All about reefer containers | What are the types of reefer containers?

Image credits: Thornton spares

Reefer container

The Reefer container is used for transporting perishables and its having own standalone cooling system

Refrigeration is the removal of heat from a substance and maintaining the cold state during storage and transportation in the cold chain. The purpose of refrigeration is to preserve the product and increase its shelf life.

Air circulation in units designed to distribute from bottom to top via specific T-shaped decking.

What is TEU?

Container ship capacity is expressed in Twenty-foot Equivalent Units (TEU)

Types of container ships

TYPE	TEU	LENGTH IN METER (Maximum)	BREADTH IN METER (Maximum)	DRAUGHT IN METER (Maximum)
PANAMAX	4000 TO 5000	294.1	32.3	12
SUEZMAX	About 12000	275	50 TO 57	14.4 TO 14.6
POST PANAMAX	About 12000	366	49	15.2
POST SUEZMAX	About 18000	285	60	21
POST MALACCAMAX	About 18000	400	59	14.5

Size of reefer container

SIZE	DIMENSION	VOLUME
20 FOOT	20 x 8 x 8.6	27m3
40 FOOT	40 x 8 x 9.6	67.5m3

What are the types of reefer containers?

MODE	TEMPERATURE RANGE	MAX TEMP OF CONTAINER
CHILLED Dehumidification range 65-85%	More than -3 degree Celsius	-30 to 30 degree Celsius
FROZEN	less than -3 degree Celsius	-30 to 30 degree Celsius
COLD TREATMENT	-1°C to +5°C	-30 to 30 degree Celsius
CONTROLLED ATMOSPHERE	02 (2-21%) C02 (2 -12%)	-30 to 30 degree Celsius
SUPER FREEZER	Maintain up to -65 degree Celsius	-65 to 30 degree Celsius

What is CHILLED MODE?

Air has to flow through the cargo at all times so that heat and gases are removed, therefore the cartons used should have ventilation.

Temperature control is accurately achieved through the supply airflow.

What is FROZEN MODE?

Air has to flow around the cargo so there should be no gaps between the cargo and the walls and the cargo itself.

Temperature control is accurately achieved through the return air.

What is the COLD TREATMENT?

The cold treatment used for eliminating the presence of an unusually large number of certain species of insects, like fruit flies, from import cargoes of US

The cold treatment is controlled by pre-loaded software and microcontroller

The CT reefer sensor and container must be approved by USDA

Before use, temperature sensors must be calibrated using an ice bath (mix of water and ice). This process is carried out by shore-side experienced staff.

Three probes are required for a USDA cold treatment procedure.

USDA: United State Department of Agriculture’s

Placement of probes

Sensor1

Placed next to the return air intake.

Sensor2

If 40 feet: five feet from the end of the load

If 20 feet: three feet from the end of the load

This is should be placed in a center carton at half the height of the load.

Sensor3

If 40 feet: five feet from the end of the load

If 20 feet: three feet from the end of the load

This sensor should be placed in a carton at a side wall at half the height of the load.

What is SUPER FREEZER?

The Super Freezer container maintains the temperatures as low as -60°C

What is CONTROLLED ATMOSPHERE REEFER?

Controlled atmosphere reefer is to maintain the quality of fresh commodities by continuously regulating the mix of O2 and CO2 inside the container

The principle of CA reefer

The fruit will respiration O2 and it will generate CO2. This will increase the CO2 level in the container. The vacuum pump will run and pull out CO2 when the CO2 level reaches above the CO2 set point. If O2 level goes below the O2 set point the fresh air vent will open for ambient air

What is the difference between a container ship and a cargo ship?

Bulk carrier- it carries cargo in bulk or packaged form

Container ship – it is carrying cargo only inside a container. The standard size of the container is 20 and 40 foot).

Reefer Facts

All reefer containers have bottom air delivery.
Supply air is measured (probe) at (1) and return air at (2).
Chilled loads are controlled by supply air temperature - why?
Frozen loads are controlled by return air - why?
All reefer units can be plugged to the power supply (440v 60Hz)

Defrost Management in Reefer container

Why defrost of reefer container necessary?

The defrost serves to move the ice from the evaporator that has evolved during cooling/freezing. This ensures effective cooling. Without this, the reefer will not work.

How is defrost done on reefer container?

It works by stopping the reefer machinery (reefer not cooling) and turn on a heating element that melts the ice. The duration is between 10-90 minutes depending on the amount of ice on the evaporator.

How often is it done?

Chilled cargo - every 06 hours (ventilation – open)
Chilled cargo - every 12 hours (ventilation – closed)
Frozen cargo - every 24 hours (provided the cargo is on temperature)
Defrost cycles can be set manually between 3, 6, 12, and 24 hours.

Why the difference?

As chilled products are more sensitive to temperature deviations, we must ensure that the reefer is working every single minute. If a chilled cargo is not cooled for some hours, it will affect the quality of the cargo/PSL.

Will defrost affect the cargo quality?

No, it will not. It actually helps the reefer to work more efficiently.

Studies have shown that the cargo temperature will not be affected at all during the defrost period.

Data logger function for reefer container

A computer that records data at a given interval during the voyage. Capable of measuring the following:

Temperature setting
Changes in setting temperature
Supply air temperature
Return air temperature
Status main power (on/off)
Battery power in use for recording
Recording of alarm
Up to 4 pulp temperatures (e.g. for cold treatment shipments)
Defrost activity
Status humidity control
Trip start
Pre-trip activity
Humidity readings
CO2 readings
O2 readings

Raw Data in reefer container

Example: Star cool reefer container

S - Setpoint change
D - Defrost start
d - Defrost end
A - Alarm
T - Trip start
E - Economy mode start
e - Economy mode end
B - Bulb mode start/change
b - Bulb mode end
R - Battery backup recording start
r - Battery backup recording end
O - Power loss
o - Power up

What are Probes?

Probes are used to record the cargo temperature of the cargo inside the reefer unit. Probes are cables with a temperature-sensitive element fixed to one end.

Placement of Probes in reefer container

The probe must be secured to the cartons to ensure that it does not detach during transport.

Unused length of the probes to be coiled up, placed ON TOP of the cargo, and secured.

The temperature-sensitive tip is to be inserted into the fruit without splitting it open. The tip must be covered, and can be inserted into more than one fruit if necessary.

Ventilation in reefer container – Why?

Remove Ethylene and CO2
Replenish oxygen
Only Chilled Commodities - down to -2 C
Settings of 5-75 CMH allowed, except for flower bulbs
Set at lowest safe value for the commodity to reduce power consumption (cost).

How Does Incorrect Ventilation Affect The Cargo?

Chilled cargo with closed ventilation:

Ethylene gas will not be removed

If the commodity is sensitive to ethylene, it will trigger an earlier than expected ripening process and the cargo will be discharged with less shelf life or damaged.

Carbon dioxide will not be removed

This may cause skin defects or other damage. Furthermore, for cargo with a high respiration rate, the product may use all the oxygen and produce CO2. When no more oxygen, the cargo will collapse/die (read total loss).

Frozen cargo:

For reefer containers with frozen cargo, ventilation must always be closed.

If ventilation is open, the outer layers of the cargo will be defrosted and this will eventually lead to cargo damage.

Humidity Control in reefer container

Humidity Control 65-80% R/H
De-humidifier function only
Commodities
Flower bulbs
Ginger
Garlic / Onions
Electronic equipment
Live plants
Tomatoes
Leather Garments
Effective from +28°F (-3 °C) to +86 °F (+30 °C) depending on type of reefer container.
At temperatures below +50 °F (+10 °C) the ventilation cannot be kept fully open.

PTI - Pre Trip Inspection in reefer container

A reefer container must normally be pre-tripped just before use, but the PTI is valid for a period of 60 days.

PTI consist of:

Visual check
Operational check, Auto PTI
Final check

What is Precooling in reefer terms?

When a precooled container is opened, the cold air rushes out, and warm ambient air rushes in.

Water from the warmer ambient air condenses in the container, particularly on the walls, ceiling and floor, and heats the walls to ambient temperature.

The water will then be transported by the air circulation in the container and deposited on the evaporator, resulting in too frequent defrost …

Precooling the reefer Container

Only when a cold tunnel is extended from the cold storage doors, covering the container doors, and sealing against ambient air is precooling of a container not detrimental to the safe transport of refrigerated goods.

Example of a ‘low-tech’ cold tunnel.

Stowage Guidelines of reefer container

Free airflow
Prevent movement of cargo

Distinguish between:

Frozen (non-living) products
Chilled (live) products
Chilled (non-living) products

Frozen cargo < +27 F / -3 C < Chilled cargo

Air Flow

The cargo must cover the entire floor to ensure proper distribution of cooling air.

Preventing Short Circuit

If the floor is not covered by the cargo, heavy cardboard must be placed where no cargo is stowed in order to ensure proper air distribution.

The Red Load Line in reefer container

To ensure correct airflow in the container all cargo must be stowed beneath the red load line.

If it is not, cargo damage is likely as air circulation is restricted.

In case of cargo damage to CY loads, MSL rejects liability as to the shipper is responsible for the correct stowage of the container (Shipper’s load, stow and count)

This does, however, not improve relations with our customers, neither the shipper nor the consignee and care should be taken to avoid the situation altogether.

Restricted airflow preventing the cargo from being kept at setpoint.

What is a hot-stuffing in reefer?

A hot-stuffing is when cargo is put into the container at a higher temperature than stated in the B/L

What happens when the temperature of the cargo is higher than the optimal storage temperature?

Shelf life rapidly decreases!

How to determine a hot-stuffing?

Probe readings on the Micro-processor (if probes inserted)

If the return air temperature is higher than 10F from set-point

Acceptance Policy for Hot-stuffed Cargo

The return air temperature of up to +10F higher than the set-point.

If the deviation is > 10F above set-point the regional reefer management must be contacted.

NOTE: Chilled meat, Shellfish, IQF and Ice cream are exceptions as they are to be considered hot stuffed if more than 5F above set-point.

Super Freezer Containers specifications

Temperature Range:

-10 C to -60 C

14 F to -76 F

Advantages of Super Freezer Containers

Global Coverage
Limited rehandling of the products
Provides an unbroken cold chain to the final place of delivery
Fast delivery due to shipment in smaller quantities
Reduced cold storage costs
Extended season as less cargo is required to make a shipment
Steadier supply and production

What is a Blast Freezer?

It is a Freezer capable of freezing down 7 tons of fresh fish down to -76 F (-60 C) within 24 hours

Controlled Atmosphere System (CA Reefer)

Normal Atmosphere

Nitrogen 78%
Carbon Dioxide .03%
Oxygen 21%

Typical Desired Atmosphere

Nitrogen 96%
Carbon Dioxide 2%
Oxygen 2%

CA Development

Reef Only:

Practical Storage (Shelf) Life (PSL) of product extended through cooling thus reducing the respiration rate.

Modified Atmosphere:

PSL (Practical Storage Life) of Product extended Further by one only O2/ CO2 level adjustment PRIOR to shipment. Perfectly sealed container required otherwise MA lost.

Controlled Atmosphere:

PSL extended to the maximum through the continual Atmosphere control of O2 / CO2 levels around product throughout the shipment period.

O₂ level decreases and CO₂ level increases due to cargo respiration. Addition of N₂ further decreases O₂ level and maintains levels at set point

What Is a Starvent?

High ventilation container with no cooling capacity.
Thus it is NOT a refrigerator but just a high ventilated container.

Must be plugged to electricity

Starvent Containers

The following commodities benefit from the fresh air ventilation of 2000 / 4000 CBM/HR which the Starvent units are able to provide:

Onions
Potatoes
Garlic
Ginger etc…

What are the checks carried out while loading after reefer container at PORT?

15 important Pre checks have to carry out after loading the reefer container at the port

Check the set temperature and ventilation settings according to reefer manifest
Check the stowage location according to reefer manifest
Check the condenser for any leakage, structural damage and excessive corrosion
Check the compressor oil level and leaks
Check the pipes, connectors, and components for leakage, and any damages
Check the drain hose for damage and clogged
Check the wiring for any loose connections
Check the contactors for like burned or any damage
Check the moisture indicator
Check the filter dryer for any damage and deterioration
Check the power cable and plug for any damage and if you found any joint between the cables, ensure the proper splicing
Check the presence of alarm and alarm history
Check the temperature history
Check any abnormal noise or vibration
Check the control box door for firmly tightened to prevent any liquid or water damage

In case of reefer failure, huge differences in actual temperature from set temperature and if you found any abnormal conditions from above checks immediately inform to Duty officer(Chief engineer also) and reefer technician

What are the pre-checks carried out for CA REEFER?

Follow the above-mentioned checks

Additional checks:

Check the drain pipe-pipe should be upright position and filled with water
Check the Vacuum pump oil level
Make sure the CO₂ and O₂ level settings as per reefer manifest
Check the history of CO₂ and O₂ levels.
Check the structural damages on the container
Check the service hatches condition and installed correctly
Make sure the fresh air module is perfect condition and butterfly nut condition
Check the drain plug for leaking or water condensation
Check the door gasket for water condensation

What are daily checks carried out while carrying reefer containers on ships at sea?

Make sure the temperature is an in-range condition
Check the active alarms
Check the compressor oil level
Check the running machine vibrations
Check the dryer conditions
Check for any refrigerant leakage

In case of a reefer container malfunction, the malfunctions should be reported without a delay to concerned-parties as required by the voyage or company instructions.