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

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.

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Source and References:

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

Centrifugal Pump Casing Repair Onboard Vessels: A Comprehensive Guide

Centrifugal pumps are critical components on board vessels, responsible for various fluid-handling tasks such as cooling, ballasting, and transferring liquids. They are simple and reliable machines that operate on the principle of converting mechanical energy to kinetic energy and then to pressure energy.

However, like any other machinery, they are subject to wear and tear and may require maintenance and repair from time to time. One of the common problems that affect centrifugal pumps is the damage or erosion of the pump casing.

Example of centrifugal pump casing

The pump casing is the stationary part of the pump that encloses the impeller and directs the flow of the fluid. It also converts the kinetic energy of the fluid to pressure energy. The pump casing can be damaged by various factors, such as corrosion, cavitation, abrasion, erosion, fatigue, or impact. These factors can cause cracks, holes, dents, or thinning of the casing wall, which can reduce the efficiency and performance of the pump and lead to leakage, vibration, noise, or even failure.

To mitigate these risks, it’s essential for maritime professionals to understand the process of centrifugal pump casing repair and its feasibility onboard vessels. In this comprehensive guide, we will explore whether it is possible to conduct centrifugal pump casing repair onboard, the equipment and materials required, the skills needed from the crew, and the operational precautions to take after the repair.

Is Onboard Centrifugal Pump Casing Repair Feasible?

Repairing centrifugal pump casings onboard vessels is not only possible but often necessary to maintain the vessel’s operational efficiency and safety.

Repairing the pump casing is an important task that should be done as soon as possible to prevent further deterioration and ensure the safety and reliability of the pump. Repairing the pump casing onboard vessels can be challenging due to the limited space, resources, and time available. Therefore, it is essential to have a proper plan and procedure for carrying out this task effectively and efficiently.

However, it’s important to assess the extent of the damage before deciding whether a repair can be carried out at sea or if the pump should be taken to a shore-based facility for more extensive repairs.

Feasibility Factors:

  • Extent of Damage: Minor casing damage, such as small cracks or corrosion, can typically be repaired onboard. Extensive damage may require specialized equipment and expertise available ashore.

  • Availability of Equipment and Materials: Vessels need to be equipped with the necessary tools and materials to perform casing repairs effectively. Having a well-stocked spare parts inventory is crucial.

  • Crew Skills: The onboard crew should have the required knowledge and skills to perform casing repairs safely and effectively.

  • Operational Considerations: It’s essential to consider the vessel’s operational needs and downtime constraints when deciding whether to repair the casing onboard.

How to Repair a Centrifugal Pump Casing Onboard

Repairing a centrifugal pump casing onboard a vessel involves a series of steps and requires specific equipment and materials:

  • Safety Precautions: Before starting any repair work, ensure the pump is shut down, and the associated systems are depressurized to prevent accidents. Isolate the pump from the system by closing the suction and discharge valves and locking them with chains. Switch off and lock the electrical supply to the pump and attach a warning notice. Drain the pump by opening the drain valves and cracking open the flange joints carefully.

  • Pump removal: Remove the pump from its location by using a chain block or a crane and place it on a suitable workbench or platform. Remove any external fittings or accessories that may interfere with the repair work.

  • Pump dismantling: Dismantle the pump by following the manufacturer’s instructions or using a general procedure. Remove the impeller, shaft, bearings, seals, sleeves, rings, etc. from the casing and inspect them for any damage or wear. Clean them thoroughly and store them safely for reassembly.

    Example of centrifugal pump sectional view after dismantling

  • Inspection: Carefully inspect the casing to assess the damage’s extent and location. Common issues include cracks, corrosion, and erosion. Measure the thickness of the casing wall using a caliper or a thickness gauge, if available, and compare it with the original specifications or acceptable limits. Mark the areas that need repair with a marker or a chalk.
  • Cleaning: Thoroughly clean the damaged area to remove any contaminants, rust, or debris. Proper cleaning ensures better adhesion of repair materials.

  • Choose a suitable repair method for the pump casing depending on the type and extent of damage, availability of materials and equipment, and skill level of crew members. The most common repair methods are welding, brazing, soldering, epoxy resin filling, metal spraying, or chrome plating. Each method has its own advantages and disadvantages in terms of cost, durability, quality, ease of application, etc. Therefore, it is important to weigh these factors carefully before selecting a repair method.
  • Preparation: If welding or brazing is chosen as a repair method, preheat the casing to a suitable temperature to avoid thermal stress or distortion. If epoxy resin or other repair material application is chosen, prepare the casing surface for repair by roughening it with abrasive tools. This helps enhance the bond between the casing and the repair material.

Materials and Equipment in case of epoxy resin:

    • Epoxy Resin: Use a high-quality epoxy resin suitable for marine applications.
    • Fiberglass Cloth: Employ fiberglass cloth or mat for reinforcement.
    • Putty Knife/Roller: These tools help apply and smooth the repair materials.
    • Safety Gear: Crew should wear appropriate protective gear, including gloves and eye protection.

Application of Epoxy Resin: Mix the epoxy resin according to the manufacturer’s instructions and apply it to the damaged area. Place fiberglass cloth over the resin and apply more resin to saturate the cloth fully.

Curing: Ensure that there are no gaps or air bubbles in the repair material and that it covers the damaged areas completely and evenly. Allow the repair to cure for the recommended time. This may vary based on the resin used and environmental conditions. Monitor temperature and humidity levels.

Sanding and Finishing: After curing, sand the repaired area to achieve a smooth finish. This may require multiple passes with progressively finer sandpaper.

Painting: Apply an appropriate marine-grade paint to protect the repaired area from corrosion and improve aesthetics.

Crew Skills Required for Onboard Repair

Performing a centrifugal pump casing repair onboard requires a skilled crew with the following expertise:

  • Mechanical Knowledge: Crew members should understand the pump’s operation, its components, and the function of the casing.

  • Composite Repair Skills: Familiarity with composite repair techniques, including surface preparation, resin application, and curing processes, is crucial.

  • Safety Awareness: Crew members must prioritize safety, including following safety procedures, wearing protective gear, and handling chemicals responsibly.

  • Problem Solving: The ability to assess damage, determine the appropriate repair method, and troubleshoot issues during the repair process is essential.

Operational Precautions After Repair

After completing the centrifugal pump casing repair onboard, it’s crucial to take specific operational precautions to ensure the pump’s continued functionality and vessel safety:

  • Testing: Conduct a comprehensive test of the pump to ensure it operates as expected. Monitor performance, pressure, and temperature closely during testing.

  • Regular Inspection: Implement a regular inspection and maintenance schedule to monitor the repaired casing and identify any signs of wear or damage.

  • Documentation: Maintain detailed records of the repair, including the materials used, repair date, and crew members involved, for future reference.

  • Training: Train crew members on the importance of proper pump operation and maintenance to prevent future issues.

In conclusion, centrifugal pump casing repair onboard vessels is feasible and often necessary to ensure the vessel’s smooth operation and safety. By following the proper procedures, having the necessary equipment and materials, and employing a skilled crew, maritime professionals can effectively repair pump casings at sea. It’s essential to prioritize safety, adhere to manufacturer guidelines, and implement regular maintenance to extend the life of the repaired pump casing and avoid costly breakdowns at sea.

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

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.

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Centrifugal Pump Overhauling: The Vital Role of Shaft Alignment and Preventing Common Issues

Centrifugal pumps play a critical role in various industrial applications, including marine vessels. They are responsible for transferring fluids by converting mechanical energy into hydraulic energy. To ensure optimal pump performance and prevent unexpected failures, periodic overhauling is essential. This article will delve into the significance of shaft alignment during pump overhauling, explore different problems that can arise if proper procedures are not followed, and provide an in-depth description of various pump parts, their importance, maintenance requirements, and potential issues caused by improper pump operation by vessel engine crews.

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Understanding Shaft Alignment and Its Importance

Proper shaft alignment is a crucial aspect of centrifugal pump overhauling. It refers to the precise positioning of the pump’s motor shaft and pump shaft, ensuring their perfect alignment. Accurate alignment enhances pump efficiency, minimizes wear and tear, reduces energy consumption, and extends the pump’s operational lifespan. Misalignment, on the other hand, leads to excessive vibration, premature component failure, and reduced pump performance.

Common Problems Arising from Improper Overhauling

    • Misalignment-induced Vibration: Incorrect shaft alignment can result in excessive vibration, leading to accelerated wear on bearings, seals, and other pump components. This vibration can also propagate throughout the system, causing damage to adjacent equipment and negatively impacting overall vessel performance.
    • Seal and Bearing Failures: When the pump’s shafts are misaligned, it puts additional stress on the mechanical seals and bearings. This increased load can cause seal leakage, premature seal failure, and excessive bearing wear, resulting in costly repairs and downtime.

Example of a pump damaged bearing

    • Reduced Efficiency and Increased Energy Consumption: Misalignment disrupts the hydraulic balance within the pump, leading to reduced efficiency and increased power consumption. Consequently, the pump operates at suboptimal levels, consuming more energy while delivering less output.

Understanding Pump Parts, Maintenance, and Measurement

    • Impeller: The impeller is a vital component that transfers energy to the fluid, inducing its movement. Proper maintenance of the impeller is essential for optimal pump performance and longevity. Some key considerations include:
      • Regular Cleaning: Impellers can accumulate debris, scale, or corrosion, which can hinder performance. Cleaning the impeller periodically helps maintain efficiency.
      • Inspection for Damage: Impellers should be inspected for signs of erosion, cavitation damage, wear, or corrosion. Damaged impellers can negatively impact pump performance and require timely repair or replacement.
      • Balancing: Balanced impellers minimize vibrations and reduce stress on pump components. Periodic balancing ensures smooth operation and prolongs the life of the impeller and other pump parts.
    • Bearings: Proper lubrication and monitoring of bearing conditions are crucial. Overheating, excessive vibration, or abnormal noise from the bearings can indicate problems. Regular greasing and replacement, if necessary, help prevent bearing failures.
    • Mechanical Seals: Mechanical seals prevent fluid leakage along the shaft. They require regular inspection for wear, proper lubrication, and replacement when damaged. Proper alignment significantly extends the life of mechanical seals.

      Example of pump mechanical seal

      Proper maintenance is crucial for the reliable operation of centrifugal pump mechanical seals. Some key considerations include:

      • Lubrication and Cooling: Mechanical seals often require a source of lubrication or cooling, such as a barrier fluid, to reduce friction and dissipate heat generated during operation.
      • Regular Inspection: Periodically inspect the mechanical seals for signs of wear, damage, or leakage. Pay attention to the condition of the seal faces, secondary sealing elements, and the presence of any fluid leakage.
      • Seal Flush and Flushing Plans: Depending on the application, a seal flush system may be required to remove solids or prevent clogging of the seal faces. Follow the recommended flushing plan provided by the pump manufacturer.
      • Seal Replacement: Mechanical seals have a limited lifespan and may require replacement when they exhibit excessive wear, damage, or leakage. Timely replacement helps avoid potential failures and ensures continued pump performance.
    • Casing and Wear Rings: Centrifugal pump casing wear rings are components designed to reduce the wear and improve the efficiency of the pump by providing a sacrificial surface that protects the casing and impeller. Here’s some information about centrifugal pump casing wear rings:
      • Wear Protection: The primary function of casing wear rings is to minimize wear between the impeller and the pump casing. They act as a sacrificial surface that absorbs the wear and prevents direct contact between the rotating impeller and the stationary casing.
      • Improved Efficiency: By reducing the clearance between the impeller and casing, wear rings help minimize internal recirculation and fluid leakage, leading to improved pump efficiency and performance.

The pump casing and wear rings should be periodically inspected for erosion, corrosion, or damage. Any issues should be promptly addressed to maintain hydraulic efficiency and prevent potential leaks.

Example of a pump casing

The clearance between the wear rings and the impeller/casing is important for optimal pump performance. The clearance should be designed to balance between minimizing wear and avoiding excessive friction. Proper clearance can be determined based on pump design specifications or manufacturer recommendations.

Problems Arising from Improper Pump Operation by Vessel Engine Crew

Cavitation: If the crew operates the pump at incorrect speeds or pressures, it can lead to cavitation. Cavitation occurs when the pressure drops below the vapor pressure of the fluid, causing the formation of vapor bubbles. The subsequent collapse of these bubbles results in pitting and erosion on the impeller and other internal components, reducing pump performance and lifespan.

Running Dry: Operating the pump without proper fluid flow (running dry) can cause excessive heat, seal damage, and accelerated wear on pump parts. Adequate training and awareness among the vessel engine crew regarding the importance of maintaining sufficient fluid levels are crucial for preventing such issues.

In conclusion, centrifugal pump overhauling plays a vital role in maintaining pump performance and preventing unexpected failures. Proper shaft alignment significantly contributes to efficient operation and longevity of the pump. Neglecting proper overhauling procedures can lead to a range of problems, including excessive vibration, seal and bearing failures, reduced efficiency, and increased energy consumption. Understanding the importance of pump parts, their maintenance requirements, and the potential issues arising from improper pump operation by vessel engine crews is crucial in ensuring the smooth and reliable operation of centrifugal pumps in marine applications.

If you want to learn and get a “Diploma in Marine Auxiliary Machinery”, 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 Auxiliary Machinery – Pumps, Fans, and Blowers”, 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 maintenance of hydraulic systems onboard vessel

Recently I have worked on a vessel where all mooring equipment was hydraulically powered and due age of the vessel we have encountered a lot of trouble with the system (pipe failure, pipe damage, hydraulic hoses and connection failure, pumps’ failures etc.). Apart from this, the vessel was equipped with hydraulically driven cargo cranes which gave us a lot of headache during cargo operation due their age, condition and lack of proper maintenance.

However, the majority of vessel engineers are not familiar with the correct techniques for maintaining hydraulic systems, which is despite the fact that improper maintenance of hydraulic systems is the leading cause of component and system failure. Two different aspects of concern make up the fundamental basis for performing appropriate maintenance on a hydraulic system. The first area is preventative maintenance, which is essential to the success of any maintenance program, regardless of whether it’s for hydraulics or any other piece of equipment for which we rely on its dependability. The second component is corrective maintenance, which, if it is not carried out according to the established protocols, can frequently result in the failure of additional hydraulic components.

As in any other occupational field, knowledge is power and every marine engineer must be proficient in understanding the basic principles of a hydraulic diagram, how is it working, the meaning of hydraulic symbols and the components application and function in the hydraulic system.

Unfortunately, most of the shipping companies don’t spend money for training their engineers in maintenance and troubleshooting of the hydraulic systems. Moreover, the schools and colleges teach their students only general stuff about hydraulic systems, hence the lack of maintenance and troubleshooting knowledge.

Troubleshooting a hydraulic system would take less time and cost less money if we concentrated on reducing the likelihood of system failure in the first place. Instead of selecting not to account for the possibility of hydraulic system failure as the usual, we routinely account for the possibility of such failure. Preventive maintenance of a hydraulic system is very basic and simple and if followed properly can eliminate most hydraulic component failure.

Here on this post I will describe the best maintenance practices for main components of hydraulic systems, practices based on my experience and knowledge which I hope that will help you to learn and understand the importance of these systems preventive maintenance.

The hydraulic reservoirs are used to store a volume of oil, dissipate heat from the fluid and remove contamination from the system. In the below video you can learn about their purpose.

As part of maintenance of the hydraulic reservoirs, I would like to emphasize that if any of the following conditions are met…

    • System has been opened for major work
    • Oil analysis states excessive contamination
    • Hydraulic pump fails

…the best best practices are as follow:

    • It is necessary to clean the region under and all around the reservoir in addition to the reservoir’s exterior.
    • Remove the oil from the reservoir using a filter pump and place it in a fresh container that has never been used to store any other kind of fluid.
    • Clean the insides of the reservoir by opening the reservoir and cleaning the reservoir with a “Lint Free” rag.
    • After that, pour clean hydraulic fluid into the reservoir, and then drain the remaining fluid from the system.

For the reservoir air breather which has been mentioned in the above video, it is not recommended that a standard screen breather be utilized in an unhealthy or hazardous environment. Because of the possibility of introducing impurities into a hydraulic system, it is recommended to utilize a filtered air breather with a value of 10 micron.

Example of a hydraulic reservoir air breather

As part of maintenance of the hydraulic reservoirs air breather, I would like to emphasize that the frequency of maintenance is preferred to be based on historical trending of oil samples rather than based on manufacturer’s recommendation.

The best practice is to remove and throw away the filter and never cleaned, washed and reused.

The hydraulic fluid filters are of a two types on a hydraulic system:

    • pressure filter which comes in collapsible and non-collapsible type and where the latter is preferred.
    • return filter which typically has a bypass, which will allow contaminated oil to bypass the filter before indicating the filter needs to be changed.

Same as hydraulic reservoirs air breather, as part of maintenance of the hydraulic filters, I would like to emphasize that the frequency of maintenance is preferred to be based on historical trending of oil samples rather than based on manufacturer’s recommendation and the best practices are as follow:

    • Utilizing a cleaning solution and a set of clean rags, thoroughly scrub the filter housing or cover.
    • Using clean hands, remove the old filter from the filter housing, then place the new filter inside the housing or screw it into place. NEVER allow your hand to touch a filter cartridge. Open the plastic bag and insert the filter without touching the filter with your hand.

With regard to the hydraulic pumps a marine engineers needs to know the type of pump they have in the system and how operates in their systems (e.g. what is the flow and pressure of the pump during a given operating cycle). Because of this information, a marine engineer is able to swiftly solve a system issue and identify potential trends in pump failure.

The pumps must be checked daily, when in service, for any abnormal noises, vibrations and overheating and if and when it is possible for  proper flow and pressure.

The best maintenance practices is to check and record flow and pressure during specific operating cycles; review graphs of pressure and flow and check for excessive fluctuation of the hydraulic system (usually the maker designate the fluctuation allowed).

It is important to note that hydraulic pumps are very sensitive to impurities and their inner working parts are mainly made of brass. Therefore, any kind of system oil contamination must be avoided as will interfere with pump working performance and lifetime.

Example of damaged hydraulic pump pistons

The hydraulic hoses are designed to to allow fluid to flow from one component to another and they are a vital part of keeping hydraulics systems moving. Any type of hydraulic hoses are required to meet stringent standards to accustom pressure points, loads, and also their position demanded. To perform heavy-duty functions, some engineering elements are assumed to confront the forces within and be flexible enough to bend or reach diverging angles.

Example of hydraulic hoses

It is simple to detect problems with your hydraulic hose assemblies if you check the hoses on a monthly basis. These problems could lead to more serious concerns in the future.  A marine engineer must ensure that fluid designed temperature and pressure are not exceeded and all system’s safety features and protections are fully operational. Do not disregard the leakages because the presence of any external leakage indicates that something is wrong. Hydraulic oil is expensive on its own, but if there is a significant leak, additional costs will be incurred due to fines from the Environmental Protection Agency as well as the expense of cleaning up the spill. The fact that a machine operator or technician could easily slip and fall on the remnants of a leaky hydraulic system is another significant cause for concern regarding the level of safety that is there. When threaded pipe couplings, valve seals, and flexible hoses burst or vibrate loose, not only does pressurized hydraulic fluid create a significant risk of fire, but so does pressurized hydraulic fluid.

Example of hydraulic hose failure

A marine engineer must learn to identify potential hazards, like cracks, abrasions in the cover, tight bends or twisting. The cover protects the reinforcements (wire or fabric) from weather and any other environmental hazards. If the wire or fabric is exposed, water and debris can adversely affect the reinforcement by either rusting the wire or, in the case of fabric, allowing water to wick into the system and get behind the coupling where it can cause damage.

Hoses are a relatively insignificant component of hydraulic equipment and machinery, as you are aware; nonetheless, if they are not properly maintained, they may be the source of some of the most significant issues as well as major injuries.

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 – Marine Online; Lunchbox Sessions; Donaldson Hydraulic; Al Sikander Parts

 

 

What you need to know about mechanical seals used onboard vessels

Within the pump, the mechanical seal is the component that acts as a barrier between the rotary components and the stationary elements.

Example of a mechanical seal

The seal needs to be able to prevent leakage at three different places.

Schematic of a simple mechanical seal

    • In the space between the faces of the seal (both rotational and fixed).
    • Between the rotating element and the shaft or sleeve of the pump.
    • Between the stationary element and the housing for the seal chamber of the pump.

All seals share these fundamental parts and functions in common with one another. The form, style, and design might be different from one manufacturer to the next depending on their purpose, but despite this, the fundamental theory behind its function and purpose has not changed at all.

Through the use of the spring, the set screw that is responsible for transmitting the torque from the shaft is connected to the rotary face. In addition to this, it ensures the positive and accurate placement of all of the rotary components.
Because of the wear on the faces, the spring is allowed to lengthen, which keeps the rotating face in contact with the stationary face. Within the parameters of the operational tolerances of the bearings, the O-ring on the shaft should be able to move freely in the axial direction. This type of play is known as axial play.

The pressure exerted by the liquid inside the seal chamber not only keeps the faces of the seal together but also creates a thin coating that acts as a lubricant between the surfaces of the faces. This lubricant is the media that was pumped out. The only components of the seal that move relative to one another are called faces, and they were chosen for their low frictional properties. If the equipment is not properly aligned or if the bearings have a loose tolerance, then other parts could be moving relative to one another.

There are different types of mechanical seals used onboard vessels and those mainly are:

    • Single, unbalanced, inside mounted mechanical seal

Example of single spring, unbalanced, inside mounted mechanical seal

    • Single, balanced, inside mounted mechanical seal

Example of single spring, balanced, inside mounted mechanical seal

    • Single, balanced, external mounted mechanical seal

Example of single, balanced, external mounted mechanical seal

The balanced type tend to be more and more present due their  numerous advantages (less heat generated, balanced seals can seal vacuum, high pressure, less energy consumed, less wear, higher speed shafts etc.). This balance is not a dynamic balance; rather, it is a relationship between the forces that tend to open the faces in a mechanical seal and the forces that tend to close the seal faces. In other words, this balance is a relationship between the two types of forces.

Cartridge mechanical seals are constructed in such a way that the rotary and elements, the springs and secondary seals, the gland, the sleeve stationary, and all of the pieces that accompany it are all included into a single, unified unit. It installs as a single unit as opposed to the many separate parts previously required.

Same like any other machineries and mechanical elements, the mechanical seals fail at some point, sometimes prematurely and there are numerous reasons why seals fail prematurely.

The source of the problem might be the pumping system, the operation of the pump, the repairer, the warehouse, or even before the seal was even delivered to the vessel. The appearance of liquid on the floor is typically the earliest warning sign of a problem.

The failure could have originated on the seal assembly line, although the manufacturers perform a static pressure and vacuum test on their final product.

If the mechanical seal fails immediately, or within moments of the pump start-up, one should investigate the events before start-up. This problem most likely occurred during the installation process, or possibly during the handling or manufacturing of the seal. If the seal breaks after only a few days, the problem could be caused by an erroneous specification of a component such as an O-ring seal. However, if the mechanical seal fails after three weeks of service, or after two or more months of use, then it need to reevaluate the operation of the system as well as its design.

The pump must be operated at, or close to it’s best efficiency point (BEP) on the pump curve.

Example of a pump Best Efficiency Point (BEP)

The pump will vibrate if it is operated away from its BEP on the curve, which might be either to the left or to the right. This causes the bearings and seal faces to become damaged, which ultimately leads to premature failure. In addition, operating the pump to the left of the BEP on the curve causes more heat to be added to the fluid, which has the potential to destroy the O-rings that are contained within the seal. In extreme circumstances, the fluid may evaporate, leaving the seal without any cooling or lubrication as it continues to run dry. This causes the seal to get damaged. In addition to the vibrations that will occur if the pump is operating to the right of the BEP on its curve, the bad pump may enter cavitation, which will almost likely result in the seal being destroyed.

Roughly half of all of the pumps that were in the shop at the moment had to be removed from operation because they were leaking, couldn’t maintain pressure, or wouldn’t pump. This is most likely due to an O-ring that is leaking.

The majority of mechanical seals have a rubber component known as an O-ring. The O-ring is responsible for regulating the mechanical seal’s performance in terms of temperature, pressure, and chemical resistance.
The O-ring is what differentiates a mechanical seal used in a pump for a fuel system from an O-ring used in a pump for a water system. It is not the ceramic face of the seal or the stainless steel face of the seal.
Depending on the nature of the chemical attack, the O-ring may swell, harden, dry and crack, soften, or even disintegrate if the pumped liquid is not chemically compatible with the O-ring.

Even though an O-ring will become more flexible as the temperature rises, exposing it to extreme heat will cause it to become more rigid, therefore should be compatible with the high temperature environment.

O-rings, particularly Buna-N (a compound made of nitrile), should be stored in a location that is not near fluorescent lighting or electric motors. These things produce ozone in the atmosphere. These elastomers deteriorate in quality as a whole when exposed to ozone.

The pumped liquid may contain suspended particulates, crystals, and silt, all of which have the potential to settle into the seal springs and impede their movement. Because they are jammed, the springs are unable to bend and keep the seal faces together while the shaft moves within the axial tolerance of the bearing.
The shaft O-ring will need to bend in order to maintain face contact if the mechanical seal is cocked or misaligned onto the shaft, or if the seal chamber face is not perpendicular to the shaft. Because of the bending, the shaft seal will rub against the shaft underneath the seal, which can cause the shaft to erode or eat away at a groove. Either the pumped fluid may leak under the O-ring, or the O-ring could dangle into the groove and pull the seal faces as the shaft moved within the bearing tolerance. Both of these scenarios are possible. This is commonly thought to be a problem with the seal, although it is actually an alignment issue.

Seal faces that are loaded with an excessive amount of spring tension might generate an excessive amount of heat. This will cause damage to the O-ring, and the seal faces may potentially shatter as a result of the temperature expansion. If the spring tension is not sufficient, the faces may leak after a short while when the softer face wears against the harder face and the spring tension entirely relaxes. This occurs when the softer face rubs against the harder face. When it comes to a lengthy seal life, the installation dimension is quite important.

Pump and motor alignment is yet, another important matter that must take into consideration when investigate the mechanical seal failure. A misaligned shaft will exert a higher load on the pump bearings which will overheat due overloading. This overheat will affect the mechanical seal O-ring which will harden in time, thus leading to its failure.

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:

  • Know and Understand Centrifugal Pumps – Larry Bachus & Angel Custodio
  • Youtube video training credit – Engineering Dots ; Mechanical Seal Engineering Pty Ltd; Paul Brimhall; 

Why the pump’s bearings fail and how to correctly lubricate them?

Failures of the pump’s bearings are the cause of pump outages and repairs nearly as frequently as failures of the pump’s mechanical seals.

Example of ball bearing failure

Centrifugal pumps often make use of both rolling element (anti-friction) bearings and sliding element (plain) bearings in their construction. Each of these two groups of bearings can be discovered in small as well as large pumps, as well as single and multiple-stage configurations. On the other hand, sliding element bearings are typically preferred over rolling element bearings for extremely big or extremely high-speed pumps.

Rolling element bearings are typically utilized in the majority of centrifugal pumps onboard vessels. This is due to the fact that the vast majority of centrifugal pumps have a horsepower rating of less than 200 (or -150 kW). Failures of rolling element bearings should therefore be avoided or reduced if possible, as this should be the primary focus of any conversation concerning the extension of pump life.
A rolling element bearing is a device that requires a high level of precision and is a feat of engineering. It is quite improbable that any other mass-produced item is machined to tolerances that are quite as stringent as these. Rolling contact surfaces and geometries are normally maintained to millionths of an inch, whereas boundary dimensions are often kept to tenths of a thousandth of an inch. Because of this obviously important factor, only a negligible amount of surface degradation can be tolerated.

In most cases, fatigue failure rather than wear is what causes a rolling element bearing to fail before its expected lifespan, provided that the working circumstances are satisfactory. The number of stress reversals and the cube of the load that is creating these stresses are the two factors that determine how long a bearing will last under optimal operating circumstances before it fails due to fatigue. As an example, if the load that is being supported by the bearing is doubled, the theoretical fatigue life will be cut in half. In addition, the potential fatigue life is cut in half if the speed is increased by a factor of two.

The friction torque that is generated by a rolling element bearing is fundamentally made up of two different parts. One of these is a function that depends on the design of the bearing as well as the load that is placed on the bearing. The other aspect is determined by the type of lubrication, the amount of lubricant used, and the speed at which the bearing rotates.

It has been discovered that the friction torque in a bearing is at its lowest when there is just enough oil of the appropriate viscosity to produce a film between the contacting surfaces of the bearing. This is just one of the many reasons why oil mist is a superior technique of lubricating. The amount of friction will increase if there is a bigger quantity of oil or if its viscosity is increased. When there is more oil present than what is necessary to keep the rolling parts apart, the friction torque will grow along with the speed.

The following are some of the tasks that are performed by a bearing lubricant:

    • To prevent sticking and provide smooth sliding between the cage and the other components of the bearing
    • To function as a lubricant for any points of contact between the races and the rolling parts in regions where there is slippage.
    • In roller bearings, to lubricate the sliding contact that exists between the rollers and the guiding parts.
    • In some instances, to dissipate the heat that has been generated in the bearing.
    • To prevent corrosion from occurring on the surfaces that have been thoroughly polished.
    • To create a barrier that is airtight and watertight against any outside elements.

Oil is the lubricant of choice for rolling element bearings because of its superior properties. Simply combining oil with soap or other thickeners that aren’t soap-based to create grease is an easy approach to get more use out of the oil and grease can be used for a variety of purposes. When making a grease, the thickener’s primary function is not that of a lubricant but rather that of a carrier.
Grease is used to lubricate a far larger number of rolling bearings than any other type of bearing, despite the fact that only a small percentage of centrifugal pump bearings are greased with grease. The widespread use of grease has been motivated by the possibility of simpler housing designs, less maintenance, less problems with leaking, and better sealing against filth. In addition, the use of grease has led to improved sealing against dust. On the other hand, due to certain restrictions, the use of grease is not permitted. It is not a good idea to use grease in situations where a lubricant must rapidly remove heat. Oil is required for rolling element bearings the majority of the time since the accompanying machine parts that they interact with are lubricated with oil.

There are advantages and disadvantages of using grease to lubricate the rolling element bearings. The advantages are:

    • Simpler housing designs are possible; piping is greatly reduced or eliminated.
    • Maintenance is greatly reduced since oil levels do not have to be maintained.
    • Being a solid when not under shear, grease forms an effective collar at bearing edges to help seal against dirt and water.
    • With grease lubrication, leakage is minimized where contamination of products must be avoided.
    • During start-up periods, the bearing is instantly lubricated whereas with pressure or splash oil systems, there can be a time interval during which the bearing may operate before oil flow reaches the bearing.

The disadvantages are:

    • Extreme loads at low speed or moderate loads at high speed may create sufficient heat in the bearing to make grease lubrication unsatisfactory.
    • Oil may flush debris out of the bearing. Grease will not.
    • The correct amount of lubricant is not as easily controlled as with oil.

When it comes to high-speed bearing functioning, making the right choice between a grease and an oil is of the utmost importance. To ensure that the bearing is properly lubricated, an elastohydrodynamic oil film needs to be created and kept between the spinning components of the bearing. Lubricating oil needs to have a viscosity that is high enough to survive the given speed, load, and temperature conditions in order for there to be an adequate buildup of an oil film that is capable of carrying an adequate amount of load.
To fulfill these requirements in the most effective manner, it is most likely advisable to use a different lubricant for each particular application. When it comes to the relatively simple rolling element bearing care required by the ordinary centrifugal pump, it is generally possible to reduce costs by stocking only a select few grades of lubricant. This will allow the pump to operate more efficiently. It has long been the common suggestion of many bearing manufacturers that the minimum base oil viscosity be maintained at 70 Saybolt Universal Seconds (SUS) or 13.1 centistokes (cSt). It was applied to the majority of types of ball bearings and some roller bearings in electric motors with the understanding that the bearings would operate close to their published maximum rated speed, that naphthenic oils would be used, and that the viscosity would not drop below this value even at the maximum anticipated operating temperature of the bearings. This was done in order to ensure that the bearings would be able to withstand the high speeds that would be required of them.
When applying greases to lubricate pump bearings, it is important to take the appropriate safety precautions. Because of the high shear rate that these lubricants have, bearings will overheat if they are lubricated with soft, long-fibered types of greases or oils that are extremely heavy. This will result in increased churning friction at higher speeds.

High temperatures are another side effect of using an excessive amount of lubricant.

Example of ball bearing affected by high temperature

It is possible to significantly lessen the heat-generating effects of lubricants by employing oils with sufficient film strength but low viscosity, as well as channeling or semi-channeling greases. This is one of the benefits of using these types of lubricants. The capacity of these greases to “channel,” or be pushed aside by the spinning ball or roller elements of a bearing, and to lie basically inert in the side cavities of the bearing or housing reservoir is the primary source of the advantages that these greases offer. Channeling greases are typically described as having a “short-fibered” structure and a buttery consistency, both of which contribute to the lubricant’s low shear rate. Even if a lubricant is supplied that has a slightly higher viscosity than the application required, this low temperature helps a functioning bearing to create a temperature equilibrium. This is true even if the application requires a viscosity that is somewhat lower. When there is more fluid friction, the temperature of the lubricant rises, and it stays at that level until the viscosity is decreased to the appropriate level. It is important to note, however, that the use of short-fibered greases in applications that are sensitive to vibration but do not include equipment rotation can cause damage known as “false brinelling.”
In general, greases are employed in situations where oils cannot be utilized. This includes areas where sealing does not occur or is insufficient, unclean environments, inaccessible locations, areas where oil pouring or splashing cannot be permitted, and areas where “sealed-for-life” lubrication is sought.

The majority of bearings experience premature failure due to static overload, wear, corrosion, failed lubrication, contamination, or overheating in their early years. It is possible to eliminate skidding, which is another common source of bearing difficulties, by guaranteeing that the bearing will always be loaded. Skidding refers to the incapacity of a rolling element to remain in rolling contact at all times.

Better bearing specification procedures have been proved to eliminate the vast majority of difficulties caused by static overload, as demonstrated by actual operations. By selecting, using, and storing lubricants in the appropriate manner, additional issues such as wear, corrosion, and lubricant failure, as well as contamination and overheating, can be avoided. The viscosity of the oil and the presence of moisture contamination are the key concerns, and in general, lubricants with a higher viscosity are favored.

When it comes to the mechanical design of reliable centrifugal pumps, there are a few things that need to be taken into consideration in addition to the numerous conceivable elements that could have an effect on bearing life. Bearings with precision tolerances are less tolerant of off-design pump operation than deep-groove Conrad-type radial bearings with slack internal clearance.

Because of their sensitivity to misalignment, ball bearings require careful mounting in order to remove this potential source of failure. The amount of misalignment allowed cannot be higher than 0.001 inch for every inch of the shaft’s length. It doesn’t matter what kind of cage a bearing has if it’s working in an improper alignment since it will eventually fail.

In conclusion, it is very important to remember that bearings should always have a trace amount of lubricant, which might take the form of oil or grease depending on the application. If this is not done, there will be damage to the bearing surfaces, which will shorten the life of the bearing. It is possible to prevent this damage by performing thorough cleaning and applying fresh lubricant as directed. Typically, there is a significant amount of time that passes between cleaning and re-lubing the bearings.
It is not difficult to determine whether or not a bearing requires oil. Check the indication for the level of oil at the site. Grease presents a unique challenge, as it is impossible to know when additional grease should be applied to a bearing. This is because the grease that is already there in the bearing does not abruptly lose its ability to lubricate it. These qualities diminish progressively with the passage of time. In order to identify when more grease should be added, prior operating experience, often known as history, is a helpful guide. The intervals are determined by the characteristics of the grease, the dimensions and configuration of the hearing, the working speed, the temperature, and the relative humidity.
It is recommended that the grease in the bearings of significant process pumps be changed once every 12 to 18 months. Because the lubricating capacity of grease naturally decreases with the passage of time, doing this will make the operation and maintenance of the pump more trustworthy.
If water or moisture is able to enter the hearing chamber, the intervals at which the bearings should be cleaned and re-lubricated should be reduced to a greater degree. Rain, hose-downs, pumps positioned under dripping equipment, mist, fog, and condensation are some of the other environmental factors that can contaminate bearings. Inadequate, damaged, or improperly filed shaft seals, as well as the breather cap and the lubricant oil fill cap, could all serve as potential entry points.

In most cases, grease is injected by means of a port known as a zerk (or zirk) fitting, or alternatively, the bearing end cover or housing cap must first be removed. Always remember to open the drain or expel port before injecting grease, whether you are doing so mechanically or hydraulically. Under the force of the pressure, the old grease will be expelled by the new grease. Also, don’t forget to close the drain port when you’re finished. The amount of grease that needs to be added is determined both by the size and design of the housing as well as the size of the bearing. The bearing should be completely saturated with grease, and the housing should be filled approximately 25% of the way. Overheating can occur when there is an excessive amount of grease.

To clean off the old grease from the bearing internals and the housing, do the following:

    • Remove as much as you can by hand.
    • Use a warm kerosene flush to clean the bearing and the housing.
    • Next, a flush with mineral oil of SAE 10 viscosity should be performed. If the old grease has caked up and become solid, you should do the following:
      • Soak the bearing and housing in heated kerosene.
      • Use your hand to slowly rotate the bearing clockwise.
      • Give the bearing a final cleaning with some clean degreasing solution or kerosene.
      • Once more, rotate the bearing’s outer race by hand while imparting a light axial and radial stress to the balls and races. Do this while keeping the bearing at room temperature.
      • Repeat the process of soaking and rinsing as many times as required until the earring rotates freely and smoothly.

After all of the old grease has been removed from the housing, it should be cleaned, and then it should be carefully inspected to ensure that there is no damage. If the bearing is not damaged in any way, it can be reinstated in the machine after being repacked with new grease of the appropriate sort and consistency, or it can be put away for use at a later time. Wrap the bearing entirely with wax or oilpaper and place it into a storage box so that it can be preserved for later use.

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:

  • Know and Understand Centrifugal Pumps – Larry Bachus & Angel Custodio
  • Youtube video training credit – SKF Group; JAES Company
  • Photo credit: chiefengineerlog; ACOEM USA; Metcar

What you need to know about vessel anti heeling system

The anti heeling system is part of the ballast system which has been explained in one of my previous posts and can be found if follow thins link.

The anti-heeling tanks are located on the port and starboard sides of the ship and are filled and emptied by means of the ballast system.

Example of anti-heeling system

A reversible propeller pump is used in the heeling system. This pump is attached to a pipeline that connects the two heeling tanks.

Example of heeling pump

Depending on the control position that has been preset, the pump can be started and stopped either from the anti-heeling system control panel located in the SCC or from the integrated control and monitoring system (ICMS) screen displays, located either in the SCC or on the bridge. On board, the use of the control panel for the anti-heeling system is the option that is most highly recommended because it enables full access to the system through a menu-driven operator display.

Example of anti-heeling system controller

When heeling operations are being performed, there will be a lowest level at which the pump will automatically shut off, same as a maximum level that can be reached in any tank.

Floats for the highest level are installed in each tank. These are wired up and attached to the monitoring and alarm system. Each tank is equipped with a low level transmitter, which will turn off the pump when the predetermined level is reached. When the pump is running, the system will turn off automatically if the ship’s heel is greater than 8 degrees.

During cargo loading and discharge activities, the vessel will be able to stay within acceptable heeling limits thanks to the anti-heeling system. On container vessels, the vessel should not be listed more than 0.5 degree to either side of upright in order to guarantee that containers move freely in the cell guides. However, the loading and unloading of containers can cause the ship to list beyond these limitations. The list can be corrected by moving a quantity of water from the port anti-heeling tank to the starboard anti-heeling tank, or vice versa.

The operating modes of the system are as follow:

    • AUTO: starting and stopping is decided by heel measurement to keep the vessel at a predetermined heel
    • MANUAL: starting and stopping is controlled by the operator
    • GOTO: the operator keys in a desired heel and the pump will run until that heel value is obtained
    • VALVE: the tank valves only are opened to gravitate water between tanks achieving the desired heel correction without starting the pump
    • LOCAL/COMP: operation of the heeling pumps remotely from the ICMS screen display in the SCC or the bridge.

It is important to note that only authorized personnel with a knowledge of the system and an understanding of ship stability make any adjustment to the anti-heeling system. Errors in adjustment can have serious implications on the vessel’s stability and operational performance.

Make sure that the anti-heeling tanks are filled with sea water to the correct level before beginning any mode of operation. This means that the combined total of both tanks should be less than 95% of the capacity of one tank.
Check to see that the pump, the control panel for the anti-heeling system, and any other system equipment all have access to electrical power.

The operation on AUTO mode of the anti-heeling system is only permitted in harbor. Here below I will exemplify, the operating mode based on above illustrated control panel:

On anti-heeling system control panel, key in MAIN to begin at the main menu, select RUN, then select AUTO. It is not possible to select RUN if the system is blocked for any reason. In this window the operator has two choices, START and SET. Firstly select SET; this will open a new window, AUTO SETTINGS. The operator must now verify that the settings are as required, as follows:

    • WORKING POINT: this is the reference value, normally set at 0 degrees. However, if another value is required, key in that required value. Positive values (+) refer to STARBOARD and negative (-) values refer to PORT
    • START AT: the pump will start when the heel angle from the working point exceeds this value. The factory setting is 1°
    • STOP AT: the pump will stop when the heel angle is less than this selected value. Typical heel would normally be when the vessel is upright or 0 degrees. The STOP setting must be at least 0.5 degrees less than the START setting to prevent the pump from operating too many stops and starts and so avoid overheating the pump motor
    • START DELAY: a time delay can be keyed in to start the pump only after the completion of the time delay, measured in seconds. Normal setting would be 0 seconds.

When all operating values have been selected and set return to the previous window by pressing the PREV key. The current heel value of the vessel will be displayed. If the text NOT READY is shown above the field START, make sure that the system is not in alarm and also make sure that the system is not in SEAMODE. If READY is displayed the START pushbutton can be operated; an LED light will illuminate to indicate that the system is now in auto. Two LED lights will illuminate to indicate when the pump is pumping to port or starboard.

To select MANUAL on the control panel key in MAIN to reach the main menu, then select RUN and then MANUAL. It will not be possible to select RUN if the system is blocked for any reason. In this mode there are three choices: PORT, STBD and TIMER. If the text NOT READY is shown above the field PORT or STBD, make sure that the system is not in alarm and make sure that the mode is not blocked. Pressing the pushbutton PORT or STBD will open the heeling tank valve and start the pump in the desired direction. When the desired heel correction has been achieved press key to stop the pump. Two LED lights will illuminate to indicate when the pump is pumping to port or starboard. A countdown timer will stop the pump when zero is reached. The preset value of this timer can be set by the operator, within certain limits. If the timer approaches zero when the pump is still required to run press the TIMER key. The timer will then start over again for the preset value.

To select GOTO control return to the main menu by keying in MAIN, select RUN, and then select GOTO. Once again RUN cannot be selected if the system is blocked. In this mode there is one selection: START. If the text NOT READY is shown above the field START, check out the alarms and make sure that the mode is not blocked or that SEAMODE has not been selected. NOT READY will also be shown if the current value is the same as the set value. Key in the desired heel value in the input field SET VALUE, positive (+) value indicates starboard and negative (-) value indicates port. Pressing the START pushbutton will open the heeling tank valve and start the pump in the desired direction.
The pump will stop automatically when the pre-selected heel value has been reached. Pressing the Key F8 STOP will interrupt the process. Two LED lights will illuminate to indicate when the pump is pumping to port or starboard.

To select VALVE control, return to the main menu by keying in MAIN. Select RUN and then VALVE. It is not possible to select RUN if the system is blocked. In this window there are two choices, OPEN and TIMER. If the text NOT READY is shown above the field OPEN, check out the alarms to make sure that the mode is not blocked or in SEAMODE. Pressing the OPEN pushbutton will open the anti-heeling tank valves while pressing Key F8 STOP will interrupt the process. Valve position is indicated by the text showing CLOSED, OPEN, CLOSING and OPENING. A countdown timer will close the tank valves when the desired heel correction has been achieved; the preset value of this sequence can be set by the operator within certain limits. If the timer approaches the desired heel correction position but the operator wishes to continue ballast transfer, press the TIMER key and ballast transfer will continue up to the preset value again.

The anti-heeling pump may be operated locally in manual mode for maintenance
purposes. Pushbuttons allow the pump to be started locally, in either the port or
starboard flow direction.

As specified, the above instruction is for exemplification purpose only, as every vessel has its own designed system which may be close or similar with the above.

Some vessels are equipped with anti-rolling tank which is fitted to provide a roll damping system to control the rolling of the vessel at sea and is a passive free surface open channel type anti-roll tank. The system is capable of adapting to changes in load and operation conditions by a change in the liquid level, the natural response period of the tank can be adjusted to the roll period of the ship. The system includes a liquid level and roll period indicating system and a phase sensing system to monitor the movement and control the anti-roll tank to assist the crew in achieving the most effective roll stabilization.

The operation of this type of anti-rolling tank consist of the following:

Prior departure

    1. Calculate the solid transverse metacentric height (GMs) without any free surface reduction of any tanks for the anti-rolling tank filled at the maximum operating liquid level.
    2. Check whether the calculated GMs is equal or higher than 3.0 meters. If this is the case, continue with 4.
    3. If the GMs is less than 3.0 meters, refer to the figure to obtain the correct operational liquid level. Recalculate GMs with the obtained liquid level. Refer again to the figure whether GMs is within the indicated range of GMs. If the GMs should fall on the dividing line between two operational liquid levels, use the higher level.
    4. Check whether the corrected GM including the free surface correction of all tanks (including the anti-rolling tank filled to the corresponding operating level) is above all minimum stability requirements. If operating parameters are acceptable fill or adjust the anti-rolling tank to the correct liquid level.

At Sea

    1. The tank liquid level/roll period indication system constantly monitors the operational conditions and will automatically alarm to alert the crew if any adjustment of the system is required.
    2. In case of emergency, vessel’s stability must be considered carefully. If necessary the tank can be emptied by operating the quick discharge dump valves from the control panel.
    3. The tank should be emptied if the GMs is below or above certain values.
    4. If the roll period of the vessel is shorter than 16.0 seconds the range of design efficiency is reached. The tank should be operated at the maximum designed operational liquid 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!

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Source and Bibliography:

  • Youtube channels: Marine Online and Hoppe Marine

Vessel water ballast and heeling systems explained…

All along the ship’s length, the ballast system utilizes water tanks positioned in the double bottom, along the sidewalls, and beneath the ship’s main deck.
In order to keep the ship’s draught and trim proper, to provide maximum stability, and to keep the ship’s stress and bending moments within acceptable limits, water is added to or removed from the ballast tanks. One tank or pair of tanks should never be partially filled (slack) at any given moment, as slack tanks provide a free surface effect that is detrimental to stability.

Ballast operation. Source and credit: Desi Pitara

Ballast systems typically refer to tanks with pipes and pumps that may be filled or emptied in order to alter the ship’s mass and hence its draft, but this is not always the case. Heeling systems on the other hand simply recirculate the ship’s ballast water to maintain a ship’s heel or trim. Heeling tanks are partially filled with water and are used to adjust the heel of the ship during loading and unloading operations. Water is transferred from the port heeling tank to the starboard heeling tank, or vice versa, in order to keep the ship in the upright position using a dedicated anti-heeling pump system.

The heeling tanks are filled and emptied by way of the ballast pumping system. In the event of a failure of the anti-heeling system, the ballast pump is used to transfer ballast as required between the port and starboard heeling tanks.

After an incident, the heeling system must be able to move huge amounts of water in a short period of time and give a heeling compensation

Example of working principle of antiheeling system. Source and credit: Marine Online

Both a tie line and a collecting pipe system are options for ballast system pipework. Simple collecting pipe systems have been most common, with the main line running through a ship’s pipe tunnel.

Example of a tie line ballast system
Example of collecting pipe ballast system

For ballasting and eductor drive operations, the ballast pumps can draw suction from the main sea water main crossing pipe in the engine room. As part of de-ballasting procedures, the ballast pump discharges directly overboard. Before beginning ballasting operations, care must be taken to ensure that the ballast main is properly flooded.

The ballast system is controlled from the ship’s control centre panel which enables the pumps to be started and stopped and ballast system valves to be opened and closed remotely. Usually the valves are hydraulically operated and all of them are normally located outside of the respective ballast tanks which allows maintenance and inspections to be carried out on all of the valves without having to enter a tank.

All ballast and de-ballasting operations for each tank must be entered into the Ballast Log Record Book, stating date, ship’s position, temperature, specific gravity, pumped quantity, tank quantity and any further remarks. Refer to IMO Resolution A868(20). The International Convention for Control and Management of Ship’s Ballast Water and Sediments has been accepted in 2004 and it applies to all vessels that carry ballast water. There are some basic procedures available for ballast water management:

Ballast water exchange – either all of the water is pumped out and then filled back up (sequential method) or fresh sea water is continuously added (flow-through method). With the sequential method, the tank is completely emptied and then filled again, but this changes the vessel’s load condition, which is not good. In the flow through or overflow method, the water is pumped through the tank until it overflows. To replace 98 percent of the total volume of the old ballast water with new water, the whole volume needs to be replaced about three times. This method doesn’t affect the vessel’s load condition, but it does increase the handling capacity of the ballast pump and the amount of time it is running.

Ballast water re-circulation – ballast water is recirculated within the ship instead of being released or taken in using this approach, which is dependent on the ship’s load. Ships carrying containers are particularly interested in this strategy, which keeps the ship’s overall mass constant while optimizing load distribution.

Ballast water management. Source and credit: Marine Online

Ballast water treatment – when the tanks are filled and when they are emptied, the ballast water is subjected to mechanical, physical and chemical treatment. There are a variety of ways in which water can be heated or subjected to UV radiation or ultrasound depending on the manufacturer, but the sediments are separated by means of filters.

Example of a ballast water treatment system. Source and credit: marine electro technical officer

When using ballast water treatment system, prior to the commencement of ballasting operations, the BWT units lamps commence a start-up sequence at which time the units are cooled by sea water. The incoming ballast passes through the filter which performs the function of removing larger organisms and particles, after the filter, the ballast water passes through the UV or chemical injection units which treat the water to the required IMO standard before entering the ballast tanks. On completion of ballasting, an automated sequence flushes the treatment unit with fresh water, following this, a CIP (Cleaning-in Place) cycle commences to clean the unit, which takes approximately 15 minutes. The cleaning cycle may also be operated manually from the local control panel.

During de-ballasting, the main difference to the ballasting procedure is that the filter is bypassed because the water would already have been filtered during ballasting. During the discharge process, water from the tanks is again passed through the UV or chemical injection units to destroy any organisms that may have formed during the time the ballast water has remained in the tanks.

Ballast system is normally operated by vessel Chief officer or one of the deck officers during their watchkeeping under Chief Officer supervision and the engine room should be informed by the imminent use of the system 9especially operating the ballast pumps).

Under normal circumstances no more than one pair of ballast tanks (port and starboard) should be partly filled at any one time in order to prevent stability problems due to the effect of slack tanks. Tanks not currently being filled or emptied should be completely filled or empty. Check the quantity of ballast water to be removed from the particular pair of tanks. Water should normally be removed from the port and starboard ballast tanks at the same time with heeling being controlled by the anti-heeling system.

It is important to note that hydraulic hammer in ballast lines can cause serious damage and must
be prevented at all times. Valves must only be opened in a manner that will prevent damage to pipes, pumps and other valves in the system. In the planning and execution stages of ballast operations, consideration must be given to the following:
– The opening of valve(s) from an empty tank into a line that may or may not be empty or in partial vacuum. This will allow the pressure or vacuum that may be present to decay slowly.
– Back filling of the lines from the sea chest should be done in a controlled manner by only opening the appropriate valves to the pumps and the ballast lines. This will again allow the pressure or vacuum that may be present to decay slowly. It may also be possible to vent any displaced air in the lines through the ballast overboard discharges.

It is the responsibility of all those either directly involved in or assisting in supervising cargo/ballast operations to ensure that the system valves are operated in a safe and proper manner and that the systems, including pump casings are vented before operations commence.

If the operator is to leave the Ship Control Center then the discharge, in case of de-ballasting, should be set to eductor discharge only, in order that the ballast pump does not run dry with the subsequent failure of the pump elements and shaft seal.

In order to strip out the tanks, different systems are used like water eductors or self-priming stripping pumps (usually lobe type) which are designed to run with low suction and without any additional water which is an advantage as the vessels are fitted with a Ballast Water Treatment System. An adequate trim should be maintained throughout the stripping operation to achieve good suction to the pump.

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Bilge system on vessels explained

A bilge system is a piping system installed onboard a vessel for the purpose of removing water that accumulates in enclosed spaces (holds, machinery spaces, cofferdams) as a result of condensation, leakage, washing, or fire fighting. It is also to be capable of controlling flooding in the Engine Room as a result of minimal piping system damage.

Bilge system. Source and credit: KARCO & Özgür Alemdağ

In general, the vessel’s bilge system consists of three main sub-systems:

  • Engine room bilge system
  • Cargo hold bilge system
  • Rudder trunk or bow thruster bilge system

The engine room bilge system and cargo hold bilge system are interconnected and an isolation valve is fitted between these two systems. This isolation valve should normally be closed and sealed and seal recorded into engine room seal book. The rudder trunk or bow thruster bilge system is a separate system.
The bilge system is served by three pump sets:

  • The engine room bilge pump
  • The cargo bilge pump
  • The fire and general service pumps

Under normal operating conditions the engine room bilge pump is used to pump from the engine room bilge main to either the clean bilge water tank or the oily water tank. Bilge water from the engine room system can be discharged overboard , while vessel is underway, only via the oily water separator.

The cargo bilge pump is used to pump from the cargo hold bilge main to the cargo bilge tank if the ship is designed as such. If there is no designated cargo bilge tank, the bilge can be pumped directly overboard after has been visually checked for presence of oil, otherwise should be pumped into engine room bilge tank via interconnection valve.

The fire and general service pumps can only discharge water overboard or to the fire and general service system. These pumps should only be used to pump bilge water in an emergency.

It is very important that the overboard discharge is not to be used for discharging bilges unless under emergency conditions.

The rudder trunk or bow thruster bilge system is operated by an ejector, which is driven by water, the driving water being supplied from the fire and wash deck system.

The engine room bilge pump is, usually, of a self priming type which can draw water from the various bilge suctions via the engine room bilge system and discharge to the oily water tank or clean bilge tank. It can take, also, suction from oily bilge tank, clean bilge tank, cofferdams, engine pit, void spaces, stern tube cooling tank etc. In general, all the bilge pump suction points are connected to the bilge pump via the engine room bilge system, except for the clean bilge tank, the oily water tank and the oily water separator. The engine room bilge pump is equipped with a suction strainer and, on modern vessels, the pump motor can be set to stop automatically if the pump runs dry. The pump can be stopped locally or from the shore connection stations on main deck close to the bilge & sludge shore discharge manifold.

Engine room bilge pump arrangement

The oily water tank receives water from the engine room bilge pump, and has different capacity according with the vessel size. The tank is equipped with a steam heating coil, and has, usually, three suction lines:

  • Sludge transfer pump suction, high
  • Sludge transfer pump suction, low
  • Engine room bilge pump

The oily water tank allows oil to separate from the bilge water by gravity and the oil can then be removed by the sludge transfer pump, which has a high and low suction. Water is removed from the oily water tank and transferred to the clean bilge tank by the engine room bilge pump.

Example of a bilge pump

The clean bilge tank receives water from the oily bilge tank and various scuppers and save-alls in the engine room. Similar with oily bilge tank, its capacity is strictly connected with the vessel size and is equipped with a steaming out connection. The clean bilge tank has two suction lines, one from engine room bilge pump and the other from oily water separator supply pump.

Only water with an oil content of less than 15ppm is discharged overboard. A feed pump supplies bilge water from the clean bilge tank to the oily water separator which is used to treat bilge water from the clean bilge tank before it is discharged overboard. About this machinery will discuss on a later post as the subject is very comprehensive.

As mentioned above, bilge wells connected to the engine room bilge system are normally pumped to the oily water tank using the bilge engine room pump. The bilge pump may also pump from the engine room bilge system to the clean bilge tank, cargo bilge holding tank or the shore connections. The procedure to pump from the engine room bilge wells to the oily bilge tank is, generally, as follow:

  • Check and ensure that the engine room bilge pump suction strainer is clean.
  • Check and ensure by taking a sounding measurement that there is sufficient space in the oily water tank for the bilge water, before starting the transfer operation . If the oily water tank is full, bilge water can be transferred to the clean bilge tank.
  • Open the bilge pump discharge valve to the oily water tank and ensure that all the other bilge pump discharge valves are closed.
  • Open the bilge pump suction valve to the main engine room bilge system as this connects all the suction points to the bilge pump.
  • Check the suction strainer on the bilge suction to be pumped and open the suction valve.
  • Start the bilge pump. Ensure that the bilge pump does not run dry. Usually, bilge pumps have a sea water suction connection which can be used for priming. don’t keep the sea water valve connection open for too long time, as there is a risk of filling the oily bilge tank with too much sea water.
  • Close the bilge suction valve before the bilge is completely empty to prevent the pump to run dry.

Under normal operating conditions the cargo hold bilge system is served by the cargo bilge pump which is, usually, a positive displacement pump but the pump suction is also equipped with a priming unit because of the length and large volume of the cargo hold bilge system. The pump will draw water from the various hold bilge suction points via the forward and aft cargo hold bilge systems and discharge to the cargo bilge holding tank or directly overboard.

The fire and general service (GS) pumps are vertical centrifugal pumps and each pump is equipped with a priming unit. A cross-connection line is fitted between the pump suction and discharge and this line is arranged to ensure that bilge water cannot be discharged into the fire and wash deck main.

The emergency bilge suction is provided to deal with serious flooding of the machinery spaces. Under such circumstances when the situation threatens the safety of the vessel, it is permissible to use this means to pump the bilge water directly overboard. The emergency bilge suction valve is part of the ship’s safety equipment and must be maintained operable with testing and greasing at intervals not exceeding one week.

Example of bilge emergency suction live test

The bilge system, especially the cargo hold bilge system must be periodically pressure and vacuum tested (6 monthly period) in order to check the valve proper sealing and pipe integrity. Failure to do so can result in cargo hold flooding and damaging of cargo.

Cargo hold flooding due bilge system failure

Usually, cargo hold bilge wells are equipped with non return flaps which prevents the water backflow into the bilge wells. Checking the integrity of these flaps is one of the reason of the system pressure test that must be periodically done. The vacuum test is done in order to check the remote butterfly valves sealing property.

Inner side of non return flap
Cargo hold bilge non return flap
Failure cargo hold butterfly valve

The procedure for vacuum and pressure testing will follow into a later post.

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