Refrigeration

Question 1

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

Answer 1

-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

Question 2

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

Answer 2

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

Question 3

Defrosting methods

Answer 3

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

Question 4

Lubrication oils for the compressor

Answer 4

-OM70
-SW68
-SUNISO

Question 5

Three methods for adding oil to compressor

Answer 5

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

Question 6

What are the ozone depleting gases

Answer 6

-CFCs
-HCFC
-Halons

Question 7

Greenhouse gases

Answer 7

CO2
HFC
PFC

Question 8

Methods of leak detection

Answer 8

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

Question 9

Three methods of heat transfer

Answer 9

-Conduction
-Convection
-Radiation

Question 10

Procedure for entering Refrigeration compartments

Answer 10

-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

Question 11

What is chilled water used for

Answer 11

Weapon systems
Radars
Ship’s computer systems
Air treatment Units

Question 12

What is ventilation used for

Answer 12

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

Question 13

When are citadel tests carried out

Answer 13

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

Question 14

What is a cash stop

Answer 14

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

Question 15

Before vents are restarted what should be checked for…

Answer 15

Clear of smoke, welding fumes and debris

Question 16

Advantages of hydraulics (8)

Answer 16

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

Question 17

Disadvantages of hydraulics (4)

Answer 17

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

Question 18

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

Answer 18

Fluorocarbon elastomers, 300*c, give off hydrogen fluoride

Question 19

Common causes of of contamination in hydraulic oil are:

Answer 19

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

Question 20

Methods of reducing contamination are:

Answer 20

• 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

Question 21

Pumps used for hydraulic systems

Answer 21

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

Question 22

What are Axial piston pumps used for

Answer 22

Stabilisers
CPP systems
Steering systems

Question 23

Actuator types

Answer 23

Linear (single or double acting)
Rotary

Question 24

What are accumulators used for

Answer 24

Store energy and to smooth out pulsations

Question 25

What is fresh water used for

Answer 25

Drinking
• Washing
• Cooking
• Cleaning

Question 26

What services are provided by fresh water systems