Understanding Engine Hydrostatic Locking: Causes, Prevention, and the Role of Marine Engineers

In the world of marine engineering, hydrostatic locking is a term that sends shivers down the spine of every professional. It’s a potentially catastrophic problem that can lead to severe damage to engines and, in some cases, endanger the entire vessel. In this article, we will delve into the causes of engine hydrostatic locking, how it can be prevented, and the crucial role marine engineers play in ensuring it doesn’t reoccur.

What is engine hydrostatic locking?

Engine hydrostatic locking, also known as hydrolock, occurs when a liquid, usually water, enters the combustion chamber or cylinders of an engine, preventing the engine from turning over. This unwanted intrusion of liquid disrupts the engine’s internal workings, and in the case of a marine engine, it can spell disaster for the entire vessel.

Example of oil present into engine intake manifold. Source and credit: dieselmarineinsights.blogspot.com

For example, hydrolock happens when a volume of liquid greater than the volume of the cylinder at its minimum (end of the piston’s stroke) enters the cylinder. Since liquids are nearly incompressible, the piston cannot complete its travel; either the engine must stop rotating or a mechanical failure must occur.

Causes of Engine Hydrostatic Locking

The most common cause of hydrolocking in marine engines is water ingress through the exhaust system. This can happen if the exhaust outlet is submerged due to waves, trim, or loading conditions. Water can also enter the engine through the air intake, fuel system, or cooling system due to leaks, flooding, or condensation.

Depending on how much water is in the cylinders and how fast the engine is running, hydrolocking can have different effects on the engine. If the engine is stopped or idling, hydrolocking may cause the engine to stall or refuse to start. If the engine is running at high speed, hydrolocking may cause a loud noise and a sudden stop of the engine. The sudden expansion of gases can also cause gaskets to blow or cylinders to crack. The most common damage caused by hydrolocking is bent or broken connecting rods, which connect the pistons to the crankshaft.

Bent connecting rod. Source and credit: dieselmarineinsights.blogspot.com

Bent connecting rod. Source and credit: dieselmarineinsights.blogspot.com

Apart from water, when the engine is off, and there’s an intake leak, other fluids (oil, fuel) can easily enter the cylinders.

Prevention of Engine Hydrostatic Locking

  • Regular Maintenance: The most crucial step in preventing engine hydrolock is regular maintenance. This includes:
    • Checking and changing air filters, inspecting seals and valves for leaks, and ensuring that the engine is in optimal working condition.
    • Check and maintain the exhaust system regularly. Install anti-siphon devices or water traps to prevent water from flowing back into the engine.
    • Check and maintain the air intake system regularly. Make sure that the air filter is clean and dry and that there are no obstructions or leaks in the ducts or hoses. Avoid operating the engine in areas with high humidity or spray.
    • Check and maintain the fuel system regularly. Make sure that the fuel tank is vented properly and that there are no leaks or contamination in the lines or injectors. Use fuel additives to prevent water from accumulating in the fuel.
    • Check and maintain the cooling system regularly. Make sure that the coolant level is adequate and that there are no leaks or corrosion in the radiator, hoses, or pump. Use antifreeze to prevent freezing and boiling of the coolant.
  • Proper Ventilation: Adequate ventilation in the engine room can help reduce condensation and the risk of hydrolock. Proper ventilation systems can also help keep the engine room dry.
  • Water-Tight Integrity: Ensuring that the vessel is properly sealed and that water cannot enter the engine room in the event of flooding is essential. Make sure that the exhaust outlet is above the waterline and that there are no leaks or cracks in the pipes or valves. Regular inspections for potential breaches are crucial. Avoid operating the engine in extreme weather conditions or rough seas. Reduce speed and load when encountering waves or wakes. Monitor the engine temperature and pressure gauges and listen for any unusual sounds or vibrations.
  • Proper Shutdown Procedures: When shutting down the engine, it’s important to follow the manufacturer’s recommended procedures. This may include turning off the fuel supply before stopping the engine, preventing the intake of water during the cooling down process.

The Role of Marine Engineers

Marine engineers are responsible for designing, installing, operating, and maintaining marine engines and related systems. They play a vital role in preventing hydrostatic locking by ensuring that the engines are suitable for marine applications and that they meet safety and performance standards. Their responsibilities include:

  • Regular Inspections: Marine engineers should conduct regular inspections to identify and address potential issues that may lead to hydrolock. This includes inspecting intake systems, seals, and valves.
  • Maintenance: They are responsible for the routine maintenance of the engine, ensuring that air filters are changed, seals are in good condition, and the engine is functioning optimally.
  • Emergency Response: In the event of flooding or water intrusion, marine engineers must act swiftly to prevent or mitigate hydrolock. This may involve sealing off the affected area, pumping out water, and assessing and repairing any damage. They use their knowledge and skills to troubleshoot and resolve any issues related to hydrostatic locking or other engine malfunctions.

    Broken liner. Source and credit: dieselmarineinsights.blogspot.com

  • Training: Owners must ensure that the vessel’s engineering crew is trained to follow proper shutdown procedures and respond effectively in emergency situations. Marine engineers also educate and train other crew members on how to operate and maintain marine engines properly. They provide guidance and instructions on how to prevent hydrostatic locking and what to do in case it happens. They also follow emergency procedures and protocols to minimize damage and ensure safety in case of hydrostatic locking or other engine failures.

In conclusion, engine hydrostatic locking is a serious concern in the world of marine engineering. By understanding its causes and taking proactive steps to prevent it, marine engineers can safeguard the vessel and its crew. Their vigilance in regular maintenance, proper shutdown procedures, and rapid response to emergencies can make all the difference in ensuring the smooth operation of marine engines and the safety of everyone on board.

You can read a very interesting case study related to engine failure due hydrolocking if you follow THIS LINK.

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

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

Example of generator’s synchronizing panel

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

What is Reverse Power? 

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

Preventive Measures and Precautions

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

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

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

      Example of frequency matching

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

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

Example of a reverse power protective relay

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

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

Troubleshooting Reverse Power

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

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

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

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

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

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

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

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

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

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What you need to know about main engine continuous low load operation

I believe that many of you, have heard in the last couple of years about running the main engine at low load or slow steaming due increasing fuel price and lately due more stringent environmental regulations.

The 2-stroke engines are designed and optimized for operation in the load range above 60 % CMCR, but is possible to use them at continuous low loads down to 10% CMCR if we pay special attention as they are some recommendations on what needs to be observed when operating the engine at loads lower than 60 % CMCR.

It is very important to be aware that at lower engine load between approximately 60% and the auxiliary blower switch-on/off point, the turbocharger efficiency is relatively low and within this power range the engine operates with a lower air/fuel ratio resulting in higher exhaust gas temperatures.

The electronic controlled engines are more suitable for continuous low load operation than the conventional engines, due to their electronically  controlled common rail injection system.

Example of common rail injection system

These engines allow for higher injection pressure and selective fuel injector cut-off at very low loads, thus reducing excessive carbon deposits, exhaust gas economiser and turbocharger fouling.

The engine makers have issued a set of recommendations that should be observed, in order to limit the adverse affects of continuous low load operation as much as possible. The following needs to be in order:

    • The fuel injection valves should be in good working order.
    • When operating on HFO, the fuel viscosity required at the fuel pump inlet for conventional engines must be in the range of 13 to 17 cSt; for electronically controlled engines must be in the range 10 to 20 cSt. However, it is recommended to maintain the viscosity at the lower end of the range 13 to 17 cSt as specified in the engine operating manual, without exceeding 150°C at engine inlet. Sufficient trace heating of the fuel system on the engine must be ensured.
    • Keep the LT cooling water close to upper limit at 36°C in order to maintain the optimum scavenge air temperature and to minimize effects of possible cold corrosion.
    • For DF (dual fuel) engines operating in gas mode or (Low Sulphur) liquid fuels keep the LT cooling water set point at 25 °C to maintain a low (optimized) scavenge air temperature.
    • Clean the turbocharger as per manufacturer’s instruction manual.

Apart from above the following should be observed, monitored and adjusted accordingly:

    • The cylinder oil feed rate is load and sulphur dependent and is recommended to be properly adjusted as per the fuel that it is in use (about cylinder lubrication you can read in here). Frequent piston underside inspections must be carried out to monitor piston running conditions and signs of over-lubrication, as over-lubrication can lead to scuffing due to hard alkaline deposits on the piston crown.
    • The exhaust gas temperature after the cylinders should be kept above 250°C in order to reduce and avoid cold corrosion, fouling of exhaust gas receiver and turbocharger nozzle ring. If the exhaust gas temperature drops below this value, the engine load should be increased.
    • If the exhaust gas temperature gets too high (>450°C after cylinders), the auxiliary blower may be switched to “continuous running”. However, it has to be taken into account that not all auxiliary blowers and circuit breakers may be suitable for continuous running at electrical loads above nominal current.
    • Repeatedly switching on/off of the auxiliary blower must be avoided. If necessary, the auxiliary blower controls have to be switched to “manual operation”, or operation in this load area has to be avoided.
    • Inspect and lubricate the bearings more frequently if considered necessary due to increased operation of the blower. This also includes the inspections of the non-return valves for the scavenging air.
    • A concern during continuous low load operation is the accumulation of unburned fuel and lubricating oil in the exhaust manifold, as such deposits can ignite after the engine load is increased again. This may result in severe damage to the turbocharger due to sudden over-speeding. Therefore, it should be considered to periodically (twice a week) increase the engine load as high as possible, however at least 70% for at least 1 hour, in order to burn off accumulated carbon deposits. The load-up has to be done very carefully (i.e. during 2 hours) in order to avoid adverse piston running conditions due to carbon that has built up on the crown land of the piston head and to avoid possible exhaust manifold fire.
    • Exhaust manifold and other related components (scavenging air receiver, exhaust gas valves, turbocharger grid, etc.) need more frequent inspections and possible cleaning. Depending on result of inspections, the regular engine load-up intervals might be adapted if no excessive deposit accumulation is detected.
    • An economiser with closely-spaced fins may also require more frequent soot blowing.
    • On Dual-Fuel (DF) engines operating in gas mode, the described regular loading up to high loads is not required. The deposit formation is minimal compared to diesel mode operation.

In order to improve the piston running performance and reduce the risk of cold corrosion in cylinder liners, when the engine is continuously running at low loads, the temperature range of the cylinder cooling water outlet is increased. For example, Wärtsilä recommends keeping the cylinder cooling water outlet temperature as close as possible to the alarm limit. As a consequence of the increase of the cylinder cooling outlet water temperature, the respective alarm and slowdown settings need to be adjusted in some engines as well.

Example of alarm settings on Wartsila engines

In order to further optimize the engine operation at low load, Wärtsilä has developed A Slow Steaming Upgrade Kit that involves cutting out of a turbocharger.

Example of Wartsila Slow Steaming Kit

This increases the scavenge air delivery at low load for better combustion and more optimum temperatures of engine components. With this kit the following is achieved:

    • With the increased scavenge air pressure the auxiliary blower on/off threshold is at lower loads compared to engines with all turbochargers operative.
    • A considerable reduction in SFOC with cut out turbocharger and increased scavenge air pressure in the low-load range.
    • Due to better combustion at lower loads the risk of turbocharger and economizer fouling is decreased and the formation of deposits due to unburnt fuel is reduced.

The time interval between engine load-up to burn off carbon deposits can be increased based on inspection results. In order to burn off the deposits, a high enough exhaust gas temperature at turbine inlet is needed. The engine needs to be loaded up until the exhaust gas temperature at turbine inlet corresponds to 380°C. If this temperature is not possible to reach, the engine needs to be loaded up to the maximum load that can be reached with one turbocharger cut-out.

In combination with the above described slow steaming kit, Wärtsilä also recommends the installation of electronically controlled cylinder lubrication, called Retrofit Pulse Lubrication System which provides optimal lubrication due to the precisely timed feeding of oil into the piston ring pack and savings in lubricating oil.

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.

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Source and Bibliography:

  • Wartsila 2 Stroke –  Service letter RT174 – 27/11/2014

What you need to know about electrical preferential tripping and sequential restarting

Onboard vessels, modern power management systems make it less likely for power to go out for no reason, but engineers must be familiar with the specific procedures, where to find the instructions and procedures, and ready to act in case of automation failure.

Example of Power Management System

In case of a problem with power main diesel generators or in case of overcurrent, non-essential loads are interrupted automatically, in order to prevent the ship’s power failure. Preferential tripping has been fitted to reduce the possibility of the loss of essential vessel supplies if an event as described above will occur. It has been arranged that load reduction will be achieved by an ordered disconnection of non-essential supplies to prevent a blackout that may put the vessel’s safety at risk.

Example of preferential trip alarm

Depending on the vessel electrical layout and design, there are different stages (two or three) of preferential tripping. For example:

      • if the current on a running generator exceeds 100% of the generator rating for a period exceeding 5 seconds, the PMS will initiate the release of the 1st stage preferential tripping (PT1), thereby providing protection against the overcurrent which would otherwise trip the circuit-breaker – non critical ship systems.
      • if the current on a running generator exceeds 100% of the generator rating for a further 5 seconds, the PMS will initiate the release of the 2nd stage preferential tripping (PT2) – cargo hold vent fans and packaged air conditioning units.
      • in some vessels if the current on a running generator exceeds 100% of the generator rating for a further 5 seconds, the PMS will initiate the release of the 3rd stage preferential tripping (PT3).

Example of 1st and 2nd stage preferential trips alarm

on some other systems the preferential trips can be triggered in three ways regardless of the generator being under PMS or manual control:

      • an overcurrent condition in a main generator for a preset time will initiate first stage trips – if the current on a running generator reaches 120 % of the rated full load current for a period of 10 s, the breaker overcurrent protection circuit will initiate the release of the first stage of preferential tripping. If the 120% overload condition should continue for 40 seconds the generator VCB itself would trip, initiating the 2nd stage trip.

Example of DG overcurrent alarm leading to preferential trip alarms

When normal conditions resume, the tripped breakers must be manually reset.

      • abnormal trip of the generator VCB – second stage tripping. This abnormal trip of the generator VCB can be caused by any of the following:
          • low lubricating oil pressure
          • high fresh water cooling temperature
          • overspeed of generator engine
          • short-circuit current
          • nuisance trip

Should such trip occur then the remaining preferential trips will operate simultaneously.

      • manual tripping – the bus tie panel carries emergency stop contacts and preferential trips.

To trip the specific consumers, their circuit breakers are fitted with undervoltage (UV) trips. The supply to these UV trips is interrupted by the preferential tripping relays.

Example of UVT trip device

The identifications labels of the consumers configured for preferential tripping are coloured yellow with either PT1, PT2 or PT3 engraved into them.

Preferential tripping stages are accompanied by alarms into the alarm and monitoring system.

The vessel’s automatic control system will automatically restart the required machinery to restore power to the vessel, but to fulfil this requirement, at least one diesel generator must be left in the automatic standby mode. The essential machinery is started automatically according to the example sequence shown below.

Example of sequential restart list

The sequence is started when power is restored to the 440V main switchboard. The restart sequence is usually left enabled, however, the operator may disable the sequence, and if the sequence is disabled, an ‘auto start sequence disabled’ alarm is raised. The sequence is automatically halted in the case of another blackout.

When normal power is restored after a blackout, all essential service machinery in service before the blackout will be started automatically when the main switchboard has regained power. Motors that were selected for duty before the blackout will be automatically returned to duty when power is restored. Similarly, motors selected for standby will automatically return to standby. If the machinery designated for duty does not restore normal system conditions, such as pressure, within a preset time, the standby motor will cut in automatically. If power is only restored to the emergency switchboard, motors whose supply is from the emergency switchboard will start irrespective of any previous selection.
In the event of a blackout all transformers in the HVS will switch off. After the first main generator is connected to the HV busbar the transformer outlets will automatically switch in sequentially in two steps, depending upon the part of the switchboard concerned.

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What you need to know if white metal fragments are found inside main engine crankcase

Two-stroke bearings are mainly composed of aluminum or tin-based alloys, allowing the bearing to bed and transfer the load over a broader area. If the bearing surface experiences excessive stress, the bearing shell will normally continue to function as the load is distributed across a greater area. As a result, most white metal fragment detection will simply be an indication of bearing deterioration that requires immediate attention, as material fatigue would result in white metal separation.

Example of main bearing deterioration

When metal particles are detected in the crankcase, it is crucial to pinpoint their source. The most likely source is the white metal bearings, which may be confirmed by examining the magnetic characteristics of the particles using a magnet. White metal is nonmagnetic and appears silvery white. To determine the source of the particles, it is essential to record the shape and size of the particles that are discovered, as well as the place where these particles are discovered (sometimes due to natural trim of the vessel the particles may move during operation).

Example of white metal fragments found inside main engine crankcase

The LO filters and the mud discharge filter should be inspected to determine if the engine running has dislodged more (thin) particles. It is essential to eliminate any metal particles from the engine’s crankcase and LO filter. The overall area of the bearing surface area that has been destroyed must be determined, and images of the particles showing their size must be taken.

Example of white metal particles found inside oil filter

It is necessary to be aware of the different types of bearings installed on the engine, such as thick or thin shell type main bearings.
It is of the utmost importance to always have spares of each type of engine bearing and they must be included on the ship’s vital spares list. Spare bearing shells must be maintained/protected and kept in a manner that allows them to be used when necessary; ensuring that all tools required for bearing replacement are on board.

It is important to know that on MAN engines, if fatigue failure is found on a conventional bearing shell, it is advised to switch to a Blended Edge design.

Fatigue failure is the most typical form of failure that is seen in the form of dislodged white metal particles from the bearing shell and is observed in vessels where the bearings have been subjected to cyclic stress for an extended period of time. Frequently, fatigue cracks result from a high top clearance.

In general, the bearings are examined by measuring the top clearances which is an indicator to detect the state of the bearing (periodic checks are performed without opening the bearing housing), but also serves as a verification of the correct reassembly of the bearing. The clearances for new bearings must fall within the parameters indicated in the maintenance manual.

Failure due to contact damage on crosshead bearings on 2-stroke engines is caused because these bearings are more sensitive than other bearings due to the inability to build a hydrodynamic LO film for lubrication, which is exacerbated by operating at low loads, such as with the turbocharger cut out (TCCO) system for low-speed operation.

Example of a cross head bearing

At low load operations, the crosshead pin does not display pin lift in the same manner as when the engine is working at a higher speed and this poses a challenge to the hydrodynamic oil film thickness. Reduced oil thickness is the result of an unbalanced relationship between upward and downward forces in the reciprocating system, which causes the crosshead bearing to always rest at the bottom of the lower shell. In a higher-speed engine with all turbochargers operational, the forces of inertia drive the pin to the upper shell once per revolution, resulting in a thicker oil layer. Consequently, contact damage is more prevalent on vessels operating with a light load.

If a bearing develops damage, it swiftly progresses to the edge and finally forms a hole at the edge, allowing white metal to fall into the crankcase below the bearing support.

It is very difficult to know with certainty from where the white metal comes, however crosshead bearing damage is considered more critical than crankpin and main bearing damage.

It is important to note that white metal particles that are less than 0.5 mm or are the same size as the bearing clearance and have smooth surfaces on both sides show that the white metal is being squeezed out of the bearing and this means that the bearing is being overloaded, which should be looked into before the ship departure.

Maximum permissible area of white metal discovered and assessment can be found if you subscribe into the Seafarer’s World Forum (powered by chiefengineerlog.com).

Close visual inspection must be performed on the bearings in the vicinity of the cylinder units where the metal particles are located, giving particular attention to the severely loaded bearing edges with a powerful flashlight in search of any dark spots (mirrors could be used for areas which are difficult to view and access). Listed below are the crucial areas for the various bearings:

      • Upper half edge for the bottom end bearing of the connecting rod;
      • Lower half edge for the cross head and main bearing;
      • Crosshead guide shoes and slippers for marks across the length of the bearing surface.

A wire feeler check could be carried out on the main, cross head and connecting rod bearings to further confirm the finding during visual inspection.

In the form of service letters, engine makers have given inspection instructions and set the conditions that must be met to be able to check the condition of the bearings on an engine (service bulletins SL2012-552 and RT-188).

Any white metal particles found in the crankcase must be confirmed with an open-up inspection to find out where they came from. However, if the number of white metal particles found adds up to more than the area listed in the table found in Seafarer’s World Forum (powered by chiefengineerlog.com), or if the white metal particles have a thickness that looks like they were squeezed out of the bearing shell, the source must be found and confirmed before the engine can be run.

Most of the new engines come with a Main bearing temperature monitoring system and a bearing wear monitoring system. These systems are very reliable and work well to give an early warning before engine parts come into contact with each other and can be used to check the condition of the engine’s bearings.

If there is water in the LO, it could get into the bearings and damage them. This usually happens at the crosshead bearing, where water can cause corrosion at the top layer and then damage the bearing mechanically. The amount of water in the LO should always be less than 0.1%. If the change is more than 0.1 percent, further investigation should be carried out. Engine can’t be run at more than 0.2 % water content there is a specific order and recommendation. If the engine is run with more than 0.2 percent water in it, the crosshead bearing should be checked by opening it up.

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

Source and Bibliography:

  • MAN Diesel video training
  • Wartsila Service Letter RT-188
  • MAN Diesel & Turbo Service letter SL2012-552

What is emergency diesel generator, its purpose and how to safely operate it?

The emergency diesel generator is a self contained diesel engine driven electrical generator set, which is located in a separated room with access from deck. Usually the generator is the self-excited, brushless type and can be set for manual or automatic operation. Auto will be normally selected, with the manual setting being used for testing the generator or in case of auto start failure.

Emergency generator

Upon failure of the main diesel generators the emergency generator set will start automatically and connect to the emergency switchboard to maintain supplies to essential services. It is also used to get the ship under power from dead ship condition and will enable power to be supplied to the essential services without the need for external services such as starting air, fuel oil supply and cooling water.

The engine is normally equipped with a self-contained cooling water system which is circulated by an engine-driven pump and cooled in a radiator. Cooling air is forced through the radiator by an engine-driven fan. The cooling water is mixed with anti-freeze in order to prevent freezing of the cooling water in cold conditions and a thermostatic electrical heater is fitted in the cooling water system to maintain the engine in a condition ready for immediate starting. The engine-driven cooling water pump supplies the LO cooler and after leaving the engine, the cooling water flows to the thermostat and back to the radiator or engine circulation pump.

The engine running gear is force lubricated by an engine-driven gear pump which draws oil from the sump tank and discharges it through the cooler and a filter to the lube oil rail. The system is equipped with a pressure regulating valve to prevent over-pressure of the lube oil supply to the engine.

The generator is supplied with fuel from a dedicated tank which is located in the emergency generator compartment. The fuel level into the tank, as per SOLAS requirement should be enough for 18 hrs in case of cargo ships and 36 hrs in case of passenger vessels of continuous running of the generator at maximum nominal load.

The engine is normally started by means of an electric starter motor with power to the motor being supplied by batteries. The batteries are provided with an isolation switch and are maintained in a fully charged condition by a battery charger which operates continuously and is usually equipped with an alarm which is activated if the charger fails. A back up hydraulic starter is also fitted with the hydraulic power being manually generated via a hand pump. An accumulator charged by the hand pump provides the pressure to drive the hydraulic motor which connects with the flywheel.

Emergency generator hydraulic starter

When in automatic operation only the electric starter motor is utilized. The engine should be started at least once a week and run up to full load monthly.

The emergency switchboard is normally supplied from the main 440V switchboard and when AUTO mode is selected, the emergency generator is started automatically by detecting no-voltage on the emergency switchboard busbar. Usually, three start attempts are available under automatic control, with a start failure alarm in the event of a failure to start.

The emergency generator air circuit breaker (ACB) will connect automatically to the emergency switchboard after confirming the continuation of no voltage and the bus tie breaker on the emergency switchboard, which feeds from 440V main switchboard is opened automatically when no voltage is detected.

Emergency generator air circuit breaker (ACB)

The emergency generator is designed to restore power to the emergency switchboard within 45 seconds as per SOLAS requirement. According to SOLAS regulation an emergency generator must be fully operational for up to 10 degree of trim and 22 and a half degrees of list and need to start anytime at 0°C temperature.

Example of an emergency generator control panel

So, in order to enable the emergency generator to start automatically in the event of a blackout:

  • The mode selector switch at the local control panel must be set to the AUTO position.
  • The fuel tank must always contain sufficient fuel for at least 18 hours of operation at full load.
  • The battery system must always remain on charge and the batteries must be checked to ensure that they are fully charged. If one of the battery systems fails it must be disconnected and must be replaced at the earliest possible time.

Usually, after power has been restored on the main switchboard the generator ACB and tie breaker will automatically operate and engine will stop. If the automatic system fails, the manual procedure to stop the engine after power restoration is as follow:

  • Turn the emergency generator operating mode switch to the MANUAL position.
  • Manually open the emergency generator circuit breaker.
  • Manually close the normal supply circuit breaker (tie breaker) to the emergency switchboard.
  • Manually stop the emergency generator by pressing the STOP pushbutton on the engine panel.
  • After engine stops, turn the emergency generator operating mode switch to the AUTO position.
Example of an emergency generator electrical panel

If for some reason the emergency generators fails to start automatically, then this must be started manually either using battery starter or hydraulic starter mentioned above. The procedure of manual starting of the emergency generator and manual closing of the circuit breaker is, generally as follow:

  • Check that there are no water, fuel or lubricating oil leaks and that the emergency generator is available for starting and ensure that there is no restriction on the engine starting.
  • Ensure that the engine control panel is supplied with electrical power.
  • Ensure that the fuel system is fully primed and that all of the valves from the fuel tank to the engine are open.
  • Check the water level in the radiator expansion tank add water to the tank if necessary.
  • The generator heater and switchboard heater must be switched on.
  • Ensure that the starter batteries are fully charged and that they are able to supply electrical power to the starter motor.
  • Check the oil level in the engine sump and replenish if necessary.
  • Turn the engine control panel mode selector switch to the MAN position.
  • At the engine control panel press the START pushbutton. The engine should turn over on the electric starter motor and should fire. When the engine fires the START pushbutton must be released. The engine governor will regulate the speed to the preset value.
  • Check that the engine runs smoothly without excessive noise or vibration.
  • When the engine is running normally and the generator voltage and frequency are correct, the generator may be connected to the switchboard. The emergency generator circuit breaker is closed by pressing the CLOSE/MAN pushbutton on the same panel.

In order to test the interlock between main switchboard and emergency switchboard the procedure is quite simple but requires attention in order to prevent total power loss during test. In this procedure the bus tie breaker (located normally in ECR and EG’s room) need to be manually open and the emergency switchboard will black out. The emergency generator will start automatically and the generator ACB will close to feed the emergency generator. To return to the normal mode, the tie breaker must be manually closed and emergency generator ACB will open and generator will automatically stop after a preset cooling time. The same test can be performed by turning the E/G SEQ TEST switch, located at the emergency switchboard, inside the emergency generator panel, to the ENG & ACB position. The bus tie breaker will receive an open command. However, during live test in presence of a surveyor or PSC officer , they will always ask to manually trip the tie breaker.

It is very important to avoid frequent consecutive start and stop of the emergency generator without cooling down as this will lead to alternator heater or winding failure. Moreover, running the engine on idle before stop will allow the cooling water and lube oil to carry away heat from the combustion chambers, bearings and turbocharger. It is very important for the turbocharger where frequent sudden stops can result in damage to the bearings and seals.

Generally the idling period before stop is set for 5 minutes and the time period should not be extended, as long periods of idling will result in poor combustion and build-up of carbon deposits in the engine combustion chamber, exhaust manifold and turbocharger.

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