refrigeration and ventilation 4 Flashcards
label this diagram
what are the uses of ventilation? (5)
cooling of electronics
CBRN
habitability
main machinery space cooling
galley ventilation
why do we use fans on exhaust and supply and in which compartments?
to remove fumes and moisture in compartments where people work
found in
machinery spaces
galley’s
laundries
WC/ heads
why do we use fan supply and natural exhaust?
to supply fresh air in places like stores and workshops
natural supply/exhaust where is it used
this is only used in minor unoccupied compartments and lobbies
where do we use natural supply fan exhaust and why?
inflame, paint ,sprit stores to remove toxic or flammable gases
what type of filters do we use in ventilation? (6)
panel filters (fitted to air conditioning to remove impurities)
supply filters (fitted to Air treatment units between the plenum chamber and cooler)
grease filter(fitted in the galley to exhaust canopies)
lint filters( fitted to prevent lint accumulation)
dust filters (fitted to computers and sick bay)
flameproof gauzes (prevents flames traveling through the vents)
Certain compartments have Fire Flaps built into their exhaust trunking what are they (3)
Galleys
Main Machinery Spaces
Magazines
what areas require special filters?(6)
galleys(grease filters and fire flaps)
storerooms (panel filters)
auxiliary machinery spaces (supply filter and fire flaps )
magazines (flameproof gauzes and fire flaps)
paint stores (flame proof gauzes)
Sewage treatment plants
what are the ventilation requirements for sewage treatment plants? (3)
15 air changes per hour
separate exhaust system
excess of exhaust to supply (negative pressure)
what percentage of air is recirculated in the ATU?
67%
what percentage of fresh air is used in the ATU?
33%
what does ATU stand for?
Air Treatment Unit
what does AFU stand for?
Air Filtration Unit
what state are AFU’s used?
CBRN DC state 1 condition Zulu Alpha
citadel state.
3 stages of filtration in AFU’s?
pre particular filter (paper filter)
particulate filter (made of glass filter)
gas filter(made of charcoal)
paper filter, what does it remove?
removes coarse particulate matter including radio active fall out.
particulate filter, what does it remove?
removes particulate such as bacteria by entrapment.
gas filter, what does it remove?
remove all chemical warfare agents in the form of gasses or vapours by absorption in the active charcoal filling
what is the procedure to close down in to a citadel state? (7)
close all openings on the citadel boundary
normal ventilation on recirculation
open AFU inlets and start AFU’s
restrict access to and from the citadel
search for leaks carry out temp repairs
monitor pressure for 2 inches on the water gauge
record the results in the SEF & D171 part 2 survey report
when is the citadels integrity is checked?(4)
annually
during harbour and sea acceptance e trails
before FOST
before and after refit or major dockyard work
how do you normalise pressure between compartments
use Air bleed valve(lift at 1/2 inch on the water gauge)
how do you shut all ventilation in a emergency?
use the Crash stop button in the SCC and HQ1
what must you do before restarting the vent system?
check around the vent intake for smoke, fumes and debris.
what are the four types of refrigeration plants?
cold rooms(freezers)
cold rooms (fridges)
domestic refrigerators ( in sickbay)
ice making machines
what are the 3 types of heat transfer?
conduction(transfer through a solid)
convection(transfer through a liquid)
radiation(transfer through a gas)
what happens to a fluid if pressure changes?
if the pressure increases the volume decreases and boiling point rises(more energy required)
opposite for decrease in pressure
what is sensible heat?
the change in temperature but no change in state.
what is latent heat?
the change in state but no change in temperature
what is sub cooling?
removing the heat energy from boiling point to a solid
boiling point - 1 degrees c
what is super heating?
adding heat energy from boiling point to gas
boiling point +1 degrees c
what temperature is required for each type of fridges?
cold rooms(freezers) -18 to -22 degrees c
cool room dairy +4 to +6 degrees c
fruit and vegetable store +4 to +6 degrees c
galley ready use cupboard +5 to +7 degrees c
where does heat travel from?
hot to cold
what is the role of the compressor?
to compress the refrigerant into a HP hot gas and pump ot round the system
what is the role the condenser?
to cool the HP hot gas into a HP warm liquid
uses sea water to cool
what is the role of the thermal expansion valve?
to convert the HP cooler liquid into a LP very cold liquid
uses Bernoulli’s principle to cool the liquid by changing pressure
what is the role of the evaporator?
to convert LP cold Liquid into a LP warm gas
label the diagram
why do we compress refrigerant to make it hot to then cool it
reliable cooling in any weather
efficiency to comply with regulation
why do we fit a HP cut out after the compressor?
to trip the compressor if the discharge pressure is to high.
why is the oil separator important?
to trap any oil from the compressor that has leaked into the refrigerant lines?
what is the role of the liquid receiver?
it holds refrigerant when not needed
prevents vapour entering the TEV (liquid seal)
used for pump down
why do we fit a LP cut out before the compressor?
to trip the compressor if it lacks refrigerant to cool it>
why do we have a liquid line stop valve?
to make the system safe if there is a leak and hold it in the liquid receiver in emergencies.(wartime)
why do we fit driers to refrigerant systems?
to remove any water droplets from the refrigerant
why do we have a suction valve?
used for vacuuming down the system
why do we have a sight glass moisture indicator?
to show the state of the refrigerant
green = dry
amber = moist
shows if there is the correct amount by bubbling in the sight glass if it is low
how do you defrost a refrigerant system?
turn the system of and let it thaw naturally.
what are the 3 defrosting methods?
naturally(turn the system off and let defrost[when in port])
hot gas defrosting(use gas from the compressor to prevent ice building up 4 x 15 min max a day)
electrical heating coils(refrigerant is stopped and coils in the evaporator heat up 4 x 15 min max a day)
how do you detect leaks in a refrigerant system?(5)
inferred leak detection systems(built in to the compartment)
soapy water(snoop)
halogen leak detector
UV sensitive coloured dye (Spectrolyne dye)
visual ( looking for oil)
what oils do we use in refrigerant systems?(3)
OM70 - used with CFC/HCFC machines
SUNISO 3GS - T boats and type 23’s
SW 68 - a synthetic R134a refrigerants
what does hygroscopic mean?
attracts water and moisture.
why are yellow brakes better then red?
because they slow down quicker.
what are the 3 gases associated with the Kyoto protocol?
HFC’s
PFC’s
CO2
what does the Montreal cover?
The ban and regulation of refrigerant that deplete the ozone layer.
how do you remember what refrigerants are covered under which protocol?
2 c’s = banned under the Montreal protocol (contains chlorine)
1 c = regulated under the Kyoto protocol
what gas are associated with the Montreal protocol?
CFC’s
HCFC’s
Halons
what do chilled water plants cool?
weapon systems
radar
ships computer system
air treatment units
what replaces the evaporator in the chilled water system?
The chiller
what two parts of the chilled water system are cooled with sea water?
the compressor motor
the condenser
what are the hazards of refrigerant plants?
displace air
CFC refrigerants make phosgene gas after heating (mustard gas)
CO2 from fruit and veg
frost bite
what is required to enter a fridge space?(9)
inform rating in charge of the compartment
man below tally
Breathing apparatus out side space
exhaust fans on
no smoking
test IRLDS before entrance
trapped personnel lamp outside
safety number outside
check door mechanism works
what should you do if you get refrigerant in your eyes?
wash out with clean water
then go to sickbay
what is the most common refrigerant in the RN?
R134a
