Refigeration Flashcards
(123 cards)
1
Q
What is stored in coldrooms?
A
Storage of food, which has to be kept frozen.
2
Q
What is stored in a cool rooms?
A
Storage of food, which has to be kept chilled.
3
Q
Where are there domestic refrigerators found onboard?
A
Sickbay and Mess decks.
4
Q
What is kept on board for medical purposes (Burns and heat exhaustion)?
A
Ice making machines.
5
Q
What environmental factor affects the temperature at which a liquid will boil?
A
Pressure.
6
Q
If the pressure is increased will the boiling point increase or decrease?
A
BP will increase.
7
Q
If the pressure is decreased, will the boiling point increase or decrease?
A
BP will decrease.
8
Q
What are the three modes of heat transfer?
A
Conduction, Convection and Radiation
9
Q
What is the definition of conduction?
A
Heat energy is transferred by direct contact.
10
Q
What is the definition of Convection?
A
Heat energy is transferred by tge mass motion of molecules.
11
Q
What is the definition of Radiation?
A
Heat energy is transferred by electromagnetic radiation.
12
Q
What are the three ‘forms’ a substance exists as?
A
Solid, Liquid, and Gas.
13
Q
What is sensible heat defined as?
A
Temperature rises, but there is not change in the state of the substance.
14
Q
What is latent head defined as?
A
Temperature remains constant, but there is a change in the state of the substance.
15
Q
On the temperature vs. heat graph, what is sensible heat represented as?
A
A sloped line moving from the bottom left to the top right.
16
Q
On the temperature vs. heat graph, what is latent heat represented as?
A
A flat line parallel to the x-axis.
17
Q
Define superheated?
A
Any increase in temperature of a gas above the boiling point temperature.
18
Q
Define sub-cooling
A
A decrease in temperature below the Boiling point. (i.e. steam that is sub-cooled by 10 degrees will bring the gas to 90 degrees celcius.)
19
Q
At what temperature and what is stored in a cold room?
A
-18 to -22 Celcius, Meat, fish, chicken stored.
20
Q
At what temperature and what is stored in a cool room diary?
A
+4 to +6 celcius. Butter, milk and other diary products stored.
21
Q
At what temperature and what is stored in a Fruit and Veg. store?
A
+4 to +6 degrees C. Stored fruit and vegetables.
22
Q
At what temeprature and what is stored in a Galley Ready Use Cupboard?
A
+5 to +7 degrees C. Mostly keep galley supplies and ready-to use items or items of convenience.
23
Q
Do modern refrigerants have a boiling point below zero?
A
Yes, R134A boils at -25.6 C.
24
Q
What are the four basic components of a refrigeration unit?
A
Compressor, Evaporator, Condenser, Thermal Expansion Valve.
25
What is the state of the refrigerant at the following points?
A) Between the evaporator and compressor.
B) Between the compressor and condenser.
C) Between the TEV and evaporator.
D) Between the Condenser and the TEV.
A) Gas at low pressure and superheated
B) Gas at high pressure and superheated.
C) Liquid at low pressure and cold.
D) Liquid at high pressure and subcooled
26
What does TEV stand for?
Thermal Expansion Valve
27
What is the role of the TEV?
Slows the rate of the refigerant, lowering the pressure and temperature of the refrigerant present in the evaporator.
The TEV controls the refrigerant flow to make sure that all refrigerant is 'flashed off', reducing the risk of liquid making back to the compressor.
28
How does a TEV regulate the flow of refrigerant correctly?
It uses a Phial (Bulb) which is linked to the diaphragm of the TEV. This bulb is filled with the same refigerant. At the area around the condensor increases, the refrigerant in the bulb expands pressing against the TEV diaphragm. This allows more refigerant in the exaporator. Which in turn cools down the bulb which reduces the pressure of the bulb refrigerant against the TEV.
29
What component of the refrigeration is being descibed?
"Extremely cold liquid refrigerant enters, it then evaporates into a gas and exits the component."
Evaporator
30
Where is the evaporator situated?
In the area/room that you want to create cold air.
31
If a plant trips on a low pressure trip, what is wrong?
Not enough refrigerant
32
If the HP trip operates what is wrong ?
over charged with gas or there is a shut valve.
33
What does the suction valve do?
Isolâtes the suction side the compressor
34
What does the discharge valve do?
It isolâtes the discharge side of the compressor.
35
What is the role of the oil separator?
Removes the lubricating oil that is carried over in the refrigerant.
36
What is the role of the liquid receiver?
Acts as a reservoir for refrigerant.
And
Provides a liquid deal between the condenser and the thermal expansion valve.
37
Explain the liquid line stop valve.
By shutting this valve you prevent refrigerant leaving the liquid receiver.
This will stop the system due to the LP trip activating. At this point all refrigerant is in the liquid receiver.
38
What does the drier do?
Removes moisture.
39
What are the sight glass indication colours and their meaning?
Green = dry
Yellow = Moisture present
40
Explain charging connections and the colours and where they should be connected?
LP is blue and HP side is red. Either side of the compressor.
41
What are the 3 types of defrosting, and how are they done?
Natural Defrosting - switch off the refrigeration system open the door and allow the ambient atmostphere to melt the ice. Done every 3 - 6 months).
Hot Gas Defrosting - Pushing hot gas through the evaporator to defrost the coils. This is performed for one hour per day (4 x 15mins), this is done to protect the compressor oil and not heat up the room.
Electrical Heating coils - rod type or coils wrapped around the evaporator. Carried out for a maximum of 1 hour to prevent any oil in the evaporator from burning.
42
Explain the Montreal protocol 1987.
Various states willl phase our harmful CFC gases. All refrigerants must be recovered for processing, nothing is to be knowingly released into the atmosphere. 1967.
43
List three ozone depleting substances.
CFC's
HCFC's
Halons
44
Explain the Kyoto Summit of 1997
Nation states came together and agreed to reduce their greenhouse gas (CO2, CFC's, HCFC's) emissions.
45
Why is leak detection important?
It maintain good engineering standards and efficient running of refrigeration plants, preventing the ingress of air (Moisture). Additionally, the UK has to keep up with the montreal protocol.
46
Name the 5 leak detection techinques and how they are used?
Infra Red Leak Detection System (IRLDS) Sensor fitted at various points around the machinery and pipework.
Oil Slick - If there is oil leaking there is gas leaking too.
Spectrolyn Dye and UV light - Put dye into the system and use the light to check for the leak.
Snoop - Soapy water that will bubble where ever there is a leak.
Halogen Leak Detector - A Hand held sniffing device that detects leaks. It is sensitive. Not reliable.
47
Name the 3 oils used in Refrigeration for the RN and where they are used.
OM 70 - General purpose, used in CFC/HCFC.
SUNISO 3GS - Synthetic oil T23 and T boats.
SW 68 - Synthetic oil used with R134a gas.
48
What is the general rule when putting new oil into refrigeration compressor?
Use the right amount of for the job. Oil cannisters sizes range from 500ml to 5 ltr.
49
Define Hygroscopic.
Ability to readily absorb moisture.
50
What three methods are used to add oil to the sump?
Sump filler plug
Hand pump
Dosing pot
51
What systems are cooled by the chilled water plant?
Weapons systems
Radars
Ships computer system
Air treatment units (ATU's)
52
What temperature does the chilled water plant operate at?
4 - 6 degrees celcius.
53
describe how a chilled water plant operates.
It is the same as a normal refrigeration system, but, with a chilled water heat exchanger in place of a evaporator. With the chilled water closed system supplying cold water for cooling to the various systems onboard the vessel.
54
What makes refrigerant vapour dangerous?
It is odourless, non-toxic, non-flammable and non-explosive. However, it does not support life and will kill you by replacing the oxygen available in the atmosphere.
It is heavier than air.
55
If there is a refrigerant leak, what are the dangers associated...
CFC's exposed to high heat source will produce Phospgene gas (Mustard Gas).
56
What gas fills a fruit and vegetable store?
CO2
57
What precautions should be put in place when working in a refrigeration machinery room?
Inform someone
BA is available
Fans are running
No smoking at any time
Infra Red Leak Detection System is working and indicating SAFE.
Warning (Distress) lamp is working
Sentry who remains outside
Door mechanism for exit is operating.
58
What are the four basic combinations of ventilation onboard a ship, and where are they used?
Fan supply and fan exhaust
- Machinery space, WC's, Bathroom, laundry
Fan supply and natural exhaust
- Store room and workshops
Natural Supply and fan exhaust
- Pain stores, spirit rooms, inflam stores.
Natural Supply and natural exhaust
- Minor unoccupied compartments and lobbies.
59
Name the six filters used onboard RN ships.
Panel Filters
Supply Filters
Grease Filters
Lint Filters
Dust Filters
Flameproof Gauzes.
60
Where are each of the following filters used in the RN ships?
Panel Filters
Supply Filters
Grease Filters
Lint Filters
Dust Filters
Flameproof Gauzes.
Panel Filters
- fitted to air conditioning
Supply Filters
- ATU's Between plenum chamber and cooler
Grease Filters
- on exhaust canopies over deep fat fryers
Lint Filters
- on the ehaust trunking of the laundry
Dust Filters
- on the sonar and computer system spaces
Flameproof Gauzes.
- on inflam stores, paint stores, hangers, vehibles decks and magazines.
61
What do each of the following marking denote for finding a compartment on a ship?
3L7
3 is the deck
L - denotes which section of the ship it is in.
7 is starboard side because the number is odd.
62
Name the 5 areas onboard a ship that have special requirements.
Galley
Store Rooms
Auxillary Machinery Spaces
Sewage treatment plants
Magazines.
63
What does the STP compartment require?
15 air changes per hour.
64
What happens in a magazines store when in Alpha State?
The fresh treated air is put into full re-circulation.
65
Whaht are the precentages of recirc air and fresh air in a ATU?
67% Recirc air and 33% fresh air.
66
What are the three sections (filters) in a ATU? (What does each one do.)
Pre-particulate filter
-Paper filter removes coarse particles
Particulate filter
- Made of Glass fibre, removes bacteria
Gas Filter
- removal of all chemical warfare agents.
67
When are citadel tests carried out?
Annually
Prior to DED (Docking Extended Duration)
During HATS (Harbour Acceptance Trials)
During SATS (Sea Acceptance Trials)
During a FOST workup.
68
How is a citadel test done?
Close all openings
Open AFU inlets and start AFU
Restrict access to and from the CItadel (Airlocks must be used.).
Search for leaks and carry out repairs. Vacuum of 2" WG is required.
Record the Results of the test in the SEF and D171.
69
What is the role of an air bleed and valve and what are its parameters for effective operation?
Maintains the citadel pressure at the required amount above atmospheric pressure.
The valve is set to lift when a compartment pressure exceeds 0.5" WG.
70
What temperature is the air that is pumped into the machinery space?
15 degrees celcius below ambient.
71
What is the Crash Stop ventilation, when is it used and where is it operated from?
It is the button that allows for the immediate stoppage of all ventilation on board a ship.
It is used in the event of a fire or crash on a deck.
it is situated in SCC and HQ1.
72
Define a fluid
Substance that takes the shape of its container
Capable of transmitting power
Can be a liquid or a gas.
73
Differences between a liquid and a gas
Gas is compressible
Liquid incompressible
Liquids used in hydraulic system
Gas used in pneumatic system
74
What is Pascals principle regarding hydraulics and explain a practical application?
Pressure in a closed container is the same at all points.
In practice this would see small cylinder receiving a force, but the larger cylinder has more surface area so the force exerted on this cylinder is multiplied and greater than the small cylinder.
75
What is the equation used for calculating hydraulics
F = AxP
76
What is a common problem in hydraulic systems?
If there is an indication of pressure it does not mean there is "flow". Flow is the actual displacement of liquid and the force is actually causing movement.
77
What are the advantages of Hydraulics?
Reliable
Infinite speed range
Simiple and easy to understand
Easily Reversible
No spark risk
Ability to withstand overload
High Torque at low speeds
Size is 1/12 of equivalent electric motor.
78
What are the disadvantages of hydraulics?
Fire risk
Less efficient
Risk of contamination
Noise
79
What is denso 'tape' used for?
Where is it stored?
Where is it found?
Used to prevent corrosion
It is stored in the Flammable store.
It is found on the underdeck or where two dissimilar metals are coming into contact with each other.
80
At what temperature does O-rings melt at and what gas if produced and what are the dangers associated with it?
above 300 degrees celcius.
HF gas released.
If inhaled serious damage possibly death.
In moist environments it can create HF acid = burns.
81
What PPE must be worn when working with Fluorocarbon elastomers?
PVC gauntlets
Rubber boots
PVC coveralls
Full-face visor.
82
What is the HDS information for hydraulic fluid?
Skin irritation
Change oil soaked clothes immediately.
Irritation/inflammation = see doctor
Always consult the HDS
Poses a fire risk, all leaks should be cleaned immdiately.
Flexi hoses are to be in date for test.
Gauge glass valves to be shut except when in use.
Suitable precautions taken before welding. or burning in the vicinity.
83
Where is hydraulic’s used?
Steering
Anchor windlass
Weapon system
hydraulic lifts
CPP
84
Name two types of hydraulic fluid and the propertires thereof.
Petroleum based - Cheap mineral oil. General purpose.
Synthetic based - Man made for specific purpose, contains additives to prevent undesirable properties (Loss of viscocity at high temp.) it is expensive.
85
Name the 3 Hydraulic oils their colour and uses?
OX30 Red - submarines
OM33 Orange - General purpose, Carriers.
OX40 Green - Synthetic oil used on T23 and T 45.
86
What is the function of Rust Veto?
Used during upkeep periods where hydraulic oil has been removed from a system, substitute to prevent corrosion in Hydraulic system.
87
Name the 3 requirements of a hydraulic fluid
Transmission of power
Must flow easily
Must be as incompressible as possible.
88
What extra requirement must hydraulic fluid fulfill?
Lubrication, where it must create a full filim lubrication on the parts reducing wear and tear.
89
Why don't hydraulic systems have a o-rings?
viscocity of the oil and low clearances of moving parts means there is no leakage or minimal leakage.
90
What are the 2 methods by which a hydraulic system is cooled?
Seawater heat exchanger.
Circulation of the fluid into a header tank, where the walls of the tank give up heat.
91
What are the requirements of a good hydraulic fluid?
Incompressible - tranmitting of power.
Good lubrication properties
Good sealing properties
Gives up heat Readily
92
Name 5 Hydraulic oil additives.
Anti foam
Anti oxidants
Anti corrision
Demulsibility
Pour point depressant.
93
What are the common causes of contamination of Hydraulic system?
Airborne particles and moisture
Construction dirt
Dirt in new fluid
Dirt produced by wearing in a new system
Dirt from human sources.
94
How do you reduce the contamination of a hydraulic system?
Filtration and filter maintenance.
Operation of filter cloggin indicator
Caps on open ended pipes
Clean working area
Good design
Good working practices
Guardian Filter pack.
95
What are the two types of hydraulic systems?
Ring main
Stand alone power packs.
96
Name each type of pump and how it works in HS's
External Gear type pump - Gears with intermeshing teeth.
Internal Gear type pump - The pump is an improvement on EGTP.
Vane Pump - A spinning roter with extendable arms create a pressure gradients.
Lobe Pump - Intermeshing lobes that draw fluid around the outside of the compartment.
Piston Pump (single) - Just a normal piston.
Piston Pump (Multiple) - Radial pistons and an off center disc that rotates pressuring each cylinder.
97
What is the advantage of the multi cylinder pump over a single.
Highly efficient
Wide range of capacities
Variable output
Large HP applications.
98
What is the purpose of the drain on a HS?
The drain leg allows the oil that has been specifically used for cooling and sealing the actuator/ motor to return to the tank.
99
What is an accumulator?
A device in which potential energy is held and smooth out pulsations.
100
What are the 3 types of accumulators?
Piston
Bag
Bladder
101
Explain a Axial Piston Pump (Fixed capacity)
A wedge shaped swash plate at the base of a series of cylinders. See notes for more.
102
Expalin an Axial Piston Pump (Variable capacity, bi-direction flow)
The swash plate can be moved to different angles to vary the flow of fluid, it can also reverse the flow direction of the fluid, but moving the swash plate passed vertical.
103
What does the Axial Piston Pump (variable capacity and bi-directional flow) used for?
Stabiliser system
CPP systems
Steering systems.
104
What does an actuator do?
Converts hydraulic energy into mechanical movement.
105
Define osmosis
The movement of water from high concentration to low concentration through a semi-permeable membrane.
106
Define Reverse osmosis
Using the principles of osmostic pressure. A concentrated salt solution is pressurised to overcome the osmostic pressure, thereby allowing fresh water to leave the salt solution (extracting the water) and increasing the concetration of salts in the brine.
107
How much Total dissolved solids are there in sea water?
34 000 ppm
108
How much is the TDS in made water after the desalination process
250 - 300 ppm
109
What is the RN term for Desalinated water and waste water.
Desalinated water is "Permeate" or "made water"
Waste water is "Brine"
110
What is the max operating pressure of deselatination plant?
65bar
111
What is the first filter and pore size in the desalination plant?
Bag filter with a pore size of 60 microns.
112
What is bank cartridge filter port size?
10 Microns
113
How does the concentration control valve assist in the reverse osmosis system.
It helps by increasing the pressure of the system, through creating back pressure by controlling the flow.
114
After passing through the Desal Plant what are the properties of the 'Made water'?
350 ppm TDS
115
Using double filtration, what is the properties of the "clean water" ?
3.5ppm
116
What is the % volume of water lost as brine and what are the properties thereof?
85% of the volume of liquid is pumped out and the TDS is 56 000 ppm.
117
What is the antiscaling process for the water entering the reverse osmosis stack?
"Hypersperse" is released into the water via a dosage system. Usually 5ppm.
118
What is the concentration of Chlorine in the freshwater system?
0.2ppm
119
When should desalination not take place?
When the water source is contaminated, such as a harbour or estuary.
120
What services are supplied by the "Fresh water"?
Laundry
Galley
Showers/ sinks
Water heaters
Medical use
Bridge window washers
fresh water hose reels
Machinery cooling
Gas turbine washing.
121
What three tests are carried out on fresh water that is collected from a third party alongside in port?
Visual Test
ChEMets Test
Taste test
122
How do you remove a water hammer from a hot water system?
Air eliminator is fitted.
123
Name the prodcedures for when getting water from a fresh water source alongside in port.
Draw fresh water hoses and connection from the store.
Unscrew the deck cap to the filling connection
Fit the filling gooseneck to the filling connection/ Pressure Relief Valve
Connect hoses to the shore water supply.
Ope the shore filling supply valve and flush through the hoses.
Carry out water tests - only continue to next stage if tests ok.
