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Mechanical > Theory 4 > Flashcards

Theory 4 Flashcards

1
Q

Describe the relationship between pressure and volume

A

As pressure increases, volume decreases or vice versa

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2
Q

Describe the relationship between boiling point and pressure

A

As pressure decreases boiling point decreases or vice versa

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3
Q

What are 3 methods of heat transfer?

A
  • Convection
  • Conduction
  • Radiation
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4
Q

How does heat travel?

A

Hot –> cold

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5
Q

What is it called when the temperature of a material increase but the state doesn’t changes?

A

Sensible heat

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6
Q

What is it called when the temperature of a material stays the same but the state changes?

A

Latent heat

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7
Q

What is superheating?

A

Substances temperature goes above its boiling point

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8
Q

What is subcooling?

A

Cooling a substances below its boiling point

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9
Q

Name the examples of the on-board refrigeration plants

A
  • Cold room
  • Cool room dairy
  • Fruit and veg store
  • Galley ready use cupboard
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10
Q

What is the temperature range of the cold room?

A

-18 –> -22 degrees C

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11
Q

What is the temperature range of the cool room dairy?

A

4 –> 6 degrees C

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12
Q

What is the temperature range of the fruit and veg store?

A

4 –> 6 degrees C

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13
Q

What is the temperature range of the Galley ready use cupboard?

A

5 –> 7

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14
Q

What are the 4 components of the refrigeration cycle?

A
  • Compressor
  • Condenser
  • Thermal expansion valve (TEV)
  • Evapourator
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15
Q

Describe the compressor

A
  • Cool gas enters the compressor
  • Compresses the gas to form a high pressure, high temperature gas
  • Provides the motive force in the cycle
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16
Q

Describe the condenser

A
  • High pressure hot gas is condensed into a high pressure liquid
  • Subcooling is used to ensure all gas is converted to liquid
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17
Q

Describe the Thermal Expansion Valve (TEV)

A
  • Slows the flow rate of the refrigerent
  • Lowers the pressure and temperature
  • TEV senses the temperature of refrigerant leaving the evaporator to control the flow of the refrigerant
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18
Q

Describe the evaporator

A
  • Evaporates the liquid to a gas
  • Superheats the refrigerant so no liquid enters the compressor
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19
Q

What does the HP cut out do?

A

Shuts down the plant if the pressure gets to high

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20
Q

What does the oil seperator do?

A

Seperates the oil from the refrigerant and directs the oil back to the compressor sump

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21
Q

What does the liquid reciever do?

A

Stores liquid refrigerant for maintainance

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22
Q

What does the drier do?

A

Removes any moisure from the refrigerant liquid

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23
Q

What does the sight glass indicator do?

A

Green indicates, its dry
Yellow indicates its wet

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24
Q

What are the 3 defrosting methods?

A
  • Natural defrosting
  • Hot gas defrosting
  • Electric heating coil
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25
Q

How often do you defrost refrgeration plants using natural defrosting?

A

Every 3-6 months

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26
Q

How often do you defrost refrgeration plants using hot gas defrosting?

A

4x15min per day

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27
Q

How often do you defrost refrgeration plants using electrical heating coil?

A

1 hour per day

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28
Q

What gases does the monteal protocol aim to phase out production and use of?

A
  • CFCs
  • HCFCs
  • Halons
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29
Q

What gases does the kyoto summit agreement aim to phase out production and use of?

A
  • CO2s
  • HFCs
  • PFCs
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30
Q

What are the mothods of leak detection?

A
  • Infrared leak detection system
  • Oil slicks
  • Spectrolyne dye and UV
  • Snoop
  • Halogen leak detector
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31
Q

What oils are commonly used in RN refrgeration plants?

A
  • OM70
  • SUNISO 3GS
  • SW68
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32
Q

What does Hygdroscopic mean?

A

Readily absorbs moisutre

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33
Q

Why are open/ damaged cans of oil to be discarded?

A

To avoid contamination with moisture from the air

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34
Q

How can oil be added to the sump in refrigeration plants?

A
  • Sump filter plug
  • Hand pump
  • Dosing Pot
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35
Q

What does the chilled water plants provide cooling for?

A
  • Wepons systems
  • Radars
  • Ships computer system
  • Air treatement unit
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36
Q

What is the difference between the chiller system and refrigeration system?

A

Has a chillar instead of the evapourator

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37
Q

What is used to cool the condenser and motor?

A

Sea water

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38
Q

Why are refrigerent vapours dangerous?

A

Displace the oxygen in the compartment as refrigerents tend to be heavier than oxygen so will sink to lower areas of the compartments

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39
Q

What gas is produced when refrigerents come in contact with heat?

A

Phosgene gas
(mustard gas)

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40
Q

What gas is produced when fruit and veg start to degrade?

A

CO2

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41
Q

What proceedures need to be carried out before entering the refrigeration compartment?

A
  • People are to be informed before entering the compartment
  • Breathing apparatus avaliable
  • High and low exhaust fans are running
  • No smoking anywhere is compartment
  • Ensure the infrared leak detection system is working correctly
  • Personnel trapped warning lights are in working order
  • Ensure there is a sensory
  • Ensure the internal door opening mechanism is working correctly
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42
Q

What do you do if you get refrigerent in eyes?

A

Flush with water and report to medbay

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43
Q

What do you do if you get refrigerent on the skin?

A

Wash off immediately and report to medbay

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44
Q

What equipment and uses require ventillation?

A
  • Cooling of electronic equipment
  • CBRN
  • Habitability
  • Main machinary space cooling
  • Galley Ventillation
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45
Q

What are the configurations of ventillation?

A
  • Fan supply and fan exhaust
  • Fan supply and natural exhaust
  • Natural supply and fan exhaust
  • Natural supply and natural exhaust
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46
Q

Where and why is fan supply and fan exhaust used?

A

Remove large quantities of air and provide fresh air for personnel working in the compartments
Machinary Space, galley, laundry, bathrooms

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47
Q

Where and why is fan supply and natural exhaust used?

A

Supply of fresh air is priamry objective
Store rooms and workshops

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48
Q

Where and why is natural supply and fan exhaust used?

A

Removable of noxious gases and flammable vapours is primary objective
Paint shops, Inflam stores, spirit rooms

49
Q

Where is natural supply and natural exhaust used?

A

Minor unoccupied compartments and lobbies

50
Q

Name the common filters

A
  • Lint filters
  • Panel filters
  • Dust filters
  • Supply filters
  • Grease filters
  • Flameproof gauzes
51
Q

Where are the special filters fitted?

A
  • Galleys
  • Store rooms
  • Auxillary machinary spaces
  • Magazines
  • Paint stores
52
Q

Which compartments have fire flaps built into exhaust trunking?

A
  • Galleys
  • Main machinary spaces
  • Magazines
53
Q

What are the requirements of a ventillation system in an STP space?

A
  • 15 air changes an hour
  • Low level exhaust system
  • Excess of exhaust capacity from that of supply
54
Q

What are the percentages of air used in the ATUs?

A
  • 33% fresh air
  • 67% recirculated air
55
Q

What do AFUs consist of?

A
  • Preparticulate filter –> paper filter that removes all coarse particles
  • Particulate filter –> fibre glass that removes bacteria
  • Gas filter –> charcoal removes all known chemical warfare
56
Q

How does Citadel work?

A
  • A whole ship chemical, biological and nuclear shelter
  • By closing the ship down to an increased gas tight state
  • Increasing atmospheric pressure within the shipabove external pressures by using AFUs
57
Q

When are citadel tests carried out?

A
  • Annually
  • Prior to DED ( Docking extended duration)
  • During harbour acceptance trials (HATs)
  • During sea acceptance trials (SATS)
  • During FOST workup
58
Q

What pressure is needed for the citadel to be effective

A

2” WG

59
Q

When does the air bleed valve lift?

A

When air pressure exceeds 1/2” WG

60
Q

When are AFUs used?

A

CBRNDC State 1 condition alpha zulu

61
Q

When is the crash stop used?

A

When all fans need to be stopped in case of an emergancy e.g fire/explosion

62
Q

Where is the crash stop operated from?

A

SCC/ HQ1

63
Q

When are the fans restarted?

A

When checked that they are clear of smoke and debris?

64
Q

What is the definition of a fluid?

A
  • Substance that will readily take the shape of its container
  • Capable of transmitting power
  • Liquid or gas
65
Q

What are the advantages of hydraulics?

A
  • Reliable
  • Simple,easy to understand
  • Infinite speed range
  • Easily reversed
  • Abitlity to withstand overload
  • No sparks risk
  • High torque at low speeds
  • 1/12 size of equivilant electric motor
66
Q

What are the disadvantages of hydraulics?

A
  • Fire risk with mineral oil systems
  • Noise
  • Risk of contamination
  • Less efficient (85-95%)
67
Q

What does denso steel working mastic give off when ignited?

A

Toxic gas

68
Q

Where is denso steel working mastic stored?

A

Flammable store

69
Q

Where is denso steel working mastic used?

A

Upper deck for hydraulic fittings

70
Q

What is in pipework sealing joints and what are they made of?

A

O-Rings
made of fluorocarbon elastomers

71
Q

What does fluorocarbon elastomers give off when heated above 300 degrees C?

A

Toxic gases including hydrogen fluoride

72
Q

What PPE is required when working with fluorocarbon elastomers?

A
  • PVC gauntlets
  • Rubber boots
  • PVC coveralls
  • Full face visor
73
Q

What are the overall health and safety risks when working with hydraulics?

A
  • Hydraulic fluid can cause skin irritation
  • Change oil soaked clothes immediately
  • Any skin irritation should be reported to medbay
  • Always consult Hazard data sheet
  • Mineral oil is a fire hazard, leaks cleaned up immediately
  • Flexi hoses in date for test
  • Gauge glass valves to be shut when not in use
  • suitable precautions to be taken before welding or burning in the vicinity
74
Q

What are the 2 types of hydraulic fluid?

A
  • Petroleum based
  • Synthetic based
75
Q

Which oils are used in hydraulic systems?

A
  • OM33
  • OX40
  • OX30
76
Q

What colour is OX30?

A

Red

77
Q

What colour is OM33?

A

Orange/yellow

78
Q

What colour is OX40?

A

Green

79
Q

What are the requirements for hydraulic oil?

A
  • Be incompressible, transmit power effectively
  • Good lubrication properties
  • Good sealing properties
  • Give up heat readily
80
Q

What does demulsibility mean?

A

The ability of a fluid to seperate out from water

81
Q

What are the most common types of oil contamination?

A
  • Airborne particles and moisture
  • Construction dirt
  • Dirt in new fluid
  • Dirt produced by wearing in new system
  • Dirt from human sources
82
Q

What methods are used to reduce contamination?

A
  • Good system design
  • filtration and filter maintainance
  • Operation of filter and clogging indicators
  • Good working practices
  • Guardian filter pack
  • Caps should be fitted to open pipework
  • Clean working area
83
Q

What compoents are in the anchor windless hydraulic system?

A
  • Tank
  • Filters
  • Relief valve
  • Cooler
  • Pressure guages
  • Valves
  • Non return valves on discharge side
  • Float switch
  • Pump
  • Contol vlave
  • Actuator
84
Q

What type of pump is used in the hydraulic system?

A

Positive displacement

85
Q

What types of positive displacement pumps are used?

A
  • External gear pump
  • Internal gear pump
  • Vane pump
  • Lobe pump
  • Single piston pump
  • Multi piston pump
86
Q

What does the control valve do?

A

Controls oil flow and direction

87
Q

What does an actuator do?

A

Reverts hydraulic pressure into mechanical motion?

88
Q

What is the purpose of the drain leg?

A

To return cooling oil and sealing oil from the actuator to the tank

89
Q

What is an acumulator?

A

A device in which potential energy is held and smooths out pulsations

90
Q

What are two types of accumulator?

A
  • Bag
  • Piston
91
Q

What are axial piston pumps used in?

A
  • Stabiliser systems
  • CPP systems
  • Steering systems
92
Q

What is fresh water used for?

A
  • laundry
  • Galley
  • Showers and sinks
  • Water heaters
  • Medical use
  • Bridge window washers
  • Fresh water hose reals
  • Machinary cooling
  • Gas turbine washing
93
Q

What is desalinated (made water) called?

A

Permeate

94
Q

What is waste water after desalination called?

A

Concentrate

95
Q

What does TDS stand for?

A

Total dissolved solids

96
Q

What is the TDS of sea water?

A

34,000ppm

97
Q

What is the TDS of the permeate?

A

250-300ppm

98
Q

How much of the supplied sea water is ejected overboard?

A

80%

99
Q

What is the TDS of the ejected concentrate?

A

56,000ppm

100
Q

What does the bag filter filter down to?

A

60 microns

101
Q

What does the cartridge filters filter down to?

A

10 microns

102
Q

What pump is used in the reverse osmosis plant?

A

HP, 3 piston, positive displacement pump

103
Q

What pressure does the pump in the reverse osmosis plant operate at?

A

65 Bar

104
Q

What does the concentration control valve do?

A
  • Can be opened or closed
  • Forcing more or less water through the membranes
  • Controls the TDS of the permeate
105
Q

What anti-scalent is used in fresh water systems?

A

Hypersperse

106
Q

What are the chlorine levels in the fresh water tank maintained at?

A

0.2ppm

107
Q

Who authorises/ supervises any addition of chlorine to fresh water tanks?

A

Section head

108
Q

When are chlorine levels tested?

A

Daily and before embarkation

108
Q

When are chlorine levels tested?

A

Daily and before embarkation

109
Q

What colour are fresh water hoses?

A

Blue

110
Q

What needs to be done to fresh water hoses before they are used?

A

Flush them

111
Q

What needs to be done to fresh water hoses before they are used?

A

Flush them

112
Q

What are the tests carried out on fresh water?

A
  • CHEMets test (Chlorine)
  • Visual
  • Taste
113
Q

How often do you carry out a CHEMets test?

A

Daily and before embarkation

114
Q

How do you record the levels in the fresh water tank?

A

Sounding tube
Dip tape and conversion chart

115
Q

How do you get hot fresh water onboard ship?

A

Calorifier

116
Q

What does the air eliminator do?

A

Eliminates air and prevents water hammer

117
Q

When are fresh water levels checked?

A

Hourly

118
Q

Where are fresh water levels recorded?

A

SCC

Mechanical (2 decks)

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