Port State Control is the inspection of foreign-flagged ships in a country's ports, verifying that visiting vessels meet the international conventions their flag states have ratified: SOLAS, MARPOL, MLC, STCW and the rest. It exists because flag states police their own fleets unevenly, so port states check arriving tonnage themselves. PSC issues no score and no certificate; it records deficiencies, and serious ones can lead to detention.
Nine regional agreements, the Memoranda of Understanding, coordinate the work so a ship cannot dodge scrutiny by changing ports. The Paris MoU covers Europe and the North Atlantic, the Tokyo MoU the Asia-Pacific, and the United States runs its own programme through the Coast Guard. Each regime pools inspection results in a shared database and uses them to decide which ships to board next.
How it shows up in practice
A bulk carrier arrives in Rotterdam. The Paris MoU database shows her inspection window has closed, which makes her Priority I: the Netherlands must inspect her at this call. A Port State Control officer boards, checks the statutory certificates and walks the ship. If the paperwork is in order and nothing on the walk raises clear grounds, the visit can end within a few hours. A corroded fire main, an out-of-date muster list or hesitant answers from the crew move it to a more detailed inspection, with operational tests and document sampling in the areas of concern. Every finding is recorded as a deficiency with an action code that sets the deadline for the fix, from before departure to the next port. The full sequence, stage by stage, is covered in how a PSC inspection actually runs.
What it means for operators
PSC targets ships by their record. Every inspection result feeds the Ship Risk Profile, which sets how often each ship is boarded and how deep the inspection goes; a detention means more frequent and more searching visits for years, with commercial consequences described in what a detention costs. The record is permanent and shared between port states, so the only lever an operator fully controls is the condition of the ship before arrival. That is the argument for structured pre-inspections with evidence the office can see, which is what Fleetward's PSC readiness workflow is built for.