Theoretical / Design Capacity (The Peak)
This is the maximum possible loading rate the machine is engineered for under ideal conditions. Ship loaders are built for specific commodities and vessel sizes.
Bulk Carriers (Coal, Iron Ore, Grain): Common capacities range from 1,000 t/h to over 10,000 t/h.
A mid-sized loader for coal might be 2,500 t/h.
Large-scale, modern loaders at major iron ore ports (e.g., in Australia or Brazil) can exceed 12,000 t/h.
Container Cranes (STS - Ship-to-Shore): Capacity is measured in moves per hour (crane cycles). Modern mega-cranes can achieve 30-50+ moves per hour under peak conditions.
Operational / Effective Capacity (The Reality)
This is the average sustained rate achieved during a full loading cycle. It is always lower than the theoretical peak due to the inevitable non-loading time. A realistic effective capacity is often 70-85% of the design capacity.
Key reasons for the difference:
Vessel Holds: Time spent shifting the loader boom between holds, adjusting spout height, and trimming cargo.
Ship Movement: Adjustments due to tidal changes or the ship settling in the water.
Sequence & Stability: Loading must follow a precise sequence to maintain the ship's stability and stress limits.
Feeding System Delays: Interruptions in the conveyor system supplying the loader (e.g., shifts between stockpiles).
Safety & Checks: Regular inspections, sample taking, and crew breaks.
