Condition Assessment Scheme (CAS) is a requirement as per Reg 20 of MARPOL Annex I
it is internded to focus on the Category 2 tankers ( Deadweight 20000 and above ) and Category 3 tankers ( DWT between 5000 and 20000 )..
the main prupose was that such kind of tankers are to be phased out during 2005 and 2010.
but i such tankers wish to be operated, they have to be subject to CAS.
if usch tankers pass the CAS survey requirments, they can be operated beyond 2010.
Anyway, such tankers are to be completely disappeared from service beyond 2015, on the time of their Anniverssary Date /or/ the age of 25 years whichever is the earlier.
therefore for the time being, CAS is not valid anymore.