Motor Flashcards
1a. State the reason for turning the engine with the turning gear prior to starting. (4 marks)
b. State the reason for leaving the indicator cocks on main engine cylinders open when the engine is turned initially with the turning gear. (4 marks)
c. State the reason for leaving the lubricating oil circulating after “Finish with Engines”. (4
marks)
d. State why diesel alternator cooling water may be circulated through the main engine after shutdown. (4 marks)
1a. State the reason for turning the engine with the turning gear prior to starting. (4 marks)
- [ ] When piston goes from TDC to BDC at each other these points they may not be aswell lubriacted or just be touched barely with the piston meaning when you turned the piston when the engine is on hotspots can occur cause thermal shock uneven heat distribution
- [ ] Ensure nothing is left in the engine blocking it, trapped pressurised air/water
- [ ] Check turning gear amps to see they are high, means there could be a blockage
b. State the reason for leaving the indicator cocks on main engine cylinders open when the engine is turned initially with the turning gear. (4 marks)
- [ ] Allows Debris/Trapped air to be discharged
- [ ] Checks for fuel leaks through Indicator cock if cylinder liner has a crack and LO/FW has leaked into it
c. State the reason for leaving the lubricating oil circulating after “Finish with Engines”. (4 marks)
- [ ] Cooling left on to prevent engine seizure
- [ ] To prevent engine oil cooking which could cause to become carbon deposits
- [ ] Maintain lubrication, preventing film is out onto cylinder liner so it’s ready to start
-[] you need cooling to reduce thermal stress by bringing down engine temp gradually
d. State why diesel alternator cooling water may be circulated through the main engine after shutdown. (4 marks)
d. State why diesel alternator cooling water may be circulated through the main engine after shutdown. (4 marks)
-[] Main engine cooling pumps are engine driven so if they shut down because engine has stopped we can use diesel alternator fresh water
-[] Controlled cooldown when using these
-[] Automatic operation - auxiliary systems are usually automatic they turn on when engine is stoped
-[] Using a small electric pump to circulate water after shutdown is far more energy efficient
-[] prevents engine parts over heating
Summary (Exam Style):
Although the main engine has its own cooling system, this is typically mechanically driven and stops with the engine. To prevent heat soak, thermal stress, and oil degradation after shutdown, a separate electric-driven circulation system is used to ensure uniform and gradual cooling of engine components.
a. Describe the procedure to change the fuel supply of the main propulsion engine from high viscosity fuel to low viscosity fuel such as diesel oil. (16 marks)
- [ ] Ensure fields tank full
- [ ] Ensure diesel pump working
- [ ] Inform bridge
- [ ] Fobas calculator - speed/capacity/engine cylinders/size of engine
- [ ] Seca area
- [ ] England load reduction as recommended by manufacturer
- [ ] Gradually reduce steam 2c per minute no more (inlet heating valve)
- [ ] (Heater has 4 valves Fuel in/out. Steam in/out )
- [ ] Selection switch is a 3 way valve will introduce fuel slowly
- [ ] Control flow pressure (slowly changing each valve)
- [ ] Keep monitoring exhaust temps/viscosity(fuel temp) pressures
- [ ] Ensure engine is operating slowly through before 25-40 percent mcr before increasing
What else can these boiler valves/parts be called?
- [ ] Boiler vent valve-
- [ ] Mud hole -
- [ ] Auxiliary steam stop valve -
- [ ] Are mud hole and blow down valve the same?
What else can these boiler valves/parts be called?
- [ ] Boiler vent valve- air cock
- [ ] Mud hole - scum blow down valve
- [ ] Auxiliary steam stop valve - is on top of main steam stop valve
- [ ] Mud valve and blow down valve are two separate valves
a. Describe the procedure to change the fuel supply of the main propulsion engine from high viscosity fuel to low viscosity fuel such as diesel oil. (16 marks)
Procedure for Changing from High Viscosity Fuel to Low Viscosity Fuel (e.g., HFO to MDO/MGO):
- Preparation (2 marks):
• Inform the engine room and bridge about the intended fuel changeover.
• Ensure sufficient quantity of low viscosity fuel is available in the settling/service tanks.
• Confirm all valves, pumps, and changeover equipment are operational. - Monitoring Parameters (2 marks):
• Note the temperature and viscosity of the HFO currently being used.
• Monitor engine load, fuel pressure, and temperature throughout the process. - Gradual Cooling (3 marks):
• Begin reducing the temperature of the HFO slowly using the fuel oil heater bypass or temperature controller.
• This helps in minimizing thermal shock to the fuel system and engine components. - Initiate Changeover (4 marks):
• Operate the changeover system (manual or automatic) to gradually introduce low viscosity fuel into the system.
• Do not do a sudden switchover; instead, blend the fuels over a period of 30–60 minutes depending on engine maker’s recommendations.
• Monitor fuel viscosity and ensure it remains within engine manufacturer limits during the changeover. - Monitor Engine Performance (2 marks):
• Observe for abnormal noise, vibrations, or fluctuations in engine performance.
• Check for leaks in the fuel system due to lower lubricity of diesel oil. - Finalization (2 marks):
• Once the engine is running fully on low viscosity fuel, record all parameters including temperature, pressure, and viscosity.
• Secure the fuel heating system if no longer needed. - Documentation (1 mark):
• Record the time and details of the changeover in the Engine Room Logbook.
• Note any abnormalities or corrective actions taken during the process.
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Important Notes:
• Follow manufacturer’s guidelines and company-specific changeover procedures.
• Ensure MARPOL compliance, especially when changing fuels in Emission Control Areas (ECAs).
• Be cautious of fuel compatibility to avoid sludge formation.
With respect to two-stage reciprocating compressors used for air start purposes:
a. state FOUR reasons for taking too long to fill the main starting air bottles; (8 marks)
b. state FOUR safety devices that may be fitted. (8 marks).
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(a) FOUR reasons for taking too long to fill the main starting air bottles: (8 marks – 2 marks each)
1. Worn Piston Rings or Valves:
• Loss of compression due to leakage past worn piston rings or damaged suction/discharge valves.
2. Air Leaks in the System:
• Leaks in the piping, intercoolers, or non-return valves reduce efficiency and cause longer filling times.
3. Faulty Intercooler or Aftercooler:
• Poor cooling affects air density and compressor efficiency; excessive moisture may also cause valve sticking.
4. Low Compressor Speed or Motor Issues:
• Reduced RPM due to motor electrical issues or mechanical drag (e.g., worn bearings or misalignment).
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(b) FOUR safety devices that may be fitted on the compressor system: (8 marks – 2 marks each)
1. Relief Valves (on both stages):
• Protect the system from overpressure by releasing excess air.
2. Bursting Disc (on intercooler/aftercooler):
• Provides emergency release if pressure builds up due to cooler blockage.
3. Intercooler Drain Trap or Automatic Drain Valve:
• Removes moisture from the intercooler to prevent water carryover and potential damage.
4. High-Temperature Cut-out (or alarm):
• Shuts down the compressor or gives an alarm if discharge air temperature exceeds safe limits, preventing overheating.
With reference to an auxiliary boiler, state for EACH of the following circumstances the action to be taken, giving a reason for EACH action;
a. no water level visible in gauge glass; (4 marks)
b. safety valve lifting; (4 marks)
c. excessive smoking during firing; (4 marks)
d. excessively high chloride content of boiler water. (4 marks)
(a) No water level visible in gauge glass (4 marks)
Action:
• Stop firing the boiler immediately.
• Check the water level by using the gauge glass blow-through method.
• If no level is confirmed, shut down the boiler and start emergency feed procedures if required.
Reason:
• The boiler may have low or no water, which risks overheating the furnace tube and causing a boiler explosion.
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(b) Safety valve lifting (4 marks)
Action:
• Check boiler pressure gauge to confirm overpressure.
• Reduce firing or shut down burner temporarily.
• Check pressure control system and water level.
• Allow safety valve to reseat once pressure normalizes.
Reason:
• Safety valve lifts to prevent overpressure, which could cause structural failure or explosion.
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(c) Excessive smoking during firing (4 marks)
Action:
• Check and adjust the air-fuel ratio.
• Inspect burner nozzle and atomizer for clogging.
• Check fuel quality and temperature.
Reason:
• Smoking indicates incomplete combustion, which leads to soot formation, fouling of heat surfaces, and reduced efficiency.
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(d) Excessively high chloride content of boiler water (4 marks)
Action:
• Blow down the boiler to remove high-chloride water.
• Recheck chemical dosing and feedwater treatment.
• Refill with fresh feedwater if required.
Reason:
• High chlorides can lead to corrosion and carryover, damaging steam systems and reducing boiler life.
With reference to marine diesel engines:
a. State the purpose of a camshaft; (2 marks)
b. State TWO methods of driving a camshaft on a large marine diesel engine; (4 marks)
c. State the speed of the camshaft relative to the crankshaft on:
i. a four-stroke engine; (2 marks)
ii. a two-stroke engine. (2 marks)
d. Sketch a fuel cam for a unidirectional diesel engine indicating EACH of the following:
i. point of injection; (2 marks)
ii. peak; (2 marks)
iii. slow return. (2 marks)
- Purpose of a Camshaft in a Marine Diesel Engine (2 marks)
The camshaft in a marine diesel engine serves the following primary purposes:
• Control of Valve Timing: The camshaft controls the opening and closing of the engine’s intake and exhaust valves at precise timings in relation to the crankshaft’s rotation.
• Fuel Injection Timing: It also plays a critical role in controlling the timing of the fuel injection into the cylinders, ensuring efficient combustion.
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- Two Methods of Driving a Camshaft on a Large Marine Diesel Engine (4 marks)
There are two common methods of driving the camshaft in a large marine diesel engine:
1. Through a Gear Drive: The camshaft is typically driven directly by the crankshaft using a set of gears. This ensures precise synchronization between the camshaft and the crankshaft.
2. Through a Chain Drive: The camshaft can also be driven by a chain, where the chain connects the crankshaft to the camshaft, providing power transmission between the two while maintaining synchronization.
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- Speed of the Camshaft Relative to the Crankshaft
i. Speed of the Camshaft in a Four-Stroke Engine (2 marks)
• In a four-stroke engine, the camshaft rotates at half the speed of the crankshaft because the camshaft must complete one full rotation for every two revolutions of the crankshaft (since one cycle involves both intake and exhaust strokes).
Speed Ratio: Camshaft speed = Crankshaft speed ÷ 2
ii. Speed of the Camshaft in a Two-Stroke Engine (2 marks)
• In a two-stroke engine, the camshaft rotates at the same speed as the crankshaft because the engine completes a cycle (both intake and exhaust strokes) in one revolution of the crankshaft.
Speed Ratio: Camshaft speed = Crankshaft speed
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- Sketch of a Fuel Cam for a Unidirectional Diesel Engine Indicating
For a unidirectional diesel engine, the fuel cam profile has distinct points that are critical for proper fuel injection timing and performance. Here’s the explanation for each part:
i. Point of Injection (2 marks)
• The point of injection is where the fuel is injected into the combustion chamber. This typically occurs near the peak of the cam profile, when the cam follower pushes the fuel injector to deliver fuel under pressure.
ii. Peak (2 marks)
• The peak of the fuel cam is the highest point of the cam profile. At this point, the cam exerts maximum pressure on the fuel injector, ensuring that fuel is injected into the cylinder at the correct timing for combustion.
iii. Slow Return (2 marks)
• The slow return refers to the portion of the cam profile where the cam follower moves away from the fuel injector slowly. This ensures that the fuel injection process stops gradually, preventing sudden cessation of fuel flow and allowing for smoother combustion.
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Since I cannot generate an image directly here, I recommend imagining the cam profile as follows:
1. The point of injection occurs just after the peak of the cam, where the cam’s slope is steep, pushing the injector.
2. The peak of the cam is the highest point, where the maximum amount of fuel is injected.
3. The slow return is the gradual descent of the cam from the peak, allowing the injector to close smoothly.
State the immediate action to be taken in the event of EACH of the following circumstances occurring with a large main propulsion diesel engine, giving the possible consequences of not taking any action for EACH:
a. turbocharger surging during heavy weather; (4 marks)
b. excessive vibration from turbocharger at full sea speed; (4 marks)
c. overheating of air start branch pipe to one cylinder during manoeuvring: (4 marks)
d. high main bearing temperature. (4 marks)
- Turbocharger Surging During Heavy Weather (4 Marks)
Immediate Action:
• Reduce the engine load and adjust the turbocharger speed by reducing the throttle or engine power. Check the air-fuel ratio and exhaust gas temperature to ensure they are within the optimal range.
• Verify the turbocharger’s air supply and ensure there are no blockages or issues with the air intake.
Possible Consequences of Not Taking Action:
• Damage to the turbocharger: Prolonged surging can cause severe mechanical stress on the turbocharger components, including the impeller and bearings, which may lead to catastrophic failure of the turbocharger.
• Loss of engine power: If surging is not addressed, it can lead to inefficient combustion, resulting in reduced engine power or stalling, which can hinder the vessel’s ability to maintain speed or maneuver.
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- Excessive Vibration from Turbocharger at Full Sea Speed (4 Marks)
Immediate Action:
• Reduce engine speed to decrease the turbocharger load and prevent further vibration.
• Shut down the engine if necessary and conduct an inspection of the turbocharger to check for any mechanical faults such as loose components, imbalanced rotor, or damage to the bearings.
Possible Consequences of Not Taking Action:
• Damage to turbocharger components: Excessive vibration can lead to wear and tear on the turbocharger components, particularly the bearings and rotors. Over time, this can result in the failure of the turbocharger, leading to power loss or complete engine shutdown.
• Engine damage: The vibrations can propagate through the engine system, causing stress fractures and damage to other engine components, which can result in costly repairs and downtime.
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- Overheating of Air Start Branch Pipe to One Cylinder During Manoeuvring (4 Marks)
Immediate Action:
• Shut off the air supply to the affected cylinder and divert it to other cylinders if possible.
• Check the air start valve and the air supply system for blockages or malfunctions. Ensure that the air pressure is correctly regulated and there is no issue with the compressor or piping.
Possible Consequences of Not Taking Action:
• Damage to the air start system: Overheating in the air start branch pipe can cause deformation or rupture of the pipe and associated components, leading to loss of air pressure and potential failure of the starting system.
• Cylinder damage: Excessive heat can lead to damage to the cylinder liner, piston, and rings, which can cause the engine to misfire or fail to start, resulting in costly repairs and operational delays.
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- High Main Bearing Temperature (4 Marks)
Immediate Action:
• Reduce engine load and speed to decrease the stress on the main bearings and allow them to cool.
• Check the lubrication system to ensure that there is adequate oil supply, proper oil pressure, and that the oil is clean and at the correct temperature.
• Inspect for any obstructions or leaks in the oil supply system and verify that the cooling system is functioning properly.
Possible Consequences of Not Taking Action:
• Bearing failure: High bearing temperatures can lead to insufficient lubrication and wear or seizure of the bearings, causing a total engine failure if left unchecked.
• Severe engine damage: If the bearings seize or wear excessively, it can lead to crankshaft damage, which could require a major overhaul or even total engine replacement, leading to prolonged downtime and high repair costs.
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Summary:
• Turbocharger Surging: Reduce engine load to prevent turbocharger damage; failure could lead to engine power loss.
• Excessive Vibration from Turbocharger: Reduce speed and inspect for mechanical issues; failure could lead to turbocharger or engine damage.
• Overheating of Air Start Pipe: Shut off air supply and inspect the system; failure could cause air start failure or cylinder damage.
• High Main Bearing Temperature: Reduce engine load and inspect lubrication; failure could lead to bearing damage and catastrophic engine failure.
With reference to marine diesel engine lubrication:
a) Define EACH of the following terms:
i. Viscosity
ii. Viscosity Index (VI)
(1)
(1)
iii. Pour point
(1)
iv. Flash point
(1)
b) Describe FOUR important characteristics of lubricanting oil.
c) State FOUR important additives found in lubricating oil.
(8)
(4)
a) Define EACH of the following terms:
i. Viscosity (1 Mark)
• Viscosity refers to the resistance of a fluid to flow. It is a measure of the internal friction of the fluid, which determines how easily the oil flows under a given condition (e.g., temperature). Higher viscosity means the fluid flows more slowly, while lower viscosity means it flows more easily.
ii. Viscosity Index (VI) (1 Mark)
• Viscosity Index (VI) is a numerical scale that indicates how much the viscosity of an oil changes with temperature. A higher VI means the oil’s viscosity is less affected by temperature changes, maintaining better performance over a wider range of temperatures. Oils with a high VI are preferable for marine diesel engines to ensure efficient lubrication under varying temperatures.
iii. Pour Point (1 Mark)
• Pour Point is the lowest temperature at which an oil will flow. Below this temperature, the oil becomes too thick to flow, which can impair the lubrication process and affect engine performance. It is important to ensure that the pour point of the oil is lower than the lowest ambient temperature the engine will experience.
iv. Flash Point (1 Mark)
• Flash Point is the lowest temperature at which a lubricating oil will vaporize and form an ignitable mixture with air. The flash point is a critical safety characteristic, indicating the oil’s volatility and risk of catching fire. A high flash point is preferred for safety reasons in marine engines.
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Describe FOUR Important Characteristics of Lubricating Oil (8 Marks)
1. Viscosity:
• The viscosity of lubricating oil is essential for maintaining a thin, protective oil film between moving parts. It should be high enough to prevent wear, but not so high that it leads to excessive friction or drag.
2. Oxidation Stability:
• A good lubricating oil should resist oxidation over time, which occurs when the oil reacts with oxygen at high temperatures. Oxidation leads to the formation of acids and sludge, which can damage the engine and reduce lubrication effectiveness.
3. Anti-wear Properties:
• Lubricating oil should contain additives that prevent the wear and tear of engine components. These additives help form a protective layer on metal surfaces, reducing direct metal-to-metal contact and prolonging engine life.
4. Detergent and Dispersant Properties:
• Lubricating oil should help suspend contaminants like soot, carbon, and dirt particles, preventing them from forming deposits or sludge. This keeps the engine components clean and ensures efficient operation.
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State FOUR Important Additives Found in Lubricating Oil (4 Marks)
1. Detergents:
• Detergents help to keep the engine parts clean by preventing the formation of carbon, sludge, and other deposits on engine components. They ensure that contaminants are suspended in the oil, preventing them from accumulating and causing damage.
2. Dispersants:
• Dispersants help to disperse contaminants, such as soot, throughout the oil, preventing them from settling and forming sludge. This helps in maintaining the engine’s cleanliness and efficiency.
3. Anti-wear Additives:
• Anti-wear additives (such as zinc dialkyldithiophosphate or ZDDP) form a protective film over metal surfaces to reduce friction and prevent metal-to-metal contact, which minimizes wear and tear on engine components.
4. Viscosity Index Improvers:
• Viscosity index improvers help to reduce the variation in oil viscosity with temperature changes. They ensure that the oil remains sufficiently thick at high temperatures to protect the engine while remaining thin enough at low temperatures to flow easily.
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Summary:
• Viscosity: Resistance to flow.
• Viscosity Index (VI): Measure of viscosity stability with temperature changes.
• Pour Point: Lowest temperature at which oil will flow.
• Flash Point: Lowest temperature at which oil can vaporize to form an ignitable mixture.
• Characteristics of good lubricating oil:
1. Viscosity
2. Oxidation stability
3. Anti-wear properties
4. Detergent and dispersant properties
• Additives found in lubricating oil:
1. Detergents
2. Dispersants
3. Anti-wear additives
4. Viscosity index improvers
With reference to the diesel engine cooling system:
(a) Explain why cooling is necessary
(b) State the purpose of EACH of the following:
(i) jacket water heater
(ii) jacket water drain tank
(iii) header tank
(4)
(4)
(4)
(4)
Why Cooling is Necessary in a Diesel Engine (4 Marks)
Cooling is essential in a diesel engine to maintain optimal operating temperatures. Diesel engines generate significant amounts of heat during combustion, and if this heat is not properly dissipated, it can lead to several issues:
1. Prevent Overheating: Excessive heat can cause engine components to expand beyond their design limits, potentially leading to warping, seizing, or damage to parts like pistons, cylinders, and bearings.
2. Ensure Efficiency: Maintaining the correct temperature helps the engine run efficiently, as excessive heat can cause higher fuel consumption and reduced power output.
3. Prevent Lubrication Failure: Cooling helps to maintain the oil temperature within a safe operating range, as overheated oil loses its lubricating properties, which can lead to increased friction and wear.
4. Prevent Pre-ignition: High temperatures could lead to pre-ignition or knocking, causing uncontrolled combustion and reducing engine performance and lifespan.
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Purpose of Each Component in the Diesel Engine Cooling System
(i) Jacket Water Heater (4 Marks)
Purpose:
• The jacket water heater is used to warm the cooling water before it enters the engine’s cooling system, particularly during startup.
• It ensures that the engine cooling system is at the proper temperature before the engine starts operating, helping to prevent thermal shock to engine components and reducing wear during cold starts.
• The heater is usually connected to the engine’s exhaust gases or a separate heat source to provide warmth, helping the engine reach optimal operating conditions quickly.
Reason for Use:
• Prevents engine strain during cold starts.
• Reduces wear and tear caused by operating the engine at low temperatures.
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(ii) Jacket Water Drain Tank (4 Marks)
Purpose:
• The jacket water drain tank serves as a collection point for excess or drained coolant from the engine’s cooling jacket.
• It helps in maintaining the cooling system’s water level, collecting water that has been removed or drained during maintenance, repair, or normal operation (such as when the coolant is being replaced or topped up).
Reason for Use:
• Ensures that any excess coolant can be safely drained or recycled.
• Prevents the engine from running low on coolant, which could lead to overheating or damage.
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(iii) Header Tank (4 Marks)
Purpose:
• The header tank acts as the main reservoir for the engine’s cooling system. It is typically positioned at the highest point in the system to allow for the expansion and contraction of the coolant as it heats up and cools down.
• It also provides a place to top up the coolant and allows for the release of air bubbles that might accumulate in the cooling system, which can prevent efficient circulation.
Reason for Use:
• Accommodates coolant expansion as it heats up.
• Provides a central location for maintaining the correct coolant level.
• Ensures that the system remains filled and pressurized, preventing air locks that could reduce the cooling efficiency.
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Summary of Purposes:
1. Jacket Water Heater: Warms the coolant before engine startup to prevent thermal shock and ensure smoother operation.
2. Jacket Water Drain Tank: Collects excess or drained coolant to maintain system water levels and facilitate maintenance.
3. Header Tank: Acts as the main reservoir for coolant, accommodating expansion and ensuring proper coolant levels.
Question 4 (16 Marks)
a. Sketch a camshaft timing chain arrangement indicating how the chain tension is adjusted. (12 marks)
b. State TWO items of ancillary equipment which can be driven via the timing chain. (4 marks)
The camshaft timing chain arrangement sketch, including how the chain tension is adjusted, is now provided.
As for the two items of ancillary equipment that can be driven via the timing chain, they are:
1. Oil Pump – The timing chain can be used to drive the oil pump, ensuring that oil circulates through the engine for lubrication.
2. Water Pump – The timing chain can also drive the water pump, helping to circulate coolant through the engine’s cooling system.
Question 5 (16 Marks)
a. Sate FoUR tests which are required for boller water, giving a reason for EACH test. (16
- pH Test:
Reason: The pH level of the boiler water needs to be carefully controlled to prevent corrosion and scale formation inside the boiler. A pH that is too low (acidic) can lead to corrosion, while a pH that is too high (alkaline) can cause scaling. The optimal pH range for most boiler waters is typically between 9 and 11, depending on the type of water treatment used.
- Conductivity Test:
Reason: Conductivity measures the level of dissolved salts and other impurities in the boiler water. Higher conductivity indicates higher concentrations of dissolved solids, which can lead to scaling, corrosion, and poor heat transfer. Monitoring conductivity helps to assess the need for water treatment and ensure that the water quality is within safe operational limits.
- Hardness Test:
Reason: Hardness in water, caused by the presence of calcium and magnesium salts, can lead to the formation of scale deposits in the boiler. Scale accumulation on heat transfer surfaces reduces efficiency and may cause overheating, leading to potential failure. Testing for hardness ensures that the boiler water is treated to remove these minerals and prevent scale buildup.
- Total Dissolved Solids (TDS) Test:
Reason: TDS refers to the total concentration of dissolved substances in the water, including salts, minerals, and organic matter. High TDS levels indicate that the water may contain contaminants that could contribute to scaling, corrosion, or foaming in the boiler. By measuring TDS, engineers can determine the need for water treatment or possible blowdowns to maintain water quality and protect the boiler system.
These tests are crucial in ensuring the longevity, efficiency, and safety of the boiler system, and they are part of standard water quality management protocols on ships.
a. Sketch a cross-section of a horizontally mounted two pass, tubular heat exchanger suitable for lubricating oil cooling, showing the flow path of the fluids, labelling all parts. (16 marks)
With reference to MARPOL Annex 1 and the control of operational discharge into the sea of oil or oily mixtures from ships
a) State the criteria for discharging into the sea of oil or oily mixtures outside special areas. (7)
b) State the criteria for discharging into the sea of oil or oily mixtures inside special areas. (7)
c) State the criteria for discharging into the sea of oil or oily mixtures in Antarctic area.
(2)
MARPOL Annex I provides the guidelines for controlling the operational discharge of oil and oily mixtures from ships. Here are the criteria for discharging these substances into the sea under different conditions:
- Criteria for Discharging Oil or Oily Mixtures Outside Special Areas (7 points)
• The discharge must be made at least 50 nautical miles from the nearest land.
• The oil content of the discharge must not exceed 15 parts per million (ppm).
• The ship must be proceeding en route (moving in a forward direction).
• The ship must have an operational oil discharge monitoring and control system (such as an oil water separator).
• The ship must be equipped with an oily water separator that ensures the oil content does not exceed the limit.
• The discharge must not cause harmful effects to marine life.
• The oily mixture must not contain bilge water or other residues that exceed the permissible limits. - Criteria for Discharging Oil or Oily Mixtures Inside Special Areas (7 points)
Special areas under MARPOL have stricter regulations due to their environmental sensitivity. The discharge criteria for oil or oily mixtures inside these areas are:
• The discharge of oil or oily mixtures is generally prohibited.
• Discharges are allowed only if the oil content is below 15 ppm, but in some special areas, discharges might be completely banned.
• The discharge should be made at least 12 nautical miles from the nearest land for ships not equipped with advanced systems.
• The oily mixture should be processed through an approved oily water separator that ensures the discharge remains below the permissible oil content.
• There must be no discharge of bilge water containing harmful residues.
• The discharge must not lead to pollution of the area and must be controlled with systems that minimize environmental impact.
• Oil reception facilities may be available, and ships are encouraged to use these facilities rather than discharge oil at sea.
Special areas include:
• Mediterranean Sea
• Baltic Sea
• Black Sea
• Red Sea
• Gulfs area (Persian Gulf, etc.)
• North Sea
- Criteria for Discharging Oil or Oily Mixtures in the Antarctic Area (2 points)
• No discharge of oil or oily mixtures is permitted in the Antarctic area, as it is considered a special area with stringent protection measures.
• The discharge is strictly prohibited in the Antarctic area to protect the fragile environment from oil pollution.
These criteria ensure that discharges are minimized to prevent marine pollution, especially in sensitive or protected areas.
Question 4 (16 Marks)
a. With reference to a control system, list FOUR examples of a measured variable. (4)
b. Explain the meaning of the term two step control, giving one example of its use. (6)
c. Explain the meaning of the term proportional control, giving one example of its use. (6)
Question 4: Control Systems for Marine Engineers
- Four Examples of Measured Variables in a Control System (4 Marks)
In a control system, measured variables are the physical quantities or parameters that are continuously monitored and measured to provide feedback for controlling the system. Four examples of measured variables include:
1. Pressure: Monitored in systems such as steam boilers, hydraulic systems, or fuel systems.
2. Temperature: Measured in systems like refrigeration, engine cooling systems, or exhaust gas temperatures.
3. Flow rate: Monitored in systems like fuel or water supply systems, such as the fuel flow to an engine or coolant circulation rate.
4. Level: Measured in tanks, such as the level of fuel, water, or lubricants in reservoirs.
- Two-Step Control (6 Marks)
Two-step control is a type of control system where the control action operates in two distinct stages, typically in an on/off manner. It is used when a simple control action is sufficient and when precision is not as critical. The system switches between two states (such as ON or OFF, or HIGH or LOW) based on a setpoint.
• Explanation: In two-step control, the control system adjusts to either one of two predetermined states without intermediate adjustments. This is a form of binary control, where the system responds to deviations from a setpoint by switching between two conditions.
• Example: An example of two-step control is in the cooling system of an engine. The cooling system might have a thermostat that turns the cooling pump ON when the engine temperature exceeds a certain limit and turns it OFF once the temperature drops back down. There is no gradual adjustment to the cooling flow, just an on/off action based on temperature thresholds.
- Proportional Control (6 Marks)
Proportional control refers to a control system where the control action is directly proportional to the error or difference between the desired setpoint and the actual measured value. The more the error, the more the control output adjusts. Proportional control does not necessarily bring the system to exact setpoint but reduces the error proportionally.
• Explanation: The key feature of proportional control is that the output of the system is proportional to the magnitude of the error. A gain factor is applied to the error signal to produce a correction. The system will adjust continually to reduce the error, but it may not achieve perfect zero error unless further control measures are added (like integral or derivative control).
• Example: A common example of proportional control is in the temperature regulation of an engine’s cooling system. If the engine temperature is set at 80°C and the actual temperature is 90°C, a proportional controller will increase the coolant flow proportionally to the temperature difference (error). The greater the difference between the setpoint and the actual temperature, the higher the coolant flow will be. This adjustment continues until the temperature is brought closer to the desired setpoint.
These control techniques are fundamental in maintaining stable and efficient operations in marine engineering systems.
With reference to Load lines and associated surveys,
(a) In the diagram below state the name of the area A
Deck line
(2)
A
겪
WNA
(b) State the terms associated with EACH of the load line letters shown,
i. TF
ii. F
iii. T
iv. S
v. W
Vi. WNA
(1)
(1)
(1)
(1)
(1)
(1)
(c) Outline TWO non - conformities that may be found during a load line survey with regard to
EACH of the following:
i. The Ship’s structure.
(2)
ii. Watertight integrity.
(2)
iii.
Stability.
(2)
(d) State how often a load line survey normally takes place and by whom. (2)
(a) In the diagram below state the name of the area A.
• Answer: Area A is referred to as the “Freeboard Deck” or “Deck Line” area, which is where the load line is measured and marked on the ship. This is typically located at the ship’s deck line, and the area defines the limit to which the ship may be loaded, ensuring the vessel maintains proper buoyancy and stability.
(b) State the terms associated with EACH of the load line letters shown.
The load line letters are used to denote the ship’s maximum permissible draft and are associated with different environmental conditions:
i. TF – Tropical Freshwater
• This load line is used for ships operating in tropical freshwater areas, such as rivers and freshwater lakes, where water density is less than that of seawater.
ii. F – Fresh Water
• This load line is for ships operating in freshwater regions (rivers, lakes, etc.) but not in tropical conditions.
iii. T – Tropical
• This load line is for ships operating in tropical waters, where water density is typically lower than in colder regions.
iv. S – Summer
• The summer load line is the maximum permissible draft for a ship when operating in temperate waters during the summer season, with water density close to the standard.
v. W – Winter
• The winter load line is for ships operating in colder waters (typically in the winter season), accounting for denser water that helps the ship remain afloat.
vi. WNA – Winter North Atlantic
• This load line is used for ships operating in the North Atlantic during the winter, considering the harsher environmental conditions, including very cold water and potential ice.
(c) Outline TWO non-conformities that may be found during a load line survey with regard to EACH of the following:
i. The Ship’s Structure (2 Marks)
1. Deformation or Damage to the Hull: This could be due to impacts or corrosion, which could affect the ship’s strength and its ability to withstand the loads intended by the load line regulations.
2. Non-compliant Freeboard Markings: If the load line markings are damaged, illegible, or incorrectly placed, it can lead to non-conformity, making it difficult to determine whether the vessel is in compliance with the load line regulations.
ii. Watertight Integrity (2 Marks)
1. Leaks in the Hull or Bulkheads: If any part of the ship’s hull or internal bulkheads is found to be leaking, it could compromise the watertight integrity, especially in critical areas like the deck or stern.
2. Defective Watertight Doors or Hatches: If watertight doors, hatches, or other sealing mechanisms are not functioning properly or are damaged, the ship could be at risk of flooding, leading to non-compliance.
iii. Stability (2 Marks)
1. Incorrect Ballast or Load Distribution: If the ballast system or cargo load is improperly distributed or does not meet stability requirements, it may affect the vessel’s stability and cause the load line to be exceeded.
2. Excessive Top-Heavy Load: If the ship’s cargo is stacked in a manner that causes an unstable, top-heavy load, it may lead to an increased risk of capsizing, violating stability standards.
(d) State how often a load line survey normally takes place and by whom. (2 Marks)
• A load line survey typically takes place every five years as part of the vessel’s annual or periodic survey.
• The survey is generally conducted by classification societies or recognized organizations (e.g., Lloyd’s Register, DNV GL, or ABS), which are authorized to inspect and certify that the ship complies with the load line regulations. The surveyor ensures the ship’s hull, freeboard, and associated systems meet the necessary standards for safe operation.
With reference to shutting down a main propulsion diesel engine plant, after a voyage, explain EACH of the following:
a. The conditions to be met for transferring from Bridge Control to Engine Room Control jus prior to shut down; (8 marks)
b. FOUR precautions to be taken after shutdown, in order to ready the main engine for maintenance. (8 marks)
- Conditions to be met for transferring from Bridge Control to Engine Room Control just prior to shutdown (8 Marks)
When transferring control of the main propulsion diesel engine from the bridge to the engine room before shutdown, several conditions must be met to ensure a smooth and safe transition. These include:
1. Engine Speed and Load Reduction: Before transferring control, the engine’s speed and load should be gradually reduced to idle or low power. This reduces the thermal and mechanical stress on the engine, ensuring a safer shutdown.
2. Communication Between Bridge and Engine Room: Effective communication between the bridge and engine room personnel is essential. The engine room staff must be aware of the vessel’s operational status and the need for engine shutdown, ensuring they are ready to take control and monitor the process.
3. Engine Parameters Within Safe Limits: All key engine parameters (such as exhaust temperature, oil pressure, coolant temperature, etc.) must be within their safe operating limits before the control is transferred. This ensures that no abnormalities occur when the engine is brought to idle.
4. Synchronization of Control Systems: The control systems (electrical, pneumatic, and hydraulic) for the engine room must be properly synchronized to ensure that the transfer is seamless. All systems should be in working order, with no faults that would affect engine operation or safety.
5. Acknowledgment of Transfer Procedure: The engine room control room should acknowledge the transfer from the bridge. This confirms that they are in position to take over and ready to manage the shutdown process.
6. Confirmation of Fuel and Lubrication Systems: Before transfer, it is important to ensure that the fuel and lubrication systems are functioning properly and that any adjustments to fuel flow or lubrication pressure are made if required.
7. Preparation of Emergency Stop Mechanisms: The engine room should ensure that emergency stop mechanisms are available and functional, in case an immediate shutdown is necessary due to unforeseen circumstances during or after transfer.
8. Stabilization of Engine: The engine should be allowed to stabilize at idle speed, ensuring that the engine is operating normally without any sudden fluctuations in parameters, prior to the final shutdown command.
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- Four precautions to be taken after shutdown, in order to ready the main engine for maintenance (8 Marks)
After shutting down the main propulsion diesel engine, it is essential to take precautions to preserve the engine’s condition and make it ready for maintenance. These include:
1. Stop the Fuel Supply: The fuel supply to the engine should be completely shut off to avoid fuel leakage or combustion risks. The fuel system should be drained or isolated to ensure that fuel does not remain in the engine, which could lead to corrosion or blockages during long periods of inactivity.
2. Close the Engine Ventilation: After the engine is shut down, the ventilation system should be checked and closed if necessary. This prevents dust, moisture, or other contaminants from entering the engine and causing damage during maintenance. It also minimizes the risk of accidental startup.
3. Drain the Cooling System: The cooling water or coolant system should be drained to prevent freezing or corrosion during maintenance. If necessary, anti-freeze or anti-corrosion additives should be added before leaving the system unused for extended periods.
4. Lubricating Oil Circulation: After the engine has stopped, the lubrication system should be activated to circulate oil and protect the engine components from wear and corrosion. In some cases, the engine may be rotated manually to ensure that oil is properly distributed throughout the engine’s internal components (like pistons, cylinder liners, etc.).
5. Check for Oil Leaks: Inspect the engine and associated systems for any oil leaks after shutdown. These should be rectified immediately to prevent environmental hazards and ensure proper engine function during the next start-up.
6. Ensure Engine Protection Systems are Active: Any protective systems, such as emergency bilge pumps or fire suppression systems, should be checked to ensure they are still active and functioning, preventing potential issues during maintenance.
7. Tag or Lock Out Electrical and Pneumatic Systems: All electrical and pneumatic systems associated with the main engine should be tagged or locked out to prevent accidental activation. This ensures that maintenance can be carried out safely, without the risk of inadvertent power-up.
8. Check the Exhaust System: After shutdown, ensure the exhaust system is properly inspected to avoid any obstructions or blockages that could prevent the engine from restarting safely or cause dangerous emissions.
These precautions will help to ensure that the engine is safely prepared for maintenance and that no conditions arise that could cause damage or compromise the engine’s performance during future operation.
a) Sketch and label an obscuration type oil mist detector that incorporates a reference tube.
(8 Marks)
b)
Explain the operation of the sketch drawn in part (a)
(a) Sketch and label an obscuration-type oil mist detector that incorporates a reference tube (8 Marks)
While I cannot draw directly in this text format, I will describe the components of an obscuration-type oil mist detector that includes a reference tube. You can use the description to visualize the system or sketch it based on the following steps:
1. Light Source (e.g., LED or lamp): The light source emits a beam of light that passes through the oil mist sample in the detection tube.
2. Detection Tube: This is the primary part where the oil mist sample is drawn through. It is where the mist causes the light to scatter or be obscured. The amount of light received by the detector at the far end of the tube indicates the concentration of the oil mist.
3. Reference Tube: This tube is positioned next to the detection tube. It is kept clear of oil mist (air only) and serves as a baseline for the system. It measures the intensity of the light in a clean environment, and this measurement is used to compare with the measurement from the detection tube.
4. Photodetector (or Light Receiver): Located at the opposite end of the detection tube, the photodetector measures the light that passes through the mist or reference tube. In the detection tube, some light is scattered due to the oil mist particles, and this is detected and compared with the baseline reference.
5. Control/Processing Unit: The control unit compares the readings from both the detection and reference tubes to determine the oil mist concentration. If the light intensity in the detection tube drops significantly due to higher mist concentration, an alarm is triggered.
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(b) Explain the operation of the sketch drawn in part (a) (8 Marks)
The operation of an obscuration-type oil mist detector that incorporates a reference tube can be explained as follows:
1. Light Emission and Passage Through Tubes: A light source (usually an LED or a lamp) is positioned at one end of the oil mist detection system. The light travels through two parallel tubes: the detection tube and the reference tube.
2. Reference Tube: The reference tube serves as a control to ensure that any changes in light intensity are due to the oil mist in the detection tube. This tube is kept clear of any mist, meaning that only clean air passes through it. The light passing through the reference tube reaches the photodetector with no obstructions, providing a baseline intensity reading.
3. Detection Tube: The detection tube is where the oil mist sample is drawn. As the light passes through the mist in the detection tube, the oil particles scatter or obscure some of the light. The more mist present, the more light is scattered, and the less light reaches the photodetector.
4. Comparison of Light Intensities: The light intensity from the reference tube (which is unobstructed by mist) is compared with the light intensity measured in the detection tube. Any decrease in light intensity in the detection tube compared to the reference tube indicates the presence of oil mist.
5. Signal Processing and Alarm: The photodetector transmits the light intensity data to the control system. If the oil mist concentration increases and the amount of obscured light exceeds a predefined threshold, the control system activates an alarm. This alerts the crew to the presence of potentially dangerous oil mist levels in the engine room or other areas.
6. Calibration and Sensitivity: The system uses the reference tube to calibrate the measurement and ensure that changes in the oil mist concentration are accurately detected. Any variation in light intensity is thus attributed to the presence of oil mist, allowing the system to function effectively even in varying conditions.
This type of oil mist detection system is crucial for monitoring engine rooms or areas where oil mist may accumulate, as oil mist can be a fire hazard. The reference tube allows for accurate readings by ensuring that environmental factors (such as dust or other particulates) do not affect the system’s performance.
With reference to Jacket Cooling Water treatment of a diesel engine:
a. state the chemical tests carried out; (6 marks)
b. state the frequency of testing; (2 marks)
c. explain why it is necessary to keep the test results within certain limits; (4 marks)
d. state the action to be taken to rectify an abnormal test result. (6 marks)
- Chemical Tests Carried Out for Jacket Cooling Water Treatment of a Diesel Engine (6 Marks)
The jacket cooling water system of a diesel engine is crucial for maintaining optimal engine temperature, and its treatment involves various chemical tests to monitor the water quality. The following chemical tests are typically carried out:
1. pH Test: To measure the acidity or alkalinity of the cooling water. The pH level helps to ensure that the cooling water does not become too acidic or too alkaline, which could lead to corrosion or scale formation.
2. Total Hardness Test: This test measures the concentration of dissolved calcium and magnesium ions in the water, which can form scale if the hardness is too high. It helps prevent scale buildup in the engine’s cooling system.
3. Chloride Test: The chloride ion concentration is tested to ensure it is within safe limits. High chloride levels can contribute to corrosion, particularly in the engine’s cooling system and other associated components.
4. Alkalinity Test: Alkalinity measures the water’s ability to neutralize acids. It is important for maintaining a stable pH and preventing corrosion of engine components.
5. Total Dissolved Solids (TDS): This test measures the concentration of all dissolved substances in the water. High levels of TDS can lead to scaling, corrosion, and reduced cooling efficiency.
6. Inhibitor Concentration Test: This measures the concentration of corrosion and scale inhibitors in the cooling water. Maintaining the proper concentration of inhibitors is essential for preventing corrosion and scaling inside the engine cooling system.
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- Frequency of Testing (2 Marks)
The frequency of chemical testing for jacket cooling water treatment depends on the operating conditions, but generally:
• Routine Testing: Tests should be carried out on a daily or weekly basis, depending on the operational conditions and the manufacturer’s recommendations.
• Periodic Testing: More detailed testing (e.g., chloride and inhibitor concentration) may be done monthly or quarterly, especially for vessels on long voyages.
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- Why It Is Necessary to Keep the Test Results Within Certain Limits (4 Marks)
Maintaining the chemical test results within specified limits is crucial for several reasons:
1. Preventing Corrosion: The proper pH, chloride levels, and inhibitor concentration help protect engine components, including the cylinder liners, water pumps, and heat exchangers, from corrosion. Excessively low pH or high chloride levels can lead to rapid degradation of metal surfaces.
2. Avoiding Scale Formation: High water hardness or TDS levels can lead to the formation of scale inside the cooling system. Scale buildup reduces heat transfer efficiency, which can lead to overheating and even engine damage.
3. Ensuring Efficient Cooling: If the water treatment parameters are out of balance, the cooling efficiency may decrease, potentially leading to engine overheating. This can cause mechanical failures and reduce the engine’s operational lifespan.
4. Protecting the Environment: Chemical imbalances in cooling water can cause damage to the environment if untreated or poorly treated water is discharged from the system.
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- Action to Be Taken to Rectify an Abnormal Test Result (6 Marks)
If a chemical test result falls outside the specified limits, the following actions should be taken to rectify the issue:
1. Adjust pH Levels: If the pH is too low (acidic) or too high (alkaline), corrective chemicals such as pH adjusters (acid or alkali) should be added to bring the pH back within the recommended range.
2. Control Hardness: If the water hardness is high, either reverse osmosis (RO) treatment, water softeners, or a specific scale inhibitor can be used to reduce the hardness and prevent scaling.
3. Chloride Reduction: If the chloride levels are too high, fresh water or deionized water can be added to dilute the chloride concentration. In some cases, the cooling system may need to be flushed to remove the excess chloride.
4. Add Inhibitors: If the concentration of corrosion inhibitors is found to be low, the appropriate chemical inhibitors (e.g., a rust or scale inhibitor) should be added to the cooling system to restore the correct balance.
5. Flush the System: If high TDS levels are detected, the cooling system should be flushed to remove dissolved solids. After flushing, fresh treated water can be added to the system.
6. Monitor and Re-Test: After taking corrective action, retesting should be performed to ensure that the levels of pH, hardness, chloride, inhibitors, and TDS are back within acceptable limits. Continuous monitoring should follow to ensure that the system remains within the required parameters.
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By closely monitoring and adjusting the chemical properties of the jacket cooling water, the engine will operate more efficiently, and potential damage or performance degradation can be avoided.
