Marine Main Engine Operating Principles

Main Engine

• The main engine, also known as the marine engine, is the powerhouse of a ship and is responsible for converting fuel energy into mechanical energy.
• The engine is usually located at the bottom or stern of the ship in the engine room.
• The most common type of main engine is the diesel engine.
• The operating principle of the main engine involves four stages: intake, compression, combustion, and power.
• Components of the main engine include:
  • Engine block: the main housing containing cylinders, pistons, and crankshafts.
  • Cylinders: chambers where fuel is burned and pistons move up and down.
  • Pistons: components that compress the air-fuel mixture and transmit the force to the crankshaft.
  • Crankshaft: a rotating shaft that converts the reciprocating motion of pistons into rotary motion.
  • Camshaft: a shaft that operates valves that control air intake and exhaust release.
  • Valves: open and close to allow air and exhaust gases in and out of the cylinders.
  • Fuel injection system: delivers fuel into the cylinders at the right moment.
  • Turbocharger (optional): uses exhaust gases to compress incoming air, increasing engine power.

Boiler

• A ship's boiler is a giant kettle that heats water to create high-pressure steam.
• The steam is crucial for powering various onboard systems, including main propulsion, auxiliary machinery, and heating.
• Components of the boiler include:
  • Boiler shell: a strong, steel chamber that houses everything else.
  • Tubes: carry water or hot gases, depending on the boiler type.
  • Burner: injects fuel (usually oil) into a furnace where it combusts.
  • Economizer: preheats feedwater entering the boiler using exhaust gases, making the boiler more efficient.
  • Superheater: heats steam beyond its saturation point, creating superheated steam that's more efficient for turbines.
  • Feedwater pump: delivers water to the boiler.
  • Safety valves: release excess pressure to prevent boiler explosions.
• There are two main types of boilers: water-tube and fire-tube boilers.
• Modern ships use water-tube boilers due to their efficiency and ability to withstand higher pressure.

Generator

• A ship's generator is essentially the power plant responsible for providing electricity to the entire vessel.
• The generator uses the principle of electromagnetic induction to convert mechanical energy from the prime mover into electrical energy.
• Components of the generator include:
  • Prime mover: the engine that spins the rotor (can be a diesel engine or steam turbine).
  • Alternator: the heart of the generator, comprising a rotor and stator.
  • Rotor: a rotating magnet (or electromagnet) that creates a magnetic field.
  • Stator: a stationary ring with coils that produce electricity.
  • Voltage regulator: maintains consistent output voltage.
  • Exciter: supplies direct current (DC) to the rotor's electromagnet if it's used.
• Multiple generators are often installed for redundancy and to handle varying power demands.
• There are two main types of generators: shaft generators and emergency generators.

Fresh Water Generator

• A freshwater generator is a crucial piece of equipment on ships that produces potable water from seawater.
• The generator uses vacuum distillation or reverse osmosis to remove salt and other minerals from seawater.
• Components of the freshwater generator include:
  • Shell: the outer casing of the freshwater generator.
  • Evaporator: a chamber where seawater is heated by steam or hot water.
  • Condenser: a heat exchanger that cools down the hot vapor produced by the evaporator.
  • Demister: a device that removes any entrained saltwater droplets from the vapor.
  • Freshwater pump: transfers the distilled freshwater to a storage tank.
  • Ejector: creates a vacuum in the evaporator.
  • Temperature monitoring devices: monitor the temperature of the seawater, vapor, and freshwater product.
  • Air purge valve: removes air from the freshwater generator.
  • Safety relief valve: relieves pressure in the freshwater generator if it gets too high.
  • Salinometer: measures the salinity of the freshwater product.
• The operating principles of the freshwater generator involve heat and pressure reduction, evaporation and separation, condensation, and demisting.

Oily Water Separator

• An oily water separator (OWS) is a piece of equipment specifically designed for the shipping industry.
• The OWS treats oily bilge water and other oily wastewaters generated by ship operations before discharging the treated water overboard.
• Components of the OWS include:
  • Separation unit: coalescing media, coarse separation compartment, and fine settling compartment.
  • Filter unit: filter or pre-coat filter.
  • Monitoring and control unit: oil content monitor (OCM) and inlet/outlet valves.
• The operating principles of the OWS involve gravity separation, coalescence, and filtration.
• The OWS plays a vital role in protecting the marine environment by preventing oil pollution from ships.### Control Unit and Oily Water Separator
• The control unit regulates the operation of the oily water separator based on OCM readings.
• It can automatically shut down the separator if the oil content exceeds the limit.

Incinerator

• A ship incinerator is a device that burns solid and liquid waste generated during ship operation.
• It is designed to be more environmentally friendly than dumping waste overboard.
• Components: combustion chamber, flue gas scrubber, and stack.
• Operating principles: waste loading, combustion, emission treatment, and emission release.

Pumps

• Pumps are mechanical devices that move fluids (liquids or gases) from one place to another.
• Primary purpose: transfer fluids by creating a pressure difference.
• Operating principle: fluid entry, energy transfer, pressure increase, and fluid flow.
• Types: positive displacement (reciprocating and rotary) and centrifugal pumps.
• Components: impeller/rotor, casing, inlet/suction, outlet/delivery, shaft, and seals.
• Applications on ships: engine cooling, ballast systems, fuel oil transfer, freshwater supply, bilge water removal, and hydraulic systems.

Purifier

• A ship purifier is a device that cleans and separates contaminants from fluids used on the vessel.
• Operating principle: relying on centrifugal force to separate components based on their density.
• Components: bowl, disc stack, gravity disc, and water outlet.
• Applications: fuel oil, lubricating oil, and bilge water.

Air Compressor

• An air compressor on a ship takes in ambient air and squeezes it to a higher pressure.
• Operating principle: air intake, filtration, compression, aftercooling, and storage.
• Components: air intake, air filter, intercooler, compressor element, aftercooler, pressure relief valve, air receiver tank, and discharge valve.
• Types: main air compressor and auxiliary air compressors.

Steering Gear

• The steering gear is responsible for controlling the movement of the rudder, which ultimately changes the ship's direction.
• Operating principle: translating commands from the wheel on the bridge into mechanical movement of the rudder.
• Components: helm, control system, power unit, rudder actuator, and rudder stock.
• Types: hydraulic steering gear, electro-hydraulic steering gear, and vane type.

Sewage Treatment Plant (STP)

• A ship's STP treats wastewater before it's discharged overboard to protect the marine environment.

• Operating principle: wastewater flows into the STP, removing pollutants and meeting regulations.

• Components: screens, primary settling tank, biological treatment tank, secondary settling tank, and disinfection unit.

• Purpose: prevent pollution, comply with regulations, and protect the marine environment.### Sewage Treatment Plant

• Remaining solids (bacteria and decomposed organic matter) settle as sludge at the bottom, while treated effluent (water) rises to the top.

• Disinfection unit: treated effluent is disinfected with chlorine or UV light to eliminate harmful pathogens before discharge.

• Sludge treatment system: removed sludge undergoes further treatment to reduce volume and make it suitable for land disposal or incineration at sea.

Refrigeration System

• Purpose: maintain proper temperature conditions for cargo preservation and crew provisions.
• Components:
  • Compressor: pumps refrigerant gas, raising pressure and temperature.
  • Condenser: cools hot, high-pressure gas, condensing it back into liquid.
  • Expansion valve: reduces pressure of liquid refrigerant, causing it to partially vaporize.
  • Evaporator: absorbs heat from cargo hold or provisions rooms, cooling the space.
• Operating principle:
  1. Low-pressure gas starts as a cool temperature.
  2. Compression: compressor squeezes gas, increasing pressure and temperature.
  3. Condensation: hot gas passes through condenser, releasing heat and condensing back into liquid.
  4. Expansion: liquid refrigerant flows through expansion valve, reducing pressure and causing partial vaporization.
  5. Absorption: cold, low-pressure refrigerant gas absorbs heat from surrounding air.
  6. Cycle restart: warmed, low-pressure gas is drawn back into compressor, restarting the cycle.

Starting Air System

• Purpose: crank large marine diesel engines and get them running.
• Components:
  • Air compressors: compress ambient air to high pressure (31 bars).
  • Air receivers: store compressed air for multiple engine starts.
  • Pilot air system: separate system with lower pressure air for control purposes.
  • Automatic air starting valve: regulates flow of high-pressure air to engine.
  • Starting air distributor: directs compressed air to appropriate engine cylinder.
• Operating principle:
  1. Compressed air storage: air compressors fill receivers with high-pressure air.
  2. Engine preparation: crew ensures engine is ready and safety interlocks are engaged.
  3. Initiating engine start: pilot air system opens path for compressed air to flow to engine.

Fuel Oil System

• Purpose: store, treat, and deliver fuel oil to engines for propulsion and power generation.
• Components:
  • Fuel oil storage tanks: store fuel oil received during bunkering.
  • Transfer pumps: move fuel oil from storage tanks to settling tanks.
  • Settling tanks: allow water and sediment to settle out of fuel oil.
  • Fuel oil heaters: heat fuel oil to improve flow properties and aid purification.
  • Purifiers (centrifuges): remove finer contaminants and water from fuel oil.
  • Service tanks: store purified and heated fuel oil ready for engine use.
• Operating principle:
  1. Bunkering: fuel oil is loaded into storage tanks through deck fill connections.
  2. Transfer and heating: fuel oil is moved to settling tanks, heated, and purified.
  3. Purification: heated oil is fed into centrifuges to remove contaminants and water.
  4. Storage and supply: purified fuel oil is transferred to service tanks and delivered to engines.

Lubricating Oil System

• Purpose: reduce friction and wear between moving engine parts, cool critical components, and clean and remove contaminants.
• Components:
  • Lubricating oil tank (sump): stores engine oil and serves as a collection point for oil returning from engine.
  • Lubricating oil pump: draws oil from sump and pressurizes it for distribution.
  • Oil filter: removes contaminants from oil.
  • Oil cooler: reduces oil temperature after it absorbs heat from engine components.
  • Pressure relief valve: protects system from excessive pressure.
  • Pressure regulator valve: maintains consistent oil pressure throughout engine.
  • Piping system: distributes oil under pressure to various engine components.
• Operating principle:
  1. Oil circulation: lubricating oil pump draws oil from sump and pressurizes it for distribution.
  2. Filtration: oil passes through filter to remove contaminants.
  3. Temperature control: oil flows through oil cooler to reduce temperature.
  4. Pressure regulation: oil pressure is regulated by pressure regulator valve.
  5. Distribution: pressurized oil is delivered to engine components.

Propulsion System

• Purpose: convert energy into mechanical energy that creates thrust to propel the ship forward.
• Components:
  • Prime mover: engine or motor that generates initial power.
  • Power transmission system: transfers power from prime mover to propeller.
  • Propeller: converts rotational energy from shafting into thrust.
• Operating principle:
  1. Energy generation: prime mover generates mechanical energy in the form of rotation.
  2. Power transmission: rotational energy is transmitted through power transmission system.
  3. Thrust generation: propeller converts rotational energy into thrust.

Cooling System

• Purpose: prevent overheating of engines and machinery.
• Components:
  • Seawater pumps: draw in seawater from sea chest.
  • Heat exchangers: devices where seawater absorbs heat from engine or machinery.
  • Piping system: network of pipes that carries seawater throughout system.
  • Strainers: filters that remove debris from seawater to prevent clogging.
  • Expansion tank: absorbs pressure fluctuations in freshwater loop.
• Operating principle:
  1. Direct seawater cooling: seawater is used as direct coolant for engine or machinery.
  2. Central freshwater cooling: freshwater is circulated through closed loop, absorbing heat from engine or machinery.

Control System

• Purpose: navigate, maneuver, and maintain stability of the ship.
• Components:
  • Sensors: continuously gather data on ship's state and surroundings.
  • Control units: compare data to desired course, speed, or operating parameters.
  • Actuators: make adjustments to ship's systems (rudder angle, engine speed, etc.).
• Operating principle:
  1. Sensors gather data on ship's state and surroundings.
  2. Control units compare data to desired parameters and send commands to actuators.
  3. Actuators make adjustments to ship's systems.
  4. Sensors pick up on changes and send updated data back to control units, completing the loop.