Refrigeration and ventilation Flashcards
The main refrigeration plant comprises of:
- Cold rooms and cool rooms
- domestic refrigerators
- ice making machines
How do you make water boil at a higher boiling point?
Increase the pressure on it
How do you lower the boiling point?
Decrease the pressure on it
What temperature does water boil at?
100 degrees
What are the three methods of heat transfer and describe each one
- Conduction - the transfer of heat between two solid bodies
- Convection - moving heat using air
3 . Radiation - the electromagnetic transfer of energy
What three forms can water exist in?
Solid (ice)
Liquid (water)
Gas (vapour)
What is sensible heat?
Temperature rises but no change of state
What is latent heat
No change in temperature but the state changes
What is superheat
The heat added above boiling point (100 degrees for water)
What is sub cooling
The removal of heat
What temp is the cold room
-18 to -22 degrees
What temp is the cool room
4 to 6 degrees
What temp is the fruit and veg store
4 to 6 degrees
What temp is the galley ready use cupboard
5 to 7 degrees
4 components of the refrigeration system in order
Compressor
Condenser
TEV
Evaporator
What does TEV stand for
Thermal expansion valve
How does the TEV work
Slows the flow rate of the refrigerant to lower the temperature and pressure
What does the HP cut out do
Protects the compressor if the discharge pressure gets too high
What does the oil separator do
Separates oil from the refrigerant
What does the liquid receiver do
Provides a liquid seal between the condenser and the TEV
What does the liquid line stop valve do
Shutting the valve prevent refrigerant leaving the liquid receiver
What does the drier do
Removes moisture
What colour means what on the sight glass indicator
Green - indicates dry
Yellow - indicates moisture
What does the LP cut out do
Stops the compressor if pressure gets too low on the suction side
What is the Montreal protocol 1987
An arrangement to phase out the use of all harmful CFC gases
3 ozone depleting substances
- CFC
- HCFC
- HALONS
What is the Kyoto summit
Reduce greenhouse gases
Methods of leak detection
- infra red leak detection system (IRLDS)
- oil slicks
- spectrolyne dye and UV lamp
- snoop
- halogen leak detector (very sensitive)
What needs lubrication
The compressor
3 lubricants
- OM70
- SUNSIGO 3GS
- SW68
What does hygroscopic mean
Absorbs moisture
How big are the cans of oil and what is the rule?
500ml to 5ltr
Only use the smallest can required
How can oil be added to the sump
- sump filler plug
- hand pump
- dosing pot
What do chilled water plants provide cooling for
- weapons systems
- radars
- ships computer system
- air treatment units (ATU)
What is a chilled water plant called
Chiller
What temp does the chilled water leave and return at
Leaves at 4-6 degrees
Returns at 13-20 degrees
How is phosgene gas (mustard gas) produced
If CFC refrigerant come into contact with a high heat source
What procedures must you carry out before entering the refrigeration machinery room?
- someone knows where you are
- breathing apparatus is available
- fans are running
- no smoking
- IRLDS is working
- warning lights are working
- you have a sentry
- the door mechanism works
Uses of a ventilation system
- cooling of electronic equipment
- CBRN
- Habitability
- main machinery space cooling
- galley ventilation
What are the four combinations of supply and exhaust ventilation and where are they used
- Fan supply and fan exhaust - used in machinery spaces, galleys laundries, WCs and bathrooms
- Fan supply and natural exhaust- used in store room and workshops
- Natural supply and fan exhaust- used in paint stores, spirit rooms and Inflam stores
- Natural supply and natural exhaust- used in minor unoccupied compartments and lobbies
6 Types of filters
- panel filters
- supply filters
- grease filters
- lint filters
- dust filters
- flameproof gauzes
What compartments require special filters
Galley
Store room
Auxiliary machinery spaces
Magazines
Paint stores
What compartments have fire flaps
Galleys
Main machinery spaces
Magazines
What areas need special requirements
- Galleys
- Store rooms
- Auxiliary machinery spaces
- Sewage treatment spaces (require 15 changes per hour)
- magazines (fitted with there own air conditioning which allows 100% treated fresh air)
The AFU consists of 3 sections which are:
- pre particulate filter (paper filter removed coarse particles)
- particulate filter (made of glass givers to remove bacteria)
- gas filter (removes chemical)
when are citadel tests carried out
- annually
- prior to DED (dicking extended duration)
- during harbour acceptance trials
- during sea acceptance trials
- during a FOST work up
how is a citadel test conducted
- Close all openings on the Citadel boundary and put system on re-circ
- Open AFU inlets and start AFUs
- Restrict access to and from Citadel to essential personnel only. AIRLOCKS MUST BE USED.
- Search for leaks and carry out temporary repairs.
- Record the result of the test in the SEF & D171 Part II survey report
where is the crash stop board
SCC/HQ1
what is the crash stop
built into the ventilation system to allow fans to be stopped in case of an emergency
whats Michael Dents middle name?
John William
What is natural defrosting and when is it done
Turn the fridge off and it’s carried out every 3-6 months or when the ship will de-store
What is hot gas defrosting and when is it carried out
Uses hot high pressure vapour which is passed through the evaporator. Carried out for 4 15 minute sessions throughout the day
How do you defrost using electrical heating coils and when is it done
Uses either rod type or wrap around coils in the evaporator. Carried out for a maximum of 1 hour (to prevent the oil from burning)
