Cargo discharge is the process of unloading cargo from a vessel — the reverse of loading, but with its own distinct planning requirements since stability and stress conditions change continuously as weight is removed.
Key Planning Considerations
- Stability throughout discharge — as cargo is removed, GM and the vessel’s overall stability picture changes; a discharge sequence must keep the vessel stable at every intermediate stage, not just the final empty condition
- Structural stress — removing cargo unevenly can create dangerous local stress concentrations, same principle as loading but in reverse
- Trim control — discharge sequence affects trim throughout the operation, with implications for draft and under-keel clearance in port
- Multi-port discharge — for vessels discharging at multiple ports, remaining cargo for later ports must not be disturbed while earlier-port cargo is discharged
Draft Surveys
Draft readings taken before and after discharge (or at intervals during multi-port discharge) allow calculation of the actual cargo weight discharged — a draft survey — used for commercial verification of quantities.
Coordination with Shore Side
Discharge operations require close coordination between the ship’s cargo officer and shore-based terminal operations, particularly regarding sequencing, equipment availability, and any special handling requirements for specific cargo.
Exam Relevance
Discharge planning, stability monitoring during discharge, and draft survey calculations are core Cargo Work topics in deck officer competency exams.