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Container refrigeration - Puprpose of dedicated reefer ships

Refrigeration on board ships

Containership underway

Today, a newbuild Panamax containership of 4,600TEU will typically have capacity for 700 reefer plugs, and with a full load will consume 18 tonnes of HFO per day. However, you cannot just load a container, plug it in and play it like a computer component. Questions on requirements of the content and the power consumption demanded are just some of the items that a refrigeration technician must consider.

With a growing global refrigerated trade of 50M tonnes p.a, and with few dedicated reefer ships on order, growth is going to be seen in the available refrigerated capacity on container ships. However, increased reefer cargo claims point to a lack of knowledge by both ship and shore personnel.

Dedicated reefer ship
Fig: Dedicated reefer ship underway

Purpose of reefer ships

Many of the container ships operating on trade routes where refrigerated cargoes were carried in conventional refrigerated cargo liners (‘reefer ships’) have provision for carrying refrigerated containers and have in many cases replaced the latter.

The ISO containers (usually 20 foot size since with most refrigerated cargoes 40 foot size would be too heavy) are insulated, and below decks the end of each hold may be fitted with brine coolers which serve each stack of containers. Air from the brine coolers is ducted to and from each insulated container. Connection of each container to the cold air ducts is by means of an automatic coupling which is remotely controlled and can be engaged when the container is correctly positioned in the cell guides.

The below decks system described with fully insulated containers means that heavy insulation of the hold space is unnecessary. On the ships sides, bulkheads and deckhead about 50 mm of foam insulation with a fire retardent coating may be fitted and the tank top covered with 75 mm of cork and bitumastic. If provision is only made for the ship to carry a part load of under deck refrigerated containers these are generally arranged in the after holds adjacent to the machinery space.

On deck refrigerated containers are generally serviced by clip-on air cooled electric motor drive cooling units. The units are plugged into the ships electrical system by way of suitable deck sockets. Similar water cooled units have been used for below deck containers on short haul voyages.

Other useful articles :
  1. Methods of refrigeration

  2. Refrigeration is essentially the removal of heat through the process of evaporation. We choose to refrigerate commodities such as fruits and vegetables because we want to prolong their “practical shelf life” – the time from harvest until the product loses its commercial value.
    More .....

  3. Reefer cargo stuffing

  4. it is essential that all products are treated correctly prior to stuffing. Even though the temperature, ventilation and humidity are all optimal during the entire voyage, products will only arrive in perfect condition if the pre-treatment has been performed correctly. Successful shipping begins at the product sourcing area.
    More .....

  5. Growing demand for container refrigeration

  6. On deck refrigerated containers are generally serviced by clip-on air cooled electric motor drive cooling units. The units are plugged into the ships electrical system by way of suitable deck sockets.
    More .....

  7. Frozen products packaging requirement

  8. Proper packaging procedures will help protect frozen cargo during transport. Frozen products do not require air holes in the top and bottom of the cartons. Air flowing around the load is sufficient to remove heat that has penetrated the container. The cartons should be stacked directly on top of each other to take advantage of their strength in the corners.
    More .....

  9. Packaging & stowage guideline for reefer cargo

  10. Packaging plays an important role when it comes to protecting the cargo. The packaging material must be able to support a stacking height of up to 2.4 metres (7’10’’). The material should be able to withstand humidity without collapsing, and should allow the passage of an adequate vertical airflow through the cartons in order to maintain the desired temperature..
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  11. Choice of packaging for various commodities

  12. Goods should be well stowed within the package, evenly distributed and properly secured. Items completely filling the case or carton contribute to the strength of the whole package. Items which do not completely fill the package must be cushioned against shock or vibration.
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  13. How to keep cargo fresh ?

  14. Proper ventilation of fresh, chilled products is necessary to remove the heat, carbon dioxide and other gases produced by the cargo. Heat is removed by continuously circulating the internal air, whereas carbon dioxide and other gases are removed by replacing the internal air supply with cooled fresh air..
    More .....

  15. Loading precautions for refrigerated cargoes

  16. Refrigerated cargoes include meat carcases, carton (packed) meat, fruit, cheese, butter, fish and offal. Ships are specifically designed for their carriage, with separate spaces in holds and ’tween decks, each fitted with suitable insulation and individual control of ventilation. Ordinary general cargoes may be carried in the spaces at other times, the temperature being regulated accordingly for the type of cargo being carried.
    More .....

  17. Role classification societies maintaining seaworthiness of vessels

  18. classification societies publish rules and regulations which are principally concerned with the strength of the ship, the provision of adequate equipment, and the reliability of the machinery .
    More .....

  19. Periodic survey requirement by classification societies

  20. To maintain the assigned class all steel ships are required to be surveyed and examined by the Society’s surveyors at regular periods. The major hull items to be examined at these surveys only are discussed here..
    More .....

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