|The shape of the ventilation holes com in various configurations
Ventilated containers are also known as passive (naturally) ventilated or coffee containers. Ventilation is provided by ventilation openings in the top and bottom side rails. The openings do not let in spray, to prevent depreciation of the cargo by rain or spray, for example. If actively ventilated containers are required, i.e. containers with adjustable ventilation, porthole containers may be used, which simultaneously act as insulated or refrigerated containers.
Lashing rings, to which the cargo may be secured, are installed in the upper and lower side rails and the corner posts. The lashing rings may take loads of up to 1,000 kg. The common size for ventilated containers is 20'. Ventilated containers are used especially for cargoes which have to be ventilated in transit. One of the most significant of such commodities is green coffee beans, hence the name coffee container.
This type of refrigerated container has an integral refrigeration unit for controlling the temperature inside the container. The refrigeration unit is arranged in such a way that the external dimensions of the container meet ISO standards and thus fit into the container ship cell guides, for example. The presence of an integral refrigeration unit entails a loss of internal volume and payload. When being transported by ship, integral units have to be connected to the on-board power supply system.
The number of refrigerated containers which may be connected depends on the capacity of the ship's power supply system. If the aforesaid capacity is too low for the refrigerated containers to be transported, power packs may be used, which are equipped with relatively large diesel generators and satisfy ISO requirements with regard to the dimensions of a 20' container. When at the terminal, the containers are connected to the terminal's power supply system.
For transport by road and rail, most integral unit refrigeration units are operated by a generator set (genset). This may either be a component of the refrigeration unit or connected to the refrigeration unit. Air flows through the container from bottom to top. In general, the warm air is drawn off from the inside of the container, cooled in the refrigeration unit and then blown back in the container as cold air. To ensure adequate circulation of the cold air, the floor is provided with gratings. Pallets form an additional space between container floor and cargo, so also forming a satisfactory air flow channel. In addition, the side walls of the container are corrugated, which ensures satisfactory air flow there too. In the upper area of the container, adequate space (at least 12 cm) must likewise be provided for air flow. For this purpose, during packing of the container adequate free space must be left above the cargo.
The maximum load height is marked on the side. To ensure vertical air flow from bottom to top, packaging must also be appropriately designed and the cargo must be sensibly stowed. In addition to temperature regulation, integral units also allow a controlled fresh air exchange, for example for the removal of metabolic products such as CO2 and ethylene in the case of the transport of fruits.
In the refrigeration units, both the supply and return air temperatures are measured and, depending on the operating mode, one of these values is used to control the cold air. Temperature measurement may be performed in various ways. The Partlow recorder generally records return air temperature, since this provides an indication of the state or temperature of the cargo. Data loggers are increasingly used, which detect temperature digitally and indicate it on a display. Once transferred to a PC, the data may then be evaluated.
MODIFIED/CONTROLLED ATMOSPHERE CONTAINERS
With the increase in exotic food cargoes, special containers have been devised that can modify or control the atmosphere within the container to the precise requirement of the foodstuffs. To prolong the life of cargo, containers with control of the gas levels are now used. 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. 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.
REFRIGERATED CONTAINER (PORTHOLE)
This type of container is often referred to not as a refrigerated container but as an insulated container, as it has no integral refrigeration unit. The lack of a refrigeration unit allows such containers to have a larger internal volume and payload than integral units. On board, the inside of the container is supplied with cold air via the ship's central cooling plant. The air flows through the container in the same way as in integral units. Cold air is blown in at the bottom and the warm air is removed at the top.
Off the ship, the temperature is controlled by a terminal refrigeration system or clip-on units. After completion of transportation, the clip-on units may be returned using special frameworks, dimensions of which match those of a 20' container. On the opposite end wall from the door, the containers are provided with openings for supply and return air. In general, supply air is blown into the lower opening, distributed by means of the gratings in the container floor, conveyed upwards through the cargo and discharged via the return air opening. This type of container also requires adequate air flow. For this purpose, appropriate air-ducts must be provided in the floor and the ceiling and the cargo must be sensibly packaged and stowed. Porthole containers do not have an integral temperature display. Either such a display is installed in the terminal refrigeration systems or the clip-on units or the temperature values may be obtained from the ship's central cooling plant. If the porthole-containers are provided with clip-on units when ashore, they no longer fulfil ISO requirements with regard to dimensions.
The doors constitute a weak point in both integral units and porthole containers. Wear to rubber door gaskets or improper handling may result in the doors no longer closing correctly, so that they are no longer sealed against rainwater and the like. During transport of chilled goods and frozen goods, water ingress may lead to cargo spoilage or to ice formation in the door area. In addition, refrigeration capacity has to be increased to compensate for losses due to cold air leakage.
In the case of frozen cargo and cargo containing non-respiring goods (goods other than fruit and vegetables), the goods are usually packed using the block stowage method. The cold air only flows around the goods and does not circulate between the boxes. Here it is important for the cargo to be pre-chilled to the required temperature before it is loaded into the container. If a load which is too warm is loaded into a refrigerated container, the heat is passed to the air and the cooling effect of the refrigeration unit is not passed to the cargo. If the air cannot pass the available cooling capacity to the cargo, it is cooled rapidly by the high cooling capacity of the refrigeration unit, and the actual cargo requires a considerably longer period for refrigeration. Refrigerated containers are used for goods which need to be transported at a constant temperature above or below freezing point.
Flatracks consist of a floor structure with a high loading capacity composed of a steel frame and a softwood floor and two end walls, which may either be fixed or collapsible. The end walls are stable enough to allow cargo securing means to be attached and several flatracks to be stacked on top of one another. Flatracks are available in 20' and 40' sizes.
A number of lashing rings, to which the cargo may be secured, are installed in the side rails, the corner posts and the floor. The lashing rings may take loads of up to 2000 kg in the case of 20' flatracks or up to 4000 kg in the case of 40' flatracks. Some types of 20' flatracks have forklift pockets. 40' flatracks have gooseneck tunnels at each end. In addition, they are sometimes equipped with lashing winches with 2 metric ton lashing belts. For transport of certain cargoes, flatracks may be provided with stanchions.
The maximum payload may be used only if the load is distributed evenly over the floor structure. If the weight of the cargo is applied to only a small proportion of the floor, it must be distributed and the manufacturer of the flatracks may have to be consulted on safety issues.
Flatracks are mainly used to transport heavy-lifts and overheight or overwidth cargoes.
Tank containers must be at least 80% full, to prevent dangerous surging of the liquids in transit. On the other hand, they must not as a rule be over 95% full, or there will not be sufficient ullage space for thermal expansion. Tank containers intended for transporting foodstuffs must be labeled Portable Liquids only. Some hazardous materials must be transported in tank containers with no in- or outlet openings below the surface of the liquid. Tank containers are generally designed for an operating pressure of up to 3 bar (above atmospheric). The test pressure used is 4.5 bar (above atmospheric). If the cargo requires temperature-controlled transport, tank containers can be equipped with insulation or heating. The temperature of the cargo may be precisely controlled using temperature sensors. Used for fruit juices, spirits, sweet oils hazardous materials such as fuels, toxic substances, corrosion protection agents.
OPEN SIDED CONTAINER
Open-sided containers (OS) have solid end walls and a solid roof panel. The sides may be closed at the bottom by folding down wooden, aluminium profile or steel sheet side walls, which may be divided into sections. Roof bow holders and roof bows are provided for the upper part, which may be covered with tarpaulins. The container is packed from the side. Open-sided containers also exist which are open only on one side. If bars are positioned over one open side, the containers can be used for transporting livestock. Another variant is the folding side wall container.
The current standard which deals with the coding, identification and marking of containers is DIN EN ISO 6346, dated January 1996. Among other things, this standard specifies that the previous standards with similar content have equal validity, since a number of older versions of containers with different markings naturally remain in service alongside the brand new ones.
1 owner code, consisting of three capital letters
2 product group code, consisting of one of capital letters U, J or Z
3 six-digit registration number
4 check digit
The owner code must be unique and registered with the International Container Bureau either directly or through a national registration organization.
The product group code consists of one of the following three capital letters:
U - for all freight containers
J - for detachable freight container-related equipment
Z - for trailers and chassis
Additional information may be shown. Here is just one example.
US is the country code for the United States. The first digit of the size code indicates the length of the container, with the number 4 standing for a 40' container. The second digit indicates height and whether or not a gooseneck tunnel is present. In this example, the number 3 stands for a height of 8'6" with gooseneck tunnel. The first digit of the type code indicates container type. Here, 1 means that the container is a closed container with ventilation openings. The second digit of the type code relates to special features. The 0 used here means opening at the end.
Also shown is the gross and tare weights