Mechanical Theory 4 Flashcards
explain the pressure/volume relationship
- Low pressure – volume increase – less energy required
- High pressure – volume decreases – more energy required
briefly explain heat transfer
- Conduction – direct contact through solid
- Radiation – energy transfer through air
- Convection – energy transferred through fluid
breifly explain latent heat
temperature stays the same but the state changes
briefly explain sensible heat
increase of temp but state stays the same
briefly explain super heat
any temperature above the boiling point
explain the purpose of the compressor
- Raises the pressure of refrigerant
- (no liquid should enter the compressor – liquids cannot be compressed)
- Refrigerant leaving the compressor is a high-pressure hot gas
- Motive force
- Positive displacement pump
- Quadrant 1 – high pressure, hot gas
explain the purpose of the condenser
- Condenses the hot gas into a warm, high pressure liquid
- Must be a liquid on leaving the condenser
- Use sea water as a cooling medium
- Quadrant 2 – high pressure, warm liquid
explain the purpose of the evaporator
- Cold liquid refrigerant enters the evaporator
- Leaves as a gas
- Quadrant 4 – low pressure, cool gas
explain the purpose of the thermal expansion valve
- rate of flow – can increase/decrease
- Lowers the pressure
- Still stays as a fluid
- Thermometer – sense temp in refrigeration room – controls the rate of flow, to increase / decrease temp
- Quadrant 3 – low pressure, very cold liquid
what is the purpose of the moisture indicating sight glass
- Visible indication of refrigerant flow / shows presence of any moisture
- Green – indicates dry
- Yellow – indicates moisture
explain the montreal protocol agreement
Bunch of countries come together to control where refrigerants can be released
- CFC
- HCFC
- HALONS
explain the kyoto summit agreement
Reduce and limit greenhouse gases
* CO2
* HFC
* PFC
state five methods refrigeration leak detection
- Infra red leak detection system (IRLDS)
- Oil slicks
- Spectrolyne and UV lamp
- Snoop
- Halogen leak detector
state 3 oils used in a refrigeration system
- OM- 70
- SUNISO 3GS
- SW68
from what source should oil be used
fresh unopened
what should happen to oil after use
how can oil be added to a refrigeration system
what systems are supplied with chilled water
- weapon systems
- radar
- ships computer systems
- air treatment units
what is the main difference betwen refrigeration and chilled water system
what provides cooling for the condenser and motors
sea water
the system has its own, seperate sea water pumps
when will phosgene gas be created
produced if the refrigerant comes into contact with heat
mustard gas - it is toxic
what is given off if fruit & veg decomposes
as they degrade CO2 is produced
displaced oxygen in the air
what is the procedure for entering a refrigeration compartment
*duty of the watch is to be informed that personnel are entering the compartment, & informed when the compartment is vacated.
* Breathing Apparatus is available
* high and low exhaust fans are running.
* No smoking. hot work is to be very closely controlled.
* Infra Red Leak Detections System (IRLDS) is working correctly & indicating safe.
* personnel trapped warning lamps are working
what should you do if you get refrigerant in your eyes
flush with running clean water, then after seek medical attention
state 5 uses of ventilation
- Cooling of electronic equipment
- CBRN
- Habitability
- Main machinery space cooling
- Galley ventilation
explain the 4 methods of ventilation configuration
Fan supply and fan exhaust
* removes large quantities of wild heat, moisture fumes coupled with the requirements to provide fresh air to personal working
* Machinery spaces, galley’s, laundries, W.C
Fan supply and natural exhaust
* Supply of fresh air to compartments is the primary objective
* Store rooms and workshops
Natural supply and fan exhaust
* Removal of noxious gases and flammable vapours is the primary object
* Paint stores, spirit rooms, inflame store
Natural supply and natural exhaust (barely used)
* Only used in minor unoccupied compartments and lobbies
state 6 types of filter
- panel filter
- supply filter
- grease filter
- lint filter
- dust filter
- flameproof gauzes
state 5 spaces that require special filters
- Galleys
- Store rooms
- Auxiliary machinery spaces
- Sewage treatment spaces
- Magazines
explain the requirements of a vent system in a STP space
- 15 air changes in 1 hr
- Low level exhaust
- More exhaust than supply
which compartments would require fire flaps
- Galley
- Main machinery spaces
- Magazines
what percentage of air is Fresh / re-circulated
fresh- 33%
re-circulated - 67%
what NBCD state would AFU be used
state 1 - zulu alpha
explain 3 types of filter found in a AFU
- Pre-particulate filter - paper filter – removes coarse particulates
- Particulate filter – glass fibre – remove particulates such as bacteria by entrapment
- Gas filter – activated charcoal filling - remove all known chemical warfare agents
what is the citadel
- Whole ship chemical, biological and nuclear shelter
- Formed by closing the ship down to an increased gas tight state
- Works by increasing the atmospheric pressure within the ship above external using air filtered by AFU
when would the citadel be tested
- Annually
- Prior to DED (docking extended duration)
- During harbour acceptance trials (HATS)
- During sea acceptance trials (SATS)
when would an air Bleed valve operate
where would a crash stop board be situated
SCC/HQ1
when would the fans be restarted after a crash stop
when would a crash stop be used
in the event of a fire, crash on deck
