Intermediate Survey
An Intermediate Survey (IS) is carried out around the middle of the five-year classification cycle — in practice at or between the second and third annual surveys. Its scope sits between the annual and the special survey, adding items such as selected tank and space examinations and, for older ships, some thickness measurements.
The intermediate survey is where age-related deterioration is caught halfway through the cycle, before it becomes a major problem at the next special survey. For tankers and bulk carriers its scope increases with the age of the ship, reflecting the higher risk of structural wastage.
Five years is a long time for a working hull, and the intermediate survey is the checkpoint that stops corrosion and defects running unchecked to the next special survey. Catching steel wastage or coating breakdown here, rather than later, is far cheaper and avoids nasty surprises in dry dock.
When is the intermediate survey due?
Between the second and third annual survey of the five-year class cycle — effectively at the midpoint — completed within the associated survey window.