Special Survey
The Special Survey (SS), also called the class renewal survey, is the most extensive of the periodic surveys a classification society carries out. It is due every five years and is what renews the ship classification certificate for the next five-year cycle.
A special survey goes far beyond a visual check: it includes close-up examination of the structure, extensive ultrasonic thickness measurements of the steel to assess wastage, tank and space internal examinations, testing of machinery and systems, and overhaul of selected items. It is heavy, is usually combined with a dry-docking, and its scope increases with the age of the ship.
The special survey is the single biggest inspection event in the five-year cycle and the one most likely to uncover expensive steel renewals. Because it is usually done alongside a dry-docking, planning its scope, the thickness-measurement campaign and the likely steel-renewal work is central to controlling both off-hire time and the repair budget.
How often is a special survey carried out?
Every five years, at the end of each classification cycle. Owners may spread the workload through a continuous or rolling survey arrangement, but the full scope must be completed within the five-year window.
What is thickness measurement in a special survey?
Ultrasonic gauging of the steel plating and structure to measure how much thickness has been lost to corrosion. Readings beyond the allowable wastage limits require steel renewal.