replacement of Parts: As with any mechanical component, parts of the valve may need to be replaced periodically due to wear and tear.

Feed water regulating valve troubleshooting

When issues arise with the feed water regulating valve, onboard marine engineers are responsible for diagnosing and addressing the problems promptly. Some common troubleshooting steps include:

  • Pressure Fluctuations: If pressure within the system fluctuates, engineers may need to inspect for leaks, blockages, or a malfunctioning valve.
  • Inconsistent Flow: Inconsistent feed water flow can be a result of valve wear or a misalignment of components. This requires a careful examination and possible adjustment.
  • Corrosion and Fouling: Engineers should check for corrosion and fouling regularly. If detected, cleaning and potential replacement of corroded parts are necessary.
  • Valve Sticking: If the valve sticks, it may not open or close as required. This could be due to debris or wear and may necessitate cleaning or repairs.
  • Leakage: Leakage is a serious concern and may require immediate action to prevent damage to the equipment and environmental contamination.

Role of Onboard Marine Engineers

Onboard marine engineers are indispensable when it comes to the operation, maintenance, and troubleshooting of the feed water regulating valve. Their roles include:

  • Regular Inspections: Conducting routine checks and inspections to ensure the valve is in optimal working condition.
  • Maintenance Planning: Planning and executing maintenance schedules to prevent unexpected breakdowns.
  • Prompt Response: Quick response to any issues with the valve to minimize downtime and ensure a constant supply of fresh water.
  • Training: Training the crew on basic troubleshooting and maintenance procedures to ensure everyone is prepared in case of emergencies.

In conclusion, the feed water regulating valve is a critical component of marine fresh water generator systems. Proper operation, maintenance, and troubleshooting are essential to ensure a continuous and reliable supply of fresh water on board. Marine engineers play a central role in safeguarding this vital resource, ensuring the safety and comfort of the crew and the vessel’s overall performance.

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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Comprehensive Guide to Marine Freshwater Generator Maintenance and Troubleshooting: Expert Tips and Techniques

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Marine fresh water generators play a critical role in ensuring a continuous supply of clean, fresh water onboard ships and vessels.

For proper operation of fresh water generators please follow THIS LINK.

Regular maintenance and timely troubleshooting are essential to keep these systems in optimal working condition. In this article, we will explore the maintenance process and provide detailed insights into troubleshooting methods for two common types of marine freshwater generators: plate type and reverse osmosis systems.

Plate Type Freshwater Generator Maintenance

Pre-Maintenance Preparation

Before initiating the maintenance process, it is important to follow these preliminary steps:

      • Shut down the freshwater generator system and isolate it from the power source.
      • Ensure all valves and pipes are closed to prevent water leakage.
      • Use appropriate personal protective equipment (PPE) such as gloves, goggles, and masks.

Cleaning the Plate Heat Exchanger

The plate heat exchanger is a critical component of plate type freshwater generators. Regular cleaning is necessary to maintain its efficiency. Follow these steps:

      • Remove the end covers and access plates from the heat exchanger.
      • Measure the holding bolts distance from the end tip to the end plate in order to have a tightening reference.
      • Soak the plates into an mild acid base solution (e.g. Descalex, Descaling liquid etc.) and keep them soaked for few hours, as it will help to easily remove the salt scaling.
      • Use a soft brush or sponge to gently clean the plates, ensuring the removal of any fouling, scale, or corrosion.
      • Rinse the plates thoroughly with clean water to remove any residue.
      • Inspect for any signs of leakage or gasket damage. Replace damaged plates and/or gaskets if necessary. Use rubber glue if required for securing the gaskets.
      • Reassemble the heat exchanger, ensuring proper alignment and tightness of bolts.
      • Pressure test the plate assembly to ensure that there are no abnormal leaks detected.

Inspecting Valves and Pumps

Valves and pumps play crucial roles in regulating water flow. Regular inspection and maintenance are essential:

      • Check all valves for proper functioning, tightness, and freedom from leakage.
      • Lubricate valve stems and ensure smooth operation.
      • Inspect pumps for signs of wear, leaks, or abnormal noise. Replace worn-out parts if necessary.
      • Verify pump impeller clearance and adjust if required.
      • Check and re-adjust, if necessary, the feed water regulating valve.
      • Check and clean, if required the feed water nozzle.

Maintaining Filters and Strainers

Filters and strainers prevent contaminants from entering the freshwater generator system. Regular maintenance is essential:

      • Remove and clean intake filters, strainers, and mesh screens.
      • Inspect for clogs, damage, or excessive fouling.
      • Replace or clean the filters as per manufacturer guidelines.
      • Ensure proper alignment and tightness during reinstallation.

Troubleshooting Tips and Techniques

Insufficient Freshwater Production:

      • Inspect Seawater Supply:
        • Check for clogged or malfunctioning seawater intake filters, valves, or strainers.
        • Check for feed water regulating valve adjustment
        • Check the water level in the sight glass.
        • Check the system vacuum and shell temperature.
        • Check the brine ejector for proper operation.
      • Monitor Pressure Gauges: Ensure proper pressure readings within specified ranges. Low pressure may indicate a blockage or fouling in the system.

High Energy Consumption:

      • Fouled Heat Exchanger: Clean the heat exchanger plates/tubes to improve heat transfer efficiency.
      • Pump Malfunction: Check pump performance, impeller condition, and motor function. Repair or replace components as necessary.

Excessive Noise or Vibration:

      • Misaligned Components: Check alignment of pumps, motors, and other rotating elements. Realignment may be required to reduce noise and vibration.
      • Loose Mounting: Inspect mounting brackets, bolts, and fasteners. Tighten as needed to minimize vibration.

Water Quality Issues:

      • Fouled Filters: Clean or replace filters to ensure optimal filtration and maintain water quality.
      • Scaling or Fouling: If the water has a salty taste or is discolored, perform chemical cleaning or descaling procedures as recommended by the manufacturer.
      • Plate assembly leakage: Pressure test the plate assembly and re-tight as found necessary. Check for any damage gaskets and replace as found necessary.
      • Salinity sensor: Check salinity sensor, clean it and replace it as found necessary. Be aware that the sensor must be cleaned with a clean dry rag and must avoid to be touched by bare hands.
      • Brine ejector: Check the brine ejector for proper operation.

System Leakage:

      • Check Connections: Inspect all connections, valves, and fittings for leaks. Tighten or replace damaged components.
      • Gaskets and Seals: Inspect and replace worn-out gaskets and seals to prevent leaks.

Electrical Malfunctions:

      • Circuit Breakers and Fuses: Check and reset or replace tripped circuit breakers or blown fuses.
      • Control Panel: Inspect the control panel for error codes or abnormal readings. Consult the system manual for troubleshooting guidance.

Reverse Osmosis Freshwater Generator Maintenance

Pre-Maintenance Preparation

Before starting maintenance on a reverse osmosis (RO) freshwater generator, follow these preparatory steps:

      • Isolate the system from the power source and shut off the seawater supply.
      • Open the system to relieve pressure.
      • Wear appropriate PPE to protect against chemicals and ensure safety.

Cleaning the RO Membranes

The RO membranes are the heart of the reverse osmosis system and require regular maintenance to optimize performance. Perform the following steps:

      • Prepare a cleaning solution as recommended by the membrane manufacturer.
      • Flush the system with clean water to remove any loose particles.
      • Circulate the cleaning solution through the membranes for the recommended duration.
      • Rinse the system with clean water to remove residual cleaning solution.
      • Inspect the membranes for signs of fouling, scaling, or damage. Replace if necessary.

Inspecting High-Pressure Pumps

High-pressure pumps are vital for maintaining the required pressure in RO systems. Regular inspection and maintenance are crucial:

      • Check the pump’s suction and discharge valves for proper operation and tightness.
      • Inspect the pump for leaks, vibrations, and unusual noises.
      • Verify the pump’s pressure and flow rates. Adjust as per manufacturer guidelines.
      • Lubricate pump bearings if required, following the manufacturer’s instructions.

Checking Instrumentation and Controls

Proper functioning of instrumentation and controls is essential for the overall performance of the RO system. Follow these steps:

      • Inspect pressure gauges, flow meters, and control valves for accuracy and freedom from blockages.
      • Calibrate instrumentation devices if necessary.
      • Verify the performance of automatic control systems and alarms.
      • Test emergency shutdown systems to ensure their functionality.

Troubleshooting for Reverse Osmosis Systems

Marine reverse osmosis (RO) freshwater generators are prone to various issues, with membrane-related problems being one of the most common. Membranes play a crucial role in the RO process by separating salt and impurities from seawater.

Insufficient Freshwater Production

      • Check the seawater flow rate and pressure. Adjust as required.
      • Inspect and clean clogged filters or strainers.
      • Evaluate the condition of RO membranes for fouling or scaling.
      • Over time, membranes can lose their efficiency due to wear and tear. Monitor the performance of the membranes and consider replacing them if they are significantly aged or damaged.

Excessive Freshwater Salinity

      • Verify the system’s seawater flow and pressure. Adjust if needed.
      • Inspect the RO membranes for damage or fouling.
      • Review and adjust the operating parameters of the RO system, such as pressure, flow rate, and recovery rate, as per manufacturer guidelines. Optimizing these parameters can enhance the membrane’s performance in removing salt and TDS. If the salt or TDS levels remain high after adjusting the operating parameters, perform a thorough chemical cleaning of the membranes to remove any accumulated deposits that may be hindering their performance.
      • Check salinity sensor, clean it and replace it as found necessary. Be aware that the sensor must be cleaned with a clean dry rag and must avoid to be touched by bare hands.

Leakage or Water Purity Issues

      • Inspect valves, pipes, and fittings for leakage or improper sealing. Repair or replace as necessary.
      • Check for loose or damaged connections.
      • Examine gaskets and seals for wear or degradation. Replace if needed.

Poor Permeate Quality

In some cases, the quality of the produced freshwater may not meet the desired standards. Troubleshoot as follows:

      • Evaluate Feedwater Quality: Check the quality of the seawater being fed into the RO system. High levels of contaminants or unusual seawater conditions can affect the permeate quality. Address any issues with the feedwater source, such as pre-filtration or pretreatment, to improve the incoming water quality.
      • Inspect and Clean Pre-filtration Systems: Examine and clean the pre-filtration systems, including filters and strainers, to ensure they are effectively removing larger particles and contaminants before reaching the RO membranes.
      • Check Chemical Dosage: Review the dosage of chemicals, such as antiscalants or biocides, used in the RO system. Incorrect dosing or expired chemicals can impact the permeate quality. Follow the manufacturer’s recommendations for proper chemical dosage and replace expired chemicals.

Pressure Drop or Flux Decline

A sudden decrease in pressure or flux (water production rate) can indicate membrane issues. Troubleshoot using the following steps:

      • Check for Fouling or Scaling: Inspect the membranes for fouling or scaling, which can cause a pressure drop or decline in water production. Clean the membranes using appropriate cleaning procedures.
      • Examine and Adjust Pre-treatment Systems: Ensure that pre-treatment systems, such as sand filters, cartridge filters, or media filters, are functioning properly. Clean or replace them if necessary to maintain optimum flow rates and pressure.
      • Verify Pump Performance: Inspect the high-pressure pump for any issues, such as clogging, leaks, or reduced performance. Address any pump-related problems promptly.

In conclusion, regular maintenance and prompt troubleshooting are essential for the reliable operation of marine freshwater generators. By following the outlined maintenance process and using the troubleshooting techniques mentioned above, ship owners, engineers, and crew members can ensure a consistent supply of high-quality fresh water onboard vessels. Remember to consult the manufacturer’s guidelines and seek professional assistance when faced with complex issues. With proper care and attention, marine freshwater generators can deliver reliable performance and contribute to the smooth operation of maritime vessels.

If you want to learn and get more knowledge about “Marine Auxiliary Machinery – Heat Exchangers and Air Compression”, 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 “Maritime Equipment for System Maintenance”, 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!

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What you need to know about FWG’s brine/air ejector

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We all know how important engine room piece of equipment is the Fresh Water Generator (FWG), as it converse seawater into freshwater by vacuum distillation for the supply of high quality freshwater for domestic and process utilization. About this equipment I have written a previous post which can be found by following this link.

A very important part of this equipment is the brine/air ejector. Ejectors are hydro-pneumatic generators with motor fluid that utilize the transfer of mass and energy between an agent with a high energy potential (pressure) and the working fluid, which has a lower pressure.

Ejector parts

The ejectors have a disadvantage in that they produce poor yields, but they have an advantage in that they are highly reliable because there are no moving components in them.

The fundamental idea behind how an ejector accomplishes its work is to transform the potential energy stored in the pressure of high-pressure motive fluid into velocity.

After that, work is done on the suction fluid with high velocity fluid that has been released from a motive nozzle. This work takes place in the diffuser inlet as well as the suction chamber. After then, the leftover energy from the velocity is converted into pressure on the other side of the diffuser. In layman’s words, high-pressure motive fluid is utilized to raise the pressure of a fluid that is currently at a pressure that is significantly lower than the pressure of the motive fluid.

According to the laws of thermodynamics, a high velocity can be attained by adiabatically expanding the motive fluid over the converging/diverging motive nozzle, which lowers the pressure of the motive fluid relative to the pressure of the suction fluid. At the exit of the motor nozzle, the supersonic velocities that are caused by the expansion of the fluid over the nozzle are seen. The converging section of a diffuser reduces velocity as the cross-sectional area is reduced. The diffuser throat is designed to create a normal shock wave. A dramatic increase in pressure occurs as flow across the shock wave goes from supersonic, to sonic at the shock-wave, to subsonic after the shock wave. In a diffuser diverging section, cross-sectional flow area is increased and velocity is further reduced and converted to pressure.

Fluid pressures that are at or above a predetermined minimum have been designed into the system by the maker to ensure that it continues to operate in a steady manner. If the pressure of the supply of motive fluid drops below what was designed for, then a motive nozzle will let through less fluid. In the event that this occurs, the ejector is not supplied with an adequate amount of energy to compress the suction fluid to the discharge pressure that was designed for it.
It is possible for an ejector to function in an unstable manner if it is not provided with an adequate amount of energy to enable compression to its design discharge pressure. Dramatic shifts in the ejector’s operating pressure are one of the telltale signs of unstable ejector functioning.

Example of FWG’s brine/air ejector arrangement

The Brine Ejector is a device that has been developed specifically to be used with seawater in its operation. It is used for brine elimination from the lower side of the FWG shell and for creating and maintaining the necessary vacuum required for FWG to boil the water by using the jacket water temperature of 70 – 90 ºC and shell temperature of 40-60 ºC.
By forcing sea water to pass through the air/brine ejector and sea water supplied by the ejector pump to be delivered to the ejector, the combined air/brine ejector is able to produce an evaporator chamber vacuum condition. This allows the brine (concentrated seawater) and air to be ejected from the evaporator chamber.

Although ejectors are very reliable, it might happen that sometimes will underperform (poor ejection performance) due different reasons. These reasons mainly are:

    • Lower than designed motive fluid (sea water) pressure – obviously in this case there is something wrong with the sea water ejector pump and need to be investigated (fouled filter, worn impeller, damaged mechanical seal etc.)
    • Higher than designed motive fluid (sea water) pressure – outboard valve need to be checked, same as outlet piping for any obstacles. If everything is ok the motive fluid nozzle can be replaced with another nozzle designed for a higher pressure.
    • Damage of the suction chamber – same need to be opened and investigated for any abnormalities (cracks, corrosion, cavitation etc.). It might be temporary repaired, by using bronze putty or ceramic putty, if spare parts are not available.

Example of corroded suction chamber

    •  Damage of the nozzle due corrosion or foreign objects – nozzle need to be replaced.

  • Example of a motive sea water nozzle

    • Damage of the diffuser – same as suction chamber can be temporary repaired, by using bronze putty or ceramic putty, if spare parts are not available.

Example of a diffuser

As part of their maintenance,  as ejectors have no moving parts in contact with the process fluids and, as such, they are reliable and require no maintenance.

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 – GEA Group
  • Photo credit: Alfa Laval and chiefengineerlog.com

 

Steam system and its purpose explained

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Onboard vessel, in general, saturated steam is produced into the oil-fired boiler or the exhaust gas boiler. There are special type of systems, where steam is used for propulsion or electrical generation into the steam turbines. On these cases steam need to be superheated and at high pressure and steam generating systems are more complex with bigger boilers, large economizers, superheaters, large steam condensers and hotwells.

Production of superheated steam. Source and credit: The Engineer Portal T.E.P

On the majority regular vessels a normal pressure of 6.0kg/cm2, saturated steam is led from the oil-fired boiler or the exhaust gas boiler, through pipe lines connected to a common 6.0kg/cm2 steam line from which steam is distributed to consumers. The steam is produced by boiling water using fuel in oil-fired boiler or by using the energy from the main engine exhaust gases during vessel cruising or in some cases, when large diesel generators are in play, the energy of their exhaust gases, as they are fitted with economizers on their exhaust manifold as part of the heat recovery systems.

Steam has a lot of use onboard vessel, like: heating fuel, oil and sludge, heating cargo, heating water, crew accommodation heating and climatization, de-icing of sea chests, pipe’s heating through steam tracings, etc.

In the close proximity of boilers, on the the common steam line there is a branch to the pressure-controlled steam dump valve, which discharges surplus steam to the dump condenser. Here below there is an example of dump valve operating principle (onboard vessels they are pneumatically actuated valves):

Dump valve operating principle. Source and credit: Sur-Flo Meters & Controls

The correct procedure of supplying steam to the consumers is as follow:

  • Ensure that the boiler is operating correctly and that the desired steam pressure is being generated.
  • Ensure that cooling water (fresh or sea water) is open and flow is present through steam dump condenser cooling tubes. This can be checked by opening the vent valve or through a manometer port on the outlet side of the steam dump condenser.
  • Open all steam line drain valves and drain the section of steam pipe of condensate as the pipe warms up. Where drain traps are fitted, line drain valves may be left open after the pipe has warmed through, otherwise the drain valve must be closed when the pipe is warm and steam comes out from the drain valve.
  • Slowly crack open the steam valve and allow the pipe line to sufficiently warm up and expand.

Water hammer in steam lines can be an issue since it can damage the pipe system and potentially cause the steam line to fail, injuring the crew members. It is critical to drain all steam lines of condensate and to gradually supply steam to cold lines with line drain valves open. This enables for proper warming of the steam line and drainage of the condensate. Drain valves are positioned throughout the steam system, and they must be opened prior to opening the steam valve for that section of line. Drain valves for all systems are normally left open when a drain trap
is fitted, however, if a system is shut down for maintenance the drain valve should be shut as well as the steam valve after the line has been allowed to cool down. The cooling down period is required to ensure that a vacuum is not formed in the steam line by the remaining steam in the heating coil/heater condensing.

Steam traps enable condensate but not steam to flow through, allowing for more efficient use of heating steam because the latent heat of evaporation is recovered as the steam condenses. If a drain trap fails, steam can travel through, resulting in low efficiency.

Steam traps and how did they work. Source and credit: Energy Synergy
Delta Venturi steam trap. Source and credit: Piping Analysis

Auxiliary steam service drains are routed to the hotwell via the steam dump condenser and the observation tank and after that, the condensate is returned to the feed water system. Because there is a risk of contamination from hydrocarbons from oil heating services, the condensate is tested in the observation tank before being returned to the system.
The condensate from the steam dump condenser is gravity-fed to the observation tank and finally to the hotwell. In order to maintain the desired steam system pressure, the dump condenser condenses excess steam from the exhaust gas boiler. An inverted ‘U’ bend in the water output line keeps the condenser water level stable.
A three-way valve at the condenser’s drain line entrance bypasses the atmospheric condenser, allowing condensate to flow straight to the observation tank and by allowing hot condensate directly into this, the system allows the temperature of the water in the observation tank to be adjusted. The three-way valve is temperature controlled, with a set point temperature of 85 – 90 deg. C at the observation tank. When the atmospheric condenser is being serviced or is malfunctioning, the condenser bypass can also be employed.
Water travels from the observation tank to the hotwell, which has a steam heating coil to help heat the boiler feed water if necessary and the level in the hotwell is maintained either directly from the discharge line of the fresh water generator into it or indirectly from the home fresh water hydrophore system. The make-up water should ideally be distilled water from the fresh water generator.

Steam dump condenser with observation tank and hotwell

The observation tank has observation windows as well as hydrocarbon monitoring equipment. If any oil is found, an alarm will trigger, and precautions can be taken to prevent oil from being pumped into the boilers. The observation tank has a big reserve of water, and the flow from the observation tank to the hotwell is from the bottom of the observation chamber. This decreases the possibility of oil carryover to the hotwell and, as a result, to the feed pump suction. Any floating sediment or oil in any portion of the observation tank can be emptied to the sludge tank via a scum line.

If oil contamination occurs every effort must be made to avoid pumping oil into the boilers. The scum valve should be opened in order to remove oil from the surface of the observation tank and the temperature in the observation tank should be maintained in order to assist in the oil removal operation. If oil is present in the observation tank, the drains from the drain traps on all the steam services should be checked until the defective service is located and this must then be isolated for repair. After repair the drain line and drain trap from the defective service must be cleaned to remove all traces of oil. The observation tank and the oil content monitor probe must also be cleaned.

Water from the hotwell gives a positive inlet head of pressure to the pump suction for the auxiliary boiler and exhaust gas boiler feed pumps. A salinity sensor is fitted in the feed pump suction line or between steam dump condenser and observation tank (in case of sea water cooled steam dump condenser) and is linked to ECR alarm monitoring system and its purpose is to detect any salt water contamination in the system but it can be isolated if required.

Boiler’s water feed pumps

The dump condenser’s condensate outflow temperature should be sufficient to keep the observation tank at 85 – 90°C. The three-way bypass valve, as previously mentioned, permits direct passage from the drains to the observation tank.
There are two boiler feed pumps, one for the oil-fired auxiliary boiler and one for the exhaust gas boiler. Each boiler has two feed water lines, with the main feed line to each boiler having a controlled valve that is controlled by the boiler’s water level. There is a return connection from the feed pump output to the hotwell to ensure that water flows through the feed pump even when the feed control valve is closed. This line has four orifice plates to control the flow of water returning to the drain tank. If the feed control system fails, the auxiliary feed valve on each boiler provides manual control of the water level.
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What is fresh water generator and how to correctly operate it?

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The fresh water generator is an equipment installed onboard vessels which is used to produce fresh water from sea water. There are two major ways of producing fresh water onboard vessels: vacuum evaporation and reverse osmosis, of which the vacuum evaporation comprises of two types: tube type and plate type. Each system has its own pro and cons. The reverse osmosis type has the advantage that it can produce the designated amount of water even at anchorage or while vessel is drifting, but the equipment and its parts are very expensive. This system is mainly common for offshore vessels. Vacuum evaporation type is the most used onboard vessels, especially the plate type, as is reliable, efficient, easy to maintain and makes use of the energy generated by the main engine jacket cooling water system. The fresh water generator can be used for extended periods even at anchor by heating it with the main engine jacket water heater (of course the water production will be low and vessel must use more fuel in the boiler).

Vacuum evaporation plate type fresh water generator

The combined brine/air ejector, which is driven by the ejector pump, creates a vacuum in the system, lowering the feed water’s boiling temperature.

Brine/Air ejector

A spring-loaded regulating valve is used to introduce feed water into the fresh water generator.

Spring loaded regulating valve

Each second plate channel of the evaporator portion receives feed water.
The remaining channels are filled with hot water from the jacket cooling system, which transfers its heat to the supply water in the evaporation channels.

Fresh water generator plate arrangement

Once the feed water reaches its boiling point (which is lower than the pressure at atmospheric pressure), it undergoes partial evaporation. The vapors and brine combination enters the separator vessel, where it is separated from the vapors and extracted using the combined brine/air ejector. After passing through a demister the vapors enter every second plate channel of the condenser section.

Demister

The remaining channels are filled with sea water supplied by the combination cooling/ejector water pump, which absorbs the heat from the vapour and condenses it into fresh water.
The distillate pump extracts the produced fresh water and discharges it through a salinometer, which checks the water’s salinity. A flow meter is located at the distillate pump outflow.
The distillate from the FW generator is routed through the re-hardening filter/neutralizing unit and the silver ion type electric sterilizer before being released into the fresh water storage tanks.

To continuously check the quality of the produced fresh water, a salinometer is provided, together with an electrode unit fitted on the fresh water pump delivery side. If the salinity of the produced fresh water exceeds the chosen maximum value, the dump valve and alarm are activated to automatically dump the produced water to the bilge tank.

In conclusion, the fresh water generator consists of the following components:

  • Evaporator section which consists of a plate heat exchanger and is enclosed within the separator vessel.
  • Separator vessel which separates the brine from the vapour.
  • Condenser section which like the evaporator section consists of a plate heat exchanger which is enclosed within the separator vessel.
  • The ejector extracts brine and uncondensed gases from the separator vessel.
  • The sea water supply pump is a single-stage centrifugal pump. This pump supplies the condenser with sea water, the brine/air ejector with jet water, and feed water for evaporation.
  • The distillate pump is a single-stage centrifugal pump. The distillate pump extracts the produced fresh water from the condenser and pumps the water to the fresh water tank.
  • The salinometer continuously checks the salinity of the produced water. The alarm set point is adjustable. The salinometer control panel is located at the fresh water generator side with LCD indicators ranging from 0.5 – 20ppm. The panel also contains a 10ppm test function and control buttons to set the alarm point.

The operating procedures for fresh water generator is described in the video below for a better understanding:

Source and credit: JJ AbelTasman
Reverse Osmosis. Source and credit: SA WaterCorp

It is very important that you do not operate the plant in polluted water. Fresh water must not be
produced from polluted water, as the produced water will be unsuitable for human consumption. It is advisable and safe to start fresh water generator when the vessel is at least 20 nm from the shoreline.

Chemical treatment is added to the sea water feed in order to minimize foaming and restrict the formation of salt scale in the FW generator. It is essential that the correct dosage of chemical is used and frequent checks must be made on the dosing unit to ensure that the correct treatment is being applied.

The condensate produced in the FW generator is pumped to the storage tanks by the distillate pump. The distilled water may be pumped to the drain tank directly (for boiler feed water use), or it may be pumped to the fresh water tanks for domestic use throughout the ship.

Alfa Laval developed the new AQUA Blue S-type which maximizes energy efficiency and capacity-to-footprint ratio by making use of the vessel’s existing seawater cooling system pumps. This cuts electrical power needs by 70% compared to conventional freshwater generators, and it shrinks the already small AQUA Blue footprint by up to 15%. Because it makes use of the vessel’s seawater cooling system pumps, it employs a smaller ejector and a smaller, separately installed ejector pump. Likewise, the pipework can be both shorter and smaller in diameter.

Source and credit: Alfa Laval

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