Why Ullage Matters in IBC Shipments

Why Ullage Matters in IBC Shipments

Why IBC Filling Limits Matter

When shipping liquids in Intermediate Bulk Containers (IBCs), one critical safety consideration is allowing enough space for thermal expansion. As temperatures rise during transport, liquids expand. If an IBC is filled completely, the expanding liquid may create pressure inside the package, potentially leading to leaks, deformation, or even failure of the container. For this reason, dangerous goods regulations establish limits on how full an IBC may be filled.

North American Requirements for Ullage

In Canada and the United States, the regulatory approach is essentially the same. Under the Transportation of Dangerous Goods Regulations and the U.S. hazardous materials regulations in 49 CFR, liquids must be loaded so that sufficient ullage remains and the IBC will not exceed 98 percent of its water capacity at a mean bulk temperature of 50 °C (122 °F). This requirement assumes that packages may be exposed to elevated temperatures during transportation and ensures that there is enough space inside the IBC to safely accommodate the expansion of the liquid.

How ADR Approaches Filling Limits

The European system under ADR, which follows the framework of the regulation, takes a slightly different approach. It provides two possible methods for determining filling limits. One option uses a table that relates the filling temperature to a maximum percentage of capacity, while the other uses a mathematical formula based on the coefficient of thermal expansion of the liquid. Both methods ultimately serve the same purpose: ensuring that enough space is left inside the packaging to safely accommodate expansion during transport.

Example Calculation for a 1,000-Litre IBC

A simple practical example helps illustrate the North American approach. If an IBC has a water capacity of 1,000 litres, the maximum permitted filling amount would be:

1,000 L × 0.98 = 980 L

In this situation, the IBC should be filled with no more than 980 litres, leaving approximately 20 litres of ullage. This remaining space allows the liquid to expand if the temperature increases during transport.

Don’t Forget Maximum Gross Mass

It is also important to remember that IBCs display a UN performance marking on the outside of the container. This marking includes a maximum permissible gross mass, which represents the total allowable weight of the filled IBC, including the packaging itself. Since liquids have weight and different products can vary significantly in density, shippers should always verify that the combined weight of the product and the IBC does not exceed this marked limit. Even if the filling volume is acceptable, exceeding the maximum gross mass would still place the package out of compliance.

The Key Takeaway

Although the regulatory wording differs slightly between regions, the safety principle remains the same worldwide: liquid dangerous goods should never be filled completely into an IBC. Maintaining sufficient ullage and respecting the maximum permissible gross mass are both essential steps for preventing leaks, protecting the integrity of the packaging, and ensuring the safe transportation of hazardous materials.

Stay up to date and sign up for our newsletter!

We have all the products, services and training you need to ensure your staff is properly trained and informed.

Shipping Dangerous Goods by Ground

CFR 49 Publications

Shipping & Handling Labels