3. • Reefer ships are designed to carry perishable goods at
temperatures between -27 and +13 degree Celsius.
• Types of Reefer cargo ships
• There are three main types of reefer ships based on the types for
shipment of perishable goods.
• Reefer Cargo Ships
1. Ships carrying reefer cargoes in bulk.
2. Ships carrying palletized goods in all cargo spaces.
3. Freezer ships carrying fish and other frozen goods.
• Freezers ships are specially built to carry frozen cargoes.
• Reefer Containerships, are exclusively intended to carry
refrigerated containers in holds and on decks.
4. Secondary refrigerants
• These are used where plants are huge &
complex, to avoid circulation of expensive
gases in large quantities.
• Brine or chilled water is used for reefer
chambers.
• Ventilation Fans used for Air circulation
inside cargro area
5. Brine System.
• Brine system and air circulation.
• In this system, brine as secondary refrigerant is circulated through
the coolers in cargo holds.
• Air is cooled in a brine cooling system and cold air ducted to the
cargo spaces.
• Brine is relatively easy to regulate.
• Brine is inexpensive, being made with calcium chloride and fresh
water.
• Sodium dichromate or lime may be added to maintain the brine in an
alkaline condition.
7. Brine system in Reefer Ship.
• Primary refrigerant
vapourises in the
evaporator coil causing
brine to cool.
• Brine gets cooled to
about -15 Deg C and
being circulated in the
reefer chambers to cool
the Holds.
• By control the flow rate of
the brine, the temperature
can be controlled.
• Brine:
• Calcium chloride ¼ kg
mixed in 1 litre of fresh
water.
• If Concentration of calcium
chloride in brine is
increased; the freezing
point of brine will decrease.
• Inhibitors to prevent
corrosion also added to the
brine.
• Common salt may be used,
• but not the sea water (SW
is highly corrosive)
8. • Freezing point (deg c)
• -3
• -7
• -13
• -21
• -32
• -46
• Density at 15’c kg/m3
• 1050
• 1100
• 1150
• 1200
• 1250
• 1290
BRINE
9. • Secondary refrigerants are usually liquids, and are used to transfer
heat from the substance being cooled to a heat exchanger where
the heat is absorbed by a primary refrigerant.
• (In an air conditioning system it could be said that air is acting as a
secondary refrigerant).
• These fluids are cooled by a primary refrigerant then exposed to the
cargo, thus absorbing its heat, and the warmer fluid returned to the
chiller, rejecting the heat to the primary refrigerant circuit.
• High temperature applications such as air conditioning use chilled
water as the secondary refrigerant.
• Low temperature applications use brines, glycols and oils as
secondary refrigerant.
• Large refrigeration plants often use secondary refrigerants to
transport the cooling capacity from the plant room to the point of
use.
10. • Benefits available from the use of secondary refrigerants:-
• The amount of primary refrigerant used can be minimised.
• Primary Refrigerant remains in the plant room under supervision.
• Pressure losses in the vapour compression cycle are minimised so
increasing cycle efficiency.
• The mass of secondary refrigerant provides a continuous operation, hence
no intermittent surging of thermal loads.
• Less Supervisory Staff needed as Refrigeration Plant can be switched
on/off (automatically).
• Breakdowns can be repaired in the primary system while secondary cooling
capability still maintained.
11. The basic diagram with one chamber circulated with brine from one evaporator,
in a closed circuit with a header tank to allow for expansion and contraction of the
brine
BRINE Cooler
BRINE Pump
Basic Diagram
Brine cooled by Primary Refrigerant.
Secondary Loop, Using Brine.
12. • The evaporators (brine coolers), pumps, and distribution valves in Reefer
cargo ships are usually located together within an insulated brine room.
• The system is basically very simple, the complexity arises from duplication
of components and alternative cross connections.
• The following diagram illustrates the development of a brine system.
BRINE Cooler
13. The addition of headers which enable a number of spaces to
be served.
BRINE
Brine Pump
Multiple Spaces cooling
15. Air circulation systems
• The design of an air circulating system is dictated principally by the allowable
temperature spread in the cargo spaces and is not influenced by the type of air
cooler in use.
• Brine and direct expansion systems have similar air circuits.
• The air cooler and fan unit are mounted behind a trunking at one side of the
chamber with air being delivered and returned via trunking, false decks or
deckheads provided with suitable openings.
• The delivery openings are arranged with the largest furthest away from the fan
where the air pressure is at its lowest and the smallest nearest to the fan.
• Correct cargo stowage is important as voids in the stow could allow the air to
short circuit to the suction side of the cooler.
• Cargo stowed adjacent to air inlets can become desiccated (dried out).
• For this reason and also to remove hot spots in the cargo, air circulation
should be reversible.
• With ripening (live) cargoes, CO2 tends to accumulate in cargo spaces and it
is necessary to limit the level by freshening the circulating air.
• Vents must be provided for this purpose.
16. Air circulation and refreshing
• Between 90 and 120 air changes of the net volume per hour is
usually provided in holds.
• Such volume flow guarantees good and uniform cooling rate of
palletized and bulk cargo and allows for imperfect storage.
• This air rate will be reduced on completion of cooling down and
when frozen cargo is carried.
• Air refreshing rates to remove carbon dioxide, ethylene and other
volatiles, can be two or three air changes per hour.
18. • Four Holds or more.
• Each cargo hold with 4 or 5 cargo
decks.
• Each with enough clear head of
2.2M.
• size of Pallets (1.2M long x 1.oM
wide x 2.1M high max).
• These decks are arranged
usually in eight air tight
temperature zones, with the air
coolers placed along the bulk-
heads serving one or sometimes
two decks.
• Variable speed fans are placed
above the coolers forcing air
through the cargo and back to
the coolers.
19. Refrigeration systems on board for Cargo Holds
• Refrigeration system is by using secondary cooling by chilled Brine.
• Brine is made by dissolving calcium chloride in fresh water will have
a freezing point well below the desired temperatures of the
refrigerated compartments.
• Cold brine is pumped at controlled rates to give the correct working
temperature.
• The brine absorbs heat from the compartments and returns to the
evaporator where it is again cooled and recirculated.
• The brine is then led into grid boxes and air drawn from the bottom
of the compartments by fans is blown over the brine grids into the
compartments via trunking arranged along the ceiling.
20. • Reefer must be able to maintain temperature
from – 30 deg C to 13 deg C.
• Holds are designed to carry palletised cargo.
• Air coolers are placed inside for circulation.
• Air forced through under the grating, then
vertically from bottom to top through the cargo
and back to coolers.
• The square shape of holds prevents pallets from
falling at sea and improves circulation.
• Decks are strengthened for forklift trucks to work
inside the holds.
21. • For uniform cooling, between 90 to 120 air
changes of the net volume per hour is usually
provided in holds.
• The rate of air circulation will be reduced on
completion of cooling down of cargo.
• Air refreshing rates to remove carbon- dioxide,
ethylene and other volatile gases will be two or
three changes.
22.
23.
24. Working principle
• Liquid refrigerant at the evaporator coil will pick
up heat from the room (cargo) and vapourise.
• Vapour pressure at the compressor suction will
increase (2.8 bar).
• Suction pressure high switch will actuate the
motor starter and motor will cut in.
• The compressor will thus run, drawing gas from
the evaporator coil and pumping refrigerant back
to the evaporator coil through the condenser and
throttle valve.
25. • The plant will continue run like this, cooling the
cargo till the set temperature (-12c), at which
point the thermostat will cause the solenoid
valve, to shut off.
• Flow of refrigerant to the evaporator coil will
stop, suction pressure at the compressor inlet
will drop and compressor will cut off on ‘low
suction pressure’ (1.5 bar)
• Once the room temperature raises to -8c, the
solenoid valve will open, stored refrigerant from
the receiver will flow into evaporator coil and
vapourise, Compressor will cut in.
26. • For additional holds will have its own set of
solenoid valve, expansion valve,
evaporator coil and thermostat.
27. • Fruits, vegetables & flowers: are live
cargoes.
• They respire absorbing O2 and exhale
CO2.
• During this process energy is released and
volatile gases given off.
• Higher rate of air circulation is required.
• CO2 concentration to be maintained with
in acceptable limits.
28. • Types of chilled cargo
• Fresh fruits and vegetables
• Fresh meats, poultry and seafood
• Dairy products and eggs
• Fresh juices
• Confectionery products
• Bulbs, live plants and cut flowers
29. • ‘Chilled’ Cargo has a short shelf-life.
• It must be transported from source to destination with
maximum care or its value will diminish.
• This means shipping sensitive products in a highly
controlled environment at the perfect temperature.
• Reefer containers automatically manage temperatures
within a 0.5°C (0.9°F) range, ensuring optimum condition
on delivery.
30. Factors affecting Live Cargo
• Exposure to high temperatures can:
• Accelerate water loss
• Produce Ethylene
• Produce disease-forming organisms
• Affect the physiological state of the product
• Cause uneven ripening, surface scalding and decay
• Exposure to low temperatures can cause:
• Chilling or freezing injury
• Surface pitting and watery areas
• Discoloration
31. • Types of frozen cargo
• Frozen meats, poultry and seafood
• Frozen prepared foods
• Frozen concentrates.
Key factors that affect the shipment of frozen cargo
32. Meat & Fish
• To maintain: -
• Flavour,
• Texture
• Aroma, and
• Prevent Disease,
• many meat and seafood products are best shipped at
temperatures of -20°C (-4°F) or lower.
33. • Refrigerated transport for
all perishable cargo,
under controlled
temperature, controlled
atmosphere(O2 & CO2)
and humidity.
• The object of refrigeration
is to prolong the life of
perishables by lowering
the temperature so that
metabolic deterioration
and decay caused by
micro organism are
retarded.
• Animal products do not
generate any gases or
heat during sea voyage
and are referred as
‘Dead’ cargo.
• Frozen meat:
microbiological activity
above -8 deg C.
36. Methods of insulation
• As the steel hull structure is an excellent conductor of heat, some
form of insulation must be provided at the boundaries of the
refrigerated compartments if the desired temperatures are to be
maintained economically.
• Cork, glass fibre, and various foam plastics in sheet or granulated
form may be used for insulating purposes.
• Glass fibre is often used in modern ships as it has a number of
advantages over the other materials; for example, it is extremely
light, vermin-proof, and fire-resistant, and it will not absorb moisture.
• On the decks and particularly at the tank top the insulation must
often be load-bearing material, and cork might be preferred, but
fibreglass can be supported by tongue and grooved board linings
and wood bearers.
37. Drainage
• A particular problem in insulated
spaces is drainage, as ordinary
scuppers would nullify the
effects of the insulation.
• To overcome this problem brine
traps are provided in drains
from the tween deck chambers
and insulated holds.
• The brine in the trap forms an
effective seal against ingress of
warm air, and
• It will not freeze, preventing the
drain from removing water from
the compartment .
38. • The thickness of the insulation depends on the type of material used
and the temperature to be maintained in the compartment.
• However the depth of stiffening members often determines the final
depth.
• Insulating material is retained at the sides by galvanized sheet steel
or aluminium alloy sheet screwed to wood grounds on the frames or
other stiffening members .
• Insulation on the boundaries of oil tanks, e.g. on the tank top above
an oil fuel double bottom tank, has an air space of at least 50mm
between the insulation and steel.
• Suitable insulated doors are provided to cold rooms in general cargo
ships, and
• in refrigerated cargo ships, the hold and tween hatches may be
insulated.
• Patent steel covers or pontoon covers may be filled with a suitable
insulating material to prevent heat losses.
39.
40. Load port survey.
• Prior to loading condition of chambers to
inspected.
• Must be clean and free from odor and
fitted with thermometers in working order.
• Refrigeration machinery seen in operating
condition.
• The temperatures of each chamber is
noted and entered in the certificate.
41. Insulation.
• Ship sides & Bulkheads insulated with
Rock wool.
• Tank tops & decks with polyurethane
slabs.
42.
43. Details of ship side & deck insulation
• Polyurethane is
injected between
shipside and plywood
lining.
• Mineral wool are fitted
between the frames.
46. • Temperature Control - Prevention of Damage by Micro-organisms
• Almost all organic matter is constantly under attack by micro-
organisms such as yeasts, moulds or bacteria which, like all living
things, require adequate moisture and an appropriate temperature to
enable them to grow.
• In general, the higher the temperature, the faster the rate of growth.
For example, the rate of growth of almost all micro-organisms
doubles for every 10°C increase in temperature.
• Equally, the rate of growth halves for each 10°C reduction in
temperature. However, there are upper and lower limits to this
effect.
• For most micro-organisms, the rate of growth at temperatures below
zero is very small while most will not grow at temperatures above
about 45°C.
• Thus, carrying an organic cargo at a lower temperature will tend to
slow down the rate at which it can be damaged by micro-organisms
because they grow at a much slower rate
47. • Cold treatment
• The purpose of Cold Treatment is to kill insects and
larvae by maintaining a sufficiently low temperature for a
pre-determined period of time.
• Applying Cold Treatment eliminates the need to fumigate
cargo using insecticides, such as methyl bromide, which
is illegal in many countries.
• Cold Treatment is primarily applied to various types of
citrus fruits, such as oranges, grapefruit.
• However, kiwi fruit, apples, pears, grapes, lychees,
loquats, etc. can also be carried under Cold Treatment.
48. Cold Treatment
• Why and how.
• CT is used to protect the receiving country from insects such as the
‘Mediterranean Fruit Fly’, (The most common species).
• It is done by lowering the fruit pulp temperature to below 36°F (2,2°C)
and maintaining the temperature there for a longer period. This will
kill all living flies, eggs and possible larvae in or on the fruit.
49. Factors affecting Reefer Cargo.
• Fruits & Vegetables: -
• Respiration
• Fruits and vegetables continue to live and breathe after
harvest, consuming
• oxygen, generating heat and giving off gases such as
carbon dioxide and moisture.
• This respiration process utilizes resources and causes
changes that influence the Commodity’s value, flavour,
quality, colour, texture and water content.
50. • The quality of frozen fishery products:
• Loss of quality before freezing. ...
• Loss of quality during frozen storage. ...
• Physical damage to frozen products. ...
• Pre-shipment inspection. ...
• Nature of the consignment. ...
• Temperature of the consignment. ...
• Condition of the Insulation material. ...
• Visual indications of spoilage in individually frozen fish.
• To maintain flavour, texture and aroma, and prevent disease, many
meat and seafood products are best shipped at temperatures of
-20°C or lower.
51. • Important factors to consider when transporting frozen products are:
• The cargo must be pre-frozen to the correct temperature.
• Maximum load height should never exceed the red load line of the
container.
• Ventilation of the container must always remain closed and humidity
off.
• Packaging must be able to resist moisture and allow for a vertical
flow through boxes to maintain the desired temperature.
60. • Individual Insulated box containers with
their own refrigeration plant are connected
to 440 V A.C sockets provided on deck.
• 20 ft or 40 ft containers are generally in
use.
• Containers are insulated with rigid
polyurethane with metallic lining.
• Insulation thickness is generally 100mm.
61. • Floor is with T-sections for air circulation.
• Air is admitted along one side of the
container with extraction from the opposite
side.
• The overall weight of the container is limited
to 20 tonnes.
• The container will have an independent
refrigeration unit of capacity to maintain -25
to + 20 deg C.
62. • A reefer container is an enclosed unit used for
transporting temperature sensitive cargo.
• The container requires an external power supply for its
operation.
• When reefer containers are loaded in ships, the power
supply is provided from the power generated from the
D.G sets of the vessel.
63. Types of Refrigerated Shipping Containers are:
• 1. Closed Reefer:
• This is a conventional type refrigerated container.
• It comes in one-piece with integral front wall and an all-
electric automatic cooling and heating unit.
• 2. Modified/ Controlled Atmosphere (MA/CA) reefer
containers:
• These type of insulated shipping containers maintain a
constant atmosphere by replacing consumed oxygen
using an air exchange system, for Live cargo.
64. • 3. Automatic Fresh Air Management Containers:
• AFAM reefer containers uses advanced technology to
regulate the air combination by automatically adjusting
the scale of fresh air exchange.
• It works similar to Controlled Atmosphere refrigerated
container, controlling the composition of oxygen, carbon
dioxide and others.
• AFAM refrigerated containers extend the shelf lives of
the cargo they carry.
65. • Some important points about container refrigeration are:
• Container Refrigeration unit is fitted in front of the
container and it serves as a container front wall.
• 380/460 volts A.C, 3 phase, 50-60 hertz power.
• Operating control power is provided by single phase
transformer which steps down the A.C supply power
source to 24 volts, 1 phase control power.
66. • Understanding the Basic Sections of Refer Unit
• 1. Compressor Section
• Consists of a compressor (with H.P switch) and power cable storage
compartment
• It also contain modulating and suction solenoid valve (for controlling
the quantity of gas flow).
• Safety fittings in the section are-
• moisture liquid indicator, pressure relief valve, filter drier etc.
• Safety of the system have following sensors-
• Compressor suction and discharge sensor,
• supply air temperature sensor,
• Supply temperature recorder sensor,
• Ambient temperature sensor.
67. • 2. Condenser Section
• The condenser section contains condenser fan and its
motor, an air cooled condenser coil and condenser
saturation sensor.
• For air cooled condenser air is normally pulled from
bottom and discharged horizontally through centre of the
unit.
• Some units consists of water cooled condenser
/receiver. This unit is expensive.
68. • 3. Evaporator Section
• This section contains temperature sensing bulb,
• return recorder bulb sensor and a
• thermostatic expansion valve (for flow of refrigerant and
maintenance of inside temperature).
• Assembly consist of evaporator coil and heater,
• drain pan and
• heater,
• defrost and
• heat transmission switches.
• The evaporator fan circulates air throughout the container by pulling
air in top of refrigeration unit and directing air through evaporator coil
where it’s either heated or cooled and is then discharged out at the
bottom of refrigeration unit into the container.
69. • 4. Fresh air Make up Vent
• Purpose of this vent is to provide ventilation for commodities that
requires fresh air circulation and must be closed when transporting
frozen foods.
• Air exchange depends upon static pressure differential which will
vary depending upon how container is loaded.
70. • Always wear safety gloves and glasses while working on any unit and also
when charging refrigerant.
• Keep hand, tools, and clothing clear from evaporator and condenser fan.
• No work should be performed on any unit until all circuit breaker and start-
stop switches are turned off and power supply disconnected.
• Do not bypass any electrical safety device.
• In case of electrical fire, open circuit switch and extinguish it with CO2
extinguisher.
• Officer and crew responsible for refrigerated shipping container must know
the hazard related to refrigerant gas such as – Phosgene gas hazard (due
to high temperature), Asphyxiation hazard in non-ventilated spaces etc.
• Safely handle the compressed gas bottles when charging refrigerant
71. • Most common Problem in refrigerated shipping containers – Gas
Leakage.
• The leakage of refrigerant is the most common problem faced by on-
board staff during the voyage. Following tests must be carried out to
detect leakages:
• 1. Soap water test: This is done on low-pressure line by spraying
soapy water on the troubled pipe or space. If the soapy water comes
in contact with leakage area, bubbles will form
• 2. Halide lamp test: This is used for all pressure lines
• 3. Electronic leak detector: It is a portable unit to carry out leak
detection. It should not be used in a noisy area.
76. The economizer is a type of subcooler where part of
the refrigerant, typically 10-20%, is evaporated at a
higher evaporation temperature than in the main
evaporator, while subcooling the remaining refrigerant
flow substantially.
77. • An economizer contributes two
benefits to the system:
• The efficiency of the system is
improved by the increased sub-
cooling from the economizer unit.
• The economizer port provides
efficient compressor cooling during
compression.
• These two factors increase the
capacity of the compressor by around
10% while offering a larger operation
envelope for the compressor.
• Operating a heat pump with a
compressor with a large envelope
results in higher seasonal COP
because the heat pump may operate
without auxiliary power, also at very
low ambient temperatures.
78. • The Dos and Don’ts of Reefer Containers
• To take full advantage of these benefits, it’s essential to make sure that the stowage of reefer
cargo is carried out correctly.
• This is especially important for cold-treatment cargoes as certain types of fruit can be rejected
at the destination country if not stored correctly due to the risk of pathogens still being
present.
• To avoid this, it’s important to follow some general ‘Dos and Donts’ of reefer containers:
• Do’s Don’ts
• Pack cargo tightly and make sure it
is stable to prevent shifting. Stow cargo above the red load line.
• Set the unit at the correct
temperature that the cargo requires. Stow cargo past the end of the T-floor.
• Check the dehumidification controls. Allow any restrictions to block the flow of air.
• Pre-cool the cargo if required. Pre-cool the container unless it’s in
• cold storage in an airlocked cold tunnel.
• Set the correct ventilation settings. Allow any gaps between the pallets and the
• door
79. • The Benefits of a Reefer Container
• Containers don’t need to be put into cold storage upon arrival at their destination as
they are self-contained refrigerated units.
• They are available in a variety of dimensions, which makes them suitable for road,
sea, and air transportation.
• They are durable and can remain operational in harsh environmental conditions.
• They can be transported by diversified carriers. This offers greater financial security
and a faster return on investment than specialised reefer ships.
• They can prevent products from ripening too quickly and ensure a longer shelf-life by
circulating cool air.
• Despite their many benefits, there are still certain challenges facing the reefer
container industry.
• Reefer containers are adapting to changing over to new refrigerants, thus by moving
towards more eco-friendly alternatives.
80. Preparation for Loading
• PREPARATION OF CARGO HOLD for Loading:
• THE COMPARTMENT MUST BE CLEAN, DRY AND FREE OF
ANY ODOUR OR DIRT,
• HOLD MUST BE DEODORISED WITH MILD AGENTS (LIME,
OZONE),
• BILGES TO BE CLEANED, DRY, DEODORISED AND SUCTIONS
CHECKED,
• THE INSULATION AND PERMANENT DUNNAGE TO BE
CHECKED AND REPAIRED AS NECESSARY,
• SCUPPERS TO BE CLEANED,
• BRINE TRAPS TO BE CHECKED, TESTED AND REFILLED,
• THERMOMETERS TO BE IN POSITION,
• BRINE PIPES TO BE TESTED TO ENSURE THEY ARE NOT
CHOCKED AND THAT NO LEAKS AT THE JOINTS.
81. • Dunnage is the name for
the materials used in
holds and containers.
• To protect goods and
their packaging from
moisture, contamination
and mechanical damage.
• Dunnage may include
plastic films, jute
coverings, tarpaulins,
wood (wooden dunnage),
rice matting, nonwovens.
82. • PRECOOLING OF THE COMPARTMENT:
• THE COMPARTMENT SHOULD BE COOLED DOWN
PRIOR TO LOADING TO A TEMPERATURE SLIGHTLY
LOWER THAN THE TRANSIT TEMPERATURE,
• DUNNAGE LAID IN THE COMPARTMENT SHOULD
ALSO BE COOLED DOWN OTHERWISE IT WILL
STAIN THE CARGO,
83. • PRECAUTIONS DURING LOADING:
• REEFER CARGO SHOULD BE LOADED ONBOARD ONLY UNDER THE
SUPERVISION OF A RECOGNIZED SURVEYOR,
• CARGO SHOULD NOT BE ALLOWED TO WAIT FOR LONG TIME ON THE QUAY,
• HOLD SHOULD BE PRE-COOLED TO TEMP BELOW THE CARRIAGE TEMP,
• DAMP, WET AND TORN PACKAGES SHOULD BE INSPECTED IF THE CARGO
HAS DETERIORATED. IF THE CARGO IS FINE THEN ONLY IT SHOULD BE
LOADED AFTER RE-PACKING,
• CONTENTS OF AT LEAST 5-10% CARTONS SHOULD BE EXAMINED FROM
EACH HOLD ON A RANDOM BASIS,
• CARTONS WITH SOFT OR DRIPPING CONTENTS SHOULD BE REJECTED,
• REFRIGERATION OF HOLDS SHOULD BE TURNED ON DURING LONG BREAKS
AND DURING MEAL BREAKS,
• ONCE LOADED, THE CARGO SHOULD BE COVERED WITH TARPAULIN,
• DURING OPERATIONS, THE FROST FORMED ON TOP OF THE BRIPE PIPES
SHOULD BE BRUSHED CAREFULLY. IT SHOULD NOT FALL ON TOP OF THE
CARGO.
• IN TROPICAL CLIMATES AVOID LOADING IN THE NOON. TRY TO LOAD CARGO
DURING NIGHT TIME,
• UPON COMPLETION OF LOADING, THE REEFER CHAMBER MUST BE CLOSED
AIR TIGHT AND COOLING RESUMED IMMEDIATELY
85. Cargo survey
• Refrigerated cargo ship.
• Used to transport perishable commodities which require
temperature-controlled transportation, such as fruit, meat, fish,
vegetables, dairy products and other foods,
• Refrigerated Cargoes Surveyor should make sure that the cargo
presented for carriage under refrigeration should be pre-cooled to
the carrying temperature.
• There is always the possibility of a slight rise in the temperature of
the surface during transit which the ship can well take care of
provided the internal bulk of the packages are at the correct
temperature.
86. Survey of refrigeration equipment.
• Lloyd’s Register of shipping (LRS) notation
“ RMC (Refrigerated Machinery
Certificate)– issued to ships.
87. • Annual survey:
• Check condition of
the installation as a
whole is satisfactory
& the machinery is
operating reliably.
• Visual inspection of:
• Motors,
• Coolers,
• Piping ,
• Insulation of cargo
chambers,
• Low temperature pipes
and
• Thermometers and
• Pressure gauges.
88. • Special survey:
• By opening up the plant and the
machinery every five years.
• Compressors,
• Coolers,
• Evaporators to be examined.
• Insulation to check. Polyurethane to check
for shrinkage and absorption of water.
89. Questions from Part 1.
1. Write short notes on: - a). Latent Heat, b). Saturation temperature,
c). Properties of Refrigerant gases. e). Enthalpy, f). Entropy.
2. With aid of suitable sketches, explain refrigeration cycle of vapour
compression system.
3. A). Sketch & describe a freon compressor. B). Sketch & describe
a cylinder head assembly of a freon compressor.
4. Explain the importance of an oil separator & describe its function.
5. Sketch & describe working principle of thermostatic expansion
valve in a vapour compression system.
6. what are the safety devices in a refrigeration system? Explain with
a neat sketch, working of high pressure cut out.
7.
90. Questions from Part 2
1. Explain with the help of a sketch, the working principle of a domestic
refrigeration system for meat & Vegetable rooms in ship. Explain how
temperatures are maintained in each rooms.
2. Explain the term de-frosting. Describe a). Hot gas de-frosting, b).
Electric de-frosting.
3. Write short notes on: -a). Oil charging, b). Refrigerant charging, c).
Purging, d). Live cargo and dead cargo.
4. Explain with the help of a diagram, the heat balance in a simple
refrigeration system.
5. Draw a sketch showing details of a reefer cargo hold insulation.
6. Explain with the help of a sketch, the working principle of reefer
container.
7. Explain with the aid of a sketch, the working principle of refrigeration
system of a reefer cargo hold.
91.
92. • The Coefficient of Performance (COP) expresses the
efficiency of this cycle.
• Knowing that the aim of the refrigerator is heat removal
and that this process requires work.
93.
94. Heat balance.
• Q1= heat from the cargo
is given to refrigerant at
the evaporator coil.
• Q2 = heat from the
compressor is given to
the refrigerant while
compressing the gas.
• Q3 = heat given out to
sea at the condenser.
(refrigerant turns back
into liquid).
• Q1 + Q2 = Q3
• Coefficient of
performance(COP)
=cooling effect / work done.
• = Q1 / Q2
