Loading iron ore for export presents different demands than other bulk solids. It is not just about moving large volumes in the shortest possible time, but doing so with a particularly abrasive material of high and variable density depending on its granulometry, in operations where every hour a bulk carrier spends berthed carries a direct cost. Choosing the right clamshell grab affects both the equipment's service life and the actual pace of export operations.
Density and Abrasiveness of Iron Ore
Iron ore typically presents densities ranging between 2.5 and 3.5 t/m³ depending on whether it is handled as fines or lumps, and this variation requires shell sizing specific to the material. Stemm already works with models calibrated for densities of 2.8 to 3.2 t/m³ (± 15%) in foundry and ferroalloy applications, and this same technical reference range applies to iron ore handling in port operations.
Beyond density, the real challenge lies in abrasiveness. Iron ore wears down closing lips constantly, which is why the steel used in that contact zone is critical to the grab's service life. Lips in HARDOX 500, in wear-resistant manganese steel, are the standard solution for absorbing this wear without compromising penetration force or the airtight closure of the shells.
Airtight Closure and Fines Loss When Loading Bulk Carriers
During the loading of a bulk carrier, any leakage of material between the shells results in fines loss into the hold or onto the dock, with a twofold cost: economic, since that lost ore is never invoiced on the vessel, and environmental, due to particle dispersion in the port environment. An airtight, uniform closure along the entire length of the shell, sustained by reinforced hydraulic cylinders acting with constant and symmetrical force, minimizes this loss even with fine, low-cohesion materials.
This is especially relevant for iron ore because, unlike other bulk materials such as grain or cement, much of the cargo's commercial value lies in the exact weight loaded, not just its volume. Every ton of fines lost during the operation is a ton that never gets exported.
Loading Cycle and Export Pace
In export operations, a bulk carrier's berthing time is subject to strict contractual deadlines, and any delay in loading generates demurrage penalties. The grab's cycle time, meaning the speed of opening and closing on each pass, directly determines how many tons per hour can be moved and, therefore, whether the planned loading window is met.
Systems like GRAB CONNECT, which allow remote monitoring of pressures, temperatures, and number of cycles performed, make it possible to detect any necessary equipment adjustments before the vessel arrives, avoiding unplanned stoppages during the loading operation itself, when the cost of any downtime multiplies.
Equipment Selection for Export Operations
The right clamshell grab for iron ore combines three elements: sizing adjusted to the material's actual density, a wear-resistant steel closing lip capable of sustaining constant work cycles without losing precision, and an airtight closure system that minimizes fines loss throughout the entire loading operation. These three factors, more than nominal capacity alone, are what determine real performance at an export terminal.
Stemm, manufacturer of electrohydraulic clamshell grabs
At Stemm we design clamshell grabs calibrated for the density and abrasiveness of each mineral, with wear-resistant steel lips and airtight closure systems built for export operations. If you need to size the right equipment for your terminal, check out our online configurator.
