Theory 4 Flashcards
describe the relationship between pressure and volume
as pressure increases, volume decreases or vice versa
describe the relationship between boiling point and pressure
As pressure decreases boiling point decreases or vice versa
what are 3 methods of heat transfer?
- convection
-conduction
-radiation
how does heat travel?
hot —> cold
what is it called when the temperature of a material increases but the state doesn’t change?
sensible heat
what is it called when the temperature of a material stays the same but the state changes?
latent heat
what is superheating?
substances temperature goes above its boiling point
what is sub cooling?
cooling substances below its boiling point
name the examples of the on-board refrigeration plants
- cold room
-cool room dairy
-fruit and veg store
-galley ready use cupboard
what is the temperature range of the cold room?
-18 —> -22 degrees C
what is the temperature range of the cool dairy room?
4 —>6 degrees C
what is the temperature range of the fruit and veg store?
4 —>6 degrees C
what is the temperature range of the galley ready to use cupboard?
5 —>7 degrees C
what are the 4 components of the refrigeration cycle?
- compressor
- condenser
- thermal expansion valve (TEV)
- evaporator
describe the compressor
- cool gas enters the compressor
- compresses the gas to form a high pressure, temperature gas
- provides the motive force in the cycle
describe the condenser
- high pressure hot gas is condensed into a high pressure liquid
- sub-cooling is used to ensure all gas is converted to liquid
describe the thermal expansion valve (TEV)
- slows the flow rate of the refrigerant
-lowers the pressure and temperature - TEV senses the temperature of refrigerant leaving the evaporator to control the flow of the refrigerant
describe the evaporator
- evaporators the liquid to a gas
-superheats the refrigerant so no liquid enters the compressor
what does the HP cut out do?
shuts down the plant if the pressure gets to high
what does the oil separator do?
separates the oil from the refrigerant and directs the oil back to the compressor sump
what does the liquid receiver do?
store’s refrigerant for maintenance
what does the drier do?
removes any moisture from the refrigerant liquid
what does the sight glass indicator do?
green indicates, its dry
yellow indicates its wet
what are the 3 methods of defrosting?
- natural defrosting
- hot gas defrosting
- electric heating coil
how often do you defrost refrigeration plant using natdefrosting?
every 3-6 months
how often do you defrost refrigeration plants using hot gas defrosting?
4x15 mins per day
how often do you defrost refrigeration plants using electrical heating coil?
1 hour per day
what gases does the motels protocol aim to phase out of production and use of ?
- CFCs
-HCTCs
-halons
what gases does the Kyoto summit agreement aim to phase out production and use of?
-CO2
-HFCs
-PFCs
what are the methods of leak detection ?
- infrared leak detection system
-oil slicks
-spectrolyne dye and UV - snoop
-halogen leak detector
what oils are commonly used in RN refrigeration plants?
- OM70
-SUNISO 3GS
-SW68
what does Hydroscopic mean?
readily absorbs moisture
why are open/damaged cans of oil to be discarded?
to avoid contamination with moisture from the air
how can oil be added to the sump in refrigeration plants?
- sump filter plug
-hand pump
-dosing pot
what does the chilled water plants provide cooling for?
- weapons systems
-radars
-ships computer systems - air treatment unit
what is the difference between the chiller system and refrigeration system?
has a chiller instead of the evaporator
what is used to cool the condenser and motor?
sea water
what are refrigerant vapours dangerous?
displace the oxygen in the compartment as refrigerants tend to be heavier than oxygen so will sink to lower ares of the compartments
what gas is produced when refrigerants come into contact with heat?
Phosgene gas
(mustard gas)
what gas is produced when fruit and veg start to degrade?
CO2
what procedures need to be carried out before entering the refrigeration compartment?
- people are to be informed before entering the compartment
-breathing apparatus available
-high and low exhaust fans are running - no smoking anywhere in the compartment
- ensure the infrared leak detection system is working correctly
- personal trapped warring lights are in working order
-ensure there is a sensory
-ensure the internal door opening mechanism is working correctly
what do you do if you get refrigerant in your eyes?
flush with water and report to medbay
what do you do if you get refrigerant on the skin?
wash off immediately and report to medbay
what equipment and uses require ventilation?
-cooling of electronic equipment
-CBRN
-habitability
-main machinery space cooling
- galley ventilation
what are the configurations of ventilation?
-fan supply and exhaust
-fan supply and natural exhaust
-natural supply and fan exhaust
-natural supply and natural exhaust
where and why is fan supply and fan exhaust used?
removes large quantities of air and provide fresh air for personnel working in the compartments
machinery space, galley, laundry, bathrooms
where and why is fan supply and natural exhaust used?
supply of fresh air is primary objective
store rooms and workshops
where and why is natural supply and fan exhaust used?
removable of noxious gases and flammable vapours is primary objective
paint shops, inflam stores, sprit rooms
where is is natural supply and natural exhaust used?
minor unoccupied compartments and lobbies
name the common filters
- lint filters
-panel filters
-dust filters - supply fliters
-grease fliters
-flameproof gauzes
where are the special filters?
-galleys
-store rooms
-axillary machinery spaces
- magazines
-paint stores
which compartments have fire flaps built into exhaust trunking?
- galleys
-main machinery spaces
-magazines
what are the requirements of a ventilation system in an STP space?
- 15 air changes an hour
- low level exhaust system
- excess of exhaust capacity from that supply
what are the percentages of air used in the ATU’s?
-33% fresh air
- 67% recirculated air
what do AFUs consist of?
- preparticulate filter –> paper filters that remove all course particles
- particulate filter –> fibre glass that removes Bactria
- gas filter –> charcoal removes all known chemical warfare
how does Citadel work?
- 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
when are Citadel tests carried out?
- annually
-prior to DED (Docking extended duration)
-During harbour acceptance trials (HATs)
-During sea acceptance trials (SATS) - During FOST workup
what pressure is needed for the citadel to be effective?
2”WG
when does the air bleed valve lift?
when air pressure exceeds 1/2 “WG
when are AFUs used?
CBRNDC State 1 condition alpha zulu
when is the crash stop used?
when all fans needed to be stopped in case of an emergency e.g. fire/explosion
where is the crash stop operated from?
SSC/HQ1
when are the fans restarted?
when checked that they are clear of smoked and debris
what is the definition of a fluid?
- substance that will readily take the shape of its container
- capable of transmitting power
-liquid or gas
what are the advantages of hydraulics?
- reliable
-simple, easy to understand
-infinite speed range - easily reversed
-ability to withstand overload - no sparks risk
-high torque at low levels - 1/12 size of equivalent electric motor
what are the disadvantages of hydraulics?
- fire risk with mineral oil systems
-noise
-risk of contamination
-less efficient (85-95%)
what does denso steel working mastic give off when ignited?
toxic gas
where is denso steel working mastic stored?
flammable store
when is denso steel mastic used?
upper deck for hydraulic fittings
what is in pipework sealing joints and what are they made of?
O-rings
made of flurocarbon elastomers
what dose fluorocarbon elastomers give off when heated above 300 degrees C?
toxic gases including hydrogen fluoride
what PPE is required when working with flurocarbon elastomers?
- PVS gauntlets
-rubber boots
-PVC coveralls
-full face visor
what are the overall health and safety risks when working with hydraulics?
- 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
what are the 2 types of hydraulic fluid?
- petroleum based
-synthetic based
which oils are used in hydraulic systems?
- OM33
-OX40
-OX30
what colour is OX30?
Red
what colour is OM33?
Ornage/yellow
What colour is OX40?
Green
What are the requirements for hydraulic oil?
- be incompressible, transmit power effectively
- food lubrication properties
-good sealing properties
-give up heat readily
what does demulsibility mean?
the ability of a fluid to separate out from water
what are the most common types of oi contamination?
- airborne particles and moisture
-construction dirt
-dirt in new fluid
-dirt produced by wearing in new systems - dirt from human sources
what methods are used to reduce contamination?
- good system design
- filtration and filter maintenance
- operation of filter and clogging indicators
- good working practices
-guardian filter pack
-caps should be fitted to open pipework
-clean working area
what components are in the anchor windless hydraulic system?
tankk
filters
relief valve
cooler
pressure gauges
valves
non return on discharge side
float switch
pump
control valve
actuator
what type of pump is used in the hydraulic system?
positive displacement
what types of positive displacement pumps are used?
- external gear pump
-internal gear pump - vane pump
-lobe pump
-single piston pump
-multi piston pump
what does the control valve do?
controls oil flow and direction
what does an actuator do?
reverts hydraulic pressure into mechanical motion
what is the purpose of the drain leg?
to return cooling oil and sealing oil from the actuator to the tank
what is an acumulator?
a device in which potential energy is held and smooths out pulsations
what are two types of accumulators?
- bag
-piston
what are axial piston pumps used in?
- stabiliser systems
-CPP sytsems - steering systems
what is fresh water used for?
- laundry
-galley
-shower and sinks
-water heaters
-medical use
-bridge window washers
-fresh water hose reals - machinery cooling
- gas turbine washing
what is desalinated (made water)called?
permeate
what is waste water after desalination called?
concentrate
what does TDS stand for?
total dissolved solids
what is the TDS of sea water?
34,000ppm
what is the TDS of the permeate?
250-300ppm
how much of the supplied sea water is ejected overboard?
80%
what is the TDS of the ejected concentrate?
56,00ppm
what does the bag filter, filter down to?
60 microns
what does the cartridge filter, filter down to?
10 microns
what pumps is used in the reverse osmosis plant?
HP
3 piston
positive displacement pump
what pressure does the pump in the reserve osmosis plant operate at?
65 Bar
what does the concentration valve do?
- can be open or closed
-forcing more or less water through the membranes - controls the TDS of the permeate
what anti-scalent is used in fresh water systems?
hyperspere
what are the chlorine levels in the fresh water tank maintained at?
0.2 ppm
who authorises/ supervises any addition of chlorine to fresh water tanks?
section head
when are chlorine levels tested?
daily and before embarkation
what colour are fresh water hoses?
blue
what needs to be done to fresh water hoses before they are used?
flush them
what are the tests carried out on fresh water?
- CHEMets test (chlorine)
-visual
-taste
how often do you carry out CHEMets test?
daily and before embarkation
how do you record the levels in the fresh water tank?
sounding tube
dip tape
conversion chart
how do you get hot fresh water onboard ship?
calorifier
what does the air eliminator do?
eliminates air and prevents water hammer
when are fresh water levels checked?
hourly
where are fresh water levels recorded?
SCC
