Internal Combustion Engines Flashcards
A diesel engine requires five supporting systems in order to operate
Air intake, exhaust, cooling, lubrication, and fuel injection
The back and forth motion of one or more pistons is transformed into the rotary motion of the crankshaft
Reciprocating engines
Diesel engines are not self speed limiting because the air entering the engine is
Always the maximum amount
Engine speed is limited solely by
The amount of fuel injected into the engine cylinders
Diesel engines require a _____ to control the amount of fuel being injected into the engine
Speed limiter (governor)
A diesel engine does not require ____
An ignition system
In a diesel engine, the fuel is injected into the cylinder as ____
The piston comes to the top of its compression stroke
When fuel is injected in a diesel engine, it vaporizes and ignites due to
The heat created by the compression of the air in the cylinder
Terms used to define the displacement of an engine
Bore and stroke
Displacement is measured in
Cubic inches or litres
Diametre of the engine’s cylinders
Bore
The distance the piston travels from the top of the cylinder to the bottom
Stroke
Bore x stroke x number of cylinders equals
Displacement
Highest point of travel by the piston
Top dead center
Lowest point of travel by the piston
Bottom dead center
There are ____ degrees of crankshaft travel between TDC & BDC
180
All events that occur in the engine are related to
The location of the piston
For a diesel engine, power is rated in
Units of horsepower
The power transmitted to the pistons by the gas in the cylinders and is mathematically calculated
Indicated horsepower
Amount of useable power delivered by the engine to the crankshaft
Brake horsepower
Indicated horsepower can be as much as ___ higher than brake horsepower
15%
The difference between indicated and brake horsepower is due to
Internal engine friction, combustion inefficiencies, and parasitic losses
Ratio of an engine’s brake HP and its indicated HP
Mechanical efficiency
Mechanical efficiency of a four cycle diesel
About 82 - 90 percent
Measure of an engine’s ability to apply the power it is generating
Torque
Torque is commonly given in units of
Foot pounds
1 HP = _____ ft-lbs/min or ____ ft-lbs/sec
33000
550
Amount of compression
Compression ratio
Amount of space within the cylinder when the cylinder is at BDC as compared to the amount of space within the cylinder when the piston is at TDC
Compression ratio
Gasoline engine compression ratios range from
8:1 to 12:1
Diesel engine compression ratio ranges from
14:1 to 25:1
The high compression ratio of a diesel engine heats the air in the cylinder to approximately
1000•F
Ignites the fuel when injected into the cylinder (diesel)
Heat of compression
To find the compression ratio
Divide the total volume of the cylinder with the piston at BDC by the volume of the cylinder at TDC
Machine that converts thermal energy into mechanical energy
Engine
The correct relationship between the crankshaft and camshaft
Timing
Must be maintained so that the fuel injector operation and the opening and closing of inlet and exhaust valves occur in the correct sequence
Timing
In a four stroke engine, the camshaft is geared so that it rotates at ____ the speed of the crankshaft
Half (1:2)
Air is drawn into the cylinder due to
The negative pressure created by the increase in cylinder volume
At BDC the air in the cylinder is at
Atmospheric pressure (14.7 psia)
When the piston has traveled to the top of its stroke, the temperature has increased to approximately ___ and approximately ____ (pressure)
1300•F
750 psia
In a four stroke engine, scavenging takes place when
The piston is nearing TDC during the latter part of an upstroke and the early part of the downstroke
Have a better mechanical efficiency
Two stroke engine
Less fuel efficient engine
Two stroke engine
In a two stroke engine, the camshaft is geared so that it rotates ____ the crankshaft
At the same speed as (1:1)
Installed in all two stroke diesel and some four stroke diesel engines, increase the flow of air into the cylinders
Blower
Compresses the air and forces it into an air box or intake manifold
Blower
Creates constant air pressure that is available during the cycles of operation
Blower
In a two stroke engine, scavenging takes place during
The latter part of the downstroke and the early part of the upstroke
After the piston travels approximately ___ of the way to BDC, the piston starts to uncover the inlet or scavenging ports
3/4
Lets the blown, compressed fresh air enter the cylinder which helps cool the cylinder and scavenge the cylinder of the remaining exhaust gases
Overlap
Air forced into the cylinder
Scavenge air
Ports through which air is forced into the cylinder
Scavenge ports
In a four stroke diesel engine, what term is used to describe the timeframe during which both the intake and exhaust valves are open
Valve overlap
Secure an engine in place to the hull structure or a sub base, but are not actually part of the engine
Engine mounts
Two types of engine mounts
Rigid and flexible
Prevent any movement of the engine in relation to the cutter or boat
Rigid mounts
Two primary types of rigid mounts
Rigid and epoxy
Used for absorbing minor engine vibrations
Flexible engine mounts
Mounting pedestal for the engine and its driven machinery, where alignment is critical
Sub-base
Secure the engine, driven machinery, and sub-base to the hull structure
Foundation bolts
Foundation bolts must be inspected for what periodically
Tightness
Method of inspecting foundation bolts
Sounding
If the sounding is clear (like a bell)
The bolt is tight
If the sounding is dull (like a thud)
The bolt needs tightening
Wear what when sounding foundation bolts
Safety goggles
Provides the structure and rigid frame for the engine’s cylinders, coolant, and oil passages, and provides support for the crankshaft and camshaft bearings
Block
The area around the crankshaft and crankshaft bearings
Crankcase
Usually located on the bottom of the cylinder block
Crankcase
Located at the bottom of the crankcase
Oil pan
This area encloses the rotating crankshaft and crankshaft counterweights and directs returning oil into the oil pan
Crankcase
Collects and stores the engine’s supply of lubricating oil
Oil pan
Provides the top seal for the cylinder bore or sleeves
Cylinder head
Provides the structure holding exhaust valves (and intake valves where applicable), the fuel injector, and necessary linkages
Cylinder head
Construction of the cylinder head
Designed to withstand rapid changes in temperature and pressure, and is normally made of a heat resistant cast iron or alloy
Seals the surface between the cylinder block and cylinder head
Cylinder head gasket
Cylinder head studs are manufactured from
Round rod, generally of alloy steel
Two types of cylinders
Integral liner
Removable liner
Each cylinder is bored or machined into the block casting, making the block and cylinders an integral part
Integral liner
A machined steel sleeve/liner is pressed into the block casting to form the cylinder
Removable liner
Provides the engine with the cylindrical structure needed to confine the combustion gases and to act as a guide for the engine’s pistons
Cylinder liner, bore, or barrel
Construction of cylinder liners
Commonly close-grain cast iron, and may be treated with chromium to aid in oil retention
Three types of cylinder liners
Dry liner
Wet liner
Water-jacketed
Engine coolant circulates in passages in the engine block; the liner does not come into contact with the coolant
Dry liner
Engine coolant comes into contact with the liner
Wet liner
The cooling jacket is an integral part of the liner assembly. The flow through this liner is normally bottom to top
Water jacketed
To ensure a good seal will be made between the piston rings and liner, this check must be performed prior to piston intallation
Out of roundness check
Use ___ to check liners with integral cooling passages
Hydrostatic testing method
Use ___ equipment to locate cracks in dry liners
Magnaflux
To locate cracks in a liner with integral cooling passages, technicians will commonly fill the passage with
Glycol type antifreeze
Components that move up and down or back and forth in a repetitive motion
Reciprocating components
Transforms the thermal energy of the expanding gases into mechanical energy
Piston
Rides in the cylinder liner or sleeve
Piston
Pistons are commonly made of
Aluminium or cast iron alloys
____ pistons are used in high speed engines because they are lightweight and provide better heat transfer
Aluminium
____ pistons are used in low speed engines because they offer a longer service life and less wear
Cast iron
Prevent the combustion gases from escaping and keep friction to a minimum
Piston rings
How much of a pistons heat is transferred via ring contact with the piston wall
About 30%
The upper part of a piston directly responsible for changing the volume of the cylinder
Crown
Reinforcement used on larger pistons to prevent flexing or warping
Piston crown rib
Can serve as the crown rib on smaller pistons
Piston pin boss
The side of the piston
Piston skirt
Receives the side thrust created by the movement of the connecting rod and crankshaft, and works to keep the piston in proper alignment
Piston skirt
Three skirt designs
Plain
Slotted
Knurled
Rib around the inside of the skirt used on large pistons or long skirted pistons to prevent flexing or warping
Skirt reinforcement
Rings are usually made of
Cast iron and coated with chrome or molybdenum
Most pistons have how many rings
Two to five
___ acts primarily as the pressure seal and is known as a compression ring
Top ring
____ acts as a wiper ring to remove and control the amount of oil film on the cylinder walls
Intermediate ring
___ is an oiler ring and ensures that a supply of lubricating oil is evenly deposited on the cylinder walls. Also known as an oil control ring
Bottom ring
Seals the combustion chamber, preventing blow by and loss of power
Compression ring
Transfers heat from the piston to the cylinder wall
Compression ring
On the upstroke, prevents metal to metal contact by distributing oil to the cylinder wall
Oil control ring
On the down stroke, wipes excess oil from the cylinder wall, preventing oil from burning in the cylinder
Oil control ring
Spring steel ring placed behind the oil control ring to increase the pressure of the ring face against the cylinder wall
Flexible ring with expander
Ring gap of the expander is placed ____ from the gap of the oil control ring
180 degrees away
The part of the ring that comes in contact with the cylinder wall
Face
The distance from the face to the inside edge of the ring
Wall thickness
The ends of the rings, which allow the ring to be expanded over the piston and compressed to fit into the cylinder bore
Ring joint
The distance between the ends of the ring
Ring gap
Hold the rings in place
Piston grooves
Done to ensure proper fit of rings in the piston
Measuring piston groove width and depth
The space between the rings and the lands that allows the ring to expand
Side clearance
Side clearance is measured with
A feeler gauge
The link between the piston and the connecting rod
Piston pin (wrist pin)
Piston pin is usually constructed of
Hollow, machined, hardened, precision ground, alloy steel and provides maximum strength with a minimum of weight
The piston pin is attached one of three ways
Fixed or stationary
Semi-floating
Full-floating
The pin is secured to the piston pin bosses by a bolt or pin, and the connecting rod rotates on the wrist pin
Fixed or stationary
The pin is secured to the connecting rod by a bolt or pin, and the wrist pin rotates in the piston pin bosses
Semi-floating
The pin is free to rotate in the piston pin boss and the connecting rod
Full-floating
Heavily reinforced opening in the skirt
Piston pin boss
The mounting point for bushings or bearings which support the piston pin
Piston pin boss
Rib over the piston pin boss to prevent flexing or warping of the boss
Piston pin boss reinforcement
Clean the piston components with ___ and dry them with ____
Fuel oil
Compressed air
Connects the piston to the crankshaft
Connecting rod
The rods are made from
Drop-forged, heat-treated steel
Two types of connecting rod construction
Conventional construction
Fork and blade construction
Changes the reciprocating movement of the pistons and the connecting rods into a rotary motion
Crankshaft
Normally crankshafts are machined from
Forged alloy or high carbon steel, sometimes a cast iron alloy
Serve as the points of support and as the center of rotation for the shaft
Main journals
Hollow construction of the journals ___
Reduces weight considerably, increases torque capability of the crankshaft, provides a passage for the flow of oil
The rear main journals in some applications are ___ than the front end journals due to ____
Larger
The weight of the flywheel and the extra support it needs
The points of attachment for the connecting rods and are offset from the main journals
Connecting rod journals
Form the link between the main or intermediate journals and the connecting rod journals
Webs
The arrangement of two webs together with the connecting rod journal
Throw
Balance the off-center weight of the individual crank throws and thereby compensate for centrifugal force generated by each rotating crank throw
Counterweights
Counterweights will always be found in
Pairs
Use inertia to reduce the pulsating effect of power impulses
Counterweights
In all engines, the bending of the crankshaft takes place primarily in ___
The webs
Crank web deflection should be taken ___
After major overhaul
Dry dock
Haul out of the cutter
Crank web deflection readings should only be taken with the cutter ___
In the water
For engines with crank journals of ____, crankshaft deflection readings are to be recorded in ____
Four inches or more
Machinery history and reported in the cutter engineering report
Micrometre for measuring the differences in distance between the webs of a crankshaft during a revolution of the shaft
Strain gauge
The strain gauge should be installed with its two endpoints in ___
The crankshaft prick-punch marks
Strain gauge readings are generally taken at five crank positions
TDC, inboard, near or at BDC, outboard, TDC again
If the strain gauge reading is not within _____, a complete set of readings will need to be retaken
.0025 of 0
When the driving mechanism of an engine consists only of gears, the mechanism is commonly called
Gear train
Gear teeth placed at an angle
Helical teeth
Placed between two other gears to transfer motion from one gear to the other without changing their direction
Idler gear
The space between the thickness of a gear tooth and the width of the space between teeth in the matting gear
Backlash
Backlash is normally measured using
A feeler gauge
The camshaft is driven by a series of gears called
Idler gears
Timing gears
Serve to support rotating shafts and other moving parts, also used to transmit loads from one part of the engine to another
Bearings
Two basic types of engine bearings
Anti-friction bearings
Friction bearings
The use of anti-friction bearings is limited mainly to ___
The exterior areas of the engine
Anti-friction bearings can be grouped into six general classifications
Ball bearings Cylindrical roller bearings Needle bearings Tapered roller bearings Self-aligning roller bearings Thrust bearings
All anti-friction bearings employ a
Rolling element
Roller bearings are often made of
Carbonised steel alloy
Type of friction bearing used in most CG engines
Precision type
Stores up energy during the power event and releases it during the remaining events of the operating cycle
Flywheel
Flywheels are made of
Cast iron, cast steel, or rolled steel
Device used to absorb torsional vibrations of the crankshaft
Vibration damper
The vibration damper is mounted on ___
The crankshaft at the front of the engine
Uses a freely rotating disk acting against a fixed disk which creates friction and thereby acts as a brake
Vibrating damper
Consists of a hollow housing that contains a free or floating flywheel. The small clearance between the flywheel and the housing is filled with a ___
Viscous silicone fluid
Limits the increase or decrease in speed during sudden changes of load
Flywheel
Counterweights use ____ to reduce the pulsating effects of power impulses
Inertia
The group of parts that changes the type of motion and causes the valves of an engine to operate
Valve actuating mechanism
Long bar with egg-shaped eccentric lobes, one lobe for each valve and fuel injector
Camshaft
Slop or give in the valve train before the cam actually starts to open the valve
Valve lash
Eccentric projections that change the rotary motion of the camshaft to the reciprocating motion needed to operate the valves, injectors, and other components
Cam lobes
The amount a valve opens or moves away from its seat
Lift
The amount of time that a valve remains open
Duration
The sides of the cam
Flanks
The highest point on the cam
Nose
Transmit the rotating motion of the the cam to the the rocker arm. They ride the flank of the cam and are raised by the nose as the camshaft rotates
Cam followers
Three types of cam followers
Flat
Roller
Pivoted
Type of cam follower, provides for quick opening and closing of the valves
Flat
Type of cam follower, Provides for reduced friction between moving parts
Roller
Type of cam follower, Similar to the roller follower. The main advantage is that the pivot arm (instead of the sliding follower) takes up the side thrust created by the cam
Pivoted
Part of the actuating assembly responsible for transmitting the motion of the cam follower to the rocker arm
Pushrod
Constructing of pushrod
Usually hollow
Cup in the tip
Round at the other end
Hardened wear surfaces
Transmits the motion of the cam follower to the valve
Rocker arm
One end is in contact with the valve stem and the other end is actuated by the camshaft
Rocker arm
Mechanically opened and closed to admit or exhaust the gases as needed
Valves
The point at which the valve seals against the head
Valve seat
Part of the actuating assembly that admits intake air and discharges the exhaust gases from the combustion space
Poppet valve
The heads of poppet valves have
Beveled edges
Exhaust valves are usually made of
Silicon chromium steel
Acts as a surface against which a valve comes to rest to provide a seal against leaking
Valve seat insert
Replaceable ring that fits into a counter-bored recess in the valve port of the cylinder head
Valve seat insert
Three methods to install a valve seat insert
Pressing insert into place
Cold shrink method
Heat sink method
Reduces the diameter of the insert by the use of dry ice
Cold shrinking
Involves heating the head and installing the insert and then allowing the head to cool
Heat sinking
Prevent undesirable side to side movement of the valve in the cylinder head
Valve guides
Valve guides are usually made of
Materials that are softer than the valve stem
Returns a valve to the closed position
Valve spring
Valve springs are made of
Round steel wire wound in a helical coil
The two supports that the valve springs are mounted between
Valve spring retainers
The lower spring retainer may simply be
A recess in the top of the cylinder head
The upper spring retainer is
A steel washer shaped to fit the top of the spring and is attached to the valve stem with a removable keeper
Attach the upper valve spring retainer to the top of the valve stem
Valve spring keeper
Most common valve spring keeper
Split conical collar which fits around the valve stem and into one or more grooves
Used to remove and install valve spring keepers
Spring compression tool
Device that permits the opening of two or more valves with the use of only one rocker arm. Also known as crossheads
Valve bridge
Combination of components used to supply fresh clean air to the cylinder
Air intake system
Removes dust particles from the air that would cause abrasion or harm to the engine
Air cleaner
Three type of air filters
Dry air filter
Viscous air filter
Oil bath filter
Paper, cloth, or a metal screen in used to catch and trap dirt before it enters the engine
Dry air filter
Cotton fabric, wire mesh screening, specially wound copper crimp, or metal wool may be used. Wet usually with a medium weight oil
Viscous air filter
Air is drawn through a bath of oil, so that the oil collects the dirt in the air
Oil bath filter
Most coast guard cutters use what kind of air filter
Viscous air filter with a pleated oiled cotton fabric element
Depend upon microscopic holes to filter
Paper element
Viscous air filters have a ____ flow rate than paper elements
30% better
Uses baffles to abruptly change the direction of the airflow entering the cleaner
Oil bath filter
Incorporated into the intake system to help reduce the ambient engine room noise
Air intake silencers
Centrifugal compressor which is driven by the exhaust gases and, in turn, compresses the intake air to provide an increased mass of air to the combustion chamber
Turbocharger
Turbocharging can produce power gains of ____ compared to those of naturally aspirated engines
Over 50%
The speed of the turbine in the turbocharger is controlled by
the speed and load of the engine
Downstream of the turbocharger to reduce the air temperature and increase the density of the air entering the combustion chamber
Charge air cooler (either an intercooler or aftercooler)
Water cooled heat exchangers are called
Aftercoolers
Air cooled heat exchangers are called
Intercoolers
Also known as a supercharger
Blower
Positive displacement pump that is used to supply the engine with a large volume of low-pressure air
Blower
Unlike a turbocharger, a supercharger is
Belt or gear driven, and provides instant boost pressure to the engine at all speeds
This blower has two rotors with two, three, or four lobes on each. Driven by the engine’s gear train
Roots blower
Common type of blower found on coast guard engines
Roots blower
Combination of devices used to remove waste gases from the combustion chamber with a minimum of resistance
Exhaust system
Used on multi-cylinder engines to receive, collect, and direct exhaust gases away from the engine
Exhaust manifold
collects exhaust gases from individual cylinders and directs them to an exhaust tube leading to a turbocharger or muffler
Cast iron air-cooled manifold
Has water passages that are an integral part of the manifold
Jacketed manifold
Flexible pipe between the exhaust manifold and the muffler
Exhaust pipe
Quiets the exhaust noise
Muffler
Two types of mufflers
Wet
Dry
Uses water to cool the exhaust gases, quench sparks, and aid in silencing
Wet muffler
Uses baffles and abrupt changes in direction of flow to remove sparks and solids from the exhaust gases, and aid in silencing
Dry muffler
The temperature of combustion is about ____ that at which iron melts
Twice
When fuel burns in the cylinders of an engine, only about _____ of the heat energy from the fuel changes into mechanical energy and then leaves the engine in the form of brake horsepower
One-third
Removes heat from the engine to maintain a designated operating temperature
Cooling system
Heat is transferred from the engine using what kind of heat transfer
Convection
Mixture of fresh water and coolant that circulates in the water jackets of the engine block
Jacket water
Drawn from the water surrounding the boat or ship into the cooling system by a pump
Raw water
Used for cooling jacket water, lubricating oil, and sometimes for the air passing over generator windings
Raw water
The engine is cooled directly by sea water
Open cooling system
Fresh water is circulated through the engine. The fresh water jacket is then cooled as it passes through a cooling device (heat exchanger), where heat is carried away by a constant flow of sea water or air
Closed cooling system
Most commonly used cooling system on marine internal combustion engines
Closed cooling system
Means that the liquid that is used to carry away heat from the engine is drawn directly from the water in which the ship or boat operates. This liquid is then discharged overboard, there is no freshwater circuit
Open cooling system
Has a freshwater circuit that is self contained and is used continuously for the cooling of the engine
Closed cooling system
When an open cooling system engine operates over ____ it tends to build up a corrosive scale
140*F
Closed cooling systems may be either
Pressurized
Vented
Pressurized closed cooling systems are normally operated at
Pressures greater than atmospheric pressure so that the boiling point of the coolant is raised to a temperature that is higher than 212*F
Vented closed cooling systems are operated at
Atmospheric pressure, and the coolant boils at 212*F
Pressure release valve set to release at a predetermined pressure and increasing the boiling point of your coolant
Pressure cap
What does the number on the coolant pressure control cap indicate
The pressure at which the valve opens
Determines the maximum pressure in the cooling system
The setting of the spring on the cap
Device used to cool a liquid by transferring heat from one medium to another
Heat exchanger
Heat exchangers are classified by
Direction of flow of the two mediums
Fluid passes
Path of heat
Four type of heat exchangers found in the Coast Guard
Ross shell and tube type
Harrison strut type
Harrison plate type
Plate type
Heat exchanger, consists primarily of a bundle of tubes encased in a shell
Ross shell and tube type
Ross shell and tube type heat exchanger is classified as
Counter-flow, single-pass, indirect type
Heat exchanger, uses tubes that are composed of two sections or strips pressed together to form a hollow, flat tube
Harrison strut type
The Harrison strut type heat exchanger is classified as
Cross-flow, single-pass, indirect type
Heat exchanger, consists of a stack of flat, oblong plate-type tubes, connected in parallel with the oil supply. Encased in a cast metal housing
Harrison plate type
The Harrison plate type heat exchanger is classified as
Cross-flow, single-pass, indirect type
Heat exchanger, consist of a pack of corrugated metal plates with portholes for the passage of the two fluids. Heat transfer takes place between the plates as the fluids pass through
Plate
Heat exchanger, assembled between a fixed frame plate and movable pressure plate and is compressed by tightening the bolts
Plate
The plate corrugations on the heat exchanger promote
Fluid turbulence and support the plates against differential pressure
The point of entry for raw water through the hull
Sea chest
Removes coarse contaminates from the water before it reaches the pump or cooler
Sea strainer
Two major types of sea strainers in the Coast Guard
Simplex
Duplex
Uses a single element to strain the sea water. You must secure the system and isolate the strainer before you can remove the element for cleaning
Simplex
Has two elements with a valve to direct the flow of sea water to one element or the other. By using this valve, you can clean the strainer without having to disrupt system operation
Duplex
Also called a surge tank or supply tank, is used to provide a place to add makeup water, allow for changing volume of water when heated or cooled, maintain a static head on the system
Expansion tank
Used to keep the engine block warm by heating a circulating the jacket water
Jacket water heater
Used to carry and direct the flow of fluids
Piping
Piping is made of two types of materials
Hard (rigid)
Flexible
This piping normally made of copper, nickel, or an alloy of both copper and nickel
Hard
This piping is used to isolate vibration and torque between the engine and the fixed piping of the ship. Normally made of rubber
Flexible
The first valve just inside the hull of the ship
Skin valve
Mounted outside the ship’s hull and uses the seawater to cool the engine’s jacket water
Keel cooler
Can be used as an alternative to pumping corrosive raw water through the equipment for cooling
Keel cooler
Cooling water pump is of what type
Non positive displacement
Discharge rate and pressure of the jacket water pump is regulated by
Thermostatic expansion valve
Used to maintain the engine at its designed operating temperature by regulating pump discharge from the cooler to the engine, and jacket water flow through the cooler
Thermostatic valve (thermostat)
Thermostatic valves elements may be filled with
Gas, liquid, wax, or bi-metal
Thermostatic valves elements are made of
Copper, brass, or monel metal
Sacrificial anode used to control or reduce the effects of electrolysis
Zinc
Work by giving off ions and corroding more readily than other metals in the system
Zinc
The positive terminal of a galvanic cell that is consumed in preventing electrolytic corrosion of the metal protected
Sacrificial anode
The chemical change produced by passing an electric current through an electrolyte
Electrolysis
A nonmetallic electric conductor (as a solution, liquid, or paste) that carries current by movement of ions instead of electrons (salt water)
Electrolyte
A pair of dissimilar metals, acting together as an electric source when brought in contact with an electrolyte
Galvanic cell (copper and aluminium)
A gradual wearing away by chemical or electrochemical process
Corrode
The metal the current is flowing ___ suffers corrosion, but when zincs are used, the metal the current is flowing ____ is protected from corrosion
From
To
Never use what kind of anodes on aluminium surfaces
Magnesium
Replace zincs when
They are half deteriorated or if they show no deterioration after having been in service
Zincs that do not corrode are
improper material or have been improperly installed
Non-functioning zincs will
Retain the shape of a new anode and may be covered with a hard, adherent, dark gray or black film
Most common zinc found in a cooling system
Pencil zinc
Most important factor in the operating life of a diesel engine
Lubrication
Substance capable of reducing friction, heat, and wear when introduced as a film between moving parts
Lubricant
Three types of lubricant
Dry (graphite)
Wet
Mineral-based
Five requirements of a lubricant
Cool Clean Seal Reduce friction Prevent corrosion
Six functions of the lubricating oil system
Storing Cleaning Cooling Movement of oil Regulating system pressure Protecting the system
If the oil is too cold
It will not flow freely
If the oil is too hot
It cannot support the bearing loads or carry away enough heat, and it may flow too heavily
Storage space for the engine’s lube oil
Sump
Sumps are classified as either
Wet or dry
Most common type of sump, is located directly below the engine and bolted to the engine’s crankcase
Wet sump
This type of sump is not attached to (and is separate from) the engine, and has separate recirculating pumps to transfer the oil from the sump to the engine
Dry sump
May be either fine or coarse mesh wire screen attached to the oil pump suction line
Suction screen
Delivers oil under pressure to the components of the engine requiring lubrication
Oil pump
Normally a positive displacement, rotary gear type pump, driven by a gear or chain from the crankshaft or camshaft, or accessory drive gears
Oil pump
Protects the oil pump and lube oil system from excessive pressure
Relief valve
Used to maintain an even oil pressure as the engine changes speed and the oil temperature changes
Regulating valve
Used on some oil systems to determine when the filter elements have exceeded their usefulness and must be renewed
Pressure differential gauges
Passages that are drilled or formed in the engine. Their purpose is to distribute oil under pressure to the components of the engine that require lubrication
Main oil galleries
Main oil galleries may be classified as either
Integrally drilled passages
Externally mounted
Provided in the lubricating oil system to allow the taking of oil samples from the system
Petcock valves
Small plug, quarter turn ball or globe type, capped valves, which can easily be manipulated with your fingers controlling the amount of oil sampled
Petcock valves
Commonly referred to as prelube pumps
Priming pumps
Aid in getting lubrication forced into the engine’s various oil passages and galleries prior to starting larger engines
Priming pump
Are of the positive displacement type and are either electric motor-driven or hand operated
Priming pump
Two types of alarms in the coast guard
Visual and audible
Two major components that assist the filtering of the oil are
Strainer
Filter
Remove coarse particles of contamination from the lube oil
Strainer
Two types of strainers for oil are
Wire mesh
Edge disk type
Two most common oil cleaning devices
Edge wound type
Edge disk type
Cleans by rotating the cleaning blade around the exterior of the element
Edge wound type oil cleaning device
Cleans by rotating the disks while the fixed cleaner blades scrape off any contamination, also known as a knife edge strainer
Edge disk type
Oil cleaning devices should be rotated how much while the engine is in operation
One complete revolution each hour
Oil strainer housings should be drained how often
Daily
Rotate oil cleaning devices in ____ rotation only
Clockwise
Designed to remove harmful materials such as dirt, dust, and other insoluble matter (anything that will not mix readily with oil)
Oil filter
Two types of oil filters
Spin-on type
Canister type
Filters will not remove particles smaller than ___
.0002 in.
Filter elements in the Coast Guard are of what type
Replaceable element
The flow of fluid through the oil filter element is from ____ to ____
Outside
Inside
Oil filter elements are made of these elements
Cellulose
Cotton yarn
Cotton waste
Pleated paper
Most common material used in oil filters
Pleated paper
Permits the entire pump output to be filtered prior to lubricating the engine. It incorporates a built-in bypass valve that allows oil to be bypassed to the engine in the event the filters become clogged
Full flow system
The fuel system serves two purposes
Supply the fuel to run the engine
Act as a coolant to the injectors
Hold the fuel, keep it free from water, dirt, or other contaminates
Fuel tank
Accurate measuring of fuel that is delivered to each cylinder of the engine for each power stroke
Metering
Speed at which fuel is injected into the combustion chamber
Rate of injection
The delay between the time fuel is injected, and the time it reaches the ignition point
Ignition delay
If the rate of fuel injection is too high
Then it may cause detonation
Simultaneous combustion of all droplets of the fuel spray, thereby causing low exhaust temperature and loss of power
Detonation
If the rate of fuel injection is too low
Then the engine will have a loss of power and will experience high exhaust temperatures and smokey exhaust
If the fuel is injected early in the injection cycle
Then the symptoms will be similar to those caused by a rate of injection that is too high
If the fuel is injected late in the injection cycle
Then the symptoms will be similar to those caused by a rate of injection that is too low
Fuel must be injected into each cylinder in the form of ___
A fine spray
Breaking up of fuel into minute particles
Atomization
Ensures that each particle of fuel is surrounded by oxygen
Atomization
The high injection pressure of the fuel ensures
Atomization, penetration, distribution
Equal placement of the fuel particles in the combustion space
Distribution
Is to inject a precise amount of atomized and pressurized fuel into each engine cylinder at the precise time
The primary job of the diesel fuel system
Most fuel supply tanks are constructed of ____, or ____ small cutters and standard boats
Steel
Aluminium
Provided to allow for expansion and contraction of the fuel due to temperature changes
Vents
Fuel tanks should be kept topped to ____ of full capacity in order to maintain stability and prevent corrosion and condensation
95%
Should be installed on the fill piping when the fuel tanks are not being filled
Fueling connection caps
Remove fine particles of contamination from the fuel
Fuel filters
Separate the larger particulates from the fuel source or tank
Primary fuel filter
Used to filter out fine particles in the fuel system
Secondary fuel filter
Fuel filters are required to be protected from
Heat sources
Used to ensure fuel is not spilled during maintenance and servicing
Isolation valves
Transfer fuel from the fuel tank to the high-pressure fuel pumps
Fuel transfer pump or fuel delivery pump
The fuel pump is usually of what type
Positive displacement type, and is equipped with a relief valve
Time and meter the correct amount of fuel injected into the cylinders
Injection or high-pressure pumps
Raises the fuel pressure to a pressure higher than combustion pressure
High-pressure pump
Spray the fuel in atomized form into the combustion chamber of each cylinder
Injector nozzle
The component of the fuel system that meters and injects the fuel into each cylinder in an internal combustion diesel engine at the proper time
Fuel injector
The fuel injection equipment used on internal combustion diesel engines is of what type
Mechanical
Three types of fuel injection systems
Unit injector
Electronic unit injector
Common rail type electronic control
This kind of injector was designed with simplicity in mind for both control and adjustment
Unit injectors
Used on direct injection, open-type, two-cycle combustion chamber engines. No high pressure fuel lines or air fuel mixing or vaporisation devices are required with these injectors
Unit injectors
Lightweight, compact unit that injects diesel fuel directly into the combustion chamber
Electronic unit injector
EUI
Electronic unit injector
Controls the EUI
Electronic control module
Determines the amount of fuel injected and the beginning if injection timing
ECM
An injector is mounted on each cylinder of the engine, and high-pressure fuel produced by the supply pump is distributed to each injector by the common rail
Common rail type electronic control
Measures the specific degree of tightness of a nut or bolt as it is affixed onto a piece of equipment
Torque wrench
Torque wrenches are used to perform only
The final tightening of nuts or bolts
Works by the beam bending in response to the torque applied
Deflecting beam torque wrench
Called a click-type torque wrench
Micrometre torque wrench
Works by preloading a snap mechanism with a spring to release at a specified torque of the fastener
Micrometre torque wrench
This type of torque wrench is designed for quick calibration
Dial torque wrench
Highly accurate and precise measuring devices primarily used to measure internal and external parts of an engine
Micrometres
Three most common types of micrometres
Outside micrometre
Inside micrometre
Depth micrometre
Used to make very precise measurements of the outside of an engine part
Outside mircometre
For those medium and large parts with inside diametres greater than four inches
Inside micrometre
The inside micrometre can be extended to
Greater than 30”
Used to find the distance between two parallel surfaces
Depth micrometre
Simple product to measure the clearance between the bearing journal and the bearing
Plastigage
Piece of plastic that deforms in a very consistent way, making it easy to determine the size of gap by measuring the deformation in the piece of plastic
Plastigage
Used to measure the inside and outside diametres of pipes, cylinders, etc.
Calipers
Three types of calipers
Simple
Slide
Vernier
Three kinds of simple calipers
Outside
Inside
Hermaphrodite
Simple calipers are always used in conjunction with
Ruler
Direct reading device and are used to measure inside and outside diametres, as well as other dimensions
Slide calipers
Consist of an L-shaped frame with a scale engraved on the long shank
Vernier slide calipers
A plunger moves in and out from the body of the indicator and rotates the measuring needle on a dial face
Dial indicator
Precision measuring instrument that can be positioned at the end of an arm that can be positioned inside a hole or an opening
Telescoping gauge
Used for quick accurate measurements of inside diametres of holes and widths of slots
Telescoping gauge
The telescoping gauge measures diametres from
5/16” to 6”
Measure the telescoping gauge with
An outside micrometre
Concise measuring tool used to check thickness, gap, alignment, and spacing of machinery
Thickness gauge (feeler gauge)
Used to remove carbon ridges formed at the tips of the cylinders produced by piston rings moving up and down in the cylinders
Ridge reamer
Used to remove a piston ring
Piston ring expander
Designed for compressing the piston rings when a piston is reinstalled
Ratchet type piston ring compressor
Used for installing specific size pistons within cylinder bores, made of carbon steel
Taper-type piston ring compressor
One of the most accurate tools for measuring a cylindrical bore or for checking a bore for out of roundness or taper
Cylinder bore gauge
Used to obtain the measurements for out of roundness
Micrometre and telescoping gauge
Used to pull gears, bearing, pinions, sheaves, pulleys, and wheels
Gear and bearing puller
Screw type puller with two or three jaws, the grip tightens as pull in increased
Gear and bearing puller
Sometimes called retaining rings
Snap rings
Fasteners used to axially position a component on a shaft or in a bore
Snap rings
Used for removing or installing snap rings
Snap ring pliers
Common shop press that is used to remove and install bearings, seals, and shafts of engine components
H-type hydraulic press
The H-type hydraulic press is capable of delivering a ___ capacity
20-ton
Most common tool used to measure by hand, varies from 6 to 36 inches, usually made of steel
Machinist rule
What does the number by the one inch mark on a rule indicate
The number of divisions per inch
Measures the depth of holes, slots, counterbores, and recesses
Rule depth gauge
The depth micrometre has a range of
0 to 9 inches
A Vernier depth gauge will not enter a hole that is less than
1/4”
Used for checking depths of holes, recesses, slots, scratches, and paint thicknesses. Measurements can only be made on a longitudinal axis
Dial depth gauge
Used to measure cylinder compression which assists you in diagnosing engine conditions
Compression tester
Compression test: If the needle fails to upscale or remains the same for several strokes and then starts to climb
The cylinder has a sticking valve
Compression test: If the compression reading is considerably higher than the vehicle manufacturer’s specifications
It indicates carbon buildup in the cylinder
Compression test: If a reading on two adjacent cylinders is 20 lbs or more lower than the other cylinders
Indicates a defective head gasket
Compression test: If readings are low or vary widely between cylinders
Pour a tsp of SAE 30 oil into each cylinder, and retest. If readings increase considerably, poorly seated or worn piston rings. If readings remain the same, worn out valves and associated components
Compression test reading should not vary more than ___ from cylinder to cylinder
8%
Quick, easy method for repairing damaged threads or for creating stronger original threads in alloys and composite materials in the original equipment
Helicoil inserts
Also known as lockwire pliers
Safety wire pliers
Work just like adjustable pliers except you can lock the opening in place
Safety wire pliers
Operates on the Brayton cycle
Turbine
The same events which occur in a reciprocating engine take place simultaneously and continuously as the engine operates
The Brayton cycle
Operates on the theory that the potential energy of a pressurized gas can be converted to kinetic or mechanical energy
Gas turbine
Compression decreases ____ and increases ___
Specific volume
Total pressure
In the combustor, _____ and _____ increase, while ____ decreases slightly
Temperature
Specific volume
Total pressure
In a turbine, the expanding exhaust gases travel through a decreased ____, creating a ____
Exhaust path
Nozzle effect
During expansion in a turbine, ___ increases, while ____ decreases
Specific volume
Total pressure
Converts the thermal and kinetic energy of the exhaust to mechanical energy and transmits the mechanical energy to a propulsion reduction gear
Power/free turbine
In this configuration (with the addition of a power/free turbine), the gas turbine is referred to as a _____
Gas generator
Marine propulsion gas turbines typically add ____ in the exhaust stream of the gas turbine
Power/free turbine
In a turbine, the typical compressor is ____ compressor, made up of a series of ___ and ____
Axial flow
Stators
Rotors
In a turbine compressor, each set of stators and rotors is referred to as ____
A pressure stage
In a turbine compressor, air flow is ___ to the axis of the shaft
Parallel
As air passes through each stage of the compressor, its pressure increases and is velocity decreases until it is discharged into the combustion chamber. The more stages, the more the air can be compressed
Bernoulli’s theorem
Stationary sets of vanes that redirect air flow through stages
Stator
Moving sets of vanes that compress and move the air through the turbine to the combustion section of the turbine
Rotor
In a turbine, the combustion chamber/liner can be one of two types
Annular (GE LM2500)
Can-annular (Pratt and Whitney FT-4A)
The ___ combustion chamber/liner is typically found after an axial flow compressor
Annular
This type of combustion chamber/liner consists of an undivided circular shroud extending all the way around the turbine shaft housing. A combustor case then covers this chamber/liner
Annular
This type of combustion chamber/liner is constructed with an annular combustion casing, with the actual combustion taking place in cans arranged around the chamber
Can-annular
Houses the starter, a control mechanism, and power takeoffs for the fuel and lube oil pumps. It is connected by a gear train to the engine rotor via the tower driveshaft assembly
Accessory drive
Supports and houses the gas turbine assembly
Base enclosure assembly
The inner wall of the base enclosure assembly is constructed of ____ that is fire resistant and is designed to withstand a flame of ___ for ___
Perforated metal
2000*F
15 minutes
Used to allow the engine to run at its most efficient speed and reduce the speed of the shaft to a speed that is most efficient for the propellers
Reduction gears
This gear is attached to the propeller shaft
Main gear (bull gear)
The bull gear is ___ than the pinion gear
Larger
Term that describes the change in speed of the shafts attached to the pinion and bull gears
Gear ratio
The gear ratio is determined by dividing the number of teeth on the ___ gear, by the number of teeth on the ___ gear
Driven gear
Driving gear
The slower gear will produce greater ___ than the faster gear, proportionate to the ____
Torque
Speed difference
A Coast Guard cutter harnesses the energy provided by the main engines and gas turbines in two configurations
CODAG (Combined diesel and gas turbine)
CODOG (Combined diesel or gas turbine)
CODAG
Combined diesel and gas turbine
CODOG
Combined diesel or gas turbine
A clutch is a form of ___
Coupling
Designed to smoothly engage or disengage the spinning engine to the non-spinning reduction gear by controlling the slippage between them
Clutch
Friction clutches that use flyweights (shoes) mounted on a drive shaft and turn within a drum. At a specified (spring loaded) centrifugal force, the flyweights are slung out to the drum
Centrifugal clutches
Most major cutters have ___ type clutch for the purpose of saving weight and space
Air-flex
Incorporated in smaller reduction gear applications because they are more tolerant to misalignment and casing deformities. Accept radial and/or axial loads and help maintain alignment
Spherical roller bearings
Composed of a rotating collar and stationary pivoted segments or “shoes”. The bearing is oil lubricated and as it turns the oil clings to the collar and is drawn between the collar and shoes, this allows for a very high load capacity
Kingsbury thrust bearing
The Kingsbury thrust bearing works with a load of __
220 tons
Five common types of gears
Bevel Helical Spur Worm Double helical
Most commonly found gears found in reduction gears
Helical and spur gears
Two L/O pumps on the small standard reduction gear
High Delivery Oil Pump (HDOP)
Auxiliary Trailing Oil Pump (ATOP)
Used to ensure a large quantity of oil is supplied to cool and lubricate gears, bearings, and provide oil to the hydraulic system
HDOP
____ pump is dependent on input shaft speed or the engine’s speed for operation. It is driven by a spur gear on the input shaft and usually is the identical ratio to the engine so it directly corresponds to the engine’s speed
HDOP
____ is run off the output shaft and always supplies oil to the oil circuit in the same direction regardless of shaft rotation
ATOP
Hydraulic spool valve that directs pressurised L/O to the desired clutch pack which engages the Reduction gear into F, N, or R.
Control unit
Uses a cable or lever to move the spool valve to F, N, or R and is the most basic control system
Mechanical
Uses a compressed air linear actuator to move a mechanical lever that moves the spool to F, N, or R. If the air supply is interrupted the spool will return to N
Pneumatic mechanical
The spool valve is moved to F, N, or R by means of compressed air ports around the hydraulic spool valve and move it to F, N, or R. If air supply is interrupted the spool will return to N
Pneumatic
The spool valve is moved by means of oil pressure
Electrical mechanical
The most common shafts on cutters include the following three sections
Line/intermediate/pedestal
Stern tube
Tail
The shaft that extends from the reduction gear and penetrates other compartments before it exits the hull
Line shaft or intermediate shaft
The section of the shaft that is waterborne
Tail shaft
The propeller attaches to the ___
Tail shaft
Holes in the hull structure for accommodating the propeller shaft to the outside of the hull
Stern tubes
Provide long bearing life and are capable of withstanding heavy loads in dirty, abrasive environments
Elastomeric journal bearing technologies
Rubber strips in a cutlass bearing
Staves
Supports the tail shaft and is attached to the exterior hull as an appendage
Strut
Never secure the water supply while underway; damage to the tail shaft journal bearings (enclosed stern tube applications) and seal failures will occur in ___
Less than 5 minutes
Ceramic type seal that prevents sea water from entering the hull
Stern tube shaft seal
Used to reduce sea water intrusion around a rotating shaft to a controlled rate of flow
Stuffing boxes
Stuffing boxes typically limit flow to ____ while underway
7 - 10 drops per minute
Located at the forward end of the stern tube and seals the area between the shaft and stern tube, but allows the shaft to rotate. Hold the packing rings into place
Packing gland or stern tube gland
Provide a mount for the packing gland and a means of adjusting the packing gland inward or outward on the packing rings
Gland bolts
The gland bolts are long enough to allow the packing gland to be backed out ___ so an additional packing ring can be added
1 inch
Packing material in the form of rings, placed in the stuffing box to form a seal to control the rate of leakage along the shaft
Packing rings
Three common types of shaft packing
Braided flax
Teflon
Semi-metallic
Most commonly used and designed for higher speeds, like pumps and small boats. The softest type of packing, it causes less wear on rotating parts. It is not used in high-temperature application
Braided flax
The most slippery of the common types and has the longest life. Can be used for higher temperatures, and also can be used for valve packing
Teflon
The hardest of the common types and used for slower speeds, such as valves and rudders (packing material)
Semi-metallic
Using a commercial packing cutter, cut both ends of the packing approximately ___
45 degrees
When using four or more packing rings, the ends should be staggered ___ apart to reduce leakage
90 degrees
The stuffing box should be inspected ___
On a routine basis and when packing rings are replaced
Authorizing authority for internal access to the reduction gear
EO
Any tools in the vicinity of an open reduction gear must ___
Be secured to a lanyard
Personnel in the vicinity of an open reduction gear must ___
Be inspected to ensure they are free of metal devices and their pockets are empty
What is the purpose of reduction gear?
Reduce shaft speed compared to engine speed
What type of reduction gear has one main gear and one pinion gear?
Single pinion, single reduction gear
What type of reduction gear has one main gear and two pinion gears?
Dual pinion, single reduction gear
What type of bearing is designed to transmit axial force?
Thrust
