Urea Cargo Clumping: Causes, Assessment, and Recommendations

Our surveyor arrived at the shipside at around 1650hrs this afternoon and immediately inspected the bagged cargo. We discovered that the cargo at the shipside had clumping, where the caked cargo could be easily crushed by hand and no obvious water was found.

In the case of urea, when the water vapor pressure in the surrounding air is higher than the saturation vapor pressure of the solution at that temperature, the water in the air is absorbed onto the surface of the solid urea, increasing the water content in the urea. Given enough time, the urea will completely deliquesce. Conversely, if the water vapor pressure in the air is lower than the vapor pressure of water on the surface of the urea, the water will evaporate and transform back into a solid.

During the storage and stacking process of urea, the granules come into close contact with each other. With the change in temperature of the urea granules and the humidity of the surrounding air, there is a process of moisture absorption and evaporation on the surface of the urea granules. This leads to the appearance of a surface liquid film, causing recrystallization of the particles. The newly crystallized urea sticks together with other crystals, resulting in clumping.

Therefore, the occurrence of clumping usually indicates that the cargo may have been stored for a long time or has been exposed to a humid environment.

Due to the current storage and transportation conditions of urea, it is almost inevitable to have pseudo-clumping (normal water content) in bulk cargo transportation. Based on our experience, a common method to determine whether the cargo is pseudo-clumped is to check if the clumped cargo can be easily crushed. If the cargo can be easily crushed, we consider the condition of the cargo to be within an acceptable range. Otherwise, the moisture content of the cargo may be higher. For such cargo, we recommend removing them to prevent them from affecting other cargo.

Furthermore, to protect the interests of the shipowner, we also suggest adding corresponding annotations on the mate's receipt. We will provide specific annotation recommendations after further inspecting the cargo. We hope the above information is helpful. If you have any questions, please feel free to contact me.