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Questions and Answers
What is the maximum allowable discharge rate for oily water on ships?
What component of the fuel primarily controls SOx emissions?
At what RPM does a slow speed diesel engine typically operate?
What is the primary purpose of bearings in a turbine?
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What is the unit of measurement for viscosity?
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What role does zinc serve in a turbine system?
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What does the condensate pump do in a turbine system?
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What is the heat called that is present when water is converted to steam?
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What type of heat is used to create superheated steam in a turbine?
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What component supports the weight of a turbine?
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What happens to pressure and velocity when steam flows through a nozzle in a turbine?
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What is the purpose of the ahead throttle valve in a steam turbine?
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What does the compounding process in a turbine involve?
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Why are reduction gears necessary for turbine operation?
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What is the primary function of a rotor in a steam turbine?
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Where is steam exhausted to after leaving a low pressure turbine?
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What part of the piston absorbs the side thrust?
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In a four-stroke engine, the piston moves from bottom dead center to top dead center during which stroke?
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What mechanism delivers air at positive pressure for combustion and is driven by engine exhaust?
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What happens to the gas turbine engine when the engine speed is greater than the reduction gear speed?
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During the process of atmospheric conditions, what is the theoretical atmospheric pressure?
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What is the role of shaft seals in an engine?
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What type of cycle does a gas turbine operate on?
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What is the function of the connecting rod in a crosshead type engine?
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What does an ejector primarily do?
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What does a static suction lift require?
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Which of the following statements regarding a centrifugal pump is true?
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What contributes to friction head losses in a piping system?
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How is the efficiency of a pump affected as wear continues?
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What is the role of a suction valve in a pump?
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In a double acting pump, how often does it discharge fluid?
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What ensures the positioning of lobes in a rotary impeller?
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What is necessary for a vessel equipped with a fixed pitch propeller to go in reverse?
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What are micro-organisms used for in a biological Marine sanitation device (MSD)?
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What kind of waste is classified as black water?
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Why does oil float on water?
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What is the result of propeller cavitation that causes pitting at the tips of propellers?
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What is the role of a blower in a biological sewage treatment plant?
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What is not an approved method for treating ballast water?
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What type of waste can be discharged overboard more than 12 nautical miles from shore?
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Study Notes
Maximum Allowable Discharge Rates
- Oily water discharge rate not to exceed 15 ppm (parts per million).
Fuel Requirements
- Sulfur content in fuel plays a crucial role in controlling SOx emissions.
- Lower sulfur content in fuel reduces SOx emissions.
Diesel Engine Operation
- Slow speed diesel engines typically run at 100 RPM (revolutions per minute).
Steam Turbine Operation
- Steam flow in a turbine operates from high pressure to low pressure.
- Bearings support the turbine shaft, providing an oil film.
Fluid Properties
- Viscosity: Resistance of a fluid to flow.
- Viscosity is measured in centistokes.
- Innage: Distance from the bottom of a tank to the surface of the liquid.
- Ullage: Distance from the liquid surface to the top of the tank.
Gauges and Measurements
- Bourdon tube gauges are commonly used aboard ships.
- Pressure changes cause the Bourdon tube to straighten, moving the gauge needle.
- Pyrometers measure temperature.
- 2 bar is equivalent to 29 PSI (pounds per square inch).
- 40 liters of lube oil is approximately 10.568 gallons.
- 14 inches of water is equivalent to 0.50578 PSI.
- 900 mm of water is equal to 35.4331 inches of water.
Heat Exchange
- Heat exchange depends on conduction and convection.
- Factors affecting heat exchange rate:
- Tube wall material
- Dirt on tubes
- Heat exchange area
- Fluid film thickness
- Temperature difference
- Zinc acts as a sacrificial metal in turbines, protecting the condenser from wear and tear.
- Condensers remove latent heat and convert vapor to liquid.
- Latent heat is present during the phase change of water to steam.
- Sensible heat is added to increase the temperature of steam, creating superheated steam.
Turbine Components
- Bearings support the weight of the turbine.
- Steam flowing through a nozzle experiences a decrease in pressure and an increase in velocity.
- The ahead throttle valve controls the amount of superheated steam flowing in the ahead direction.
- Compounding combines stages in a turbine to increase power generation.
Turbine Operation
- Steam flows from the high-pressure turbine to the low-pressure turbine in the ahead direction.
- To move a vessel in the astern direction, steam is applied to the stern portion of the low-pressure turbine.
- A flexible I-beam supports the turbine casing for expansion.
Reduction Gears
- Turbines require reduction gears because they operate at high speeds (up to 6000 RPM), which is too fast for direct connection to the propeller.
Steam Turbine Limits
- The material limitations of the turbine components restrict the maximum temperature of the superheated steam.
Internal Turbine Operations
- After passing through a nozzle, steam flows onto the turbine blades.
- Dry steam should not be used in a low-pressure turbine because it can damage the blades.
- The rotor in a steam turbine holds the moving blades and transmits the force to rotate the propellers.
- Steam is exhausted to the main condenser in a low-pressure turbine.
- Radial clearances in steam turbines are maintained by the bearings.
- Glands seal the turbine, preventing air and steam leakage, and maintaining a vacuum in the condenser.
Diesel Engine Cycle
- During the compression stroke, the piston moves upwards, decreasing volume and increasing pressure and temperature.
- Stroke: Distance between top dead center (TDC) and bottom dead center (BDC).
- Crankshaft rotation: 360 degrees in a 2-stroke cycle engine and 720 degrees in a 4-stroke cycle engine.
- In a 4-stroke engine, during the intake stroke, the piston moves from TDC to BDC.
- The wrist pin connects the piston and connecting rod.
- In a 4-stroke engine, the intake and exhaust valves are located in the cylinder head.
- The piston skirt absorbs side thrust.
- The camshaft in a 2-stroke cycle engine turns at the same rate as the crankshaft.
- The camshaft in a 4-stroke cycle engine turns at half the rate of the crankshaft (2 revolutions: 1 camshaft revolution).
- Turbochargers deliver air at positive pressure for combustion and are driven by engine exhaust.
Diesel Engine Components and Operation
- TDC (Top Dead Center): Highest point in the cylinder.
- BDC (Bottom Dead Center): Lowest point in the cylinder.
- In a four-stroke engine, during the exhaust stroke, the piston moves from BDC to TDC.
- In a crosshead-type engine, the piston is connected to the crosshead by the connecting rod.
- The upper part of the piston is called the crown.
- Natural aspiration: Air intake into the cylinder during the intake stroke, driven by the piston moving down and creating a suction.
- The fuel pump meters the fuel for combustion.
Propellers
- Controllable pitch propellers allow for reversing the vessel's direction.
Gas Turbine Components
- A single-shaft gas turbine does not include a power turbine.
- A recuperator or waste heat boiler can be used to extract heat from the exhaust.
Thermodynamic Cycles
- A gas turbine operates on an open cycle.
- A steam turbine operates on a closed cycle.
- A Brayton cycle can be open or closed.
Gas Turbine Clutch
- The SSS (shaft speed sensitive) clutch connects and disconnects the gas turbine from the reduction gear.
- If the engine speed is greater than the reduction gear speed, the clutch engages.
- If the engine speed is less than the reduction gear speed, the clutch disengages.
- Shaft seals prevent oil leakage in the engine.
Compressor
- The two main functions of a compressor:
- Supplying air for combustion
- Cooling components
- A rotor shaft is supported by a bearing.
- During inoculation, air passes through the compressor, increasing pressure and decreasing volume.
- Initial ignition in a gas turbine is initiated by an electric spark igniter.
- A hung start indicates insufficient RPM for combustion.
Atmospheric Conditions
- Theoretical atmospheric pressure at standard conditions: 12 bar.
Pumping Systems
- Pumping systems move fluids from low pressure to high pressure.
- Suction lift: Distance from the liquid level in the tank to the centerline of the pump, when the tank is below the pump.
- Head: From the centerline of the pump to the height of the fluid or pump discharge.
- Pumps with a static suction head require less work than those with a static suction lift to move the same fluid.
- An ejector uses steam or gas to draw liquid upward.
- An eductor has no moving parts.
Centrifugal Pumps
- Centrifugal pumps are not positive displacement pumps.
- Centrifugal pumps require priming, meaning removing air from the casing and filling it with water.
- Cavitation: Formation of air bubbles due to low pressure in the suction line, which can collapse and damage the pump.
Rotary Pumps
- Rotary pumps are positive displacement and self-lubricating pumps.
- Efficiency decreases as wear increases. --
- The discharge capacity of a screw pump can be varied by changing the pitch, length, and number of screws.
Reciprocating Pumps
- Reciprocating pumps are positive displacement.
- A double-acting pump discharges once per stroke and twice per revolution.
- Suction valves open under low pressure in the pump chamber.
- When there is low pressure in the cylinder chamber, the suction valve opens.
- Ejectors use steam or gas, while educators use liquid.
- Lobes in a rotary impeller do not touch and are timed by gears.
Friction Head
- Friction head is the loss of pressure in a system due to:
- Pipe roughness
- Fittings
- Valves
- Pipe length
- Number of turns
Engine Disconnection
- A clutch disconnects the engine from the gearing or maneuvering system.
Shaft Bearings
- A bearing supports the reduction gear shaft.
- Line shaft bearings are found in the shaft alley.
- Hollow shafts are typically found in controllable pitch propellers.
- Stern tube bearings support the tailshaft and the weight of the propeller.
Propeller Rotation
- A right-hand propeller turns clockwise.
- A left-hand propeller turns counterclockwise.
Propeller Types
- Vessels with fixed pitch propellers require the engine to stop completely before going in reverse.
- Controllable pitch propellers change pitch for speed control and reversing.
Propeller Cavitation
- Propeller cavitation that causes pitting on the tips reduces efficiency.
Wastewater Management
- Grey water: Waste from sinks, showers, galleys, etc.
- MSD (Marine Sanitation Device): System for treating sewage.
- Biological MSD uses microorganisms to consume solid waste.
- Maceration: Grinding and chopping sewage into smaller pieces.
- Black water: Sewage.
- Sewage discharge is prohibited within 3 nautical miles from shore.
- Deck wash water with cleaning agents can be discharged overboard inside and outside of special areas.
- Aerosol cans should not be placed in incinerators.
- Incinerator ash cannot be discharged overboard.
- Oil floats on top of water because of the density difference.
- UV light can be used to treat water in some areas instead of chemicals.
- Keep a record of trash disposal in the garbage log.
Oil and Ballast Management
- Oily water is generated from bilge pumping.
- Maceration is not used to treat ballast water.
Sewage Treatment Systems
- Retention systems: Waste is stored in a holding tank until discharge.
- Biological sewage treatment plants require blowers to provide air for the microorganisms.
Waste Disposal Regulations
- Ground food waste can be discharged overboard over 12 nautical miles from shore.
Oil/Water Separation
- Heating an oil/water mixture helps with separation.
Ballast Water Management
- Mixing ballast water to change salinity conditions is not an approved method for ballast water treatment.
- Transfer of nonindigenous species can occur through ballast water operations.
Environmentally Sound Operations
- Reducing whole following resistance helps minimize CO2 emissions.
Lube Oil
- Lube oil cleans, cools, and reduces friction in engines.
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Description
Test your knowledge on marine engineering principles, including maximum allowable discharge rates, fuel requirements for lower SOx emissions, and the operation of diesel engines and steam turbines. This quiz also covers fluid properties and measurement techniques pertinent to maritime operations.
