IMDG Code 4.1.1.4 mandates that an Intermediate Bulk Container (IBC) must not be filled beyond 98% of its water capacity at a mean bulk temperature of 50 °C. This limit is kept because liquids expand as temperature rises and if there is no ullage space left to accommodate that expansion, the excess volume generates increasing internal pressure with no place to go.

Unless specific provisions are prescribed, liquids shall not completely fill a packaging at a temperature of 55°C. However, sufficient ullage shall be left in an IBC to ensure that at the mean bulk temperature of 50°C it is not filled to more than 98% of its water capacity. [4.1.1.4 of IMDG Code 32-24]

What can go wrong if a liquid if filled more than the limit specified in 4.1.1.4

The following hazards are the probable outcomes of exceeding this limit:

1. Liquid Escaping from the Top Fill Port
2. Bulging of the IBC
3. Rupture of the IBC
4. Spillage, Fire, and Other Transport Hazards

• Flammable liquids (Class 3): Vapours accumulate in enclosed CTU/cargo holds and create an explosive atmosphere resulting in fire or explosion.
• Corrosives (Class 8): Escaping liquid attacks adjacent packaging, cargo, and vessel’s steelwork. Personnel contact can cause chemical burns.
• Marine pollutants: Any release overboard triggers obligations under MARPOL Annex III and may result in port state control action, fines, and reputational consequences for the carrier.
• General spillage: Even non-hazardous liquids create slip hazards, cargo damage claims, and delays.

You may use the calculator below to ensure that the quantity loaded into an IBC at ambient temperature translates to no more than 98% of capacity.

This will ensure compliance to the Code, Safety and Protection of Marine Environment during transport.