What are objectives of PSC or Port State Control inspection?

The objective of PSC is to detect and discourage owners from operating substandard ships that endanger not only   the  ships  crew  and  the  port,  but also the environment  PSC (Port State Control) inspection helps to minimize the threat to life, properly and the environment by disallowing substandard shipping. 

The fundamental aim of the PSC is to supplement the inspections by the flag state and eliminate    sub–standard ships in order to ensure safer ships and cleaner oceans it includes boarding, inspection, remedial action and possible detention under the applicable conventions.
Port state control can be applied not only to those countries, who are party to the convention but also to the ships that fly the flag of a state that has not rectified a convention.
Thus no ships are exempted from inspection because the principle of no more favorable treatment applies. Any state may also in act its own domestic laws and impose additional nation al rules and regulations on foreign ships entering its water.