Stacking in storage (static load)
The UN mark on an IBC rated for Hazardous Materials includes a maximum stacking load in kg– this is the 6th element in the mark. This value represents the maximum load allowed to be stacked above the IBC in storage (not in transportation), and is a maximum value established during the UN design type test for the IBC.
Stacking in transportation
DOT Regulation 49 CFR 178.703 requires a symbol identifying the maximum stacking load in kg. This maximum stacking load in transportation is designated by the manufacturer and can be no greater than the amount calculated by dividing the maximum stacking load in storage (static load) by 1.8. For IBCs not designed for stacking, an alternate symbol is required to represent “no stacking”.