Archive For November 2009

Wednesday, November 25, 2009

REEFER CONTAINER AIR-DELIVERY SYSTEMS

All reefer containers are bottom-air delivery units, which means that air is consistently supplied from the bottom of the container through the T-bar floor.
The advantage of technology advanced reefer airflow system is that it delivers uniform and consistent air temperature across the entire floor and throughout the entire cargo area.
The precise air temperature, in combination with high evaporator airflow protects fresh products against moisture loss and shrinkage so that sensitive perishable products will stay fresher, longer and in better quality when they arrive at the final destination.

POWER SOURCES AND PORTABLE GENERATORS

ALL refrigerated containers operate on external power sources. Power supply used must be either 380 volts/50 Hz or 440 volts/60 Hz.

Some reefers are equipped with dual voltage supply inclusive of power supply of 190 volts/50 Hz or 220 volts/60 Hz.

Containers may be plugged into a vessel's main power supply or equipped with portable generators for land use. Two types of portable generators are available:

Clip-on generator
For use with refrigerated cargo moving on trains or trucks; attached to the front (nose) of the container.

REEFER CONTAINER MODIFIED/CONTROLLED ATMOSPHERE

When using the modified atmosphere technology, a container is purged of most gases first before a new mixture of gases - at optimum levels and amounts for the commodity being shipped - is injected into the container after it has been sealed. This modified atmosphere technology is a supplement to temperature management that provides more precise control than fresh air exchange. It is effective in slowing respiration and retarding the production of ethylene in horticultural commodities. Lettuce, for example, can be transported across the Pacific using modified atmosphere with excellent results. The modified air content of a container, however, can change during a trip due to the respiratory activity of the commodities and pressure changes in the container, thereby reducing its effectiveness at retarding the deterioration of fresh produce.

Controlled atmosphere is the most technologically advanced process that is used to precisely control the atmospheric composition within the container throughout a shipment's entire journey. Controlled atmosphere can increase the post-harvest life of some perishables by two to three times longer than other methods.

Controlled atmosphere technology uses computer systems to monitor and control the atmosphere in the container and make adjustments during the trip. These systems also record changes in the atmospheric composition during a container's journey and provide a printout for quality-control purposes.

Excellent out-turn of asparagus after 18 days of voyage under 10% O2 and 10% CO2 controlled atmosphere condition.

The composition of the controlled atmosphere transport is commodity-specific. Atmospheric conditions are custom-tailored to provide an optimum environment for each commodity. The availability of controlled atmosphere is important in opening new markets for shippers, allowing the ocean carriage of commodities previously transported by airfreight. Controlled atmosphere can also be used to meet the needs of a particular market by manipulating the ripening rate of fruits and vegetables. Some of the products benefiting from controlled atmosphere include sweet cherries, nectarines, peaches, broccoli, asparagus, avocados, mangoes, cut flowers and chilled meat.

Successful shipping of these commodities is supported by many years of university and industry research. MA and CA differ only in the degree of control. However, CA is more precise in controlling the level of gases. In summary, the following are the key potential benefits of MA/CA shipment which of course is dependent upon the commodity, variety of cultivars, duration of storage, correct post-harvest handling and proper temperature management (most critical factor).

Retard ripening and slow down respiration, ethylene production rates.

Direct or indirect effect on post-harvest pathogens, reduce decay incident and severity.

Alleviate certain fruit physiological disorders such as chilling injury.

Useful tool for insect control in some commodities to meet quarantine requirements of importing countries.

Appropriate level of gases (O 2 & CO 2 ) is essential to attain the potential benefits.

REEFER CONTAINER COLD TREATMENT

Cold treatment is a special post-harvest handling process for perishables to meet local quarantine requirements (e.g. US Department of Agriculture). It is a means of insect control by exterminating Mediterranean and certain tropical fruit flies and larvae.

This is achieved by maintaining a sufficiently low temperature, uninterrupted for a pre-determined duration of time. Cold treatment protocol includes the number of probes, treatment temperature and duration which vary according to different kinds of fruits and depend on the agreement between the country of export and import.

The use of cold treatment process is to eliminate the need for fumigation and the use of certain insecticides, which may be illegal in some countries due to environmental reasons. In general, cold treatment is primarily applicable for various types of citrus fruits such as oranges, lemons and is also common for apples, pears, lychees, star fruits, avocados and kiwi fruits.

Rigid adherence of appropriate cold treatment procedures - product pre-cooling, correct loading and packaging, probe calibration and continuous temperature monitoring - is very critical in preventing process failure. To ensure successful cold treatment shipment, dedicated and experienced APL staff will assist and supervise the installation, loading and monitoring during the entire voyage.

REEFER CONTAINER DEHUMIDIFICATION MODE

The purpose of dehumidification is to reduce or lower the relative humidity in the container during transportation.

Low relative humidity ensures dry packaging, prevents rotting and reduces incident of fungal development and is essential for cargo such as cigarette, electronic components, photographic films, onions, ginger and garlic etc.

Almost all BLUE DOLPHINS reefer equipment are equipped with dehumidification systems, where relative humidity can be set between 65% and 95% and can be controlled according to cargo requirements.

Bulb mode

Bulb mode is an extension of dehumidification mode and upon activation, the user has the option to select the evaporator fan speed (low, high or alternate) and defrost termination sensor setting.

In addition, the relative humidity setting is available from 60% to 95% (instead of the normal 65% to 95%).

Bulb mode is utilized mainly for transportation of flower bulbs, and BLUE DOLPHINS provides containers that are certified by ATO (Agrotechnological Research Institute).

Tuesday, November 24, 2009

REEFER CONTAINER FRESH AIR VENTILATION

Fresh-air exchange helps prevent unwanted ripening and the accumulation of odors, and ensures longer shelf life for many perishables. It is particularly useful for commodities that produce high levels of ethylene, like tomatoes and apples.

The amount of fresh air needed depends on the tolerance of the commodity to low levels of oxygen and high levels of carbon dioxide and ethylene, as well as the rate at which the commodity respires and produces ethylene.

Fresh-air exchange systems can be set at different levels and are measured in cubic feet per minute (cfm) and in cubic meters per hour (cmh).

Fresh-air exchange involves flushing the container with air from the outside through vent holes. The fresh air ventilation technique is essential to protect some agricultural products by removal of unwanted heat, gases, and carbon dioxide produced by the cargo. However, excessive ventilation may result in freezing of the evaporator coils and will need additional defrost to remove the ice build-up.