Air compressor is an important equipment for ships. The capacity and quantity of the air compressor must match the capacity of the relevant air reservoir and the gas consumption of the main engine and auxiliary engine, and meet the requirement of the inflation time and the start-ups of the main engine and the auxiliary engine, thus to be approved by the classification societies. The rational selection of the capacity and quantity of the air compressor can greatly save the procurement cost and the energy cost by reducing the frequent start-ups of the air compressor. It analyzes the advantages and disadvantages, optimization and redundancy of the selection of the air compressor for several container ships. It can provide reference for the ship design in future.

In order to meet the latest sulphur limit requirements of the international maritime organization(IMO), the retrofitting of the exhaust gas cleaning system for a very large crude carrier(VLCC) are examined based on the original system and its characteristics, such as the equipment selection, power load analysis, pipeline system design and general arrangement. The sea trial results show that this retrofitting plan can meet the code requirements and the operation requirements of shipowers.