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RN - ETME > Mechanical Theory 1 > Flashcards

Mechanical Theory 1 Flashcards

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1
Q

What is the definition of the three tanks:

Header
Service
Tank

A

Header - used as a reservoir to top up a tank or system
Service - used as a reservoir of clean,water free supply of fuel
Tank - used to collect oil returning from a system

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2
Q

What are the main factors that will dictate the material a pipe is made of

A

Temperature
Fluid used
Pressure

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3
Q

What is an accumulator

A

A device which potential energy is stored
(Compressed gas)
(Spring loaded piston)
(Raised weight)

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4
Q

What is the operating principle used within a pressure gauge

A

Bourdon tube principle

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5
Q

Four uses of diesel engines in the RN

A

Motor / propulsion
Power generation
Compressors
Fire systems

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6
Q

What are the five materials used for piping and what for

A

Copper - fresh domestic water
Copper nickel - lubricating oil
Phosphor bronze - HPSW (salt water)
Brass - castings (valves / taps)
Plastic - sewage and pre-wet

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7
Q

What is the definition of a system

A

The organisation of components into a structure that provides a specific service and safely

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8
Q

What is fitted in within a system to remove coarse particles from a fluid

A

Strainer

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9
Q

What are the 3 main gauge types and what are they used for

A

Gauge glass - visual indication of how much fluid is left
Contents gauge - indicates how much fluid remains
Sounding tune - measure the depth of a tank (uses dip tape and conversion chart

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10
Q

what is the purpose of a flywheel

A
  • promotes smooth running of the engine during non-power strokes
  • uses stored inertia to power the crankshaft
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11
Q

what component connects the piston to the crankshaft

A

connecting rod

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12
Q

describe the induction stage on a 4 stroke cycle

A
  • intake valve is opened
  • piston moves from TDC to BDC which draws in air from the intake.
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13
Q

describe the compression stage on a 4 stroke cycle

A
  • intake closes (both valves are closed)
  • piston moves from BDC to TDC, before reaching the max travel,
  • the injector shoots high pressure fuel into the cylinder.
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14
Q

describe the power stage in a 4 stroke cycle

A
  • both valves closed
  • piston hits max travel which causes the mixture to spark(explode).
  • controlled explosion forces the piston back to the BDC
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15
Q

describe the exhaust stage on a 4 stroke cycle

A

exhaust valve opens allowing for the exhaust fumes to be drawn out of the cylinder

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16
Q

list the safety trips ans safety devices fitted to a diesel engine

A
  • low oil pressure
  • low coolant pressure
  • high oil temperature
  • high coolant temperature
  • engine overspeed
17
Q

what are the three oil properties that are checked on a oil test

A
  • water
  • acidity
  • viscosity
18
Q

what is used to connect the piston to the connecting rod

A

gudgeon pin

19
Q

what are four functions of the cylinder head

A
  • incorporates inlet / exhaust ports
  • forms the upper part of the combustion chamber
  • closes the top of the cylinder
  • houses valves and injectors
20
Q

what are the two types of systems

A

Open Loop system - the working fluid is consumed e.g. fuel system, HPSW
Closed Loop system - the working fluid is re-used e.g. fresh water-cooling system.

21
Q

what are the main factors concidered for choosing the seal type

A
  • the system working pressure
  • the fluid being used
  • the temperature involved
22
Q

what are the four example of seals used on board ships

A
  • Gaskets - (non-asbestos fibre, paper, leather, cork, copper, rubber)
  • Mechanical seals – tend to be spring loaded seals with physically push the barrier closed (used on a rotating shaft)
  • Keelering coupling
  • Glandpacking
23
Q

what is the main function of a valve

A
  • Valves and cocks provide a way of controlling the flow of liquid or gas within a system.
  • Valves further allow you to isolate systems. (direction of flow)
24
Q

name the 8 types of valves used

A
  • Globe valve – name from the shape, screw down valve, once shut the spindle is lowered.
  • Gate valve – used in large bore systems
  • Flap valve – non-return valve (like a diode)
  • Saunders valve – fitted with a rubber diaphragm (used in water and fuel systems)
  • Ball seated cock – bored through ball, turns 90degrees to open/close
  • Relief valve – valve is consistently shut via a spring, however if the pressure has a stronger force then the spring, the valve will release the pressure (protects systems from over pressurisation)
  • Reducing valve – valve reduces the pressure build up
  • Non-return valve – prevents flow reversal using either piston or flap method (like a diode)
25
Q

what are the two types of pumps

A

Positive
* physically displaces and moves the fluid along
* These pumps deliver high pressures and have the ability to self-prime as they physically pull the fluid from the tank

dynamic displacement
* moves a fluid by using the enrgy from the impeller withing the pump to accelerate the fluid
* These pumps are required to be primed before being used fully

26
Q

what is bernoulli’s principle

A

the speed of a moving fluid increases as the pressure within the fluid decreases

27
Q

what are the six pressure gauses and system indicates

A
  • Pressure and vacuum gauges - as pressure increases the bourdon tube extends, moving the dial clockwise (measures pressure and vacuum)
  • Manometer – provides a visual representation of pressure or vacuum
  • Tachometer – measures rotational speed
  • Thermometer – measures temperature
  • Flow meter – measures rate of flow
  • Voltage meter - measures the potential difference
28
Q

what is a metallic filter

A
  • made from wire wool, thin steel plates or gauze screens.
  • They are used to remove coarser partials of contaminates from a system.
  • When block it is required for them to be cleaned and returned.
29
Q

what is a absorbent filter

A
  • made from paper, cloth, felt and other fabrics.
  • They are used to remove finer partials, used where higher standards of cleanliness is required.
  • When serviced these filters are replaced with new ones.
30
Q

what are pressure control valves

A
  • Pressure control valves maintain system pressure at designated set levels.
  • It will monitor outlet pressure and open/close as required to main a constancy
31
Q

what is rod gearing

A
  • Allows a valve to be shut manually from another location, if a space becomes unsafe to enter (flooding/fire/gas leak), these rods allow valves to be controlled from a safe location.
  • Important for them to maintained to high standard as they are commonly used on emergency equipment.
32
Q

what is the purpose of a pressure relief valve

what

A

Used to protect a system from over-pressurisation, put on outlet pump

33
Q

what is a accumulator

A
  • an energy storage device: a device which accepts energy, stores energy, and releases energy as needed.
  • Common form are hydro-pneumatic types and used in fluid power systems.
  • They can be used as a surge/pulsation dampener/absorber

RN - ETME (7 decks)

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