20' Porthole Container

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 transport, 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 fulfill ISO requirements with regard to dimensions.

Dimensions / weights

The following are some of the most important details relating to refrigerated container types.
The data was taken from Hapag- Lloyd, Hamburg.

¹) Not suitable for transporting foodstuffs
²) Suitable for clip-on generators