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Reefer container machinery troubleshoot safety guide

In the event of a container machinery failure beyond the capability of ship's staff to rectify, it may be possible to save some of the cargo by adopting emergency procedures.

If the cargo is hard or deep- frozen in a well insulated container with good door seals it should survive for several days depending, of course, on the ambient temperature. Shielding from direct sunlight will help. Even then the probability is that only the outer portions of the cargo will suffer, but undoubtedly the best way of dealing with such a situation is to introduce coldness to the cargo. This can be done by dumping liquid nitrogen or carbon dioxide into the container and allowing it to vaporise within the space, when any heat that has leaked in will be consumed. It should be ensured that the gas used will not harm the cargo (not normally a problem with hard frozen products) and that the cargo will not be adversely affected by the very low temperatures produced, particularly locally when the gas enters the unit. It is not possible to regulate the temperature when resorting to this method of refrigeration and it is quite unsuitable for chilled cargoes.

Solid carbon dioxide (dry ice) may be a suitable alternative. Normally supplied wrapped for protection during handling, it is necessary to open the wrapping to permit evaporation. The more exposed the blocks from their wrappings, the more rapid the evaporation the greater cooling effect­and the shorter the life of the blocks, although there is little point in economising on carbon dioxide to the possible detriment of the cargo. Care should be taken when handling blocks of dry ice; the extreme temperature may cause severe burns on contact with bare skin.

Neither of these gases, nitrogen or carbon dioxide, will support life so apart from the damage they would do to living fruit cargoes, when opening a container which has received this treatment personnel should ensure that adequate time has been allowed for ventilation before entering. Being heavier than air these gases should flow out like water but there is always the possibility of pockets trapped in a tight stow.

None of these methods (dumping of carbon dioxide or nitrogen, or the use of dry ice) are suitable for chilled living cargoes as the rapid introduction of nitrogen or carbon dioxide will kill the product either by the very low local temperature and/or the effect of the gas itself on respiration (although it is possible for these gases to be introduced in small quantities using sophisticated control equipment).

Where chilled live cargoes are involved, shading from the sun, even hosing down of the container, will help but inevitably the temperature will rise and the ripening process accelerate. Ventilation at this time is essential to remove harmful vapours produced by the cargo and replace the oxygen necessary for the health of the fruit, although this may give rise to an increased rise in temperature. Only speedy transfer of the cargo to a more acceptable environment will continue to prolong its storage life.

Commodities Shipped In Reefer Containers - how to maintain optimum condition ? (Information only)

In general, refrigerated commodities may be divided into two distinct categories;

a) Chilled
b) Frozen

Many chilled cargoes (e.g. fruit) are regarded as a "Live" cargo since they continue to respire post harvest and as such are susceptible to desiccation (wilting and shriveling). This is not the case with commodities such as chilled meat or cheese.

The minimum fruit carriage temperature is usually no lower than -1.1 degree C (30degreeF).

Frozen cargo is regarded as "inert" and is normally carried at or below -18 degreeC (0 degree F).

However, both categories are highly perishable and require care in handling to ensure arrival in optimum condition. In chilled commodity transportation, the ventilators are normally left in an open position, with a limited number of exceptions (e.g. meat, chocolate, film, chemicals, dairy products, and controlled atmosphere shipments).

Some cargoes may require controlled humidity (e.g. flower bulbs). It should be remembered in such cases that many refrigeration units are only capable of reducing humidity within the cargo space and the settings should be applied accordingly.

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