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

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    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

    LENGTH IN METER (Maximum)
    BREADTH IN METER (Maximum)
    DRAUGHT IN METER (Maximum)
    4000 TO 5000
    About 12000
    50 TO 57
    14.4 TO 14.6
    About 12000
    About 18000
    About 18000

    Size of reefer container

    20 FOOT
    20 x 8 x 8.6
    40 FOOT
    40 x 8 x 9.6

    What are the types of reefer containers?

    range 65-85%
    More than -3 degree Celsius
    -30 to 30 degree Celsius
    less than -3 degree Celsius
    -30 to 30 degree Celsius
    -1°C to +5°C
    -30 to 30 degree Celsius
    02 (2-21%) C02 (2 -12%)
    -30 to 30 degree Celsius
    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

    Placed next to the return air intake.

    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.

    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


    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
    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 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.

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