Vessel Analysis: Ensuring Metal Concentrate Cargo Stability

November 06, 2012
Capsized cargo ship|Fine metal concentrate that can behave like fluid|Cargo ship located at quarry|CSL Innovator self-unloading ship


The Need

The “Code for Safe Practice for Solid Bulk Cargoes” provides rules of safe practice for the shipment of bulk cargos by ship.  One of the rules is to ensure the materials in the holds have sufficient time to settle and are stable before proceeding out of port.  Bulk cargo carriers have been known to list and even sink as a result of unstable cargo – especially in inclement weather.

The metal concentrate producer understood the risks and was aware of the concern.  However the codes give no specific guidelines on how long to wait to ensure a fine, dry concentrate has properly settled and no longer presents a risk of being unstable.  Waiting too long presents costly time lost at the port so there is substantial pressure to depart as quickly as possible.  Therefore a thorough basis for determining a sufficient wait period was required.

The Solution

Jenike & Johanson was commissioned to study the problem and provide a reliable method for setting the wait period.  Our approach was to measure the relevant flow properties of the metal concentrate.  We then used our proprietary SETTLE software to predict how long the vessel must stay in the port before sailing to ensure the cargo is stable.  This required an understanding of hold sizes, filling behavior, and the flow properties of the material.  For their ships and filling approach, we recommended that the vessel remain in port for at least 24 hours after the last hold was filled.

The Result

According to the client, there have been no reports of cargo shifts since adopting Jenike & Johanson’s recommendations.  The project has eliminated the risk and provided an engineered approach for the required wait period before setting sail.

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