A PSC detention is an order from a Port State Control authority that a ship may not sail until serious deficiencies are rectified. It is the strongest intervention PSC has short of a regional ban. The record it creates is permanent, visible to charterers and vetting departments, and raises the ship's inspection exposure for years afterwards.
Detention is not a fine or a court judgement. It is an operational decision by the inspecting officer that the ship, in her current state, should not go to sea, taken when at least one deficiency is serious enough to be marked as grounds for detention.
How it shows up in practice
A tanker is boarded for a routine inspection. The officer tests the emergency fire pump and it will not build pressure; questioning shows the crew has not run it in months, which points at the safety management system rather than one pump. The deficiency is marked detainable, the master is formally notified, and the flag state and classification society are informed. The ship stays alongside, or at anchor, while repairs are arranged. Under Paris MoU procedure the officer returns on board to verify the rectification before releasing her; where repairs cannot be done locally, the authority can allow a single voyage to a repair yard under conditions. A typical detention of this kind holds the ship for two to three days. The direct costs, the off-hire clause that usually stops hire for the whole period, and the escalation that follows are broken down in what a PSC detention actually costs.
What it means for operators
The port stay is the cheap part. A detention feeds the Ship Risk Profile, so the ship is inspected more often and more deeply from then on, and repeated detentions within the counting window put the ship on the path to a Paris MoU refusal of access order. Charterers read detention records in the public databases when they screen tonnage. Nothing removes a detention from the record afterwards, which is why the working assumption should be prevention: find the failed pump in the pre-inspection, not the boarding. When a detention does happen, disciplined evidence and follow-up matter, and how to close out deficiencies properly covers that side. Fleetward's PSC solution exists to make the prevention half systematic.