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Theory 4 > Refrigeration > Flashcards

Refrigeration Flashcards

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1
Q

Name the four components of a basic Refrigeration system and what is their purpose?

A

-Compressor: pumps refrigerant around the system

-Condenser: uses sea water to cool the refrigerant changing its state from gas into a liquid

-Thermal Expansion Valve: controls the refrigerant flowing through the system. Increasing or decreasing depending on the temperature in the evaporator

-Evaporator: the refrigerant flowing through the evaporator removes heat from the refrigerator. This act changes the state of the refrigerant from a liquid to a gas

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2
Q

Describe the state of refrigerant between:
Compressor to condenser
Condenser to thermal expansion valve
Thermal expansion valve to evaporator
Evaporator to compressor

A

C-C: hot, HP, gas
C-T: Warm, HP, liquid
T-E: Very cold, LP, liquid
E-C: Cool, LP, gas

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3
Q

Defrosting methods

A

Natural (3-6months)
Hot gas defrosting- max 1hour in 24 hours in 15min slots
Electrical heating coils- max 1hour in24hours

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4
Q

Lubrication oils for the compressor

A

-OM70
-SW68
-SUNISO

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5
Q

Three methods for adding oil to compressor

A

-Sump filler pump
-hand pump
-through a dosing pot

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6
Q

What are the ozone depleting gases

A

-CFCs
-HCFC
-Halons

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7
Q

Greenhouse gases

A

CO2
HFC
PFC

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8
Q

Methods of leak detection

A

-Oil slicks
-infrared leak detection system
-spectrolyne
-snoop
-halogen leak detection

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9
Q

Three methods of heat transfer

A

-Conduction
-Convection
-Radiation

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10
Q

Procedure for entering Refrigeration compartments

A

-The Rating in charge of the watch is to be informed that personnel are entering the compartment, and informed when the compartment is vacated

-Breathing Apparatus is available at the machinery space access

-• The Infra-Red Leak Defections System (IRLDS) is working correctly and indicating safe

• The personnel trapped warning lamps are in working order
• Any rating entering the room is to be accompanied by another rating who remains outside the room as a safety number
-the internal door opening mechanism is in correct working order

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11
Q

What is chilled water used for

A

Weapon systems
Radars
Ship’s computer systems
Air treatment Units

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12
Q

What is ventilation used for

A

-Cooling of electrical equipment
-CBRN
-Habitability
-main machinery space cooling
-galley ventilation

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13
Q

When are citadel tests carried out

A

-Annually
-prior to docking for extended duration
-Harbour acceptance trials
-sea acceptance trials
-FOST work up(war games)

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14
Q

What is a cash stop

A

A crash stop facility is built into the ventilation system to allow all fans to be stopped in case of an emergency, e.g. FIRE or CRASH ON DECK. In hq1 or sc

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15
Q

Before vents are restarted what should be checked for…

A

Clear of smoke, welding fumes and debris

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16
Q

Advantages of hydraulics (8)

A

It’s reliable
Simple and easy to understand
Infinite speed range
Easily reversed
Ability to withstand overload
No spark risks
High torque at low speeds
1/12 the size of an electric motor

17
Q

Disadvantages of hydraulics (4)

A

Fire risk with mineral oil systems
Noise
Risk of contamination
Less efficient (85-95%)

18
Q

What are the hydraulic o-rings made of, what temperature do they retain their elastic properties and what happens if they burn

A

Fluorocarbon elastomers, 300*c, give off hydrogen fluoride

19
Q

Common causes of of contamination in hydraulic oil are:

A

• Airborne particles and moisture
• Construction dirt
• Dirt in new fluid
• Dirt produced by wearing in new system .
Dirt from human sources

20
Q

Methods of reducing contamination are:

A

• Good system design
• Filtration and filter maintenance
• Operation of filter and clogging indicators
• Good working practices
• Use of Guardian filter pack
• Caps should be fitted to open pipework
• Clean working area

21
Q

Pumps used for hydraulic systems

A

Internal gearwheel type
External gearwheel type
Vane type
Lobe type
Radial piston type
Axial Piston Pump (These types of pump use a Swash Plate)

22
Q

What are Axial piston pumps used for

A

Stabilisers
CPP systems
Steering systems

23
Q

Actuator types

A

Linear (single or double acting)
Rotary

24
Q

What are accumulators used for

A

Store energy and to smooth out pulsations

25
Q

What is fresh water used for

A

Drinking
• Washing
• Cooking
• Cleaning

26
Q

What services are provided by fresh water systems

A

Theory 4 (1 decks)

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