3 Allowable stacking mass

3.1          The allowable stacking mass represents the maximum superimposed load that any freight container can be subjected to and is often referred to as the stacking capability or stack height (when converted to a number of freight containers).

3.2          Freight containers built to the provisions of ISO 1496 are required to withstand a minimum superimposed load of 192,000kg. This value is the equivalent of eight superimposed freight containers with an average mass of 24,000kg.

3.3          Freight containers having an allowable stacking mass of less than 192,000 kg are not unrestrictedly suitable for sea transport. This includes:

• Freight containers built to a previous standard;
• Swap bodies;
• Freight containers designed to be used with one door removed/open.

3.4          Swap containers and tanks have a different design and therefore a different stacking capability. The wider designed width of the swap bodies means that there is a step between the corner posts and the top corner fittings which are shown clearly on the swap tank as shown in figures 4.8 and 4.9.

3.5          Freight containers with a step of this nature will generally have a lower stacking capability. The freight container may be marked with a warning decal that indicates that there is a reduced stacking capability.

3.6          Freight containers with one door off / open will have reduced allowable stacking mass and racking as shown in figure 4.10.

Figure 4.10 CSC safety approval plate for one door off operation

3.7          The practice of transporting cargo in one door open or one door removed freight containers is inherently dangerous and therefore is strongly discouraged. The practice is illegal unless it is marked on the CSC plate (see figure 4.10). Additionally, there may be negative consequences to using this practice in the supply chain (e.g. terminals refusing to handle open door freight containers).

3.8          Where there is reduced allowable stacking mass, due to design or operation, the total gross mass of freight containers and swap bodies placed above should not exceed this value.

3.9          Freight containers which are designed with an allowable stacking mass less than 192,000 kg should be marked in accordance with ISO 6346. This means that the fourth character of the ISO size type code will be a letter.